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Python Programming for Arduino - Pratik Desai2015-05

1. gen t s e t o ff o lt 02 02 0 b 0b 0o0 o e usas TX MH i rss Arduino PODER heh gang eee oheee eee o C8888 o ele ee eee Ce eee EEE Note To find out more about transistor terminals collector emitter and base and to associate transistor pins with their respective terminals you can refer to their datasheets or the following websites e http en wikipedia org wiki Transistor e http www onsemi com pub Collateral TIP120 D PDF e http www mouser com ds 2 68 PN2221 2222A 11964 pdf The Python code The Python recipe with the name dcMotorPwM py for a DC motor is located in the code bundle of this book which can be downloaded from https www packtpub com books content support 1961 Open the Python file to further understand the usage of PWM to control the speed of the DC motor The custom function dcMotorControl takes motor speed and time duration as input parameters as described in the following code snippet def dcMotorControl r deltaT pwmPin write r 100 00 sleep deltaT pwmPin write 0 Just like the previous examples we are using a similar code to import the necessary library and initialize the Arduino board After initialization we are assigning the mode of the digital pin 3 as PwM which can be seen from the utilization of the get_pin d 3 p method This code reflects the indirect m
2. 5 localhost 8080 Manually sending data to Xively channel Channel Leo Value 1 submit Python downloading data from Xively The process of downloading data from Xively includes requesting the Current Value parameter for the specified channel In the next exercise we will develop a reference code that will be used in the next downloading exercise In that exercise we will develop an advanced web application to retrieve data from a specific Xively channel As we are using functions based on the REST protocol to communicate with Xively Xively will not simply notify you about any new available update instead you will have to request it At this point it is important to note that we will have to periodically request data from Xively However Xively provides an alternative method called triggers to overcome this problem which is explained later in this section The basic method for retrieving data from Xively Just like the uploading exercises the downloading exercises also require a similar code to instantiate the XivelyAPIClient and api feeds get methods As we are retrieving the data instead of sending it we will only use the feed datastreams get method and avoid the feed datastreams create method The download process requires the channel to be already present and this is the main reason why we only have to use the get method try datastream feed datastreams get Random except HTTPError a
3. Once you have instantiated the rendering folder it is time to create template files for your program According to the requirements of your program you can create as many template files as you want A language called Templetor is used to create these template files in web py You can learn more about it at http webpy org templetor Each template file created using Templetor needs to be stored in the HTML format with the htm1 extension Let s create a file called test html in the templates folder using a text editor and paste the following code snippet in to the file def with form i lt form method POST gt form render lt form gt lt p gt Value is i lt p gt As you can see in the preceding code snippet the template file begins with the def with expression where you need to specify the input arguments as variables within the brackets Once the template is rendered these will be the only variables you can utilize for the web page for example in the previous code snippet we passed two variables form and i as input variables We utilized the form object using form render to render it inside the web page When you need to render the form object you can directly pass the other variable by simply declaring it that is i Templetor will render the HTML code of the template file as it is while utilizing the variables in the instances where they are being used Now you have a template file test htm1
4. C 3 localhost 8080 Hello world To understand how this simple code works check out the GET method in the previous code snippet As you can see when the web browser requests the URL the GET method returns the Hello world string to the browser Meanwhile you can also observe two other mandatory web py components in your code the urls and web application methods The web py library requires initialization of the response location in the declaration of the urls variable Every web py based web application requires the application urls global method to be called to initialize the web server By default the web py applications run on port number 8080 which can be changed to another port number by specifying it during execution For example if you want to run your web py application on port 8888 execute the following command python webPyBasicExample py 8888 Although this only returns simple text you have now successfully created your first web application using Python We will take it forward from here and create more complex web applications in the upcoming chapters using the web py library To develop these complex applications we will require more than just the GET method Let s start exploring advance concepts to further enhance your familiarity with the web py library Essential web py concepts for developing complex web applications The web py library has been designed to provide convenient and simple
5. e The user should be able to turn the individual power ports on and off using customized tweets e The user should be able to check the status of the power ports using Twitter Project requirements Here are the initial project requirements derived from the goals e The system should have 110V or 220V AC power ports interfaced with relays e An Arduino based unit should be able to control these relays ultimately controlling the appliance connected through the power ports e The system should be able to decode the tweets sent by the user and convert them into appropriate control messages for Arduino e The Python based program that processes the tweets should then publish these messages so that Arduino can complete those actions using the relays e To sum up the relays should be controlled in a near real time manner using the tweets sent by the user e The system should also understand keywords to check the status of the relays and automatically tweet the status The system should process a tweet only once and should be able to remember the last tweet processed Note 110V versus 220V AC power Depending on the country your AC power supply may have voltage ratings of 110 120V or 220 240V Although the circuit diagram used by this project mentions a 110V AC power supply the same circuit should also work for a 220V power supply If you are using a 220V supply check out the following notes before moving forward o Ensure that the a
6. 10 make Open the boot configuration files sudo pico boot config txt In the config txt file locate and uncomment the following lines of code framebuffer_width 320 framebuffer_height 240 Save and exit the file Now every time the Raspberry Pi restarts we need to execute a command to start the TFT LCD screen To do this open the rc 1local file using the following command sudo pico etc rc local Add the following line of code to the file that starts the screen sudo home pi mztx ext 2 4 src mztx06a amp Save and exit the file Then reboot the Raspberry Pi using the following command sudo reboot You can remove your HDMI monitor now and start working with your TFT LCD screen One thing that you will have to keep in mind is that the screen resolution is very small and it is not optimized for coding We prefer to use the HDMI monitor to perform the major code modifications that are required in the next section The utilization of the TFT LCD screen in this project is to accommodate the mobility and portability requirements of the thermostat Optimizing the GUI for the TFT LCD screen The resolution of the TFT LCD screen that we configured in the previous section is only 320 x 240 pixels but the windows that we created in first programming stage are quite large Therefore before we copy and run our Python code on the Raspberry Pi we need to adjust a few parameters in the code In your regular com
7. Root device type ebs Virtualization type hvm 3 In next window you will be prompted with a list of options that have different configurations of computational capacity From the General purpose family select the t2 micro type which is eligible for the free tier The computational capabilities provided by the t2 micro tier are sufficient for the exercises that we are going to perform in the book and for most of the DIY projects Make sure that you do not select any other tier unless you are confident of your selection Family Type CPUs 1 Memory Instance Storage EBS rr Network GiB GB i Available i Performance w General purpose MM 1 1 EBS only Low to Moderate General purpose t2 small 1 2 EBS only Low to Moderate General purpose t2 medium 2 4 EBS only Low to Moderate General purpose m3 medium 1 3 75 1 x 4 SSD Moderate General purpose m3 large 2 7 5 1 x 32 SSD Moderate 4 Once you have selected the specified tier click on the Review and Launch button to review the final configuration of the instance 5 Review the configuration and make sure that you have selected the appropriate options as mentioned earlier You can now click on the Launch button to proceed further 6 This will open a pop up window that will prompt you to create a new key pair that will be used for authentication in the upcoming steps 10 Select an existing key pair or create a new key pair x A key pair consists of a public k
8. Your own cloud platform for the IoT In the previous section we worked with a commercial loT platform that also provides restricted free access to basic functionalities We also learned various ways to communicate with Xively that is based on the REST protocol For any small projects or prototypes Xively and other similar IoT platforms provide a sufficient solution and are therefore recommended by us However the limited free service provided by Xively may not satisfy all of your requirements to develop a full stack loT product The following are a few cases where you may want to configure or develop your own IoT platform e Develop your own commercial IoT platform e Develop custom features that are exclusive to your product e Add more control features and communication protocols while also securing your data e Require an inexpensive solution for large scale projects This section will guide you through the step by step process of creating an elementary small level IoT cloud platform The goal of the section is to make you familiar with the requirements and the process of creating an IoT platform To develop a large scale diverse and feature rich platform such as Xively you will need a significant amount of knowledge and experience in the domains of cloud and distributed computing Unfortunately cloud and distributed computing are out of scope of this book and we will stick with the implementation of the basic features To develop a cl
9. id datastream current_value 1337 Improving UX When we designed the user experience for this project our goal was to demonstrate the usefulness of a UX design in developing the software flow In the current UX design the control center and the web application have limited control and features for a user The following are a few changes that you need to implement to improve the UX of the project e Add tooltips and proper naming conventions for the various descriptions Implement a proper layout to differentiate between the various information categories e Add buttons for the buzzer and the LED control on the control center GUI e In the web application use a JavaScript and Ajax based interface to automatically refresh the changes in sensor values e Provide a UI mechanism so that the user can change the update interval at the control center and the web application Once these changes are made propagate them through each program so that the monitoring station can start publishing messages at the new interval Expanding cloud based features In the current setup we are using two stages to provide cloud based capabilities and enable remote monitoring We have Xively as a data relay and Amazon AWS to host the web application If you are working on a commercial grade product and want to reduce the complexity of the architecture you can implement the following changes e You can develop your own data relay on your cloud i
10. Arduino board The list of components USB cable The list of components o computer The list of components e motion triggered LEDs using Arduino sketch o developing Method 1 using a standalone Arduino sketch project setup The project setup coding The Arduino sketch setup function using The setup function loop function using The loop function custom Arduino functions using Working with custom Arduino functions testing Testing o troubleshooting Troubleshooting e motion triggered LEDs using Python and Firmata o developing Method 2 using Python and Firmata project setup The project setup Python executable files using Working with Python executable files coding The Python code pyFirmata methods using Working with pyFirmata methods Python functions using Working with Python functions testing Testing o troubleshooting Troubleshooting e MQTT o about MQTT A lightweight messaging protocol o URL Introduction to MQTT o Mosquitto Mosquitto an open source MQTT broker e MQTT on Arduino o PubSubClient library using MQTT on Arduino using the PubSubClient library o Arduino MQTT client developing Developing the Arduino MQTT client e MQTT on Python o paho matt library using MQTT on Python using paho matt Using the paho matt Python library e MQTT Gateway o developing for Arduino Exercise 4 MQTT Gateway for Arduino Arduino developing as MQTT client
11. Developing Arduino as the MQTT client developing Mosquitto used Developing the MQTT Gateway using Mosquitto extending web py used Extending the MQTT Gateway using web py testing Testing your Mosquitto Gateway O O O O 0 0 O O O 0 Oo O O O 0 0 0 O O 0 O N e Nest Thermostat o URL Thermostat the project description e networking o O O O O 0 O 0 o fundamentals Networking fundamentals local area network LAN Networking fundamentals home area network HAN Networking fundamentals wide area network WAN Networking fundamentals protocols Networking fundamentals media access control MAC address Networking fundamentals Internet Protocol IP Networking fundamentals IP address Networking fundamentals localhost IP address Networking fundamentals e networking extensions for Arduino o o o o about Networking extensions for Arduino Arduino Ethernet Shield Arduino Ethernet Shield Arduino WiFi Shield Arduino WiFi Shield Arduino Y n Arduino Y n e newline character o o about Playing with a pySerial example URL Playing with a pySerial example e New Out Of Box Software NOOBS o about Preparing an SD card e NumPy package o URL Configuring matplotlib on Windows O e open method o used for manipulating files The open method o modes The open method e Operators o about Python operators and built in types Operator
12. Livery Place 35 Livery Street Birmingham B3 2PB UK ISBN 978 1 78328 593 8 www packtpub com Credits Author Pratik Desai Reviewers Juan Ram n Gonz lez Marco Schwartz Josh VanderLinden Commissioning Editor Saleem Ahmed Acquisition Editor James Jones Content Development Editor Priyanka Shah Technical Editor Ankita Thakur Copy Editors Jasmine Nadar Vikrant Phadke Project Coordinator Milton Dsouza Proofreaders Safis Editing Maria Gould Ameesha Green Paul Hindle Indexer Mariammal Chettiyar Graphics Abhinash Sahu Production Coordinator Manu Joseph Cover Work Manu Joseph About the Author Pratik Desai PhD is the Principal Scientist and cofounder of a connected devices start up Imbue Labs where he develops scalable and interoperable architecture for wearable devices and Internet of Things IoT platforms during the day At night he leads the development of an open source IoT initiative the Semantic Repository of Things Pratik has 8 years of research and design experience in various layers of the loT and its predecessor technologies such as wireless sensor networks RFID and machine to machine M2M communication His domains of expertise are the loT Semantic Web machine learning robotics and artificial intelligence Pratik completed his MS and PhD from Wright State University Ohio and collaborated with the Ohio Center of Excellence in Knowledge enabled Computing Kno e sis during
13. Now connect your Arduino Uno to a computer using a USB cable You will also need to connect Arduino to your local home network using an Ethernet cable To do that use a straight CAT5 or CAT6 cable and connect one end of the cable to your home router This router should be the same device that provides network access to the computer you are using Connect the other end of the Ethernet cable to the Ethernet port of the Arduino Ethernet Shield board If the physical level connection has been established correctly you should see a green light on the port WiFi Ethernet Now it s time to start coding your first Ethernet example Open the WebServer example by navigating to File Examples Ethernet WebServer in your Arduino IDE As you can see the Ethernet library is included with the other required libraries and the supported code In the code you will need to change the MAC and IP addresses to make it work for your configuration While you can obtain the MAC address of the Ethernet Shield from the back of the board you will have to select an IP address according to your home network configuration As you have already obtained the IP address of the computer you are working with select another address in the range Ensure that no other network node is using this IP address Use these MAC and IP addresses to update the following values in your code You will need to repeat these steps for every exercise when you are dealing with Ard
14. Prototyping Just for a moment let s step back and look at the project that we built in the previous chapter The project had a very simple goal and we were able to develop it quite comfortably However the project is certainly not ready to be a consumer product since it doesn t have significant functionalities and most importantly it is not a robust product that can be repeatedly produced as it is What you can tell about your current project is that it is a DIY project for personal use or just a model that can be developed further to be a great product Now if you are looking to develop a commercial product or just a DIY project that is really robust and scalable you must consider starting it by making a model first At this stage you need to envision the product with the required features that need to be developed and the number of components that are required to deploy these features Prototyping is basically a rapid way to create a working model of your envisioned idea before developing it into a fully functional project or product The proof of concept prototype that is developed during this prototyping process lets you to identify the feasibility of your idea and in some cases it helps you to explore the potential of your project The prototyping or functional model making process is essential for any industry and not just for electronics In the electronics domain prototyping can be used at the very first stage of interfacing compon
15. Python Programming for Arduino Develop practical Internet of Things prototypes and applications with Arduino and Python PACKT 2 Python Programming for Arduino Table of Contents Python Programming for Arduino Credits About the Author About the Reviewers www PacktPub com Support files eBooks discount offers and more Why subscribe Free access for Packt account holders Preface What this book covers What you need for this book Who this book is for Conventions Reader feedback Customer support Downloading the example code Downloading the color images of this book Errata Piracy Questions 1 Getting Started with Python and Arduino Introduction to Python Why we use Python When do we use other languages Installing Python and Setuptools Installing Python Linux Ubuntu Fedora and Red Hat Installing Setuptools The if statement The for statement The while statement Built in functions Conversions Math operations Arduino variants The Arduino Uno board Installing the Arduino IDE Variables Constants Linux Windows What is Firmata Uploading a Firmata sketch to the Arduino board The project setup The Arduino sketch The setup function Connections The Python code Connections The Arduino sketch for the thermostat Interfacing the temperature sensor Windows Mac OS X Networking extensions for Arduin
16. The Tk widget initializes a main empty window with a title bar This is a root widget and it is required by each program only once The main window gets its decoration and styles from the operating system s environment Therefore when you run the same Tkinter code on different operating systems you will get the same window and title bar but in a different style Once you create a root widget you can perform some top level methods to decorate describe or resize this window In code we are using the title method to set the title of the main window This title method takes a string as an input argument Top Tkinter Tk top title Hello GUI Next we call the minsize method on the main window to set the minimum size of the window with the argument width height top minsize 200 30 Similarly you can also use the maxsize method to specify the maximum size that the main window should have In the minsize and maxsize methods the values of width and height are provided in the number of pixels Once the entire program has been instantiated the mainloop function is required to start the event loop top mainloop You won t be able to see any other widgets including the main window if the code does not enter in the main event loop The event loop will be alive until the window is manually closed or the quit method is called You might have various questions about updating the window programmatically closing
17. if client connect MonitoringStation client subscribe MonitoringStation led client subscribe MonitoringStation buzzer Programming an interrupt to handle the press of a button We have taken care of the publishing and subscribing functions of the monitoring station Now we will need to integrate the button switch that is controlled by inputs from the user In the Arduino programming routines we run a periodic loop to check the status of the pins However this may not be useful if the button is pressed since it requires immediate action This action of pressing the button is handled using the Arduino interrupts as shown in the following line of code attachInterrupt buttonPress RISING The preceding line of code associates an interrupt at pin O digital pin 2 with the buttonPress function This function sets off the buzzers whenever the state of the interrupt is changed In other words when the button is pressed by the user the buzzer will be instantaneously turned off irrespective of the current status of the buzzer void buttonPress digitalwrite BUZZER LOW Serial printin Set buzzer off Testing The current Arduino code communicates with the control center for publishing and subscribing the data but we haven t yet set up the Mosquitto broker to handle these requests You can still go ahead and upload the Arduino sketch to your monitoring station using the USB cable This will not result in any frui
18. 8 lt lt eevee eeeee so vr eee eevee o o eevee s T fritzin If you want to use any other digital pin make sure that you change the pin number in the Python program in the next section Once you have made the appropriate connections let s move on to the Python program The Python code The Python file consisting of this code is named servoCustomAngle py and is located in the code bundle of this book which can be downloaded from https www packtpub com books content support 19610 Open this file in your Python editor Like other examples the starting section of the program contains the code to import the libraries and set up the Arduino board from pyfirmata import Arduino SERVO from time import sleep Setting up the Arduino board port COM5 board Arduino port Need to give some time to pyFirmata and Arduino to synchronize sleep 5 Now that you have Python ready to communicate with the Arduino board let s configure the digital pin that is going to be used to connect the servomotor to the Arduino board We will complete this task by setting the mode of pin 13 to SERVO Set mode of the pin 13 as SERVO pin 13 board digital pin mode SERVO The setServoAngle pin angle custom function takes the pins on which the servomotor is connected and the custom angle as input parameters This function can be used as a part of various large projects that involve servos Cust
19. If allthe steps are performed as described on execution you will be able to see the temperature reading in Celsius and Fahrenheit in the Serial Monitor window include lt Wire h gt int partAddress 0x48 void setup Serial begin 9600 Wire begin void loop Wire requestFrom partAddress 2 Wire read Wire read byte MSB byte LSB int TemperatureData MSB lt lt 8 LSB gt gt 4 float celsius TemperatureData 0 0625 Serial print Celsius Serial println celsius float fahrenheit 1 8 celsius 32 Serial print Fahrenheit Serial printin fahrenheit delay 500 In the preceding code snippet the Wire requestFrom partAddress 2 function requests two bytes from the slave TMP102 The slave sends data bytes to the master which get captured by the Wire read function and are stored as two different bits most significant bit MSB and least significant bit LSB These bytes are converted into an integer value which is then converted into the actual Celsius reading by multiplying the incremental fraction of the TMP102 sensor that is obtained from the datasheet TMP102 is one of the easiest I2C sensors to interface with Arduino as the sensor values can be obtained via a simple I2C request method Arduino coding for the BH1750 light sensor BH1750 is a digital light sensor that measures the amount of visible light in a given area Although various DIY projects utilize si
20. PowerStrip fan off Similarly when the code receives an update from the PowerStrip statusreport topic it obtains the status from the message payload and posts it as a new tweet to the user timeline of that Twitter account This completes the UX flow for the status check using Twitter def onMessage mosq obj msg if msg topic PowerStrip statusreport print msg payload api PostUpdate msg payload Testing and troubleshooting Testing can simply be performed by posting the fan on status to the Twitter account used in this project You should be able to see the fan turning on by using the command shown here Tweet a PowerStrip Tweet_a Strip 4h Fan on September 17 Similarly send the fan off status to turn off the fan You may find some lagging as the loop used to retrieve the tweets is set with a delay of a minute Tweet a PowerStrip Tweet_a_ Strip 4h Fan off September 17 To access the status of the system post the status get status to the account and you will be able to see the system status automatically posted by the computation unit Tweet a PowerStrip Tweet_a Strip now status get The tweet shown in the following screenshot is generated using the Tweet a PowerStrip unit It displays the status of all the connected appliances Tweet a PowerStrip t Fan on Lamp off Toaster off Coffeemaker off While working with the system you will want to either avoid
21. TFT LCD connection using GPIO Connecting the TFT LCD using GPIO TFT LCD configuring Configuring the TFT LCD with the Raspberry Pi OS GUI optimizing for TFT LCD screen Optimizing the GUI for the TFT LCD screen troubleshooting Troubleshooting thin film transistor liquid crystal display TFT LCD o about Hardware design ThingSpeak o about ThingSpeak Tk O widget o about Learning Tkinter for GUI design The root widget Tk and the top level methods Tkinter o o o o about Learning Tkinter for GUI design Pack geometry manager The Pack geometry manager Grid geometry manager The Grid geometry manager plots integrating Integrating plots in the Tkinter window Tkinter widgets Tk Learning Tkinter for GUI design Label Learning Tkinter for GUI design Button Learning Tkinter for GUI design Entry Learning Tkinter for GUI design Scale Learning Tkinter for GUI design o Checkbox Learning Tkinter for GUI design e Tkinter class o about The Label widget monitoring I O pins o BooleanVar method The Label widget monitoring I O pins o update_idletasks method The Label widget monitoring I O pins o update method The Label widget monitoring I O pins e TMP102 temperature sensor o interfacing Arduino used Arduino coding for the TMP102 temperature sensor o interfacing PyMata library used Interfacing TMP102 using PyMata e transistor terminal
22. We have selected web py as the preferred web framework due to its simple yet powerful functionalities The web py library was initially developed by the late Aaron Swartz with the goal of developing an easy and straightforward approach to create web applications using Python This library provides two main methods GET and POST to support the HTTP Representation State Transfer REST architecture This architecture is designed to support the HT TP protocol by sending and receiving data between clients and the server Today the REST architecture is implemented by a huge number of websites to transfer data over HTTP Installing web py To get started with web py you need to install the web py library using Setuptools We installed Setuptools for various operating systems in Chapter 1 Getting Started with Python and Arduino On Linux and Mac OS X execute either of these commands on the terminal to install web py sudo easy_install web py sudo pip install web py On Windows open the Command Prompt and execute the following command gt easy_install exe web py If Setuptools is set up correctly you should be able to install the library without any difficulty To verify the installation of the library open the Python interactive prompt and run this command to see whether you have imported the library without any errors gt gt gt import web Your first Python web application Implementing a web server using web py is a very s
23. What do you need to begin using the Raspberry Pi mouse What do you need to begin using the Raspberry Pi keyboard What do you need to begin using the Raspberry Pi o USB hub optional What do you need to begin using the Raspberry Pi hardware components remote home monitoring system o about The list of required components hardware components Tweet a PowerStrip o about Required hardware components o relays Relays o PowerSwitch Tail PowerSwitch Tail hardware design IoT o about Hardware design The loT cloud platforms hardware design Tweet a PowerStrip o about Hardware design hardware system design motion triggered LEDs o Fritzing using Introducing Fritzing a hardware prototyping software o breadboard using Working with the breadboard o hardware prototype designing Designing the hardware prototype help function o about Plotting random numbers using matplotlib HIH 4030 humidity sensor o using The list of required components home area network HAN o about Networking fundamentals Homebrew o URL Mac OS X o installing Mac OS X O O O O 0 I2C protocol o reference link Prototyping with the 12C protocol if statement o about The if statement input output 1 0 pins o about Arduino variants installation Arduino IDE o on Linux Linux o on Mac OS X Mac OS X o on Windows Windows installation paho matt library Installing paho matt installation pip
24. as displayed in the diagram We recommend that you use red and black wires to represent the 5V and ground lines respectively 5 The push button provides the output as HIGH or LOW state and interfaced using digital pins As displayed in the circuit connect these push buttons to digital pins 2 and 3 using two 1 kilo ohm resistors 6 Complete the remaining connections as displayed in the following diagram Make sure that you have firmly connected all the wires before powering up the Arduino board HIH 4030 TX ME A AXE Arduino Note Make sure that you always disconnect your Arduino board from the power source or a USB port before making any connections This will prevent any damage to the board due to short circuiting Complete all the connections for the thermostat sensor unit before heading to the next section As this unit is being used in both the programming stages you won t be performing any further changes to the thermostat sensor unit Software flow for user experience design One of the critical components of any project is its usability or accessibility When you are working on making your project prototype into a product it is necessary to have an intuitive and resourceful user interface so that the user can easily interact with your product Hence it is necessary to define the user experience and software flow of a project before you start coding The software flow includes the flow chart and the logic
25. first attach the Ethernet Shield on top of the Arduino board Connect the sensors and actuators to the appropriate pins as displayed in the following figure Once you have the hardware assembled you can connect the Ethernet Shield to your home router using the Ethernet cable You will need to power the board using the USB cable to upload the Arduino code from your computer In case you want to deploy the Arduino board to a remote location you will need an external 5V supply to power Arduino PIR motion sensor Arduino Ethernet Shield 3 ron imo ma a y a hd DIGITAL PuNer Eos ken UNO i pi aa ON gt rx Arduino HIH 4030 The IoT cloud platforms The term IoT cloud platform is used for the cloud platforms that provide very specific services protocol support and web based tools for IoT applications In more informal terms these cloud IoT platforms can be used to upload your sensor data and access them from anywhere using the Internet With these basic features they also provide tools to access visualize and process your sensor data on various platforms such as computers and smartphones Examples of similar IoT cloud platforms include Xively http www xively com 2lemetry http www 2lemetry com Carriots http www carriots com ThingSpeak http thingspeak com and so on The following figure shows the architecture of an loT system with an Arduino based sensor system that is sen
26. found at http arduino cc en Main ArduinoWi FiShield Arduino Y n Unlike the Ethernet Shield and the WiFi Shield the Arduino Y n is a standalone variant of the Arduino board It includes both Ethernet and Wi Fi based network connectivity in addition to the basic Arduino component the microcontroller Yun is equipped with the latest and more powerful processing units compared to Uno Instead of the traditional way of using Arduino code Y n supports a lightweight version of the Linux operating system providing functionality similar to a single board computer such as the Raspberry Pi You can use your Arduino IDE to program Y n even while running Unix shell scripts _ mama Source http arduino cc en uploads Main Arduino YunFront_2 jpg You can find more information about Yun at the Arduino official website at http arduino cc en Main ArduinoBoard Yun Arduino Ethernet library The Arduino Ethernet library provides support for the Ethernet protocol and hence provides support for Ethernet extensions of Arduino such as the Ethernet Shield This is a standard Arduino library and it gets deployed with the Arduino IDE The library is designed to accept incoming connection requests when deployed as a server and while making outgoing connections to other servers when being utilized as a client The library concurrently supports up to four connections due to the limited computation capability of
27. from pyfirmata import Arduino from pyfirmata import INPUT OUTPUT PWM Setting up Arduino board port dev cu usbmodemfa1331 board Arduino port Assigning modes to digital pins board digital 13 mode OUTPUT board analog 0 mode INPUT The pyFirmata library includes classes for the INPUT and OUTPUT modes which are required to be imported before you utilized them The preceding example shows the delegation of digital pin 13 as an output and the analog pin 0 as an input The mode method is performed on the variable assigned to the configured Arduino board using the digital and analog array index assignment The pyFirmata library also supports additional modes such as PwM and SERVO The PwM mode is used to get analog results from digital pins while the SERVO mode helps a digital pin to set the angle of the shaft between 0 to 180 degrees The PwM and SERVO modes are explained with detailed examples later in this chapter If you are using any of these modes import their appropriate classes from the pyFirmata library Once these classes are imported from the pyFirmata package the modes for the appropriate pins can be assigned using the following lines of code board digital 3 mode PWM board digital 10 mode SERVO Note In electronics PWM is a signal modulation technique that is greatly used to provide controlled amount of power to components While dealing with digital signals the PWM technique is used to obtain anal
28. give you control over your hardware Chapter 11 Tweet a PowerStrip Smart power management units or strips are part of some of the most popular IoT subdomains smart homes and smart grids Nowadays smart power strips are commercially available and provide a large number of features such as remote access smart power usage and power management In this project we are going to create a smart DIY power strip that can be controlled remotely using status messages posted on Twitter the popular social media website http www twitter com These messages are also known as tweets Basically just like you can control sensors remotely using a web browser you can control them by sending a tweet We ve already worked with low power sensors in the previous project so let s work with AC appliances in this project We will be implementing the same project development methods that we utilized in the previous project This chapter avoids additional explanations about the process and sticks only to the details associated with the project Project overview This project requires the development of a smart power strip using Arduino and Python while the control inputs to the strips are tweets Although we are only enabling remote access to the power strip there are a large number of additional features that can be implemented in future to elevate this DIY project to a commercial product The major goals we want to achieve in this project are as follows
29. gt s1 2 He gt gt gt s1 s2 5 Hello Note Similar to the primary prompt with default notation gt gt gt the Python interactive interpreter also has a secondary prompt that uses three dots when it is being used from the terminal You won t be able to see the three dots in IDLE when you use the secondary prompt The secondary prompt is used for a multiline construct which requires continuous lines Execute the following commands by manually typing them in the interpreter and do not forget to indent the next line after the if statement with a tab gt gt gt age 14 gt gt gt if age gt 10 or age lt 20 print teen teen Data structures Python supports four main data structures list tuple set and dictionary and there are a number of important built in methods around these data structures Lists Lists are used to group together values of single or multiple data types The list structure can be assigned by stating values in square brackets with a comma as a separator gt gt gt myList a 2 b 12 0 5 2 gt gt gt myList a 2 b 12 0 5 2 Like strings values in a list can be accessed using index numbers which starts from 0 A feature called slicing is used by Python to obtain a specific subset or element of the data structure using the colon operator In a standard format slicing can be specified using the myList start end increment notation Here are a few exam
30. o reference link What do you need to begin using the Raspberry Pi Preparing an SD card o preparing Preparing an SD card o preparing from Windows Preparing an SD card preparing from Mac OS X Preparing an SD card o preparing from Ubuntu Linux Preparing an SD card Secure Shell SSH protocol Logging into your virtual instance Serial Clock Line SCL o about Prototyping with the I2C protocol Serial Data Line SDA o about Prototyping with the I2C protocol serial monitor o using Using the Serial Monitor window serial peripheral interface SPI o about Prototyping Server class o about The Server class servomotors o using Servomotor moving the motor to a certain angle o connections Connections o Python code The Python code setup function o using The setup function Setuptools o installing Installing Setuptools o about Installing Setuptools o installing on Linux Linux o installing on Windows Windows o installing on Mac OS X Mac OS X sketch o about What is an Arduino sketch o compiling Compiling and uploading sketches o uploading Compiling and uploading sketches sketchbook o about What is an Arduino sketch slicing o about Lists StandardFirmata firmware o using Prototyping statements o about Functions and statements Statements subnetwork subnet o about Exercise 1 a web server your first Arduino network program o reference li
31. ready to be used in your web py program Whenever a GET or POST function is executed you are required to return a value to the requesting client Although you can return any variable for these requests including None you will have to render a template file where the response is associated with loading a web page You can return the template file using the render function followed by the filename of the template file and input arguments return render test f i As you can see in the preceding line of code we are returning the rendered test html page by specifying the render test function where test is just the filename without the html extension The function also includes a form object f and variable i that will be passed as input arguments Forms The web py library provides simple ways of creating form elements using the Form module This module includes the capability to create HTML form elements obtain inputs from users and validate these inputs before utilizing them in the Python program In the following code snippet we are creating two form elements Textbox and Button using the Form library submit_form form Form form Textbox Celsius description Celsius form Button submit type submit description submit Besides Textbox which obtains text input from users and Button which submits the form the Form module also provides a few other form elements such as Password to obtain hi
32. when we start using multiple programs to control Arduino in the next section Assuming that you can now select the serial port in the Arduino IDE we can go ahead with compiling and uploading sketches to your Arduino board The Arduino IDE ships with preinstalled example sketches with which you can play around However before we go ahead and start playing with complex examples let s go through the next section which explains the Firmata protocol and also guides you through step by step instructions to compile and upload a sketch Introducing the Firmata protocol Before Arduino the domain of microcontroller based applications was limited to hardware programmers Arduino made it simple for developers that came from other software fields and even for the non coding community to develop microcontroller based hardware applications Arduino consists of a simple hardware design with a microcontroller and VO pins to interface external devices If one can write an Arduino sketch that can transfer the control of the microcontroller and these pins to an external software mechanism then it will reduce one s efforts to upload Arduino sketches for every modification This process can be performed by developing such an Arduino program that can then be controlled using a serial port There exists a protocol called Firmata which does exactly that What is Firmata Firmata is a generic protocol that allows communication between the microcontroller and
33. working with Working with pyFirmata methods used for setting up Arduino board Setting up the Arduino board used for configuring Arduino pins Configuring Arduino pins used for working with Arduino pins Working with pins servo_config pin min_pulse 544 max_pulse 2400 angle 0 Additional functions pass_time seconds Additional functions get_firmata_version Additional functions exit Additional functions pulseIn pulseOut Upcoming functions shiftIn shiftOut Upcoming functions URL Why we use Python Installing Python packages about Why we use Python e pyplot framework o about Plotting random numbers using matplotlib o figure function Plotting random numbers using matplotlib o show method Plotting random numbers using matplotlib e pySerial commands o using Useful pySerial commands o used for connecting with serial port Connecting with the serial port o used for reading a line from port Reading a line from the port o used for flushing port to avoid buffer overflow Flushing the port to avoid buffer overflow o used for closing port Closing the port e pySerial library o about Getting started with pySerial o installing Installing pySerial o URL Installing pySerial o example Playing with a pySerial example o and Firmata bridging Bridging pySerial and Firmata e Python o about Introduction to Python benefits Why we use Python usage considerations When do we use other languag
34. you will be able to see a window similar to the one displayed in the following screenshot Click on the Start button and wave in front of the motion sensor If the sensor detects the motion the label will change from No motion detected to Motion detected O O O First Project No motion Detected Start Exit Summary Now you have hands on experience of building a basic GUI to handle Arduino projects With minor modifications to the included exercises you can use them to create a GUI for a large variety of Arduino prototyping projects In the previous two exercises we displayed the sensor outputs as strings in label widgets It will be more meaningful if these numerical values are plotted as a graph and stored for further analysis This is what you are going to perform in the next chapter Chapter 6 Storing and Plotting Arduino Data Sensors that are connected to Arduino produce lots of analog and digital data Analog sensors produce data points as numerical information while digital sensors produce Boolean values that is 1 on or O off Until now we printed this data as a string on the command prompt or displayed it in a GUI The data was being printed in real time and it was not being saved for any further analysis Instead of using the string format if the data is printed as a plot or graph it will provide useful information for us to rapidly understand it and derive conclusions Plots are even more useful for real time appl
35. 9 Maverick comes equipped with Python 2 7 5 which is the latest version Tests Mac test python Python 2 7 5 default Aug 25 2013 00 04 04 GCC 4 2 1 Compatible Apple LLVM 5 0 clang 500 0 68 on darwin Type help copyright credits or license for more information gt gt gt Previous versions such as Mac OS X 10 8 Mountain Lion and Mac OS X 10 7 Lion included Python 2 7 2 and Python 2 7 1 respectively which are also compatible versions for this book If you are an experienced Python user or someone who wants to work with the latest version of Python you can download the latest version from http www python org getit Older versions of Mac OS X such as Snow Leopard and later which came with an older version of Python can be updated to the latest version by downloading and installing it from http www python org getit Installing Setuptools Setuptools is a library containing a collection of utilities for building and distributing Python packages The most important tool from this collection is called easy_install It allows a user to look into PyPI the Python package repository that we mentioned previously and provides a simple interface to install any package by name The easy_install utility automatically downloads builds installs and manages packages for the user This utility has been used in the later part of this book to install the necessary packages required for the upcoming projects of Python and Ardui
36. According to the project setup the PIR sensor provides event inputs to Arduino pin 7 In the test program change the type of pin 7 to Input and wave your hand over the sensor and you should be able to see the status of the pin as High as displayed in the following screenshot Firmata Test Output Output Output Output Output Input Output Output Output Output Output High A v A v A v A v A v A v A v A v A v A v A v A v Output High Analog AO 113 Analog AI 116 Analog A2 117 Analog AB 117 Analog Ej a4 108 Analog Eas 112 dev cu usbmodemfal331 StandardFirmata ino 2 3 Tx 158 Rx 4294 Check the LED connections by setting up pins 12 and 13 as output pins and toggling the buttons to set the status of the pins If you see the LEDs blinking while you are toggling the button then your connections are working perfectly If you cannot successfully perform these checks verify and repeat the design steps Method 1 using a standalone Arduino sketch As we discussed in the previous chapters a project can be implemented by creating project specific native Arduino code or by using a Python Arduino hybrid approach The native Arduino sketches are useful in applications where negligible or no communication with a computer system is required Although this type of standalone project enables continuous operation in the absence of serial connectivity it is difficult to keep updating and uploading
37. Before we go ahead let s first make sure that your Arduino board is equipped with the latest version of the StandardFirmata program and is connected to your computer 1 Depending upon the Arduino board that is being utilized start by importing the appropriate pyFirmata classes to the Python code Currently the inbuilt pyFirmata classes only support the Arduino Uno and Arduino Mega boards from pyfirmata import Arduino In the case of Arduino Mega use the following line of code from pyfirmata import ArduinoMega 2 Before we start executing any methods that are associated with handling pins you need to properly set up the Arduino board To perform this task we have to first identify the USB port to which the Arduino board is connected and assign this location to a variable in the form of a string object For Mac OS X the port string should approximately look like this port dev cu usbmodemfa1331 For Windows use the following string structure port COM3 In the case of the Linux operating system use the following line of code port dev ttyACM0 The port s location might be different according to your computer configuration You can identify the correct location of your Arduino USB port by using the Arduino IDE as described in Chapter 2 Working with the Firmata Protocol and the pySerial Library 3 Once you have imported the Arduino class and assigned the port to a variable object it s time to engage Arduino
38. LED at specified pin number void blinkLED int pin String message digitalwrite pin HIGH Serial println message delay 1000 digitalwrite pin LOW delay 2000 4 Compile and upload the sketch to the Arduino board Now you have completed your project with the first programming method and successfully deployed it to your hardware It should be running the designed algorithm to detect motion events and perform the blink action As your project is functioning properly it s time to understand the code Like any other Arduino program the code has two mandatory functions setup and loop It also has a custom function blinkLED for a specific action that will be explained later The setup function As you can see in the preceding code snippet we assigned variables to the Arduino pin at the beginning of the program In the setup function we configured these variables to be defined as input or output pins pinMode pirPin INPUT pinMode redLedPin OUTPUT pinMode greenLedPin OUTPUT Here pirPin redLedPin and greenLedPin are digital pins 7 12 and 13 respectively In the same function we also configured the Arduino board to provide serial connectively at the baud rate of 9600 bps Serial begin 9600 The loop function In the 1oop function we are repeatedly monitoring the input from the pirPin digital pin to detect motion The output of this pin is HIGH when motion is detected and LOW otherwise
39. Learning Tkinter for GUI design The Entry widget providing manual user inputs o used for providing manual user inputs The Entry widget providing manual user inputs Ethernet class o about The Ethernet class ez_setup py file o URL for downloading Windows Mac OS X Fedora Red Hat Linux o Python installing Fedora and Red Hat files o working with Working with files in Python manipulating with open method The open method write method using The write method closing close method used The close method read method using The read method with statement using The with statement Python context manager Firmata o about Introducing the Firmata protocol o URL What is Firmata Testing the Firmata protocol o StandardFirmata sketch uploading to Arduino board Uploading a Firmata sketch to the Arduino board o testing Testing the Firmata protocol o and pySerial library bridging Bridging pySerial and Firmata Firmata libraries o disadvantages Useful pySerial commands float data type o about Data types formatting tool SD card o URL for downloading Preparing an SD card for statement o about The for statement Fritzing o about Testing the Firmata protocol o using Introducing Fritzing a hardware prototyping software o URL Introducing Fritzing a hardware prototyping software functions o about Functions and statements o setup function The setup fun
40. Line EOL or Line feed Carriage Return LF CR Learn more about the newline character at http en wikipedia org wiki Newline Bridging pySerial and Firmata In the Firmata section we already learned how useful it is to use the Firmata protocol instead of constantly modifying the Arduino sketch and uploading it for simple programs pySerial is a simple library that provides a bridge between Arduino and Python via a serial port but it lacks any support for the Firmata protocol As mentioned earlier the biggest benefit of Python can be described in one sentence There is a library for that So there exists a Python library called pyFirmata that is built on pySerial to support the Firmata protocol There are a few other Python libraries that also support Firmata but we will only be focusing on pyFirmata in this chapter We will be extensively using this library for various upcoming projects as well 1 Let s start by installing pyFirmata just like any other Python package by using Setuptools sudo pin install pyfirmata In the previous section while testing pySerial we uploaded the DigitalSerialRead sketch to the Arduino board To communicate using the Firmata protocol you need to upload the StandardFirmata sketch again just as we did in the Uploading a Firmata sketch to the Arduino board section Once you have uploaded this sketch open the Python interpreter and execute the following script This script impo
41. Once the connection is established you can respond to a request using various methods supported by the server class such as write print and println The Client class The Client class provides methods to create an Ethernet client to connect and communicate with servers The EthernetClient method initializes a client that can be connected to a specific server using its IP address and port number The connect ip port method on the client object will establish a connection with the server on the mentioned IP address EthernetClient client client connect server 80 The Client class also has the connected method which provides the status of the current connection in binary This status can be true connected or false disconnected This method is useful for the periodic monitoring of the connection status client connected Other important client methods include read and write These methods help the Ethernet client to read the request from the server and to send messages to the server respectively Exercise 1 a web server your first Arduino network program The best way to test the Arduino Ethernet library and the Ethernet Shield is by using the built in examples that are deployed with the Arduino IDE If you are using version 1 x of the Arduino IDE you can find a bunch of Ethernet examples by navigating to File Examples Ethernet By utilizing one of these examples we are going to build a web server that
42. Port execute the following script in the terminal where lt username gt is your Linux username sudo usermod a G dialout lt username gt This script will add your username to the dialout group and it should also work for other Linux versions In Linux the Arduino board mostly gets connected as dev ttyACMx where x is the integer value and depends on your physical port address If you are using any other distribution of Linux other than Ubuntu you might want to check out the proper groups associated with the Arduino serial port from the Linux installation page http playground arduino cc Learning Linux of the Arduino website Note For the Fedora Linux distribution add the uucp and lock groups with the dialout group to control the serial port sudo usermod a G uucp dialout lock lt username gt Mac OS X In Mac OS X when you connect your Arduino through a serial port the OS configures it as a network interface In OS X Mavericks once the Arduino board is connected open Network from System Preferences A dialog box should appear that states that a new network interface has been detected Click on OK for Thunderbolt Bridge and then click on Apply The following screenshot displays the dialog box to add a new network interface O Network New Interface Detected 38 A new network interface has been detected e Wi Fi Thunderbolt Bridge Please verify that it is configured correctly then press e e U
43. PowerStrip Computation e Arduino Unit Tweet using mobile Tweet using web app browser Tweet with keyword to toggle power Tweet from any other source Fetch tweet Has keywords to toggle power Ignore for this case Received message from Subscribed channels Publish to channel Turn on off relay Turn on off power Fan Bulb TV on off Toggle power port Similarly the user should be able to post status check tweets and simply obtain the status report posted back by the system The system should handle checking the status of the power ports publishing it to the computation unit and posting a tweet with the message without any additional input from the user The following diagram shows the UX flow for checking the system status PowerStrip Computation Uss Tweet using mobile Tweet using web Tweet from any app browser other source Tweet with Fetch tweet keywords to check status Arduino Unit status Ignore for y this case Subscribe to this Publish to message channel to ask for status Check status Publish status Received status Post tweet with status Check port status Development and deployment stages According to the architecture we require two main development stages to complete the project The first stage which interacts with the appliance through the relays is developed using Arduino This unit subscribes to the topics associated with the appl
44. Raspberry Pi TFT LCD is a great way to expand the Raspberry Pi s functionalities and avoid the use of large display devices These TFT LCD displays can be interfaced directly with GPIO pins TFT LCD screens are available in various shapes and size but for the Raspberry Pi we recommend that you use a screen with a size smaller than or equal to 3 2 inches due to interfacing convenience Most of these small screens do not require additional power supply and can be directly powered using the GPIO pins In a few cases touch screen versions are also available to extend the functionality of the Raspberry Pi In this project we are using a Tontec 2 4 inch TFT LCD screen that can be directly interfaced with the Raspberry Pi via GPIO Although you can use any available TFT LCD screen this book only cover the setup and configuration process for this particular screen In most cases manufacturers of these screens provide detailed configuration tutorials on their websites Raspberry Pi forums and blogs are another good places to look for help if you are using a different type of the TFT LCD screen The following image shows the back of the Tontec 2 4 inch TFT LCD screen with the location of the GPIO pins Let s get started and use this screen with your Raspberry Pi J u EU arran meint JUOT Connecting the TFT LCD using GPIO Before we can use the screen we will have to connect it to the Raspberry Pi Let s disconnect the micro US
45. Temperature C TempLabel config text cleanText reading 1 TempUnitLabel config text C TempUnitLabel update_idletasks if reading 0 Temperature F TempLabel config text cleanText reading 1 TempUnitLabel config text F TempUnitLabel update_idletasks Swapping between the GUI and the plot by pressing a button If the Python code receives the value of the flag from the serial port as 1 HIGH it creates a new plot and draws the humidity values as a line chart However it closes any open plots if it receives 0 LOW as the value of the flag As you can see in the following code snippet the program will always try to update the plot with the latest values for humidity readings If the program can t find an opened plot to draw this value from it will create a new plot if reading 0 Flag print reading 1 if int reading 1 1 try 11 set_xdata np arange len pData 11 set_ydata pData update the data pyplot ylim 100 pyplot draw update the plot except pyplot figure pyplot title Humidity axi pyplot axes 11 pyplot plot pData pyplot ylim 0 100 if int reading 1 0 try pyplot close all 11 None except By now you should have a complete idea about the programs that are required by the thermostat sensor unit and the computation unit Due to the complexity involved you may face a few known problems during the execution of these programs You can refer to
46. This logic is implemented using a simple if else statement When this condition is satisfied the function calls a user defined function blinkLED to perform the appropriate action on the LEDs User defined functions are a very important aspect of any programming language Let s spend some time learning how you can create your own Arduino functions to perform various actions Working with custom Arduino functions Functions are used when a segment of code is repeatedly executed to perform the same action A user can create a custom function to organize the code or perform reoccurring actions To successfully utilize a custom function a user needs to call them from mandatory Arduino functions such as loop setup or any other function that leads to these mandatory functions return type function_name parameters Action to be performed Action_1 Action_2 Return expression In the preceding Arduino function framework return type can be any Arduino data type such as int float string and so on or void if the code is not returning anything The following is the custom function that we used in our project code void blinkLED int pin String message digitalwWrite pin HIGH Serial println message delay 1000 digitalwrite pin LOW delay 2000 In our project the blinkLED function is not retuning any value when it is called from the loop function Hence return type is void When calling the function we
47. Tweet a PowerStrip The Arduino code Arduino data o o storing in CSV file Storing Arduino data in a CSV file plotting from CSV file Plotting data from a CSV file e Arduino Ethernet library o O O O O o about Arduino Ethernet library URL Arduino Ethernet library Ethernet class The Ethernet class IPAddress class The IPAddress class Server class The Server class Client class The Client class e Arduino Ethernet Shield o o about Arduino Ethernet Shield URL Arduino Ethernet Shield e Arduino IDE Oo 00000000000 0 0 o about Arduino variants Getting started with the Arduino IDE installing Installing the Arduino IDE installing on Linux Linux URL for installation on Ubuntu Linux URL for installation on Fedora Linux installing on Mac OS X Mac OS X installing on Windows Windows URL for setup file Windows sketch What is an Arduino sketch libraries Working with libraries examples using Using Arduino examples URL for built in examples Using Arduino examples sketch compiling Compiling and uploading sketches sketch uploading Compiling and uploading sketches serial monitor using Using the Serial Monitor window e Arduino interrupts o o o about Using Arduino interrupts using Using Arduino interrupts reference link Using Arduino interrupts e Arduino pins o O O O O 0 0 o configuring Configuring Arduino pin
48. Use iterator thread to avoid buffer overflow it pyfirmata util Iterator board it start Define pins pirPin board get_pin d 7 i redPin 12 greenPin 13 Check for PIR sensor input while True Ignore case when receiving None value from pin value pirPin read while value is None pass if value is True Perform Blink using custom function blinkLED redPin Motion Detected else Perform Blink using custom function blinkLED greenPin No motion Detected Release the board board exit You have successfully created and executed your first Arduino project using Python There are two main programming components in this code pyFirmata methods and the Python function to perform the blinking action The program repeatedly detects the motion events and performs the blinking action In the previous section this problem was solved by using the default Arduino function 1oop In this method we have implemented the while statement to keep the program in loop until the code is manually terminated by the user You can terminate the code using the keyboard combination Ctrl C Working with pyFirmata methods As part of working with the Arduino board and the Firmata protocol you have to start by initializing the Arduino board as a variable The pyFirmata method that lets a user assign the board to a Python variable is as follows board pyfirmata Arduino port Once the value of the variable is assigned yo
49. We also provide you with a PDF file that has color images of the screenshots diagrams used in this book The color images will help you better understand the changes in the output You can download this file from http www packtpub com sites default files downloads 59380S_ColoredImages pdf Errata Although we have taken every care to ensure the accuracy of our content mistakes do happen If you find a mistake in one of our books maybe a mistake in the text or the code we would be grateful if you could report this to us By doing so you can save other readers from frustration and help us improve subsequent versions of this book If you find any errata please report them by visiting http www packtpub com submit errata selecting your book clicking on the Errata Submission Form link and entering the details of your errata Once your errata are verified your submission will be accepted and the errata will be uploaded to our website or added to any list of existing errata under the Errata section of that title To view the previously submitted errata go to https www packtpub com books content support and enter the name of the book in the search field The required information will appear under the Errata section Piracy Piracy of copyrighted material on the Internet is an ongoing problem across all media At Packt we take the protection of our copyright and licenses very seriously If you come across any illegal copies of our wo
50. Web application Sensor data relay Amazon AWS Xively In the previous stage we already covered the process of setting up Xively and the channels to accommodate sensor data In the control center code we also explained how we can push the updated observations to the appropriate Xively channels Therefore we really do not have any ground to cover for the Xively platform at this stage and we can move on to the web application Python web application hosted on Amazon AWS In the previous chapter we set up an Amazon AWS cloud instance to host a web application You can use the same instance to host the web application for the remote home monitoring system too However make sure that you have installed the web py library on your server 1 In your computer open the web_Application folder and then the RemoteMonitoringApplication py file in your editor 2 In the code you will be able to see that we just expand the web application program that we created in Chapter 9 Arduino and the Internet of Things We use the templates based on web py and the GET and POST functions to enable the web application 3 In the application we fetch information from each Xively channel and process it via a separate function For example the fetchTempXively function obtains the temperature information from Xively Every time the POST function is executed the fetchTempXively function fetches the latest value of temperature reading from Xivel
51. additional delay for httplib to successively send the data and receive the response we will be able to avoid this delay when we implement the core Python code with threading avoiding the entire notion of POST in between the programs eoo Python 2 7 6 Shell Python 2 7 6 default Apr 28 2014 02 15 56 GCC 4 2 1 Compatible Apple LLVM 5 1 clang 503 0 40 on darwin Type copyright credits or license for more information gt gt gt cronos RESTART Se ssesesesnnnssosnssmsseumsmmnnuunn gt gt gt Arduino humidity lt httplib HTTPResponse instance at 0x10d5387a0 gt Arduino motion lt httplib HTTPResponse instance at 0x10d5387a0 gt Arduino humidity lt httplib HTTPResponse instance at 0x10d5387a0 gt Arduino motion lt httplib HTTPResponse instance at 0x10d5387a0 gt With this exercise you have implemented two different types of messaging architecture to transfer data between your Arduino and your computer or web applications using your home network Although we recommend the use of hardware centric and lightweight MQTT messaging paradigms over REST architecture you can use either of these communication methods according to the application s requirements Summary Connectivity to computer networks can really open up limitless possibilities for future application development using Arduino We started the chapter by explaining important computer network fundamentals while also covering hardware extensions that e
52. arduino Answers to additional installation questions for Fedora can be obtained at http playground arduino cc Linux Fedora Mac OS X To install the Arduino IDE on Mac OS X 10 7 or newer perform the following steps 1 From http arduino cc en Main Software download the latest version of the Arduino IDE for Mac OS X which was 1 0 5 when this book was being written 2 Unzip and drag Arduino to the application folder The Arduino IDE is built in Java and requires that your computer is equipped with the appropriate version of Java Open the IDE from your applications If you don t have Java installed on your Mac the program will prompt you with a pop up window and ask you to install Java SE 6 runtime Go ahead and install Java as per the request as the OS X will automatically install it for you Windows Installation of Arduino for Windows is very simple Download the setup file from http arduino cc en Main Software Select the most recent version of the Arduino IDE that is 1 0 x or a newer version Make sure you download the appropriate version of the Arduino IDE according to your operating system that is 32 bit or 64 bit Install the IDE to the default location as specified in the installation wizard Once installed you can open the IDE by navigating to Start Programs Getting started with the Arduino IDE The Arduino IDE is a cross platform application developed in Java that can be used to develop compile and upl
53. as a replacement for a regular computer the architecture of the control center can interchangeably use a computer in place of the Raspberry Pi As you can see in the following diagram the control center is connected to the home network using Wi Fi and this will make it accessible to the monitoring station The control center includes the Mosquitto broker this is used as the communication point between the monitoring station and the Python program for the control center The Python program utilizes the Tkinter library for GUI and the paho_mqtt library to communicate with the Mosquitto broker By utilizing these two libraries we can convey sensor information from the monitoring station to the user However we will need a separate arrangement to establish communication between the control center and cloud services In our overall system architecture the control center is designed to communicate with the intermediate data relay Xively The Python code uses the xively python library to enable this communication ES TFT LED Screen ji gt gt From 2 3 Monitoring L 2 Control center 5 Ui Station WiFi 3 5 ce lie x service ie re lt Raspberry Pi Control Center In Chapter 8 Introduction to Arduino Networking we already provided you with methods to install the Mosquitto broker the Python mosquitto library and the xively python library We also learned the process of setting up the TFT
54. as displayed in the following diagram eevee e t o eevee Note While working with the programs provided in this and upcoming sections you will have to replace the Arduino port that is used to define the board variable according to your operating system To find out which port your Arduino board is connected to follow the detailed instructions provided in Chapter 2 Working with the Firmata Protocol and the pySerial Library Also make sure that you provide the correct pin number in the code if you are planning to use any pins other than 10 and 11 For some exercises you will have to use the PWM pins so make sure that you have correct pins In the previous exercise we asked you to use the entire code snippet as a Python file and run it This might not be possible in the upcoming exercises due to the length of the program and the complexity involved Therefore we have assembled these exercises in the program files that can be accessed from the code folder of Chapter 4 Diving into Python Arduino Prototyping which can be downloaded from https www packtpub com books content support 1961 For the Button widget exercise open the exampleButton py file from the code folder of Chapter 4 Diving into Python Arduino Prototyping The code contains three main components e The pyFirmata library and Arduino configurations e The Tkinter widget definitions for a button e The LED blink function that gets executed whe
55. be used to manage the Mosquitto password files and the setup broker configuration respectively Getting started with MQTT on Arduino and Python Now that you have the Mosquitto broker installed on your computer it means that you have a working broker that implements the MQTT protocol Our next goal is to develop the MQTT clients in Arduino and also in Python so that they will work as publishers and subscribers After implementing the MQTT clients we will have a fully functional MQTT system where these clients communicate through the Mosquitto broker Let s begin with deploying MQTT on the Arduino platform MQTT on Arduino using the PubSubClient library As MQTT is a network based messaging protocol you will always need an Ethernet Shield to communicate with your network For the following exercise we will continue using the same hardware that we have been using throughout this chapter Installing the PubSubClient library To use Arduino for pub sub and enable simple MQTT messaging you need the Arduino client library for MQTT also known as the PubSubClient library The PubSubClient library helps you develop Arduino as an MQTT client which can then communicate with the MQTT server Mosquitto broker in our case running on your computer As the library provides methods to create only an MQTT client and not a broker the footprint of the Arduino code is quite small compared to other messaging paradigms The PubSubClient library extensively
56. be wondering what a mobile unit with sensors Arduino Raspberry Pi and TFT screen might look like The following image shows a sample thermostat that was developed using the instructions given in this chapter We used an acrylic sheet to hold the Raspberry Pi and the Arduino board together and created a compact form factor Troubleshooting There are a few known problems that you may face in this stage of the project The following section describes these problems and their quick fixes e The Raspberry Pi is not booting up o Make sure that the SD card is formatted properly with the specified tools The Raspberry Pi won t boot if the SD card is not prepared properly o Check the HDMI cable and the monitor to see whether they are working fine o Make sure that the power adapter is compatible with the Raspberry Pi e The TFT LCD screen doesn t turn on o Make sure that the screen is properly connected to the GPIO pins of the Raspberry Pi o If you are using any other TFT LCD screen make sure from its datasheet that your screen doesn t require additional power o Check whether the screen is properly configured using the steps described in the Optimizing the GUI for the TFT LCD screen section e There is a slow refresh rate of the sensor data on the Raspberry Pi o Try decreasing the delay between each serial message that is sent by Arduino o Terminate any other application that is running in the background Summary With
57. broker you can start Mosquitto by executing the following command in the terminal After executing it you should be able to see the broker running while printing the initialization parameters and other requests coming to it mosquitto When you installed the Mosquitto broker the installation process would also have installed a few Mosquitto utilities which include the MQTT clients for the publisher and the subscriber These client utilities can be used to communicate with any Mosquitto broker To use the subscriber client utility mosquitto_sub use the following command at the terminal with the IP address of the Mosquitto broker As we are communicating to the Mosquitto broker running on the same computer you can avoid the h lt Broker 1P gt option The subscriber utility uses the t option to specify the name of the topic that you are planning to subscribe As you can see we are subscribing to the test topic mosquitto_sub h lt Broker IP gt t test Similar to the subscriber client the publisher client mosquitto_pub can be used to publish a message to the broker for a specific topic As described in the following command you are required to use the m option followed by a message to successfully publish it In this command we are publishing a Hello message for the test topic mosquitto_pub h lt Broker IP gt t test m Hello Other important Mosquitto utilities include mosquitto_password and mosquitto conf which can
58. clients with the Python web server e loT messaging protocol MQTT we will install a middleware tool called Mosquitto to enable MQTT on our computer e Utilizing the publisher subscriber paradigm used by MQTT to develop Arduino Python web applications Arduino and the computer networking Computer networking is a huge domain and covering every aspect of networking is not the main objective of this book We will however try to explain a few fundamentals of computer networking wherever this knowledge will need to be applied Unlike the serial interface approach where a point to point connection is required between devices the network based approach provides distributed access to resources Specifically in hardware applications where a single hardware unit is required to be accessed by multiple endpoints for example in a personal computer mobile phone or remote server the computer network stands superior In this section we will cover the basics of networking and hardware components that enable networking in Arduino Later in this chapter we will use the Arduino library and a built in example to demonstrate how remote access to Arduino using your local network works Networking fundamentals Whenever you see a computer or mobile device you are also looking at some type of computer network being used to connect those devices with other devices In simple terms a computer network is a group of interconnected computational devices al
59. code snippet to make this possible import sys csv from matplotlib import pyplot import pyfirmata from time import sleep import numpy as np Associate port and board with pyFirmata port dev cu usbmodemfa1321 board pyfirmata Arduino port Using iterator thread to avoid buffer overflow it pyfirmata util Iterator board it start Assign a role and variable to analog pin 0 a0 board get_pin a 0 i Initialize interactive mode pyplot ion pData 0 25 fig pyplot figure pyplot title Real time Potentiometer reading ax1 pyplot axes 11 pyplot plot pData pyplot ylim 0 1 real time plotting loop while True try sleep 1 pData append float a0 read pyplot ylim 1 del pData 0 11 set_xdata i for i in xrange 25 11 set_ydata pData update the data pyplot draw update the plot except KeyboardInterrupt board exit break The real time plotting in this exercise is achieved by using a combination of the pyplot functions ion draw set_xdata and set_data The ion method initializes the interactive mode of pyplot The interactive mode helps to dynamically change the x and y values of the plots in the figure pyplot ion Once the interactive mode is set to True the plot will only be drawn when the draw method is called Just like the previous Arduino interfacing exercises at the beginning of the code we initialized the Arduino boa
60. com id Arduino Home Monitor System e It can be used in automatic garage door opener applications with the support of additional hardware components and appropriate code e In DIY wildlife recording projects it can be used to trigger a camera instead of an LED when any motion is detected http www instructables com id Motion triggered camera The list of components In the previous chapter we only used an LED for programming using Arduino an Arduino USB cable and a computer The major hardware component required for this project is a PIR motion sensor You will also need an additional LED We recommend that you have a different colored LED than the one that you already have The description of the necessary components is as follows e PIR sensors These are widely used as motion detection sensors for DIY projects They are small inexpensive consume less power and are compatible with hardware platforms such as Arduino A PIR sensor uses a pair of pyroelectric sensors that detect infrared radiation If there is no motion the output of these sensors cancels each other out Any movement in the environment will produce different levels of infrared radiation by these pyroelectric sensors and the difference will trigger an output that is HIGH 5 volts We will be using the PIR sensor that is sold by SparkFun and you can obtain it from https www sparkfun com products 8630 The PIR sensor comes equipped with the required printed circuit bo
61. data types that are used in the C language A list of these data types and their descriptions are as follows e void This is used in the function declaration to indicate that the function is not going to return any value void setup actions e boolean Variables defined with the data type boolean can only hold one of two values true or false boolean ledState false e byte This is used to store an 8 bit unsigned number which is basically any number from 0 to 255 byte b OxFF e int This is short for integers It stores 16 bit Arduino Uno or 32 bit Arduino Due numbers and it is one of the primary number storage data types for the Arduino language Although int will be used to declare numbers throughout the book the Arduino language also has long and short number data types for special cases int varInt 2147483647 long varLong varlInt short varShort 32768 e float This data type is used for numbers with decimal points These are also known as floating point numbers float is one of the more widely used data types along with int to represent numbers in the Arduino language float varFloat 1 111 e char This data type stores a character value and occupies 1 byte of memory When providing a value to char data types character literals are declared with single quotes char myCharacater P e array An array stores a collection of variables that is accessible by an index number If you ar
62. delivers the sensor values when requested by a web browser As Arduino will be connected to your home network through the Ethernet you will be able to access it from any other computer connected to your network The major goals for this exercise are listed here e Use the Arduino Ethernet library with the Arduino Ethernet Shield extension to create a web server e Remotely access Arduino using your home computer network e Utilize a default Arduino example to provide humidity and motion sensor values using a web server To achieve these goals the exercise is divided into the following stages e Design and build hardware for the exercise using your Arduino and the Ethernet Shield e Run a default example from the Arduino IDE as the starting point of the exercise e Modify the example to accommodate your hardware design and redeploy the code The following is a Fritzing diagram of the circuit required for this exercise The first thing you should do is mount the Ethernet Shield on top of your Arduino Uno Ensure that all the pins of the Ethernet Shield are aligned with the corresponding pins of the Arduino Uno Then you need to connect the previously used humidity sensor HIH 4030 and the PIR motion sensor PIR motion sensor HIH 4030 Note While deploying the Arduino hardware for remote connectivity without USB you will have to provide external power for the board as you no longer have a USB connection to power the board
63. devices and data streams on Xively Open your Xively account and create a virtual device called Controlcenter Note down the feed ID and API key for this device and replace them in the current code Once you have these values create the Temperature Humidity Light Motion Buzzer and Status channels in this virtual device Looking at the Python code you can see that we have declared the individual data stream for each topic and associated them with the appropriate Xively channel The following code snippet shows the data stream for just the temperature observation but the code also contains a similar configuration for all the other sensor observations try datastreamTemp feed datastreams get Temperature except HTTPError as e print HTTPError 03 1 format e errno e strerror datastreamTemp feed datastreams create Temperature tags C print Creating new channel Temperature Once the control center receives a message from the monitoring station it updates the data stream with the latest values and pushes these changes to Xively At the same time we will also update the appropriate label in the Tkinter GUI using the onMessage function We will use the same code snippet for all the subscribed channels if msg topic MonitoringStation temperature tempG float msg payload window tempValue set tempG datastreamTemp current_value tempG try datastreamTemp update except HTTPError as e print HTTPError 0
64. examples e Code to replace occurrences of a string or substring with a different one gt gt gt str Hello World gt gt gt str replace World Universe Hello Universe e Code to split a string with a separating character where the default character is space gt gt gt str Hello World gt gt gt str split Hello World e Code to split a string from a separating character for any other character gt gt gt str2 John Merry Tom gt gt gt str2 split John Merry Tom Code to convert an entire string value into uppercase or lowercase gt gt gt str Hello World gt gt gt str upper HELLO WORLD gt gt gt str lower hello world Note The Python documentation on the official website covers every built in function in detail with examples For better understanding of Python programming visit https docs python org 2 library functions html Introduction to Arduino Any electronic product that needs computation or interfacing with other computers first requires a quick prototyping of the concept using simple tools Arduino is an open source hardware prototyping platform designed around a popular microcontroller family and it includes a simple software development environment Besides prototyping you can also use Arduino for the development of your own do it yourself DIY projects Arduino bridges the computational world with the physical world b
65. from the timePeriodEntry object You can use the get method to obtain the entered value from the timePeriodEntry object and convert it into a floating value using the float function As you can see in the following code snippet we use this float value as the time delay between switching the LED off from the on state def onStartButtonPress Value for delay is obtained from the Entry widget input timePeriod timePeriodEntry get timePeriod float timePeriod startButton config state Tkinter DISABLED ledPin write 1 sleep timePeriod ledPin write 0 startButton config state Tkinter ACTIVE Once you have understood the process of initializing the Entry widget and the method to obtain a custom value from it let s execute the code When you run this exercise you should be able to see a window similar to the one displayed in the following screenshot Enter a time delay value in seconds and click on Start to see the results on the LED Basically when the button is pressed the program will call the onStartButtonPress function and it will utilize this value to produce the time delay O Specify time using Entry The Scale widget adjusting the brightness of an LED In this section we will develop some code to change an LED s brightness using the Python GUI Previously we learned that you can use a digital pin of Arduino to produce an analog output using PWM Although you can use the Entry widget to provide
66. is 0 0 v M Autoscroll No line ending I 9600 baud B Python uploading data to Xively Similar to how we interfaced Arduino to Xively we will now explore methods to connect the Xively platform via Python and thus complete the loop In this section we will focus on different ways of uploading data to Xively using Python We will start with a basic method of communicating with Xively and extend it further with web py to implement the interface using a web application To begin with let s first install Xively s Python library xively python on your computer using the following command sudo pip install xively python The basic method for sending data Once again you will need the API key and feed ID of your virtual device that you created on the Xively platform Python assisted by the xively python library provides very simple methods to establish a communication channel with the Xively platform From your code folder open the uploadBasicXively py file As specified in the code replace the FEED_ID and API_KEY variables with the appropriate feed ID and API key lt Your feed ID gt lt Your API key gt FEED_ID API_KEY Using the xivelyAPIClient method create an api instance and create the feed variable by using the api feeds get method api xively XivelyAPIClient API_KEY feed api feeds get FEED_ID Just as we did in the Arduino exercises you will need to create data streams for each channel from th
67. is time to define the two main methods GET and POST to respond to the request coming from the web page When you launch or refresh the web page the web py server generates the GET request which is then handled by the GET function of the Index class So during the execution of the GET method the program obtains the latest raw humidity value from the serial port and calculates the relative humidity using the relativeHumidity method Note In the process of dealing with the GET request we are not submitting any form with the user input For this reason in the GET method we will use the default value of temperature 25 for the relativeHumidity method Once the humidity value is derived the program will render the base template using the render base function as displayed in the following code snippet where base refers to the base template def GET self f self submit_form f validates line port readline if line data float line humidity relativeHumidity line 25 return render base f humidity else return render base f Not valid data Contrary to the GET method the POST method is invoked when the form is submitted to the web page The submitted form includes the temperature value provided by the user which will be used to obtain the value of the relative humidity Like the GET function the POST function also renders the base template with the recent humidity value once the humidity is calc
68. moved the publishing statement of outTopic from setup to the 1oop function This action will help us to periodically publish the value for outTopic In future we will expand this method to use sensor information as messages so that the other devices can obtain those sensor values by subscribing to these sensor topics void loop client publish outTopic From Arduino delay 1000 client loop After updating the mqtt_advance sketch with the appropriate network addresses compile and upload the sketch to your Arduino hardware To test the Arduino client use the same mosquitto_sub command to subscribe to outTopic This time you will periodically get updates for outTopic on the terminal To check out the subscriber functionality of your Arduino client open your Serial Monitor window in your Arduino IDE Once the Serial Monitor window begins running execute the following command in the terminal mosquitto_pub t inTopic m Test You can see in the Serial Monitor window that the Test text is printed with the topic name as inTopic Henceforth your Arduino will serve as both an MQTT publisher and an MQTT subscriber Now let s develop a Python program to implement the MQTT clients MQTT on Python using paho matt In the previous exercise we tested the Arduino MQTT client using command line utilities Unless the published and subscribed messages are captured in Python we cannot utilize them to develop all the other app
69. need them to authenticate with the Twitter API Details Settings API Keys Permissions Application settings API key API secret Access level Read only modify app permissions Owner Tweet_a_ Strip Owner ID 5 As the UX of the Tweet a PowerStrip project requires the system to automatically send the system status we need read and write access to our application Go to the Permissions tab select the Read and Write option and save it for the changes to take effect Details Settings API Keys Permissions Access What type of access does your application need d r Application Permission Model Read only Read and Write C Read Write and Access direct messages 6 Once you are done with setting up the permissions for the application go back to the API keys tab and click on the Create Access Token icon to generate a new access token for this application After a while you should be able to see the access token on the same page as displayed in this screenshot Your access token Access token Access token secret r sx 5 pr Access level Read and write Owner Tweet_a_Strip Owner ID 7 Save the Access token and Access token secret information Your application is now ready for use and can help you to authenticate with the Twitter API Now let s move on to the Python code The Python code Before you jump into the code you are required to install the Twitter library for
70. need to be careful about the version of Python that you are downloading From the system properties of your Windows OS check whether the operating system is of 32 bit or 64 bit At the time this book was being written the latest version of Python was 2 7 6 So download the latest available version of Python but make sure that it is 2 7 x and not 3 x For many third party Python libraries the installation binary files for Windows are compiled for the 32 bit version Due to this reason we will recommend that you install the 32 bit version of Python for your Windows OS If you are really familiar with Python and know your way around installing libraries you can install the 64 bit version of Python Select and run the downloaded file to install Python Although you can install it to any custom location it is advisable to use the default installation location as the upcoming configuration steps use the default location Once the installation is complete you can find the Python command line tool and IDLE Python GUI from the Start menu Although you can always open these tools from the Start menu for basic scripting we will modify the Windows system parameters to make Python accessible through the Windows command prompt To accomplish this we will have to set up PATH in environment variables for the location of the Python installation directory Let s open System Properties by right clicking on My Computer and then selecting Properties Otherwis
71. node in the network It responds to the requests made by the distributed network nodes called clients that query it In this paradigm the client initiates a request for the state directed towards the server while the server responds to the state request without storing the client context This communication is always one directional and always initiated from the client side HTTP GET Response HTTP POST Response REST architecture To further explain the state transfer for the GET and POST requests check out the previous diagram When a client sends a GET request to a server using a URL the server responds with raw data as the HTTP response Similarly in the POST request the client sends data as payload to the server while the server responds with simply a received confirmation message REST methods are relatively simple to implement and develop using simple HTTP calls We are going to start developing Arduino networking applications using REST based requests as they are easy to implement and understand and are directly available through examples We will begin by individually implementing REST based Arduino clients for HTTP based GET and POST methods Later in this chapter we will go through an exercise to combine the GET and POST methods through the same Arduino REST client while developing the HTTP server using web py Working with the GE T request from Arduino In this exercise we will implement the HTT
72. o Check the LED connections on the breadboard e The LED blinks but there is no serial output o Check whether you have successfully installed the standard Firmata sketch to the board e There is no serial output and no blinking LEDs o Check whether any program other than Python is using the serial port Close any program that might be using that serial port including the Arduino IDE o Verify all the circuit connections o Make sure that the port name specified in the Python code is correct Summary Between the two programming methods that you learned in this chapter the method that uses just an Arduino sketch represents the traditional paradigm of programming a microcontroller While this method is simple to implement it lacks the extensiveness that is achieved by Python Arduino interfacing Although we will use extensive Arduino coding in all the projects beginning from now exercises and projects will have Python Arduino interfacing as the primary way of programming Starting from the next chapter we are going to explore the additional aspects of Python programming that can extend the usability of an Arduino based hardware project while keeping the programming difficulty levels to a minimum We will begin with Python Arduino prototyping and then create graphical interfaces for user interaction before stopping for the second project that utilizes these concepts Chapter 4 Diving into Python Arduino Prototyping On the comple
73. o First run the current code on your Raspberry Pi and if you see that the GUI window does not match the screen add the following line of code after initializing the main window top minsize 320 200 o This code will fix the problem with the size for a 2 8 inch TFT LCD screen In the previous code snippet 320 and 200 represent the pixel sizes for width and length respectively For other screen sizes change the pixel size accordingly e Test the LED o In current code configuration the LED is turned on only when the system changes to Alert or Caution That means you won t be able to test the LEDs unless these situations occur To check whether they are working correctly execute the following command at the control center mosquitto pub t MonitoringStation led m red o This command will light up the LED in red To turn off the LED just use off instead of red in the previous code If nothing lights up you should check the connection wires of the LEDs In addition check for network related issues as the Mosquitto itself might not be working If you see any color other than red this means that you haven t connected the LED correctly and you need to interchange the pin configuration of your LED If you are using an LED different than super flux RGB you should check out the pin layout in the datasheet and reorganize the connections Extending your remote home monitoring system To successfully create commercial products f
74. observation for that particular sensor type e On the user side the web server obtains the current sensor type through the web browser e When the submit button in the browser is pressed the server updates the sensor value in the browser with the latest value The Arduino sketch for the exercise Using the same Arduino hardware we built open the Arduino sketch named WebPyEthernetArduinoGETPOST ino from the Exercise 3 RESTful application Arduino and webpy code folder As we described in the exercise s architecture earlier the Arduino client should periodically send GET requests to the server and get the corresponding value of the sensor type in the response After comparing the sensor type the Arduino client fetches the current sensor observation from the Arduino pins and sends that observation back to the server using POST if client connected if client find Humidity Fetch humidity sensor value if client connect 10 0 0 20 8080 Post humidity values else Fetch motion sensor value if client connect 10 0 0 20 8080 Post motion values Add delay After changing the appropriate server s IP address in the code compile and upload it to the Arduino Open the Serial Monitor window where you will find unsuccessful connection attempts as your web py server is not yet running Close any other instance or program of the web py server running on your computer The web py appli
75. of a large amount of open library packages which can be used to build applications that span from dynamic websites to complex data analysis applications as well as the development of simple GUI based applications to plot charts from complex math functions The majority of Python library packages have systematically maintained the code that was obtained from the community with regular updates The de facto repository that indexes the largest number of Python packages is PyPI http pypi python org PyPI also provides simple ways to install various packages on your operating system which will be covered in the upcoming section While working with the hardware platform it is necessary to have some means of communication between the hardware and the computer that you are using for development Among the common computer to hardware interfacing methods serial port based communication is the most popular and it is really simple to establish especially for the Arduino platform Python provides a library called pySerial that is really easy to use and quick to implement to interface a serial port It is really simple to use similar libraries and Python s interactive programming abilities to rapidly test and implement your project ideas Nowadays complex Internet of Things IoT applications not only require serial communication support but they also need additional high level features such as graphical user interfaces GUIs for operating systems
76. of the code we are interfacing the serial port using the Serial method from the pySerial library Don t forget to change the serial port name as it may be different for your computer depending on the operating system and physical port that you are using import serial port serial Serial dev tty usbmodemfa1331 9600 timeout 1 Once the port object for the serial port is created the program starts reading the text coming from the physical port using the readline method Using the relativeHumidity function we convert the raw humidity data to appropriate relative humidity observations line port readline if line data float line humidity relativeHumidity line 25 On the web server side we will be using all the major web py components you learned in the previous section to complete this goal As part of it we are implementing an input form for the temperature value We will capture this user input and utilize it with the raw sensor data to calculate relative humidity Therefore we need to define the render object to use the template directory In this exercise we are only using the default landing page location for the web server which is directed towards the Index class render web template render templates As you can see in the WebPySerialExample_ Python folder we have a directory called templates This directory contains a template with the base html filename As this is an HTML file it is lik
77. onStopButtonPress redPin write 0 greenPin write 0 Since you have now learned about the Tkinter variables and the Checkbutton widget let s run the Python program exampleCheckbutton py As you can see in the next screenshot the GUI has two Checkbutton widgets each for the red and green LEDs As there is a separate initialization of the Checkbutton widgets a user can check both the red and green LEDs Tkinter also provides similar widgets such as Radiobutton and Listbox for cases where you want to select only a single value from the given options A O O Checkbox example Y Red LED M Green LED Start Stop Exit Note You can learn more about the Radiobutton and Listbox widgets from the following web pages e http effbot org tkinterbook radiobutton htm e http effbot org tkinterbook listbox htm The Label widget monitoring I O pins Arduino projects often deal with real time systems and are required to continuously monitor input values from digital and analog pins Therefore if these values are being displayed on a graphical interface they need to be updated periodically or when the state of a pin changes If you observe the previous GUI exercises you will notice that we initialized the root window using mainloop at the end of the code which started the Tkinter loop and initialized all the widgets with the updated values Once the mainloop was initialized we did not use any other Tkinte
78. organize the widget in the root window In the case of multiple widgets if the positions for the widgets are not specified the Pack manager arranges them in the same root window The Pack manager is simple to implement but it has a limitation in terms of its degree of customization An alternative geometry manager that is helpful to create a complex layout is called Grid which is explained in the upcoming sections We will cover additional widgets and their associated methods in the upcoming coding exercises In these exercises we will explain each individual widget with practical applications to give you a better understanding of the use cases The Button widget interfacing GUI with Arduino and LEDs Now that you have had your first hands on experience in creating a Python graphical interface let s integrate Arduino with it Python makes it easy to interface various heterogeneous packages within each other and that is what you are going to do In the next coding exercise we will use Tkinter and pyFirmata to make the GUI work with Arduino In this exercise we are going to use the Button widget to control the LEDs interfaced with the Arduino board Before we jump to the exercises let s build the circuit that we will need for all upcoming programs The following is a Fritzing diagram of the circuit where we use two different colored LEDs with pull up resistors Connect these LEDs to digital pins 10 and 11 on your Arduino Uno board
79. perform the LED action int retD xivelyclient get feedD xivelyKey Serial print xivelyclient get returned In the second stage of the periodic function we obtain the raw sensor values from the analog and digital pins of the Arduino board and then upload those values using feedu int humidityValue analogRead A0 datastreamU 0 setFloat humidityValue int pirValue digitalRead pirPin datastreamU 1 setFloat pirValue int retU xivelyclient put feedU xivelyKey Serial print xivelyclient put returned Make the appropriate changes in the code to accommodate feed ID and API key and then upload the sketch to the Arduino board Once you upload this Arduino sketch to your platform you should be able to see the following output on the Serial Monitor window You can now disconnect your Arduino from the USB port and connect the external power supply Now that you have connected your Arduino assembly to your local network using an Ethernet cable you can place the Arduino assembly at any location in your workplace usbmodemfa1331 _ Raw humidity and motion values sent to xively xivelyclient get returned 209 Datastream is id LED current_value 0 00 LED value is 0 09 LED status updated from xively channel value xivelyclient put returned 209 Row humidity and motion values sent to xively xivelyclient get returned 209 Datastream is ie LED current_value 0 00 2 LED value
80. port 80 to the port used by web py 8080 if client connect server 8080 Serial printin connected Make a HTTP request client println GET data HTTP 1 1 client println Host 10 0 0 20 client println Connection close client println Once you have made all of these changes go to the Arduino_GET_Webpy ArduinoGET folder and open the ArduinoGET ino sketch Compare your modified sketch with this sketch and perform the appropriate changes Now you can save your sketch and compile your code for any errors At this stage we are assuming that you have the Arduino Ethernet Shield mounted on your Arduino Uno Connect the Ethernet Shield to your local network using an Ethernet cable and connect Uno with your computer using a USB cable Upload the sketch to the Arduino board and open the Serial Monitor window to check the activity At this stage Arduino would not be able to connect to the server because your web py server is still not running You can close the serial monitor for now The HTTP server using web py to handle the GET request In your first web py application you developed a server that returned Hello world when requested from a web browser Despite all the additional tasks it can perform your web browser is an HTTP client at its core This means that if your first web py server code was able to respond to the GET request made by the web browser it should also be able to respond to the Arduino we
81. port 80 we used a web browser to access the web server Web browsers are one of the most popular types of web clients used to access a web server CURL Wget and web crawlers are the other types A web browser uses HTTP to communicate with any web servers including the Arduino web server that we used GET and POST are two fundamental methods supported by the HTTP protocol to address server requests coming from a web browser Whenever you are trying to open a website in your browser or any other HTTP client you are actually requesting the GET function from the web server for example when you open a website URL http www example com you are requesting that the web server that hosts this website serves you the GET request for the location In the Handling URLs section you learned how to associate the web py classes with URL landing locations Using the GET method provided by the web py library you can associate the GET request with individual classes Once you have captured the GET request you need to return appropriate values as the response to the client The following code snippet shows how the GET function will be called when anyone makes a GET request to the location def GET self f self submit_form f validates t 76 return render test f t The PosT function of the HTTP protocol is mainly used to submit a form or any other data to the web server In most cases POST is embedded in a web page and a request
82. products 9026 readboard fk https www sparkfun com products 9567 Jar a030 umidiy sensor https www sparkfun com products 9569 1 1 1 1 Mini photocell po https www sparkfun com products 9088 Pr motionsensor ho https www sparkfun com products 8630 Super flux RGB LED common o http www adafruit com product 314 anode wer fk http www adafruit com products 160 Push button switch https www sparkfun com products 97 USB cable for Arduino https www sparkfun com products 512 for development stage rduino power supply http www amazon com Arduino 9V 1A Power for deployment stage Adapter dp BOOCP1QLSC feos 220 ohm 1 kilo ohm and 10 kilo ohm Connection wires The hardware components for the control center are as follows ee Ic omponent first stage Quantity tink Raspberry Pi https www sparkfun com products 11546 TFT LCD screen http www amazon com gp product BOOGASHVDU SD card 8 GB https www sparkfun com products 12998 i Fi dongle 1 http www amazon com Edimax EW 7811Un 150Mbps Raspberry 5 Supports dp B003MTTJOY http www amazon com CanaKit Raspberry Supply Adapter Charger dp BOOGF9T3I0 y Raspberry Pi power supply Keyboard mouse USB hub adao Requried for development and debugging stages Defining the project development stages As per the system architecture we have three main units that collaboratively create the remote home monitoring p
83. projects that can be used as blueprints for your future IoT projects The book has been designed in such a way that every successive chapter has increasing complexity in terms of material that is covered and also more practical value The book has three conceptual sections getting started implementing Python features and network connectivity and each section concludes with a practical project that integrates the concepts that you learned in that section The theoretical concepts and exercises covered in the book are meant to give you hands on experience with Python Arduino programming while the projects are designed to teach you hardware prototyping methodologies for your future projects However you will still need extensive expertise in each domain to develop a commercial product In the end I hope to provide you with sufficient knowledge to jump start your journey in this novel domain of the IoT What this book covers Chapter 1 Getting Started with Python and Arduino introduces the fundamentals of the Arduino and Python platforms It also provides comprehensive installation and configuration steps to set up the necessary software tools Chapter 2 Working with the Firmata Protocol and the pySerial Library discusses the interfacing of the Arduino hardware with the Python program by explaining the Firmata protocol and the serial interfacing library Chapter 3 The First Project Motion triggered LEDs provides comprehensive guide
84. rapidly sending random signals Note The randint function takes the randint startValue endValue syntax and returns the random integer between the range established by startvalue and endvalue Connections Like we used in the previous chapter s project we will need a pull up resistor to connect the LED with the Arduino pin As displayed in the following diagram simply connect the anode of the LED longer leg to the digital pin 11 via one 220 ohm resistor and connect the cathode shorter leg to the ground TX HE s rx m Arduino eevee eeeee eevee e t ee oe eee o eeeee eeeee eevee fritzing It is important to note that the digital pin 11 on Arduino Uno is also capable of performing PWM along with digital pins 3 5 6 9 and 10 The Python code The Python code with the title ledBrightnessPwM py for this exercise is located in the code bundle of this book which can be downloaded from https www packtpub com books content support 1961 Open the file to explore the code As you can see in this code template a float value between 0 and 1 0 is randomly selected before passing it to the PWM pin This method generates random LED brightness for a given amount of time This practice can be used to generate random input samples for various other testing projects As you can see the first few lines of the code import the necessary libraries and initialize the board Although the board variable dev cu
85. sensor This measures and provides relative humidity results as an analog output The output of the sensor can be directly connected to any analog pin of Arduino The following image shows the breakout board with the HIH 4030 sensor that is sold by SparkFun Electronics You can learn more about the HIH 4030 sensor from its datasheet which can be obtained from https www sparkfun com datasheets Sensors Weather SEN 09569 HIH 4030 datasheet pdf e Push button switch Push button switches are small switches that can be used on a breadboard When pressed the switch output changes its status to HIGH which is LOW otherwise In the second stage we are going to make the sensor unit mobile by replacing your computer with a Raspberry Pi For that you will need the following components to get started Raspberry Pi po fe s www sparkfun com products 11546 Micro USB cable with a power http www amazon com CanaKit Raspberry Supply Adapter adapter Charger dp BOOGF9T3I0 8 GB SD card https www sparkfun com products 12998 TFT LCD screen mar www amazon com gp product BOOGASHVDU Further explanations of these components are provided later in the chapter Hardware design The entire hardware architecture of the thermostat can be divided into two units a physical world interfacing unit and a computation unit The physical world interfacing unit as its name indicates monitors phenomenon of the physical world
86. server begin In the 1oop function we initialize a client object to listen to incoming client requests using the EthernetClient method This object will respond to any request coming from connected clients that try to access the Ethernet server through port 80 EthernetClient client server available On receiving the request the program will wait for the request payload to end Then it will reply to the client with formatted HTML data using the client print method while client connected if client available char c client read Serial write c Response code If you try to access the Arduino server from the browser you will see that the web server replies to the clients with the analog pin readings Now to obtain the proper values of the humidity and PIR sensors that we connected in the hardware design you will have to perform the following modification to the code You will notice here that we are replying to the clients with the calculated values of relative humidity instead of raw readings from all the analog pins We have also modified the text that will be printed in the web browser to match the proper sensor title if ce An amp amp currentLinelsBlank send a standard http response header client printlin HTTP 1 1 200 OK client println Content Type text html client println Connection close client println Refresh 5 client println client println lt DOCTYPE
87. start your Mosquitto broker after that it won t be able to communicate with the broker So you need to make sure that you start the Mosquitto broker before powering on the monitoring station If you need to restart the Mosquitto broker for any reason remove and restart the monitoring station first pi raspberrypi Deskt File Edit Tabs Help MonitoringStation temperature O 27 Mon tor n tion humdity O 48 Monitor flon motion OC Mon tor tation light O 831 00 donitoringStation led O off Mon tor ngStat on buzzer OFF MonitoringStation buzzer O OFF MonitoringStation buzzer O OFF onito gStation buzzer O OFF Monito gStation buzzer O OFF Mon tor ngStat on buzzer O O YdonitoringStation buzzer O O onitoringStation buzzer 0 O MonitoringStation buzzer onitoringStation buzzer O OFF MonitoringStation temperature O 2 MonitoringStation humidity O MonitoringStation motion O Mon tor ngStat on l ght O 831 00 Mon tor ngStat on led O off Monitorin tion buzzer OFF MonitoringStation buzzer O OFF MonitoringStation buzzer O OFF On execution of the program you will be able to see a small GUI window as shown in the following screenshot This window displays the sensor s values for temperature humidity ambient light and motion Along with these values the GUI also displays the status of the system which is Normal in this screenshot You can also observe that every time the control center gets updates from the mon
88. step It is important not to modify anything in the code as the test software that we are going to use complies with the latest unchanged firmware 3 Once the StandardFirmata sketch is opened the next step is to compile it for your Arduino board In the previous section we already connected the Arduino board to the computer and selected the proper serial port However if the new sketchbook has a different configuration than that follow the steps from the previous section that is select the appropriate serial port and the Arduino board type 4 To compile the current sketch click on the Verify icon from the toolbar as displayed in the following screenshot You can also compile it by navigating to Sketch Verify Compile or clicking on Ctrl R command R if you are using Mac OS X StandardFirmata Arduino 1 0 5 StandardFirmata Firmata is a generic protocol for communicating with microcontrollers from software on a host computer It is intended to work with any host computer software package To download a host software package please clink on the following Link to open the download page in your default browser http firmata org wiki Download The compilation process should complete without any errors as we are using default example code from the IDE itself Now it s time to upload the sketch to the board Make sure that you have connected the board 5 Press the upload icon in the toolbar as displayed in the followi
89. such as temperature humidity and ambient light using sensors connected to the Arduino board The physical world interfacing unit is interchangeably mentioned as the thermostat sensor unit throughout the chapter The computational unit is responsible for displaying the sensor information via the GUI and plots The following diagram shows the hardware components for the first stage where the thermostat sensor unit is connected to a computer using the USB port In the thermostat sensor unit various sensor components are connected to the Arduino board using I2C analog and digital pins Temperature Light serial Computer Thermostat Sensor Unit Thermostat Computation Unit In the second programming stage where we are going make our thermostat into a mobile and deployable unit you will be using a single board computer Raspberry Pi as the computational device In this stage we will use a miniature thin film transistor liquid crystal display TFT LCD screen that is connected to a Raspberry Pi via general purpose input output GPIO pins and is used as a display unit to replace the traditional monitor or laptop screen The following diagram shows this new thermostat computational unit which truly reduces the overall size of the thermostat and makes it portable and mobile Circuit connections for the Arduino board are unchanged for this stage and we will use the same hardware without any major modifications TFT LCD Scre
90. sudo easy_install pip New terms and important words are shown in bold Words that you see on the screen for example in menus or dialog boxes appear in the text like this In the System window click on the Advanced system settings in the left navigation bar to open a window called System Properties Note Warnings or important notes appear in a box like this Tip Tips and tricks appear like this Reader feedback Feedback from our readers is always welcome Let us know what you think about this book what you liked or disliked Reader feedback is important for us as it helps us develop titles that you will really get the most out of To send us general feedback simply e mail lt feedback packtpub com gt and mention the book s title in the subject of your message If there is a topic that you have expertise in and you are interested in either writing or contributing to a book see our author guide at www packtpub com authors Customer support Now that you are the proud owner of a Packt book we have a number of things to help you to get the most from your purchase Downloading the example code You can download the example code files from your account at http www packtpub com for all the Packt Publishing books you have purchased If you purchased this book elsewhere you can visit http www packtpub com support and register to have the files e mailed directly to you Downloading the color images of this book
91. sudo pip install paho_mqtt In the previous chapter we developed a web application based on web py that utilizes the paho_mqtt library to support the MQTT protocol As with the first project we are going to deploy the same web application on the EC2 based virtual instance to demonstrate your custom IoT cloud platform As a dependency of this project you first need the web py Python library which you can install using the following command sudo pip install web py Now you have all the necessary software packages to run the IoT application To make your web application accessible via the Internet you need to configure the security of you virtual instance Configuring the security of the virtual instance First we will configure the virtual instance to securely host the Mosquitto broker Later we will go through the methods to set up basic security to prevent the abuse of your Mosquitto server by automated bots or spamming attempts To change any parameters on your virtual instance you will have to use the Security Groups tools from the Network amp Security section of your AWS Management Console page Open the Security Groups section as displayed in the following screenshot NETWORK 4 SECURITY Elastic IPs Placement Groups Load Balancers Key Pairs Network Interfaces AUTO SCALIN Launch Configurations Auto Scaling Groups Each virtual instance has a default security group that is generated automatically
92. t have a provision to automatically publish data when it is updated with a new value In order to overcome this limitation Xively implements the concept of triggers which provide additional functionality beyond just publishing data when it is changed Through this you can basically create a trigger for any channel to perform the POST operation on the specified location when conditions that are set for that trigger get satisfied by the incoming data For example you can set a trigger on the Humidity channel to send you a notification when the value of humidity changes that is increases above or decrease below a given threshold You can create a trigger in your Xively platform account by just clicking on the Add Trigger button as displayed in the following screenshot Triggers Add Trigger While creating a trigger you can specify the channel you want to monitor and the condition to trigger a notification on the specified HTTP PosT URL As shown in the following screenshot complete the information for Channel Condition and HTTP POST URL before saving the trigger The major drawback with this approach is that Xively requires an actual URL to send the POST notification If your current computer doesn t have a static IP address or a DNS address the trigger won t be able to send you the notification Add Trigger Channel Humidity Condition HTTP POST URL http example com 8080 Y Save Trigger Cancel
93. testing of the project architecture Before we jump to the hardware design process of this project let s get ourselves familiar with the helpful tools Introducing Fritzing a hardware prototyping software You are not required to design the hardware system for this project By and large in this book the hardware system designs will be provided as the primary focus of the book is on programming rather than hardware design If you are interested in system design or rapid prototyping of the hardware components the open source software tool used for this purpose is called Fritzing The schematics for your projects can be designed using Fritzing and it can be obtained from http fritzing org download Fritzing is a community supported electronic design automation software initiative for designers artists and hobbyists It lets you convert your hardware sketch from paper to software as a Circuit diagram Fritzing also provides you with a tool to create PCB layouts from your designs Fritzing extensively supports Arduino and other popular open source DIY hardware platforms You can explore Fritzing via built in example projects Install and run Fritzing The following screenshot shows one of the default projects that are displayed after opening Fritzing Blink fzz READ ONLY Fritzing Breadboard View BIETET jm A LIe Comm folta 0 2 ne aj y 9 o on pin 13 M ORCE Ea INSPECTOR 216 1707 m 0 0
94. that generates the data Publisher and the node that consumes the data Subscriber We are going to use MQTT as the protocol that uses the pub sub model of message transportation Let s begin by covering the pub sub architecture and MQTT in detail MQTT A lightweight messaging protocol Just like REST pub sub is one of the most popular messaging patterns mostly deployed to transfer short messages between nodes Instead of deploying client server based architecture the pub sub paradigm implements messaging middleware called a broker to receive queue and relay messages between the subscriber and publisher clients subscribe lt topic gt Subscriber publish lt topic data gt notify lt data gt Publisher Subscriber architecture The pub sub architecture utilizes a topic based system to select and process messages where each message is labeled with a specific topic name Instead of sending a message directly to the subscriber the publisher sends it first to the broker with a topic name In a totally independent process the subscriber registers its subscription for particular topics with the broker In the event of receiving a message from the publisher the broker performs topic based filtering on that message before forwarding it to the subscribers registered for that topic As publishers are loosely coupled to subscribers in this architecture the publishers do not need to know the whereabouts of the subscrib
95. the Arduino board To use the Ethernet library in your Arduino program the first step you have to take is to import it in to your Arduino sketch include lt Ethernet h gt The Ethernet library implements various functionalities through specific classes which are described as follows Tip We are going to describe only the important methods provided by these classes You can obtain more information regarding this library and its classes from http arduino cc en Reference Ethernet The Ethernet class The Ethernet class is a core class of the Ethernet library and it provides methods to initialize this library and the network settings This is an essential class for any program that wants to use the Ethernet library to establish connections through the Ethernet Shield The primary information required to establish this connection is the MAC address of the device You ll need to create a variable that has the MAC address as an array of 6 bytes as described here byte mac OxDE OxAD OXBE OxEF OXFE OXED The Ethernet library supports the Dynamic Host Control Protocol DHCP which is responsible for dynamically assigning IP addresses to new network nodes If your home network is configured to support DHCP you can establish the Ethernet connection using the begin mac method from the Ethernet class Ethernet begin mac Keep in mind that when you are initializing an Ethernet connection using this class you are only in
96. the MQTT protocol As you can see in the architectural sketch of the system we have Arduino with the Ethernet Shield connected to our home network while the computer is running the Mosquitto broker and the Python applications on the same network We are using the same sensors that is a motion sensor and a humidity sensor and the same hardware design that we used in the previous exercises in this chapter Sensors Arduino Computer Ethernet browser Ethernet Router System Architecture In the software architecture we have the Arduino code that interfaces with the humidity and motion sensors using analog pin 0 and digital pin 3 respectively Using the PubSubClient library the Arduino publishes sensor information to the Mosquitto broker On the MQTT Gateway we have two different Python programs running on the computer The first program uses the paho mqtt library to subscribe and retrieve sensor information from the Mosquitto broker and then post it to the web application The second Python program which is based on web py implements the web applications while obtaining sensor values from the first Python program This program provides a user interface front for the MQTT Gateway Although both of the preceding Python programs can be part of a single application we are delegating the tasks of communicating with Mosquitto and serving information using the web application to separate applications fo
97. the input pin to start reporting This method needs to be utilized before performing a reading operation on the pin board analog 3 enable_reporting Once the reading operation is complete the pin can be set to disable reporting board analog 3 disable_reporting In the preceding example we assumed that you had already set up the Arduino board and configured the mode of the analog pin 3 as INPUT The pyFirmata library also provides the Iterator class to read and handle data over the serial port While working with analog pins we recommend that you start an iterator thread in the main loop to update the pin value to the latest one If the iterator method is not used the buffered data might overflow your serial port This class is defined in the util module of the pyFirmata package and needs to be imported before it is utilized in the code from pyfirmata import Arduino util Setting up the Arduino board port COM3 board Arduino port sleep 5 Start Iterator to avoid serial overflow it util Iterator board it start Manual operations As we have configured the Arduino pins to suitable modes and their reporting characteristic we can start monitoring them The pyFirmata library provides the write and read methods for the configured pins The write method The write method is used to write a value to the pin If the pin s mode is set to OUTPUT the value parameter is a Boolean that is 0 or 1 b
98. the pub sub messaging paradigm the implementation of MQTT on your hardware application provides support for one to many distributed messaging eliminating the limitation of unidirectional communication demonstrated by HTTP REST As MQTT is agnostic of the content of the payload there is no restriction on the type of message you can pass using this protocol Due to all the benefits associated with the pub sub paradigm and its implementation in the MQTT protocol we will be using the MQTT protocol for the rest of the exercises to have messages communicated between Arduino and its networked computer To achieve this we will be using the MQTT broker to provide the ground work for message communication and host topics while deploying the MQTT publisher and subscriber clients at the Arduino and Python ends Mosquitto an open source MQTT broker As we described MQTT is just a protocol standard and it still requires software tools so that it can be implemented in actual applications Mosquitto is an open source implementation of the message broker which supports the latest version of the MQTT protocol standard The Mosquitto broker enables the pub sub paradigm implemented by the MQTT protocol while providing a lightweight mechanism to enable messaging between machines Development of Mosquitto is supported through community efforts Mosquitto is one of the most popular MQTT implementations freely available and widely supported on the Internet Yo
99. the updated sensor value generated by this code sample to the web py server if client connect 10 0 0 20 8080 Serial printin connected client println POST data HTTP 1 1 client println Host 10 0 0 20 client println Content Type application x www form urlencoded client println Connection close client print Content Length client println data length client println client print data client println Serial println Data sent Once you have performed the changes compile and upload this sketch to the Arduino board As the web py server is yet not implemented the POST request that originated from Arduino will not be able to reach its destination successfully so let s create the web py server to accept POST requests The HTTP server using web py to handle the POST request In this implementation of the POST method we require two web py classes index and data to individually serve requests from the web browser and Arduino respectively As we are going to use two separate classes to update common sensor values that is humidity and temperature we are going to declare them as global variables global temperature humidity temperature 25 As you may have noticed in the Arduino code client println POST data HTTP 1 1 we were sending the POST request to the URL located at data Similarly we will use the default root location to land any request coming from the web brow
100. this case char xivelyKey lt Your API key gt char ledId LED The xively Arduino library requires you to define the xivelyDatastream variable as an array You can also specify multiple data streams according to your application XivelyDatastream datastreams XivelyDatastream ledId strlen ledId DATASTREAM_FLOAT y You also need to declare a variable called feed using the XivelyFeed function As displayed in the following line of code replace the default feed ID with the appropriate one In the initialization of the feed variable the value 1 represents the number of datastreams in the XivelyDatastream array XivelyFeed feed lt Your feed ID gt datastreams 1 In our exercise we want to periodically retrieve the value of the LED channel and turn the actual LED on or off accordingly In the following code snippet we obtain the float value from feed 0 where 0 specifies the data stream located at the 0 position in the datastreams array Serial print LED value is Serial printlin feed 0 getFloat if feed 0 getFloat gt 1 digitalwrite ledPin HIGH else digitalwrite ledPin LOW As you now know that the parameters need to be changed for this exercise open the XivelyLibBasicRetrieveData ino Arduino sketch from the code folder This sketch contains the exact code that you need to use for the exercise Although this sketch includes the necessary modifications you will st
101. this phase is by using CSV files Once you have your Arduino board ready with the appropriate connections use the following code snippet to create a Python file and run it You can also open the csvArduinoStore py file from this chapter s code folder import csv import pyfirmata from time import sleep port dev cu usbmodemfa1331 board pyfirmata Arduino port it pyfirmata util Iterator board it start pirPin board get_pin d 11 i a0 board get_pin a 0 i with open SensorDataStore csv w as f w csv writer f w writerow Number Potentiometer Motion sensor 1 0 pirData pirPin read potData a0 read while i lt 25 sleep 1 if pirData is not None i 1 row i potData pirData w writerow row print Done CSV file is ready board exit While the code is running rotate the knob of the potentiometer and wave your hand in front of the motion sensors This action will help you to generate and measure distinct values from these sensors Meanwhile the program will log this data in the SensorDataStore csv file When complete open the SensorDataStore csv file using any text viewer or spreadsheet program and you will be able to see these sensor values stored in the file Now let s try to understand the program As you can observe from the code we are not utilizing a new module to interface the Arduino board or store sensor values to the file Instead we have utilized the sa
102. to Xively use the tutorials in the following links to get started e The official website https www carriots com e Setting up an account on Carriots https learn adafruit com wireless gardening arduino cc3000 wifi modules setting up your carriots account e The Carriots library for Arduino https github com carriots arduino library e A Carriots example for Arduino https github com carriots arduino examples e Connect Carriots to the Python web application Developing cloud applications using Python and Xively Now you have a basic idea about the available commercial IoT platforms and you can select one according to your comfort level and requirements It will be very difficult to comprehensively explain every cloud platform with practical examples as the objective of this chapter is to make you familiar with integrating the cloud platform with Python and Arduino For this reason we are going to use Xively as the de facto IoT cloud platform for the rest of the integration exercises Now that you know how to create an account on Xively and work with the Xively platform it is time to start interfacing real hardware with the Xively platform In this section we will go through methods to upload and download data from Xively We will combine the Arduino hardware that we built with the Python programs to show you basic methods of communicating with Xively Interfacing Arduino with Xively The first stage to establish communicati
103. to allow access to your instance through the SSH port 22 This security configuration is responsible for letting you access your virtual instance through the SSH client from your computer The Mosquitto broker uses the TCP port number 1883 to establish communication with publishers and subscriber clients To allow incoming access from this Mosquitto port you will have to edit the current inbound rules and add an entry for port 1883 sever za Filter All security groups v A 1 to 2 of 2 Security Groups Name Y Group ID Group Name VPCID Description oe sg 8e07beeb launch wizard 1 vpc ebc8378e launch wizard 1 created 2014 07 28T02 25 31 968 07 sg e3ca7586 default vpc ebcB378e default VPC security group Security Group sg 8e07beeb E oe f m Description inbound Outbound Tags Type i Protocol i Port Range i Source i SSH TCP 22 0 0 0 0 0 Once you click on the Edit button the website will open a pop up window to add new rules and edit the existing rules Click on the Add Rule button to create an additional rule to accommodate the Mosquitto broker Edit inbound rules Type i Protocol i Port Range SSH TCP 22 Add Rule As displayed in the following screenshot enter the TCP port s number as 1883 and complete the other information in the form Once you have completed the form with the given values save the rules and exit the window Edit inbound rules Type i Protocol i Port Range i Source i SSH TCP
104. to the server is generated when a user submits the component carrying the POST function The web py library also provides the POST function which is called when a web client tries to contact the web py server using the POST method In most implementations of the POST function the request includes some kind of data submitted through forms You can retrieve individual form elements using f Celsius value which will give you a value associated with the form element called Celsius Once the POST function has performed the provided actions you can return appropriate information to the client in response to the POST request def POST self f self submit_form f validates c f Celsius value t c 9 0 5 0 32 return render test f t Templates Now you know how to redirect an HTTP request to an appropriate URL and also how to implement methods to respond to these HTTP requests that is GET and POST But what about the web page that needs to be rendered once the request is received To understand the rendering process let s start with creating a folder called templates in the same directory where our web py program is going to be placed This folder will store the templates that will be used to render the web pages when requested You have to specify the location of this template folder in the program using the template render function as displayed in the following line of code render web template render templates
105. trick for you sudo apt get install python matplotlib When prompted to select dependencies click on Yes to install them all You should be able to find the matplotlib package in other popular Linux distributions too Plotting random numbers using matplotlib The matplotlib library provides a collection of basic plotting related functions and methods via the pyplot framework The pyplot framework contains functions for creating figures drawing plots setting up titles setting up axes and many additional plotting methods One of the import functions provided by pyplot is figure This initializes an empty figure canvas that can be selected for your plot or a set of plots fig1 pyplot figure 1 You can similarly create multiple figures by specifying a number as the parameter that is figure 2 If a figure with this number already exists the method activates the existing figure that can then be further used for plotting The matplotlib library provides the plot method to create line charts The plot method takes a list or an array data structure that is made up of integer or floating point numbers as input If two arrays are used as inputs plot utilizes them as values for the x axis and the y axis If only one list or array is provided plot assumes it to be the sequence values for the y axis and uses auto generated incremental values for the x axis pyplot plot x y The third optional parameter that is supported by t
106. using a serial interface Chapter 2 Working with the Firmata Protocol and the pySerial Library In the previous chapter you learned the fundamentals of the Python programming language and the Arduino hardware platform so that you could get started If you are reading this chapter directly without going through the previous chapter it is assumed that you have some level of expertise or working experience with these technologies This chapter describes two important components that are required to bridge Arduino with Python e The Arduino Firmata protocol e Python s serial library called pySerial Although the Firmata protocol is useful to interface Arduino with Python it can also be used as an independent tool to develop a large variety of applications It is time to take your Arduino hardware out and start getting your hands dirty During the course of this chapter you will require an LED a breadboard and a 1 kilo ohm resistor as well as the components that you already used in the previous chapter that is Arduino Uno and a USB cable Note If you are using any other variant of Arduino you can obtain further information about it from http arduino cc en Guide HomePage or the community supported Arduino forum that is located at http forum arduino cc Connecting the Arduino board As mentioned in the previous chapter this book supports all major operating systems and this section will provide you with steps to connect and c
107. web interfaces for remote access plots for data visualization tools for data analysis interfaces for data storage and so on Using any other programming language such as C or Java the development of these features would require a large amount of programming effort due to the distributed and unorganized nature of the supporting tools Thankfully Python has been very successful at providing support for these types of applications for years Python has a number of libraries to support the development of each of the features mentioned here which are available through PyPI These libraries are open source easy to use and widely supported by the community This makes Python a language of choice for IoT applications Additionally Python also has support to create and ship your custom built applications as libraries so that everyone else can also utilize them in their projects This is a helpful feature if you are developing custom protocols APIs or algorithms for your own hardware products When do we use other languages So when should we not use Python for our projects As mentioned earlier Python is a dynamic language that reduces development time but it also makes the execution of your code slower as compared to other static high level languages such as C C and Java These static languages use a compiler to compile the code and create binaries that get executed during runtime thereby increasing the runtime performance When the perfor
108. with the custom temperature value and you will be able to see the web application load the current relative humidity in percentage units Internally when you submitted the form the web application retrieved the current raw humidity value from the HumidityRaw channel executed the relativeHumidity data temperature function uploaded the calculated humidity value to a new channel called Humidity and then displayed that value in the web application e006 localhost 8080 i A 2 C 5 localhost 8080 Receiving and updating data to Xively Enter current temperature value which effects the Humidity Temperature 22 submit Manually entered temperature value is 22 0 Current humidity value from raw humidity data 35 4672147584 If you open your Xively platform page on a web browser you will be able to see a newly created Humidity channel with the current value for relative humidity You can submit multiple values for temperature in the web application to see the results reflected on the graph of the Humidity channel as displayed in the following screenshot Although this exercise demonstrates a single use case this web application can be extended in multiple ways to create complex applications Humidity 35 782487592 74113 a minute ago 47 O 5 ie Edit Delete Triggers custom notifications from Xively The Xively platform primarily deploys services based on the REST protocol which doesn
109. you can see in this screenshot the IP address of the network interface is listed as IPv4 Address in the opened window Local Area Connection Status General Network Connection Details Connection Property Connection specfic DN Description Physical Address DHCP Enabled Pv4 Address Pv4 Subnet Mask Lease Obtained Lease Expires Pv4 Default Gateway Pv4 DHCP Server Pv4 DNS Servers Pv4 WINS Server NetBIOS over Tcpip En Link4tocal IPv6 Address Pv6 Default Gateway 4 Network Connection Details Value home network Intel R PRO 1000 MT Desktop Adap 08 00 27 E9 1F C1 Yes 10 0 0 23 255 255 255 0 Monday September 29 2014 12 33 73 Monday October 06 2014 12 33 40 10 0 0 1 10 0 0 1 75 75 79 75 75 75 76 76 Yes fe80 15ed c44a 389 beb4 12 m You can also obtain the IP address of your computer using the built in ipconfig utility Open the Command Prompt and enter the following command gt ipconfig As you can see in the following screenshot the IP address of your computer is listed under the Ethernet adapter If you are using a wireless connection to connect to your network the Ethernet adapter will be replaced by the wireless Ethernet adapter ES CA Windows system321cmd exe o m G Users lest gt ipconfig Mindows IP Configuration Ethernet adapter Local Area Connection Connection specific DNS Suffix home network Link local IPv6 Address feRAM 15a
110. you are going to learn and implement these approaches for Arduino communication on the Ethernet Developing web applications using Python By implementing the previous program you have enabled networking on Arduino In the preceding example we created an HTTP web server using methods available from the Ethernet library By creating an Arduino web server we made the Arduino resources available on the network Similarly Python also provides extensibility by way of various libraries to create web server interfaces By running the Python based web server on your computer or other devices such as the Raspberry Pi you can avoid using Arduino to host the web server Web applications created using high level languages such as Python can also provide additional capabilities and extensibility compared to Arduino In this section we will use the Python library web py to create a Python web server We will also use this library to create interactive web applications that will enable the transfer of data between an Arduino client and a web browser After you have learned the basics of web py we will interface Arduino with web py using serial ports to make Arduino accessible through the Python web server Then we will upgrade the Arduino communication method from the serial interface to HT TP based messaging Python web framework web py A web server can be developed in Python using various web frameworks such as Django bottle Pylon and web py
111. you encounter an error for exceeding the limit wait for 5 minutes before your access limit gets lifted o Increase the delay between consecutive Xively updates at the control center level threading Timer 120 checkBuzzerFromXively start o Reduce the frequency of published messages at the monitoring station timer setInterval 600000 publishData o You can also combine various Xively channels by formatting data into JSON or XML e Working with the maximum current draw limitation of Arudino o The 5V power pin and digital pin of Arduino can provide a maximum current of 200 mA and 40 mA respectively When running sensors directly from the Arduino board make sure that you do not exceed these limits o Make sure the combined current requirement of all the sensors is less than 200 mA Otherwise the components won t be able to get enough power to run and this will translate into faulty sensor information o You can provide external power to the components that require large amounts of current and control this power mechanism via Arduino itself You will need a transistor that is acting as a switch that can then be controlled using the digital pins of Arduino The tutorial at https learn adafruit com adafruit arduino lesson 13 dc motors transistors shows a similar example for aDC motor e Solve network problems o In some scenarios your monitoring station won t be able to communicate with the control center due to network prob
112. your recently created t2 micro instance in the list To find out more details about your virtual instance select it from the list As soon as you select your instance you will be able to see additional information in the bottom tab This information includes the public DNS private DNS public IP address and so on instance i 2eed8323 Description Status Checks Instance ID Instance state Instance type Private DNS Private IPs Secondary private IPs Public DNS Monitoring Tags i 2eed8323 running t2 micro A 2 MOS Public DNS Public IP Elastic IP Availability zone Security groups Scheduled events us west 2a launch wizard 1 view rules No scheduled events 11 Save this information as you will need it to log in to your instance Now you have successfully created and turned on a virtual cloud instance using Amazon AWS However this instance is running in the Amazon EC2 and you will have to remotely authenticate into this instance to access its resources Logging into your virtual instance In reality your virtual instance is a virtual computer on a cloud with computation resources that are similar to your regular computer You now need to log in to the running virtual instance to access files run scripts and install additional packages To establish a secure authentication and access procedure you need to use the Secure Shell SSH protocol and there are multiple ways to use SSH
113. 0 pValues append float row 1 if row 2 True mValues append 1 else mValues append 0 pyplot subplot 2 1 1 pyplot plot i pValues pyplot title Line plot header 1 pyplot xlim 1 25 pyplot xlabel X Axis pyplot ylabel Y Axis pyplot subplot 2 1 2 pyplot bar i mValues pyplot title Bar chart header 2 pyplot xlim 1 25 pyplot xlabel X Axis pyplot ylabel Y Axis pyplot tight_layout pyplot show gt In this program we have created two arrays of sensor values pValues and mvalues by reading the SensorDataStore csv file row by row Here pvalues and mValues represent the sensor data for the potentiometer and the motion sensor respectively Once we had these two lists we plotted them using the matplotlib methods The matplotlib library provides various ways to plot different arrays of values You can individually plot them in two different figures using figure that is figure 1 and figure 2 or plot both in a single plot in which they overlay each other The pyplot method also offers a third meaningful alternative by allowing multiple plots in a single figure via the subplot method pyplot subplot 2 1 1 This method is structured as subplot nrows ncols plot_number which creates grids on the figure canvas using row and column numbers that is nrows and ncols respectively This method places the plot on the specific cell that is provided by the plot_numb
114. 1 format e errno e strerror The control center also implements the function to set the system s status across the system once it is calculated using the calculateStatus function There are three different functions to perform this task using a method that is similar to what we described in the previous code snippet These functions include setAlert setCaution and setNormal and these are associated with Alert Caution and Normal respectively While updating the system s status these functions also perform buzzer and LED actions by publishing the LED and buzzer values to the Mosquitto broker def setAlert status window statusValue set status datastreamStatus current_value Alert try datastreamStatus update except HTTPError as e print HTTPError 0 1 format e errno e strerror cli publish MonitoringStation led red cli publish MonitoringStation buzzer ON Checking and updating the buzzer s status In the control center we set the buzzer s status to ON if the system s status is determined as Alert If you look back at the UX flow you will notice that we also want to include a feature for the user to manually turn off the buzzer The checkBuzzerFromXively function keeps track of the buzzer s status from Xively and if the user manually turns off the buzzer using the web application this function sets off the buzzer To continue this process independently from the GUI and situation aw
115. 22 Anywhere gt 0 0 0 0 0 Custom TCP Rule TCP Anywhere Add Rule Now with this configuration port 1883 is accessible by other devices and enables remote communication with the Mosquitto broker You can use the same method to add a rule for port 8080 to allow access to Python s web applications that were developed using web py In future you can add any additional ports to allow access to various services Although it is very easy to change the security rules on your virtual instance make sure that you refrain from opening excessive ports to avoid any security risk Testing your cloud platform In this testing section we will first perform checks for the Mosquitto broker from your computer and then set up authentication parameters for the Mosquitto broker Later we will upload files and folders containing the Python code to our virtual instance using the SSH file transfer protocol Testing the Mosquitto service The first thing that we are going to check on our IoT platform is the accessibility of the Mosquitto broker Open the terminal on your computer and execute the following command after replacing lt Public IP gt with the public IP or public DNS address of your virtual instance mosquitto_pub h lt Public IP gt t test m 3 This command will publish the message value 3 for the test topic for the Mosquitto broker that is specified at the given IP address in our case this is the virtual instance Now open a sep
116. 258035812 Latest received value from Random channel Latest received value from Random channel Latest received value from Random channel Latest received value from Random channel Latest received value from Random channel 50000000 Retrieving data from the web py web interface This is an advanced exercise where we will upload data to one Xively channel after fetching data from another Xively channel and process it by using the data entered via the web form As you know the analog pin on which the HIH 4030 sensor is connected provides you with raw sensor value whereas the relative humidity depends upon the value of the current temperature In this exercise we will develop a web application so that the user can manually enter the temperature value and we will use this to calculate relative humidity from the raw sensor data Before we begin with the details of the code let s first open the uploadwebpyXively py file change the appropriate parameters and execute the file Now in a web browser open the http localhost 8080 location You will be able to see following web application asking you to provide it with the current temperature value Meanwhile upload the XivelyLibAdvance ino sketch to the Arduino board after making the appropriate changes With this program Arduino will start sending raw motion and humidity values to the MotionRaw and HumidityRaw channels In the web application that is running submit the form
117. Arduino IDE comes equipped with a default library called wire This library can be imported to your Arduino sketch by adding the following line of code at the beginning of your program include lt Wire h gt To initialize I2C communication the Wire library uses a combination of the following functions to write data on the slave device Wire beginTransmission 0x48 Wire write 0 Wire endTransmission These slave devices are differentiated using unique part addresses As you can see in the preceding example 0x48 is the part address of a connected slave device The wire library also provides the wire read and Wire requestFrom functions to read and request data from the slave devices These functions are explained in detail in the next section Note You can learn more about the I2C protocol and the wire library from the following links e http www instructables com id I2C between Arduinos e http arduino cc en reference wire Arduino examples for I2C interfacing In order to practice prototyping exercises for the I2C protocol let s utilize two popular I2C sensors that detect temperature and ambient light in the environment As the first step towards understanding I2C messaging we will work with Arduino sketches for I2C interfacing and later we will develop similar functionalities using Python Arduino coding for the TMP102 temperature sensor TMP102 is one of the widely used digital sensors to measure ambient tem
118. As you can see we are also subscribing to the PowerStrip statuscheck channel to deal with the status report if client connect PowerStrip client subscribe PowerStrip fan client subscribe PowerStrip lamp client subscribe PowerStrip toaster client subscribe PowerStrip coffeemaker client subscribe PowerStrip statuscheck In the callback function we use the if statement to match the topic with the appropriate digitalwrite action As you can see we are setting up HIGH and LOW statuses for the digital pin when the program receives on and off messages respectively for that appliance With this action we are also changing the state of the Boolean variable associated with the appliance which will be helpful in retrieving the status of the port The same process is then repeated for all appliances if topicS PowerStrip fan if payloadS equalsIgnoreCase on digitalwrite FAN HIGH fanStatus true if payloadS equalsIgnoreCase off digitalWrite FAN LOW fanStatus false When the system receives a get message that is associated with the status check the program creates a message using the Boolean variables that we toggled earlier The program then publishes the status to the PowerStrip statusreport channel if topicS equals PowerStrip statuscheck if payloadS equalsIgnoreCase get String report if fanStatus report Fan on else repor
119. B power adapter from the Raspberry Pi and locate the GPIO male pins near the RCA video port on the Raspberry Pi Get your TFT screen and connect the GPIO pins as such you can see Raspberry Pi and the screen as displayed in the following image In handful cases the notations on the screen will be misleading and therefore we suggest that you follow the guidelines from the manufacturer to make the connections Once your screen is connected to the Raspberry Pi power it up using the micro USB cable Do not disconnect your HDMI cable yet as your screen is still not ready Before we go ahead with any of the configuration steps let s first connect the Raspberry Pi to the Internet Connect the Ethernet port of the Raspberry Pi to your home or office network using an Ethernet cable Now let s configure the TFT LCD screen in the Raspbian OS to make it work properly Configuring the TFT LCD with the Raspberry Pi OS Once your Raspberry Pi is powered up log in using your username and password Complete the following steps to configure the screen with your Raspberry Pi 1 Download the supporting files and manual using the following command on the terminal wget https s3 amazonaws com tontec 24usingmanual zip 2 Unzip the file The following command will extract the files into the same directory unzip 24usingmanual zip 3 Navigate to the src directory cd cd mztx ext 2 4 src 4 Enter following command to compile the source files
120. Board for prototyping your circui which provides instructions to assemble a circuit using the original breadboards Designing the hardware prototype It s time to collect the hardware components mentioned earlier and start building the system The next figure shows the circuit for the project that has been developed using Fritzing If you have prior experience of working with circuit assembly go ahead and connect the components as displayed in the figure If this is your first experience of working with sensors and the breadboard use the following steps to complete the circuit assembly 1 Connect VCC 5V and ground from the Arduino to the breadboard 2 Connect the anode long lead of the red LED to digital pin 12 of the Arduino board Connect the cathode short lead of the red LED to ground with 220 ohm resistors 3 Connect the anode long lead of the green LED to digital pin 13 of the Arduino board Connect the cathode short lead of the green LED to ground with 220 ohm resistors 4 Connect VDD of the PIR sensor to VCC on the breadboard Use the same wire color to represent the same category of connections This will greatly help in troubleshooting the circuit 5 Connect the signal middle pin of the PIR sensor to Arduino digital pin 7 with a 10 kilo ohm pull up resistor The majority of experts prefer a schematic diagram instead of the prototype diagram that we used previously Schematic diagrams are useful wh
121. H1750 h gt BH1750 lightMeter void setup Serial begin 9600 lightMeter begin Serial println Running void loop uint16_t lux lightMeter readLightLevel Serial print Light Serial print lux Serial println 1x delay 1000 As you can see from the preceding code snippet we have imported the BH1750 library by including BH1750 h file with wire h This library provides the readLightLevel function which will fetch the ambient light value from the sensor and provide it as an integer As the Arduino code runs in a loop with a delay of 1000 milliseconds the lux values will be fetched from the sensor and sent to the serial port every second You can observe these values in the Serial Monitor window PyMata for quick I2C prototyping We have been using pyFirmata as our default Python library to interface the Firmata protocol The pyFirmata library is a very useful Python library to get started with the Firmata protocol as it provides many simple and effective methods to define the Firmata ports and their roles Due to these reasons we extensively used pyFirmata for rapid prototyping in the previous section Although pyFirmata supports analog digital PWM and SERVO modes with easy to use methods it provides limited support to the I2C protocol In this section we are going to use a different Python Firmata library called PyMata to get familiar with Python based prototyping of I2C sensors The PyMat
122. HTML gt client println lt html gt float sensorReading getHumidity analogChannel temperature client print Relative Humidity from HIH4030 is client print sensorReading client printin lt br gt client printin lt html gt break In this process we also added an Arduino function getHumidity that will calculate the relative humidity from the values observed from the analog pins We have already used a similar function to calculate relative humidity in one of the previous projects float getHumidity int analogChannel float temperature float supplyVolt 5 0 int HIH4030_Value analogRead analogChannel float analogReading HIH4030_Value 1023 0 supplyVolt float sensorReading 161 0 analogReading supplyVolt 25 8 float humidityReading sensorReading 1 0546 0 0026 temperature return humidityReading You can implement these changes to the WebServer Arduino example for the testing phase or just open the webServer_Custom ino sketch from the Exercise 1 Web Server folder of your code directory As you can see in the opened sketch file we have already modified the code to reflect the changes but you will still have to change the MAC and IP addresses to the appropriate addresses Once you are done with these minor changes compile and upload the sketch to Arduino If everything goes as planned you should be able to access the web server using your web browser Open the IP a
123. I key gt define FEEDID lt Your feed 1D gt define USERAGENT lt Your project name gt 4 In the Arduino sketch you will also have to change the MAC address and the IP address of your Ethernet Shield You should be familiar with obtaining these addresses from the exercise that you performed in the previous chapter Use these values and modify the following lines of code appropriately byte mac 0x90 OxA2 OxDA 0Ox0D Ox3F 0x62 IPAddress ip 10 0 0 75 5 Asthe opened Arduino example was created for the Pachube you need to update the server address to api xively com as specified in the following code snippet Comment the IP address line as we will not need it anymore and add the server parameter IPAddress server 216 52 233 122 char server api xively com 6 In the sendData function change the channel name to HumidityRaw as we have our HIH 4030 humidity sensor connected to the analog port We are not performing any relative humidity calculations at this stage and are going to upload just the raw data from the sensor here s the actual content of the PUT request client print HumidityRaw client printin thisData Once you have performed these changes open the xivelyClientBasic ino file from the folder containing codes for this chapter Compare them with your current sketch and compile upload the sketch to the Arduino board if everything seems satisfactory Once you have uploaded the code o
124. IEEE 802 family of standards the IEEE 802 3 standard describes different types of wired connectivity between nodes in a local area network also called Ethernet Similarly Wireless LAN also referred to as Wi Fi is part of the IEEE 802 11 standard where a communication channel uses wireless frequency bands to exchange data Most network nodes deployed with IEEE 802 standards that is Ethernet Wi Fi and so on have a unique identifier assigned to the network interface hardware called a media access control MAC address This address is assigned by the manufacturer and is mostly fixed for each network interface While using Arduino for network connectivity we will need the MAC address to enable networking A MAC address is a 48 bit address and in human friendly form it contains six groups of two hexadecimal digits For example 01 23 45 67 89 ab is the human readable form of a 48 bit MAC address While the MAC address is associated with the hardware level that is physical protocols the Internet Protocol IP is a communication protocol that is widely used at the Internet level to enable internetworking between networked nodes In the implementation of version 4 of the IP protocol suite IPv4 each network node is assigned a 32 bit number called the IP address for example 192 168 0 1 When you connect a computer phone or any other device to your local home network an IP address is assigned to that device by your router One of th
125. LCD screen with the Raspberry Pi in Chapter 7 The Midterm Project a Portable DIY Thermostat Please refer to those tutorials in case you haven t completed those exercises yet Assuming that you have configured the Mosquitto broker and the required Python libraries you can move on to the next section which includes the actual Python programming The Python code for the control center Before you start interfacing these libraries in the Python code start your Mosquitto broker first from the command line using this simple command mosquitto Make sure that you restart your monitoring station every time you start or restart the Mosquitto broker This action will make sure that your monitoring station is connected to the Mosquitto broker since the process of establishing the connection only gets executed once in our Arduino code that is at the beginning of the setup process The Python code for the current project is located in the code folder of this chapter with the name controlCenter py Open this file using your Python IDE and modify the values of the appropriate parameters before executing it These parameters include the IP address of the Mosquitto broker along with the feed ID and the API key of the Xively virtual device You should already have the feed ID and the API key of your Xively virtual device from the previous chapter cli connect 10 0 0 18 1883 15 FEED_ID lt feed id gt API_KEY lt api key If you are us
126. MotionPin motionC dtostrf motion 5 2 message_buff2 client publish Arduino motion motionC Complete any other modification you want to implement and then compile your code If your code is compiled successfully you can upload it to your Arduino board If your Mosquitto is running you will be able see that a new client is connected as Arduino which is the client name you specified in the preceding Arduino code Developing the MQTT Gateway using Mosquitto You can have the Mosquitto broker running on the same computer as the Mosquitto Gateway or on any other node in your local network For this exercise let s run it on the same computer Open the program file named mosquittoGateway py for this stage from the Step2_Gateway_mosquitto folder which is inside the Exercise 4 MQTT gateway folder The first stage of the Gateway application includes the paho mqtt based Python program which subscribes to the Mosquitto broker for the Arduino humidity and Arduino motion topics cli subscribe Arduino humidity 0 cli subscribe Arduino motion 0 When this MQTT subscriber program receives a message from the broker it calls the onMessage function as we ve already described in the previous coding exercise This method then identifies the appropriate sensor type and sends the data to the web py program using the POST method We are using the default Python library httplib to implement the PosT method in this program
127. ON gs ern paa O A TEISI AO Jan Source http arduino cc en uploads Main ArduinoEthernetShield R3 Front j Every Ethernet Shield board is equipped with a unique hardware MAC address You can see it on the back of the board You may want to note down this hardware address as it will be required frequently in the upcoming exercises Also make sure that you get familiar with mounting the Arduino Ethernet Shield for those exercises Buy an Arduino Ethernet Shield module from SparkFun or Amazon before your start working on any exercises You can obtain additional information about this Shield at http arduino cc en Main ArduinoEthernetShield Arduino WiFi Shield The Arduino WiFi Shield has a layout similar to that of the Arduino Ethernet Shield as far as mounting on top of the Arduino board is concerned Instead of the Ethernet RJ45 connector the WiFi Shield contains components to enable wireless networking Using the WiFi Shield you can connect to the IEEE 802 11 Wi Fi wireless networks which is one of the most popular ways of connecting computers to the home network nowadays Source http arduino cc en uploads Main A000058_front jpg The Arduino WiFi Shield requires additional power through a USB connector It also contains a microSD slot to save files Just like the Ethernet Shield you can view the MAC address on the back of the board More information about the Arduino WiFi Shield can be
128. P GET client on Arduino while using an HTTP server that was developed using web py The premise of this programming exercise is to use the Ethernet Shield extension and the Ethernet library to develop a physical Arduino HTTP client that supports the GET request The Arduino code to generate the GET request The Arduino IDE ships with a few basic examples that utilize the Ethernet library One of these examples is WebClient which can be found by navigating to File Examples Ethernet WebClient It is designed to demonstrate the GET request by implementing the HTTP client on Arduino Open this sketch in the Arduino IDE as we are going to use this sketch and modify it to accommodate the Arduino hardware we created The first thing you need to change in the opened sketch is the IP address and the MAC address of your Arduino Ethernet Shield Replace the following variables with the variables appropriate for your system The following code snippet shows the IP address and the MAC address for our hardware and you need to change it to accommodate yours byte mac 0x90 OxA2 OxDA 0x00 0x47 0x28 IPAddress ip 10 0 0 75 As you can see the example uses Google as a server to get a response You need to change this address to reflect the IP address of your computer which will host the web py server char server 10 0 0 20 In the setup function you will have to change the server IP address again Also change the default HTTP
129. Python Use the Setuptools or pip to install the library using the following command We are assuming that you already have the latest paho_mqtt library installed on your computer sudo pip install python twitter The Python code for this section is located in the code folder with the PythonTweetAPowerStrip py filename Open the code in your IDE and start exploring it The code contains two parallel threads to handle the tweets and the Mosquitto library separately As you can see in the following code snippet we are using the Api class from the python twitter library to establish a connection with the Twitter API We are using the consumer key consumer secret access token key and access token secret values for this authentication Once the authentication is established the Api class can be used to get the latest status from the timeline using the GetHomeTimeline function call and to post the new status using the PostUpdate function call The GetHomeTimeline function gives an array of statuses from the user we need the latest status which can be fetched using statuses 0 the first element of the array api twitter Api consumer_key lt consumer key gt consumer_secret lt consumer secret gt access_token_key lt access token key gt access_token_secret access token secret gt Once we have retrieved the latest tweet we need to make sure that we haven t used that tweet already So we save the latest tweet ID in a
130. SB Modem Apply to activate it tails OK e Thund ther ithi i A IP Address e Fitbit B Station Q Subnet Mask Router Bluetooth PAN J DNS Server Search Domains Advanced Assist me Revert Apply For OS X Lion or later versions on connecting the Arduino board a dialog box will appear that will ask you to add a new network interface In this case you will not have to navigate to your network preferences If you see the network interface with the status Not connected and highlighted in red don t worry about it as it should work just fine Open the Arduino IDE and navigate to Serial Port from the Tools menu You should be able to see options similar to those displayed in the following screenshot The serial port on which the Arduino board is connected might vary according to your OS X version and the physical port to which it is connected Make sure that you select a tty interface for a USB modem As displayed in the following screenshot the Arduino board is connected to the serial port dev tty usbmodemfd121 Board Serial Port Programmer Burn Bootloader dev tty Bluetooth Incoming Port dev cu Bluetooth Incoming Port dev tty Bluetooth Modem dev cu Bluetooth Modem iv dev tty usbmodemfd1211 dev cu usbmodemfd1211 Windows The configuration of the Arduino serial port is very straightforward if you are using Windows When you connect your Arduino board the very first time the o
131. SB power supply Optionally you can use a micro USB based phone charger to supply power to the Raspberry Pi e A display cable If you have an HDMI monitor or a TV you can use an HDMI cable to connect it to your Raspberry Pi If you want to use your VGA or DVI based monitor you will need a VGA to HDMI or DVI to HDMI adapter converter You can buy these adapter converters from Amazon or Best Buy e An SD card You are required to have at least an 8 GB SD card to get started It is preferable to use an SD card that has a quality of class 4 or better You can also buy an SD card with the preinstalled OS at http swag raspberrypi org collections frontpage products noobs 8gb sd card Note The Raspberry Pi Model B requires a microSD card instead of a regular SD card e A mouse and keyboard You will need a standard USB keyboard and a USB mouse to work with the Raspberry Pi e AUSB hub optional Since the Model B has just two USB ports you will have to remove existing devices from the USB ports to make space for another device if you want to connect a Wi Fi adapter or memory stick to it A USB hub can be handy to attach multiple peripheral components to your Raspberry Pi We recommend that you use a USB hub with external power supply as the Raspberry Pi can drive a limited number of peripheral devices through the USB ports due to power limitations Preparing an SD card To install and configure software components such as Python and the requir
132. SFE_BMP180 Preferences Ctrie Comma EEPROM Quit Ctri Q Esplora Ethernet Let s start with a simple in built example Open the Blink example by navigating to File Examples 01 Basics Blink The IDE will open a new window containing code that is similar to the code in the following program Blink Turns on an LED on for one second then off for one second repeatedly This example code is in the public domain Pin 13 has an LED connected on most Arduino boards give it a name int led 13 the setup routine runs once when you press reset void setup initialize the digital pin as an output pinMode led OUTPUT the loop routine runs over and over again forever void loop digitalwrite led HIGH turn the LED on HIGH is the voltage level delay 1000 wait for a second digitalwrite led LOW turn the LED off by making the voltage LOW delay 1000 wait for a second This Arduino sketch is designed to blink an LED on digital pin 13 You must be wondering why we didn t discuss or ask you to bring any hardware That s because the Arduino Uno board is equipped with an on board LED that is connected to digital pin 13 Now instead of diving deeper into the Arduino code we are going to focus on the process of dealing with the Arduino board through the IDE Compiling and uploading sketches Once you have your code opened in the IDE the first thing you need to do is to sel
133. T client open the Serial Monitor window in your Arduino IDE You will be able to see the periodic publication of the sensor information as displayed in this screenshot 600 dev cu usbmodemfa1331 Publishing data Arduino humidity 41 35 Arduino motion 0 09 Dota pbulished Publishing data Arduino humidity 18 63 Arduino motion 0 09 Data pbulished v Y Autoscroll No line ending HJ 9600 baud HA Now open a web browser on your computer and go to the URL of your web application You should be able to see a window that looks like what is shown in the following screenshot You can click on the Refresh button to check out the updated sensor values 600 T30 0 0 0 8080 x io 7 gt D 0 0 0 0 8080 O04 Get sensor information from mosquitto Refresh humidity and motion values by pressing button Refresh Humidity 17 84 Motion 0 00 Note We have set a delay of 5 seconds between successive sensor updates Henceforth you won t be able to see the updated values if you rapidly press the Refresh button On the Gateway program terminal you will be able to see the label of the topic every time the program receives a new message from Mosquitto If the delay between successive sensor updates is not sufficient and httplib doesn t have enough time to get the response back from the web py application the program will generate an error message with the httplib function Although we require an
134. The coding milestone for the first stage can be further distributed as follows e Develop the Arduino sketch to interface sensors and buttons while providing output of the sensor data to the Python program via the serial port e Develop the Python code to obtain sensor data from the serial port using the pySerial library and display the data using GUI that is designed in Tkinter e Create a plot to demonstrate the real time humidity readings using the matplotlib library In the second stage we will attach the Arduino hardware to a single board computer and a miniature display to make it mobile and deployable The milestone to achieve objective of the second stage are as follows e Install and configure a single board computer Raspberry Pi to run the Python code from the first stage e Interface and configure the miniature screen with the Raspberry Pi e Optimize the GUI and plot window to adjust to this small screen s resolution In the following subsection of this section you will be notified about the list of required components for both the stages followed by the hardware circuit design and the software flow design The programming exercises for these stages are explained in the next two sections of the chapter The list of required components Instead of going through the process of identifying the required components we have already selected the components for this project based on their utilization in the previous exercises ease o
135. Tkinter Label top text TempUnitLabel grid column 3 row 1 HumdUnitLabel Tkinter Label top text HumdUnitLabel grid column 3 row 2 LighUnitLabel Tkinter Label top text 1x LighUnitLabel grid colum 3 row 3 Once you initialize the code and before you click on the Start button you will be able to see the following window The observation labels are populated without any values at this stage De Temperature Humidity Light x Start Exit Once the Start button is clicked the program will engage the thermostat sensor unit and start reading the sensor values from the serial port Using the lines that are obtained from the serial port the program will populate the observation labels with the obtained values The following code snippet updates the temperature values in the observation label and also updates the temperature unit TempLabel config text cleanText reading 1 TempUnitLabel config text C TempUnitLabel update_idletasks In the program we are using similar methods for humidity and ambient light to update their labels respectively As you can see in the following screenshot the GUI now has the values for the temperature humidity and ambient light readings OSE Temperature 27 06 C Humidity 14 72 Light 25 kx it ex La _ The Start and Exit buttons are programmed to call the onStartButtonPress and onExitButtonPress functions when they are
136. WS platform account setting up Setting up an account on AWS analog digital buzzer o URL Buzzer generating sound alarm pattern architecture IoT web applications o o o o about Architecture of loT web applications physical layer Architecture of loT web applications computation layer Architecture of IoT web applications interfacing layer Architecture of IoT web applications Arduino o O O O 0 0 0 o about Introduction to Arduino history History objectives Why Arduino variants Arduino variants Uno board The Arduino Uno board URL for installation on Linux Linux interfacing with Python Prototyping computer networking Arduino and the computer networking Arduino interfacing with Xively o O O O about Interfacing Arduino with Xively Arduino data uploading Uploading Arduino data to Xively data downloading to Arduino Downloading data to Arduino from Xively advanced code for data upload and download Advanced code to upload and download data using Arduino Arduino board o o StandardFirmata sketch uploading Uploading a Firmata sketch to the Arduino board setting up pyFirmata methods used Setting up the Arduino board Arduino board connection establishing Connecting the Arduino board establishing on Linux Linux establishing on Mac OS X Mac OS X establishing on Windows Windows troubleshooting Troubleshooting Arduino code
137. While using the httplib library you have to use the HTTPConnection method to connect to the web application running on port number 8080 Note Although this program requires that your web application second stage must run in parallel we are going to implement this web application in the upcoming section Make sure that you first run the web application from the next section before executing this program otherwise you will end up with errors The implementation of this library requires that you first import the library into your program Being a built in library http1ib does not require an additional setup process import httplib Once the connection is established with the web application you have to prepare the data that needs to be sent in the POST method The httplib method uses the request method on the opened connection to post the data You can also use the same method in other applications to implement the GET function Once you are done with sending the data you can close the connection using the close method In the current implementation of the httplib library we are creating and closing the connection on each message You can also declare the connection outside the onMessage function and close it when you terminate the program def onMessage mosq obj msg print msg topic connection httplib HTTPConnection 10 0 0 20 8080 if msg topic Arduino motion data motion msg payload connection requ
138. a library supports regular Firmata methods and also provides full support for the I2C messaging protocol PyMata can be easily installed using Setuptools which we used in the previous chapters to install other Python libraries We are assuming that you already have Setuptools and pip on your computer Let s start performing the following steps 1 To install PyMata on a Windows computer execute the following command in the command prompt C gt easy_install exe pymata 2 If you are using Linux or Mac OS X use the following command in the terminal to install the PyMata library sudo pip install pymata 3 If everything is set up properly this process will complete without any error You can confirm PyMata by opening Python s interactive prompt and importing PyMata gt gt gt import PyMata 4 If the execution of the preceding command fails you need to check the installation process for any error Resolve the error and repeat the installation process Interfacing TMP102 using PyMata In order to utilize PyMata functionalities you will need your Arduino board to be equipped with the standard firmata firmware just like the pyFirmata library Before we proceed to explain the PyMata functions let s first run the following code snippet Connect your TMP102 temperature sensor as explained in the previous section Using the Arduino IDE navigate to File Examples Firmata and upload the standard Firmata sketch from there to your A
139. a means of communication between the Arduino Uno and the control center and we will be utilizing the Arduino Ethernet Shield for this purpose Let s discuss the hardware architecture of the monitoring station and its components Designing the monitoring station We already designed units based on Arduino and the Ethernet Shield in various exercises in Chapter 8 Introduction to Arduino Networking and Chapter 9 Arduino and the Internet of Things Therefore we have assumed that you are familiar with interfacing the Ethernet Shield with the Arduino board We will connect various sensors and actuators with the Arduino board as displayed in the following diagram As you can see in this diagram the sensors will provide the data to the Arduino board while the actuators will seek the data from the Arduino board Although we are automatically collecting environment data for these sensors the data from the button will be collected from manual user inputs Sensor TMP102 Humidity HIH 4030 Publish Arduino Ethemet Shield To Control Ambient Light fat Center Motion PIR sensor Sensors ev 1 Subscribe Buzzer RGB LED Actuators Monitoring Station Check out the following Fritzing diagram for the detailed connections in the monitoring station As you can see in our hardware design the temperature sensor TMP102 is connected through the I2C interface which means that we will need the SDA and SCL lines We will be
140. aced using a set of relays and switches You can upgrade the current sensors at the monitoring station with more powerful efficient and accurate sensors However the monitoring station with the upgraded sensors may require a more powerful version of Arduino with more VO pins and computation capabilities You can also use additional sensors other than those used in this project at the monitoring station There are large amount of heterogeneous Arduino supported DIY sensors that you can buy off the shelf Examples of these sensors include the Alcohol Gas Sensor MQ 3 LPG Gas Sensor MQ 6 Carbon Monoxide Sensor MQ 7 Methane Gas Sensor MQ 4 and so on These sensors can be simply interfaced with the Arduino just like the other sensors that we connected earlier To accommodate these changes you will be required to change the control center logic and algorithms If you are interfacing a third party component you may also have to revisit the system architecture and adjust it Similarly you will also have to run frequent updates to Xively for the additional number of sensors making the free version inadequate To resolve this you can pay for the commercial version of a Xively account or use a limited number of requests using a JSON file format similar to the one displayed in the following code snippet version 1 0 0 datastreams id example current_value 333 ig key current_value value ty
141. al components of the program that are derived from the project requirements According to the goals that we have defined for the thermostat project the software flow can be demonstrated in the following diagram get temperature humidity ambient light via Arduino receive data using serial port is new data available Yes is temperature No flag high Yes set temperature unit to Celsius set temperature unit to Fahrenheit Display GUI using Tkinter is plot flag high close any plot window if open display humidity plot In the implementation the software flow of the project begins by measuring the temperature humidity and ambient light from Arduino and printing them on a serial port line by line The Python program obtains the sensor data from Arduino via the serial port before presenting the data on the screen Meanwhile the Python program keeps looking for a new line of data A user can interact with the thermostat using a push button which will let the user change the unit for the temperature data Once the button is pressed the flag gets changed to HIGH and the temperature unit is changed to Celsius from its default unit Fahrenheit If the button is pressed again the opposite process will happen and the unit will be changed back to its default value Similarly another user interaction point is the second push button that allows a user to open a plot for real time
142. all system The control center calculates the status of the system as Alert Caution or Normal using the current values of temperature and humidity To calculate the status the control center executes the calculateStatus function every time it gets an update for the temperature or humidity from the monitoring station According to the current situation awareness logic if the temperature is measured above 45 degree Celsius or below 5 degree Celsius we call the system s status as Alert Similarly you can identify the range of temperature and humidity values for Caution and Normal statuses from the following code snippet def calculateStatus if tempG gt 45 if humdG gt 80 status High Temperature High Humidity elif humdG lt 20 status High Temperature Low Humidity else status High Temperature setAlert status elif tempG lt 5 if humdG gt 80 status Low Temperature High Humidity elif humdG lt 20 status Low Temperature Low Humidity else status Low Temperature setAlert status else if humdG gt 80 status High Humidity setCaution status elif humdG lt 20 status Low Humidity setCaution status else status Normal setNormal status Communicating with Xively The control center is also required to communicate with Xively when it receives a message from the subscribed topics We are already familiar with the process of setting up virtual
143. ame method that was described earlier Select the appropriate serial port on which your Arduino is connected and make a note of it As you can see in the sketch this simple Arduino code transmits the status of digital pin 2 that is on the serial port with a baud rate of 9600 bps 3 Without disconnecting the Arduino board from your computer open the Python interpreter Then execute the following commands on the Python interpreter Make sure that you replace dev ttyACmo with the port name that you noted down earlier gt gt gt import serial gt gt gt s serial Serial dev ttyACMO 9600 gt gt gt while True print s readline 4 On execution you should get repeated values in the Python interpreter Press Ctrl C to terminate this code As you can see the Arduino code will keep sending messages due to the loop function that was used in the sketch We don t have anything connected to pin 2 and because of this we are getting the status 0 that is Low 5 If you know what you are doing you can connect any digital sensor to pin 2 and run the script again to see the changed status In the preceding Python script the serial Serial method interfaces and opens the specified serial port while the readline method reads each line from this interface terminated with n that is the newline character Note The newline character is a special character that signifies the end of a line of text It is also known as End of
144. an Arduino sketch for minor modifications If you look at the various applications of this project you will notice that only a few of them require the project to be implemented as a standalone system that just detects motion and blinks LEDs This type of system can be easily implemented by a simple Arduino sketch The project setup Before we go ahead with the project make sure that you have the following things in place e The hardware components are set up and are functioning correctly e Your Arduino is connected to the computer using a USB cable e Your computer has the Arduino IDE and you can access the connected Arduino board through the IDE The Arduino sketch This section describes the Arduino code for the project Before we get into a step by step description of the code let s first follow these steps to run the project 1 Open the Arduino IDE 2 From the File menu open a new sketchbook 3 Copy the following Arduino code to the sketch and save it int pirPin 7 Pin number for PIR sensor int redLedPin 12 Pin number for Red LED int greenLedPin 13 Pin number for Green LED void setup Serial begin 9600 pinMode pirPin INPUT pinMode redLedPin OUTPUT pinMode greenLedPin OUTPUT void loop int pirVal digitalRead pirPin if pirVal LOW was motion detected blinkLED greenLedPin No motion detected else blinkLED redLedPin Motion detected Function which blinks
145. an be seen in the preceding figure As you can see in the next figure we have converted the overall system into three main architectural units e Monitoring station e Control center e Cloud service In this figure we have addressed each and every major component that we are going to utilize in the project along with their association to each other In the following sections we are going to define these three main units briefly The comprehensive description and implementation steps for these units are provided later in the chapter under separate sections Control Center Monitoring Station Sensors Arduino Raspberry Pi User interaction points Components interacting with physical world Cloud Service Computation units Web Application Xively Amazon AWS Virtual Instance The monitoring station We need a resource constrained and robust unit that will communicate with the physical environment periodically This monitoring unit can be built using Arduino since low level microcontroller programming can provide uninterrupted stream of sensor data The usage of Arduino at this stage will also help us to avoid the direct interfacing of basic low level sensors with computers that are running on complex operating systems The sensors and the actuators are connected to Arduino using digital analog PWM and I2C interfaces The control center The control center behaves as the main user interaction point
146. arate terminal window and execute the following command to subscribe to the test topic on our broker mosquitto_sub h lt Public IP gt t test On the execution of this command you will be able to see the latest value that is published for this topic Use the mosquitto_pub command to post multiple messages and you can see the output of these messages in the other terminal window that is running the mosquitto_sub command Configuring and testing basic security As you saw in the previous example the publishing and subscribing commands just used the IP address to send and receive data without using any authentication parameters This is a major security loophole as anyone on the Internet can send data to your Mosquitto broker To avoid unauthorized access to your broker you have to establish authentication credentials You can specify these parameters by following these steps in the given order 1 If you have not already logged into your instance through SSH open a terminal window and log in using SSH Once you are logged in navigate to the Mosquitto directory and create a new file called passwd using the following set of commands We will use this file to store the usernames and passwords cd etc mosquitto sudo nano passwd 2 In the file enter the username and password information separated by using the colon operator For testing purposes we will use the following credentials which can be changed any time once you are m
147. ard PCB It has range of up to 20 feet 6 meters which is sufficient for the project The following image displays the PIR sensor available on the SparkFun website Image courtesy Sparkfun Inc Source Sparkfun Inc e LEDs We recommend that you use green and red LEDs for the project If they are unavailable you can use any two LEDs with different colors e Wires resistors and the breadboard You will require a bunch of wires and a breadboard to complete the connections As a best practice have at least three different colors of wire connectors to represent power ground and signal You will also need two 220 ohm and one 10 kilo ohm pull resistors e The Arduino board The Arduino Uno board is sufficient for the project requirements You can also use Arduino Mega or any other Arduino board for this project The project requires only three I O pins and any available Arduino board is equipped with more than three I O pins e A USB cable You will need a USB cable to upload the Arduino code and perform serial communication with the Arduino board e A computer We have already configured a computer with Python and the Arduino IDE for your favorite operating system in the previous chapters You will need this computer for the project Make sure that you have all the software components that we installed and configured in the previous chapters The software flow design The first step before jumping to work on any hardware s
148. are set up as described in the system design Connected the Arduino to your computer using a USB cable Uploaded the StandardFirmata sketch back to Arduino Made sure that you have Python and the Python packages pySerial and pyFirmata installed on your computer Obtained a text editor to write Python codes Working with Python executable files In the previous chapters we explored Python programming using the interactive Python interpreter However when working with large projects it is very difficult to keep using the Python interactive interpreter for repetitive tasks Like other programming languages the preferred method is to create Python executable files and run them from the terminal Python executable files carry the py extension and are formatted as plain text Any text editor can be used to create these files The popular editors used to create and edit Python files are Notepad nano vi and so on This list also includes the default editor that is shipped with the Python setup files called IDLE You can use the editor of your choice but make sure that you save the files with the py extension Let s copy the following lines of code in a new file and save it as test py usr bin python a Python b Programming print a b To run this file execute the following command on the terminal where the test py file is saved python test py You should be able to see the text Python Programming printed on the t
149. are to create the wiring diagram before we perform the actual physical wiring There are multiple ways to communicate with the Arduino board from the host computer using Firmata such as writing your own program in Python using the supported library or using the prebuilt testing software Starting from the next section we are going to write our own programs to use Firmata but at this stage let s use a freely available tool for testing purposes The official Firmata website http www firmata org also provides test tools that you can download from the Firmata Test Program section on the main page The website includes a different variant of the tool called firmata_test for different operating systems Using the following steps you can test the implementation of the Firmata protocol 1 Download the appropriate version of the firmata_test program to your computer 2 Now connect your Arduino board with the LED to the host computer using the USB cable and run the downloaded firmata_test program You will be able to see an empty window on the successful execution of the program 3 As displayed in the following screenshot select the appropriate port from the drop down menu Make sure to select the same port that you used to upload the Arduino sketch amp Firmata Test_File LH Window Help 600 Firmata none dev cu Bluetooth Incoming Port dev cu Bluetooth Modem v dev cu usbmodemfd1211 F Tip At this point ma
150. areness threads we will need to create another thread for this function The timer on this thread will automatically execute the function every 30 seconds def checkBuzzerFromXively try datastreamBuzzer feed datastreams get Buzzer buzzerValue datastreamBuzzer current_value buzzerValue str buzzerValue cli publish MonitoringStation buzzer buzzerValue except HTTPError as e print HTTPError 0 1 format e errno e strerror print Requested channel doesn t exist threading Timer 30 checkBuzzerFromXively start With this function running in a separate thread every 30 seconds the control center will check the status of the Xively channel and stop the buzzer if the status is set to OFF We will explain how the user can update the Xively channel for the buzzer in the next section Testing the control center with the monitoring station Assuming your Mosquitto broker is running execute the controlCenter py code with the changed parameters Then start the monitoring station After a few moments you will see on the terminal that the control center has already started getting messages from the publishers that are initialized on the monitoring station The update interval for the messages from the publisher at the control center depends upon the configured publishing interval at the monitoring station Note The Arduino code executes the process of connecting to the Mosquitto broker only once after powering on If you
151. atform that contains the Mosquitto broker and the Python project can be extended to accommodate additional features protocols and extra security Installing the necessary packages on AWS Using the SSH protocol and the key pair log into your virtual instance Once you are at the Command Prompt the first task that you need to perform is to update all the outdated packages in Ubuntu the operating system of your virtual instance Successively execute the following commands sudo apt get update sudo apt get upgrade Ubuntu already comes with the latest version of Python However you will still need to install Setuptools to install the additional Python packages sudo apt get install python setuptools Ubuntu s package repository also hosts Mosquitto and it can be directly installed using the following command With this command we will install the Mosquitto broker Mosquitto client and all other dependencies together During the installation you will be asked to confirm the installation of additional packages Enter Yes at the terminal and proceed with the installation sudo apt get install mosquitto Now you have installed the Mosquitto broker on your virtual instance and you can run it by executing the Mosquitto command To develop Python based Mosquitto applications we need the Python Mosquitto library on our instance Let s install the library using Setuptools through the following commands sudo easy_install pip
152. b client To check this out open your first web py program webPyBasicExample py and change the return string from Hello world to test We are performing this string change to differentiate it from the other instances of this program Execute the Python program from the terminal and open the Serial Monitor window in the Arduino IDE again This time you will be able to see that your Arduino client is receiving a response for the GET request it sent to the web py server As you can see in the following screenshot you will be able to see the test string printed in the Serial Monitor window which is returned by the web py server for the GET request 600 dev cu usbmodemfa1331 coconnecting connected HTTP 1 1 288 OK Transfer Encoding chunked Connection close Date Wed 24 Sep 2014 10 02 15 GMT Server localhost A disconnecting v M Autoscroll No line ending HJ 9600 baud B Although in this example we are returning a simple string for the GET request you can extend this method to obtain different user specified parameters from the web server This GET implementation can be used in a large number of applications where Arduino requires repeated input from the user or other programs But what if the web server requires input from the Arduino In that case we will have to use the POST request Let s develop an Arduino program to accommodate the HTTP PosT request Working with the POST request from Arduino Sinc
153. be applied to projects in which external manual control to a system is required The potentiometer output that translates to the analog input of Arduino can be used to control an actuator such as a motor or an LED In some cases the input can also be used to control the flow of the program by applying its values to a variable Connections Connect the output of the potentiometer to analog pin AO as shown in the following diagram Complete the circuit by connecting Vref and the ground terminals of the potentiometers to 5V and the ground of the Arduino board respectively IGIT DIG H U A Oo1080 vo oo oo oo ee vr E E E E E E E E E E E E E E eee TX ME 3 r Arduino The Python code Assuming that you already have the StandardFirmata firmware uploaded to the Arduino board you are required to run a Python code on your computer to complete its interfacing with the potentiometer A Python code template with the name potentiometer py to help you get started with this example is located in the code bundle of this book which can be downloaded from https www packtpub com books content support 1961 Let s open this file to understand the program As you can see we are using the pyFirmata library with other Python modules such as time and os from pyfirmata import Arduino util from time import sleep import os In the second step of the program we are initializing the Arduino board and star
154. between the sensor information and the user It is also responsible for conveying the sensor information from the monitoring station to the cloud services The control center can be developed using your regular computer or a single board computer such as a Raspberry Pi We are going to utilize a Raspberry Pi since it can be easily deployed as a hardware unit and it is also capable enough at hosting Python programs We will replace a computer screen with a small TFT LCD screen for the Raspberry Pi to display the GUI The cloud services The main purpose of the cloud services is to provide an Internet based interface for the control center so that the user can access it remotely Before we host a web application to perform this operation we will need an intermediate data relay This sensor data relay works as a host between the cloud based web application and the control center In this project we will be using Xively as the platform to collect this sensor data The web application can be hosted on an Internet server in our case we are going to use Amazon AWS due to our familiarity with it Defining UX flow Now although we know what the architecture of the overall system looks like we haven t defined how the user is going to interact with it This process of designing user interaction for our system will also help us to figure out data flow between major components Let s begin with the components that are operating locally at your house that
155. between these monitoring stations updating data models for Xively updates and so on e The free Xively account may not be able to handle the large amounts of data coming from the monitoring stations In this case you can either optimize the update rate and or payload size or upgrade your Xively account to comply with the requirements You can also resort to other free services such as ThingSpeak Dweet io and Carriots but you will have to make substantial modifications to the existing code structure e You can also update the web application to provide you with a selection menu for the monitoring stations or display all of them at once You will also have to change the code to yield the modified data models Extending sensory capabilities In term of sensors we are only interfacing temperature humidity ambient light and motion sensors However the actuation is limited to the buzzer and LED You can implement the following changes to improve the sensory capabilities of the project In a real scenario a remote home monitoring system should be able to interface with other existing sensors such as the security system monitoring cameras refrigerator sensors door sensors and garage sensors throughout a home You can also interface this project with other appliances such as the air conditioner heater and security alarm which can help you to control the environment that you are already monitoring As a trial these components can be interf
156. blish MonitoringStation temperature temperatureC float humidity getHumidity celsius humidityC dtostrf humidity 5 2 message_buff2 client publish MonitoringStation humidity humidityC int motion digitalRead MotionPin motionC dtostrf motion 5 2 message_buff2 client publish MonitoringStation motion motionC int light analogRead LightPin lightC dtostrf light 5 2 message_buff2 client publish MonitoringStation light lightC If you check out the setup function you will notice that we have used a library called SimpleTimer to set up a timer method for this function This method executes the publishData function periodically without interrupting and blocking the actual flow of the Arduino execution cycle In the following code snippet the number 300000 represents the time delay in milliseconds that is 5 minutes timer setInterval 300000 publishData Note You will need to download and import the SimpleTimer library to compile and run the code successfully You can download the library from https github com infomaniac50 SimpleTimer Subscribing to actuator actions You can see in the setup function that we are initializing the code by subscribing to the MonitoringStation led and MonitoringStation buzzer channels The client subscribe method will make sure that whenever the Mosquitto broker gets any updates for these channels the Arduino based monitoring system gets notified
157. browsers the file gets saved to the Download folder 3 Run the following command in the terminal to build and set up Setuptools sudo python ez_setup py If you are familiar with Homebrew based software installation just follow these quick steps to install Setuptools 1 First install wget from Homebrew if you don t have it already brew install wget 2 Once you have installed wget run the following command in the terminal wget https bitbucket org pypa setuptools raw bootstrap ez_setup py 0 python Note More information regarding the Homebrew utility can be obtained from http brew sh You can install Homebrew on your Mac by running the following simple script in the terminal ruby e curl fsSL https raw githubusercontent com Homebrew install master install Installing pip As you have successfully installed Setuptools let s use it to install pip For Linux or Mac OS X you can run the following command in the terminal to install pip sudo easy_install pip For Windows open the command prompt and execute the following command gt easy_install exe pip If you have already installed pip on your computer please make sure that you upgrade it to the latest version to overcome the few bugs that are associated with the upgrade You can upgrade pip using the following command at the terminal sudo easy_install upgrade pip Since you have already used easy_install to install a Python package
158. cant bit LSB o about Arduino coding for the TMP102 temperature sensor LED o brightness controlling with PWM LED controlling LED brightness using PWM connections Connections o Python code The Python code libraries Arduino IDE o about Working with libraries o URL Working with libraries Line feed Carriage Return LF CR o about Playing with a pySerial example Linux o Python installing Linux o Setuptools installing Linux o Arduino IDE installing Linux o Arduino board connection establishing Linux o IP address obtaining Linux Listbox widget o about The Checkbutton widget selecting LEDs o URL The Checkbutton widget selecting LEDs local area network LAN o about Networking fundamentals localhost IP address o about Networking fundamentals loop function o about The loop function o using The loop function M Mac OS X o Python installing Mac OS X Setuptools installing Mac OS X Arduino IDE installing Mac OS X Arduino board connection establishing Mac OS X matplotlib configuring Configuring matplotlib on Mac OS X SD card preparing Preparing an SD card o IP address obtaining Mac OS X matplotlib o about Getting started with matplotlib URL Getting started with matplotlib Configuring matplotlib on Windows configuring on Windows Configuring matplotlib on Windows configuring on Mac OS X Configuring matplotlib on Mac OS X upgra
159. cation to support REST requests Open the webPyEthernetGETPOST py file from the Exercise 3 RESTful application Arduino and webpy code folder As you can see the web py based web server implements two separate classes index and data to support the REST architecture for the web browser and the Arduino client respectively We are introducing a new concept for the Form element called Dropdown Using this Form method you can implement the drop down selection menu and ask the user to select one option from the list of options form Dropdown dropdown Humidity Humidity Motion Motion form Button submit type submit description submit In the previous web py program we implemented the GET and POST methods for the index class and only the POST method for the data class Moving forward in this exercise we ll also add the GET method to the data class This method returns the value of the sensorType variable when the GET request is made for the data location From the user side the value of the sensorType variable is updated when the form gets submitted with an option This action sends a selected value to the POST method of the index class ultimately updating the sensorType value class data def GET self return sensorType def POST self global humidity motion i web input data web data data data split 1 if sensorType Humidity humidity relativeHumidity data temperature return humi
160. ce necessary packages installing on AWS Installing the necessary packages on AWS virtual instance security configuring Configuring the security of the virtual instance testing Testing your cloud platform Mosquitto service testing Testing the Mosquitto service basic security configuring Configuring and testing basic security basic security testing Configuring and testing basic security project uploading on instance Uploading and testing a project on the instance project testing on instance Uploading and testing a project on the instance e loT cloud platforms o o o o Xively The IoT cloud platforms Xively a cloud platform for the loT 2lemetry The IoT cloud platforms Carriots The loT cloud platforms Carriots ThingSpeak The IoT cloud platforms ThingSpeak e IoT projects o design methodology The design methodology for loT projects e oT web applications o architecture Architecture of loT web applications e IP address about Networking fundamentals obtaining Obtaining the IP address of your computer obtaining for Windows Windows obtaining for Mac OS X Mac OS X obtaining for Linux Linux e IPAddress class Oo about The IPAddress class Label widget o about Learning Tkinter for GUI design The Label widget The LabelQ widget monitoring I O pins o used for monitoring I O pins The Label widget monitoring I O pins least signifi
161. cess on Xively com open https xively com signup in a web browser 2 On the sign up page you will be prompted to select the username and the password as displayed in the following screenshot Username Email Password 3 On the next page you will be asked to enter some additional information that includes your full name organization s name country zip code time zone and so on Fill out the form appropriately and click on the Sign Up button What describes you best Pick one Full Name Organization Country United States ZIP Code Postcode Time zone GMT 00 00 UTC Areas of interest Commercial Government Personal Education Communication Settings Xively may contact me directly Y Sign Up Terms of Use 4 Xively will send an activation e mail to the e mail account that you specified in the form Open the e mail and click on the activation link Check your spam folder if you don t see the e mail in your inbox 5 Once you click on the activation link you will be redirected to the welcome page on Xively s website We advise you to go through the tutorials provided on the welcome page as it will help you to get familiar with the Xively platform 6 After completing the tutorials you can come back to the main user screen from the page using the https xively com login link If you are not already logged in you will require your e mail address as the username and an a
162. changes are not applied Summary At the end of this chapter and hence the end of the contextual part of the book you should be able to develop your own Internet of Things projects In this chapter we used a commercial IoT cloud platform to handle your sensor data We also deployed a cloud instance to host open source IoT tools and created our own version of the customized IoT cloud platform Certainly the content that you learned is not sufficient to develop scalable and fully stacked commercial products but it is really helpful to get you started with them In a large number of cases this material is sufficient to develop DIY projects and product prototypes that will ultimately lead you to the final product In the next two chapters we will put the material that we learned to the test and develop two complete IoT hardware projects We are also going to learn a project development methodology that is specific to hardware based IoT products which can be applied to convert your prototypes into real products Chapter 10 The Final Project a Remote Home Monitoring System It is now time to combine every topic that we learned in the previous chapters into a project that combines Arduino programming Python GUI development MQTT messaging protocol and a Python based cloud application As you might have already figured out from the chapter title we are going to develop a remote home monitoring system using these components The first secti
163. clicked by the user The onStartButtonPress function executes the code necessary to create the user interface while the onExitButtonPress function closes all the opened windows disconnects the thermostat sensor unit and exits the code StartButton Tkinter Button top text Start command onStartButtonPress StartButton grid column 1 row 4 ExitButton Tkinter Button top text Exit command onExitButtonPress ExitButton grid column 2 row 4 You can play with the Start and Exit buttons to explore the Python code To observe the changes in the sensor readings try to blow air or place an obstacle over the thermostat sensor unit If the program doesn t behave appropriately check the terminal for error messages Plotting percentage humidity using matplotlib We will use the matplotlib library to plot the relative humidity values in real time We will plot the relative humidity values in this project as the range of the data is fixed between 0 and 100 percent Using a similar method you can also plot temperature and ambient light sensor values While developing the code to plot temperature and ambient light sensor data make sure that you are using appropriate ranges to cover the sensor data in the same plot Now as we have specified in the onStartButtonPress function a window similar to the following screenshot will pop up once you press the push button for the plot Humidity The following code snippet is responsib
164. cloud computing platform One of the original and most popular services offered by AWS is its Elastic Computer Cloud EC2 service The EC2 service lets a user create instances of a virtual machine with different combinations of computation power and operating systems from their large cloud infrastructure It is also really easy to change the computational properties of these virtual instances at any time making them highly scalable When you are trying to create your own IoT platform using EC2 this scalability feature greatly helps you as you can expand or compress the size of your instances according to demand If you are not familiar with the concept of cloud computing or AWS as a particular product you can learn more about them from http aws amazon com The EC2 cloud platform is different from Xively as it provides general purpose cloud instances virtual machines with computation power and storage that can be converted to any feature specific platform by installing and configuring platform specific software It is important to note that you really do not have to be an expert in cloud computing to further advance in this chapter The upcoming sections provide an intuitive guide to perform basic tasks such as setting up an account creating and configuring your virtual machines and installing software tools to create loT platforms Setting up an account on AWS Amazon provides one year of free access to the basic instance of the cloud based vi
165. clude statement at the beginning of the sketch that is include lt Wire h gt The Arduino IDE also provides the capability to add an external library that supports a specific hardware or provides additional features In the upcoming chapters we will be dealing with some of these external libraries and we will go through the process of importing them at that time You can learn more about built in Arduino libraries from http arduino cc en Reference Libraries Using Arduino examples The Arduino IDE contains a large number of built in example sketches These examples are designed to get the user familiar with basic Arduino concepts and built in Arduino libraries The examples are well maintained by the Arduino community since they have comprehensive support for each example through the Arduino website http arduino cc en Tutorial HomePage In the Arduino IDE you can access these examples by navigating to File Examples as shown in the following screenshot fo sketch_decl4a Arduino 1 0 5 01 Basics AnalogReadSerial File Edit Sketch Tools Help 02 Digital BareMinimum New Ctrl N 03 Analog Blink Open Ctri O 04 Communication DigitalReadSerial Sketchbook 05 Control Fade Examples 06 Sensors ReadAnalogVoltage Close Ctrl W 07 Display Save Ctri S 08 Strings Save As Ctrl Shift S 09 USB Upload Ctri U 10 StarterKit Upload Using Programmer Ctrl Shift U ArduinolSP Page Setup Ctri Shift P BH1750 Print Ctri P PubSubClient
166. code that we developed in the previous exercise The goal of this exercise is to send data to the LED channel using a web application while observing the LED s behavior on the Arduino hardware You can find the Python program for this exercise in this chapter s folder with the name uploadwebpyXively py As you can see in the code we are using the web py forms to obtain two inputs Channel and Value We will use these inputs to modify the current value of the LED channel submit_form form Form form Textbox Channel description Channel form Textbox Value description Value form Button submit type submit description submit The template file base html is also modified to accommodate minor changes that are required by this exercise As you can see in the opened Python file we are using the same code that we used to interface with Xively in the previous exercise The only major modification is done to the datastream update method which is now placed in the POST function This method will be executed when you submit the form Once you change the API key and feed ID in this file execute the Python code and open http localhost 8080 in your web browser You can see the web application running as displayed in the following screenshot Enter the value as displayed in the figure to turn on the LED on the Arduino board You can change the Value parameter to 0 to turn off the LED A os FA
167. code to reflect the pin that you have selected eve o o o r A niie er a E E so e gt DIGIT eeeeveeseeseeeeeeeeeeeeeeeeeeeee eeeeeeeeeeeeeeeeeeeeeeeeeee RUNGEN oe Fe Hoe oe 8888 o 88088 8886 fritzing The Python code In the code example two different sound patterns are generated using arrays of time delays To perform these actions we are going to implement a custom Python function that will take the pin number the recurrence time and the pattern number as input Before we jump to explain the code let s open the program file buzzerPattern py from the code folder In the beginning of the code you can find the Python function buzzerPattern that will be called from the main program with appropriate options As this function is the core of the entire program let s try to understand it The function contains two hardcoded pattern arrays pattern1 and pattern2 Each contains the on and off time for the buzzer for a second which is the duty cycle of the pattern For example in pattern1 0 8 represents the time the buzzer needs to be on and 0 2 represents the opposite The function will repeat this buzzer pattern for recurrence times that is specified by the function argument Once the for loop with the value of recurrence is started the function will check for the pattern number from the function argument and execute the pattern We are using the flag va
168. continue and pass that can be used while a loop is being executed using the compound statements mentioned earlier You can learn more about these Python features from https docs python org 2 tutorial controlflow html Built in functions Python supports a number of useful built in functions that do not require any external libraries to be imported We have described a few of these functions as a collection of a respective category according to their functionalities Conversions Conversion methods such as int float and str can convert other data types into integer float or string data types respectively gt gt gt a a gt gt gt int a base 16 10 gt gt gt i 1 gt gt gt str i 3 Similarly list set and tuple can be used to convert one data structure into another Math operations Python also supports built in mathematical functions that can find the minimum and or maximum values from a list Check out the following examples and play around with the different data structures to understand these methods gt gt gt list 1 12 2 2 34 4 78 gt gt gt min list 1 12 gt gt gt max list 4 78 The pow x y function returns the value of x to the power of y gt gt gt pow 3 14159 2 9 869587728099999 String operations Python provides easy access to string manipulation through built in functions that are optimized for performance Let s take a look at the following
169. control center where the appropriate actions for the control center will remain the same as in the previous scenario However in the web application the user has to load the web browser every time to request the data which was happening automatically at the control center Take a look at the following figure to understand the UX flow for the web application User Web Application Open Web Application in browser Read Xively Channels Observe status amp sensor outputs on LCD TFT screen Display current system status Bo SHA sensor outputs is system on alert Y Press button switch on Monitoring station Click button on GUI Set Xively Buzzer channel status The list of required components The necessary components for the project are derived using three main criteria e Ease of availability e Compatibility with the Arduino board e Familiarity with the components due to previous utilization in this book This is the list of the components that you will need to start working on the project If you have completed the previous exercises and projects you should already have most of the components If you don t want to disassemble the projects you can obtain them from the websites of SparkFun Adafruit or Amazon whose links are provide in the next table The hardware components for the monitoring station are as follows aunosnemasnid fho https www sparkfun com
170. ction o loop function The loop function o pinMode function The pinMode function functions pins o digitalWrite function Working with pins digitalRead function Working with pins analogRead function Working with pins analog Write function Working with pins O O O 0 0 O O Oo G e general purpose input output GPIO pins o about Hardware design e graphical user interfaces GUIs o e Grid o about Why we use Python about The Pack geometry manager e Grid geometry manager o about The Grid geometry manager e GUI thermostat o o designing Designing the GUI and plot in Python pySerial used for streaming sensor data Using pySerial to stream sensor data in your Python program designing Tkinter used Designing the GUI using Tkinter percentage humidity plotting with matplotlib Plotting percentage humidity using matplotlib button interrupts using Using button interrupts to control the parameters button interrupts used for changing temperature unit Changing the temperature unit by pressing a button button interrupts used for swapping between GUI and plot Swapping between the GUI and the plot by pressing a button hardware components Raspberry Pi o Raspberry Pi What do you need to begin using the Raspberry Pi power cable What do you need to begin using the Raspberry Pi display cable What do you need to begin using the Raspberry Pi SD card
171. curity configuration mosquitto pub u user P password h lt Public Ip gt t test m 3 9 Also check your Mosquitto subscriber using the following command mosquitto_sub u user P password h lt Public Ip gt t test Uploading and testing a project on the instance As we discussed in the previous chapters you can always use your computer for development purposes Once you are ready for deployment you can utilize this newly configured virtual instance as the deployment unit You can copy your files from your local computer to the virtual instance using a utility called PuTTY https docs aws amazon com AWSEC2 latest UserGuide putty html or using the SCP SSH copy command Now it is time to upload the project files from the final coding exercise of the previous chapter which implemented the MQTT protocol using Python and the Mosquitto library As a reminder the final exercise is located in the folder named Exercise 4 MQTT gateway of the previous chapter s code repository We will be using the SCP utility to upload these files to your virtual instance Before we use this utility let s first create a directory on your virtual instance Log in to your virtual instance and go to the user directory of the virtual instance by using the following command ssh i lt key name gt pem ubuntu lt public ip gt cd Using the character tilde with the cd command will change the current directory to the home directory unles
172. d which is now part of the thermostat sensor unit to your computer Select the appropriate board and port names in the Arduino IDE and verify the code Upload the code to your Arduino board and open the Serial Monitor window once the code is successfully uploaded You should be able to see text similar to that displayed in the following screenshot Humidity 3 16 Flag 0 Light 1x 30 Temperature F 78 0 Humidity 3 16 Flag 0 Light 1x 30 Temperature F 78 Humidity 3 17 37 Flag 0 Light 1x 30 Temperature F 78 Humidity 3 16 7 Flag 0 Light 1x 30 Y Autoscroll No line ending 9600 baud The Arduino code structure and basic declarations are already explained in various sections throughout the book Instead of explaining the entire code line by line we will focus here on the main components of the software flow that we described earlier Interfacing the temperature sensor In the Arduino sketch the temperature data is obtained from the TMP102 sensor using the getTemperature function The function implements the wire library on the 12C address of TMP102 to read the sensor data This is then converted into proper temperature values float getTemperature Wire requestFrom tmp102Address 2 byte MSB Wire read byte LSB Wire read it s a 12bit int using two s compliment for negative int TemperatureSum MSB lt lt 8 LSB gt gt 4 float celsius TemperatureSum 0 0625 r
173. d between the integer value of 0 and 1023 to represent the voltage from OV to 5V value analogRead 0 analogwrite This function is used to provide analog output results at a digital pin The technique is called PWM and this will be explained in Chapter 4 Diving into Python Arduino Prototyping It is still important to note that this function is not designed for all digital pins but it is only for pins that are designated as PWM pins Statements If you are familiar with any other object oriented programming language you must have used statements extensively for your programs The Arduino language uses traditional C C statements such as if else while switch case and for to control the flow of your program Instead of diving deep into these statements right now they are described later in the book with practical examples Summary Alright You have successfully completed the comparatively mundane tasks of installing and configuring Python and the Arduino IDE Your system whether it is a Mac OS X Linux or Windows system is now ready for the upcoming chapters In this chapter we went through the history and building blocks of Arduino We also learned the basics of Python programming and the Arduino language Now you are ready to get your hands on real hardware and start exploring computer to hardware interfacing In the next chapter we will go through the first step of interfacing that is connecting Arduino to the computer
174. d c44a 389 beb412 ERA RAS A TREU Oe Subnet Mask o 255 255 255 Default Gateway e o 18 8 8 1 Tunnel adapter isatap hone network Media State 2 Media disconnected Connection specific DNS Suffix home network Tunnel adapter Local Area Connection 9 Connection specific DNS Suffix IPv6 Address 2 2 2881 8 9438 6abd 2438 1cfe f5ff ffe Link local IPv6 Address fe8B0 2438 1cfe f5ff ffe8 11 Default Gateway oo ss 2 35 Mac OS X If you are using Mac OS X you can obtain the IP address from the network settings Open System Preferences and click on the Network icon You will see a window similar to what is shown in the next screenshot In the left sidebar click on the interface you are looking to obtain the IP address of a0 Network Show All Location Automatic Ethernet N Connected N Status Connected Ethernet is currently active and has the IP USB Modem 2 address 192 168 110 130 e Built i Port 1 Q Configure IPv4 Using DHCP nd y Built i Port 2 Qu IP Address 192 168 110 130 a Subnet Mask 255 255 255 0 Bluetooth PAN J Router 192 168 110 2 DNS Server Search Domains Advanced Assist me If you want to get the IP address using the terminal you can use the following command This command will require you to enter the system name of the interface eno ipconfi
175. d thread the onPublish function is executed by the program Just like the previous function you can implement various operations within this function while the function behaves as the exit point of any message published using this Python MQTT client In the current implementation of onPublish we are not performing any operations def onPublish mosq obj mid pass In the opened Python file mattPython py you will only need to change the IP address of the server running the Mosquitto broker If you are running the Mosquitto broker on the same computer you can use 127 0 0 1 as the IP address of the localhost Before you execute this Python file ensure that your Arduino is running with the MQTT client we created in the previous exercise Once you run this code you can start seeing the messages being sent from your Arduino in the Python terminal as displayed in the following screenshot Whenever a new message is received the Python program prints the outTopic topic name followed by the From Arduino message This confirms that the Python client is receiving messages for outTopic to which it is subscribed If you look back at the Arduino code you will notice that it is the same message that we were publishing from the Arduino client 600 Python 2 7 6 Shell outTopic From outTopic From outTopic From outTopic From outTopic From outTopic From outTopic From outTopic From outTopic From outTopic From outTopic From
176. dden text input Dropbox to obtain a mutually exclusive input from a drop down list Radio to obtain mutually exclusive inputs from multiple options and Checkbox to select a binary input from the given options While all of these elements are very easy to implement you should select form elements only according to your program requirements In the web py implementation of Form the web page needs to execute the POST method every time the form is submitted As you can in see in the following implementation of the form in the template file we are explicitly declaring the form submission method as POST def with form i lt form method POST gt form render lt form gt Exercise 2 playing with web py concepts using the Arduino serial interface Now you have a general idea of the basic web py concepts used to build a web application In this exercise we will utilize the concepts you learned to create an application to provide the Arduino with sensor information As the goal of this exercise is to demonstrate the web py server for Arduino data we are not going to utilize the Ethernet Shield for communication Instead we will capture the Arduino data using the serial interface while using the web py server to respond to the requests coming from different clients As you can see in the following diagram we are using the same hardware that you designed for exercise 1 but without utilizing the Ethernet connection to our home ro
177. ddress of your recently prepared Arduino in the web browser You should be able to receive a similar response as displayed in the following screenshot Although we are only displaying humidity values through this sketch you can easily attach motion sensor values using additional client print methods 000 10 0 0 75 C B 10 0 0 75 Relative Humidity observation from HIH4030 is 46 29 Just like the mechanism we implemented in this exercise a web server responds to the request made by a web browser and delivers the web pages you are looking for Although this method is very popular and universally used to deliver web pages the payload contains a lot of additional metadata compared to the actual size of the sensor information Also the server implementation using the Ethernet server library occupies a lot of the Arduino s resources Arduino being a resource constrained device is not suitable for running a server application as the Arduino s resources should be prioritized to handle the sensors rather than communication Moreover the web server created using the Ethernet library supports a very limited amount of connections at a time making it unusable for large scale applications and multiuser systems The best approach to overcome this problem is by using Arduino as a client device or by using lightweight communication protocols that are designed to work with resource constrained hardware devices In the next few sections
178. degrees Locked ip fa Or 0 of 2 nets routed 2 connections still to be routed Share Addanote Rotate Fip 0 1781 011in 100 g As you can see a toolbox containing virtual hardware components is located to the right of the opened window The main editing space located in the center lets the user drag and drop components from the toolbox and also allows the user to complete connections between these components You can learn more about the features provided by Fritzing and go through some hands on tutorials at http fritzing org learning Working with the breadboard Once you are familiar with Fritzing you have the flexibility to create your own circuits or you can always use the Fritzing files provided with the book However there is another challenge that is porting your virtual circuit to a physical one One of the fundamental components used by electronics projects that let you implement connections and build the physical circuit is the breadboard The breadboard contains intelligently organized metal rows hidden under an assembly containing plastic holes This assembly helps the user to connect wires without going through any soldering work It is really easy to insert and remove wires or electronics components through the holes The following figure shows a small breadboard with a couple of components and a few wire connections Terminal strips DIP support etowe wwe EEE ES Power
179. dely using them in your future Arduino projects Beside these methods there is a wide variety of popular sensors that are based on integrated circuit IC which require different ways of communication These IC based advanced sensors utilize I2C or SPI bus based methods to communicate with the microcontroller As we are going to use 12C based sensors in the upcoming projects the section will only cover the I2C protocol and practical example to understand the protocol in a better way Once you understand the fundamentals of the 12C protocol you can learn the SPI protocol very quickly Note You can learn more about SPI protocol and the supported Arduino SPI library from the following links e http arduino cc en Reference SPI e http www instructables com id Using an Arduino to Control or Test an SPI electro In 1982 the Philips company needed to find out a simple and efficient way to establish communication between a microcontroller and the peripheral chips on TV sets which led to the development of the I2C communication protocol The I2C protocol connects the microcontroller or the CPU to a large number of low speed peripheral devices using just two wires Examples of such peripheral devices or sensors include I O devices A D converters D A converters EEPROM and many similar devices I2C uses the concept of master slave devices where the microcontroller is the master and the peripherals are the slave devices The following diag
180. ding Upgrading matplotlib installation errors troubleshooting Troubleshooting installation errors reference link Troubleshooting installation errors setting up on Ubuntu Setting up matplotlib on Ubuntu used for plotting random numbers Plotting random numbers using matplotlib media access control MAC address o about Networking fundamentals monitoring station remote home monitoring system o defining Stage 1 a monitoring station using Arduino Designing the monitoring station o Arduino sketch The Arduino sketch for the monitoring station Mosquitto o about Mosquitto an open source MOTT broker o URL Mosquitto an open source MOTT broker o setting up Setting up Mosquitto o initialization Getting familiar with Mosquitto most significant bit MSB o about Arduino coding for the TMP102 temperature sensor motion triggered LEDs o developing Motion triggered LEDs the project description project goals The project goal examples The project goal online resources The project goal software flow design The software flow design hardware system design The hardware system design o hardware connections testing Testing hardware connections motion triggered LEDs components o PIR sensors The list of components o LEDs The list of components O O O O 0 O O O O 0 O 0 0 O O O 0 0 wires The list of components resistors The list of components breadboard The list of components
181. ding data to a cloud platform while a computation unit is accessing the data remotely from the cloud Cloud Platform Com outer A Ethernet Sy Ethernet Arduino Sample architecture of the Internet of Things Xively being the oldest and most popular IoT platform has a large amount of community based online help that is available for beginners This is one of the major reasons why we have chosen Xively as our platform of choice for the upcoming exercises Recently Xively has changed their policy of creating free developer accounts and a user has to request access to this free account instead of obtaining one freely In case you want to use another platform other than Xively we have briefly covered a few similar platforms at the end of this section Xively a cloud platform for the IoT Xively is one of the very first loT specific cloud platforms that was founded in 2007 as Pachube It went through multiple name changes as it was called Cosm but it is currently known as Xively Xively provides an loT cloud platform with tools and services to develop connected devices products and solutions As mentioned on its website Xively is the public cloud that is specifically built for the IoT Setting up an account on Xively Now we can go ahead and set up a new user account for the Xively platform To set up an account you need to execute following steps in the given order 1 To begin the sign up pro
182. ding upon the application In this example we are utilizing a 5V DC motor because we want to supply the power using the Arduino board itself As the Arduino digital pin can only have two states that is HIGH 5V or Low 0V it is impossible to control the speed of the motor using just the OUTPUT mode As a solution we are going to implement the PwM mode via digital pins that are capable of supporting PWM While using pyFirmata pins configured with the PwM mode take any float input values between 0 and 1 0 which represent OV and 5V respectively Connections Depending upon the load DC motors can sometimes draw large amounts of current and harm the Arduino board To avoid any damage to the Arduino board due to any large accidental current draw we will use a transistor as a switch which only uses a small amount of current to control the large amount of current in the DC motor To complete the circuit connection as displayed in the following diagram you will need an NPN transistor TIP120 N2222 or a similar one one diode 1N4001 or similar one and a 220 ohm resistor with your DC motor Connect the base of the transistor to the digital pin 3 that also supports the PWM mode Connect the remaining components as displayed in the diagram 0 en am u r 5 5 Lasa RESET 1CSP2 L E U69 000000000000000000000000s0s00 eoeeeneeeeeeeeeeeeeeeee eee eee eeeesenstieeenteneeseeeeeeeeeeeeeeee A vr a
183. dity else motion data return motion Before you run this Python program make sure you have checked every component of the code and updated the values where needed Then execute the code from the terminal Your web server will now run on your local computer on the port number 8080 Power cycle your Arduino device in case the connection attempt from Arduino fails To test your system open the web application from your web browser You will see a web page open in your browser as displayed in the following screenshot 129 9 10 0 0 20 8080 x gt 5 gt D 10 0 0 20 8080 woas Arduino GET amp POST request to Web py Select sensor to send GET request to Arduino dropdowr Y Humidity Motion Humidity value is 18 2700870301 You can choose the sensor type from the dropdown menu Humidity or Motion before pressing the Submit button On submission you will be able to see the page updated with the appropriate sensor type and its current value Why do we need a resource constrained messaging protocol In the previous section you learned how to use the HTTP REST architecture to send and receive data between your Arduino and the host server The HTTP protocol was originally designed to serve textual data through web pages on the Internet The data delivery mechanism used by HTTP requires a comparatively large amount of computation and network resources which may be sufficient for a computer sys
184. ds to be changed from a regular monitor to something small and more portable To ensure its real world and meaningful application the thermostat should demonstrate real time operation It is important to note that the thermostat will not be interfacing with any actuators such as home cooling and heating systems As the interfacing of these systems with the thermostat project requires high level understanding and experience of working with heating and cooling systems it will deviate the flow of the chapter from its original goal of teaching you Arduino and Python programming Project goals and stages In order to describe the features that we want to have in the thermostat let s first identify the goals and milestones to achieve these objectives The major goals for the project can be determined as follows e Identify the necessary sensors and hardware components for the project e Design and assemble the circuit for the thermostat using these sensors and the Arduino board e Design an effective user experience and develop software to accommodate the user experience e Develop and implement code to interface the designed hardware with the software components The code development process of the thermostat project is divided into two major stages The objectives of the first stage include sensor interfacing the development of the Arduino sketch and the development of the Python code on your regular computer that you have been using all along
185. duino board Although we covered a vast amount of programming concepts with these prototyping examples the goal of the chapter was to make you familiar with the interfacing problems and provide quick recipes for your projects We are assuming that by now you are comfortable testing your sensors or project prototypes using Python and Arduino It s time to start working towards creating your applications that have complex Python features such as user controls charts and plots In the next chapter we are going to develop custom graphical user interfaces GUIs for your Python Arduino projects Chapter 5 Working with the Python GUI In the first four chapters we used the Python interactive prompt or Arduino serial monitor to observe the results The method of using text based output on prompt may be useful for basic and quick prototyping but when it comes to an advanced level of prototyping and demonstrating your prototype or final product you need to have a nice looking and user friendly interface GUI helps users to understand various components of your hardware project and easily interact with it It can also help you to validate the results from your project Python has a number of widely used GUI frameworks such as Tkinter wxPython PyQt PySide and PyGTK Each of these frameworks possesses an almost complete set of features that are required to create professional applications Due to the complexity involved these frameworks have diffe
186. e Update System Architecture to accommodate UX Define User Experience UX flow Identify development stages Assemble and code each stage Integrate Development Stages Test and Troubleshoot Once you have defined the set of major goals you need to break them down into project requirements that include every detail of the tasks that your prototype should execute to achieve these goals Using the project requirements you need to sketch out the overall architecture of the system The next step includes the process of defining the UX flow that will help you to lay out the user interaction points for your system At this stage you will be able to identify any changes that are required in the system architecture and the hardware and software components to start the development As you have defined the interaction points now you need to distribute the entire project development process into multiple stages and delegate the tasks between these stages Once you have completed the development of these stages you will have to interface these stages with each other according to your architecture and debug the components if it is needed At the end you will have to test your project as a whole system and troubleshoot minor problems In hardware projects it is very difficult to work on your electric circuits again after the completion of complex development processes as the changes can have recurring effects on all other comp
187. e pass return Ok The default URL http lt ip address gt 8080 displays the base template with the Refresh button populated using the Form method As displayed in the following code snippet the default index class renders the template with the updated current humidity and motion values when it receives the GET or POST request class index submit_form form Form form Button Refresh type submit description refresh GET function def GET self f self submit_form return render base f humidity motion POST function def POST self f self submit_form return render base f humidity motion Run the program from the command line Make sure that you are running both programs from separate terminal windows Testing your Mosquitto Gateway You have to follow these steps in the specified order to successfully execute and test all the components of this exercise 1 Run the Mosquitto broker 2 Run the Arduino client If it is running already restart the program by powering off the Arduino client and powering it on again 3 Execute the web application in your terminal or from the Command Prompt 4 Run the paho mqtt Gateway program If you follow this sequence all of your programs will start without any errors If you get any errors while executing make sure that you follow all the instructions correctly while also confirming the IP addresses in your programs To check out your Arduino MQT
188. e UX flow Tweet a PowerStrip o about User experience flow V e variables o about Variables e virtual instance on AWS EC2 service o creating Creating a virtual instance on the AWS EC2 service o logging into Logging into your virtual instance e void data type o about Data types W e web py o used for developing web applications Python web framework web py o installing Installing web py o basic concepts Essential web py concepts for developing complex web applications URL handling Handling URLs GET methods The GET and POST methods POST methods The GET and POST methods templates Templates forms Forms with Arduino serial interface Exercise 2 playing with web py concepts using the Arduino serial interface e web application remote home monitoring system o about Stage 3 a web application using Xively Python and Amazon cloud service o architecture Architecture of the cloud services o Python web application hosted on Amazon AWS Python web application hosted on Amazon AWS o testing Testing the web application Testing and troubleshooting e web applications o developing with Python Developing web applications using Python o developing web py used Python web framework web py o implementing web py used Your first Python web application e while statement o about The while statement e wide area network WAN o about Networking fundamentals e Windows o Pyt
189. e you can also navigate to Start Control Panel System and Security System You will be able to see a window similar to the one that is displayed in the following screenshot The System window shows you the basic information about your computer including the type of Windows operating system that you are using such as the 32 bit or the 64 bit version OW Control Panel All Control Panel Items System earch Control Pane File Edit View Tools Help Control Panel Home s ee d View basic information about your computer de Device Manager Windows edition By Remote settings Windows 7 Ultimate System protection Copyright 2009 Microsoft Corporation All rights reserved Y Advanced system settings Service Pack1 System Rating En Windows Experience Index Processor Intel R Core TM 17 3632QM CPU 2 20GHz 2 20 GHz Installed memory RAM 12 0 GB 11 9 GB usable System type 64 bit Operating System Pen and Touch No Pen or Touch Input is available for this Display Computer name domain and workgroup settings Action Center Computer name chheplo PC W Change settings Wind Updat N DEREN Full computer name chheplo PC Performance Information and 3 Took Computer description Workgroup WORKGROUP In the System window click on Advanced system settings in the left navigation bar to open a window called System Properties Click on the Environment Variables button in the System Proper
190. e you will be able to see a relative humidity value obtained using the GET method Now you can enter an appropriate temperature value and press the submit button to invoke the POST method On successful execution you will be able to see the latest relative humidity value which is calculated based on the temperature value that you submitted RESTful web applications with Arduino and Python In the previous exercise we implemented the GET and POST requests using the web py library These requests are actually part of the most popular communication architecture of the World Wide Web WWW called REST The REST architecture implements a client server paradigm using the HTTP protocol for operations such as POST READ and DELETE The GET and PosT functions implemented using web py are functional subsets of these standard HTTP REST operations that is GET POST UPDATE and DELETE The REST architecture is designed for network applications websites and web services to establish communication through HTTP based calls Rather than being just a set of standard rules the REST architecture utilizes existing web technologies and protocols making it a core component of the majority of the websites we use today Due to this reason the WWW can be considered to be the largest implementation of REST based architecture Designing REST based Arduino applications The REST architecture uses a client server model where the server acts as a centralized
191. e Pause is pressed even rotating the knob will not result in any updates to the plot As soon as you click on the Start button again you will again see the plot get updated with real time values discarding the values generated while paused Click on the Exit button to safely close the program A O O Tkinter ma Start Pause Exit A Figure 1 Potentiometer Summary In this chapter we introduced two major Python programming paradigms creating reading and writing files using Python while also storing data into these files and plotting sensor values and updating plots in real time We also explored methods to store and plot real time Arduino sensor data Besides helping you in your Arduino projects these methods can also be used in your everyday Python projects Throughout the chapter using simple exercises we interfaced the newly learned CSV and matplot1ib modules with the Tkinter and pyFirmata modules that we learned in the previous chapters In the next chapter you will be introduced to your second project a portable unit that measures and displays environmental data such as temperature humidity and ambient light We will be utilizing the concepts that we have learned so far to build this project Chapter 7 The Midterm Project a Portable DIY Thermostat After the first Python Arduino project you learned the process of prototyping various sensors developing user interfaces and plotting sensor data The conce
192. e extensively using 5V of power and ground pins for our projects Digital pins DO and D1 support serial interfacing through the Tx transmission and Rx receiver interfaces respectively The USB port on the board can be used to connect Arduino with a computer Analog pins ISOW dS2I WIS 24501 OSIW 24521 ZLG OSIN LLO WMd ISOW OLG WMd SS Digital pins Serial interface Now that we are familiar with the Arduino hardware let s move on to programming the Arduino board Installing the Arduino IDE The first step to start getting familiar with Arduino is to install the Arduino integrated development environment IDE According to the operating system that you selected at the beginning of the Python installation section follow the appropriate subsection to install the correct IDE Linux The installation of the Arduino IDE is really simple in Ubuntu The Ubuntu repository already includes the Arduino IDE with the required dependencies For Ubuntu 12 04 or a newer version execute the following command in the terminal to install Arduino sudo apt get update amp amp sudo apt get install arduino arduino core The latest version of the Arduino IDE in the Ubuntu repository is 1 0 3 You can obtain more information regarding other Ubuntu related questions at http playground arduino cc Linux Ubuntu For Fedora 17 or a newer version of Red Hat Linux execute the following script in the terminal sudo yum install
193. e familiar with arrays in C C it will be easier for you to get started as the Arduino language uses the same C C arrays The following are some of the methods to initialize an array int myIntArray 1 2 3 4 5 int tempValues 5 32 55 72 75 char msgArray 10 hello An array can be accessed using an index number where the index starts from number 0 1 art ss nal msg Conversions Conversion functions are used to convert any data type value into the provided data types The Arduino language implements the following conversion functions that can be utilized during programming char This converts the value of any data type to the character data type byte This converts the value of any data type to the byte data type int This converts the value of any data type to the integer data type float This converts the value of any data type to the floating point number data type As a demonstration of using these functions check out the following example int myInt 10 float myfloat float myInt Implementation of the preceding code will create a floating point variable myFloat with value 10 0 using the integer value initialized by the myInt variable Functions and statements Functions also called subroutines or procedures are a piece of code implemented to do specific tasks The Arduino language has some predefined functions and the user can also write custom functions to implement certa
194. e feeds As specified in the following code snippet try to get the specified channel from the feed or create one if it is not present on the Xively virtual device You can also specify tags and other variables while creating a new channel try datastream feed datastreams get Random except HTTPError as e print HTTPError 1 format e errno e strerror datastream feed datastreams create Random tags python print Creating Random datastream Once you have opened the data stream for a channel you can specify the current value using the datastream cuurent_value method and update the value which will upload this value to the specified channel datastream current_value randomValue datastream at datetime datetime utcnow datastream update Once you have performed the specified modifications to the uploadBasicXively py file execute it using the following command python uploadBasicXively py Open your virtual device on the Xively website to find the Random channel populated with the data that you uploaded It will look similar to the following screenshot Random 0 4467869376 4633315 python a few seconds ago lt 5 minutes Uploading data using a web interface based on web py In the previous chapter we worked with the web py library while developing templates and web applications In this exercise we will utilize one of the programs in which we created the web py forms with the Xively
195. e in the code snippet we used the additional pyplot methods such as title xlabel ylabel and plot These methods are self explanatory and they are largely used to make your plots more informative and meaningful At end of the example we used one of the most important pyplot methods called show The show method displays the generated plots in a figure This method is not mandatory to display figures when running from Python s interactive prompt The following screenshot illustrates the plot of randomly generated values using matplotlib 800 _ Figure 1 First Plot Random integers Plotting data from a CSV file At the beginning of the chapter we created a CSV file from Arduino data We will be using that SensorDataStore csv file for this section If you recall we used two different sensors to log the data Hence we have two arrays of values one from a digital sensor and another from the analog one Now in the previous example we just plotted one set of values for the y axis So how are we going to plot two arrays separately and in a meaningful way Let s start by creating a new Python program using the following lines of code or by opening the plotcsv py file from this chapter s code folder import csv from matplotlib import pyplot i mValues pValues with open SensorDataStore csv r as f reader csv reader f header next reader None for row in reader i append int row
196. e initialization parameters loop contains the logical parameters of your program void loop digitalwrite led HIGH delay 1000 digitalwrite led LOW delay 1000 As you can see in the preceding code snippet from the Blink sketch the loop function executes the main code that blinks the LED and repeats the process iteratively The pinMode function The pinMode function is used to set the behavior of Arduino As we saw in the setup function of the Blink sketch the pinMode function configures the LED pin for OUTPUT pinMode led OUTPUT Here the led variable is assigned to digital pin 13 whose mode will be changed by the pinMode function Working with pins Once you are done configuring the pins that will be used by your program you also need help in reading the input from these pins or for sending signals to them Arduino provides a few specific functions to handle these scenarios e digitalwrite This was developed for digital I O pins This function sets the pin to HIGH 5V or Low OV which are already configured as OUTPUT using pinMode For example the following line of code sets digital pin 13 to HIGH digitalwrite 13 HIGH e digitalRead Similar to digitalwrite this function helps you to read the state of a digital pin that is configured as INPUT value digitalRead 13 e analogRead This function reads the value from a specific analog pin The value is linearly mappe
197. e loop for 25 iterations You can change this value You can also change the time delay between each successive point from one second as used in the program to the value that you need Getting started with matplotlib The matplotlib library is one of the most popular and widely supported Python plotting libraries Although matplotlib is inspired by MATLAB it is independent of MATLAB Similar to other Python libraries that we have been using it is an open source Python library The matplotlib library assists in creating 2D plots from simple lines of code from easy to use built in functions and methods The matplotlib library is extensively used in Python based applications for data visualization and analysis It utilizes NumPy the short form of numerical Python and SciPy short form of scientific Python packages for mathematical calculations for the analysis These packages are major dependencies for matplotlib including freetype and pyparsing Make sure that you have these packages preinstalled on your system if you are using any other installation methods besides the ones mentioned in the next section You can obtain more information about the matplotlib library from its official website http matplotlib org Configuring matplotlib on Windows Before we install matplotlib on Windows make sure that you have your Windows operating system with the latest version of Python 2 x distribution In Chapter 1 Getting Started with Python and Arduin
198. e most popular IP addresses is 127 0 0 1 which is also called the localhost IP address Apart from the IP address assigned to a computer by the network each computer also has the localhost IP address associated with it The localhost IP address is very useful when you want to internally access or call your computer from the same device In the case of a remote access application you need to know the IP address assigned by the network Obtaining the IP address of your computer Arduino is a resource constrained device and therefore it can only demonstrate a limited amount of network capability While working with Arduino based projects that include the utilization of a computer network you will require a server or Gateway interface These interfaces include but are not limited to a desktop computer a laptop the Raspberry Pi and other remote computing instances If you are using these interfaces as part of your hardware project you will need their IP addresses Ensure that they are under the same network as your Arduino The following are the techniques to obtain IP addresses in major operating systems Windows In most versions of the Windows OS you can obtain the IP address from the Network Connection utility in Control Panel Navigate to Control Panel Network and Internet Network Connections and open the Local Area Connection Status window Click on the Details button to see the details of the Network Connection Details window As
199. e of unique strings for the title of the window will help you to differentiate these windows according to their properties when you are dealing with multiple windows in one application top Tkinter Tk top title Specify time using Entry Although the Entry widget can be easily initialized by specifying the parent widget as the only parameter it also supports a large number of parameters to customize the widget For example in our exercise we are using the bd parameter to specify the width of the widget border and width to provide the expected width of the widget You can learn more about the available options at http effbot org tkinterbook entry htm timePeriodEntry Tkinter Entry top bd 5 width 25 timePeriodEntry pack timePeriodEntry focus_set startButton Tkinter Button top text Start command onStartButtonPress startButton pack In the preceding lines of code we have initialized two widget objects in our main window timePeriodEntry for the Entry widget and startButton that we used in the previous exercise for the Button widget The Pack geometry manager always sets the graphical pointer to the last widget that has been added to the main window We can manually shift the focus of the graphical pointer to the timePeriodEntry widget using the focus_set method Contrary to the onStartButtonPress function in the previous exercise this function doesn t use the time delay fix It instead obtains the value
200. e the Arduino MQTT library PubSubClient in the previous chapter which means that your Arduino IDE should already have the PubSubClient library installed on it At the beginning of the code we have also declared few constants such as the IP addresses of the MQTT server and Arduino and the pin numbers of various sensor and actuators Note You will have to change the IP address of the monitoring station and the control center according to your network setup Make sure that you perform these modifications before uploading the Arduino code In the code structure we have two mandatory Arduino functions setup and loop In the setup function we will set up the Arduino pin types and the MQTT subscriber channels In the same function we will also attach an interrupt for the press of the button while setting up the timer for the publishData function Publishing sensor information The publishData function reads the sensor inputs and publishes this data to the Mosquitto broker that is located on the control center As you can see in the following code snippet we are measuring sensors values one by one and publishing them to the broker using the client publish method void publishData Wire requestFrom partAddress 2 byte MSB Wire read byte LSB Wire read int TemperatureData MSB lt lt 8 LSB gt gt 4 float celsius TemperatureData 0 0625 temperatureC dtostrf celsius 5 2 message_buff2 client pu
201. e the status of the motion sensor It also blinks the physical LEDs using the write method and the inserted time delay As input parameters the blinkLED function accepts the pin object and a message string from the function call where the pin objects that is redPin or greenPin should be one of the pin assignment for the LEDs def blinkLED pin message MotionLabel config text message MotionLabel update_idletasks top update pin write 1 sleep 1 pin write 0 sleep 1 The other two Tkinter related functions onStartButtonPress and onExitButtonPress are basically derived from the previous exercise In this version of onStartButtonPress we call the blinkLED function if the flag variable is True and the motion is detected using pinPir read def onStartButtonPress while True if flag get if pirPin read is True blinkLED redPin Motion Detected else blinkLED greenPin No motion Detected else break board exit top destroy The program also instantiates two buttons Start and Exit and one label using the methods similar to those we used in the previous exercises As you can observe from the code the logic behind the motion detection system is still the same We are only adding a layer of graphical interface to display the state of the detected motion continuously using a Label widget We have also added the Start and Exit buttons to control the project execution cycle Once you run the code
202. e we have now implemented the GET request we can use a similar approach to exercise the POST request Instead of asking the server to provide a response for a state request we will send sensor data as payload from Arduino in the implementation of the POST request Similarly on the server side we will utilize web py to accept the POST request and display it through a web browser The Arduino code to generate the POST request Open the Arduino sketch ArduinoPOST ino from the Arduino_POST_Webpy ArduinoPOST folder of the code repository As in the previous exercise you will first have to provide the IP address and the MAC address of your Arduino Once you have completed these basic changes observe the following code snippet for the implementation of the POST request You might notice that we are creating payload for the POST request as the variable data from the values obtained from analog pin 0 String data data data Humidity data analogRead analogChannel In the following Arduino code we ll first create a client object using the Ethernet library In the recurring 1oop function we ll use this client object to connect to the web py server running on our computer You will have to replace the IP address in the connect method with the IP address of your web py server Once connected we ll create a custom POST message with the payload data we calculated previously The Arduino loop function will periodically send
203. ect or even on the Amazon AWS server For the development stage let s start with the regular computer that you have been using all along We are assuming that this computer has the Mosquitto broker installed and running Note down the IP address of this unit as you will need it in the Arduino code that you developed in the previous section Python software flow The Python code deals with two services during execution the Twitter API to get or post tweets and the Mosquitto broker to relay messages to the hardware unit The program begins by parsing the latest tweet from the user account and checking whether it has been utilized in the previous action or not This avoids any command duplication as the frequency of new tweets is significantly lower than the frequency of the program loop Once the code finds a new tweet with the appropriate keywords to perform operations on the appliance or appliances it publishes the message to the Mosquitto broker If the tweet contains a message to check the status the code requests the status from your Arduino and posts a new tweet with the status after receiving it The following diagram shows the detailed program flow of the computation unit Parse tweets has new tweet D Ye S Update tweet ID as keyword to toggle power Delay before next parse has keywords to check status Publish on off message for power Publish status inquiry message Twe
204. ect the type of Arduino board on which you are going to upload your sketch The Arduino IDE needs to know the type of board in order to compile the program for the appropriate microcontroller as different Arduino boards can have different Atmel microcontrollers Therefore you need to perform this step before you go ahead with the compiling or uploading of the program to the board You can select the Arduino board by navigating to Tools Board as displayed in the following screenshot sketch_nov03a Arduino 1 0 5 File Edit Sketch Tools Help Auto Format Archive Sketch Fix Encoding amp Reload Serial Monitor sketch_nov033 Ctri Shift M Board gt Arduino Uno Arduino Duemilanove w ATmega328 Arduino Diecimila or Duemilanove w ATmegal68 Programmer Arduino Nano w ATmega328 Burn Bootloader Arduino Nano w ATmegal68 Arduino Mega 2560 or Mega ADK Arduino Mega ATmegal280 Arduino Leonardo Arduino Esplora Arduino Micro Arduino Mini w ATmega328 Arduino Mini w ATmegal68 Arduino Ethernet Arduino Fio Arduino BT w ATmega328 Arduino BT w ATmegal68 LilyPad Arduino USB LilyPad Arduino w ATmega328 LilyPad Arduino w ATmegal68 Arduino Pro or Pro Mini 5V 16 MHz w ATmega328 Arduino Pro or Pro Mini 5V 16 MHz w ATmegal68 Arduino Pro or Pro Mini 3 3V 8 MHz w ATmega328 Arduino Pro or Pro Mini 3 3V 8 MHz w ATmegal68 Arduino NG or older w ATmegal68 Ardu
205. ectronic components with Arduino The second interfacing abstraction is associated with Arduino and the physical components As we already did various electronics components can be simply interfaced with the Arduino board using digital or analog pins These components deal with either digital or analog signals A few digital pins on the Arduino board support PWM communication for specific hardware devices The other alternative interfacing methods include I2C and serial peripheral interface SPI communication The I2C method is comprehensively explained in the final section of this chapter Working with pyFirmata methods The pyFirmata package provides useful methods to bridge the gap between Python and Arduino s Firmata protocol Although these methods are described with specific examples you can use them in various different ways This section also provides a detailed description of a few additional methods that were not used in the previous project and lists the missing features Setting up the Arduino board To set up your Arduino board in a Python program using pyFirmata you need to specifically follow the steps that we have covered We have distributed the entire code that is required for the setup process into small code snippets in each step While writing your code you will have to carefully use the code snippets that are appropriate for your application You can always refer to the example Python files containing the complete code
206. ed libraries first we need an operating system for the Raspberry Pi A Raspberry Pi officially supports Linux based open source operating systems that are preconfigured for custom Raspberry Pi hardware components Various versions of these operating systems are available on Raspberry Pi s website http www raspberrypi org downloads Raspberry Pi s website provides a variety of OSes for users who range from newbies to experts It is difficult for a first time user to identify the appropriate OS and its installation process If this is your first attempt with a Raspberry Pi we recommend that you use the New Out Of Box Software NOOBS package Download the latest version of NOOBS from the previous link The NOOBS package includes few different operating systems such as Raspbian Pidora Archlinux and RaspBMC NooBs streamlines the entire installation process and helps you to install and configure your preferred version of the OS easily It is important to note that NOOBS is just an installation package and you will be left with only the Raspbian OS once you complete the given installation steps Raspberry Pi uses the SD card to host the operating system and you need to prepare the SD card from your computer before placing it into the SD card slot of the Raspberry Pi Insert your SD card into your computer and make sure that you have a backup of any important information that is on the SD card During the installation process you will lose al
207. eives a message on_message and publishes a message on_publish Once you have initialized these methods you can connect your client to the Mosquitto server by specifying the server IP address and the port number To subscribe to or publish for a topic you simply need to implement the subscribe and publish methods on the client respectively as displayed in the following code snippet In this exercise we are using the loop_forever method for the client to periodically check the broker for any new messages As you can see in the code we are executing the publishTest function before the control enters the loop cli mq Client mosquittoPython cli on_message onMessage cli on_publish onPublish cli connect 10 0 0 20 1883 15 cli subscribe outTopic 0 publishTest cli loop_forever It is very important to run all the required functions or pieces of code before you enter the loop as the program will enter the loop with the Mosquitto server once loop_forever is executed During this period the client will only execute the on_publish and on_message methods for any update on the subscribed or published topics To overcome this situation we are implementing the multithreading paradigm of the Python programming language Although we are not going to dive deep into multithreading the following example will teach you enough to implement basic programming logic To understand more about the Python threading library and
208. el top text Humidity font Helvetica 20 grid column 1 row 2 Similarly the font option is added to the observation labels HumdUnitLabel Tkinter Label top text font Helvetica 20 The labels for the observation unit also carry similar modifications HumdLabel config text cleanText reading 1 font Helvetica 20 The Thermostat_ Stage2 py file already includes the preceding modifications and is ready to run on your Raspberry Pi Before you run the file first we need to copy the file to the Raspberry Pi At this stage the USB hub will be very handy to copy the files If you don t have a USB hub you can utilize two available USB ports simultaneously to attach the USB pen drive mouse and keyboard With the use of the USB hub connect the USB pen drive containing the Python files and copy them to the home folder Attach the USB port of the Arduino board to one of the ends of the USB hub From the start menu of the Raspberry Pi open the LXTerminal program by navigating to Accessories LXterminal Run the Python code from the home folder and you will be able to see the optimized user interface window that opens on the Raspberry Pi s screen If every step mentioned in the chapter is performed correctly you will be able to see the sensor observation being printed when you click on the Start button 7 Tkinter matplotlib F Temperature Humidity Light Start Exit At the end of the chapter you must
209. ely that if you just click on the file it opens in a web browser Make sure that you open the file in a text editor In the opened file you ll see that we are initializing the template file with def with form humidity In this initialization form and humidity are input variables that are required by the template during the rendering process The template declares the actual lt form gt element with the form render method while displaying the humidity value using the humidity variable lt form method POST gt form render lt form gt lt h3 gt Relative Humidity is lt h3 gt lt p name temp gt humidity lt p gt Although the template file renders the form variable we have to define this variable in the Python program first As you can see in the following code snippet we have declared a variable called submit_form using the form Form method of the web py library The submit_form variable includes a Textbox element to capture the temperature value and a Button element to enable the submit action submit_form form Form form Textbox Temperature description Temperature form Button submit type submit description submit When you want to access the current submitted values of the submit_form variable you will have to validate the form using the validates method f self submit_form f validates Now we have the user facing web page and input components designed for the exercise It
210. ementing for your future projects Designing system architecture Continuing from project goals first you need to sketch out a high level architecture of the system This architectural sketch should include major components that enable the system to pass on information between the sensors and the remote users The following figure shows an architectural sketch for our project ll nn ve N t Xively 2 Z cloud a Monitoring Station E I NE ee Room1 BR A x oe yi A ey Ethernet ee N Pa WiFi ae i p Amazon 2 Monitoring Station Instance p y ey i E _ u Control Center Ethernet According to the goals the user should be able to access the system using the Internet this means that we need cloud components in the architecture The system also needs to monitor the physical environment using a resource constrained device and this can be executed using Arduino The middle layer which connects the cloud service and the sensor system can be built using a Raspberry Pi In the last project we connected Arduino and the Raspberry Pi using a serial connection but we want to move away from serial connections and start using our home s Ethernet network to make the system deployable Hence the Arduino based unit is connected to the network using Ethernet while the Raspberry Pi uses Wi Fi to connect to the same network In order to lay out the overall system architecture let s utilize the sketch that we designed which c
211. en Temperature Light Arduino Raspberry Pi serial Thermostat Sensor Unit Thermostat Computation Unit As the common unit for both stages of the project the Arduino centric thermostat sensor unit requires slightly more complex circuit connections compared to other exercises that you have been through In this section we are going to interface the necessary sensors and push buttons to their respective pins on the Arduino board and you will need a breadboard to make these connections If you are familiar with PCB prototyping you can create your own PCB board by soldering these components and avoid the breadboard PCB boards are more robust compared to breadboards and less prone to loose connections Use the following instructions and the Fritzing diagram to complete the circuit connections 1 As you can see in the following diagram connect the SDA and SCL pins of TMP102 and BH1750 to analog pins 4 and 5 of the Arduino board and create an I2C bus To make these connections you can use multiple color coded wires to simplify the debugging process 2 Use two 10 kilo ohm pull up resistors with the SDA and SCL lines 3 Contrary to these I2C sensors the HIH 4030 humidity sensor is a simple analog sensor and can be directly connected to the analog pin Connect the HIH 4030 to the analog pin AO 4 Connect VCC and the ground of TMP102 BH1750 and HIH 4030 to 5V and the ground of the Arduino board using power strips of the breadboard
212. en you are using compatible components instead of the exact components from the prototype diagram The following is a schematic diagram of the electronics circuit that we designed earlier This diagram is also obtained using Fritzing 5V VIN RESET Arduino TUDO RESET2 Uno RX D1 AREF Rev3 PWM D9 SS PWM D10 MOSI PWM D11 MISO D12 SCK D13 ICSP2 MISO ICSP2 SCK ICSP MOSI Your system is now ready to run the Arduino program As we will be using the same hardware for both the programming methods you are almost done working with electronics unless you encounter a problem Just to make sure that everything is connected perfectly let s check out these connections in the next section Note Note that pull up resistors are used to make sure that the output signal from a PIR sensor settles at the expected logic level Testing hardware connections Once the circuit connections are complete you can go directly to the programming sections As a best practice we recommend that you verify the circuit connections and check the sensor s status We are assuming that your Arduino board is already equipped with the StandardFirmata sketch that we discussed in the previous chapter Otherwise refer to the previous chapter and upload the StandardFirmata sketch to your Arduino board The best way to verify our circuit implementation is to use the Firmata test program that we used in the previous chapter
213. enable networking for the Arduino platform Among these devices a few can be used as extensions for your existing Arduino board while others exist as standalone Arduino modules with networking capabilities The most popular extensions used to enable networking are the Arduino Ethernet Shield and Arduino WiFi Shield Similarly Arduino Yun is an example of a standalone Arduino platform that includes built in networking capabilities In this book we are going to develop various networking applications around the Arduino Ethernet Shield There are also a few other extensions Arduino GSM Shield and standalone Arduino platforms Arduino Ethernet Arduino Tre and so on but we are not going to cover them in detail Let s get familiar with the following Arduino extensions and board Arduino Ethernet Shield The Arduino Ethernet Shield is an officially supported and open source network extension designed to work with Arduino Uno The Ethernet Shield is equipped with an RJ45 connector to enable Ethernet networking The Ethernet Shield is designed to mount on top of Arduino Uno and it extends the layout of the pins from your Arduino Uno to the top of the board The Ethernet Shield is also equipped with a microSD card slot to store important files over the network Just like most of these shield extensions the Ethernet Shield is powered by the Arduino board it is attached to t un DIGITAL PWM SPI Tas CO ETHERNET LS ARDUINO SHIELD
214. ents to a computer instead of directly spending a significant amount of resources for the schematic design PCB manufacturing and developing the complete code base This stage helps you to identify major flaws in your circuit design and check the mutual compatibility of the selected components Fortunately Arduino and the existing software support around Arduino have really simplified electronics prototyping In the upcoming sections we will go through various helper functions and interfacing exercises to help you proceed with your own projects These examples or templates are designed in such a fashion that they can be used as a blueprint for larger projects Before diving into these prototyping examples let s understand two different abstractions of interfacing that we are going to explore in this chapter e Interfacing Arduino with Python We have learned the easiest method of Python Arduino interfacing using the Firmata protocol On the Arduino board the Firmata protocol is implemented using the StandardFirmata firmware while on the Python end we used the Firmata libraries pyFirmata or pyMata for Python Another Python Arduino interfacing method includes the use of simple but nonstandard serial commands using the custom Arduino sketch and the pySerial library in the Python program It is also possible to use a computer network to establish communication between Python and Arduino which is covered later in the book e Interfacing el
215. environment and can be part of your daily routine The thermostat is one of the most important components of any remote home monitoring system and home automation system A popular commercial example of a connected thermostat is the Nest Thermostat https www nest com which provides intelligent remote monitoring and scheduling features for your existing home s heating and cooling system Before we think about a full stack product such as Nest we need first need to build a DIY thermostat with the basic set of features Later we can build upon this project by adding features to improve the DIY thermostat experience Let s first outline the features that we are planning to implement in this version of the thermostat project Project background Temperature humidity and ambient light are the three main physical characteristics that we want to monitor using the thermostat In terms of user experience we want to have an elegant user interface to display the measured sensor data The user experience can be more resourceful if any of this sensor data is plotted as a line graph In the case of a thermostat the visual representation of the sensor data provides a more meaningful comprehension of the environment than just displaying plain numerical values One of the major objectives of the project is to make the thermostat portable and deployable so that it can be used in your day to day life To satisfy this requirement the thermostat display nee
216. environment to obtain the IP address of your computer ifconfig You can obtain the IP address from the inet addr field of the appropriate adapter as displayed in this screenshot chheplo chheplo PPAF ifconfig etho Link encap Ethernet HWaddr 08 00 27 fb 83 f6 inet addr 10 0 0 15 Bcast 10 0 0 255 Mask 255 255 255 0 inet addr fe80 a00 27ff fefb 83f6 64 Scope Link UP BROADCAST RUNNING MULTICAST MTU 1500 Metric 1 RX packets 1549 errors 0 dropped overruns frame 0 TX packets 802 errors 0 dropped 0 overruns 0 carrier 0 collisions 0 txqueuelen 1000 RX bytes 2262119 2 2 MB TX bytes 61188 61 1 KB If supported by your operating system another command that can be utilized to obtain the IP address is hostname hostname I Be careful when using this utility to obtain the IP address as you may end up getting the IP address of a different adapter if you are not familiar with the supported command options of the utility Note If you are going to connect your Arduino to the same local area network as your computer make sure you are choosing the proper IP address that is covered by the same domain as that of your computer Also ensure that no other network device is using the same IP address that you have selected for your Arduino This practice will help you avoid IP address conflicts within the network Networking extensions for Arduino There are various hardware devices available in the Arduino community that
217. er parameter For example through subplot 2 1 1 we created a table of two rows and one column and placed the first subplot in the first cell of the table Similarly the next set of values was used for the second subplot and was placed in the second cell that is row 2 and column 1 pyplot subplot 2 1 2 In the first subplot we have used the plot method to create a plot using the analog value from the potentiometer that is pvalues While in the second subplot we created a bar chart instead of a line chart to display the digital values from the motion sensor The bar chart functionality was provided by the bar method As you can see in the code snippet we have utilized an additional pyplot method called xlim The x1im x_minimum x_maximum or ylim y_minimum y_maximum methods are used to confine the plot between the given maximum and minimum values of the particular axes Before we displayed these subplots in the figure using the show method we used the tight_layout function to organize the title and label texts in the figure The tight_layout function is a very important matplot1ib module that nicely fit the subplot parameters in one figure You can check the effects of this module by commenting that line and running the code again The following screenshot shows these subplots with labels and a title in one figure object Plotting real time Arduino data In the previous chapter while dealing w
218. erent row values for the widgets while having similar column values As a result our widgets will be organized in the same column and they will have their description labels in the next column of the same row You can skip to the output window if you want to check this organization pattern So far we were relying on the user to manually close the main window However you can create another Button widget and through that call the method to close this window In this coding exercise we have an additional button compared to the previous exercise that is Called exitButton The command parameter associated with this button is quit which ends the loop started by the Tkinter method top mainloop and closes the GUI exitButton Tkinter Button top text Exit command top quit exitButton grid column 2 row 3 In this code sample the quit method is initialized as a command option and it can be also be called as a method top quit Before we go ahead to the next step perform the appropriate changes in the code and run the program You will be prompted with a window similar to the one displayed in the following screenshot 600 Grid example The red dotted lines are inserted later to help you identify the grid and they won t appear in the window that is opened by running the program You can now clearly identify the role of each widget due to the presence of the description label beside them In the opened window play around with t
219. erminal As you can see the file starts with usr bin python which is the default Python installation location By adding this line in your Python code you can directly execute a Python file from the terminal In Unix based operating systems you need to make the test py file executable through the following command chmod x test py Now as your file is executable you can directly run the file using the following command test py Note For Unix based operating systems an alternative way to provide the Python interpreter location is to use the following line of code instead of the one that we used usr bin env python In Windows operating systems Python files automatically become executable because of the py extension You can just run the program files by double clicking and opening them The Python code As you now know how to create and run Python code let s create a new Python file with the following code snippet and run it Make sure to change the value of the port variable according to your operating system as described in the previous chapter usr bin python Import required libraries import pyfirmata from time import sleep Define custom function to perform Blink action def blinkLED pin message print message board digital pin write 1 sleep 1 board digital pin write 0 sleep 1 Associate port and board with pyFirmata port dev ttyACM0 board pyfirmata Arduino port
220. ers and can work uninterrupted without worrying about their status While discussing the limitations of the REST architecture we noticed that it requires the implementation of both the HTTP client and server on the Arduino end to enable bidirectional communication with Arduino With the broker based architecture demonstrated by pub sub you only need to implement lightweight code for the publisher or subscriber client on Arduino while the broker can be implemented on a device with more computation resources Henceforth you will have bidirectional communication enabled on Arduino without using significant resources Introduction to MQTT Message Queue Telemetry Transport MQTT is a very simple easy and open implementation of the pub sub paradigm IBM has been working on standardizing and supporting the MQTT protocol The documentation for the latest specification of the MQTT protocol v3 1 can be obtained from the official MQTT website at http www matt org As a standard for machine messaging MQTT is designed to be extremely lightweight and with a smaller footprint for code while also using a lower network bandwidth for communication MQTT is very specifically designed to work on embedded systems like hardware platforms such as Arduino and other appliances that carry limited processor and memory resources While MQTT is a transport layer messaging protocol it uses TCP IP for network level connectivity As MQTT is designed to support
221. erve in the code the timePeriodEntry object an Entry widget now uses the grid method instead of the pack method The grid method is initialized with the column and row options The values supplied for these options determine the position of the cell where the timePeriodEntry object will be placed On the other hand we have also created a label object using the Label widget and placed it beside the Entry widget in the same row The label contains a description string that is specified using the text option After placing it in a cell using the grid method widgets are arranged in the center in that cell To change this alignment you can use the sticky option with one or more values from N E S and W that is north east south and west timePeriodEntry Tkinter Entry top bd 5 timePeriodEntry grid column 1 row 1 timePeriodEntry focus_set Tkinter Label top text Time seconds grid column 2 row 1 We have repeated this practice of placing the widget in a cell and describing it using a Label widget for the objects of the Scale and Button widgets as well brightnessScale Tkinter Scale top from_ 0 to 100 orient Tkinter HORIZONTAL brightnessScale grid column 1 row 2 Tkinter Label top text Brightness grid column 2 row 2 startButton Tkinter Button top text Start command onStartButtonPress startButton grid column 1 row 3 As you can see in the preceding code snippet we are using diff
222. es URL When do we use other languages installing Installing Python and Setuptools installing on Linux Linux installing on Ubuntu Ubuntu installing on Fedora Red Hat Linux Fedora and Red Hat installing on Windows Windows URL for downloading Windows Mac OS X installing on Mac OS X Mac OS X pip installing Installing pip o URL for documentation Controlling the flow of your program e Python code Tweet a PowerStrip o about The Python code e Python context manager o reference link The with statement Python context manager e Python data downloading to Xively o about Python downloading data from Xively o basic method for retrieving data The basic method for retrieving data from Xively o data retrieving from web py web interface Retrieving data from the web py web interface o custom notifications from Xively Triggers custom notifications from Xively o triggers Triggers custom notifications from Xively e Python data uploading to Xively o about Python uploading data to Xively O O O O O O 0 G0 O O o basic method for sending data The basic method for sending data o web interface used Uploading data using a web interface based on web py e Python executable files o using Working with Python executable files e Python functions o using Working with Python functions o def keyword Working with Python functions e Python GUI o Tkinter Learning Tkinter fo
223. es the reader function to read a CSV file Check out the following example to learn more about this function or you can open the csvReader py file from the next chapter s code folder import csv with open example csv r as file r csv reader file for row in r print row The reader function creates a reader object to iterate over lines in the opened CSV file The reader object retrieves each element of a row by splitting it using the delimiter You can access each line of the file by iterating over the object using the for loop as displayed in the preceding code snippet or use the next method every time you want to access the next line On execution of the previous code you will be able to see three separate array lists that are printed with three individual elements Tip To open the CSV files externally you can use a spreadsheet program such as Microsoft Excel OpenOffice Calc or Apple Numbers Storing Arduino data in a CSV file In the previous two sections you learned methods to store values in a CSV file Although the data required for the file was already initialized in the code the same code could be modified to store Arduino input data To begin with storing Arduino data let s create a circuit that produces these values for us We used a motion sensor in the project of Chapter 3 The First Project Motion triggered LEDs and a potentiometer in the exercise of Chapter 4 Diving into Python Arduino Prototy
224. est POST data data postResult connection getresponse print postResult elif msg topic Arduino humidity data humidity msg payload connection request POST data data postResult connection getresponse print postResult else pass connection close Once you have performed the appropriate modifications such as changing the IP address of the Mosquitto broker and the web py application go to the next exercise before running the code Extending the MQTT Gateway using web py The MQTT Gateway code provides the user interface with the sensor information using the web py based web application The code is quite similar to what you implemented in exercise 3 The program file is named GatewayWebApplication py and located in your Exercise 4 MQTT gateway code folder In this application we have removed the sensor selection process by simply implementing a button displayed as Refresh This application waits for the POST message from the previous program which will be received on the http lt ip address gt 8080 data URL ultimately triggering the data class The POST method in this class will split the received string to identify and update the value of the humidity and motion global sensor variables class data def POST self global motion humidity i web input data web data data data split if data 0 humidity humidity data 1 elif data 0 motion motion data 1 els
225. ested in gaining experience with hardware domain this book will help you to get started If you are a hardware engineer who wants to learn advance software features this book can help you to begin with Conventions In this book you will find a number of text styles that distinguish between different kinds of information Here are some examples of these styles and an explanation of their meaning Code words in text database table names folder names filenames file extensions pathnames dummy URLs user input and Twitter handles are shown as follows While assigning the value to the weight variable we didn t specify the data type but the Python interpreter assigned it as an integer type int A block of code is set as follows Blink Turns on an LED on for one second then off for one second repeatedly This example code is in the public domain Pin 13 has an LED connected on most Arduino boards give it a name int led 13 the setup routine runs once when you press reset void setup initialize the digital pin as an output pinMode led OUTPUT the loop routine runs over and over again forever void loop digitalwrite led HIGH turn the LED on HIGH is the voltage level delay 1000 wait for a second digitalwrite led LOW turn the LED off by making the voltage LOW delay 1000 wait for a second Any command line input or output is written as follows
226. et status message You can change the program flow to accommodate any other feature you want to add at the Python level The logic behind identifying and toggling the appliance can be improvised to accommodate more complex tweet text Setting up the Twitter application We are assuming that you have a Twitter account by now If you don t you can create a new account just for this project to avoid changes to your own profile With the introduction of the latest APIs Twitter requires you to authenticate using OAuth before accessing any information from your account To do that you will have to create a Twitter app using your account Execute the following steps in order to create a new Twitter app for this project 1 Log in to your Twitter account and open the https apps twitter com address in your web browser 2 Click on the Create New App icon on the page and you will be directed to a page asking for your application details as displayed in the following screenshot Application details Name Description Website Callback URL 3 Fill in all the required details marked with red asterisks and continue to the next page Ensure that your application name is unique as Twitter asks for a unique application name 4 Once your application is created you can click on the APT Keys tab and find the consumer key API key and consumer secret API secret for your app Save this information in a safe place as you will
227. ethod to upload any sketch in the future Implementation of the Firmata protocol requires the latest version of the Firmata firmware and you don t have to worry about writing it The latest Arduino IDE ships with a standard version of the Firmata firmware and we recommend that you use the latest IDE to avoid any conflict Now follow the following steps to upload the program to your Arduino board 1 As shown in the following screenshot open the StandardFirmata sketch by navigating to File Examples Firmata StandardFirmata in the Arduino IDE Arduino File Edit Sketch Tools Help New RN Open KO Sketchbook gt 01 Basics Close RW 02 Digital gt Save ES 03 Analog gt Save As OMS 04 Communication gt Upload KU 05 Control gt Upload Using Programmer DEU 06 Sensors gt 07 Display gt Page Setup OEP 08 Strings gt Print xP 09 USB gt 10 StarterKit gt ArduinolSP EEPROM u Esplora gt Ethernet u IN Alinputsfirmata GSM u AnalogFirmata LiquidCrystal gt EchoString Robot_Control gt 12CFirmata Robot_Motor gt OldStandardFirmata SD gt ServoFirmata Servo gt SimpleAnalogFirmata SoftwareSerial gt SimpleDigitalFirmata SPI gt Stepper gt TFT G WiFi gt Wire gt 2 This action will open another sketchbook in a new window with the StandardFirmata sketch loaded in the editor Do not modify anything in the sketch and go ahead with the compiling process that is described in the next
228. etup Ctrl Shift P Print Ctrl P Preferences Ctrl Comma Quit Ctrl Q Arduino Uno on COMG You will be prompted with an empty text editor The text editor supports standard features that is copy paste select find replace and so on Before we go ahead with an Arduino program let s explore the other tools provided by the IDE Note The Arduino IDE version prior to 1 0 used the pde extension to save sketchbooks Starting from 1 0 they are saved with the ino extension You can still open files with the pde extension in the latest IDE Later the IDE will convert it to the ino extension when you save them Working with libraries The Arduino IDE uses libraries to extend the functionalities of existing sketches Libraries are a set of functions combined to perform tasks around a specific component or concept The majority of the built in Arduino libraries provide methods to start working with external hardware components You can import any library by navigating to Sketch Import Library as shown in the following screenshot ES sketch_nov0a Arduino 1 0 5 File Edit Tools Help Verify Compile Ctrl R sketch Show Sketch Folder Ctrl K Add File Import Library Add Library EEPROM Esplora Ethernet Firmata GSM LiquidCrystal Robot_Control Robot_Motor SD Servo SoftwareSerial SPI Stepper TFT WiFi Wire You can also use a library for your sketch by just specifying the library with the in
229. eturn celsius The getTemperature function returns the temperature values in Celsius which is then sent to the serial port Interfacing the humidity sensor Although the humidity sensor provides the analog output it is not straightforward to obtain relative humidity since it also depends upon the temperature The getHumidity function calculates the relative humidity from the analog output provided by the HIH 4030 sensor The formulas to calculate the relative humidity are obtained from the datasheet and reference examples of the sensor If you are using a different humidity sensor please make sure that you change the formulas accordingly as they may change the results significantly float getHumidity float degreesCelsius caculate relative humidity float supplyVolt 5 0 Get the sensor value int HIH4030_Value analogRead HIH4030_Pin convert to voltage value float voltage HIH4030_Value 1023 supplyVolt convert the voltage to a relative humidity float sensorRH 161 0 voltage supplyVolt 25 8 float trueRH sensorRH 1 0546 0 0026 degreesCelsius return trueRH As we are calculating relative humidity the returned humidity values are sent to the serial port with percentage as the unit Interfacing the light sensor To interface the BH1750 light sensor we will use the BH1750 Arduino library which we used earlier Using this library the ambient light value can be directly obtai
230. ey that AWS stores and a private key file that you store Together they allow you to connect to your instance securely For Windows AMis the private key file is required to obtain the password used to log into your instance For Linux AMis the private key file allows you to securely SSH into your instance Note The selected key pair will be added to the set of keys authorized for this instance Learn more about removing existing key pairs from a public AMI Choose an existing key pair Select a key pair No key pairs found No key pairs found You don t have any key pairs Please create a new key pair by selecting the Create a new key pair option above to continue cane As shown in the previous screenshot select Create a new key pair from the first drop down menu while providing a name for the key pair Click on the Download Key Pair button to download the key The downloaded key will have the name that you provided in the previous option with the pem extension If you already have an existing key you can select the appropriate options from the first drop down menu You will need this key every time you want to log in to this instance Save this key in a safe place Once again click on the Launch Instances button to finally start the instance Your virtual instance is launched on AWS now and it is running in the EC2 Now click on the View Instance button that will take you back to the EC2 console window You will be able to see
231. f use and availability You can replace these components according to their availability at the time you are building this project or your familiarity with other sensors Just make sure that you take care of modifications in the circuit connections and code if these new components are not compatible with the ones that we are using In the first stage of prototyping we will need components to develop the electronic circuit for the thermostat unit As we mentioned earlier we are going to measure temperature humidity and ambient light through our unit We already learned about the temperature sensor TMP102 and the ambient light sensor BH1750 in Chapter 4 Diving into Python Arduino Prototyping We will be using these sensors for this project with the humidity sensor HIH 4030 The project will utilize the same Arduino Uno board that you have been using throughout the previous chapters with the necessary cables We will also need two push buttons to provide manual inputs to the unit The summary of the required components for the first stage is provided in the following table Push button switch ttps www sparkfun com products 97 1 kilo ohm resistor p 10 kilo ohm resistor Although the table provides links for few specific website you can obtain these components from your preferred providers The two major components HIH 4030 humidity sensor and push button switch that we haven t used previously are described as follows e HIH 4030 humidity
232. ference link Working with the breadboard broker o about MOTT A lightweight messaging protocol built in functions o about Built in functions o conversion methods Conversions o math operations Math operations o string operations String operations o URL String operations built in types o about Python operators and built in types Built in types o data structures Data structures Button widget o about Learning Tkinter for GUI design The Button widget interfacing GUI with Arduino and LEDs o using The Button widget interfacing GUI with Arduino and LEDs buzzer o using Buzzer generating sound alarm pattern o connections Connections o Python code The Python code byte data type o about Data types callback o about The Label widget monitoring I O pins Carriots o about Carriots char data type o about Data types Checkbox widget o about Learning Tkinter for GUI design Checkbutton widget o about The Checkbutton widget selecting LEDs o used for selecting LEDs The Checkbutton widget selecting LEDs Client class o about The Client class close method o used for closing file The close method comments o about Comments o block comment Comments o single line or inline comment Comments computer networking o about Arduino and the computer networking IP address obtaining Obtaining the IP address of your computer networking ex
233. first change you want to replace the part address of TMP102 0x48 with the one of BH1750 0x23 in the following code snippet You will also have to convert the raw values received from the sensor into the 1ux value using the given formula After these modifications run the following program from the terminal import time from PyMata pymata import PyMata port PyMata COM5 port i2c_config port ANALOG 4 5 Request BH1750 to send 2 bytes port i2c_read 0x23 0 2 port I2C_READ Wait for BH1750 to send the data time sleep 3 Read data from BH1750 data port i2c_get_read_data 0x23 Obtain lux values from received data LuxSum data 1 lt lt 8 data 2 gt gt 4 lux LuxSum 1 2 print str lux lux firmata close On running the preceding code snippet you will be able to see the ambient light sensor reading in lux at the terminal This process can be used in a large number of I2C devices to read the registered information In complex I2C devices you will have to follow their datasheet or examples to organize the read and write commands of the I2C Useful pySerial commands The standard Firmata protocol and Python s Firmata libraries are very useful for testing or quick prototyping of the I2C sensors Although they have many advantages Firmata based projects face the following disadvantages e Delay in real time execution Firmata based approaches require a series of serial communication messages
234. form to serve sensor data At the end of this chapter you should be able to design and develop full stack IoT applications using Arduino Python and the cloud Getting started with the IoT Long before the Internet sensor and actuator based electronic control systems existed in high tech automation systems In those systems sensors were interfaced to the microcontroller via hard wired connections Due to extensibility limitations the coverage area of these systems was geographically restricted Examples of these high tech systems included factory automation satellite systems weapon systems and so on In most cases the sensors used in these systems were huge and the microcontrollers were also limited by their low computational capabilities With recent advancements in technology especially in the semiconductor industry the physical size of sensors and microcontrollers has significantly reduced It has also been made possible to manufacture low cost and highly efficient electronic components hence today it is relatively inexpensive to develop small and efficient sensor based hardware products Arduino and Raspberry Pi are great examples of these achievements These sensor and actuator based hardware systems interface with the physical world that we live in The sensors measure various elements from the physical environment while the actuators manipulate the physical environment These types of hardware based electronic systems are also kno
235. from the Arduino board board get_firmata_version e exit We recommend that you disconnect the Arduino board from pyFirmata once you have completed running your code This will free the serial port which can be then utilized by other programs board exit Upcoming functions The pyFirmata library is currently under development and it continuously receives updates to add and improve various methods Although most of the native Arduino methods are available in the pyFirmata library via the Firmata protocol there are few functions that are still missing or under development and they are as follows e pulseIn pulse0ut These native Arduino functions wait for the Arduino pin to achieve the specified value The waiting period is returned in microseconds This method is widely used by Ping ultrasonic distance measurement sensors Implementation of this method using pyFirmata requires major changes to the standard Firmata protocol e shiftIn shiftout These functions shift a byte of data in or out one bit at a time The pyFirmata library lacks supports for these functions and can be implemented using the various Python programming tricks Prototyping templates using Firmata The goal of this section is to provide prototyping templates while also explaining various Python methods and programming techniques It tries to cover some of the most popular sensors with coding examples that are used by DIY Arduino projects This section is desig
236. from your computer If you are using Mac OS X or Ubuntu an SSH client program already exists within your operating system For Windows you can download the PuTTY SSH client from http www putty org From the EC2 management window retrieve the public IP address of your instance To use the default SSH client in the Linux or Mac environment open the terminal and navigate to the folder where you have saved your key file with the pem extension In the terminal window execute the following command to make your key accessible chmod 400 test pem Once you have changed permission for your key file run the following command to log in to the virtual instance In the command you will have to replace lt key name gt with the file name of your key and lt public IP gt with the public IP that you retrieved from the management console ssh i lt key name gt pem ubuntu lt public IP gt Once you execute this command you will be asked to continue with the connection process if you are authenticating the instance for the very first time At the prompt write yes and press Enter to continue On successful authentication you will be able to see the command prompt of your virtual instance in the same terminal window In case you are using the Windows operating system and are not sure about the status of your SSH client select your instance in the EC2 window and click on the Connect button in the top navigation bar which is displayed in the fo
237. g and downloading tasks In this exercise we want to create an Arduino program where we can upload data from the connected sensors the PIR motion sensor and the HIH 4030 humidity sensor while retrieving the value to control the LED Open the Arduino sketch XivelyLibAdvance ino which contains the code that demonstrates both the functionalities As you can see in the following code snippet we have defined three separate channels for each component while having independent XivelyDatastream objects for upload datastreau and download datastreamD Similarly we have also created two different feeds feedU and feedD The main reason behind delegating the upload and download tasks to different objects is to independently update the value of the LED channel while uploading the data stream for channels HumidityRaw and MotionRaw char ledId LED char humidityId HumidityRaw char pirId MotionRaw int ledPin 2 int pirPin 3 XivelyDatastream datastreamU XivelyDatastream humidityId strlen humidityId DATASTREAM_FLOAT XivelyDatastream pirId strlen pirId DATASTREAM_FLOAT J XivelyDatastream datastreamD XivelyDatastream ledId strlen ledId DATASTREAM_FLOAT J XivelyFeed feedU lt Your feed ID gt datastreamU 2 XivelyFeed feedD lt Your feed ID gt datastreamD 1 In the 1oop function of the Arduino code we periodically fetch the current value of the LED channel from feedD and then
238. g command on the terminal python Thermostat_Stagel py This will execute the Python code and you will be able to see the GUI window on the screen Using pySerial to stream sensor data in your Python program As described in the software flow the program receives the sensor data from the Arduino using the pySerial library The code that declares the serial port in the Python code is as follows Import serial port serial Serial COM5 9600 timeout 1 It is very important to specify the timeout parameter while using the pySerial library as the code may have an error if timeout is not specified Designing the GUI using Tkinter The GUI for this project is designed using the Tkinter library that we used earlier As a GUI building exercise three columns of labels labels to display the sensor type the observation values and observation units are programmed as shown in the following code snippet Labels for sensor name Tkinter Label top text Temperature grid column 1 row 1 Tkinter Label top text Humidity grid column 1 row 2 Tkinter Label top text Light grid column 1 row 3 Labels for observation values TempLabel Tkinter Label top text TempLabel grid column 2 row 1 HumdLabel Tkinter Label top text HumdLabel grid column 2 row 2 LighLabel Tkinter Label top text LighLabel grid column 2 row 3 Labels for observation unit TempUnitLabel
239. g getifaddr eno If you are connected to multiple networks and are not aware of the network name you can find the list of IP addresses associated with your computer using the command shown here ifconfig grep inet As you can see in this screenshot you will get all the network addresses associated with your Mac computer and other network parameters GS test bash 76x8 Tests Mac test ifconfig grep inet inet6 1 prefixlen 128 inet 127 0 0 1 netmask 0xff000000 inet6 fe88 1 1o8 prefixlen 64 scopeid 0x1 inet6 fe80 20c 29ff fel4 2dc3 en prefixlen 64 scopeid 0x4 inet 192 168 110 130 netmask Oxffffff00 broadcast 192 168 110 255 Tests Mac test Linux On the Ubuntu OS you can obtain the IP address of your computer from the Network Settings utility To open it navigate to System Settings Network and click on the adapter through which the computer is connected to your home network You can select an appropriate adapter to obtain the IP address as displayed in the following screenshot Network Connected jP Wired Hardware Address em mm er Network proxy Security WPA WPA2 Strength Good Link speed 26 Mb s IP Address 10 0 0 41 Default Route 10 0 0 1 DNS 75 75 75 75 75 75 76 76 Forget Network Settings In a Linux based system there are multiple ways of obtaining the IP address from the command line You can use the same command ifconfig that we used in Mac OS X in the Linux
240. g to work on this missing link and develop various applications to provide Internet connectivity to the exercises To perform this operation we are going to utilize a commercial cloud platform in the first section and develop our customized platform in the later section As the focus of this chapter is going to be on cloud connectivity we are not going to develop a hardware circuit for each exercise We will go through the hardware design exercise only once and keep using the same hardware for all the programming exercises Similarly we will also reuse the web py programs that we developed in the previous chapter to focus on code snippets that are associated with Python libraries to develop cloud applications Hardware design Let s begin by developing standard hardware for all the upcoming exercises We will need the Arduino board that is attached to the Ethernet Shield to use the Ethernet protocol for network connectivity In terms of components you will be using simple sensors and actuators that you already used in the previous coding exercises We will use the PIR motion sensor and the HIH 4030 humidity sensor to provide digital and analog outputs respectively We will also have an LED as part of the hardware design and this will be used in coding exercises as an actuator For more information regarding the properties and detailed explanations of these sensors you can refer to previous chapters To begin assembly of the hardware components
241. gh we are using some example appliances to control the use of the relay you can select any other appliance you own You can also use a commercial power strip instead of an individual power plug Hardware design While assembling the hardware components as displayed in the following diagram make sure you are precise in connecting the appliances with the AC power plugs One wire of the AC plug is directly connected to the appliance while the other is connected between the C and NO ports of the relay We have connected the control side of the relay to the digital pin of our Arduino As we are using a four channel relay we will have to utilize four digital IO pins from the Arduino board Complete the remaining connections as shown here 110 V ae gt his Be AC power k L a M plugs ss LS Arduino Ad Ve ee ld Ethernet shield 1 SS G ww BABBEEEEE ZEEZZZZZZZZZZZZ ZZ s o flo sosse soser s sosok soose o o Connecting the hardware unit is fairly simple but requires a lot of precision because it involves high power AC connections Tip You should cover the open 110V AC power cords going to the relay and the appliance with electric tape to avoid any type of electrical hazard Keeping these live wires open can be really dangerous due to the large amount of current being carried by them In the deployment stage a plastic cover or a box around the relay unit can also be helpful in cover
242. global variable as well as in a file in case we need to run the code again with open lastTweetID txt w as fh lastTweetId fh readline print Initializing with ID lastTweetId We retrieve the ID of the previous tweet from the lastTweetID txt file to match with the latest ID If it doesn t match we update the lastTweetID txt file with the latest ID for the next loop if lastTweetId str currentStatus id lastTweetId str currentStatus id print Updated file with ID lastTweetId with open lastTweetID txt w as fh fh write lastTweetId currentStatusText currentStatus text print currentStatusText Once we have identified the latest unique tweet we use the Python string operation to decode the keywords for the appliance and power commands As you can see in the following code snippet the keyword we are looking for in the tweeted text to access the fan is fan Once we have identified that the message is directed to the fan we check for action keywords such as on and Hoff and then take the associated action of publishing the message to the Mosquitto broker We repeat this action for all the appliances connected to the system Your Arduino takes an action using the published message and completes the UX flow for the controlled appliances if fan in currentStatusText lower if on in currentStatusText lower cli publish PowerStrip fan on if off in currentStatusText lower cli publish
243. gt gt gt age 14 gt gt gt if age lt 18 and age gt 12 print Teen elif age lt 13 print Child else print Adult This will result in Teen being printed on the interpreter The for statement Python s for statement iterates over the elements of any sequence according to the order of the elements in that sequence gt gt gt celsius 13 21 23 8 gt gt gt for c in celsius print Fahrenheit str c 1 8 32 This will result in the Python interpreter generating the following output that will display the calculated Fahrenheit values from the given Celsius values Fahrenheit 55 4 Fahrenheit 69 8 Fahrenheit 73 4 Fahrenheit 46 4 The while statement The while statement is used to create a continuous loop in a Python program A while loop keeps iterating over the code block until the condition is proved true gt gt gt count 5 gt gt gt while count gt 0 print count count count 1 The while statement will keep iterating and printing the value of the variable count and also reduce its value by 1 until the condition that is count gt becomes true As soon as the value of count is lower than or equal to 0 the while loop will exit the code block and stop iterating The other compound statements supported by Python are try catch and with These statements will be explained in detail in the upcoming chapters Python also provides loop control statements such as break
244. h Note Although we are running individual scripts at the Python prompt we will be going through the process of creating Python executable files in the next chapter Summary By introducing the Firmata library we avoided writing any custom Arduino sketches in this chapter We will continue this practice during the remaining part of this book and will only use or make custom sketches when required In this chapter you interacted with the Arduino board by making the LED blink which is the easiest way to get started on a hardware project Now it s time for your first project where we are also going to make some more LEDs blink One might ask the question that if we have already done it then why do we need another project to make LEDs blink Let s find out Chapter 3 The First Project Motion triggered LEDs In the preceding chapter you learned the basics of Python Arduino interfacing We went through some exercises to provide hands on experience with a useful Arduino protocol Firmata and the Python library Now it s time for your first Python Arduino project We will start this chapter by discussing the project goals and the required components to design the software flow and the hardware layout for the project Just like any other microcontroller based hardware project you can use code and implement the entire logic of your project on Arduino itself However the goal of this book is to help you to utilize Python in suc
245. h a way that you can simplify and extend your hardware projects Although we will be using a hybrid approach with a Python program assisted by an Arduino sketch in the upcoming chapters we would like you to get familiar with both ways of programming As this is your first experience of building a hardware project the chapter provides you with two different programming methods for the project just using an Arduino sketch and using a Python program with the Firmata protocol on Arduino The method with the Arduino sketch is included so that you get the complete experience with the Arduino components such as I O pins and serial communication Motion triggered LEDs the project description When you start learning any programming language in most cases you will be writing code to print Hello World Meanwhile in hardware projects the majority of tutorials begin by helping a user to write the code to blink an LED These exercises or projects are useful for developers to get started with the language but mostly they do not carry any importance towards real world applications However we don t want to overwhelm you with a complex and sophisticated project that might require you to have a good amount of domain knowledge While working with the Firmata protocol in the previous chapter we already blinked an LED on the Arduino board To keep the tradition alive of having a blinking LED as a first major project and also build excitement toward
246. h as designers artists and students The Arduino language is implemented in C C while the fundamentals of the sketch and program structures are derived from an open source programming language called Processing and an open source electronic prototyping language called Wiring Comments Arduino follows a commenting format that is adopted from C and it is similar to higher level languages however it is different from the Python comment format that we learned earlier in this chapter There are various methods of commenting which are as follows e Block comment This is done by covering the commented text between and This is a comment Arduino will ignore any text till it finds until the ending comment syntax which is e Single line or inline comment This is done by using before the line This syntax only applies to one line You have to use it again for each next line of comment int pin 13 Selected pin 13 Usually a block comment at the beginning of the sketch is mostly used to describe the program as a whole Single line comments are used to describe specific functions or to do notes such as the following one TODO explain variables next Variables Like any other high level language a variable is used to store data with three components a name a value and a type For example consider the following statement int pin 10 Here pin is the variable name that is defined with the ty
247. he plot method is for the format string These parameters help users to change the style of line and markers with different colors In our example we are using the solid line style So the plot function for our plot looks like this pyplot plot x y The plot function provides a selection from a large collection of styles and colors To find more information about these parameters use Python s he1p function on the plot function of matplotlib gt gt gt import matplotlib gt gt gt help matplotlib pyplot plot This he1p function will provide the necessary information to create plotting styles with different markers line styles and colors You can exit this help menu by typing q at the prompt Now as we have explored plotting sufficiently let s create your first Python plot using the following code snippet The program containing this code is also located in this chapter s code folder with the name plotBasic py from matplotlib import pyplot import random x y range 0 25 random randint 0 100 for r in range 0 25 fig1 pyplot figure pyplot plot x y pyplot title First Plot Random integers pyplot xlabel X Axis pyplot ylabel Y Axis pyplot show In the previous exercise we randomly generated a dataset for the y axis using the randint method You can see a plot depicting this data with the solid line style in an opened window after running the program As you can se
248. he time and brightness values while using the Start and Exit buttons to perform the associated actions From the next exercise we will start using the grid method regularly to arrange the widgets The Checkbutton widget selecting LEDs While developing complex projects you will encounter scenarios where you have to depend on the user to select single or multiple options from a given set of values For example when you have multiple numbers of LEDs interfaced with the Arduino board and you want the user to select an LED or LEDs that need to be turned on This level of customization makes your interface more interactive and useful The Tkinter library provides an interface for a standard widget called Checkbutton that enables the manual selection process from the given options In this exercise we are going to work with both the LEDs green and red that you connected to the Arduino board at the beginning The entire Python program for this exercise is located in the code folder with the name exampleCheckbutton py Open the file with the same editor that you have been using all along This program implements the Checkbutton widget for users to select the red and or green LED when the Start button is clicked To understand the entire program logic let s start from the initialization and importing of the libraries As you can see now we have two pin assignments for digital pins 10 and 11 as redPin and greenPin respectively The code f
249. he value of the Xively s Buzzer channel to OFF which then get picked up by the control center and it turns off the buzzer at the monitoring station subsequently l a A e00 D 10 0 0 20 8080 x WE he C 5 10 0 0 20 8080 O8 Remote Home Monitoring System Status Normal Temperature 27 31 Humidity 48 65 Light 831 0 Motion 0 0 Refresh Buzzer Off Testing and troubleshooting Due to the number of components involved and complex programming associated with them the overall project is a complex system to test and debug Before you jump into troubleshooting make sure that you have properly followed the steps that were described in the previous sections in order The following are a few solutions to possible problems that can occur during the execution of the project e Troubleshoot individual sensor performance o If your sensor measurements are way off the expected values the first thing that you want to evaluate is the connection of the sensor pins to the Arduino board Make sure that you have connected the digital analog and PWM pins correctly o Check whether your Ethernet Shield board is properly connected to Arduino Uno o Evaluate the connections of the 5V power supply and ground for each component e Avoid Xively s update limit o Xively imposes a limit on the maximum number of transactions that you can perform in a limited amount of time While running your control center code if
250. hermostat provides an idea of the type of features that a properly designed remote monitoring system with professional features should have Achieving this level of system capabilities requires a lot of development effort from a large team Although it will be difficult to include each of the features that are supported by a commercial system in our project we will still try to implement the common features that can be incorporated by a prototype project The top level features that we are planning to incorporate in this project can be described by the following goals e Observe the physical environment and make it accessible remotely e Provide basic level controls to the user to interact with the system e Demonstrate a primitive level of built in situational awareness The project requirements Now that we have defined the major goals let s convert them into detailed system requirements On the completion of the project the system should be able to satisfy the following requirements e It must be able to observe physical phenomenon such as temperature humidity motion and ambient light e It should provide local access to sensor information and control over actuators such as a buzzer a button switch and an LED e The monitoring should be done by a unit that is developed using the open source hardware platform Arduino e The monitoring unit should be limited to collect sensor information and communicate it to the control unit e The c
251. hernet port and only had a memory of 256 MB In our project we are using the Raspberry Pi s Model B that has a dedicated Ethernet port 512 MB memory and dual USB ports The latest versions of Raspberry Pi Model B can be also used as it is also equipped with an Ethernet port Installing the operating system and configuring the Raspberry Pi Although the Raspberry Pi is a computer it is different than traditional desktop computers when it comes to interfacing peripheral devices Instead of supporting traditional VGA or DVI display ports the Raspberry Pi provides a RCA video port for TVs and an HDMI port for the latest generation of monitors and TVs In addition the Raspberry Pi has only two USB ports that need to be utilized for connecting various peripheral devices such as the mouse the keyboard the USB wireless adapter and the USB memory stick Let s get started by collecting components and cables to start working with a Raspberry Pi What do you need to begin using the Raspberry Pi The hardware components required to get started with a Raspberry Pi are as follows e A Raspberry Pi For this stage of the project you will need a Raspberry Pi version Model B or latest You can buy the Raspberry Pi from http www raspberrypi org buy e A power cable The Raspberry Pi runs on 5V DC and requires at least 750 mA current The power is applied through the micro USB port that is located on the board In this project you will need a micro U
252. his doctoral research His doctoral research was focused on developing situation awareness frameworks for IoT devices enabling semantic web based reasoning and handling the uncertainty associated with sensor data In his personal life Pratik is an avid DIY junkie and likes to get hands on experience on upcoming technologies He extensively expresses his views on technology and shares interesting developments on Twitter chheplo I would like to dedicate the book to my parents who were responsible for building the foundation of what I am today The book would not have been possible without the patience support and encouragement from my beloved wife Sachi I would also like to thank her for landing her photography skills that were used in development of some of the important images used in the book I would also like to extend my sincere gratitude to the editors for their valuable feedbacks About the Reviewers Juan Ram n Gonz lez is a technical engineer of computer systems and lives in Seville Andalusia Spain For the past 9 years he has been working on free software based projects for the regional Ministry of Education by using Python C and JavaScript among other programming languages He is one of the main members of the CGA project in Andalusia Centro de Gesti n Avanzado or Advanced Management Center which manages a network with more than 4 000 servers with Debian and 500 000 client computers that run Guadalinex a custom
253. his function in our Arduino program as described in the following code snippet attachInterrupt 0 buttoniPress RISING attachInterrupt 1 button2Press RISING The supported mode for attachInterrupt are LOW CHANGE RISING and FALLING In our case the interrupts are triggered when the mode is RISING that is the pin goes from low to high For interrupts declared at O and 1 we call the button1Press and button2Press functions that will change flagTemperature and flagPlot respectively When flagTemperature is set to HIGH Arduino sends the temperature in Celsius otherwise it sends the temperature in Fahrenheit When flagPlot is HIGH Arduino will print the flag on the serial port which will be used by the Python program later to open the plot window You can learn more about Arduino interrupts from the tutorial at http arduino cc en Reference attachInterrupt Designing the GUI and plot in Python Once your thermostat sensor unit starts sending sensor data to the serial port it is time to execute the second part of this stage the Python code for the GUI and the plot From this chapter s code folder open the Python file called Thermostat_Stage1 py In the file go to the line that contains the Serial function where the serial port is declared Change the serial port name from CoM5 to the appropriate one You can find this information from the Arduino IDE Save the change and exit the editor From the same folder run the followin
254. his project you will need four of these devices to replace the four channel relay that we are going to use As you can see in the following diagram one end of the Tail goes into the regular power port while you need to connect your appliance to the other port Meanwhile you can use the three control inputs to control the relay We are using one of the digital I O pins of the Arduino board to send the control signal to the Tail When going ahead with the Tails instead of the relays make sure that you make necessary amendments to the upcoming hardware design Towards the appliance A Let aces TT ED PowerSwitch Tail From power socket User experience flow From the system architecture we have created what should the user experience UX flow while working with the Tweet a PowerStrip be We have divided the UX into two separate sections controlling the power to the appliances and checking the status of the power strip In the first UX flow design as displayed in the following diagram the user begins by sending a tweet containing the name of the appliance fan lamp toaster or coffee and the control command on or off The system should be able to handle the tweet from the point of parsing until the appliance has behaved as asked for The system should also provide a hassle free experience for the user where the user doesn t have to perform any further actions than simply sending tweets
255. hon installing Windows Setuptools installing Windows Arduino IDE installing Windows Arduino board connection establishing Windows matplotlib configuring Configuring matplotlib on Windows SD card preparing Preparing an SD card o IP address obtaining Windows e Wire library o about Prototyping with the I2C protocol o URL Prototyping with the I2C protocol e Wiring o about Introduction to Arduino programming e with statement o using The with statement Python context manager O O O O 0 0 O O O 0 O e World Wide Web WWW o about RESTful web applications with Arduino and Python e write method o used for working with files The write method X e Xively Architecture of the cloud services e Xively IoT cloud platforms o about Xively a cloud platform for the IoT o account setting up Setting up an account on Xively o working with Working with Xively o Adruino interfacing with Interfacing Arduino with Xively
256. hown in the previous diagram or if you are comfortable you can use a PCB prototype board and solder the components In our setup we first tested the components on the breadboard and once they were tested we soldered the components as shown in the following figure If you venture to solder the PCB board make sure that you have the necessary components for the job The PCB prototype will yield a robust performance compared to the breadboard but it will also make it difficult for you to debug and change the components afterwards Light sensor i Buzzer a Arduino PIR sensor HIH4030 If you are ready with your circuit connection connect your Arduino to your computer using the USB cable Also connect the Ethernet Shield to your home router using an Ethernet cable The Arduino sketch for the monitoring station Before jumping into the coding stage make sure that you have collected the prebuilt Arduino code for the project You can find it in the code folder of this chapter with the filename Arduino_monitoring_station ino The code implements the necessary logic to support the overall UX flow at the monitoring station which we discussed in the previous section In the following sections we will go through the major areas of the program so that you can better understand these code snippets Now open this sketch in the Arduino IDE You are already familiar with setting up the IP address for Arduino You also learned how to us
257. humidity values The second push button also utilizes a similar method of using flags to capture the input and opens a new plot window If the same button is pushed sequentially the program will close the plot window Stage 1 prototyping the thermostat In this prototyping stage we will develop the Arduino and Python code for our thermostat which will be later used in the second stage with minor changes Before you start the coding exercise make sure that you have the thermostat sensor unit ready with the Arduino board and the connected sensors as described in the previous section For this stage you will be using your regular computer which is equipped with the Arduino IDE and the Python programming environment The prototyping stage requires two levels of programming the Arduino sketch for the thermostat sensor unit and the Python code for the computational unit Let s get started with coding for our thermostat The Arduino sketch for the thermostat The goal of this Arduino program is to interface sensors get measurements from the sensors and print them on the serial port As we discussed earlier rather than using the standard Firmata sketch that we used in the previous project we are going to develop a custom Arduino sketch in this project To get started open the Thermostat_Arduino ino sketch from this chapter s code folder which is part of the source code that you received for the book Connect the USB port of the Arduino boar
258. iances and once it receives an appropriate message it executes the action on the relay level In the second stage we deal with the individual tweets where we parse the tweets from the Twitter account check for duplicates decode actions from the messages and also post tweets with status reports During these development stages we are going to use a breadboard and jumper wires to test the Arduino and Python programs At this stage the project is still not ready to deploy as a portable unit for daily usage The deployment stage contains tasks of creating a PCB for the breadboard connections and insulating wires to avoid any electric hazard You can also buy or create an enclosure box to isolate the open hardware from physical contact As the development stage contains everything that is required to convert the project into its working state we are not going to dive deep into the deployment stage You can perform addition deployment tasks according to your personal requirements Let s start from the hardware design stage and develop the physical section of the smart power strip using Arduino Stage 1 a smart power strip with Arduino and relays The hardware of Tweet a PowerStrip contains Arduino as the main controller unit that interfaces with the relays and the Ethernet Shield to communicate with the computation unit The Arduino code implements the MQTT client using the PubSubClient library to publish and subscribe to the topics Althou
259. ications as they can provide information regarding the system s behavior for better understanding of the data This chapter is organized around two major sections storing the Arduino sensor data and plotting this data We will start by creating and manipulating files using Python After that we will work with methods for storing Arduino data in the CSV file format In the second section you will be introduced to the Python plotting library matplotlib Then we will work with examples that deal with plotting data from a saved file and also from real time sensor readings In the end we will try to integrate the matplotlib plots with the Tkinter window that we created in the previous chapter In terms of hardware components we will be working with familiar sensors such as a potentiometer and the PIR motion sensor which we used in the previous chapters so you will not have to learn or buy any additional sensors for this chapter Working with files in Python Python provides built in methods to create and modify files File related Python operations are useful in a large number of programming exercises These methods are provided by standard Python modules and do not require installation of additional packages The open method The open method is a default method that is available in Python and it is one of the most widely used functions to manipulate files Now the first step of dealing with a file is to open it gt gt gt f o
260. ient tools to start developing IoT applications the functionalities of the platform will be confined to the supplied feature set To have complete control over customization you may have to use the next option If you want to separately install and configure the necessary software tools here s what you need to remember e This option includes furnishing project specific software tools such as Python and the Mosquitto broker with the required Python libraries such as web py and paho_mqtt e We have already worked with exercises that implemented applications which were based on the Mosquitto broker and web py This version of the custom IoT cloud platform can reduce the complexity of installing additional open source platform tools and still provide the necessary support to host applications e The Arduino program can directly communicate with this custom platform using REST or MQTT protocols It can also behave as the remote computation unit to communicate with Xively or other third party IoT cloud platforms In the next section we will begin the platform deployment process by installing the Mosquitto broker and the necessary packages on your virtual instance This will be followed by the configuration of the virtual instance to support the MQTT protocol Once your IoT cloud platform is up and running you can just run the Python based Mosquitto code from the last chapter from the instance with minor or no modifications In future this IoT pl
261. ill be handy for the upcoming coding exercises The with statement Python context manager Although the with statement can be used to cover the execution of a code block that is defined by a context manager it is widely used in Python to deal with files Execute the following command on the Python interactive prompt assuming that you have already executed the previous commands and have the test txt file with some data gt gt gt with open test txt r as f lines f readlines for 1 in lines print 1 On execution you will be able to see each line of the file printed on the command prompt The with statement while used with the open method creates a context manager which executes the wrapped code while automatically taking care of closing the file This is the recommended method to work with files in Python and we will be utilizing it in all of our exercises You can learn more about the Python context manager on the following websites e https docs python org 2 reference compound_stmts html with e http preshing com 20110920 the python with statement by example Using CSV files to store data Now you know methods to open manipulate and close files using Python In the previous examples we used the Python interpreter and string data to get familiar with these methods But when it comes to saving a large number of numerical values from sensor data the comma separated values CSV file format is one of the most widel
262. ill have to change the values for account specific parameters that is the API key feed ID and so on Before you go ahead and upload this sketch go to the Xively platform and create a channel called LED with Current Value as 1 as displayed in the following screenshot Add Channel o LED Tags Units Symbol Current Value E Save Channel Cancel 6 Now compile and upload the code to your Arduino 7 Once you have uploaded the compiled code to your Arduino open the Serial Monitor window and wait for an output that is similar to the one displayed in following screenshot You will notice that the LED on the Arduino hardware is turned on 600 dev tty usbmodemfa1331 Reading from Xively example xivelyclient get returned 209 Datastream is id LED current value 1 00 LED value is 1 00 xivelyclient get returned 209 Datastreom is id LED current_value 1 00 LED value is 1 09 A v M Autoscroll No line ending 4 9600 baud 93 8 You can go back to the Xively LED channel and change the Current Value field to o Within a few seconds you will notice that the LED on the Arduino hardware is turned off With this exercise you have successfully established two way communication between Arduino and the Xively platform Advanced code to upload and download data using Arduino In the previous two Arduino exercises we individually performed the uploadin
263. imple and straightforward process The web py library requires the declaration of a mandatory method GET to successfully start the web server When a client tries to access the server using a web browser or another client web py receives a GET request and returns data as specified by the method To create a simple web application using the web py library create a Python file using the following lines of code and execute the file using Python You can also run the webPyBasicExample py file from the code folder of this chapter import web urls index class index def GET self return Hello world if _ name__ _ main__ app web application urls globals app run On execution you will see that the server is now running and accessible through the http 0 0 0 0 8080 address As the server program is running on the 0 0 0 0 IP address you can access it using the same computer localhost or any other computer from the same network To check out the server open a web browser and go to http 0 0 0 0 8080 When you are trying to access the server from the same computer you can also use http 127 0 0 1 8080 or http localhost 8080 The 127 0 0 1 IP address actually stands for localhost that is the network address of the same computer on which the program is running You will be able to see the response of the server displayed in the browser as shown in the following screenshot e00 localhost 8080
264. in program logic These custom functions can then be called from any part of the sketch to perform a specific task Functions help programmers to simplify debugging to reduce chances for error and to organize coding concepts void blinkLED action A action B The Arduino language has a set of library functions to simplify the programming experience Although not all of these library functions are required by an Arduino sketch setup and loop are mandatory functions and they are required to successfully compile the sketch The setup function When Arduino runs a sketch it first looks for the setup function The setup function is used to execute important programming subroutines before the rest of the program such as declaring constants setting up pins initializing serial communication or initializing external libraries When Arduino runs the program it executes the setup functions only once If you check out the Blink sketch that we used in the previous section you can see the initialization of the setup function as displayed in the following code snippet void setup initialize the digital pin as an output pinMode led OUTPUT As you can see in our example we used the pinMode function to assign the role of the LED pin in the setup function The loop function Once Arduino has executed the setup function it starts iterating the loop function continuously While setup contains th
265. ing a local instance of the Mosquitto broker you can replace the IP address with 127 0 0 1 Otherwise replace the 10 0 0 18 address with the appropriate IP address of the computer that is hosting the Mosquitto broker Let s try to understand the code now Note Sometimes on Mac OS X you won t be able to run Tkinter window and Python threads in parallel due to an unknown bug You should be able to execute the program successfully in Windows and Linux environments This program has been tested with the Raspberry Pi which means you won t encounter the same bug while deploying the control center Creating the GUI using Tkinter In the previous exercises we always used a single Python thread to run the program This practice will not help us to perform multiple tasks in parallel such as obtaining sensor observation from the monitoring station and simultaneously updating the GUI with that information As a solution we have introduced multithreading in this exercise As we need two separate loops one each for Tkinter and paho mqtt we will be running them independently in separate threads The main thread will run methods that are related to Mosquitto and the cloud services while the second thread will handle the Tkinter GUI In the following code snippet you can see that we have initialized the controlCenterWindow class with the threading thread parameter Therefore when we execute window controlCenterWindow in the main program it wi
266. ing applications using these connected sensors In this chapter we will learn the last step in the development of a full stack IoT application enabling access for your Python Arduino application through the Internet Now let s try to first understand the architecture of the IoT Architecture of IoT web applications In this book we have covered three major concepts in the first eight chapters e Physical layer We used various sensors and actuators with the Arduino board to deal with the physical environment The sensors such as the temperature sensor humidity sensor and motion sensor were used measured the physical phenomenon while the actuators such as LEDs were utilized to alter or produce physical elements e Computation layer We used Arduino sketches and Python programs to convert these physical elements into numerical data We also utilized these high level languages to perform various computations such as calculating relative humidity developing user interfaces plotting data and providing web interfaces e Interfacing layer Throughout the material that we covered we also utilized various interfacing methods to establish communication between Arduino and Python For interfacing part of the interfacing layer between the physical and computation layers we used serial port libraries established network based communication using the REST and MQTT protocol and developed web applications As you can see we have developed applica
267. ing the client using the IP address of the server Mosquitto port number and Ethernet client Before using any other method for the PubSubClient library you will always have to initialize the MQTT client using a similar method EthernetClient ethClient PubSubClient client server 1883 callback ethClient Further on in the code we are using the publish and subscribe methods on the client class to publish a message for the outTopic topic and subscribe to the inTopic topic You can specify the name of the client using the client connect method As you can see in the following code snippet we are declaring arduinoClient as the name for this client Ethernet begin mac ip if client connect arduinoClient client publish outTopic hello world client subscribe inTopic As we are using this code in the setup function the client will only publish the hello world message once during the initialization of the code while the subscribe method will keep looking for new messages for inTopic due to the use of the client loop method in the Arduino loop function client loop Now while running Mosquitto in the background open another terminal window In this terminal window run the following command This command will use a computer based Mosquitto client to subscribe to the outTopic topic mosquitto_sub t outTopic Compile your Arduino sketch and upload it As soon as the upload process is com
268. ing the live power wires Once you are ready with the connections connect the Arduino board to your computer using a USB port as shown in the following image The Arduino code The Arduino sketch for this section is located in the folder containing the chapter code with the Arduino_powerstrip ino filename You can open the file in the Arduino IDE to explore the code As usual you will have to change the IP addresses of the device and the Mosquitto server to the appropriate IP addresses while also changing the MAC address of the Ethernet Shield The following code snippet shows the declaration of the Arduino pins and their roles in the main function setup Make sure that you are using the same pin numbers that you have used to connect the relay Alternatively you can change the appliance name to that of the appliance you are using Also make sure whatever changes you make in the variable names should be reflected in the entire code to avoid any compilation errors pinMode FAN OUTPUT pinMode LAMP OUTPUT pinMode TOASTER OUTPUT pinMode COFFEEMAKER OUTPUT fanStatus false lampStatus false toasterStatus false coffeemakerStatus false digitalwrite FAN LOW digitalwrite LAMP LOW digitalwrite TOASTER LOW digitalwrite COFFEEMAKER LOW In the setup function the code also subscribes to the appropriate MQTT channels so that it can receive messages from the Mosquitto broker as soon as they are available
269. ino NG or older w ATmegad Arduino Robot Control Arduino Robot Motor Select Arduino Uno from the list of boards unless you are using a different Arduino board Once you have selected the board you can go ahead and compile the sketch You can compile the sketch by navigating to Sketch Verify Compile from the menu bar or by using the keyboard shortcut Ctrl R If everything is set up well you should be able to compile the code without any error After successfully compiling the sketch it is time to upload the compiled code to the Arduino board To do this you need to make sure that your Arduino IDE is properly connected to your computer If it is not already connected connect your Arduino board to your computer using a USB port Now it is time to let your IDE know the serial port on which the board is connected Navigate to Tools Serial Ports and select the appropriate serial port Note In the case of some Linux distributions you may not be able to see or upload the Arduino program to the board due to permission restriction s on the serial port Running the following command on the terminal should solve that problem sudo usermod a G uucp dialout lock lt username gt You can now upload the compiled sketch to your Arduino board by navigating to File Upload This process will use the serial connection to burn the compiled firmware in the microcontroller Please wait for some time or until the LEDs Tx and Rx LED
270. ions are followed correctly let s open the Python interpreter by executing the Python command at the terminal or the command prompt You should get results similar to those displayed in the following screenshot If you have installed Python by downloading the setup files from the website you should have the Python integrated development environment IDLE installed as well You can also start the Python interpreter by opening its IDLE from the location where it was installed As you can see after printing some system information the interpreter opens a prompt with three greater than signs gt gt gt which is also known as the primary prompt The interpreter is now in the interactive mode and it is ready to execute scripts from the prompt C Windows system32 cmd exe python Microsoft Windows Version 6 1 7681 Copyright c gt 2869 Microsoft Corporation All rights reserved G Users Test gt python Python 2 7 5 default May 15 2813 22 43 36 MSC v 1588 32 bit lt Intel gt on win 32 Type help copyright credits or license for more information gt gt gt To close the interactive mode of the Python interpreter run the either exit or quit at the primary prompt Another method to exit from the interactive mode is to use the keyboard shortcut Ctrl D Note Note that Python s built in functions are case sensitive This means the following exit 4 EXITO 4 Exit The official Python website p
271. is the monitoring station and the control center As you can see from the following figure we have our first user interaction point at the control center The user can observe the information or act upon it if the system s status is an alert The user action to dismiss the alert prompts multiple operations to take place at the control center and the monitoring station We recommend you thoroughly examine the figure to better understand the flow of the system Monitoring Control isa Station Center Sense physical environment Observe status amp sensor outputs on LCD TFT screen Send sensor data to Control Center Display current system status 4 sensor outputs Obtain sensor data Temperature out of range is system on alert Set status Normal with Set LED status Green LED Humidity out of range Dismiss alert Set status Alert with Red LED and buzzer Press button switch on Monitoring station Set buzzer status OH Send buzzer off a E q qtI I2 message to Click button on GUI Monitoring station Similarly the second user interaction point is located at the web application The web application displays the observations and system s status that we calculated at the control center and provides an interface to dismiss the alert In this scenario the dismiss action will travel through Xively to the
272. it arranging widgets in the grid and so on There are definitely a lot more top level methods than the ones specified earlier The Label widget The other widget used in the code beside Tk is Labe1 The Tkinter widgets are part of the widget hierarchy where Labe1 is the child of the root widget Tk This widget cannot be called without specifying the root widget or the main window on which the label needs to be displayed The major use of this widget is to display text or image in the main window In the following line of code we use it to display the Hello World string helloLabel Tkinter Label top text Hello World Here we created and initialized a label object called helloLabe1 which has two input parameters the top variable that specifies the root widget and a text string The Label widget is highly customizable and accepts various configuration parameters for adjusting the width border background and justification as options Examples involving these customizations are covered in the upcoming sections You can learn more about the supported input arguments at http effbot org tkinterbook label htm The Pack geometry manager The Pack geometry manager organizes widgets in rows and columns To use this Tkinter requires the pack method to be called for each widget to make the widget visible on the main window helloLabel pack The Pack geometry manager can be used by all Tkinter widgets except root to
273. ith GUI and Arduino data you must have noticed that the code was updating the interface with every new value that was obtained from the Arduino sensors Similarly in this exercise we will be redrawing the plot every time we receive new values from Arduino Basically we will be plotting and updating a real time Chart instead of plotting the entire set of sensor values as we did in the previous exercise We will be using the same Arduino circuit that you built in the previous exercises Here we will utilize only the potentiometer section of the circuit to obtain the analog sensor values Now before we explain the new methods used in this exercise let s first open the program file for this exercise You can find the program file from this chapter s folder it is named plotLive py In the code change the appropriate parameters for the Arduino board and execute the code While the code is running rotate the knob of the potentiometer to observe the real time changes in the plot On running the program you will get a screen similar to the following screenshot that shows a plot from real time Arduino data Real time Potentiometer reading One can make various conclusions about the potentiometer s knob rotation or some other sensor behavior by just looking at the plot These types of plots are widely used in the graphical dashboard for real time monitoring applications Now let s try to understand the methods that are used in the following
274. itializing the Ethernet connection and setting up the IP address This means that you still need to configure Arduino as a server or a client in order to enable further communication The IPAddress class In applications where you have to manually assign the IP address to your Arduino device you will have to use the IPAddress class of the Ethernet library This class provides methods to specify the IP address which can be either local or remote depending upon the application IPAddress ip 192 168 1 177 The IP address created using this method can be used in the initialization of the network connection that we performed in the previous section If you want to assign a manual IP address to your Arduino you can use the begin mac ip method with the MAC and IP addresses Ethernet begin mac ip The Server class The Server class is designed to create a server using the Ethernet library on Arduino which listens to incoming connection requests for a specific port The EthernetServer method when specified with in integer value of the port number initializes the server on Arduino EthernetServer server EthernetServer 80 By specifying port 80 in the previous line of code which represents the HTTP protocol on the TCP IP suite we have specifically created a web server using the Ethernet library To start listening to the incoming connection requests you have to use the begin method on the server object server begin
275. itoring station the system s status and sensor observations change in real time E Control Center o x Normal Temperature 27 31 C Humidity 48 65 Light 831 0 Ix Motion No If this setup is working correctly on your computer let s move on to deploy the control center on the Raspberry Pi Setting up the control center on the Raspberry Pi The process of installing the Raspbian operating system is explained in Chapter 7 The Midterm Project a Portable DIY Thermostat You can use the same module that you used in the Midterm project or set up a new one Once you have installed Raspbian and configured the TFT screen connect the Wi Fi dongle through a USB port At this stage we assume that your Raspberry Pi is connected with a monitor a keyboard and a mouse to perform the basic changes Although we won t recommend it you can also use the TFT screen for the following operations if you are comfortable with it 1 Start your Raspberry Pi and log in At the command prompt execute the following command to enter the visual desktop mode startx 2 Once your graphical desktop starts you will be able to see the icon of the WiFi config utility Double click on this icon and open the WiFi config utility Scan for wireless networks and connect to the Wi Fi network that has the monitoring station When asked enter the password of your network in the form window called PSK and connect to your network 3 Now your Ra
276. ized Ubuntu based operating system for Andalusian schools As a software developer who has a passion for electronics and astronomy he started one of the first projects to control a telescope with the Arduino microcontroller by using a computer with the Stellarium software and a driver developed with Python to communicate with the telescope This project s sources are published on the collaborative platform GitHub You can see the whole code and the prototype at https github com juanrmn Arduino Telescope Control Marco Schwartz is an electrical engineer entrepreneur and blogger He has a master s degree in electrical engineering and computer science from Sup lec France and a master s degree in micro engineering from EPFL Switzerland Marco has more than 5 years of experience working in the domain of electrical engineering His interests gravitate around electronics home automation the Arduino and the Raspberry Pi platforms open source hardware projects and 3D printing He runs several websites around Arduino including the Open Home Automation website that is dedicated to building home automation systems using open source hardware Marco has written a book on home automation and Arduino called Arduino Home Automation Projects Packt Publishing He has also written a book on how to build Internet of Things projects with Arduino called Internet of Things with the Arduino Yun Packt Publishing Josh VanderLinden is a lifelong tech
277. ke sure that your Arduino IDE is not connected to the board using the same port number As we mentioned earlier the serial interface grants exclusive access to only one application at a time 4 Once you select the Arduino serial port the program will load multiple drop down boxes and buttons with labels that contain the pin number You can see in the following screenshot that the program is loaded with 12 digital pins from pin 2 to pin 13 and six analog pins from pin 14 to pin 19 As we are using the Arduino Uno board for our applications the test program only loads pins that are part of Arduino Uno If you are using Arduino Mega or any other board the number of pins displayed in the program will be according to the pins supported by that particular variant of the Arduino board Firmata Test Output Output Output Output Output Output Output Output Output Output Output Output Analog AO Analog Al Analog A2 Analog A3 Analog A4 Analog AS dev cu usbmodemfd1211 StandardFirmata ino 2 3 Tx 149 Rx 76522 A Tip Working with the firmata_test program on Linux On a Linux platform you might have to modify the property of the downloaded file and make it executable From the same directory run the following command in the terminal to make it executable chmod x firmata_test Once you have changed the permissions use the following command to run the program from the terminal firmata_test As y
278. l also use the same Entry widget to obtain the time interval as an input timePeriodEntry Tkinter Entry top bd 5 width 25 timePeriodEntry pack timePeriodEntry focus_set The scale widget offers a slider knob that can be moved over a fixed scale to provide a numeric value as an output The starting and the ending values for this scale are provided using the from_ and to options The orientation of this slider can also be configured using the orient option where the acceptable values for the orientation are HORIZONTAL and VERTICAL However you will have to import HORIZONTAL and VERTICAL constants from the Tkinter library before utilizing them here If no options are provided the default widget uses the scale from 0 to 100 and the vertical orientation In our program we have used the horizontal orientation as a demonstration of the orient option Once you have defined the widget object brightnessScale you will have to add it to the Pack geometry manager using pack brightnessScale Tkinter Scale top from_ 0 to 100 orient Tkinter HORIZONTAL brightnessScale pack In order to start the process and reuse the previous code we have kept the instantiation of the startButton widget and the onStartButtonPress function as it is However the property of the function is changed to accommodate the Scale widget startButton Tkinter Button top text Start command onStartButtonPress startButton pack In this ve
279. l be repeating this process to install other libraries in future Execute the following steps to import the BH1750 library to your Arduino IDE 1 Download and extract Chapter 7 The Midterm Project a Portable DIY Thermostat code examples in a folder 2 Open the Arduino IDE and navigate to Sketch Import Library Add Library 3 When you are asked for a directory go to the BH1750 folder in the downloaded file and click on Select 4 To check if your library is installed navigate to Sketch Import Library and look for BH1750 in the drop down list 5 Finally restart the Arduino IDE Tip If you are using an Arduino IDE with version 1 0 4 or an older version you might not be able to find the Import Library option from the menu In this case you need to follow the tutorial at http arduino cc en Guide Libraries The BH1750 library has a method to directly obtain ambient light values Let s test this library using a built in code example After restarting your Arduino IDE navigate to File Examples BH1750 and open the BH1750test Arduino sketch This should open the following code snippet in the Arduino IDE Set up an appropriate serial port and upload the code to your Arduino board Once the code is executed you will be able to check the luminous flux 1ux values using the serial monitor of the Arduino IDE Make sure that the serial monitor is configured to 9600 baud include lt Wire h gt include lt B
280. l port settings through Python properties and allows you to configure the serial port directly through the interpreter pySerial will be the bridge for any future communication between the Python and Arduino Let s start by installing pySerial Installing pySerial We installed the package manager Setuptools in Chapter 1 Getting Started with Python and Arduino If you have skipped that chapter and are not sure about it then please go through that section If you already know how to install and configure Python library packages skip these installation steps From this stage we are going to use only pip based installation commands due to their obvious advantages that were described in Chapter 1 Getting Started with Python and Arduino 1 Open a terminal or command prompt and execute the following command gt pip install pyserial The Windows operating system does not require administrator level user access to execute the command but you should have root privileges to install Python packages in Unix based operating systems as follows sudo pip install pyserial If you want to install the pySerial library from source download the archive from http pypi python org pypi pyserial unpack it and from the pySerial directory run the following command sudo python setup py install 2 If Python and Setuptools are installed properly you should see the following output at the command line after the installation is complete Pr
281. l the data stored on the SD card Let s start by preparing your SD card Follow these steps to prepare an SD card from Windows 1 You will require a software tool to format and prepare the SD card for Windows You can download the freely available formatting tool from https www sdcard org downloads formatter_4 eula windows 2 Download and install the formatting tool on your Windows computer 3 Insert your SD card and start the formatting tool 4 In the formatting tool open the Options menu and set FORMAT SIZE ADJUSTMENT to ON 5 Select the appropriate SD card and click on Format 6 Then wait for the formatting tool to finish formatting the SD card Once this is done extract the downloaded nooBs ZIP file to the SD card Make sure that you extract the content of the ZIP folder to the root location of the SD card Follow these directions to prepare SD card from Mac OS X 1 You will require a software tool to format and prepare the SD card for Mac OS X You can download the freely available formatting tool from https www sdcard org downloads formatter 4 eula mac Download and install the formatting tool on your machine Insert your SD card and run the formatting tool In the formatting tool select Overwrite Format Select the appropriate SD card and click on Format Then wait for the formatting tool to finish formatting the SD card Once this is done extract the downloaded nooBs ZIP file to the SD card Make sure that
282. le for plotting the line chart using the humidity sensor values The values are limited between 0 and 100 on the y axis where the y axis represents the relative humidity range The plot is updated every time the program receives a new humidity value pyplot figure pyplot title Humidity ax1 pyplot axes 11 pyplot plot pData pyplot ylim 0 100 Using button interrupts to control the parameters The push button interrupts are a critical part of the user experience as the user can control the temperature unit and the plot using these interrupts The Python features implemented using the push button interrupts are as follows Changing the temperature unit by pressing a button The Arduino sketch contains the logic to handle interrupts from push buttons and use them to change the temperature unit When an interrupt occurs instead of printing the temperature in Fahrenheit it sends the temperature in Celsius to the serial port As you can see in the following screenshot the Python code just prints the obtained numeric value of the temperature observation and the associated unit of measurement with it 76 Temperature 80 71 F Humidity 14 88 Light 29 Ix Start Exit CY As you can see in the following code snippet if the Python code receives the Temperature C string it prints the temperature in Celsius and if it receives the Temperature F string it prints the temperature in Fahrenheit if reading 0
283. learned in this chapter in order to develop advanced Arduino Python projects that will enable remote access to our Arduino hardware through the Internet Chapter 9 Arduino and the Internet of Things In the previous chapter we learned how to access Arduino using Ethernet from a remote location The main objective was to get you started with developing Arduino based network applications using Python We were able to accomplish this using various tools such as the web py Python library Mosquitto MQTT broker and the Arduino Ethernet library Remote access to sensor data via a Python like extensible language can open up limitless possibilities for sensor based web applications In recent years the rapid growth of these applications has enabled the development of a domain called the Internet of Things IoT In the last chapter we worked on Arduino networking However it was limited to LAN and the premise of the exercises was limited to your home or office We didn t even involve the Internet to enable global access in our exercises Traditional loT applications require Arduino to be accessed remotely from any part of the world via the Internet In this chapter we will extend the Arduino networking concepts by interfacing Arduino with cloud based platforms We will also develop web applications to access the sensor data from these cloud platforms Later in the chapter we will go through the process of setting up your cloud based messaging plat
284. lems o This problem can be solved by using manual IP addresses for both Arduino and the Raspberry Pi In our project we use a manual IP address for the Arduino but the Raspberry Pi is connected using the Wi Fi network In most cases when you are using your home Wi Fi network Wi Fi routers are set up to provide dynamic IP addresses to the device every time they reconnect to the router o You can solve this by configuring your Wi Fi router to a fixed IP address for the Raspberry Pi As the type and model of the Wi Fi router is different for every scenario you will have to use its user manual or online help forums for setting it up e Working with buzzer related issues o Sometimes the buzzer sound can be too loud or too quiet depending upon the sensor that you are using You can use PWM to configure the intensity of the buzzer In our project we used the Arduino digital pin 9 to connect the buzzer This pin also supports PWM In your Arduino code modify the line to reflect changes for the PWM pin Replace the digitalwrite BUZZER HIGH line with analogwrite BUZZER 127 o This routine will reduce the intensity of the buzzer by half from the original level You can also change the PWM value from 0 to 255 and set the intensity of the buzzer sound from lowest to highest e Control center GUI calibration o Depending upon the size of the TFT LCD screen that you are using you will have to adjust the size of the main window of Tkinter
285. let s get ourselves more familiar with Python package management Installing Python packages With the installation of pip you have two different options to install any third party Python package listed on the PyPi repository http pypi python org The following are the various procedures that you need to know to work with the installation of Python packages In the following examples the term PackageName is a pseudo name that is used for a Python package that you want to work with For your package of choice identify the appropriate package name from the PyPi website and put its name in place of PackageName In some cases you will need root super user privileges to install or uninstall a package You can use sudo followed by an appropriate command for these cases To install a Python package execute the following command at the terminal easy_install PackageName Otherwise you can also execute the following command pip install PackageName If you want to install a specific version of a package you can use the following command easy_install PackageName version If you are not aware of the exact version number you can also use comparison operators such as gt lt gt or lt to specify a range for the version number Both easy_install and pip will select the best matching version of the package from the repository and install it easy_install PackageName gt version Meanwhile for pip you can use the f
286. lib 1 Install Xcode from Apple s App Store Open Xcode and navigate to the Download tab in Preferences Download and install Command Line Tools from Preferences This step should solve any compilation related errors 2 Install homebrew using the following command in the terminal ruby e curl fsSL https raw github com Homebrew homebrew go install Install the following packages using homebrew brew install freetype brew install pkg config If you still receive an error with the freetype package try to create a link for freetype using the following command brew link freetype ln s usr local opt freetype include freetype2 usr local include freetype If you receive any further errors after performing the preceding steps go to the matplotlib forums at http matplotlib 1069221 n5 nabble com for those specific errors Note If you use matplotlib in Mac OS X you need to set up the appropriate drawing backend as shown in the following code snippet import matplotlib matplotlib use TkAgg You can learn more about drawing backends for matplotlib at http matplotlib org fag usage_ faq html what is a backend Setting up matplotlib on Ubuntu The installation of matplotlib and the required dependencies is a very straightforward process on Ubuntu We can perform this operation without using Setuptools and with the help of the Ubuntu package manager The following simple command should do the
287. lications we ve built so far To transfer messages between the Mosquitto broker and the Python interpreter we use a Python library called paho mqtt This library used to be called mosquitto python before it was donated to the Paho project Identical to the Arduino MQTT client library the paho mqtt library provides similar methods to develop the MQTT pub sub client using Python Installing paho mgtt Like all other Python libraries we used paho mqtt can also be installed using Setuptools To install the library run this command in the terminal sudo pip install paho mqtt For the Windows operating system use easy_install exe to install the library Once it is installed you can check the successful installation of the library using the following command in the Python interactive terminal gt gt gt import paho mqtt client Using the paho mqtt Python library The paho mgtt Python library provides very simple methods to connect to your Mosquitto broker Let s open the mgt tPython py file from this chapter s code folder As you can see we have initialized the code by importing the paho mqtt client library method import paho mqtt client as mq Just like the Arduino MQTT library the paho mqtt library also provides methods to connect to the Mosquitto broker As you can see we have named our client mosquittoPython by simply using the Client method The library also provides methods for activities for example when the client rec
288. lines to create your first Python Arduino project which controls different LEDs according to the detected motion Chapter 4 Diving into Python Arduino Prototyping takes you beyond the basic prototyping that we performed in the previous project and provides an in depth description of prototyping methods with appropriate examples Chapter 5 Working with the Python GUI begins our two chapter journey into developing graphical interfaces using Python The chapter introduces the Tkinter library which provides the graphical frontend for the Arduino hardware Chapter 6 Storing and Plotting Arduino Data covers Python libraries CSV and matplotlib that are used to store and plot the sensor data respectively Chapter 7 The Midterm Project a Portable DIY Thermostat contains a practical and deployable project that utilizes the material that we covered in previous chapters such as serial interfacing a graphical frontend and a plot of the sensor data Chapter 8 Introduction to Arduino Networking introduces computer networking for Arduino while utilizing various protocols to establish Ethernet communication between the Python program and Arduino This chapter also explores a messaging protocol called MQTT with basic examples This protocol is specifically designed for resource constrained hardware devices such as Arduino Chapter 9 Arduino and the Internet of Things discusses the domain of the IoT while providing step by step guidelines
289. link the red LED and display a string Motion detected on the serial monitor Once you stay steady and avoid any motion for a while you will be able to see the green LED blinking until the next movement gets detected via the PIR sensor Troubleshooting Troubleshooting is an important process if anything goes awry These are a few example problems and the troubleshooting steps for them e Serial output is correct but there are no blinking LEDs o Check the LED connections on the breadboard e The LED blinks but there is no serial output o Check the port on which the serial monitor is configured o Check whether the baud rate in the serial monitor is correct 9600 bps e There is no serial output and no blinking LEDs o Check the PIR sensor connection and make sure that you are getting signal from the PIR sensor o Check your Arduino code o Check power and ground connections Method 2 using Python and Firmata In the previous chapter we discussed the benefits of using Python programming that is assisted by Firmata over using native Arduino sketches The Python based programming approach provides tangible experience when performing any algorithmic or parametric changes In this section we are going to explore these benefits and also learn important Python programming paradigms The project setup Let s make sure that you have done the following before we go ahead with Python programming Made sure that the hardware components
290. ll create another thread for this class Basically this class creates the GUI window while populating labels and other GUI components The labels need to be updated when new sensor observations arrive are declared as class variables and are accessible from the class instant As you can see in the following code snippet we have declared the labels for temperature humidity light and motion as class variables class controlCenterWindow threading Thread def _ init__ self Tkinter canvas threading Thread __init__ self self start def callback self self top quit def run self self top Tkinter Tk self top protocol WM_DELETE_WINDOW self callback self top title Control Center self statusValue Tkinter StringVar self statusValue set Normal self tempValue Tkinter StringVar self tempValue set self humdValue Tkinter StringVar self humdValue set self lightValue Tkinter StringVar self lightValue set self motionValue Tkinter StringVar self motionValue set No Begin code subsection Declares Tkinter components Included in the code sample of the chapter End code subsection self top mainloop The previous code snippet doesn t contain the portion where we declared the Tkinter components as it is similar to what we coded in the midterm project If you have questions regarding Tkinter related issues please refer to Chapter 6 Storing and Plotting Arduino Data and Chap
291. llowing screenshot Launch Instance connect Actions v Filter All instances y All instance types y Q w Name Y InstanceID Instance Type This action will open a pop up window with a short tutorial that explains the connection process This tutorial is also linked to the step by step authentication guide for PuTTY Creating an IoT platform on the EC2 instance As you have successfully set up an Amazon EC2 instance you have a virtual computer that is running in the cloud and has a static IP address to enable remote access However this instance cannot be categorized as an IoT platform as it only contains a plain operating system Ubuntu Linux in our case and lacks the necessary software packages and configurations There are two distinct ways of setting up a custom IoT cloud platform on your virtual instance e Setting up an open source loT platform such as ThingSpeak e Separately installing and configuring the required software tools Keep the following points in mind when setting up an open source IoT platform e ThingSpeak is one of the open source IoT platforms that provides supporting files to create and host your own replica of the ThingSpeak platform e Setting up this platform on your AWS instance is quite simple and you can obtain the necessary files and guidelines to install it via https github com iobridge ThingSpeak e Although this personalized version of the ThingSpeak platform will provide suffic
292. ls but it cannot be used to write complex applications using the Firmata protocol In real world applications we really need to execute the Firmata methods using custom code which in addition to switching the LED status also includes the implementation of smart logic and algorithms interfacing other components and so on We are going to use Python for these applications starting from the next section Getting started with pySerial You learned about the Firmata protocol in the previous section This is an easy and quick way to start working with Arduino Although the Firmata protocol helps you to develop complex applications from your computer without modifying the Arduino sketch we are not ready to start coding these applications The first step towards writing these complex applications is to provide an interface between your programming environment and the Arduino via a serial port In this book you will be required to establish a connection between the Python interpreter and Arduino for every project that we develop Writing your own library which includes implementation of functions and specifications to enable communication on a serial protocol is an inconvenient and time consuming process We are going to avoid that by using an open source well maintained Python library called pySerial The pySerial library enables communication with Arduino by encapsulating the access for the serial port This module provides access to the seria
293. ly Python and Amazon cloud service The cloud services module of the overall system enables remote access to your monitoring station through the Internet The unit interacts with the user via a web application as an extended version of the control center With the use of this web application the user can observe the sensor information from the monitoring station and the system s status calculated by the control center while having remote control to turn off the buzzer So what does the architecture of the cloud services look like Architecture of the cloud services The architecture of the cloud services module with its associated components is displayed in the following diagram In the cloud services architecture we are using Xively as the intermediate data relay between the web application and the control center The control center pushes the observations obtained from the monitoring station to the Xively channels Xively stores and relays the data to the web application that is hosted on the Amazon AWS The server instance on the Amazon AWS is used to make the web application accessible through the Internet The server instance runs the Ubuntu operating system and the web application that is developed using the web py library in Python Temperature Channel Humidity Channel Ambient light Channel From Xively Control a am Eii Motion Channel Python xively web py vi Center LEd Channel Buzzer Channel System status Channel
294. mance of the code is more important than a longer development time and higher cost you should consider these static languages Some other drawbacks of Python include being memory heavy not having the proper support for threading and lacking data protection features In short we can say that even though Python provides quicker and easier ways for quick prototyping we should consider other static high level languages for development after we are done testing our prototype and we are ready to ship our product Nowadays this scenario is changing rapidly and companies have started utilizing Python for their industrial products Note You can obtain more Python related information from the official website at http www python org Installing Python and Setuptools Python comes in two versions Python v2 x and Python v3 x Here x represents an appropriate version number While Python v2 x is a legacy branch and has better library support Python v3 x is the future of Python Most Linux distributions and Mac OS X operating systems are equipped with Python and they have v2 x as their preferred and default version of Python We will be using Python v2 7 as the default version of Python for the rest of the book due to the following reasons e It is the most current version of the Python v2 x branch e It has large community support and solutions for its known issues are available through support forums e It is supported by most of the major Pytho
295. mand and accessible via a web browser Free access for Packt account holders If you have an account with Packt at www PacktPub com you can use this to access PacktLib today and view 9 entirely free books Simply use your login credentials for immediate access Preface In the era of the Internet of Things IoT it has become very important to rapidly develop and test prototypes of your hardware products while also augmenting them using software features The Arduino movement has been the front runner in this hardware revolution and through its simple board designs it has made it convenient for anyone to develop DIY hardware projects The great amount of support that is available through the open source community has made the difficulties that are associated with the development of a hardware prototype a thing of the past On the software front Python has been the crown jewel of the open source software community for a significant amount of time Python is supported by a huge amount of libraries to develop various features such as graphical user interfaces plots messaging and cloud applications This book tries to bring you the best of both hardware and software worlds to help you develop exciting projects using Arduino and Python The main goal of the book is to assist the reader to solve the difficult problem of interfacing Arduino hardware with Python libraries Meanwhile as a secondary goal the book also provides you with exercises and
296. me methods that we used in the previous exercises The code has two distinct components Python Arduino interfacing and storing data to a CSV file By skipping the explanation of pyFirmata methods to interface the Arduino board let s focus on the code that is associated with storing the sensor data The first line that we will write to the CSV file using writerow is the header line that explains the content of the columns w writerow Number Potentiometer Motion sensor Later we will obtain the readings from the sensors and write them to the CSV file as shown in the following code snippet We will repeat this process 25 times as defined by the variable i You can change the value of i according to your requirements while i lt 25 sleep 1 if pirData is not None i 1 row i potData pirData w writerow row The next question is how can you utilize this coding exercise in your custom projects The program has three main sections that can be customized to accomplish your project requirements which are as follows e Arduino pins You can change the Arduino pin numbers and the number of pins to be utilized You can do this by adding additional sensor values to the row object e The CSV file The name of the file and its location can be changed from SensorDataStore csv to the one that is specific to your application e The number of data points We have collected 25 different pairs of data points while running the whil
297. ment sensors to calculate the power load at each port Combining it with the time the device was on you can calculate very comprehensive power usage to further improve power management You can use the system clock with the motion sensor to intelligently turn off the appliance during nights and periods of no activity The Tweet a PowerStrip project can be interfaced with the remote home monitoring system that we developed in the previous project in order to obtain useful information from other sensors being used in the same house One of the modifications you can easily implement is to utilize Twitter s private messages instead of its tweets to control the appliances This will extend the access permissions of your system to other trusted Twitter accounts For security reasons you should tighten the access level and only let approved people post such messages to your account Summary You have now successfully completed two different IoT projects using just two base technologies Arduino and Python With the current project it is obvious that it is very easy to interface any other technology tool or API with Arduino and Python The project development methodology we used in these two projects will also help you with your DIY projects and other future products Happy prototyping And happy coding Index A Amazon AWS platform o o o about Getting familiar with the Amazon AWS platform URL Getting familiar with the Amazon A
298. methods to develop dynamic websites and web applications using Python Using web py it is really easy to build complex websites by utilizing just a few additional Python concepts along with what you already know Due to this limited learning curve and easy to implement methods web py is one of the quickest ways to create web applications in any programming language Let s begin with understanding these web py concepts in detail Handling URLs You might have noticed that in our first web py program we defined a variable called urls that points to the root location of the Index class urls index In the preceding declaration the first part is a regular expression used to match the actual URL requests You can use regular expressions to handle complex queries coming to your web py server and point them to the appropriate class In web py you can associate different landing page locations with appropriate classes For example if you want to redirect the data location to the data class in addition to the Index class you can change the urls variable as follows urls index data data With this provision when a client sends a request to access the http lt ip address gt 8080 data address the request will be directed towards the data class and then the GET or POST method of that class The GET and POST methods In exercise 1 where we created an Arduino based web server running on
299. mple photocells as a cheap alternative the BH1750 sensor is known for higher resolution and accuracy in a wide range of applications The ambient light also called luminous flux or lux is measured in unit lumen The BH1750 sensor supports 12C communication with part address 0x23 with x5C as the secondary address if you are using multiple BH1750 sensors The following is an image of a typical breakout board consisting of BH1750 e 8 3 al 2 g A D 8 Connect the SDA and SCL pins of the BH1750 breakout board to analog pins 4 and 5 of the Arduino Uno board as displayed in the following circuit diagram Also complete the 5V and ground connections as displayed in the following diagram u gt n 3 gt a n n 3 DIGITAL PUN E w E CO UNO TX a Ta Arduino In the previous example we used functions from the wire library to complete the I2C communication Although BH1750 is a simple and convenient I2C sensor in the case of a sensor with multiple measurement capabilities it is not convenient to code directly using the wire library In this situation you can use sensor specific Arduino libraries that are developed by the manufacturer or the open source community For BH1750 we will demonstrate the use of such a library to assist the I2C coding Before we can use this library we will have to import it to the Arduino IDE It is really important to know the process of importing libraries to your Arduino IDE as you wil
300. n Options Set up language and regional settings to match your location 5 Enable Camera Enable this Pi to work with the Raspberry Pi Camera 6 Add to Rastrack Add this Pi to the online Raspberry Pi Map Rastrack 7 Overciock Conf gure overclock for your Pi 9 About raspi config Information about this configuration too lt Select gt lt Finish gt 3 You can go back to this screen again in case you want to change any parameter by typing the following command in the terminal sudo raspi config 4 Raspberry Pi will now reboot and you will be prompted to the default login screen Log in using the default username pi and password raspberry 5 You can start the graphical desktop of the Raspberry Pi by typing the following command in the terminal startx 6 To run the Python code that we developed in the first stage you will need to set up required Python libraries on the Raspberry Pi You will have to connect your Raspberry Pi to the Internet using the Ethernet cable to install the packages Install the required Python packages on the Raspberry Pi terminal using the following command sudo apt get install python setuptools python matplotlib python numpy 7 Install pySerial using Setuptools sudo easy_install pyserial Now your Raspberry Pi is ready with an operating system and the necessary components to support Python Arduino programming Using a portable TFT LCD display with the
301. n libraries Even though the code samples exercises and projects provided in this book should work in any variant of Python 2 7 x it s better to have the latest version Installing Python Your fondness for an operating system is developed due to multiple factors and you can never ignore someone s bias towards a particular OS Thus this book provides installation and configuration guidelines for three of the most popular operating systems Linux Mac OS X and Windows Let s begin by configuring Python for a Linux computer Linux The majority of Linux distributions come with Python preinstalled To check the latest version of the installed Python use the following command at the terminal window python V Make sure that you are using an uppercase V as the option for the previous command Once you execute it on the terminal it will print the complete version number of your current Python installation If the version is 2 7 x you are good to go and your Linux is updated with the latest version of Python that is required for this book However if you have any version that is less than or equal to 2 6 x you will need to first upgrade Python to the latest version This process will require root privileges as Python will be installed as a system component that will replace the previous versions Ubuntu If you are using Ubuntu 11 10 or later versions you should already have Python v2 7 x installed on your machine You can still
302. n you press the button As you can see in the following code snippet we have first imported libraries and initialized the Arduino board using pyFirmata methods For this exercise we are only going to work with one LED and we have initialized only the ledPin variable for it import Tkinter import pyfirmata from time import sleep port dev cu usbmodemfa1331 board pyfirmata Arduino port sleep 5 ledPin board get_pin d 11 0 Note As we are using the pyFirmata library for all the exercises in this chapter make sure that you have uploaded the latest version of the standard Firmata sketch on your Arduino board In the second part of the code we have initialized the root Tkinter widget as top and provided a title string We have also fixed the size of this window using the minsize method In order to get more familiar with the root widget you can play around with the minimum and maximum size of the window top Tkinter Tk top title Blink LED using button top minsize 300 30 The Button widget is a standard Tkinter widget that is mostly used to obtain the manual external input stimulus from the user Like the Label widget the Button widget can be used to display text or images Unlike the Label widget it can be associated with actions or methods when it is pressed When the button is pressed Tkinter executes the methods or commands specified by the command option startButton Tkinter Button top tex
303. nable computer networking for Arduino Regarding the various methods of enabling networking we began the chapter by establishing a web server for Arduino We concluded that the web server on Arduino is not the best way for network communication due to the limited number of connections offered by the web server Then we demonstrated the use of Arduino as a web client to enable HTTP based GET and POST requests Although this method is useful for request based communication and requires fewer resources compared to a web server it is still not the best way for sensor communication due to the additional data overhead In the later part of the chapter we described a lightweight messaging protocol MQTT designed specifically for sensor communication We demonstrated its superiority to HT TP based protocols using a few exercises With the help of each method of Arduino Ethernet communication you learned about compatible Python libraries used to support these communication methods We used the web py library to develop a web server using Python and demonstrated the use of the library with multiple examples To support the MQTT protocol we explored an MQTT broker Mosquitto and employed the Python library paho_mqtt to serve the MQTT requests Overall we covered every major aspect of Arduino and Python communication methods throughout this chapter and demonstrated them with simple exercises In the upcoming chapters we will build upon the basics you
304. nd Arduino to control the relays The user can post tweets containing keywords from any platform such as a phone or a browser and the tweets are ultimately captured by the computation unit Required hardware components This project will require the following hardware components throughout the development and the deployment stages https www sparkfun com products 11021 Arduino Ethernet Shield https www sparkfun com products 9026 Relay four channel Arduino http www amazon com JBtek Channel Module Arduino compatible Raspberry dp BOOKTEN3TM Ihttp www powerswitchtail com PowerSwitch Tail 4 Alternative to relay Breadboard hoo For development stage USB cable for Arduino hoo For development stage Arduino power supply For deployment stage As per requirements Connection wires Relays As you can see in the following image we are introducing a new hardware component that was not utilized in any of the previous chapters a relay Images courtesy www dx com This is an electromagnetic device that uses electricity to be operated as a switch A typical relay contains three contacts on the high power side normally connected NC common C and normally open NO The other side the control side of the relay requires an activation voltage to toggle the connection from common NC to common NO This action demonstrates the switch functionalities for the connection on the high power side We ll use Ard
305. ned to utilize the Firmata protocol to implement these Python programs It also includes various Python programming paradigms such as working with indefinite loops creating custom functions working with random numbers acquiring manual inputs from prompt and so on These prototyping templates are designed in such a way that they can be easily included in large projects or they can be blueprints for a larger project that can be developed around them You learned about the pyFirmata package comprehensively in the previous section and we will only utilize those pyFirmata functions in the upcoming examples An alternative Python library that supports the Firmata protocol is covered later in the chapter Potentiometer continuous observation from an analog input A potentiometer is a variable resistor that can be controlled using a knob It has three terminals out of which two of them are Vref and ground while the third one provides a variable output The output of the potentiometer varies between the supplied voltages according to the position of the knob In Arduino you can connect the potentiometer with 5V and the ground pins of the board to provide the supply voltage When the variable terminal is interfaced with the Arduino analog input this voltage values translates between 0 and 1023 respectively In the case of pyFirmata the value of the analog observation translates between 0 and 1 This coding template containing the potentiometer can
306. ned using the following line of code uint16_t lux lightMeter readLightLevel This line provides the luminance values in the unit of lux These values are also sent to the serial port so the Python program can utilize it further Using Arduino interrupts Until now you used the Arduino program to read the physical state of an I O pin using the DigitalRead or AnalogRead functions How would you automatically obtain the state change instead of periodically reading the pins and waiting for the state to change Arduino interrupts provide a very convenient way of capturing signals for the Arduino board Interrupts are a very powerful way of automatically controlling various things in Arduino Arduino supports interrupts using the attachInterrupt method In terms of the physical pins Arduino Uno provides two interrupts interrupt 0 on digital pin 2 and interrupt 1 on digital pin 3 Various Arduino boards have different specifications for interrupt pins If you are using any board other than Uno please refer to Arduino s website to find out about the interrupt pin for your board The attachInterrupt function takes three input arguments pin ISR and mode In these input arguments pin refers to the number of the interrupt pin ISR which stands for Interrupt Service Routine refers to the function that gets called when the interrupt occurs and mode defines the condition when the interrupt should be triggered We have utilized t
307. ng screenshot This action will upload the compiled code to your Arduino board StandardFirmata Arduino 1 0 5 Upload Using Programmer StandardFirmata Firmata is a generic protocol for communicating with microcontrollers from software on a host computer It is intended to work with any To download a host software package please clink on the following lin to open the download page in your default browser http firmata ora wiki Download On completion you should see the Done uploading text in the IDE as displayed in the following screenshot for byte i i lt queryIndex 1 i 4 readAndReportData query i addr query i reg query i bytes Binary sketch size 11 948 bytes of a 32 256 byte maximum Arduino Uno on dev tty usbmodemfd1211 Your Arduino board is now ready with the latest Firmata firmware and is waiting for a request from your computer Let s move on to the next section and start testing the Firmata protocol Testing the Firmata protocol In the previous chapter we used an on board LED at pin 13 to test the Blink program This time we are going to use an external LED to get you started with the assembly of hardware components using your Arduino board As all the upcoming exercises and projects will require you to interface hardware components such as sensors and actuators to your Arduino board using a breadboard we want you to start getting hands on experience with wiring these com
308. nge of communication was limited due to the hardwired serial connection As a solution you can use a wireless protocol such as ZigBee Bluetooth or other RF channels to establish a communication channel for a remote serial interface These wireless protocols are extensively used in remote hardware applications and they use the serial interface to transfer data Due to their use of serial communication these protocols require very little to no additional programming changes on the Arduino or Python side You may require additional hardware to enable these protocols however The major benefit of these protocols is that they are really easy to implement However they are restricted with only a small geographical coverage area and limited data bandwidth Besides serial communication methods the other way to remotely access your Arduino device is to use a computer network Today computer networks are the most prolific way of communicating between computing units In the next two chapters we will explore various networking techniques using Arduino and Python which range from establishing very basic Ethernet connectivity to developing complex cloud based web applications In this chapter we will cover the following topics e The fundamentals of networking and hardware extensions that enable networking for Arduino e Python frameworks used to develop Hypertext Transfer Protocol HTTP web servers on your computer e Interfacing Arduino based HTTP
309. nitoring station can make it portable and easily deployable in any environment When designing this enclosure you should also consider the proper placement of the motion sensor and the ambient light sensor along with a button to make them accessible to the user e The Raspberry Pi and TFT LCD screen which make up the control center hardware can also be enclosed in a mountable package e Adding touch screen capabilities to the TFT LCD screen can enable additional control over the system expanding the UX use cases Summary In this chapter we developed a working prototype of a remote home monitoring system and also learned the process of hardware product development simultaneously In the project we utilized most of the hardware components and software tools that we used throughout the book We began by designing the system architecture so that we could coordinate the utilization of these tools Later we ventured into the actual development stages which included designing the hardware units and developing programs to run these units In the end we provided a list of improvements to make this prototype into a real commercial product You are welcome to use this methodology to develop your future projects and products as you now have experience working with this one In the last chapter we are going to utilize the same project development methodology to create an interesting project that utilizes your messages from a social network website to
310. nk Exercise 1 a web server your first Arduino network program system architecture remote home monitoring system o designing Designing system architecture o monitoring station The monitoring station o control center The control center o cloud services The cloud services system architecture Tweet a PowerStrip o about System architecture T e Templetor o o about Templates URL Templates e thermostat o O O O O 0 O 0 O O 0 O building Thermostat the project description project description Thermostat the project description project background Project background project stages Project goals and stages project goals Project goals and stages required components identifying The list of required components hardware design Hardware design software flow for user experience design Software flow for user experience design prototyping Stage 1 prototyping the thermostat GUI designing Designing the GUI and plot in Python plot designing Designing the GUI and plot in Python deploying Raspberry Pi used Stage 2 using a Raspberry Pi for the deployable thermostat e thermostat prototyping o Arduino interrupts using Using Arduino interrupts e thermostat using Raspberry Pi o o o deploying Stage 2 using a Raspberry Pi for the deployable thermostat portable TFT LCD display using Using a portable TFT LCD display with the Raspberry Pi
311. no Although easy_install has been used as a simple way of installing Python packages it misses out on a few useful features such as tracking actions support for uninstallation and support for other version control systems In recent years the Python community has started adopting another tool called pip over easy_install that supports these features As both easy_install and pip utilize the same PyPI repository going forward you can use any of these utilities to install the required Python packages Just to narrow down the scope we will be focusing on methods to install Setuptools and the default utilities that get installed with it that is easy_install Later in this section we will also install pip just in case you want to use it too Let s first begin by installing Setuptools for the various operating systems Linux In Ubuntu Setuptools is available in the default repository and it can be installed using the following command sudo apt get install python setuptools For Fedora it can be installed using the default software manager yum sudo yum install python setuptools For other Linux distributions it can be downloaded and built using the following single line script wget https bitbucket org pypa setuptools raw bootstrap ez_setup py 0 sudo python Once it is installed on your Linux distribution easy_install can be directly accessed from the terminal as a built in command Windows Installation of Setup
312. nology enthusiast who has been programming since the age of 10 He enjoys learning and becoming proficient with new technologies He has designed and built software ranging from simple shell scripts to scalable backend server software to interactive web and desktop user interfaces Josh has been writing software professionally using Python since 2007 and he has been building personal Arduino based projects since 2010 www PacktPub com Support files eBooks discount offers and more For support files and downloads related to your book please visit www PacktPub com Did you know that Packt offers eBook versions of every book published with PDF and ePub files available You can upgrade to the eBook version at www PacktPub com and as a print book customer you are entitled to a discount on the eBook copy Get in touch with us at lt service packtpub com gt for more details At www PacktPub com you can also read a collection of free technical articles sign up for a range of free newsletters and receive exclusive discounts and offers on Packt books and eBooks p PACKT iR https www2 packtpub com books subscription packtlib Do you need instant solutions to your IT questions PacktLib is Packt s online digital book library Here you can search access and read Packt s entire library of books Why subscribe e Fully searchable across every book published by Packt e Copy and paste print and bookmark content e On de
313. nstance using open source tools such as ThingSpeak Your control center will then communicate directly to your server and eliminate dependency on third party IoT services e If Xively is your platform you can also use additional features such as graphs on your smart phone which are provided by Xively Once your phone is paired with Xively you can access this feature directly e Alternatively you can use other cloud services such as Microsoft Azure and Google App engine instead of Amazon AWS You can also set up your own cloud server depending upon your familiarity with cloud computing Although having your own cloud will give you complete control of the server third party services such as Amazon can be more cost effective and require less maintenance compared to self hosted servers e If you are planning to develop a large scale system that is based on the current architecture you can increase the computing capability of your existing cloud instance You can also implement a distributed server system to accommodate the large number of remote monitoring systems that can be accessed by an even greater number of users Improving intelligence for situation awareness In this project we have used four different sensors to monitor the physical environment each sensor obtains user inputs with two types of actuators for notification Although we are using a good amount of information sources our situation awareness algorithm is limited to iden
314. nt_value statusTemp try datastream update except HTTPError as e print HTTPError 0 1 format e errno e strerror 6 Inthe code you will also have to modify the Xively feed ID and the API key and replace them with the values that your obtained from your virtual device Once you have performed this modification run the following command If everything goes as planned you will be able to open the web application in your web browser python RemoteMonitoringApplication py If you are running the Python code on your computer you can open http 127 0 0 1 8080 to access the application If you are running the application on the cloud server you need to enter the IP address or domain name of your server to access the web application http lt AWS IP address gt 8080 If the web application is running from the cloud it can be accessed from anywhere using the Internet which was one of the original project requirements With this last step you have successfully completed the development of the remote home monitoring system that is based on Arduino and Python Testing the web application When you open the web application in a browser you will be able to see a similar output as shown in the following screenshot As you can see the web application displays the temperature humidity light and motion values The Refresh button fetches the sensor data from Xively again and loads the application once more The Buzzer Off button sets t
315. ntelligence for situation awareness Improving intelligence for situation awareness hardware enclosures creating Creating an enclosure for hardware components e Representation State Transfer REST o about Python web framework web py e RESTful web applications o O O 0 O o o O O o 0 developing with Arduino and Python RESTful web applications with Arduino and Python designing Designing REST based Arduino applications GET request implementing Working with the GET request from Arduino GET request generating The Arduino code to generate the GET request GET request handling with web py The HTTP server using web py to handle the GET request POST request implementing Working with the POST request from Arduino POST request generating The Arduino code to generate the POST request POST request handling with web py The HTTP server using web py to handle the POST request architecture Exercise 3 a RESTful Arduino web application Arduino sketch The Arduino sketch for the exercise web py web application The web py application to support REST requests resource constrained messaging protocol using Why do we need a resource constrained messaging protocol Scale widget o about Learning Tkinter for GUI design The Scale widget adjusting the brightness of an LED o used for adjusting brightness of LED The Scale widget adjusting the brightness of an LED SD card
316. o Arduino WiFi Shield Arduino Y n Arduino Ethernet library The Ethernet class The IPAddress class The Server class The Client class The GET and POST methods The monitoring station The cloud services services Defining UX flow The list of re quired components 11 Tweet a PowerStrip Index Python Programming for Arduino Python Programming for Arduino Copyright O 2015 Packt Publishing All rights reserved No part of this book may be reproduced stored in a retrieval system or transmitted in any form or by any means without the prior written permission of the publisher except in the case of brief quotations embedded in critical articles or reviews Every effort has been made in the preparation of this book to ensure the accuracy of the information presented However the information contained in this book is sold without warranty either express or implied Neither the author nor Packt Publishing and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals However Packt Publishing cannot guarantee the accuracy of this information First published February 2015 Production reference 1230215 Published by Packt Publishing Ltd
317. o we installed Setuptools to download and install additional Python packages Make sure that you have Setuptools installed and configured properly Before we advance further we will have to install dependencies for matplotlib Open the command prompt and use the following command to install the dateutil and pyparsing packages gt easy_install exe python_dateutil gt easy_install exe pyparsing Once you have successfully installed these packages download and install the precompiled NumPy package from http sourceforge net projects numpy Make sure that you choose the appropriate installation files for Python 2 7 and the type of your Windows operating system Now your computer should have satisfied all the prerequisites for matplotlib Download and install the precompiled matplotlib package from http matplotlib org downloads html In this installation process we have avoided the usage of Setuptools for NumPy and matplotlib because of some known issues related to matplotlib in the Windows operating system If you can figure out ways to install these packages using Setuptools then you can skip the preceding manual steps Configuring matplotlib on Mac OS X Installation of matplotlib on Mac OS X can be difficult depending upon the version of Mac OS X and the availability of dependencies Make sure that you have Setuptools installed as described in Chapter 1 Getting Started with Python and Arduino Assuming that you already have Setup
318. o about Installing pip installation PubSubClient library Installing the PubSubClient library installation pySerial library o about Installing pySerial installation Python o about Installing Python and Setuptools on Linux Linux on Ubuntu Ubuntu on Fedora Red Hat Linux Fedora and Red Hat on Windows Windows o on Mac OS X Mac OS X installation Python packages o about Installing Python packages installation Setuptools o about Installing Setuptools o on Linux Linux o on Windows Windows o on Mac OS X MacOS X installation web py o about Installing web py int data type o about Data types integrated circuit IC o about Prototyping with the I2C protocol integrated development environment IDE o about Installing the Arduino IDE integrated development environment IDLE o about The fundamentals of Python programming Internet of Things IoT applications o about Why we use Python O O O 90 e Internet Protocol IP O e oT O O o o about Networking fundamentals getting started process Getting started with the loT hardware design Hardware design The IoT cloud platforms cloud applications developing with Python and Xively Developing cloud applications using Python and Xively custom cloud platform Your own cloud platform for the loT e IoT cloud platform on EC2 instance o o O O O 0 0 0 creating Creating an IoT platform on the EC2 instan
319. oad programs to the Arduino board On launching the Arduino IDE you will find an interface similar to the one displayed in the following screenshot The IDE contains a text editor for coding a menu bar to access the IDE components a toolbar to easily access the most common functions and a text console to check the compiler outputs A status bar at the bottom shows the selected Arduino board and the port name that it is connected to as shown here ES sketch_decl4a Arduino 1 0 5 File Edit Sketch Tools Help sketch_dec14a Arduino Uno on COMY What is an Arduino sketch An Arduino program that is developed using the IDE is called a sketch Sketches are coded in Arduino language which is based on a custom version of C C Once you are done with writing the code in the built in text editor you can save it using the ino extension When you save these sketch files the IDE automatically creates a folder to store them If you are using any other supporting files for a sketch such as header files or library files they are all stored at this location which is also called a sketchbook To open a new sketchbook open the Arduino IDE and select New from the File menu as shown in the following screenshot sketch_dec14a Arduino 1 0 5 Edit Sketch Tools Help New Ctrl N Open Ctrl 0 Sketchbook Examples Close Ctrl WW Save Ctrl S Save As Ctrl Shift S Upload Ctrl U Upload Using Programmer Ctrl Shift U Page S
320. oard digital pin mode OUTPUT board digital pin write 1 If you have used an alternative method of assigning the pin s mode you can use the write method as follows ledPin board get_pin d 13 0 ledPin write 1 In the case of the PWM signal the Arduino accepts a value between 0 and 255 that represents the length of the duty cycle between 0 and 100 percent The pyFirmata library provides a simplified method to deal with the PWM values as instead of values between 0 and 255 you can just provide a float value between 0 and 1 0 For example if you want a 50 percent duty cycle 2 5V analog value you can specify 0 5 with the write method The pyFirmata library will take care of the translation and send the appropriate value that is 127 to the Arduino board via the Firmata protocol board digital pin mode PWM board digital pin write 0 5 Similarly for the indirect method of assignment you can use some code similar to the following snippet pwmPin board get_pin d 13 p pwmPin write 0 5 If you are using the SERVO mode you need to provide the value in degrees between 0 and 180 Unfortunately the SERVO mode is only applicable for direct assignment of the pins and will be available in future for indirect assignments board digital pin mode SERVO board digital pin write 90 The read method The read method provides an output value at the specified Arduino pin When the Iterator class is being used
321. ocessing dependencies for pyserial Finished processing dependencies for pyserial This means that you have successfully installed the pySerial library and you are good to go to the next section 3 Now to check whether or not pySerial is successfully installed start your Python interpreter and import the pySerial library using the following command gt gt gt import serial Playing with a pySerial example Your Arduino board has the Firmata sketch StandardFirmata from the previous example To play with pySerial we are not going to use the Firmata protocol anymore Instead we are going to use another simple Arduino sketch that implements serial communication that can be captured on the Python interpreter Sticking with the promise of not performing any coding for the Arduino sketch let s select an example sketch from the Arduino IDE 1 As displayed in the following screenshot navigate to File Examples 01 Basics DigitalReadSerial GO Edit Sketch Tools Help New SEN Open Sketchbook AnalogReadSerial Close 02 Digital se BareMinimum Save ste 03 Analog gt Blink Save As 085 04 Communication gt Upload KU 05 Control Fade Upload Using Programmer DEU 06 Sensors gt ReadAnalogVoltage 07 Display 3 Page Setup EP 08 Strings gt Print 3P 09 USB gt 10 StarterKit gt ArduinolSP EEPROM gt Esplora r Ethernet gt Firmata de GSM 2 Compile and upload the program to the Arduino board using the s
322. ode of pin mode assignment that we learned in the previous section Set mode of pin 3 as PWM pwmPin board get_pin d 3 p As part of collecting manual inputs from the user we are running a combination of the try except statement to release the board on exit and the while statement to obtain continuous inputs from the user The code template introduces the input method to obtain custom values motor speed and duration to run the motor from Python s interactive terminal Once these values are obtained from the user the program calls the dcMotorControl function to perform the motor action try while True r input Enter value to set motor speed if r gt 100 or r lt 0 print Enter appropriate value board exit break t input How long seconds dcMotorControl r t except KeyboardInterrupt board exit os _exit LED controlling LED brightness using PWM In the previous template we controlled the speed of DC motor using PWM One can also control the brightness of the LED using the same method Instead of asking the user to input brightness we are going to use the Python module random in this template We will use this module to generate a random number between 1 and 100 which will be later used to write that value on the pin and randomly change the brightness of the LED This randint function is a really useful feature provided by the random module and it is widely used in testing prototypes by
323. of calling the direct method every time you need to use that pin In pyFirmata this assignment can be performed using the get_pin pin_def method from pyfirmata import Arduino port dev cu usbmodemfa1311 board Arduino port pin mode assignment ledPin board get_pin d 13 0 The get_pin method lets you assign pin modes using the pin_def string parameter d 13 0 The three components of pin_def are pin type pin number and pin mode separated by a colon operator The pin types analog and digital are denoted with a and d respectively The get_pin method supports three modes i for input o for output and p for PWM In the previous code sample d 13 0 specifies the digital pin 13 as an output In another example if you want to set up the analog pin 1 as an input the parameter string will be a 1 i Working with pins Now you have configured your Arduino pins it s time to start performing actions using them Two different types of methods are supported while working with pins reporting methods and I O operation methods Reporting data When pins get configured in a program as analog input pins they start sending input values to the serial port If the program does not utilize this incoming data the data starts getting buffered at the serial port and quickly overflows The pyFirmata library provides the reporting and iterator methods to deal with this phenomenon The enable_reporting method is used to set
324. og results by utilizing square waves and controlling the width of the signal As we already know the digital pins of the Arduino board can only have two states 5V HIGH and 0V LOW One can generate square pulses by controlling the switching pattern between HIGH and LOW and thus generate the pulse By changing the width of these pulses you can simulate any voltage between OV and 5V As you can see in the following diagram we have a square wave with 25 percent width of the duty cycle It means that we are simulating 0 25 5V 1 25V for the period of that duty cycle Duty Cycle 5v Ov lt gt 25 Duty Cycle The Arduino language supports PWM using the analogwrite function where the voltage range between OV and 5V is linearly scaled for values between 0 and 255 For example 50 percent duty cycle simulation of 2 5V translates to a value of 127 which can be coded in Arduino as analogwrite 13 127 Here the number 13 represents the digital pin that supports PWM on the Arduino Uno board Similarly a 20 percent duty cycle 1V translates to analogwrite 13 64 Assigning pin modes The direct method of configuring pins is mostly used for a single line of execution calls In a project containing a large code and complex logic it is convenient to assign a pin with its role to a variable object With an assignment like this you can later utilize the assigned variable throughout the program for various actions instead
325. ollowing identical commands to perform similar operations pip install PackageName version pip install PackageName gt version As an example if you want to install a version between 1 0 and 3 0 you will need to use the following command pip install PackageName gt 0 1 lt 0 3 It is really easy to upgrade a package using either easy_install or pip The command options used by both are also very similar easy_install upgrade PackageName pip install upgrade PackageName Although easy_install doesn t support clean uninstallation of a package you can use the following command to make sure that Python stops searching for the specified package Later carefully remove the package files from the installation directory easy_install mxN PackageName A much better way to perform a clean uninstallation of the majority of packages is to use pip instead Of easy_install pip uninstall PackageName A detailed list of the Python packages supported by Setuptools can be found at the PyPI website at https pypi python org The fundamentals of Python programming If you have previous experience of working with any other programming language Python is very easy to get started with If you have never done programming before this section will walk you through some of the basics of Python If you have already worked with Python you should skip this section and move on to the next one Assuming that the setup instruct
326. om angle to set Servo motor angle def setServoAngle pin angle board digital pin write angle sleep 0 015 In the main logic of this template we want to incrementally move the motor shaft in one direction until it achieves the maximum achievable angle 180 degrees and then move it back to the original position with the same incremental speed In the while loop we will ask the user to provide input to continue this routine which will be captured using the raw_input function The user can enter the character y to continue this routine or enter any other character to abort the loop Testing the function by rotating motor in both direction while True for i in range 180 setServoAngle pin i for i in range 180 1 1 setServoAngle pin i Continue or break the testing process i raw_input Enter y to continue or Enter to quit if i y pass else board exit break While working with all these prototyping examples we used the direct communication method by using digital and analog pins to connect the sensors with Arduino Now let s get familiar with another widely used communication method between Arduino and the sensors which is called I2C communication Prototyping with the I2C protocol In the previous section sensors or actuators were directly communicating with Arduino via digital analog or PWM pins These methods are utilized by a large number of basic low level sensors and you will be wi
327. oming section You can select any one of these Arduino boards according to your project requirements and the Arduino IDE should be able to compile and download the program to the board The Arduino Uno board As Uno is going to be the de facto board for the majority of the projects in this book let s get ourselves familiar with the board The latest revision of the Uno board is based on Atmel s ATmega328 microcontroller The board extends the I O pins of the microcontroller to the peripheral which can then be utilized to interface components using wires The board has a total of 20 pins to interface out of which 14 are digital O pins and 6 are analog input pins From the 14 digital 1 O pins 6 pins also support pulse width modulation PWM which supports the controlled delivery of power to connected components The board operates on 5V The maximum current rating of the digital I O pins is 40 mA which is sufficient to drive most of the DIY electronic components excluding motors with high current requirements While the previous image provided an overview of the Uno board the following diagram describes the pins on the Uno board As you can see the digital pins are located on one side of the board while the analog pins are on the opposite side The board also has a couple of power pins that can be used to provide 5V and 3 3V of power to external components The board contains ground pins on both sides of the board as well We will b
328. on of the chapter covers the project design process including goals requirements architecture and UX Once we are done with the design process we will jump into the actual development of the project which is divided into three separate stages Next we will cover common troubleshooting topics that are usually faced while working with large projects In our efforts to develop utilizable DIY projects the later section covers tips and features to extend the project As this is quite a large project compared to other projects in the book we are not going to jump straight into the actual development process without having any strategy Let s start by getting ourselves familiar with the standard design methodology for hardware projects The design methodology for IoT projects The process of developing a complex product that tightly couples hardware devices with high level software services requires an additional level of planning For this project we will exercise a proper product development approach to help you get familiar with the process of creating real world hardware projects This method can then be used to plan your own projects and take them to the next level The following diagram describes a typical prototype development process which always begins by defining the major goals that you want to achieve with your product Define major project goals Derive project requirements from goals Design System Architectur
329. on with Xively includes interfacing the Arduino board with the Xively platform via standalone Arduino code We have already built the necessary hardware using the Arduino Uno Ethernet Shield and a few sensors Let s connect it to your computer using the USB port You also need to connect the Ethernet Shield to your home router using the Ethernet cable Uploading Arduino data to Xively The Arduino IDE has a built in example that can be used to communicate with the Xively service This is known as PachubeClient Pachube was Xively s previous name Note It is important to note that the reason behind using this default example is to give you a jump start in the interfacing exercises This particular sketch is rather old and may get dropped as a default exercise in the upcoming releases of the Arduino IDE In that case you can directly jump to the next exercise or develop your custom sketch to perform the Same exercise Perform the following steps to upload Arduino data to Xively 1 Open the Arduino IDE and then open the PachubeClient example by navigating to File Examples Ethernet PachubeClient 2 To establish communication with Xively you will need the feed ID and the API key of your Xively device which you obtained in the last section 3 In the opened Arduino sketch perform the following changes using the obtained feed ID and API key You can specify any project name for the USERAGENT parameter define APIKEY lt Your AP
330. one time value for the PWM signal it will be useful to have a widget that can dynamically provide this value As brightness can be fluctuated between 0 and 100 percent it makes sense to use a slider that varies between 0 and 100 The Tkinter library provides this kind of sliding interface using the Scale widget As we are working to change the brightness of the LED and supply analog input we will be using a digital pin with the PWM support In the previous exercise we used digital pin 11 which already supports PWM If you are using a custom version of the circuit different to the one provided earlier we recommend that you change it to a pin that supports PWM Now it is time to open the program file exampleScale py for this exercise The first stage of the program that involves importing the necessary libraries and initializing the Arduino board using pyFirmata is almost the same as in the previous exercise Change the string that is used to specify the appropriate value for the port variable according to the operating system and the port that you are using We will also instantiate the root window with the unique title for this exercise as we did in the previous exercises This part of the program will often reoccur for a large number of exercises and you can refer to the previous exercise for more information In the next stage we will continue building the code that we developed earlier to provide a manual time delay for the LED We wil
331. onents This process will help you to minimize any hardware rework and subsequent software modifications Now that you have learned about the methodology let s begin with the actual development process for our remote home monitoring system Project overview The smart home is one of the most well defined and popular subdomains of the IoT The most important feature of any smart home is its capability to monitor the physical environment Fortunately the exercises and projects that we covered in the previous chapters include components and features that can be used for the same purpose In this chapter we are going to define a project that will utilize these existing components and programming exercises In the midterm project of Chapter 7 The Midterm Project a Portable DIY Thermostat we created a deployable thermostat with the ability to measure temperature humidity and ambient light If we want to utilize this midterm project the nearest IoT project that we can build on top of it is the remote home monitoring system The project will have Arduino as the main point of interaction between the physical environment and the software based services We will have a Python program as the middle layer which will bridge the sensor information coming from Arduino with the user facing graphical interface Let s start by defining the goals that we want to achieve and the project requirements to satisfy these goals The project goals The Nest t
332. onfigure the Arduino board for these operating systems In the previous chapter we utilized example code to get started with the Arduino IDE If you were unable to successfully communicate with Arduino by following the information given in the previous chapter follow the instructions provided in this section to establish a connection between your computer and your Arduino First connect your Arduino board to your computer s USB port using a USB cable and follow the steps according to your operating system Linux If you are using the latest version of Ubuntu Linux once you connect the Arduino board and open the Arduino IDE you will be asked to add your username to the dailout group as displayed in the following screenshot Click on the Add button and log out from the system You don t need to restart the computer for the changes to take effect Log in with the same username and open the Arduino IDE You need to be added to the dailout group to upload code to an Arduino microcontroller over the USB or serial ports You must log out and log in again before any group changes will take effect Ignore Add If you don t see this dialog box check whether you can see the Serial Port option in the Tools menu of the Arduino IDE It is possible that the installation of other programs might have added your username to the dailout group already If you don t get the dialog box and don t have any options to select in Serial
333. ontrol unit should not comprise of a desktop computer or laptop Instead it should be made deployable using a platform such as a Raspberry Pi e The control unit should demonstrate a primitive level of situation awareness capability by utilizing the collected sensor information e The control unit should have a graphical interface to provide the sensor s observation and the current state of the system e The system must be accessible via the Internet using cloud based services e The web application that provides remote access should have the capability to display the sensor s observations through a web browser e The system should also provide basic control of the actuators to complete the remote access experience by using the web application e Asthe monitoring unit can be constrained by computation resources the system should use hardware oriented messaging protocols to transfer information Although there are many other minor requirements that can be part of our project they have been skipped in this book If you have any additional plans for your remote home monitoring system this is the time that you must define these requirements before you jump into designing the architecture Any future changes to the requirements can significantly affect the development stage and make hardware and software modification difficult In the last section of the chapter we have laid down a number of additional features that you may want to consider impl
334. operations such as updating the plot and closing the plot through their respective onStartButtonPress and onExitButtonPress functions The onStartButtonPress function also consists of the interfacing point between the matplotlib and pyFirmata libraries As you can observe from the following code snippet we will start updating the plot using the draw method and the Tkinter window using the update method for each observation from the analog pin a0 which is obtained using the read method def onStartButtonPress while True if flag get sleep 1 pData append float a0 read pyplot ylim 0 1 del pData 0 11 set_xdata i for i in xrange 25 11 set_ydata pData update the data pyplot draw update the plot top update else flag set True break The onExitButtonPress function implements the exit function as described by the name itself It closes the pyplot figure and the Tkinter window before disengaging the Arduino board from the serial port Now execute the program after making the appropriate changes to the Arduino port parameter You should be able to see a window on your screen that is similar to the one displayed in the following screenshot With this code you can now control your real time plots using the Start and Pause buttons Click on the Start button and start rotating the potentiometer knob When you click on the Pause button you can observe that the program has stopped plotting new values Whil
335. or buy another instance On the next page you will be prompted to enter your name e mail address and a password as displayed in the following screenshot Fill in the information to continue with the sign up process My name is Pratik Desai My e mail address is pratik example com Type it again pratik example com note this is the e mail address that we will use to contact you about your account Enter a new password Type it again 4 You will be asked to enter your credit card information during the sign up process However you won t be charged for using the services included in the free account Your credit card will be only used if you exceed any limitations or buy any additional services 5 The next stage includes the verification of your account using your phone number Follow the instructions that are displayed in the following screenshot to complete the identity verification process 1 Provide a telephone number Please enter your information below and click the Call Me Now button Country Code Phone Number Ext United States 1 2 Call in progress 3 Identity verification complete 6 Once you have verified your identity you will be redirected to the page that lists the available Amazon AWS plans Select the appropriate plan that you want to subscribe to and continue If you are not sure you can select the Basic Free plan option which we recommend for our
336. or the initialization of the Arduino board is unchanged port dev cu usbmodemfa1331 board pyfirmata Arduino port sleep 5 redPin board get_pin d 10 0 greenPin board get_pin d 11 0 In our utilization of the Checkbutton widget we are using a very useful Tkinter variable class that is called Intvar The Tkinter variable can tell the system when the value of the variable is changed To better understand the Tkinter variable class and its specific utilization in our exercise take a look at the following code snippet from the program redVar Tkinter IntVar redCheckBox Tkinter Checkbutton top text Red LED variable redVar redCheckBox grid column 1 row 1 The Checkbutton widget lets a user select between two different values These values are usually 1 on or off making the Checkbutton widget a switch To capture this selection the variable option is required in the widget definition A variable can be initialized using one of the Tkinter variable class Intvar As you can see the redVar variable object that is instantiated using the Intvar class is used for the variable option while defining the Checkbutton widget redCheckButton Therefore any operation on the redCheckButton object will be translated to the redvar variable object As IntVar is a Tkinter class it automatically takes care of any changes in the variable values through the Checkbutton widget Therefore it is advisable
337. ore familiar with the Mosquitto configuration user password 3 Press Ctrl X to save and exit the file from the nano editor When you are prompted to confirm the save operation select Y and press Enter 4 In the same folder open the Mosquitto configuration file using thenano editor sudo nano mosquitto conf 5 In the opened file scroll down the text content until you reach the security section In this section find the allow_anonymous true line of the code and replace it with allow_anonymous false Make sure that you have removed the symbol With this operation we have disabled the anonymous access to the Mosquitto broker and only those clients with proper credentials can access it 6 After performing the previous changes scroll further down in the file uncomment the line password_file and replace it with this password_file etc mosquitto passwd 7 Now that you have configured the basic security parameters for your broker you must restart the Mosquitto service for the changes to take effect In Ubuntu Mosquitto is installed as part of the background service and you can restart it using the following command sudo service mosquitto restart 8 To test these authentication configurations open another terminal window in your computer and execute the following command with the public IP address of your instance If you are able to successfully publish your message without any errors your Mosquitto broker now has a se
338. otlib library with the Tkinter graphical interface In the last exercise of the previous chapter we integrated Tkinter with pyFirmata to implement the project of Chapter 3 The First Project Motion triggered LEDs with the GUI In this exercise we will extend this integration further by utilizing matplotlib We will perform this action by utilizing the same Arduino circuit that we have been using in this chapter and expand the code that we used in the previous exercise Meanwhile we are not introducing any new methods in this exercise instead we will be utilizing what you learned until now Open the plotTkinter py file from this chapter s code folder As mentioned earlier the program utilizes three major Python libraries and interfaces them with each other to develop an excellent Python Arduino application The first interfacing point is between Tkinter and matplotlib As you can see in the following lines of code we have initialized three button objects startButton pauseButton and exitButton for the Start Pause and Exit buttons respectively startButton Tkinter Button top text Start command onStartButtonPress startButton grid column 1 row 2 pauseButton Tkinter Button top text Pause command onPauseButtonPress pauseButton grid column 2 row 2 exitButton Tkinter Button top text Exit command onExitButtonPress exitButton grid column 3 row 2 The Start and Exit buttons provide control points for matplotlib
339. ou can use either of these methods we recommend that you use the Xively Arduino library as it is officially maintained by Xively In this exercise we will download digital values from a channel called LED Later we will use these digital values O and 1 to switch an LED that is connected to our Arduino board As an input to this channel we will alter the current value of the channel on the Xively platform s website while letting the Arduino download that value and perform the appropriate task Let s begin by importing the Xively Arduino library and its dependencies As you already know how to import libraries in the Arduino IDE visit https github com amcewen HttpClient to download and import the HttpClient library This is a dependency that is required by the Xively Arduino library to function Once you have imported the HttpClient library download the xively Arduino library from https github com xively xively_arduino and repeat the import process The xively Arduino library ships with few examples so that you can get started We will use their example as base code for downloading data for our exercise 1 In the Arduino IDE navigate to File Examples Xively_arduino DatastreamDownload and open the DatastreamDownload example Change the default API key to your own API key that was obtained from the device that you created As displayed in the following code snippet you need to also identify your channel name which is LED in
340. ou can see in the program window you have two other columns as well as the column containing the labels The second column in the program lets you select the role for the appropriate pins You can specify the role of digital pins in the case of Arduino Uno from 2 to 13 as input or output As displayed in the following screenshot you will see Low in the third column as soon as you select the role of pins 2 and 3 as input pins This is correct as we don t have any input connected to these pins You can play with the program by changing the roles and values of multiple pins Pin 2 Input Low Pin 3 Input Low Pin 4 Output Low Pin 5 Output s Low As we have connected the LED to digital pin 13 we are not expecting any physical changes on the board while you are playing around with the other pins 6 Now select pin 13 as an output pin and press the Low button This will change the button s label to High and you will see that the LED is turned on By performing this action we have changed the logic of the digital pin 13 to 1 that is High which translates to 5 volts at the pin This potential will be sufficient to light the LED You can change the level of pin 13 back to 0 by clicking on the button again and turning it to Low This will change the potential back to 0 volts in 12 Output s Low in 13 Output A ra in 14 Analog AO 153 The program that we used here is perfect to test the fundamenta
341. oud platform that is accessible through the Internet you will at least require a computational unit with Internet connection and a static IP or DNS address Today the majority of consumer oriented Internet Service Providers ISPs do not provide static IPs with their Internet service making it difficult to host a server at home However various companies such as Amazon Google and Microsoft provide free or cost effective cloud computing services which make it easier to host your cloud on their platforms These services are highly scalable and they are equipped with a large amount of features to satisfy the majority of consumer requirements In the following section you will be creating your first cloud computing instance on Amazon Web Services AWS Later in this chapter we will install and configure the appropriate software tools such as Python Mosquitto broker and so on to utilize this Amazon instance as an IoT cloud platform Note The major reason behind developing or configuring a personal cloud platform is to have access to your IoT hardware through the Internet Due to the lack of a static IP address for your home network you may not be able to access you prototypes or projects from a remote location A cloud platform can be used as the de facto computation unit for your network based projects Getting familiar with the Amazon AWS platform AWS is a collection of various cloud services offered by Amazon which together make up a
342. outTopic From outTopic From outTopic From Arduino Arduino Arduino Arduino Arduino Arduino Arduino Arduino Arduino Arduino Arduino Arduino Arduino Arduino outTopic From Arduino Now to confirm the publishing operation of the Python MQTT client let s open the Serial Monitor window from your Arduino IDE As you can see in the Serial Monitor window text that contains the inTopic topic name and the From Python message is being printed every 5 seconds This validates the Python publisher as we are publishing the same message for the same topic every 5 seconds through the publishTest function 600 dev cu usbmodemfa1331 inTopic From Python inTopic From Python inTopic From Python inTopic From Python inTopic From Python inTopic From Python inTopic From Python inTopic From Python inTopic From Python inTopic From Python inTopic From Python inTopic From Python inTopic From Python inTopic From Python v M Autoscroll No line ending 9600 baud HJ Exercise 4 MQTT Gateway for Arduino In exercise 3 we used the REST architecture to transfer motion and humidity sensor data between our Arduino and the web browser In this exercise we will develop an MQTT Gateway using the Mosquitto broker and the MQTT clients to transfer sensor information from our Arduino to the web browser The goal of the exercise is to replicate the same components that we implemented in the REST exercise but with
343. pass the pin number and a message as parameters blinkLED greenLedPin No motion detected These parameters are then utilized in the performed action writing a message on a serial port and setting up the LED status by the blinkLED function This function also introduces a delay to perform the blink action by using the delay function Testing We verified the designed system in the Testing hardware connection section using manual inputs via the Firmata test program As we have now implemented the software design we need to verify that the project is performing objective tasks autonomously and repeatedly With the USB port connected to the computer open the serial monitoring tool from the Arduino IDE by navigating to Tools Serial Monitor or by pressing Ctrl Shift M You should start seeing a message similar to the one displayed in the following screenshot on the Serial Monitor window 600 dev tty usbmodemfd1211 No motion detected No motion detected No motion detected Motion detected Motion detected Motion detected Motion detected Motion detected Motion detected Motion detected Motion detected v M Autoscroll No line ending 9600 baud While writing the blinkLED function to perform actions we included an action to write a string via a serial port Move your hand over the PIR sensor in such a way that the PIR sensor can detect motion This event should trigger the system to b
344. pe int and holds the value 10 Later in the code all occurrences of the pin variable will retrieve data from the declaration that we just made here You can use any combination of alpha numeric characters to select the variable name as long as the first character is not a number Constants In the Arduino language constants are predefined variables that are used to simplify the program e HIGH Low While working with digital pins on the Arduino board only two distinct voltage stages are possible at these pins If a pin is being used to obtain an input any measure above 3V is considered a HIGH state If you are using a pin for output then the HIGH state will set the pin voltage to 5V The opposite voltage levels are considered as LOW states e false true These are used to represent logical true and false levels false is defined as O and true is mostly defined as 1 e INPUT OUTPUT These constants are used to define the roles of the Arduino pins If you set the mode of an Arduino pin as INPUT the Arduino program will prepare the pin to read sensors Similarly the OUTPUT setting prepares the pins to provide a sufficient amount of current to the connected sensors We will utilize these constants later in the book and we will also explain them with example code Data types The declaration of each custom variable requires the user to specify the data type that is associated with the variable The Arduino language uses a standard set of
345. pen test txt w This command will create a test txt file in the same folder in which you started the Python interpreter or the location from where the code is being executed The preceding command uses the w mode that opens a file for writing or creates a new one if it doesn t exist The other modes that can be used with the open function are displayed in the following table p This opens a file for appending It starts appending from the end of the document b This opens a file for appending and reading It starts appending from the end of the document Note s b This opens a file for reading and writing Make sure that you have the proper read and write permissions for the files if you are utilizing these modes in a Unix or Linux environment The write method Once the file is open in one of the writing or appending modes you can start writing to the file object using this method The write method only takes a string as an input argument Any other data format needs to be converted into a string before it is written gt gt gt f write Hello World n In this example we are writing the Hello world string that ends with a new line character n This new line character has been explained in the previous chapter and you can obtain more information about it at http en wikipedia org wiki Newline You can also use the writelines method if you want to write a sequence of strings to the file g
346. pen the Serial Monitor window in the Arduino IDE to observe the following output 90 dev tty usbmodemfal1331 Send conecting connecting i disconnecting connecting HTTP 1 1 200 OK Date Thu 24 Jul 2014 22 09 24 GMT Content Type text plain charset utf 8 Content Length Connection close X Request Id f50259 927d5e836079276f5f3350650125c9b61 Cache Control mox age 0 Vary Accept Encoding disconnecting a connecting X M Autoscroll No line ending 9600 baud F If you see an output in the Serial Monitor window that is similar to the one displayed in the previous screenshot your Arduino is successfully connected to Xively and is uploading data on the HumidityRaw channel Open your device in Xively s website and you will be able to see an output that is similar to the following screenshot on the web page This confirms that you have successfully uploaded data to an IoT cloud platform using your remotely located Arduino HumidityRaw 463 a few seconds ago 5 5 a Edit Delete Downloading data to Arduino from Xively In the previous coding exercise we used a default Arduino example to communicate with Xively However Xively also provides a very efficient Arduino library with built in functions for rapid programming In the next exercise we will use an alternative method to communicate with the Xively platform using the Xively Arduino library Although y
347. perating system will automatically install the necessary drivers by itself Once this process is complete select an appropriate COM port from the Serial Port option in the menu bar From the main menu navigate to Tools Serial Port and select the COM port Troubleshooting Even after following the steps mentioned earlier if you still don t see the highlighted Serial Port option as displayed in the following screenshot then you have got a problem There can be two main reasons for this the serial port is being used by another program or the Arduino USB drivers are not installed properly If any program other than the Arduino IDE is using the specific serial port terminate that program and restart the Arduino IDE Sometimes in Linux the br1tty library conflicts with the Arduino serial interface Remove this library log out and log back in sudo apt get remove brltty In Windows reinstalling the Arduino IDE also works as this process installs and configures the Arduino USB driver again h_nov12a Arduino 1 0 3 n SooS Help Auto Format Archive Sketch Fix Encoding amp Reload Serial Monitor Ctrl Shift M Board gt Programmer Burn Bootloader Tip The Arduino board can be used by only one program at a time It is very import to make sure that any previously used program or other services are not using the serial port or Arduino when you try to use the Arduino IDE This check will become very important
348. perature TMP102 provides better resolution and accuracy compared to traditional analog temperature sensors such as LM35 or TMP36 The following is an image of TMP102 The previous image shows a breakout board with the available pins for the TMP102 sensor Please keep in mind that the TMP102 sensor that you obtain might have a different pin layout compared to the one displayed in the image It is always advisable to check the datasheet of your sensor breakout board before making any connections As you can see in the image the TMP102 sensor supports the I2C protocol and is equipped with SDA and SCL pins Connect analog pins 4 and 5 of your Arduino Uno board to the SDA and SCL pins of the TMP102 sensor Also connect 5V and the ground as displayed in the following diagram In this example we are using the Arduino Uno board as the master and TMP102 as the slave peripheral where the part address of TMP102 is 0x48 in hex L TX Ta Arduino Note You can obtain the TMP102 sensor breakout board from SparkFun Electronics at https www sparkfun com products 11931 The datasheet of this board can be obtained at https www sparkfun com datasheets Sensors Temperature tmp102 pdf Now connect your Arduino board to your computer using a USB cable and create a new sketch in the Arduino IDE using the following code snippet Once you have selected the appropriate serial port and type of board in the Arduino IDE upload and run the code
349. ping We will be using these two sensors to provide us with digital and analog input values respectively To develop the circuit required for this exercise connect the potentiometer to the analog pin O and the PIR motion sensor to digital pin 11 as displayed in the following diagram wu amuan L TX ME y seceaseensneeeet f Sa MN lo a a E a eee e o e e ee 069 0000000000000000s00s00 eee 069 00000000000000000000s0s80 eee 69 0000000000000000000000 eee eeeeseese eseeeteeeeeeeeeeeeeee eeee eeeeeeeeeeeeeeeeeeeeeeeeeeeeee eeeee3seeeeeeteeeeeeeeeeeeeeeeee U060 0060000000000000000s00000000s0s0s0s0s0 o k n IA eqea q CS S6 a lt u e n 0oEO06 I0 1 10 0 69 000000000000000s00000000000s0s0s0 U69 00000000000000000000000000s0s0s0s0 o o o o e o o eevee ov o o o Connect other Arduino pins such as 5V and the ground as shown in the preceding Fritzing diagram As we are going to use pyFirmata to interface Python with the Arduino board you will have to upload the StandardFirmata sketch to the Arduino board using the method described in Chapter 3 The First Project Motion triggered LEDs Note When you are working with prototyping you really don t need large powerful and computation intensive databases to deal with information The easiest and quickest way to work with sensor data in
350. platform IoT o configuring Your own cloud platform for the IoT o Amazon AWS platform Getting familiar with the Amazon AWS platform cyber physical systems Architecture of IoT web applications O O O O D e data structures o about Data structures o list Lists o tuples Tuples o sets Sets o dictionaries Dictionaries o URL Dictionaries e data types o about Data types void Data types boolean Data types byte Data types int Data types float Data types char Data types o array Data types e DC motors o using DC motor controlling motor speed using PWM o connections Connections o Python code The Python code e deployment stage Tweet a PowerStrip o about Development and deployment stages e design methology IoT projects o about The design methodology for loT projects e development stage Tweet a PowerStrip o about Development and deployment stages e development stages remote home monitoring system o defining Defining the project development stages e do it yourself DIY projects o about Introduction to Arduino e Dual in line Package DIP o about Working with the breadboard e Dynamic Host Control Protocol DHCP o about The Ethernet class O O O 0 0 0 EC2 service o about Getting familiar with the Amazon AWS platform electronic components o interfacing with Arduino Prototyping End of Line EOL o about Playing with a pySerial example Entry widget o about
351. ples to better understand the notion of slicing e You can access a single element in a list as follows gt gt gt myList 0 ta You can access all the elements in the list by having empty start and end values gt gt gt myList a 2 b 12 0 5 2 You can provide start and end index values to obtain a specific subset of the list gt gt gt myList 1 5 2 b 12 0 5 Use of the minus symbol with an index number tells the interpreter to use that index number backwards In the following example 1 backwards actually represents the index number 5 gt gt gt myList 1 1 2 b 12 0 5 You can obtain every other element of the list by providing the increment value with start and end values gt gt gt myList 0 5 2 I a I b I 5 You can check the length of a list variable using the len method The usage of this method will be handy in the upcoming projects gt gt gt len myList 6 You can also perform various operations to add or delete elements in the existing list For example if you want to add an element at the end of the list use the append method on the list gt gt gt myList append 10 gt gt gt myList a 2 b 12 0 5 2 10 To add an element at a specific location you can use the insert i x method where i denotes the index value while x is the actual value that you want to add to the list gt gt gt myList insert 5 hello gt gt g
352. plete you will be able to see the hello world string printed Basically as soon as the Arduino code starts running the Arduino MQTT client will publish the hello world string to the Mosquitto broker for the outTopic topic On the other side that is on the side of the Mosquitto client you ve started using the mosquitto_sub utility and will receive this message as it is subscribed to outTopic Although you ran the modified Arduino example mqtt_basic you can also find the code for this exercise from this chapter s code folder In this exercise the Arduino client is also subscribed to inTopic to receive any message that originates for this topic Unfortunately the program doesn t display or deal with messages it obtains as a subscriber To test the subscriber functionalities of the Arduino MQTT client let s open the mgtt_advance Arduino sketch from this chapter s code folder As you can see in the following code snippet we have added code to display the received message in the callback method The callback method will be called when the client receives any message from the subscribed topics Therefore you can implement all types of functionality on the received message from the callback method void callback char topic byte payload unsigned int length handle message arrived Serial print topic Serial print Serial write payload length Serial println In this mqtt_advance Arduino sketch we have also
353. ponents Now is the time to use the LED that we asked you to get at the beginning of the chapter Before we start wiring the LED let s first understand the physics of it The LED that you obtained should have two legs a short one and a long one The short leg is connected to the cathode of the LED and it needs to be connected to the ground via a resistor As you can see in the following figure we are using a 1 k ohm resistor to ground the cathode of the LED The long leg which is connected to the anode needs to connect to one of the digital pins of the Arduino board As shown in the following figure we have connected the anode to the digital pin number 13 Look at the figure and wire the connection as displayed Make sure that you disconnect the Arduino board from the host computer to avoid any kind of damage from static electricity uu nn i e 0 Short leg Cathode os Long leg Anode ee vr e vr ee vor s o o fritzin In this example we are going to use an LED to test some basic functionalities of the Firmata protocol We have already uploaded the Firmata code to the Arduino board and we are ready to control the LED from the host computer Note The preceding wiring figure was created using an open source tool called Fritzing We are going to cover the Fritzing tool comprehensively in the next chapter as it will be our standard softw
354. ppliances you are trying to operate such as fans lights and so on are rated for similar AC power o You have to ensure that the relays used by the project are compatible with your AC power supply o Arduino works on a DC power supply and it is not affected by any variation in AC power System architecture From the preceding requirements let s sketch the architecture of the Tweet a PowerStrip system The system architecture tries to utilize the hardware components and software tools you learned in the previous chapters while having a relay component as the only exceptional component As you can see in the architecture in the following diagram we are employing the relay to control various home appliances These appliances are usually powered by a common 110V AC power supply available in each home Instead of controlling a single appliance we are implementing a four channel relay to control at least four appliances such as a lamp a fan a toaster and a coffee machine 5 ee EL g Twitter 7 a E aT ET i Arduino u Computation units The relay is controlled using the digital pins of the Arduino Uno board which utilizes the Ethernet Shield to connect to your home network A computation unit that may consist of a computer a Raspberry Pi or a server uses Python and its supporting libraries to access tweets The computation unit also deploys a Mosquitto broker This broker handles the topics from the Python program a
355. ppropriate password to log into the Xively platform Working with Xively The Xively platform lets you create cloud device instances that can be connected to the actual hardware device app or service Perform the following steps in order to work with Xively 1 To begin working with the Xively platform add a device from the main page as displayed in the following screenshot lt gt Development Devices more En Add Device 2 Once you click on the Add Device button it will prompt you to the following window where you will be asked to provide the device name description and privacy status of the device that you are going to assign In the form select a device name that you want your development device to be called provide a brief description and select Private Device as the privacy status Device Name Device Description Privacy t more info Private Device Public Device CCO 1 0 Universal license T Y Add Device Cancel 3 Once you click the Add Device button Xively will create a device instance with automatically generated parameters and prompt you to the development workbench environment On the page of the device that you just added you can see various identification and security parameters such as Product ID Serial Number Feed ID Feed URL and API Endpoint From among these parameters you will frequently need the Feed ID information for the upcoming exercises P
356. pts that you learned in the previous chapters can be utilized to create a wide variety of Arduino based hardware projects The inception of a good application concept always begins with a real world necessity and ends up as a practical project if it is executed properly In this chapter we will demonstrate this project building process with an example of a portable sensor unit As you can estimate from the chapter title we will be building a simple and portable DIY thermostat that can be deployed without a desktop computer or a laptop To begin with we will describe the proposed thermostat with specific goals and processes to achieve them Once the strategy to achieve these goals has been laid down you will be introduced to the two successive programming stages to develop the deployable and portable unit In the first stage we will utilize a traditional computer to successfully develop the program to interface Arduino with Python In the second stage we will replace this computer with a Raspberry Pi to make it portable and deployable Thermostat the project description From the multiple projects that we can build using the things that you learned a project that helps you to monitor your surrounding environment really stands out as an important real world application From the various environment monitoring projects such as weather station thermostat and plant monitoring system we will be developing the thermostat as it focuses on indoor
357. purpose The Amazon Management Console page will let you select other plans if you want to upgrade the current one 7 Launch the Amazon management console As you have an Amazon AWS account now let s create your virtual instance on it Creating a virtual instance on the AWS EC2 service In order to create a virtual instance on Amazon s EC2 platform first log in to AWS using your credentials and open the management console Next click on the EC2 tab and execute the following instructions step by step 1 On the EC2 Console page go to Create Instance and click on the Launch Instance button This will open a wizard to create an instance that will guide you through the setup process Create Instance To start using Amazon EC2 you will want to launch a virtual server known as an Amazon EC2 instance Launch instance Note Your instances w au the US West Oregon regior 2 On the first page of the wizard you will be prompted to select an operating system for your virtual instance Select Ubuntu Server 14 04 LTS as displayed in the next screenshot which is eligible for the free tier To avoid any charges for using an advanced instance make sure that the option you select is eligible for the free tier na Ubuntu Server 14 04 LTS HVM SSD Volume Type ami e7b8c0d7 NS Ubuntu Server 14 04 LTS HVM EBS General Purpose SSD Volume Type Support available from Canonical xs http Avww ubuntu com cloud services 64 bit
358. puter where you have this chapter s folder from the book s source code open the Thermostat_Stage2 py file This file contains the details of the modification required to obtain the optimum size with minor cosmetic changes You will be using this file instead of the one that we used in the previous stage on your Raspberry Pi These adjustments in the code are explained in the following lines of code The first major alteration is in the port name For the Raspberry Pi you need to change the name of the Arduino port from that you were using in the first stage to dev ttyACM0 which is the address assigned to Arduino in the majority of the cases port serial Serial dev ttyACMO 9600 timeout 1 In this program file the size of the Tkinter main window and the matplotlib figure are also adjusted to fit the screen size If you are using a different sized screen change the following lines of code appropriately top minsize 320 160 pyplot figure figsize 4 3 Now with the preceding changes the GUI window should be able to fit within Raspberry Pi s screen As the Raspberry Pi s screen will be used as the dedicated screen for the thermostat application we need to adjust the text size on the screen to fit the window properly Add the font Helvetica 20 text in the declaration of the labels to increase the font size The following line of code shows changes that are performed on the labels to contain the sensor names Tkinter Lab
359. pySerial library Reading a line from the port Once the serial port is opened you can start reading the port using readline The readline function requires the timeout to be specified while initializing the port otherwise the code can terminate with an exception line port readline The readline function will process each line from the port that is terminated with the end line character n Flushing the port to avoid buffer overflow While working with pySerial it is necessary to flush the input buffer to avoid buffer overflow and maintain real time operations port flushInput If the port s baud rate is high and the processing of the input data is slow buffer overflow may occur reducing the speed of execution and making the experience sluggish Closing the port It is a good coding practice to close the serial port once the process is complete This practice can eliminate the port blocking problem once the Python code is terminated port close Summary In this chapter you learned important methods that are required to successfully interface the Arduino board with Python You were also introduced to various prototyping code templates with practical applications These prototyping templates helped us to learn new Python programing paradigms and Firmata methods Later in the chapter we dived further into prototyping by learning more about the different ways of establishing communication between sensors and the Ar
360. quired in advanced applications Internet Hardware layer Router Ethernet Shield a Ethernet Arduino As part of the communication layer Arduino can be connected locally to other computers using USB One can extend the coverage range by utilizing Ethernet Wi Fi or any other radio communication method As illustrated in the following figure the sensor data is collected using computation units for advance processing These computation units are powerful enough to host operating systems and programming platforms In this book we utilized Python to develop various features at the computation layer At this level we performed high level computation tasks such as developing graphical user interfaces using the Tkinter library plotting charts using the matplotlib library and developing web applications using the web py library Internet Router pl Computation layer Python features Serial Ethernet Ethernet Raspberry Pi MQTT Ethernet In all the coding exercises that we performed previously the physical coverage areas of the projects were limited because of hardwired serial interfaces or local Ethernet network as displayed in the following figure r Ethernet Computer Sample architecture of home networking To develop full stack IoT applications we need to remotely access Arduino or host the computation layer on the Internet In this chapter we are goin
361. r GUI design o first program Your first Python GUI program o Python Arduino project remaking Remaking your first Python Arduino project with a GUI e Python packages o installing Installing Python packages o installing pip install PackageName gt version command used Installing Python packages e Python programming o fundamentals The fundamentals of Python programming operators Python operators and built in types Operators built in types Python operators and built in types Built in types comments Python operators and built in types program flow controlling Controlling the flow of your program if statement The if statement for statement The for statement o while statement The while statement e Python software flow Tweet a PowerStrip o about Python software flow e Python threading library o URL Using the paho mgtt Python library e Python tutorials o URL The fundamentals of Python programming The while statement O O O 0 0 0 R e Radiobutton widget o o about The Checkbutton widget selecting LEDs URL The Checkbutton widget selecting LEDs e Raspberry Pi o O O 0 O o o o about What is a Raspberry Pi Raspbian What is a Raspberry Pi versions What is a Raspberry Pi configuring Installing the operating system and configuring the Raspberry Pi operating system installing Installing the operating system and configuring the Raspberry Pi hard
362. r class or method to periodically update the widgets with the latest values In this exercise we will use a potentiometer to provide variable input to the analog pin 0 which will be reflected by Tkinter s Label widget To update the label and display the values of the analog input we are going to implement a few Python and Tkinter tricks As we are using a potentiometer to provide input you will need to change the circuit as displayed in the following diagram before jumping to the Python program eee eeeee eevee eevee TX ME gt Narren HON rss Arduino The Python file for this exercise is located in the code folder as the workingWithLabels py file For this exercise let s run the code first to understand the premise of the exercise Make sure that you have the appropriate string for the Arduino board when you define the port variable On successful execution the program will display the following screenshot and you can click on the Start button to initiate the continuous update of the potentiometer s input value A O O Reading Analog Potentiometer input 0 7429 Start Exit So how did we do this This code contains complex logic and a different program flow compared to what we have done so far As you can see from the code we are using a variable called flag to track the state of the Exit button while continuously running the while loop that monitors and updates the val
363. r the following reasons e We want to demonstrate the functions of both libraries paho mqtt and web py in separate applications e If you want to run routines based on paho mqtt and web py in the same application you will have to implement multithreading as both of these routines need to be run independently e We also want to demonstrate the transfer of information between the two Python programs using Python based REST methods with the help of the httplib library Browser Sensors Arduino Ethernet PubSubClient Mosquitto MQTT broker Computer In this exercise we are labeling humidity and motion sensor information with the topic labels Arduino humidity and Arduino motion respectively The Arduino based MQTT publisher and the Python based MQTT subscriber will be utilizing these topic names if they want to transfer information through the Mosquitto broker Before we begin with implementing the MQTT client on our Arduino let s start the Mosquitto broker on our computer Developing Arduino as the MQTT client The goal of the Arduino MQTT client is to periodically publish the humidity and motion data to the Mosquitto broker running on your computer Open the Step1_Arduino ino sketch from the Exercise 4 MQTT gateway folder in your code repository Like all the other exercises you first need to change the MAC address and the server address value and assign an IP address for your Arduino client Once you are done with
364. ram shows an example of the I2C communication bus resistors AMAA m Pull up SDA 12C Master Microcontroller od Q Y 12C Slave 12C Slave 12C Slave Peripheral Peripheral Peripheral Device 1 Device 2 Device 3 As displayed in the preceding diagram the master device contains two bidirectional lines Serial Data Line SDA and Serial Clock Line SCL In the case of Arduino Uno the analog pins 4 and 5 provide interfaces for SDA and SCL It is important to note that these pin configurations will change with different variants of the Arduino board The peripheral sensors that are working as slaves connect to these lines which are also supported by the pull resistors The master device is responsible for generating the clock signal on the SCL and initializing communication with the slaves The slave devices receive the clock and respond to the commands sent by the master device The order of the slave devices is not important as the master device communicates with the slaves using their part address To initialize the communication the master sends one of the following types of message on the bus with the specific part address e A single message in which data is written on the slave e A single message in which data is read from the slave e Multiple messages in which first data is requested from the slave and then the received data is read To support I2C protocol in Arduino programming the
365. rd using pyFirmata and the setup pins to obtain the sensor values As you can see in the following line of code after setting up the Arduino board and pyplot interactive mode we initialized the plot with a set of blank data in our case pData 0 25 This array for y values pData is then used to append values from the sensor in the while loop The while loop keeps appending the newest values to this data array and redraws the plot with these updated arrays for the x and y values In this example we are appending new sensor values at the end of the array while simultaneously removing the first element of the array to limit the size of the array pData append float a0 read del pData 0 The set_xdata and set_ydata methods are used to update the x and y axes data from these arrays These updated values are plotted using the draw method on each iteration of the while loop 11 set_xdata i for i in xrange 25 11 set_ydata pData update the data pyplot draw update the plot You will also notice that we are utilizing an xrange function to generate a range of values according to the provided length which is 25 in our case The code snippet i for i in xrange 25 will generate a list of 25 integer numbers that start incrementally at 0 and end at 24 Integrating plots in the Tkinter window Due to the powerful integration capabilities of Python it is very convenient to interface the plots generated by the matpl
366. rduino project with a GUI Just to refresh your memory I would like to remind you that we created a motion detection system that generated alerts by blinking the red LED when a motion was detected While working with the project we were printing the state of the proximity sensor onto the Python prompt In this exercise we are going to use the concepts that you learned in the previous exercises and we will create an interface for our project As part of this exercise you have to connect the same circuit that we used in Chapter 3 The First Project Motion triggered LEDs Make sure you have the exact same circuit with the PIR sensor and the LEDs before you move ahead Once you are ready with your hardware open the firstProjectwithGUI py file from the code folder of this chapter In the code change the appropriate port values and run the GUI for the project As you can see in the pin assignments we now have three digital pins two of them as outputs and one as an input The output pins are assigned to the red and green LEDs while the input pin is assigned to the PIR motion sensor If the PIR sensor is in idle mode we will perform a onetime read operation to wake up the sensor pirPin board get_pin d 8 i redPin board get_pin d 10 0 greenPin board get_pin d 11 0 pirPin read One of the important functions that is implemented by the code is blinkLED This function updates the Label widget that is assigned to describ
367. rduino board Now create a Python executable file using the following code snippet Change the value of port COM5 if needed to an appropriate port name as required by your operating system Finally run the program import time from PyMata pymata import PyMata Initialize Arduino using port name port PyMata COM5 Configure I2C pin port i2c_config port ANALOG 4 5 One shot read asking peripheral to send 2 bytes port i2c_read 0x48 0 2 port I2C_READ Wait for peripheral to send the data time sleep 3 Read from the peripheral data port i2c_get_read_data 0x48 Obtain temperature from received data TemperatureSum data 1 lt lt 8 data 2 gt gt 4 celsius TemperatureSum 0 0625 print celsius fahrenheit 1 8 celsius 32 print fahrenheit firmata close On the execution of the preceding code snippet you will be able to see the temperature reading in Fahrenheit and Celsius As you can see from the inline comments in the code the first step to utilize Arduino using PyMata is to initialize the port using the PyMata constructor PyMata supports the configuration of I2C pins via the i2c_config function PyMata also supports simultaneous reading and writing operations via the i2c_read and i2c_write functions Interfacing BH1750 using PyMata In the case of BH1750 the previous PyMata code snippet can be utilized with minor modifications to obtain ambient light sensor data As the
368. rdware platform of choice The following image shows the basic version of the Arduino board which is called Arduino Uno Uno means one in Italian L TX ME w rss Arduino Arduino variants Like any other project hardware requirements are driven by project specifications If you are developing a project that requires you to interface with a large number of external components you need a prototyping platform that has a sufficient number of input output I O pins for interfacing If you are working on a project that needs to perform a huge amount of complex calculations you require a platform with more computation capability Fortunately the Arduino board exists in 16 different official versions and each version of Arduino differs from the others in terms of form factor computational power I O pins and other on board features Arduino Uno is the basic and most popular version which is sufficient enough for simple DIY projects For the majority of exercises in this book we will be using the Arduino Uno board You can also use another popular variant called Arduino Mega which is a larger board with extra pins and a powerful microcontroller The following table shows the comparison of some of the more popular and active variants of the Arduino board frequency PWM 1 O am IATmegal68v or Any of these variants can be programmed using a common integrated development environment called Arduino IDE which is described in the upc
369. rent levels of learning curves for first time Python programmers Now as this book is dedicated to Python programming for Arduino based projects we can t spend a large amount of time learning the nitty gritty of a specific framework Instead we will choose our interface library based on the following criteria e Ease to install and get started e Fase to implement with negligible learning efforts e Use of minimum computational resources The framework that satisfies all these requirements is Tkinter https wiki python org moin TkInter Tkinter is also the default standard GUI library deployed with all Python installations Note Although Tkinter is the de facto GUI package for Python you can learn more about other GUI frameworks that were mentioned earlier from their official websites which are as follows wxPython http www wxpython org PyGTK http www pygtk org PySide http gt project org wiki PySide PyQt http sourceforge net projects pygt Learning Tkinter for GUI design Tkinter short for Tk interface is a cross platform Python interface for the Tk GUI toolkit Tkinter provides a thin layer on Python while Tk provides the graphical widgets Tkinter is a cross platform library and gets deployed as part of Python installation packages for major operating systems For Mac OS X 10 9 Tkinter is installed with the default Python framework For Windows when you install Python from the installation file Tkinter gets ins
370. riable to alternatively use elements of the pattern array to control the buzzer Once the entire recurrence loop is complete we will turn off the buzzer completely again if it is on and safely disengage the board using the exit method def buzzerPattern pin recurrence pattern pattern1 0 8 0 2 pattern2 0 2 0 8 flag True for i in range recurrence if pattern p patterni elif pattern p pattern2 else print Please enter valid pattern 1 or 2 exit for delay in p if flag is True board digital pin write 1 flag False sleep delay else board digital pin write 0 flag True sleep delay board digital pin write 0 board exit Tip If you want to change the time delays or implement a totally different pattern you can play around with the pattern arrays The remaining part of the program is relatively simple as it contains code for importing libraries and initializing the Arduino board Once the board is initialized we will execute the buzzerPattern function with the input argument 2 10 1 This argument will ask the function to play pattern1 10 times on the pin number 2 from pyfirmata import Arduino from time import sleep port dev cu usbmodemfa1331 board Arduino port sleep 5 buzzerPattern 2 10 1 DC motor controlling motor speed using PWM DC motors are widely used in robotics applications They are available in a wide range of voltage specifications depen
371. rivate Device H Acti d Deactivate 4 A unique and secure API key of the newly created device is also located in the right hand side bar of the page This API key is very important and needs to be secured just like your password as anyone with the API key can access the device API Keys Auto generated Arduino device key for feed 1649696305 permissions 5 Now to remotely access this device open the terminal and use the CURL command to send data to it In the following command change the lt Your_Feed_ID gt and lt Your_API_key gt values with the ones available for your device curl request PUT data 0 10 header X ApiKey lt Your_API_key https api xively com v2 feeds lt Your_Feed_ID gt csv 6 As you can see the previous command sent the value of 10 on channel 0 of your device on Xively After executing the previous command you will notice that the Xively workbench is updated with the information that you just sent using CURL Channels a minute ago N Graphs o 10 s Add Channel 7 Try sending multiple values on channel 0 using the previous command On the Xively workbench you will be able to see a plot being generated by these values in real time Access the plot by clicking on channel 0 in the workbench Channels a minute ago N Graphs 0 2 a minute ago lt 30 minutes Z Edit Delete Using the method that we used in this example we can also configure Arduino
372. rks in any form on the Internet please provide us with the location address or website name immediately so that we can pursue a remedy Please contact us at lt copyright packtpub com gt with a link to the suspected pirated material We appreciate your help in protecting our authors and our ability to bring you valuable content Questions If you have a problem with any aspect of this book you can contact us at lt questions packtpub com gt and we will do our best to address the problem Chapter 1 Getting Started with Python and Arduino This chapter introduces the Python programming language and the open source electronic prototyping platform Arduino The first section of the chapter focuses on Python and briefly describes the benefits of Python along with installation and configuration steps The remaining part of the chapter describes Arduino and Arduino s development environment At the end of this chapter you will have configured a programming environment for both Python and Arduino for your favorite operating system If you are a beginner with either or both platforms that is Python and Arduino it is advisable that you follow the given steps in this chapter as the later chapters will assume that you have the exact configuration described here If you have previous experience of working with these platforms you can skip to the next chapter Introduction to Python Since its introduction by Guido van Rossum in 1991 Py
373. roject The overall hardware and software development process is also aligned with these three units and can be distributed as follows e Monitoring station development stage e Control center development stage e Web application development stage The software development for the monitoring station stage includes developing the Arduino code to monitor sensors and perform actuator actions on one side while publishing this information to the control center on the other side The middle layer of the development stage that is the Raspberry Pi based control center hosts the Mosquitto broker This stage also contains the Python program that contains the GUL situation awareness logic and subroutines to communicate with the Xively cloud service The last stage the cloud services includes two distinct components sensor data relay and a web application We will be using the Xively platform as our sensor data relay and the web application will be developed in Python on the Amazon AWS cloud instance Now let s jump into the actual development process and our first stop will be the Arduino based monitoring station Stage 1 a monitoring station using Arduino As we discussed the main tasks of the monitoring systems are to interface sensor components and communicate the information generated by these sensors to the observers You will be using Arduino Uno as the central microcontroller component to integrate these sensors and actuators We also need
374. rom DIY project prototypes you will need an additional layer of features on top of basic functionalities These features actually make things convenient for a user when they interact with the system The other distinguishable feature is the tangibility of the system which makes large scale production and support possible Although there are plenty of features that you can implement we recommend the following major improvements to elevate the level of the current project Utilizing multiple monitoring stations In this project we developed a monitoring station as a prototype with a range of functionality that is demonstrated by a remote home monitoring system A remote monitoring system can have multiple numbers of monitoring stations to cover various geographical locations such as different rooms inside a house or different office cubicles Basically a large number of monitoring stations can cover an extended area and provide efficient surveillance of the domain that you are trying to monitor If you want to extend the current project with an array of monitoring stations you will require some of the following modifications e Each monitoring station can have its own control center or a centralized control center for all of them depending upon the application requirements e You will have to update the Python code for the control center to accommodate the changes Examples of these changes include modifying topic titles for MQTT coordinating
375. rovides a very efficient way to capture exceptions in Python It is advisable to utilize this statement throughout the development process to cleverly debug your programs You can learn about Python errors and exceptions from the following links e https docs python org 2 reference compound_stmts html try e https docs python org 2 tutorial errors html Buzzer generating sound alarm pattern Digital buzzer sensors are used in various applications that require alarm notifications These sensors produce sound when they are supplied with a digital HIGH value that is 5V which can be provided by using Arduino digital pins Similar to the LED example in the previous chapter they are very easy to interface with Arduino However rather than performing a simple digital output we are implementing Python programming tricks to generate different sound patterns and produce various sound effects The same code template can be also used to produce different LED blink patterns Note An analog digital buzzer can be found at http www amazon com Arduino Compatible Speaker arduino sensors dp B0090X0634 Connections As displayed in the following circuit diagram connect the VCC and the ground of the sensor board to 5V and the ground pin of the Arduino board respectively Connect the signal pin of the sensor to the digital pin 2 via the 220 ohm resistor You can use any digital pin to connect the buzzer Just make sure that you update the Python
376. rovides comprehensive tutorials for beginners to get started with Python programming It is highly recommended that you visit the official Python tutorials at https docs python org 2 tutorial index html if you are looking for detailed programming tutorials as compared to the upcoming brief overviews Python operators and built in types Now that you have a brief idea regarding the Python prompt let s get you familiar with some of the basic Python commands For these exercises we will be using the Python IDLE which also opens with the Python interactive prompt You will require a method to describe the code segments tasks and comments when writing large and complex code Non executable content is called comments in any programming language and in Python they start with the hashtag character Like comments you will be frequently required to check the output by printing on the prompt using the print command gt gt gt Fundamental of Python gt gt gt My first comment gt gt gt name John This is my name gt gt gt print name John Note Instead of IDLE you can also access the Python interactive prompt from the terminal When using Python from the terminal make sure that you are taking care of the indentation properly Operators Python supports the usage of basic mathematical operators such as and directly from the interpreter Using these operators you can perform basic calculations in the promp
377. rsion of the onStartButtonPress function we will obtain the ledBrightness value by using the get method on the brightnessScale widget object where the get method will return the value of the current location of the slider As the PWM input requires values between 0 and 1 and the obtained slider value is between 0 and 100 we will convert the slider value into the appropriate PWM input by dividing it with 100 This new value will then be used with the write method and this will ultimately turn on the LED with the applied brightness for the time period that is provided by the timePeriodEntry value def onStartButtonPress timePeriod timePeriodEntry get timePeriod float timePeriod ledBrightness brightnessScale get ledBrightness float ledBrightness startButton config state Tkinter DISABLED ledPin write ledBrightness 100 0 sleep timePeriod ledPin write 0 startButton config state Tkinter ACTIVE For information about the Scale widget you can refer to http effbot org tkinterbook scale htm Now run the exampleScale py file You will be able to see the following screenshot with the Entry and Scale widgets Enter the time delay drag the slider to the brightness that you want and then click on the Start button Me O O Brightness using 32 You will be able to see the LED light up with the brightness set by the Scale widget Once the LED is turned off after the given time delay you can reset the slider
378. rts the pyfirmata library to the interpreter It also defines the pin number and the port gt gt gt import pyfirmata gt gt gt pin 13 gt gt gt port dev ttyACM0 After this we need to associate the port with the microcontroller board type gt gt gt board pyfirmata Arduino port While executing the previous script two LEDs on the Arduino will flicker as the communication link between the Python interpreter and the board gets established In the Testing the Firmata protocol section we used a prebuilt program to turn an LED on and off Once the Arduino board is associated to the Python interpreter these functions can be performed directly from the prompt You can now start playing with Arduino pins Turn on the LED by executing the following command gt gt gt board digital pin write 1 You can turn off the LED by executing the following command Here in both commands we set the state of digital pin 13 by passing values 1 High or o Low gt gt gt board digital pin write 0 Similarly you can also read the status of a pin from the prompt gt gt gt board digital pin read If we combined this script in an executable file with a py extension we can have a Python program that can be run directly to control the LED rather than running these individual scripts on a terminal Later this program can be extended to perform complex functions without writing or changing the Arduino sketc
379. rtual machine This instance includes 750 hours of free usage time per month and this is greater than the number of hours in any month thereby making it free for the entire month The data storage capacity and bandwidth of the AWS account are sufficient for basic IoT or Arudino projects To create a free account for a year on Amazon s AWS cloud platform perform the following steps 1 Open http aws amazon com and click on the button that asks you to try AWS for free or some other similar text 2 This action will lead you to a Sign In or Create an AWS Account page as displayed in the following screenshot Enter the e mail address that you want to use for this account when you select the I am a new user option and click on the Sign in using our secure server button If you already have an AWS account and you know how to create an account on Amazon AWS you can use those credentials and skip to the next section Sign In or Create an AWS Account You may sign in using your existing Amazon com account or you can create a new account by selecting I am a new user My e mail address is I am a new user I am a returning user and my password is Forgot your password Has your e mail address changed Note Amazon only allows one free instance for each account If you are an existing AWS user and your free instance is already occupied with another application you can use the same instance to accommodate the MQTT broker
380. s Pack geometry manager o about The Pack geometry manager paho matt library o about MQTT on Python using paho matt o installing Installing paho matt o using Using the paho matt Python library passive infrared PIR sensor o about The project goal o using The list of components o URL The list of components PEP 8 o URL Operators physical systems Getting started with the loT pinMode function o about The pinMode function pip o installing Installing pip plot function o about Plotting random numbers using matplotlib portable TFT LCD display o using Using a portable TFT LCD display with the Raspberry Pi o connecting GPIO used Connecting the TFT LCD using GPIO o configuring with Raspberry Pi OS Configuring the TFT LCD with the Raspberry Pi OS o GUI optimizing Optimizing the GUI for the TFT LCD screen potentiometer o connections Connections o Python code The Python code PowerSwitch Tail o URL PowerSwitch Tail Processing o about Introduction to Arduino programming protocols o about Networking fundamentals prototyping o about Prototyping prototyping thermostat o about Stage 1 prototyping the thermostat Arduino sketch The Arduino sketch for the thermostat temperature sensor interfacing Interfacing the temperature sensor humidity sensor interfacing Interfacing the humidity sensor light sensor interfacing Interfacing the light sensor 0 o Oo 0 o
381. s configuring with direct method The direct method pin modes assigning Assigning pin modes working with Working with pins data reporting Reporting data monitoring Manual operations write method using The write method read method using The read method e Arduino programming Oo o o o about Introduction to Arduino programming comments Comments variables Variables constants Constants Oo o 0 o data types Data types conversion functions Conversions statements Functions and statements functions Functions and statements Arduino sketch monitoring station o o 0 o about The Arduino sketch for the monitoring station sensor information publishing Publishing sensor information actuator actions subscribing to Subscribing to actuator actions interrupt programming Programming an interrupt to handle the press of a button Arduino WiFi Shield Oo o about Arduino WiFi Shield URL Arduino WiFi Shield Arduino Y n o o about Arduino Y n URL Arduino Y n array data type o about Data types BH1750 light sensor o interfacing Arduino used Arduino coding for the BH1750 light sensor o interfacing PyMata library used Interfacing BH1750 using PyMata boolean data type o about Data types breadboard o using Working with the breadboard o URL Working with the breadboard o history Working with the breadboard o re
382. s o reference link Connections e troubleshooting o Tweet a PowerStrip Testing and troubleshooting e troubleshooting Arduino board connection o about Troubleshooting e Tweet a PowerStrip project overview Project overview project requirements Project requirements system architecture System architecture hardware components Required hardware components user experience flow User experience flow development stage Development and deployment stages deployment stage Development and deployment stages smart power strip with Arduino Stage 1 a smart power strip with Arduino and relays hardware design Hardware design Arduino code The Arduino code Python code Stage 2 the Python code to process tweets The Python code Python software flow Python software flow Twitter application setting up Setting up the Twitter application testing Testing and troubleshooting troubleshooting Testing and troubleshooting o multiple features adding Extending the project with additional features e Twitter application Tweet a PowerStrip o setting up Setting up the Twitter application O O O O 0 O O O O 0 0 0 0 O O O O 0 O Ubuntu o Python installing Ubuntu o matplotlib setting up Setting up matplotlib on Ubuntu Ubuntu Linux o SD card preparing Preparing an SD card Universal Serial Bus USB o about Using the Serial Monitor window Uno board o about The Arduino Uno board user experienc
383. s on the board stop flashing Now you have your Arduino board ready with your first sketch You can observe the performance of the blinking LED near digital pin 13 Using the Serial Monitor window In the previous process we used a Universal Serial Bus USB cable to connect your Arduino board to a USB port of your computer The USB port is an industrial standard to provide an interface for connecting various electronic components to a computer using the serial interface When you connect an Arduino board using USB the computer actually interfaces it as a serial peripheral device Throughout the book we are going to refer to the connections made using a USB as serial connections The Serial Monitor window is a built in utility of the Arduino IDE The Serial Monitor window can be accessed by navigating to Tools Serial Monitor or by using the Ctrl Shift M keyboard shortcut It can be configured to observe data that is being sent or received on the serial port that is used to connect the Arduino board to the computer You can also set the baud rate for the serial communication using the drop down menu option This utility is going to be very useful further on in the book when testing your prototypes and their performances Introduction to Arduino programming The Arduino platform was introduced to simplify electronic hardware prototyping for everyone For this reason Arduino programming was intended to be easy to learn by nonprogrammers suc
384. s processor storage device and basic adaptors for expansion This makes a single board computer an appropriate candidate for portable applications as they can be part of the portable hardware device that we are trying to create Although there were a number of single board computers in the market before the introduction of the Raspberry Pi the open source nature of the hardware and the economical price are the main reasons behind the popularity and rapid adoption of the Raspberry Pi The following figure shows the Raspberry Pi Model B with its major components RCA VIDEO AUDIO LEDS USB SD CARD POWER The computational capabilities of the Raspberry Pi are adequate for running a trimmed down version of Linux OS Although people had tried to use many types of operating systems on a Raspberry Pi we will be using the default and recommended operating system called Raspbian Raspbian is a Debian distribution based open source Linux OS which is optimized for the Raspberry Pi The Raspberry Pi uses an SD card as the storage device which will be used to store your OS and program files In Raspbian you can avoid running the unnecessary OS components that are shipped with traditional OSes These include the Internet browser communication application and in some cases even the graphical interface After its introduction the Raspberry Pi has gone through a few major upgrades The earlier version called Model A did not include the Et
385. s a layout similar to a regular Arduino board but it has eight instead of six analog ports Therefore the preceding dictionary object can be customized as follows nano digital tuple x for x in range 14 analog tuple x for x in range 8 pwm 3 5 6 9 10 11 use_ports True disabled 0 1 Rx Tx Crystal e As you have already synchronized the Arduino board earlier modify the layout of the board using the setup_layout layout method board setup_layout nano This command will modify the default layout of the synchronized Arduino board to the Arduino Nano layout or any other variant for which you have customized the dictionary object Configuring Arduino pins Once your Arduino board is synchronized it is time to configure the digital and analog pins that are going to be used as part of your program Arduino board has digital I O pins and analog input pins that can be utilized to perform various operations As we already know some of these digital pins are also capable of PWM The direct method Now before we start writing or reading any data to these pins we have to first assign modes to these pins In the Arduino sketch based approach that we used in the previous chapter we used the pinMode function that is pinMode 11 INPUT for this operation Similarly in pyFirmata this assignment operation is performed using the mode method on the board object as shown in the following code snippet
386. s e print HTTPError 0 1 format e errno e strerror print Requested channel doesn t exist Once the datastream object is initialized the latest available value from the channel can be obtained using the datastream current_value method latestValue datastream current_value To enable the complete code to perform this exercise open the downloadXivelyBasic py code and change the values for the feed ID and API key to the appropriate ones In this exercise we are working with the Random channel that we created in the uploading exercise Before you execute this Python code you need to execute the uploadXivelyBasic py file that will continuously provide random data to the Random channel Now you can execute the downloadXivelyBasic py file that will fetch the current value of the Random channel periodically with a delay specified by the sleep function As you can see in the following screenshot we are getting a new value for the Random channel every 10 seconds 600 C 4_DownloadBasicXively bash 77x10 A Sachis Mac mini 4_DownloadBasicXively sachi3 python downloadBasicXively py Latest received value from Random channel 0 6314564168582527 Latest received value from Random channel 0 5755476505627495 Latest received value from Random channel 0 32560490434041245 Latest received value from Random channel 0 7624863557473238 7624863557473238 5902151037585202 06681308258035812 06681308258035812 06681308
387. s the project let s put a twist in the blinking LED project In this project we will blink two different LEDs but instead of performing these actions in a random manner we will do it for events that are measured using a motion sensor Although the difficultly level of the project is simple since it is your first project it carries real world application value and can be used as a simple application in your day to day life The project goal The project goal can be described in one sentence as follows Generate an alert using a red LED for any detected motion and display the normal condition using a green LED In comprehensive list of goals you will have to perform the following tasks to satisfy the mentioned project goal e Detect any motion in the environment as an event using a passive infrared PIR sensor e Perform a blink action using a red LED for this event e Otherwise perform a blink action using a green LED e Keep the system in loop after the action has been performed and wait for the next event The project can be implemented as a DIY application or as part of other projects with minor modifications The following are some examples where the concepts from this project can be utilized e Asa DIY security system to monitor movement in a room http www instructables com id PIR Sensor Security e In smart home applications it can be used to automatically turn off lights if no one is present http www instructables
388. s we discussed in an earlier chapter the first program while learning any programming language includes printing Hello world Now as we are starting Python programming for GUI let s start by printing the same string in a GUI window instead of a prompt Just to start with GUI programming we are going to execute a Python program and then jump into explaining the structure and the details of the code Let s create a Python executable file using the following lines of code name it helloGUI py and then run it The execution process should complete without any dependency errors import Tkinter Initialize main windows with title and size top Tkinter Tk top title Hello GUI top minsize 200 30 Label widget helloLabel Tkinter Label top text Hello World helloLabel pack Start and open the window top mainloop You should be prompted with the following window on the successful execution of the preceding code snippet As you can see the Hello World string has been printed inside the window and has Hello GUI as the title of the window O O Hello GUI Hello World So what exactly happened As you can see from the code snippet we instantiated various Tkinter widgets one by one to obtain this result These widgets are the building blocks for any Python GUI application that is developed using Tkinter Let s start with the first and the most important widget Tk The root widget Tk and the top level methods
389. s you are planning to use any other location on your virtual instance At this location create a new empty directory named project by using following command mkdir project Now on the computer you are working on Mac OS X or Linux open another terminal window and use the following command to copy the entire directory to the remote instance scp v i test pem r lt project folder path gt ubuntu lt your ec2 static ip gt project Once you have successfully copied the files to this location you can go back to the terminal that is logged in to your virtual instance and change the directory to project cd project Before running any commands make sure that you have changed the appropriate IP addresses in the Arduino sketch and the Python programs You will have to replace the previous IP address with the one of your virtual instance Now that you have made these changes you can execute the Python code containing the Mosquitto Gateway and web application to start the program Open your web browser from the http lt Public Ip gt 8080 location to see you web application running on the custom IoT platform From now on you should be able to access this application from any remote location through the Internet Tip Do not forget to change the IP address of the Mosquitto broker in the Arduino sketch and upload the sketch to the Arduino board again You may not be able to obtain the sensor data if the appropriate IP address
390. s you want to extend the previous stage of the project to a device that can be used on a regular basis If you are referring to the project to just learn Python programming you can skip this entire section The following is an image of the Raspberry Pi Model B e e oo co e e e e e E s a s a e e T Do Ma AN Om i9 3h m uine AET VUEN If you haven t worked with a single board computer before you may have a lot of unanswered questions such as What exactly does a Raspberry Pi consists of What are the benefits of using a Raspberry Pi in our project and Can t we just use Arduino for that These are legitimate questions and we will try to answer them in the following section What is a Raspberry Pi The Raspberry Pi is a small almost the size of a credit card single board computer that was developed with the initial aim of helping students learn the basics of computer science Today the Raspberry Pi movement guided by the Raspberry Pi Foundation has turned into a DIY phenomenon and captured the attention of enthusiasts and developers around the world The capabilities and features shipped with a Raspberry Pi at a nominal cost 35 have boosted the popularity of the device The term single board computer is used for devices that have all the necessary components to run an operating system on one board such as a processor RAM graphic
391. ser These requests for the root location will be handled by the index class just as we covered in exercise 2 urls index data data The data class takes care of any POST request originating from the data location In this case these POST requests contain payload that has sensor information attached by the Arduino POST client On receiving the message the method splits the payload string into sensor type and value updating the global value of the humidity variable in this process class data def POST self global humidity i web input data web data data data split 1 humidity relativeHumidity data temperature return humidity Each POST request received from Arduino updates the raw humidity value which is represented by the data variable We are using the same code from exercise 2 to obtain manual temperature values from the user The relative humidity value humidity is updated according to the temperature value you updated using the web browser and the raw humidity value is obtained from your Arduino eco 10 0 0 20 8080 y E gt C 10 0 0 20 8080 2 ju Arduino POST request to Web py Use following form to manually enter temperature value to obtain relative humidity Default temperature is 25 C Temperature 15 submit Relative Humidity is 19 3822393518 To check out the Python code open the WebPyEthernetPOST py file from the code repository After making
392. so called network nodes that allow the exchange of data between these devices These network nodes include various devices such as your personal computers mobile phones servers tablets routers and other pieces of networking hardware A computer network can be classified into numerous types according to parameters such as geographical location network topology and organizational scope In terms of geographical scale a network can be categorized into local area network LAN home area network HAN wide area network WAN and so on When you are utilizing your home router to connect to the Internet you are using the LAN created by your router With regards to the organization that handles the network LAN can be configured as Intranet Extranet and Internet The Internet is the largest example of any computer network as it interconnects all types of networks deployed globally In your implementation of various projects throughout this book you will mostly be using your LAN and the Internet for the exchange of data between an Arduino your computer the Raspberry Pi and the cloud services To standardize communication between network nodes various governing bodies and organizations have created a set of rules called protocols In the large list of standard protocols there are a few protocols that your computer uses on a daily basis The examples of those protocols associated with the local area network include Ethernet and Wi Fi In the
393. spberry Pi is connected to the local home network and to the Internet through it It s time to update the existing packages and install the required ones To update the Raspberry Pi s existing system execute the following commands in the terminal sudo apt get update sudo apt get upgrade 4 Once your system is updated with the latest version it s time to install the Mosquitto broker on your Raspberry Pi The Raspbian OS has Mosquitto in the default repository but it doesn t have the current version that we need To install the latest version of Mosquitto execute following commands in the terminal curl O http repo mosquitto org debian mosquitto repo gpg key sudo apt key add mosquitto repo gpg key rm mosquitto repo gpg key cd etc apt sources list d sudo curl 0 http repo mosquitto org debian mosquitto repo list sudo apt get update sudo apt get install mosquitto mosquitto clients WAR 5 To install other Python dependencies let s first install the Setuptools package using apt get sudo apt get install python setuptools 6 Using Setuptools we can now install all the required Python libraries such as paho_mqtt xively python and web py sudo easy_install pip sudo pip install xively python web py paho_mqtt Now that we have installed all the necessary software tools that are required to run our control center on the Raspberry Pi it is time to configure the Raspberry Pi so that it can provide uninterrup
394. specified digital pin while also printing message on the terminal It also introduces delay to simulate the blinking action def blinkLED pin message print message board digital pin write 1 sleep 1 board digital pin write 0 sleep 1 Testing You can start testing the project as soon as you run the Python code on the terminal If everything goes according to design you should be able to see the following output in the terminal Python 2 7 4 Shell File Edit Shell Debug Options Windows Help 2 7 4 default Sep 26 2013 03 20 56 1 3 on linux2 copyright credits or license for more information Motion Detected Motion Detected Motion Detected No motion Detected No motion Detected No motion Detected No motion Detected Motion Detected Motion Detected No motion Detected No motion Detected You should be able to see the Motion Detected string on the terminal when any motion is detected by the PIR sensor If you find any abnormal behavior in the output then please check the Python code A benefit of using Python is that minor modifications such as changing the blinking speed or swapping roles of the LEDs can be performed by just changing the Python code without dealing with the Arduino or the electrical circuit Troubleshooting When you run the project you might require troubleshooting for the following probable problems e Serial output is correct but there are no blinking LEDs
395. supply Power rails Note Find out more about breadboards and the tutorials to use them at http learn sparkfun com tutorials how to use a breadboard A breadboard mostly has two types of connection strips terminal strips and power rails As displayed in the preceding figure terminal strips are vertical columns with electrically shorted holes In simple words once you connect any component to one of the terminal strips the component will be electrically connected to each hole in the column The columns of terminal strips are separated by the Dual in line Package DIP support gap DIP is acommon housing for electronics components In the same column terminal strips above and below the DIP support gap are electrically independent Meanwhile the power rails are shorted horizontally throughout the entire row of the breadboard The power rails are mostly used to connect positive and ground connections from the power supply so it can be distributed easily to all components Note History of breadboards In the early years of electronics people used actual breadboards that were used to cut bread to connect their large components with just nails and wires Once electronics components started getting smaller the board to assemble circuits also became better The term stuck through this evolution and we still call the modern boards breadboards If you are interested you can check out http www instructables com id Use a real Bread
396. supported methods visit https docs python org 2 library threading html To better understand our implementation of the threading method check out the following code snippet As you can see in the code we are implementing recursion for the publishTest function every 5 seconds using the Timer threading method Using this method the program will start a new thread that is separate from the main program thread that contains the loop for Mosquitto Every 5 seconds the publishTest function will be executed recursively running the publish method and ultimately publishing a message for inTopic import threading def publishTest cli publish inTopic From Python threading Timer 5 publishTest start Now in the main thread when the client gets a new message from the subscribed topics the thread invokes the onMessage function In the current implementation of this function we are just printing the topic and message for demonstration purposes In real applications this function can be used to implement any kind of operation on the received message for example writing a message to a database running an Arduino command selecting an input calling other functions and so on In short this function is the entry point of any input you receive through the Mosquitto broker from your subscribed topics def onMessage mosq obj msg print msg topic msg payload Similarly every time you publish a message from the secon
397. t Fan off if lampStatus report Lamp on else report Lamp off if toasterStatus report Toaster on else report Toaster off if coffeemakerStatus report Coffeemaker on else report Coffeemaker off report toCharArray reportChar 100 client publish PowerStrip statusreport reportChar Just as we did in the previous project you can set up the code to periodically send keep alive messages to avoid the termination of the connection with the Mosquitto broker Once you are ready with the code connect the Ethernet cable compile the code and then upload it to your Arduino Your Arduino should be in receiving mode now and it will wait for the message from the subscribed channels As we discussed in the previous the project you need to ensure that your Mosquitto broker is running on the server IP address you specified in the Arduino code Stage 2 the Python code to process tweets As the user is interacting with the system at the level of the Twitter application we do not require a deployable computation or control unit for this project Due to this we can just use any computer capable of hosting Python and Mosquitto as the computation unit You still need to ensure that the unit is always on and connected to the Internet otherwise the system will not work as expected For simplicity you can deploy the system on the Raspberry Pi based control center that you developed in the previous proj
398. t Start command onStartButtonPress startButton pack In this initialization the function associated with the button is onStartButtonPress and the Start string is displayed as the title of the button Similarly the top object specifies the parent or the root widget Once the button is instantiated you will need to use the pack method to make it available in the main window In the preceding lines of code the onStartButonPress function includes the scripts that are required to blink the LEDs and change the state of the button A button state can have the state as NORMAL ACTIVE Or DISABLED If it is not specified the default state of any button is NORMAL The ACTIVE and DISABLED states are useful in applications when repeated pressing of the button needs to be avoided After turning the LED on using the write 1 method we will add a time delay of 5 seconds using the sleep 5 function before turning it off with the write 0 method def onStartButtonPress startButton config state Tkinter DISABLED ledPin write 1 LED is on for fix amount of time specified below sleep 5 ledPin write 0 startButton config state Tkinter ACTIVE At the end of the program we will execute the mainloop method to initiate the Tkinter loop Until this function is executed the main window won t appear To run the code make appropriate changes to the Arduino board variable and execute the program The following screenshot with a button and ti
399. t as shown in the following examples Try these operations in your prompt in order to start using the Python interpreter as a calculator gt gt gt 2 2 4 gt gt gt 2 3 1 7 gt gt gt 2 3 5 1 Note When working with the Python interpreter it is recommended that you follow the Style Guide for Python Code which is also popularly known as PEP 8 or pep8 For more information about PEP 8 visit https www python org dev peps pep 0008 Built in types Python is a dynamically typed language which means that you don t have to explicitly declare the type of the variables when initializing them When you assign a value to a variable the Python interpreter automatically deduces the data type For example let s declare the following variables in the interactive mode of the interpreter gt gt gt weight height 5 gt gt gt weight height 25 gt gt gt type weight lt type int gt While assigning the value to the weight variable we didn t specify the data type but the Python interpreter assigned it as an integer type int The interpreter assigned the int type due to the reason that the numerical value didn t contain any decimal points Let s now declare a variable with a value containing a decimal point The built in function type that can be used to find out the data type of a specified variable gt gt gt length 6 0 gt gt gt weight height length 150 0 gt gt gt type leng
400. t gt gt sq Python programming for Arduino n Bye n gt gt gt f writelines sq The close method The close method closes the file and free system resources that are occupied by the file Once they are closed you can t use the file object as it has been flushed already It is a good practice to close the file once you are done working with a file gt gt gt f close The read method This read method reads the content of an opened file from the beginning to the end To use this method you need to open the file with one of the reading compatible modes such as w r r OF at gt gt gt f open test txt r gt gt gt f read dello World nPython programming for Arduino nBye n gt gt gt f close As the read method grabs the entire contents of the file into memory you can use it with the optional size parameter to avoid any memory congestion while working with large files As an alternative method you can use the readlines method to read the content of an opened file line by line gt gt gt f open test txt r gt gt gt 1 f readlines gt gt gt print 1 Hello World n Python programming for Arduino n Bye n gt gt gt f close As you can see in the preceding example each string is printed as an element of a list that you can access individually You can play around with these methods to get familiar with creating and modifying files These exercises w
401. t myList a 2 b 12 0 5 hello 2 10 Similarly you can use pop to remove an element from the list A simple pop function will remove the last element of the list while an element at a specific location can be removed using pop i where i is the index number gt gt gt myList pop 10 gt gt gt myList a 2 b 12 0 5 hello 2 gt gt gt myList pop 5 hello gt gt gt myList a 2 b 12 0 5 2 Tuples Tuples are immutable data structures supported by Python different from the mutable structures of lists An immutable data structure means that you cannot add or remove elements from the tuple data structure Due to their immutable properties tuples are faster to access compared to lists and are mostly used to store a constant set of values that never change The tuple data structure is declared like list but by using parentheses or without any brackets gt gt gt tupleA gt gt gt tupleA 1 2 3 gt gt gt tupleB gt gt gt tupleB 1 a 3 1 2 3 1 a 3 Just like in a list data structure values in tuple can be accessed using index numbers gt gt gt tupleB 1 Li a I As tuples are immutable list manipulation methods such as append insert and pop don t apply for tuples Sets The set data structure in Python is implemented to support mathematical set operations The set data structure includes an unordered collection of elements wi
402. talled with it Tkinter is designed to take minimal programming efforts for developing graphical applications while also being powerful enough to provide support for the majority of GUI application features If required Tkinter can also be extended with plugins Tkinter via Tk offers an operating system s natural look and feel after the release of Tk Version 8 0 To test your current version of the Tk toolkit use the following commands on the Python prompt gt gt gt import Tkinter gt gt gt Tkinter _test You will be prompted with an image similar to that displayed in the following screenshot that contains information about your Tk version eoo tk This is Tcl Tk version 8 5 This should be a cedilla Click me QUIT If you face any problem in getting this window check your Python installation and reinstall it as you won t be able to move further ahead in this chapter without the Tkinter library and the Tk toolkit The Tkinter interface supports various widgets to develop GUIs The following table describes a few of the important widgets that we will be using in this chapter Scale Ir 4 Pe mis enables you to toggle between two values by checking the box Note A detailed description of the Tkinter functions and methods to implement the majority of functionalities provided by the Tk toolkit can be obtained from https docs python org 2 library tk html Your first Python GUI program A
403. ted operation for a critical system such as a remote home monitoring system 1 In the current configuration of the Raspberry Pi the screen of the Raspberry Pi will go to sleep after some time and the Wi Fi connection will be terminated when this happens To avoid this problem and force the screen to remain active you will need to perform the following changes Open the 1ightdm conf file using the following command sudo nano etc lightdm lightdm conf 2 In the file navigate to the SetDefaults section and edit the following line xserver command X s dpms 3 Now that your Raspberry Pi is set up it is time to copy the program file from your computer to the Raspberry Pi You can use SCP PuTTY or just a USB drive to transfer the necessary file to the Raspberry Pi If you install and configure everything as specified your program should run without any errors You can run the Python program constantly in the background using the following command nohup python controlCenter py The last thing that we want to set up on the Raspberry Pi is the TFT LCD screen The installation and configuration processes of the TFT LCD screen are described in Chapter 7 The Midterm Project a Portable DIY Thermostat Please follow the steps in the given order to set up the screen The control center module along with the Raspberry Pi and the TFT screen can now be deployed in any part of your house Stage 3 a web application using Xive
404. tem but not for resource constrained hardware platforms such as Arduino As we discussed earlier the client server paradigm implemented by the HTTP REST architecture creates a tightly coupled system In this paradigm both sides the client and the server need to be constantly active or live to respond Also the REST architecture only allows unidirectional communication from client to server where requests are always initialized by the client and the server responds to the client This request response based architecture is not suitable for constrained hardware devices because of but not limited to the following reasons e These devices should avoid active communication mode to save power e The communication should have less data overhaul to save network resources e They usually do not have enough computational resources to enable bidirectional REST communication that is implementing both client and server mechanisms on each side e The code should have a smaller footprint due to storage constraints Tip The REST based architecture can still be useful when the application specifically requires a request response architecture but most sensor based hardware applications are limited due to the preceding points Among other data delivery paradigms that solve the preceding problems the architecture based on publisher subscriber pub sub stands tall The pub sub architecture enables bidirectional communication capabilities between the node
405. tensions for Arduino Networking extensions for Arduino Arduino Ethernet library Arduino Ethernet library web server building with Arduino Exercise 1 a web server your first Arduino network program constants o about Constants control center remote home monitoring system o about Stage 2 a control center using Python and the Raspberry Pi O O O 0 o architecture The control center architecture o Python code The Python code for the control center o GUI creating with Tkinter Creating the GUI using Tkinter o Mosquitto broker communicating with Communicating with the Mosquitto broker o system status calculating Calculating the system s status and situation awareness Xively communicating with Communicating with Xively buzzer status checking Checking and updating the buzzer s status buzzer status updating Checking and updating the buzzer s status testing with monitoring station Testing the control center with the monitoring station O O 0 o setting up on Raspberry Pi Setting up the control center on the Raspberry Pi conversion functions o char Conversions byte Conversions int Conversions float Conversions about Conversions CSV file o about Using CSV files to store data o used for storing data Using CSV files to store data o Arduino data storing Storing Arduino data in a CSV file o data plotting Plotting data from a CSV file custom cloud
406. ter 7 The Midterm Project a Portable DIY Thermostat Communicating with the Mosquitto broker At the control center level we subscribe to topics that are published from the monitoring station that is MonitoringStation temperature MonitoringStation humidity and so on If you have performed any modification to the Arduino code to change the MQTT topics you need to reflect those changes in this section If the topics published by the monitoring station do not match the topics in the control center s code you will not get any updates As you can see in the Python code we are associating the on_message and on_publish methods with very important function Whenever a message arrives from the subscriber the client will call the functions associated with the on_message method However every time a message gets published from the Python code the onPublish function will get called cli mq Client ControlCenter cli on_message onMessage cli cli cli cli cli cli cli cli on_publish onPublish connect 10 0 0 18 1883 15 subscribe MonitoringStation temperature 0 subscribe MonitoringStation humidity subscribe MonitoringStation motion 0 subscribe MonitoringStation light 0 subscribe MonitoringStation buzzer 0 subscribe MonitoringStation led 0 Calculating the system s status and situation awareness The control center is assigned with the task of calculating the status of the over
407. tful actions from the monitoring station and you will only be able to use the Serial prin1n command to print various sensor measurements Therefore we will develop the control center next so that we can start addressing communication requests from the monitoring station Stage 2 a control center using Python and the Raspberry Pi In order to deliver the status of the system and other sensor observations to the user the control center needs to perform various operations that include obtaining raw sensor data from the monitoring station calculating the status of the system reporting this data to the cloud services and displaying observation using GUI While the control center includes two major hardware components the Raspberry Pi and TFT LCD screen it is also comprised of two major software components the Mosquitto broker and Python code to handle the control center logic Tip We are using a Raspberry Pi instead of a regular computer as we want the control center to be a deployable and portable unit that can be mounted on a wall You can still use your own computer to edit and test the Python code for development purposes instead of using a Raspberry Pi directly However we recommend that you switch back to the Raspberry Pi once you are ready for deployment The control center architecture The Raspberry Pi is the main computation unit of the control center and works as the brain of the entire system Since the Raspberry Pi is used
408. th lt type float gt As you can see the interpreter assigns the data type as float The interpreter can also deduce the type of complex numbers as shown in following examples You can access the real and imaginary value of a complex number using the dot operator followed by real and imag gt gt gt val 2 0 3 9 gt gt gt val real 2 0 gt gt gt val imag 3 9 Just to play more with complex numbers let s try the abs and round functions as displayed in the following examples They are built in Python functions to obtain the absolute value and the rounded number respectively gt gt gt abs val 4 382921400162225 gt gt gt round val imag 4 0 Like numbers the Python interpreter can also automatically identify the declaration of string data types In Python string values are assigned using single or double quotes around the value When the interpreter sees any value enclosed within quotes it considers it to be a string Python supports the usage of the operator to concatenate strings gt gt gt si Hello gt gt gt s2 World gt gt gt si s2 Helloworld gt gt gt st 52 Hello World A character type is a string of size one and the individual characters of a string can be accessed by using index numbers The first character of a string is indexed as 0 Play with the following scripts to understand indexing subscripting in Python gt gt gt s1 0 H gt gt
409. the Troubleshooting section in case you run into any trouble Troubleshooting Here are some of the errors that you may find and their fixes e 2C sensor returns the error string o Check the connections to the SDA and SCL pins o Confirm that you are providing enough delay between the reading cycles of the sensor Check the datasheet for the delay and message sequence e The plot window flickers instead of staying on when the button is pressed o Don t try to press it multiple times Hold and let go quickly Make sure that your button is connected properly o Adjust the delay in the Arduino sketch Stage 2 using a Raspberry Pi for the deployable thermostat We have now created a thermostat that exists as an Arduino prototype while the Python program runs from your computer This prototype is still nowhere near a deployable or mobile state due to the connected computer and the display monitor if you are using a desktop computer A real world thermostat device should have a small footprint portable size and miniature display to show limited information The popular and practical way to achieve this goal is to use a small single board computer that is capable of hosting an operating system and hence providing the essential Python programming interface For this stage of the project we will be utilizing a single board computer a Raspberry Pi with a small LCD display Note Note that this stage of the project is optional unles
410. the SD card and show you the following installation screen so that you can get started y Install OS dy Online help h y Exit i a cl ee Se See Archlinux ma gt OpenELEC 1 RISC OS E Pidora R RaspBMC O Raspblan RECOMMENDED Note The preceding screenshot is taken from raspberry_pi_F01_ 02 5a jpg by Simon Monk and is licensed under Attribution Creative Commons license https learn adafruit com assets 11384 1 Asa first time user select Raspbian RECOMMENDED as the recommended operating system and click on the Install OS button Raspbian is a Debian based OS that is optimized for the Raspberry Pi and it supports useful Linux commands that we have already learned in the previous chapters The process will take about 10 to 20 minutes to complete 2 On successful completion you will be able to see a screen similar to the one displayed in the following screenshot The screenshot displays the raspi config tool that will let you set up the initial parameters We will skip this process to complete the installation Select lt Finish gt and press Enter Raspberry Pi Software Configuration Tool raspi config Setup Options 1 Expand Filesystem Ensures that all of the SD card storage s available to the 0S 2 Change User Password Change password for the default user pi 3 Enable Boot to Desktop Choose whether to boot into a desktop environment or the command line 4 Internationalisatio
411. the appropriate changes execute the code from the terminal If you don t start getting any updates from the Arduino on the terminal you should restart Arduino to reestablish the connection with the web py server Once you start seeing periodic updates from the Arduino POST requests at the terminal open the location of the web application in your browser You will be able to see something similar to the preceding screenshot Here you can submit the manual temperature value using the form while the browser will reload with the updated relative humidity according to the temperature value entered Exercise 3 a RESTful Arduino web application The goal of this exercise is to simply combine the GET and POST methods you learned in the previous two sections in order to create a complete REST experience using Arduino and Python The architecture for this exercise can be described as follows e The Arduino client periodically uses the GET request to obtain the sensor type from the server It uses this sensor type to select a sensor for observation In our case it is either a humidity or motion sensor e The web server responds to the GET request by returning the current sensor type of the sensor selected by the user The user provides this selection through a web application e After receiving the sensor type the Arduino client utilizes POST to send sensor observation to the server e The web server receives the POST data and updates the sensor
412. the following scenarios or troubleshoot them e Twitter rate limit exceed error Twitter imposes a limit on the number of requests you can make to their public API If you are requesting the API too often this often occurs when you reduce the sleep time between consecutive queries your application will exit with an exception To avoid this set a longer sleep time in the Python program loop before requesting the API again There is a trade off between the frequency of requests and the response time of your appliances You can learn about this limitation at http dev twitter com rest public rate limiting and adjust your request interval accordingly Once you have received this error you will have to wait for some time approximately 10 to 15 minutes before making requests to the Twitter API again Read only application cannot post error This error will only occur if you forgot to change the permissions on your application to Read and Write from Read only Make sure that you have performed this change Also Twitter takes some time for the changes to take effect Extending the project with additional features The current system can be expanded to include multiple features You can start saving the time duration in which a particular appliance was on or off and then provide a detailed analysis to the user You can also use this information to calculate the energy being expended by these appliances You can utilize the current measure
413. the software that is hosted on a computer Any software from any computer host that is capable of serial communication can communicate with the microcontroller using Firmata Firmata gives complete access of Arduino directly to the software and eliminates the processes of modifying and uploading Arduino sketches To utilize the Firmata protocol a developer can upload a sketch that supports the protocol to the Arduino client as a onetime process Afterwards the developer can write custom software on the host computer and perform complex tasks This software will provide commands via a serial port to the Arduino board that is equipped with Firmata He or she can keep altering the logic on the host computer without interrupting the Arduino hardware The practice of writing custom Arduino sketches is still valid for standalone applications where the Arduino board has to perform a task locally We will explore both these options in the upcoming chapters Note You can learn more about the Firmata protocol and its latest version from the official website at http www firmata org Uploading a Firmata sketch to the Arduino board The best way to start testing the Firmata protocol is to upload a standard Firmata program to the Arduino board and use the testing software from the host In this section we are going to demonstrate a method to upload an Arduino sketch which has this standard Firmata program to the board This is going to be the default m
414. the value received using this method is the latest updated value at the serial port When you read a digital pin you can get only one of the two inputs HIGH or LOW which will translate to 1 or in Python board digital pin read The analog pins of Arduino linearly translate the input voltages between 0 and 5V to 0 and 1023 However in pyFirmata the values between 0 and 5V are linearly translated into the float values of O and 1 0 For example if the voltage at the analog pin is 1V an Arduino program will measure a value somewhere around 204 but you will receive the float value as 0 2 while using pyFirmata s read method in Python Additional functions Besides the method that has already been described the pyFirmata library also provides some utility functions for additional customization which are as follows e servo_config pin min_pulse 544 max_pulse 2400 angle 0 This method helps to set up the SERVO mode with further customization such as the minimum pulse value maximum pulse value and starting angle One can set the initial angle of the servomotor using the angle parameter e pass _time seconds This method provides a functionality similar to that found in the default Python s default method sleep that is provided by the time module However the pass_time function provides a non blocking timeout in seconds e get_firmata_version This function returns a tuple that contains the version of the Firmata protocol
415. these modifications you can see the setup function that we are publishing as a one time connection message to the Mosquitto broker to check the connection You can implement a similar function on a periodic basis if you have a problem with keeping your Mosquitto connection alive if client connect Arduino client publish Arduino connection Connected In the 1oop method we are executing the publishData function every 5 seconds It contains the code to publish sensor information The client loop method also helps us keep the Mosquitto connection alive and avoids the connection timeout from the Mosquitto broker void loop publishData delay 5000 client loop As you can see in the following code snippet the publishData function obtains the sensor values and publishes them using the appropriate topic labels You might have noticed that we are using the dtostrf function in this function to change the data format before publishing The dtostrf function is a function provided by the default Arduino library that converts a double value into an ASCII string representation We are also adding a delay of another 5 seconds between the successive publishing of sensor data to avoid any data buffering issues void publishData float humidity getHumidity 22 0 humidityC dtostrf humidity 5 2 message_buff2 client publish Arduino humidity humidityC delay 5000 int motion digitalRead
416. this project we successfully created a portable and deployable thermostat using Arduino which monitors temperature humidity and ambient light During this process we assembled the thermostat sensor unit using the necessary components and developed custom Arduino program to support them We also utilized Python programming methods including GUI development and plots using Tkinter and matplotlib libraries respectively Later in the chapter we utilized the Raspberry Pi to convert a mere project prototype into a practical application Henceforth you should be able to develop similar projects that require you to observe and visualize real time sensor information Going forward we will be expanding this project to accommodate upcoming topics such as Arduino networking cloud communication and remote monitoring In the next level of the thermostat project we will integrate these advanced features and make it a really resourceful DIY project that can be used in everyday life In the next chapter we are going to start the next stage of our journey from making simple Python Arduino projects to Internet connected and remotely accessible IoT projects Chapter 8 Introduction to Arduino Networking So far we used a hardwired serial connection to interact with Arduino a serial monitor to observe the Arduino serial data and a Python serial library pySerial to transfer data between the Arduino and Python applications During this entire exchange the ra
417. thon has grown into one of the most widely used general purpose high level programming languages and is supported by one of the largest open source developer communities Python is an open source programming language that includes a lot of supporting libraries These libraries are the best feature of Python making it one of the most extensible platforms Python is a dynamic programming language and it uses an interpreter to execute code at runtime rather than using a compiler to compile and create executable byte codes The philosophy behind the development of Python was to create flexible readable and clear code to easily express concepts The emphasis on using whitespace indentation in a unique way differentiates Python from other popular high level languages Python supports functional imperative and object oriented programming with automatic memory management Why we use Python Python is considered to be one of the easiest languages to learn for first time programmers Compared to other popular object oriented languages such as C and Java Python has the following major benefits for programmers e It is easy to read and understand e It enables rapid prototyping and reduces development time e It has a humongous amount of free library packages Python has a huge open source community that drives forth the effort for continuous improvement of Python as a programming language The Python community is also responsible for the development
418. thout duplicates With its mathematical use cases this data structure is mostly used to find duplicates in lists as conversion of a list to a set using the set function removes duplicates from the list gt gt gt listA 1 2 3 1 5 2 gt gt gt setA set listA gt gt gt setA set 1 2 3 5 Dictionaries The dict data structure is used to store key value pairs indexed by keys which are also known in other languages as associative arrays hashes or hashmaps Unlike other data structures dict values can be extracted using associated keys gt gt gt boards uno 328 mega 2560 lily 128 gt gt gt boards lily 128 gt gt gt boards keys lily mega uno Note You can learn more about Python data structures and associated methods at https docs python org 2 tutorial datastructures html Controlling the flow of your program Just like any other language Python supports controlling the program flow using compound statements In this section we will briefly introduce these statements to you You can get detailed information about them from the official Python documentation at https docs python org 2 reference compound_stmts html The if statement The if statement is the most basic and standard statement used to set up conditional flow To better understand the if statement execute the following code in the Python interpreter with different values of the age variable
419. ties window which is located at the bottom of the window This will open an interface similar to the one shown in the following screenshot In Environment Variables you need to update the PATH system variable to add Python to the default operating system s path Click on the PATH option as displayed in the following screenshot which will pop up an Edit System Variable window Add C Python27 or the full path of your custom Python installation directory at the end of your existing PATH variable It is required to put a semicolon before the Python installation path If you already see Python s location in the Path variable your system is set up for Python and you don t need to perform any changes Variable name Variable value 32WindowsPowerShellw1 01 C Python21 System variables Variable Value NUMBER_OF P 4 05 Windows_NT Path C windows system32 C Windows C PATHEXT COM EXE BAT CMD VBS VBE JS PT The main benefit of adding Python to the environment variables is to enable access to the Python interpreter from the command prompt In case you don t know the Windows command prompt can be accessed by navigating to Start Programs Accessories Command Prompt Mac OS X Mac OS X ships with a preinstalled copy of Python but due to the long release cycle of the operating system the frequency of updates for the default Python application is slow The latest version of Mac OS X which is 10
420. tifying out of range temperature and humidity values You can implement a few extended features to make your system more versatile and useful e Implement different logic for day and night scenarios which can help you to avoid unwarranted false alarms at night e Implement an intruder detection algorithm using the motion sensor for when you are not at home e Utilize a combination of ambient light sensor values with motion sensors to identify energy wastage For example a scenario in which more light is recorded during the night when the motions are significantly low explains that you may have forgotten to turn off the lights during the night Creating an enclosure for hardware components Just like software based features the hardware components also require a major revamp if you develop a commercial grade product Nowadays 3D printers have become viable and it is really easy to design and print plastic 3D components You can also use professional 3D printing services such as Shapeways http www shapeways com Sculpteo http www sculpteo com or makexyz http www makexyz com for your enclosures You can even use a laser cutter or other means of model making to create the hardware enclosures These are a few hardware improvements that you can implement e The sensor and actuators that are assembled on a prototype board can be organized on a PCB and permanently fixed for stable and robust operation e A hardware enclosure for the mo
421. ting the Iterator function over it port COM3 board Arduino port sleep 5 it util Iterator board it start Once the board has been initialized we need to assign a role to the analog pin 0 as it is going to be used as an input pin We are using the get_pin method to assign a role to the analog pin 0 a0 board get_pin a 0 i Now as part of the main program we need to continuously monitor the output of the potentiometer at the pin a0 that we just defined We are using the while statement to create an indefinite loop for the script that will read and print the analog input The problem with this indefinite while loop is that the program will not close properly when it is interrupted and it will not release the board by executing the board exit method To avoid this we will use another control statement from the Python programming paradigm called try except try while True p a0 read print p except KeyboardInterrupt board exit os _exit Using this statement the program will keep running the while loop until the keyboard interruption occurs which is Ctrl C and the program will execute the script under the except statement This includes releasing the board using board exit and existing the program using the os _exit method In summary the program will keep printing the output of the potentiometer until someone presses Ctrl C to interrupt the program Note The try except statement p
422. tion of the first project you successfully started Python Arduino interfacing We also interfaced multiple hardware components that is motion sensor and LEDs with Arduino via digital pins During the project you learned more about the Firmata protocol while utilizing simple Python methods that helped you to establish a connection between your Arduino board and the Python program When you are working on complex projects you need more than basic methods to implement the different features that are required by the projects and their associated electronics components This chapter is designed to give you a comprehensive experience of interfacing so that you can start working on hard problems from the next chapter onwards We have described various interfacing protocols at the Python Arduino and Arduino to components levels This chapter also includes practical examples for these protocols with appropriate code and circuit diagrams In this chapter we are going to cover the following main topics e Introduction to Prototyping e Detailed description of various pyFirmata methods to port Arduino functionalities into Python e Python Arduino interfacing examples using Firmata for basic electronic components such as the potentiometer the buzzer the DC motor and the servomotor e Introduction to the inter integrated circuit 12C protocol and prototyping examples for the I2C components such as the temperature sensor TMP102 and the light sensor BH1750
423. tions with tightly coupled physical computation and interfacing layers In the research domain these types of applications are also known as cyber physical systems One of the widely used and popular terms for the domain of cyber physical system is the loT Although the cyber physical domain is thoroughly defined compared to the IoT the IoT has recently gained more popularity due to the large number of subdomains industrial Internet wearable devices connected devices smart grid and so on that are covered under this umbrella term In simple terms an application can qualify as an IoT application if it consists of hardware devices that deal with the physical world and have sufficient computational capabilities with Internet connectivity Let s try to understand the architecture of the IoT from the material that we have already covered On the physical side the following figure shows the hardware components that we utilized to deal with the physical environment The sensors and actuators that interface with the actual physical world can be connected to Arduino using multiple low level protocols These components can be connected using GPIO pins and using the I2C or SPI protocols The data acquired from these components gets processed on the Arduino board using the code that is uploaded by the user Although the Arduino code can be made self reliant to execute tasks without any external inputs these inputs from users or other applications are re
424. tle bar will appear as the output of the program Clicking on the Start button will turn on the LED on the Arduino board for the specified time delay Meanwhile when the LED is on you will not be able to click on the Start button again Now in this particular program we haven t provided sufficient code to safely disengage the Arduino board and it will be covered in upcoming exercises 600 Blink LED using button Start The Entry widget providing manual user inputs In the previous exercise you used a button to blink the LED on the Arduino board for a fixed amount of time Let s say that you want to change this fixed time delay and specify a value according to your application s requirement To perform this operation you will need a widget that accepts custom values that can then be converted into the delay Just like any other GUI framework Tkinter provides the interface for a similar widget called Entry and we will utilize this in the next exercise Keep the same Arduino and LED configurations that you used for the previous exercise and open the exampleEntry py file In the beginning of the code you will find the same configuration for the Arduino board and the LED pin that we used in the previous exercise Moving on to the next stage you will be able to see the following code snippet that defines the root widget In this code snippet we have changed the title of the main window to reflect the premise of the exercise The us
425. to another position to dynamically vary the value for the brightness The Grid geometry manager In the previous exercise we added three different widgets to the root window using the Pack geometry manager and the pack method We didn t actively organize these widgets but the Pack manager automatically arranged them in the vertical position While designing a meaningful interface you need to arrange these widgets in the appropriate order If you look at the previous output window it is really difficult to identify the function of each widget or their association with others In order to design an intuitive GUI you also need to describe these widgets using the appropriate labels As a solution Tkinter provides an alternative way to organize your widgets that is called Grid geometry manager The Grid geometry manager provides a two dimensional 2D table interface to arrange widgets Every cell that results from the row and column of the 2D table can be used as a place for the widgets You will learn the various options that are provided by the grid class to organize widgets in the next programming exercise Open the exampleGridManager py file from the code folder of this chapter In terms of functionalities this file contains the same program that we built in the previous exercise However we have added more Label widgets and organized them using the Grid geometry manager to simplify the GUI and make it more useful As you can obs
426. to develop cloud based IoT applications Chapter 10 The Final Project a Remote Home Monitoring System teaches a design methodology for the hardware product followed by a comprehensive project that interfaces the cloud platform with Arduino and Python Chapter 11 Tweet a PowerStrip contains another IoT project that is based on everything that we learned in the book The project explores a unique approach to integrate a social network Twitter with the Python Arduino application What you need for this book To begin with you will just need a computer with one of the supported operating systems Windows Mac OS X or Linux The book requires various additional hardware components and software tools to implement programming exercises and projects A list of required hardware components and locations to obtain these components are included in each chapter In terms of software the book itself provides step by step guidelines to install and configure all the necessary software packages and dependent libraries that are utilized throughout the book Note that the exercises and projects included in the book are designed for Python 2 7 and they have not been tested against Python 3 Who this book is for If you are a student a hobbyist a developer or a designer with little or no programming and hardware prototyping experience and you want to develop IoT applications then this book is for you If you are a software developer and inter
427. to receive and send data which adds additional delay and reduces the speed of execution e Unwanted space The Firmata protocol contains a large amount of additional code to support various other Arduino functions In a well defined project you don t really need the complete set of functions e Limited support Although a version of Firmata includes I2C support it is quite difficult to implement complex I2C functions without adding delay In summary you can always use Firmata based approaches to quickly prototype your projects but when you are working on production level or advanced projects you can use alternative methods In these scenarios you can use custom Arduino code that is supported by Python s serial library pySerial to enable communication for very specific functionalities In this section we are going to cover a few helpful pySerial methods that you can use if you have to utilize the library directly Connecting with the serial port Once you have connected your Arduino to a USB port of your computer you can open the port in your Python code using the Serial class as displayed in the following code example import serial port serial Serial COM5 9600 timeout 1 In addition to port name and baud rate you can also specify a number of serial port parameters such as timeout bytesize parity stopbits and so on using Serial Itis necessary to initialize the serial port before executing any other command from the
428. to send sensor values automatically to the Xively platform This will enable the storage and visualization of Arduino data on Xively Alternative IoT platforms In this section we have provided important links for the ThingSpeak and Carriots platforms As we are not covering these platforms in detail these links will help you to find similar examples to interface Arduino and Python with ThingSpeak and Carriots ThingSpeak The tutorials in the following links will help you to get familiar with the ThingSpeak platform if you chose to use it instead of Xively e The official website https thingspeak com e Using Arduino and Ethernet to update a ThingSpeak channel http community thingspeak com tutorials arduino using an arduino ethernet shield to update a thingspeak channel e Arduino examples for ThingSpeak https github com iobridge ThingSpeak Arduino Examples means with ThingSpeak using Python a memory cpu monitor e Using Arduino and Python to talk to a ThingSpeak channel http vimeo com 19064691 e Series of ThingSpeak tutorials http community thingspeak com tutorials ThingSpeak is an open source platform and you can create your own customized version of ThingSpeak using the files provided You can obtain these files and the associated guideline from https github com iobridge ThingSpeak Carriots Carriots also provides a free basic account for developers If you want to use Carriots as an alternative
429. to use the Tkinter variable class for the Checkbutton widget instead of the default Python variables After defining the Checkbutton widget for the red LED we have repeated this process for the green LED as shown in the following code snippet greenVar Tkinter IntVar greenCheckBox Tkinter Checkbutton top text Green LED variable greenVar greenCheckBox grid column 2 row 1 This program also contains the Start and Exit buttons and their respective association with the onStartButtonPress and top quit functions similar to how we used them in the previous exercise When called the onStartButtonPress function will obtain the values of the Intvar variables redVar and greenvar using the get method In this case the variable value of the Checkbutton widget will be 1 when it is checked and 0 otherwise This will enable the program to send the value 1 or o to the Arduino pin using the write method by checking or unchecking the widget and ultimately turn the LED on or off def onStartButtonPress redPin write redVar get greenPin write greenVar get As you can see the code also implements an additional Stop button to turn off the LEDs that were turned on using the Start button stopButton Tkinter Button top text Stop command onStopButtonPress stopButton grid column 2 row 2 The onStopButtonPrerss function associated with this button turns off both the LEDs by using write 0 on both the pins def
430. tools and pip run the following command on the terminal sudo pip install matplotlib Executing this command will lead to one of the following three possibilities e Successful installation of the latest matplotlib version e Notification that the requirements are already satisfied but the installed version is older than the current version which is 1 3 at the moment e Error while installing the matplotlib package If you encounter the first possibility then you can advance to the next section otherwise follow the troubleshooting instructions You can check your matplotlib version using the following commands on the Python interactive prompt gt gt gt import matplotlib gt gt gt matplotlib version _ Upgrading matplotlib If you encounter the second possibility which states that the existing version of the matplotlib is older than the current version use the following command to upgrade the matplotlib package sudo pip install upgrade matplotlib Go through the next section in case you end up with errors during this upgrade Troubleshooting installation errors If you encounter any errors during the matplotlib installation via pip it is most likely that you are missing some dependency packages Follow these steps one by one to troubleshoot the errors Tip After every step use one of the following commands to check whether the error is resolved sudo pip install matplotlib sudo pip install upgrade matplot
431. tools is not that straightforward for Windows as compared to Linux It requires the user to download the ez_setup py file from the Windows section at https pypi python org pypi setuptools Once this is downloaded press Shift and right click in the folder where you downloaded the ez_setup py file Select Open command window here and execute the following command gt python ez_setup py This will install Setuptools in the Scripts folder of your default Python installation folder Using the same method that we used when we added Python to Environment Variables now include Setuptools by adding C Python27 Scripts to PATH followed by the semicolon This will enable the installation of various Python packages using easy_install to your Python packages folder called Libs Once you have added the package manager to the environment variables you need to close and reopen the command prompt for these changes to take effect Mac OS X Setuptools can be installed in Mac OS X using any of the following methods It is advisable for beginners to use the first method as the second method requires the external package manager Homebrew If you have never worked with Homebrew before you will need to follow these steps to install Setuptools on your Mac 1 Download ez_setup py from the Unix Mac section at https pypi python org pypi setuptools 2 Open the terminal and navigate to the directory where you downloaded this file For most
432. troubleshooting Troubleshooting e prototyping with I2C protocol e PyPI o o o Oo o about Prototyping with the 12C protocol Arduino examples Arduino examples for 12C interfacing TMP102 temperature sensor using Arduino Arduino coding for the TMP102 temperature sensor BH1750 light sensor using Arduino Arduino coding for the BH1750 light sensor PyMata library using PyMata for quick I2C prototyping TMP102 temperature sensor using PyMata library Interfacing TMP102 using PyMata BH1750 light sensor using PyMata library Interfacing BH1750 using PyMata pySerial commands using Useful pySerial commands prototyping templates using Firmata o O O O O o about Prototyping templates using Firmata potentiometer Potentiometer continuous observation from an analog input buzzer using Buzzer generating sound alarm pattern DC motor using DC motor controlling motor speed using PWM LED LED controlling LED brightness using PWM servomotors using Servomotor moving the motor to a certain angle PubSubClient library o o o using MQTT on Arduino using the PubSubClient library installing Installing the PubSubClient library URL Installing the PubSubClient library pulse width modulation PWM o about The Arduino Uno board push button switch o using The list of required components pyFirmata methods o O O 0 0 O O 0 0 Oo Oo o
433. u can obtain further information regarding the actual tool and community from its website at http www mosquitto org Setting up Mosquitto The installation and configuration of Mosquitto are very straightforward processes At the time of writing this book the latest version of Mosquitto is 1 3 4 You can also obtain the latest updates and installation information regarding Mosquitto at http www mosquitto org download On Windows you can simply download the latest version of the installation files for Windows which is made for Win32 or Win64 systems Download and run the executable file to install the Mosquitto broker To run Mosquitto from the command prompt you will have to add the Mosquitto directory to the PATH variables in the environment variables of the system properties In Chapter 1 Getting Started with Python and Arduino we comprehensively described the process of adding a PATH variable to install Python Using the same method add the path of the Mosquitto installation directory at the end of the PATH value If you are using a 64 bit operating system you should use C Program Files x86 mosquitto For a 32 bit operating system you should use C Program Files mosquitto as the path Once you are done with adding this value at the end of the PATH value close any existing command prompt windows and open a new Command Prompt window You can validate the installation by typing the following command in the newly opened window If e
434. u can perform various actions such as reading a pin or sending a signal to the pin using that variable To assign a role to a pin the get_pin method is used In the following line of code d represents the digital pin 7 is the pin number and i represents that the type of pin is an input pin pirPin board get_pin d 7 i Once a pin and its role are assigned to a variable that variable can be used to read or write values on the pin Value pirPin read One can directly write data to a specific pin as described in following code board digital pin write 1 Here the write 1 method sends a HIGH signal to the pin We will be learning additional pyFirmata methods in the upcoming chapters Working with Python functions A Python function begins with the def keyword followed by the function name and the input parameters or arguments The function definition ends with a colon and it is indented afterwards The return statement terminates the function It also passes the expression to the place where the function is called If the return statement is kept without an expression it is considered to pass the return value None def function_name parameters action_1 action_2 return expression The preceding framework can be used to create custom functions to perform recurring tasks In our project we have the blinkLED pin message function to perform the blinking LED action This function sends 1 HIGH and 0 Low value to the
435. ue To understand the program properly let s first get familiar with the following new Tkinter classes and methods e Booleanvar Just like the Intvar variable class that we used to track the integer values BooleanVar is a Tkinter variable class that tracks changes in Boolean flag Tkinter BooleanVar top flag set True In the preceding code snippet we have created a variable object flag using the BooleanVar class and set the value of the object as True Being a Boolean object flag can only have two values True or False Tkinter also provides classes for string and double type with the StringVar and DoubleVar classes respectively Due to this when the Start button is clicked the system starts updating the analog read value The Exit button sets the flag variable to false breaks the while loop and stops the monitoring process e update_idletasks While using the Tkinter library in Python you can link a Python code to any changes that happen in a Tk widget This linked Python code is called a callback The update_idletasks method calls all idle tasks without processing any callbacks This method also redraws the geometry widgets if required AnalogReadLabel update_idletasks In our exercise this method can be used to continuously update the label with the latest potentiometer value e update This top level method processes all the pending events and callbacks and also redraws any widget if it is necessar
436. uino Ethernet byte mac 0x90 OxA2 OxDA OxOD Ox3F 0x62 IPAddress ip 10 0 0 75 Tip In the IP network the visible range of IP addresses for your network is a function of another address called subnetwork or subnet The subnet of your LAN IP network can help you select the appropriate IP address for the Ethernet Shield in the range of the IP address of your computer You can learn about the basics of the subnet at http en wikipedia org wiki Subnetwork Before venturing further into the code compile the code with these modifications and upload it to your Arduino Once the uploading process is completed successfully open a web browser and enter the IP address that you had specified in the Arduino sketch If everything goes fine you should see text displaying the values of the analog pins To better understand what happened here let s go back to the code As you can see at the beginning of the code we initialize the Ethernet server library on port 80 using the EthernetServer method from the Ethernet library EthernetServer server 80 During the execution of setup the program initializes the Ethernet connection through the Ethernet Shield using the Ethernet being method with the mac and ip variables that you defined earlier The server begin method will start the server from here Both of these steps are mandatory to start a server if you are using the Ethernet library for server code Ethernet begin mac ip
437. uino compatible relays from manufacturers such as Keyes or SainSmart These relays are available in single two or four channel configurations On the high power side the relays support up to 250V 10A AC power or 30V 10A DC power The relays are controlled using 5V DC on the low power side which is provided using the digital I O pins of the Arduino board PowerSwitch Tail Working with AC power can be hazardous if you haven t dealt with it previously or if you are not familiar with the necessary precautions and measurements If you are not comfortable with working with open relays or connecting AC power to them there is another device that you can use to replace the relay the PowerSwitch Tail a safely enclosed box that contains optically isolated solid state relays and provides a convenient way to interface your AC appliance with the Arduino board The following is an image of the PowerSwitch Tail which can be obtained from its official website http www powerswitchtail com PowerSwitch Tail ul Actuated AC Pawar Suites ww Power witch Tail com in 3 Ground Note If you are dealing with a 220V 240V power supply the PowerSwitch Tail website also provides an assembly kit for 200V to 240V power supply at http www powerswitchtail com Pages PowerSwitchTail240vackit aspx It is really easy to assemble the kit from the guidelines provided at http www powerswitchtail com Documents PSSRTK 20lnstructions pdf For t
438. ulated def POST self f self submit_form f validates temperature f Temperature value line port readline if line data float line humidity relativeHumidity line float temperature return render base f humidity else return render base f Not valid data Now it is time to run the web py based web server In the Python program make the necessary changes to accommodate the serial port name and any other appropriate values If everything is configured correctly you will be able to execute the program from the terminal without any errors You can access the web server which is running on port 8080 from a web browser on the same computer that is http localhost 8080 Now the goal of the exercise is to demonstrate the remote accessibility of the web server from your home network and you can do this by opening the website from another computer in your network that is http lt ip address gt 8080 where lt ip address gt refers to the IP address of the computer that is running the web py service m As eoo 10 0 0 20 8080 C 10 0 0 20 8080 O Arduino serial interfacing with Web py Use following form to manually enter temperature value to obtain relative humidity Default temperature is 25 C Temperature 40 submit Relative Humidity is 22 8237839917 The preceding screenshot shows how the web application will look when opened in a web browser When you load the websit
439. upgrade Python to the latest revision of v2 7 x using the following command sudo apt get update amp amp sudo apt get only upgrade install python If you are running an older version of Ubuntu such as 10 04 or older you should have 2 6 as the default version In this case you will need to run the following set of commands to install version 2 7 sudo add apt repository ppa fkrull deadsnakes sudo apt get update sudo apt get install python2 7 The first command will add an external Ubuntu repository which will allow you to install any version of Python The next command will update and index the list of available packages The last command will install the latest version of Python 2 7 Fedora and Red Hat Fedora and Red Hat Linux also ships with Python as an in built package If you want to upgrade the version of Python to the latest one run the following command at the terminal sudo yum upgrade python Tip Downloading the example code You can download the example code files from your account at http www packtpub com for all the Packt Publishing books you have purchased If you purchased this book elsewhere you can visit http www packtpub com support and register to have the files e mailed directly to you Windows Installation and configuration of Python on Windows is not as straightforward as it is for Linux First of all you 1l need to download a copy of Python from http www python org getit You
440. usbmodemfa1311 is selected for Mac OS X you can use your operating system s specific variable name in the following code snippet You can obtain more information about choosing this variable name from the Setting up the Arduino board section at the beginning of this chapter from pyfirmata import Arduino INPUT PWM from time import sleep import random port dev cu usbmodemfa1311 board Arduino port sleep 5 In this example we are utilizing the direct method of pin mode assignment As you can see in the following code snippet the digital pin 11 is being assigned to the PwM mode pin 11 board digital pin mode PWM Once the pin mode is assigned the program will run a loop using the for statement while randomly generating an integer number between 0 and 100 and then send the appropriate PWM value to the pin according to the generated number With the execution of this you will be able to see the LED randomly changing its brightness for approximately 10 seconds for i in range 0 99 r random randint 1 100 board digital pin write r 100 00 sleep 0 1 Once you are done with the loop you need to safely disengage the Arduino board after turning off the LED one last time It is a good practice to turn off the LED or any connected sensor at the end of the program before exiting the board to prevent any sensor from running accidentally board digital pin write 0 board exit Note If you want to homogenousl
441. using analog pins 5 and 6 of the Arduino board to interface SDA and SCL respectively The humidity HIH 4030 and ambient light sensors also provide analog output and are connected to the analog pins of the Arduino board Meanwhile the buzzer the button switch and the PIR motion sensor are connected through the digital I O pins The super flux RGB LED is acommon anode LED this means that it is always powered using the common anode pins and the R G and B pins are controlled by using the PWM pins Make sure that you properly connect all the components to the pins that are specified in the following diagram Buzzer i RGB LED PIR motion sensor Common Anode effete see os t r s DA TMP102 o vr ore Light sensor feet 2 2 o k onx o 2 2o o o e 0 ooxo o s C _ CS lt m a PE e FINIT lt lt lt s eee o ss t fritzing Note You can learn more about the interfacing of RGB LED with Arduino from the tutorial at https learn adafruit com all about leds If you are using an Arduino board other than Arduino Uno you will have to adjust the appropriate pin numbers in the Arduino code In addition make sure that this Arduino board is compatible with the Ethernet Shield In terms of circuit connections you can use a breadboard as s
442. uter Your computer running the web py server which is also a part of your home network will serve the client requests In the first step we are going to code Arduino to periodically send the humidity sensor value to the serial interface For the Arduino code open the WebPySerialExample_Arduino ino sketch from the Exercise 2 folder of your code directory As you can see in the following code snippet of the Arduino sketch we are sending raw values from the analog port to the serial interface Now compile and upload the sketch to your Arduino board Open the Serial Monitor window from the Arduino IDE to confirm that you are receiving the raw humidity observations Once you have confirmed it close the Serial Monitor window You won t be able to run the Python code if the Serial Monitor window is using the port void loop int analogChannel O int HIH4030_Value analogRead analogChannel Serial println HIH4030_Value delay 200 Once the Arduino code is running properly it is time to execute the Python program which contains the web py server The Python program for this exercise is located in the WebPySerialExample Python directory Open the webPySerialExample py file in your code editor The Python program is organized in two sections capturing sensor data from the serial interface using the pySerial library and using the web py server based server to respond to the requests from the clients In the first stage
443. utilizes the default Arduino Ethernet library and implements the MQTT client as a subclass of the Ethernet client To get started with the PubSubClient library you ll first need to import the library to your Arduino IDE Download the latest version of the PubSubClient Arduino library from https github com knolleary pubsubclient Once you have the file downloaded import it to your Arduino IDE We will be using one of the examples installed with the PubSubClient library to get started The goal of the exercise is to utilize a basic example to create an Arduino MQTT client while performing minor modifications to accommodate the local network parameters We will then use the Mosquitto commands you learned in the previous section to test the Arduino MQTT client Meanwhile ensure that your Mosquitto broker is running in the background Developing the Arduino MQTT client Let s start with opening the mqtt_basic example by navigating to File Examples PubSubClient in our Arduino IDE menu In the opened program change the MAC and IP address values for Arduino by updating the mac and ip variables respectively In the previous section you successfully installed and tested the Mosquitto broker Use the IP address of the computer running Mosquitto to update the server variable byte mac 0x90 OxA2 OXDA OxOD Ox3F 0x62 byte server 10 O 0 20 byte ip 10 0 0 75 As you can see in the code we are initializ
444. verything is installed and configured correctly the following command should execute without any errors C gt mosquitto For Mac OS X the best way to install Mosquitto is to use the Homebrew tool We already went through the process of installing and configuring Homebrew in Chapter 1 Getting Started with Python and Arduino Install the Mosquitto broker by simply executing the following script on the terminal This script will install Mosquitto with the Mosquitto utilities and also configure them to run from the terminal as commands brew install mosquitto On Ubuntu the default repository already has the installation package for Mosquitto Depending on the version of Ubuntu you are using this Mosquitto version could be older than the current version In that case you must add this repository first sudo apt add repository ppa mosquitto dev mosquitto ppa sudo apt get update Now you can install the Mosquitto packages by simply running the following command sudo apt get install mosquitto mosquitto clients Getting familiar with Mosquitto Due to the multiple installation methods involved for different operating systems the initialization of Mosquitto may be different for your instance In some cases Mosquitto might already be running on your computer For a Unix based operating system you can check whether Mosquitto is running or not with this command ps aux grep mosquitto Unless you find a running instance of the
445. ware components What do you need to begin using the Raspberry Pi URL What do you need to begin using the Raspberry Pi Preparing an SD card SD card preparing Preparing an SD card setup process The Raspberry Pi setup process e read method o using The read method e real time Arduino data o plotting Plotting real time Arduino data e remote home monitoring system o Oo O O O O O O 0 0 0 O O O 0 0 0 project overview Project overview project goals The project goals project requirements The project requirements system architecture designing Designing system architecture UX flow defining Defining UX flow hardware components The list of required components development stages defining Defining the project development stages monitoring station Arduino used Stage 1 a monitoring station using Arduino testing Testing Testing and troubleshooting control center using Stage 2 a control center using Python and the Raspberry Pi web application Stage 3 a web application using Xively Python and Amazon cloud service troubleshooting Testing and troubleshooting extending Extending your remote home monitoring system multiple monitoring stations utilizing Utilizing multiple monitoring stations sensory capabilities extending Extending sensory capabilities UX improving Improving UX cloud based features expanding Expanding cloud based features improved i
446. with pyFirmata and associate this relationship to another variable board Arduino port Similarly for Arduino Mega use this board ArduinoMega port 4 The synchronization between the Arduino board and pyFirmata requires some time Adding sleep time between the preceding assignment and the next set of instructions can help to avoid any issues that are related to serial port buffering The easiest way to add sleep time is to use the inbuilt Python method sleep time from time import sleep sleep 1 The sleep method takes seconds as the parameter and a floating point number can be used to provide the specific sleep time For example for 200 milliseconds it will be sleep 0 2 At this point you have successfully synchronized your Arduino Uno or Arduino Mega board to the computer using pyFirmata What if you want to use a different variant other than Arduino Uno or ArduinoMega of the Arduino board e Any board layout in pyFirmata is defined as a dictionary object The following is a sample of the dictionary object for the Arduino board arduino digital tuple x for x in range 14 analog tuple x for x in range 6 pwm 3 5 6 9 10 11 use_ports True disabled 0 1 Rx Tx Crystal e For your variant of the Arduino board you have to first create a custom dictionary object To create this object you need to know the hardware layout of your board For example an Arduino Nano board ha
447. wn as physical systems On the other front advancements in the semiconductor industry also enabled the development of highly efficient computation units empowering personal computer and networking industries This movement led to the worldwide network of connected computers called CyberWorld or the Internet Every day petabytes of data get generated and transferred across the Internet The domain of IoT stands at the crossroads of these progresses in physical and cyber systems where ancient hardwired sensor based systems are ready to get upgraded to more powerful and efficient systems that are also highly connected through the Internet Due to the large number of sensors involved these systems generate and send an avalanche of data The data generated by these sensors has already eclipsed the data generated by humans The IoT has started to become a significant domain in recent years after a large number of consumer IoT products have started entering the market These products include applications in home automation health care activity tracking smart energy and so on One of the major reasons behind the rapid growth of the IoT domain is the introduction of these visible solutions In a large number of cases this was made possible due to fast and inexpensive prototyping that was enabled by Arduino and other open source hardware platforms Up to this point in the book we have learned various methods of interfacing sensors and then develop
448. y top update We are using this method with the root window so that it can perform the callback for the Start button Now let s go back to the opened Python program As you can see besides assigning an analog pin through the get_pin method and initializing the Iterator class over the Arduino board the code contains similar programming patterns that we used in the exercises for the other Tkinter widgets In this code we are performing the read operation for the analog pin inside the onStartButtonPress function This function checks the status of the flag variable while performing the read operation on the pin and subsequently updates the value of the analogReadLabel widget if the value of the flag variable is True If the value of the flag variable is found to be False the function will exit after disengaging the Arduino board and closing the root window Due to the use of the while statement this process will continuously check the flag value until it is broken by the onExitButtonPress function by changing the flag value to False def onStartButtonPress while True if flag get analogReadLabel config text str a0 read analogReadLabel update_idletasks top update else break board exit top destroy The onExitButtonPress function is called from the Exit button and it simply resets the flag variable to False using the set method def onExitButtonPress flag set False Remaking your first Python A
449. y This also means that the web application does not populate and refresh the latest information automatically and waits for POST to execute the appropriate functions def fetchTempXively try datastreamTemp feed datastreams get Temperature except HTTPError as e print HTTPError 0 1 format e errno e strerror print Requested channel doesn t exist return datastreamTemp current_value 4 The web application also provides access to control the buzzer from the user interface The following code snippet adds the Buzzer Off button with other Form components When the form is submitted after this button is pressed the web application executes the setBuzzer function inputData web input if inputData btn buzzeroff setBuzzer OFF 5 The setBuzzer function access the Xively channel Buzzer and sends the off value if the Buzzer Off button is pressed The current web application doesn t include the Buzzer On button but you can easily implement this functionality by reusing the code that we developed for the Buzzer Off button This function provides the reference code for other control points which you can reuse with minor modifications def setBuzzer statusTemp try datastream feed datastreams get Buzzer except HTTPError as e print HTTPError 0 1 format e errno e strerror datastream feed datastreams create Buzzer tags buzzer print Creating new Channel Buzzer datastream curre
450. y glow the LED instead of randomly changing its brightness replace the code in the for loop with the following code snippet Here we are changing the PWM input to the incrementing variable i instead of the random variable r for i in range 0 99 board digital pin write i 100 00 sleep 0 1 Servomotor moving the motor to a certain angle Servomotors are widely used electronic components in applications such as pan tilt camera control robotic arms mobile robot movements and so on where precise movement of the motor shaft is required This precise control of the motor shaft is possible because of the position sensing decoder which is an integral part of the servomotor assembly A standard servomotor allows the angle of the shaft to be set between 0 and 180 degrees The pyFirmata library provides the SERVO mode that can be implemented on every digital pin This prototyping exercise provides a template and guidelines to interface a servomotor with Python Connections Typically a servomotor has wires that are color coded red black and yellow respectively to connect with the power ground and signal of the Arduino board Connect the power and the ground of the servomotor to 5V and the ground of the Arduino board As displayed in the following diagram connect the yellow signal wire to the digital pin 13 nr o oe so CS ZAR RAT is ha Be en eae i o o o 8866 C6888 ema as gt a lt 2 lt
451. y letting you simply connect the sensors and actuators with a computer Basically you can write code to monitor and control various electronic components in your daily life by using Arduino s input output pins and microcontroller Examples of these components include motors thermostats lights switches and many more History In 2005 Massimo Banzi the Italian cofounder of Arduino developed the technology for his students at Interaction Design Institute Ivrea IDII Since then Arduino has developed into one of the largest open source hardware platforms All software components and schematics of the Arduino design are open source and you can buy the hardware at a very low cost approximately 30 dollars or you can even make it yourself Why Arduino The major goal of the Arduino community is to continuously improve the Arduino platform with the following objectives in mind The Arduino platform should be an affordable platform It should be easy to use and easy to code It should be an open source and extensible software platform It should be an open source and extensible hardware platform It should have community supported DIY projects These simple but powerful objectives have made Arduino a popular and widely used prototyping platform Arduino uses Atmel s ATmega series of microcontrollers that are based on the popular hardware architecture of AVR The huge support that is available for AVR architecture also makes Arduino a ha
452. y used file formats other than text As the name states values are separated and stored using commas or other delimiters such as a space or tab Python has a built in module to deal with CSV files To begin with use the following code snippet to create a Python file and run your first CSV program import csv data 1 2 3 a b c Python Arduino Programming with open example csv w as f w csv writer f for row in data w writerow row You can also open the csvwriter py file from this chapter s code folder which contains the same code After executing the code you will be able to find a file named example csv in the same location as this file which will contain the data separated with commas As you can see in the code the CSV module offers the writer function on the opened file that initializes a writer object The writer object takes a sequence or array of data integer float string and so on as input and joins the values of this array using the delimiter character w csv writer f In the preceding example since we are not using a delimiter option the program will take the default character comma as the delimiter If you want to use space as the delimiter character you can use the following writer option w csv writer f delimiter To write each element of a list to a new line of this writer object we use the writerow method Similarly Python CSV module also provid
453. you extract the content of the ZIP folder to the root location of the SD card En e I Follow these steps to prepare the SD card from Ubuntu Linux 1 To format the SD card on Ubuntu you can use a formatting tool called gparted Install gparted using the following command on the terminal sudo apt get install gparted 2 Insert your SD card and run gparted In the gparted window select the entire SD card and format it using FAT32 4 Once the format process is complete extract the downloaded NooBs ZIP file to the SD card Make sure that you extract the content of the ZIP folder to the root location of the SD card UI Tip If you have any trouble following these steps you can refer to the official documentation for preparing the SD card for a Raspberry Pi at http www raspberrypi org documentation installation installing images The Raspberry Pi setup process Once you have prepared your SD card with NOOBS insert it into the SD card slot of the Raspberry Pi Connect your monitor mouse and keyboard before connecting the micro USB cable for the power adapter Once you connect the power adapter the Raspberry Pi will turn on automatically and you will be able to see the installation process on the monitor If you are not able to see any progress on the monitor after connecting the power adapter refer to the troubleshooting section that is available later in this chapter Once the Raspberry Pi boots up it will repartition
454. ystem is to design the project flow using logic We recommend that you have your project sketched as a flowchart to better understand the layout of the components and the flow of the code The following diagram shows the flow of the project where you can see that the project runs in loops once motion is detected and the appropriate LED actions are performed Get PIR input Green LED Status HIGH Check PIR status Motion As you can see the program logic starts by detecting the state of the PIR sensor and performs the appropriate actions accordingly With a single Arduino instruction you can only turn the LED on or off To perform the blinking operation we will need to repeatedly perform the turning on and turning off actions with a time delay between the actions We will also insert a delay between the execution of each successive loop so that the PIR sensor output can settle down Note that we will use the same flow when writing the code for both the programming methods The hardware system design Designing a diagram for your software flow helps you to write the program and also assists you in identifying actions and events for the project The process of hardware system design includes circuit connections schematic design simulation verification and testing This design process provides a detailed understanding of the project and the hardware components It also helps in preliminary verification and

Python Programming for Arduino - Pratik Desai2015-05

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