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USB Data Logger User Manual

1. FLW mh KK 5 isPrime 1 returns 1 if 1 is prime 0 otherwise 1n S 1 returns the natural log of 1 if 1 gt 0 otherwise 0 1log10 1 returns the log base 10 of 1 if 1 gt 0 otherwise 0 matchNMEAString returns 1 if a NMEA sentence has been received on the serial port input pipe and it matches the one last set using the built in matchNMEA command Syntax Effect newRxUART returns 1 if a new character has been received on the serial port input pipe for the script otherwise 0 FAW mK NtCax Fw mK Fh P qT w x Fw me Hh 5D T w x G N G Ww mK mK dD Ph Pp qT ct w w xX xX FAW mK 5 qT w x Fw mK qT w x also Syntax Effect notEmpt yUART returns 1 if the serial port input pipe is not empty otherwise 0 numDivisors 1 returns the number of divisors of 1 oneWireCRC 1 return the OneWire CRC of the SoneWire buffer of up to 1 bytes openADC 1 configure pin 1 as analog input openCapture 1 2 open pin 1 as a frequency counter input in mode 2 openCaptureHighFrequency 1 open pin 1 as a high frequency input openFallingCounter 1 open pin 1 as a counter input incrementing on a falling edge clears the counter openFrequency 1 open pin 1 as a frequency input with automatic scaling of frequency modes
2. print Sending commands to the GPS module newline Refer to the datasheet of the EMS408 for details The nmea built in command sends the output to the serial port but it also keeps a running XOR checksum that is appended to the end of the sentence for error checking The NMEA CRC is sent by using the print function pf nmea as shown below The following command sets the output sentences for the EMS408 module to be GPSS GPRMC recommended minimum specific settings nmea SPSRF100 1 4800 8 1 0 pf nmea nmea SPSRF103 4 0 5 0 pf nmea print Waiting for GPS Sentences newline precision 3 while 1 if receivedNMEAUART Rx print newline pf serialInPipe newline w T GPRMCNumBytesToMatch 32 is the number of bytes output by the internal automatic match for GPRMC sentences if SSnmea outputPtr gt GPRMCNumBytesToMatch print Output S Snmea outputPtr newline print newline Longitude abs Slongitude if SSlongitude gt 0 print E else print W print newline Latitude abs S Slatitude if SSlatitude gt 0 print N else print s print newlin Speed SSspeed knots over ground print newline Heading S Scourse degrees print newline GPS Time pf vmTime newline
3. to use to match NMEA sentences received on the serial pipe buffer maxUARTRxSize 96 0x60 the maximum capacity of the serial port input pipe buffer nmea 10 Ox0A print function constant displays the NMEA end sentence sequence including CRC useful for sending NMEA sentences Syntax Value Ef E fect Syntax Value Ef E fect Syntax Value Ef E fect Syntax Value Ef E fect Syntax Value Ef E fect Syntax Value noPause 0 0x00 used to unpause a script noRxInvUART 2 0x02 do not invert the receive Rx pin input for the serial port noRxUART 32 0x20 disables receive Rx on the serial port UART noTxInvUART 1 Ox01 do not invert the transmit Tx pin output for the serial port noTxUART 16 0x10 disables transmit Tx on the serial port UART NOUART 128 0x80 Val Syntax Val Syntax Val Syntax Val Val Val Val Effect Syntax Lue Effect Lue Effect Lue Effect Lue Effect Syntax Lue Effect Syntax Lue Effect Syntax Lue Effect port Syntax Val Syntax Val Ef Syntax Lue Effect Lue Value Ef E Syntax Value Syntax Effect pipe buffer Value Ef E Syntax Value Ef E Syntax Value Ef E Syntax Value Ef
4. Syntax setTotalSeconds 1 2 Effect if only one argument is given set the local time to the number of seconds 1 from the default time 1 Jan 2011 00 00 00 otherwise if 2 vmTime set the script s time at 1 seconds from the default time Syntax setTotalSecondsDivMod 1 2 3 4 Effect if only three arguments are given set the local time to the number of seconds equal to 1 2 3 from the default time 1 Jan 2011 00 00 00 otherwise if S4 vmTime set the script s time at 1 2 S3 seconds from the default time Syntax setVBGPinI0O 1 Effect if 1 1 enable the band gap reference voltage on the D5 Al1 output pin if 1 0 disable such output Syntax setYear 1 2 Effect if only one argument is given set the year of the local time to 1 otherwise if 2 vmTime set the year of the script s time to 1 Syntax sin S 1 Effect returns the sine of the angle in radians Syntax sizeEE Effect get the size in bytes of the general non volatile memory EEPROM emulated on memory card Syntax sqrt 1 Effect returns the square root of 1 Syntax startVM 1 Effect add the script with ID 1 to the VM environment start the script Syntax stopVM 1 Effect remove the script with ID 1 from the VM environment stop the script Syntax sum 1 2 Effect returns the sum of 2 numbers starting a
5. 00 00 00 00 00 00 00 00 2225 00 00 22 22 22 223 223 249 254 259 23 2E 1238 HOS 224 29 44 04 09 14 19 ne ne ne ne ne ne ne LLe ne ne Voltage is 1 20 Voltage is 1 19 Voltage is 1 02 Voltage is 0 49 Voltage is 0 00 Voltage is 0 39 Voltage is 0 65 Voltage is 1 11 Voltage is 1 36 Voltage is 1 36 ne ne ne ne ne giz ne ne ne ne ou ou ou ou ou ou ou ou ou ou Ww L tpu tpu tpu tpu tpu tpu tpu tpu tpu tpu SV co ct ct ct ct ct ct ct ct oct LS is is is is is TS is is is The output is ON ON ON OFF OFF OFF OFF ON ON ON We r We now describe the hardware and operation of the USB Data Logger the following text is similar to that which appeared in the original three articles in SILICON CHIP magazine December 2010 amp January and February 2011 Universal USB Data Logger Part 1 BY Mauro Grassi This simple project can log vast amounts of data onto a memory card It consumes little power and works using two AAA rechargeable NiMH or alkaline batteries USB power or power derived from another external source between 5 5V and 7V DC It can read many different types of digital and analog sensors and can even measure frequency It has a real time clock and calendar for making sense of the readings and connects to your PC using the USB We also provide a PC host progr
6. clearUART sleep 1 END CUSTOM SCRIPT Typical output from the above script is the following Output 32 000 Longitude 150 093 E Latitude 32 734 S Speed 0 380 knots over ground Heading 45 620 degrees GPS Time Mon 24 Jan 2011 11 39 52 Output 32 000 Longitude 150 093 E Latitude 32 734 S Speed 0 900 knots over ground Heading 240 940 degrees GPS Time Mon 24 Jan 2011 11 39 55 Output 32 000 Longitude 150 093 E Latitude 32 734 S Speed 0 830 knots over ground Heading 237 920 degrees GPS Time Mon 24 Jan 2011 11 39 57 Rx GPRMC 113952 000 A 3244 0343 5 15005 6054 E 0 38 45 62 240111 Rx GPRMC 113955 000 A 3244 0360 S5 15005 6020 E 0 90 240 94 240111 Rx GPRMC 113957 000 A 3244 0365 S 15005 6008 E 0 83 237 92 240111 In order to decode other arbitrary NMEA sentences you need to use the nmeaMatch built in command to set the pattern Monitoring the voltage at an input and switching a digital IO pin on and off when the reading is in range We include the following example to show how the digital IO pins can be switched under script control Even the onboard LED LED3 can be controlled from within a script This example script also uses a local function START CUSTOM SCRIPT HEADER monitoring A simple voltage monitoring script By Mauro Grassi Switches a digital IO pin HIGH whenever the voltage is above the maximum and switche
7. Directories are shown in square brackets You can double click on a file to open it You can right click a file to get a list of options This way you can transfer files from the PC to the USB Data Logger For example right clicking on a file in the device files window and choosing Get and Show File will cause the file to be downloaded from the USB Data Logger and opened Note that the file transfer functions are not as fast as would be possible if the memory card were accessed directly the speed is limited by the small resources of the 18F2753 microcontroller We recommend using a direct connection for large files of the order of 15MB or more In the script windows you can click on a script and load the source into the editor Whenever you successfully compile a script it will be added to the Host Scripts up to the maximum number A script with the same name as one already in the list will overwrite it You can also compile and send the script to the data logger using the F11 key Right clicking on the PC host script allows you to send it to the data logger once the script has been sent to the USB Data Logger it is ready to run once the PC Host is disconnected Console Window The only window we have not mentioned is the Console window in the bottom right corner which will be usually greyed out whenever there is no script executing This window is used to show the logging output of a script to simulate its behaviour If th
8. Effect VM environment mode Syntax SS ven vmNum Effect VM environment number of scripts loaded Syntax SSven vmPtr Effect VM environment script pointer Fw FW Fw me mk Hh K AW mK FAW Hh KK FNM mK 5 Hh Fw me Hh G N mK 5 Hh m N hK 3 mh m a mK to Hh Fw mK Hh E a Hita iir 3 m Ww mK bh 9 Hh H Fh Hh m N FLW me me Ph Pp Ph Pp Fw me bh 9 Hh AWN mK je Hh m a mK a Hh m uN mh ha Hh m mK 3 Hh G N me 2 Hh ntax ect ntax ect ntax ntax ect ntax ect CAX ect Tax ect CAX tax ect tax CAX ect tax tax ect CAX tax ect tax ect tax tax ect tax tax ect tax CAX v n vmRecov VM environmen ryTim SSven vmSelec VM environmen SSven vmSleep VM environmen SSven vmState t sleep recovery time in seconds ted t selected script Period t script sleep period VM environment state vm base pointer to the script structure vm CRC CRC check of the current script vm DS the DS register of the current script vm DSLIMIT the DS limit register of the current script vm IR the instruction register of the current script vm PC the program counter register of the current script vm SS the SS register of the cur
9. Global variables names begin with two characters Note that arguments to local functions are specified with a single character followed by a decimal number indicated the place in the argument list for example 1 specifies the first argument passed to the local function etc Local String Variables amp Global String Variables Local string variables names begin with a single character followed by a letter and then any number of letters and numbers Global variables names begin with two characters Local Functions amp Global Functions Local functions names begin with a single character while global functions names begin with two characters There are many defined global functions for controlling many aspects of the data logger See below for a number of example scripts that show how to use the built in commands Define Constants Define constants can be redefined at compile time but the compiler will issue a warning if this is the case note that warnings are not shown unless the Verbose check box is checked Define constants names begin with a single character The following define constants are built in note in particular the defined constants which are PRINT FUNCTION arguments which allow you to log important information along with your data including the time Syntax A0 Value 0 0x00 Effect analog channel A0 multiplexed with digital channel D4 Syntax A1 Value 1 0
10. Syntax Effect opent2C 1 opens the I2C bus running at 1 kHz Syntax Effect openIO 1 2 open a digital IO pin on pin 1 and set to input if 2 inputIO 1 of output if 2 outputI0O 0 Syntax openLowFrequency 1 Effect open pin 1 as a low frequency input Syntax openMediumFrequency 1 Effect open pin 1 as a medium frequency input Syntax openOneWire 1 2 Effect open the OneWire bus in mode 1 on pin 2 The mode can be a combination of oneWireUsingUART oneWireUsingI0O oneWireOverDrive oneWireWrite oneWireRead oneWireStrongPullUp Syntax openRisingCounter 1 Effect open pin 1 as a counter input incrementing on a rising edge also clears the counter Syntax Effect CS pin 5 Syntax Effect no openSPI 1 2 3 4 5 opens the SPI bus in mode 1 with CLK pin 2 DI pin 3 DO pin 4 openUART 1 2 3 4 opens the serial port in mode 1 baud rate 2 with Tx pin 3 and Rx pin 4 The mode can be a combination of the following constants defaultUART TxInvUART noRxInvUART openDrainUART interruptRxUART not currently implemented noTxUART noRxUART GPSDecodingUART noUART Syntax Effect script with Fw yntax Ffect Hh Fw FNM Fw hK hK me 5 5 5 qT qT qT w w w x A x G N
11. connect the batteries through the USB 5V supply via CON2 or through an external power source of between 5 5V and 7V DC the latter connects through pins 1 and 3 of CON3 see Table 2 for a complete pin out In the case that USB power or an external power source is used a linear low drop out 3 3V regulator REG2 is used to first step down the voltage A linear regulator is used here for its simplicity and its poorer efficiency over the boost regulator is justified since we assume the power source is either ultimately mains powered or powered by a substantial external battery REG2 is an LM3940 that can produce 3 3V from an input voltage as low as 5V In our case the output of this regulator is fed through a Schottky diode D1 to the input of the switchmode regulator REG1 There is a tantalum 10uF capacitor on the input used for decoupling We also use a 47uF low ESR Equivalent Series Resistance aluminium electrolytic capacitor on its output to ensure stability Do not be tempted to use a common electrolytic here it must be low ESR There is also a 1k resistor to ground to provide a minimal load The switchmode regulator steps up the voltage to the required 3 3V The selection to use either USB power or an external 5 5V to 7V DC source is made using the mini toggle switch S1 Assuming that only one of these is ever used this toggle switch can function as a power switch too The external power source has polarity protection usi
12. detach from the USB when there are no custom scripts loaded this is done to save power This will be the state of the USB Data Logger after it has been first switched on As this can affect the installation of the driver since the USB connection may be lost during the driver installation it is advisable to install the driver with no memory card inserted in the socket The USB Data Logger has a much longer initial timeout period if this is the case which should be sufficient for old and slow systems up to two minutes If that is not enough you can always press S2 to add another five seconds to the timeout This should not be necessary in most cases as the driver installation will take less than a minute This feature is provided as a fail safe feature in case the USB Data Logger is used with a very old system SC Appendix 1 USB Data Logger Parts List Miscellaneous 1 PC board coded 04112101 and measuring 60 x 78 mm 1 Plastic Instrument Case black or grey Altronics H 0342 or H 0343 1 SPDT Toggle Switch sub mini S1 Altronics S 1421 1 Momentary Toggle Switch sub mini S2 Altronics S 1498 1 28 pin IC socket 0 3 or 2 14 pin IC sockets 1 20 MHz crystal X1 1 32 768kHz crystal X2 Altronics V 1902 Farnell 145 7085 1 USB TYPE B socket vertical PCB mount Farnell 107 6666 1 2 AAA battery holder Jaycar PH 9226 2 AAA NiMH rechargeable 900mAH batteries Jaycar PH 9226 or 1 2pk AAA 950mAh NiMH rechargeable 950m
13. lt and gt brackets while optional parameters are enclosed in and brackets both are shown in italics SCRIPT script this keyword together with the HEADER header keyword is used to declare a script It is followed by the name of the script and the body of the script which is enclosed in curly brackets The syntax is script lt script name gt lt script body gt SLEEP sleep suspends execution of this script for the specified number of seconds The syntax is sleep lt number of seconds gt For eg sleep 10 suspends execution for 10 seconds SLEEPUNTIL sleepUntil suspends execution of this script until an absolute time in the future The syntax is sleepUntil vear month day hour minute lt second gt For eg sleepUntil 1 13 23 24 will suspend execution until the day of the month equals 1 and the time is 13 23 24 You can omit all the arguments except the seconds TIMEUNTIL timeUntil returns the number of seconds until the nearest absolute time in the future that matches the argument The syntax is timeUntil month day hour minute lt second gt For eg timeUntil 10 will return the number of seconds until the next absolute time when the seconds equal 10 TIME time loads the script s time register with a specific time The syntax is time month day hour minute lt second gt PRECISION precision sets the number of decimal places to display when printing the value of a float
14. show are s SSvm time SSvm current sleep mode of the current script stackSizePtr stack size pointer register of the current script pP pPipe e nter to the script s time register e day ster of the script s time register e hours e mins register of the script s time register e month e secs register of the script s time register e show register of the script s time register determines which fields hown e updated updated register of the script s time register e wday week day register of the script s time register SSvm year SSvm N A N A N A SSvm SSvm SSvm e year register of the script s time register eOffset eScaling eSpeed typeMode the implicit argument type register of the current script Built In Global Functions The following global functions are defined Fi wn mK ntcax CAX ect Fl w mK bh 9 ntax fect herwise o HU a a e i a yntax fect therwise o ma yntax fect therwise oOo HU yntax fect therwise o Hu yntax fect therwise o Hu Fw yntax ffe Hh Q 1 AN AW AN AN AN AN AN AW AN me mK me mK me me me mK mK 5 5 5 5 5 5 5 5 5 g g qT qT T T T ct ct w w w w w w w w w x A Pa a x A x A x AW mK FAW mK abs 1 returns the absolute value of 1 acos 1 returns the arc cosine
15. 134 815 116 437 178 739 520 342 183 844 725 226 747 688 430 31 652 693 554 635 336 198 159 340 141 There were exactly 100 numbers generated Their sum is 46150 817 905 921 449 Deh Logging the input to the serial port A very common application is to log the input to the serial port The following script accomplishes just that even toggling a LED to acknowledge the input Note that when using the on board serial port the levels are 3 3V levels and may not be compatible with native serial ports that use different voltage levels You may need to add a small voltage translator circuit comprising a few transistors to interface the hardware correctly START CUSTOM SCRIPT header echoUARTToFile This script shows how to log the serial port input pipe onto the log file It simply prints out any characters received on the serial port By Mauro Grassi script echoUARTToFile open the serial port at 115200 bps Tx on D5 and Rx on D4 open D0O as a digital output which we toggle to acknowledge reception of a character openlIO D0 outputIoO clear the log file for this script clearFile echooutput txt openUART 0 115200 D5 D4 clearUART while 1 if newRxUART store the last received character SC SSserial lastRx output
16. 4 7k resistor to the 3 3V rail but the input pins in IC1 that they connect to are actually 5V tolerant You can also use the frequency inputs to act as simple counters that increment on edge transitions can count up to 32 bits Note that if you require greater voltage amplitude you can of course change the voltage divider associated with inputs D4 A0 and DS5 A1 however we won t cover how to do this here Digital Sensor Support Not just varying voltage and varying frequency sensors can be connected however The great flexibility of this design is that you can connect I2C One Wire Dallas and serial port UART sensors too Problems to do with the inaccuracy of the ADC conversion are thus circumvented The I2C and One Wire connections are made using the digital input outputs DO D3 pins 1 4 of CON4 There are 4 7k pull ups to the supply rail on each of these lines as required for both One Wire and I2C operation these buses use open collector outputs that need external pull ups to allow multiple devices to be connected to the same bus The great thing about using I2C sensors is that you can connect many different sensors to the same I2C bus which only requires two lines as many as 127 I2C devices can be connected to the same bus Similarly only one line is required to connect many different One Wire Dallas sensors to this data logger The Peripheral Pin Select feature of IC1 allows a number of on board peripherals to be routed
17. E fect fect functi fect fect fect fect disables the serial port function UART oneWireOverDriv 32 0x20 use over drive speeds on the OneWire bus oneWireRead 1 0x01 select read direction for the OneWire bus oneWireStrongPullUp 4 0x04 enable a strong pull up on the OneWire bus oneWireUsingIO 16 0x10 use a digital IO pin for the OneWire bus implementation oneWireUsingUuART 0 0x00 use the serial port for the OneWire bus implementation oneWireWrite 2 0x02 select write direction for the OneWire bus openDrainUART 4 0x04 enables open drain output for the transmit Tx pin on the serial outputIoO 0 0x00 indicates the IO pin is to be opened as an output pause 128 0x80 used to pause a script pi 3 14159 the mathematical constant PI useful for trigonometric ons among other uses serialInPipe 25 0x19 print function constant displays the contents of the input serial serialPipe 32768 0x8000 the serial pipe over the script s serial port showDay 1 Ox0O1 display the day of the month showDefault 127 Ox7F display the system default time settings showHours 16 0x10 display the hours Syntax showMinutes Value 4 0x04 Effect display the minutes Syntax ShowMonth Value 32 0x20 Effect display the month Syntax showSeconds Value 8 0x08 Effect display the seco
18. Effect 32 bit floating point value indicating longitude in degrees lt 0 indicates West gt 0 indicates East set by the system if a GPS module is present and outputting valid GPS GPRMC NMEA sentences through the serial port Fw yntax Ffect Hh G N me 2 LI w x FNM mK 5 qT w A Fw yntax Ffect Fw yntax Fw mK Fh DP qT w xX FAW mK Fw yntax Ffect SSnmea match string user defined NMEA match string command buffer SSnmea match stringPtr NMEA match string command buffer pointer SSnmea output byte array contains the raw output of any NMEA sentence match SSnmea outputPtr position pointer to the byte array containing the raw output of any NMEA sentence match can be used to size the output SSoneWire the OneWire internal buffer SSoneWireRomCode the OneWire Rom Code buffer SSpor is 1 if a POR Power On Reset has occurred otherwise 0 S return 32 bit floating point return value variable can be used for returning values from local functions Syntax Effect Syntax Effect S serial the serial input pipe buffer Sserial RxCRC byte value used to accumulate the CRC checksum for the serial port input pipe buffer also used for NMEA sentence decoding Syntax SSserial TxCRC Effect byte val
19. Effect set the digital output pin on pin 1 to high if 2 highIO 1 or low if 2 lowI0 0 Syntax setLED 1 Effect set the onboard LED LED3 on for 1 ms system limited Syntax setLocalTime 1 Effect set the RTCC Real Time Clock Calendar clock with the script s time register or the argument 1 in the form time YYYY MM DD hh mm ss Syntax setMinutes 1 2 Effect if only one argument is given set the minutes of the local time to 1 otherwise if 2 vmTime set the year of the script s time to 1 Syntax setMonth 1 2 Effect if only one argument is given set the month of the local time to 1 otherwise if 2 vmTime set the month of the script s time to 1 Syntax setSPICS 1 Effect set the SPI bus CS line to 1 Syntax setScriptTime 1 Effect set the script s time register the argument 1 can be a time in the form time YYYY MM DD hh mm ss Syntax setSeconds 1 2 Effect if only one argument is given set the seconds of the local time to 1 otherwise if 2 vmTime set the year of the script s time to 1 Syntax setShowScriptTime 1 Effect set the show mode for the script s time register where 1 is a combination of the following constants showDay showWeekDay showMinutes showSeconds showHours showMonth showYear showDefault
20. a combination of upper and lower case letters for keywords eg HEADER and header are both OK but heAder is not Note that all other parts of the compiler are case sensitive The compiler will give useful error and warning messages together with the line and column number of the error warning This makes it easy to fix any syntax errors The header is followed by the script s body of code This is similarly defined using the SCRIPT keyword followed by the name of the script followed by the custom script code again enclosed in curly brackets Lines starting with two slashes are comments and are ignored by the compiler like C Curly brackets are used to group statements which are always terminated by a semi colon In this case the script has a single command PRINT which takes the argument Hello World a string and a newline The arguments to the PRINT command are separated by commas The output is actually written to the log file for that script each script has its own log file although it is also possible for a script to write another script s log file too That s the first program we now run through a number of scenarios and each section presents a custom script to do a particular task We ve chosen the most common types of tasks that people would want to do Sample code can also be downloaded from the SILICON CHIP website Reading An Analog Sensor One of the most common things you ll want to do is to log a voltage varyi
21. a comma separated argument to the print command and other commands using the same comma separated argument list to override the default printing of a number This command forces the display to be an integer relative to the indicated base The syntax is base lt value gt lt base gt lt numdigits gt where lt value gt is the value and lt base gt is the base and lt numdigits gt is the number of digits to print the lt numdigits gt argument can be omitted For example base 10 16 will print A the hexadecimal code for 10 CHAR char this command can be used in a comma separated argument to the print command and other commands using the same comma separated argument list to print the ASCII character corresponding to the argument The syntax is char lt value gt For example char 0x41 will print A WHILE while this command is used to execute a command block as long as a condition holds The syntax is while lt conditional gt lt block gt The block of code is executed as long as the conditional is non zero If lt block gt is a single command the curly brackets can be omitted but a semi colon must terminate the statement AND and used to combine two conditional statements to form a compound statement that is true precisely when both are true XOR xor used to combine two conditional statements to form a compound statement that is true when exactly one is true OR or used to combine two conditional statem
22. a weather station with humidity wind speed rainfall temperature and barometric pressure sensors You can log their values over many days onto a CSV comma separated values file on the memory card Then connect the data logger to your Windows PC to download the file through the USB or simply using a memory card reader and open it using Open Office or MS Exel It is then easy to graph the readings and analyse them In another application you may want to diagnose a problem with your car s engine You can monitor the relevant sensors and log them while driving then later analyse the data to find the problem You can even log your trajectory if you use a GPS module with the USB Data Logger There are many applications where this project would be useful we ve made it as flexible as possible and able to accept many different types of sensors Circuit Description The circuit for the USB Data Logger is shown in Fig X and is based around a PIC18F27J53 microcontroller from Microchip IC1 We use the version in a slim 0 3 28 pin through hole dual in line package SDIP The PIC18F27J53 is an 8 bit microcontroller with 128KB program memory and 3KB of SRAM and is well suited to this application due to its impressive list of peripherals and low price The following are the peripherals that we use in this project the USB device peripheral the integrated RTCC Real Time Clock Calendar with separate oscillator circuit its low power sleep
23. as this is the first pin to solder Heat the pin and apply the solder quickly making sure never to apply heat for more than a few seconds The solder should melt easily and adhere to the pin and pad Let it cool Once pin 5 has been soldered you can proceed to solder in pin 3 which is diagonally opposite Once that is done you can remove the sticky tape and proceed to solder the remaining 3 pins If any solder bridges form use solder wick to remove them Altronics T 1210 Jaycar NS 3026 also known as de soldering braid While you are on the top side of the PC board you can solder in the memory card socket as well It has two small plastic feet that fit into holes on the PC board This will anchor it in position over its pads Solder the two holding pads on its sides first these will secure it in position Once that is done you can proceed to solder in the rest of the pins see photo Again use solder wick if you accidentally create solder bridges between adjacent pins and be careful not to apply heat to the plastic body as it will melt Once that is done you can proceed to install the resistors The correct value must go in each place You should refer to the resistor colour code table in conjunction with the component overlay diagram shown in Fig X It would be even better to check the resistors with a DMM to dispel any doubt Unlike most kits due to space restrictions the resistors are mounted vertically see photo Ther
24. at around 1Hz If the PC Host is connected it will flash slightly quicker than that It will also flash when responding to reading or writing of the program memory The bootloader interface is very simple The Read Memory button allows you to read the contents of the program memory and save the result to a text file The Verify Memory button allows you to check the contents of the memory against a hex file Note that if the bootloader detects that there is no main application loaded it will not run it but enters the bootloader mainloop instead The Write HEX allows you to program a new firmware image onto the FLASH memory from an Intel Hex file typically produced by embedded compilers like the C18 from Microchip You can also write the program memory from a binary file with the Write BINARY button Note that a verify is always performed after a write operation To program a new image supplied in a hex file simply start the bootloader click on Write HEX An open file dialog will open allowing you to choose the hex file Click Open The PC host will read the file check the image and proceed to erase and program the device It will also verify the contents afterwards The PC Host bootloader program checks the image before programming it to check that it is compatible Then it asks you to confirm the operation after which time the memory is erased and the new image is reprogrammed Note that all set
25. bus the use of this extra pin should not be a problem In the alternative mode the 1 wire drivers use a single digital pin and are implemented using a general IO pin of the microcontroller In this mode only one pin connects to the sensor We recommend using the UART mode unless the extra pin is absolutely required For this example we connect DO and D1 together to the DQ input of the DS18B20 sensor We first present a custom script that can be used to discover the sensor s ROM code as shown below START CUSTOM SCRIPT header oneWireReadROM Empty Header script oneWireReadROM Sample Script showing how to discover the ROM code of a 1 wire sensor in our case a DS18B20 digital thermometer connected to pins DO D1 openOneWire oneWireUsingUART 0 WHILE 1 PRINT Connecting to One Wire Sensor RESULTt resetOneWire IF RESULT PRINT Ok NEWLINE sendOneWireCommand 0x33 64 oneWireRead 0 PRINT The ROM Code is A 0 WHILE A lt 8 PRINT 0x base oneWire A 16 2 A A 1 PRINT NEWLINE j ELSE PRINT Error NEWLINE SLEEP 3 END CUSTOM SCRIPT Hardware UART or IO based 1 wire drivers Execution begins at the statement openOneWire oneWireUsingUART 0 which is a global builtin function Its first argument selects whether the one wire bus should be implemented using a UART which takes two pins or using a general IO pin using only one p
26. by any sensors being powered from the USB Data Logger itself note also that this only applies when the USB Data Logger is being powered from the 2 AAA cells as mentioned in Part 2 last month this is because of the higher consumption of the linear regulator if an external source of power is used or the USB There are a number of situations when the USB Data Logger will go into standby mode At any time you can wake up the data logger by pressing pushbutton S2 You can also bring the USB Data Logger out of standby by inserting a memory card into its socket as an internal comparator interrupt is armed prior to the microcontroller going into sleep When the USB Data Logger goes into standby it will detach itself from the USB the PC Host will show itself as being disconnected Note that the USB Data Logger will go into standby as much as possible to save power it will go into standby in the following cases 1 When there are no custom scripts loaded or 2 When all the custom scripts that are loaded are paused or not running 3 When there is a large time delay where no custom scripts need to run This delay is set at 5 seconds This means that scripts that sleep for periods greater than or equal to 5 seconds will be much more power efficient than those that don t 4 When the undervoltage protection is enabled and the input voltage to REG1 is below the set threshold Note that as mentioned in Part 1 December 2010 i
27. case these cables are common place these days and one should be easy to acquire The supplied Libusb driver should work with all Windows versions including 64 bit Windows 7 versions with which we ve developed this project We give the instructions for installing the driver on a Windows 7 machine but the procedure is similar for other Windows versions Unzip the contents of the file usbdatalogger zip to a directory on your hard disk this can be done by right clicking on the file and choosing Extract All The file can be downloaded from the downloads area of the SILICON CHIP website This zipped archive contains both the driver and the PC host software files Then connect the USB Data Logger after you ve checked that it is working correctly to your PC using the USB cable You don t need batteries for this since it can be powered directly from the USB port by moving switch S1 s position to up Windows should recognise the new device and prompt for the installation of the driver It may then try to install the driver automatically but this will fail because the driver won t be part of the driver database yet You will get the message Device Driver Software was not successfully installed Go to Control Panel gt Device Manager A window should appear similar to the one shown in Fig X You will see the device USB Memory Card Data Logger with an exclamation mark Select it and right click Select the Update Driver Softw
28. getTotalSecondsMod 1 2 Effect if no argument is given return the total number of seconds from the default time 1 Jan 2011 00 00 00 until the local time modulo 1 gt 0 otherwise if 2 vmTime from the default time to the script s time modulo 1 gt 0 Syntax getUART Effect reads a character from the serial port input pipe if available otherwise 0 Syntax getWeekDay 1 Effect if no argument is given return the week day of the local time otherwise if 1 vmTime return the week day of the script s time O Monday 6 Sunday Syntax getYear 1 Effect if 1 is not given get the year of the local time from the RTCC Real Time Clock Calendar otherwise if l vmTime get th year of the script s time Syntax Effect initRandom 1 2 initialises the pseudo random generator modulo 1 and with seed 2 returns 2 modulo 1 Fw yntax H Fw mK T w x G N mh KK a qT w x FAW yntax Ffect int 1 returns the integer part of 1 isTOHigh 1 returns 1 if the digital IO pin 1 is high otherwise 0 isIOLow 1 returns 1 if the digital IO pin 1 is low otherwise 0 isLeapYear 1 if no argument is given return 1 if the local time s year is a leap year otherwise return 1 if 1 is a leap year otherwise 0 FAW me Ntax Fw me Fh P qT w x m uN Ficka Fh P qT w x tax fect
29. itself will automatically increment on each read so we use this function to read the bytes at addresses 0 and 1 Again it returns 1 if successful or 0 otherwise If successful the data is written to an internal buffer which is a global variable I2C Global variables are visible by all scripts and always start with two characters as opposed to local variables In this case we use the round brackets to specify offsets of 0 and 1 to the buffer Using round brackets reads the data as a byte whereas using square brackets reads it as a 32bit point floating number In this case 12C 0 represents the 8 MSB bits of the 10 bit temperature and the two LSBs of I2C 1 represent the 2 LSB bits of the 10 bit temperature So the temperature is stored in the local variable T The script then logs the value and ends up at the SLEEP 30 command which suspends execution for 30 seconds before the cycle repeats Of course it is possible to sleep for a variable amount on each cycle For example in the script presented above if the I2C temperature sensor read gives an error we could choose to retry in 3 seconds rather than 30 You would simply move the SLEEP 30 command inside the first block of the IF statement and add a SLEEP 3 command after the PRINT Error NEWLINE command Conclusion What should now be apparent in all these cases is a very general pattern that each script executed an initialisation sequence once befor
30. makes it highly configurable and so easy to adapt to your application This means that it can be used to interface to a very wide range of digital sensors almost any I2C and l wire sensor can be used as well as almost any analog sensor frequency input or counter END OF BREAKOUT PANEL Universal USB Data Logger Part 3 In last month s article we started describing how to use the Universal USB Data Logger In this final article we finish with a few more example scripts to use with the Universal USB Data Logger explain in detail how to use the Windows PC host software and give a few Tips and Tricks that show some of what this data logger can do BY Mauro Grassi Errata In the circuit diagram published in Part 1 December 2010 and in the overlay diagram published in Part 2 January 2011 there is a 22uF tantalum capacitor on the output of REGI the boost regulator This should be replaced by a 220uF 10V LOW ESR electrolytic capacitor Jaycar RE 6300 instead The parts list that appeared in Part 1 should be amended accordingly too Also there was a 22uF TANTALUM capacitor missing from the schematic published in Part 1 December 2010 which should now be the 220uF capacitor mentioned above Introduction In last month s part we showed how to install the Windows driver and gave a number of example custom scripts to get you started You will want to know how to upload custom scripts to the USB Data Logger using the USB In this m
31. program connects to the USB Data Logger and can be used to compile custom scripts transfer files to and from the USB Data Logger and a few other functions You can run the executable program to get the window shown in Fig X Overview of the PC Host Program The PC host program supplied can be used to compile simulate and load custom scripts onto the USB Data Logger It also allows files to be transferred to and from it to download logs and configure the USB Data Logger as well as synchronising the real time clock Note that since all files are stored in a FAT filesystem the memory card can also be connected directly to a PC with a memory card reader or through a USB memory card reader This would be desirable if transferring very large files more than 15MB say as it can access the memory card substantially faster than the USB Data Logger s microcontroller can The PC host program is based around a Windows GUI Graphical User Interface and was written in Visual C The custom scripting language compiler and parser were also written in C with help from the open source parser and lexical analyser generators Bison and Flex The VM engine was written using the full version of the C18 compiler donated by Microchip When running and the USB Data Logger is connected with the driver installed the PC host program will detect it automatically You will then be able to write compile and send custom programs to the USB Data Logger each sc
32. scripts Note however that the same global variable accessed from different scripts may still access different physical memory For example while the return global variable is common to all scripts this is not true for the vm global function which accesses the virtual machine associated with the script Global function names begin with two characters local function names begin with one character Similarly global variable names begin with two characters while local variable names begin with one character Numeric Constants The scripting language natively recognises numeric constants in one of the following formats Decimal Integer an integer specified base 10 is simply a string made up of a finite number of decimal digits in the range from 0 9 inclusive For eg 192 Hexadecimal Integer an integer specified base 16 is a string made up of the constants Ox followed by a string made up a finite number of hexadecimal digits in the range 0 9 and A F or a f For eg OxA8 Binary Integer an integer specified base 2 is a string made up of the constants 0b followed by a string made up a finite number of binary digits in the range 0 1 For eg 0b1101 Floating Point Number a 32 bit floating point number for eg 1 34 Built In Commands reserved keywords The following built in keywords are part of the scripting language Note that the syntax is specified as follows Necessary parameters are enclosed in
33. to different pins of the microcontroller In this project it is used to allow an output input pin of CON4 to be reconfigured for different sensors There are six pins associated with digital sensors labelled D0 D5 pins 1 6 of CON4 Note that D4 and D5 share their function with analog pins AO and A1 These two pins can function in only one mode at any one time ie either digital or analog but not both Finally there is support for a configurable full duplex serial port UART to be used For example this allows a GPS module to be connected such as the EM 408 featured in the October 2010 issue of SILICON CHIP Altronics K 1131 This enables position as well as time information to be logged You can also use the GPS module to gather accurate time information from the GPS satellites rather than relying on the onboard RTCC More on these options in next month s article Yes you can even use the GPS module to synchronise the on board RTCC Scripting Language The Universal USB Data Logger uses a scripting language to allow you to configure it to read many different types of digital sensors This is a powerful feature that allows the USB Data Logger to be used with many different types of sensors as each digital sensor is different in the interface that it presents We ve written a Windows PC host program that can parse a custom scripting language to interface to many different types of sensors The scripting language is compiled and t
34. to be multiplexed on different lines For example a single UART peripheral and this microcontroller has two independent UARTs can be used on different pins With the USB Data Logger we use this feature to provide access to a number of logical UARTs across different custom scripts That is although there is only one physical UART used at any one time it is multiplexed across the running scripts so that each script can have its own UART only one per script though The UART can be configured with inverting receive and transmit buffers it can also be configured with an open drain output For example you can have one custom scripts sending data to a serial port on pin DO at 9600 bps while having another script sending data to an independent serial port on pin D1 at 115200bps The hardware state is saved and changed as required by the firmware for the currently executing custom script The same applies to the l wire peripherals the I2C bus is different and its pin out is fixed however Note that you can have different scripts writing to the same I2C bus though Startup Behaviour System Log After a Power On Reset POR the USB Data Logger will not have its time set You can set the time by connecting it to your PC and running the PC Host program Note that after such a reset the USB Data Logger will try to run any scripts that were running last The first few lines of the system log are shown below Note that System Logging can be en
35. 0 3 6V 4 3 3 4700 5170 The reason for the smaller resistors on these two inputs is that it allows them to also be used for digital functions then we refer to them as D4 and D5 respectively Internal Voltage Reference Note that the absolute accuracy of the 12 bit ADC conversion depends on knowing the exact supply voltage to the microcontroller While this is nominally 3 3V in actual practice it may be off by up to 0 1V due to manufacturing variations For this reason the firmware will measure the supply voltage to IC1 regularly using an internal band gap reference 1 2V 5 and adjust its readings accordingly Due to the error in the reference the error in the digitised analog voltage value can be as high as 5 although it will be typically better This means that the error in the analog sensor readings will be at worst as high as this too Voltage Reference For Greater Accuracy If higher than 5 precision is required for the analog sensors a more precise voltage reference can be connected to one of the four analog inputs This reference can then be used to accurately measure the other analog sensors How to do this will be explained in next month s article The Universal USB Data Logger also accepts up to six frequency inputs frequencies up to 192 kHz can be measured Up to two such inputs can be of amplitude up to 4V while the others must be in the range 0 5V Note that the inputs DO D1 only have a pull up
36. 1 makes up the hardware interface to the memory card Higher level layers add support for a FAT File Allocation Table file system This file system has the advantage that it can be used with almost all operating systems in common use As to the hardware MMC SD SDHC cards can be accessed in their native mode or in SPI mode The advantage of SPI mode is that it makes the hardware layer easy to implement The interface with SPI is simpler but the penalty is slower transfer speeds However the SPI speeds are adequate for data logging The microcontroller communicates with the memory card over one of the two on board SPI buses SPI2 It also has hardware support for DMA Direct Memory Access for the SPI peripheral which allows data to be transferred to and from the memory card transparently while the microcontroller is executing code This makes the transfers very efficient SPI communication uses a four line bus and is capable of full duplex transfers between a host and a slave The four lines are bar CS chip select active low SO serial data output SI serial data input and SCK serial clock In this case the microcontroller is the SPI master and controls the bar CS line When it is pulled low the memory card becomes active and listens for commands The SPI peripheral is routed via the PPS Peripheral Pin Select feature of IC1 so that the SCK line is at pin 21 and the SI and SO lines are at pins 18 and 22 respectively The lat
37. 65 0000 The square root is 8 0623 The integer part of the sqrt is 8 0000 The fractional part of the sqrt is 0 0623 The sine is 0 8268 The cosine is 0 5625 The tangent is 1 4700 e to the power of A 100 is 1 9155 The natural log is 4 1744 The log base 10 is 1 8129 The arcosine of SA 100 is 0 8632 The arcsine of A 100 is 0 7076 The arctangent of A 100 is 0 5764 There are even more maths functions START CUSTOM SCRIPT header imaths The following script shows the built in global maths functions By Mauro Grassi Override the default behaviour we want it to run only once xecMod xecModeNoRestart script imaths SB 100 0 SA 1 Scounter 0 print The following numbers from 1 to 100 are primes newline while SA lt 100 if isPrime SA store the prime number B Scounter SA if Scounter 8 0 print SA else if Scounter 8 7 print SA newline print SA Scounter Scounter tl SA SA t1 SA 0 while A lt Scounter print SA SB SA newline SA SA 1 print newline There wer xactly Scounter primes found newline print Their sum is sum amp SB Scounter newline END CUSTOM SCRIPT Typical output would be The following numbers from 1 to 100 are primes 27 Sy Oy 17 Ay Ey Meh 9 23 29 31 37 41 43 47 53 597 Oly 67 TL yp TIm 19 83
38. 7 89 97 n There were exactly 25 primes found Their sum is 1060 H Random Numbers You can also use pseudo random numbers START CUSTOM SCRIPT header random The following script shows the built in random number global functions By Mauro Grassi Override the default behaviour we want it to run only once xecMod xecModeNoRestart script random SB 100 0 SA 1 Scounter 0 print The following 100 numbers are randomly generated betw newline A Leandi Logos My initRandom 1000 41 while SA lt 100 store the prime number SR rnd 1000 SB Scounter R if counter 8 0 print SR else if counter 8 7 print SR newline else prin Tp y SR counter counter 1 SA SA 1 print newline Ther print Their sum is wer xactly Scounter sum amp SB Scounter numbers generated newline newline END CUSTOM SCRIPT Typical output would be H The following 100 numbers are randomly generated between 1 and 1000 862 103 164 445 346 267 608 769 150 151 172 613 874 355 456 577 118 479 60 261 482 123 584 265 566 887 628 189 970 371 792 633 294 175 676 197 138 899 880 481 102 143 4 85 786 507 648 609 790 591 412 653 714 995 896 158 319 700 701 722 163 424 6 127 668 29 610 811 32 673
39. Ah batteries Altronics S 4742C 1 8 way Horizontal PC mount 5 08mm pluggable terminal block header Altronics P 2598 Jaycar HM 3108 1 8 way screw terminal socket Altronics P 2518 Jaycar HM 3128 1 4 way Horizontal PC mount 5 08mm pluggable terminal block header Altronics P 2594 Jaycar HM 3104 1 4 way screw terminal socket Altronics P 2514 Jaycar HM 3124 1 Memory card socket Jaycar PS 0024 Semiconductors 1 PIC18F27J53I SP microcontroller IC1 Farnell 181 4996 4 1N5819 diodes D1 D4 1 1N4004 diode D5 1 2N7000 FET Q1 1 TPS61097 33DBVT boost regulator REG1 Farnell 175 5714 1 LM3940 3 3 linear regulator REG2 1 LED 3mm blue LED1 Altronics Z 0707 Jaycar ZD 0130 Inductors 1 100uH choke Altronics L 7034 Jaycar LF 1534 Capacitors 1 220uF LOW ESR 10V C5 1 47uF LOW ESR 63V C13 2 22uF TANTALUM C7 C9 2 10uF TANTALUM C12 C14 1 4 7uF TANTALUM C18 4 100nF monolithic C1 C2 C6 C16 2 10nF monolithic C3 C4 110nF greencap C17 2 33pF ceramic C8 C10 2 12pF ceramic C11 C15 Resistors 1 330k R22 3 33k R16 R21 R23 2 15k R3 R4 10 4 7k R6 R7 R8 R9 R10 R11 R12 R13 R18 R19 2 Ik R14 R15 3 470 R1 R2 R5 2 10 R17 R20
40. From The Sensor the address increments automatically SRESULT getI2C I2C_ ADDRESS 2 if RESULT Compute the Temperatur T I2C 0 I2C 1 256 0 print The Temperature is T degrees Celsius else print Read Error newline sleep 3 END CUSTOM SCRIPT Typical output would be The Bus Speed is 400 000 The Temperature is 25 875 degrees Celsius Reading a OneWire Sensor The following script is used to read a OneWire sensor START CUSTOM SCRIPT header oneWireReadROM Empty Header script oneWireReadROM Sample Script showing how to discover the ROM code of a 1l wire sensor in our case a DS18B20 digital thermometer connected to pins DO D1 openOneWire oneWireUsingUART 0 WHILE 1 SRESULT resetOneWire PRINT Connecting to One Wire Sensor IF SRESULT PRINT Ok NEWLINE sendOneWireCommand 0x33 64 oneWireRead 0 PRINT The ROM Code is SA 0 WHILE SA lt 8 PRINT 0x base SSoneWire SA 16 2 SA SA 1 PRINT NEWLINE copyOneWireBufferToRomCodeBuf fer 0 SA 0 print ROM Code while A lt 8 print base SoneWireRomCode A 16 2 SA SA 1 print newline RINT Error NEWLINE EEP 3 E
41. In Header Objects The following header objcets are built in Inside the code block for the header at the start of a script you can define either define constants or assign constant values to header objects This can be used to override the default behaviour of a script For example including the following header in a script will prevent the script from resetting if it halts the default behaviour header noRestartHeader execMode execModeNoRestart The following header objects are defined Syntax execMode Effect set this to override the default execution mode of the script which restarts automatically if it halts possible values include defaultExecMode xecModeNoRestart Syntax execPriority Effect set this to override the default execution priority of the script the higher the number the more priority the default is defaultPriority String Constants 6699 String Constants are specified with double quotes Comments Single line comments begin with two characters Using Strings While most variables are 32 bit floating point numbers you can also declare and use string variables Strings are 0 NULL terminated sequences of 8 bit characters ASCII which are stored in memory Local string variables names begin with a single character which is supposed to be reminiscent of the dereferencing operator in C In analogy with variables and func
42. ND CUSTOM SCRIPT Typical output would be Connecting to One Wire Sensor Error Connecting to One Wire Sensor Error Connecting to One Wire Sensor Ok The ROM Code is 0x28 0xCB 0x8A 0xC2 0x02 0x00 0x00 0x7E ROM Code 28 CB 8A C2 02 00 00 7E Connecting to One Wire Sensor Ok The ROM Code is 0x28 0xCB 0x8A 0xC2 0x02 0x00 0x00 0x7E Fl Fl ROM Code 28 CB 8A C2 02 00 00 7E Connecting to One Wire Sensor Ok The ROM Code is 0x28 0xCB 0x8A 0xC2 0x02 0x00 0x00 0x7E ROM Code 28 CB 8A C2 02 00 00 7E Connecting to One Wire Sensor Ok The ROM Code is 0x28 0xCB 0x8A 0xC2 0x02 0x00 0x00 0x7 ROM Code 28 CB 8A C2 02 00 00 7E Fl ira Maths Functions The following script uses a number of built in maths functions global functions START CUSTOM SCRIPT header maths The following script shows the built in global maths functions By Mauro Grassi Override the default behaviour we want it to run only once xecMod xecModeNoRestart script maths SA 100 Display Up To 4 decimal places precision 4 while A lt 100 print The argument SA is SA newline print Absolute Value is abs SA newline print The square root is sgqrt SA newline print The integer part of the sqrt is int sqrt SA newline print The fractional part of the sqrt is frac s
43. S18B20 Dallas Maxim 1 wire temperature sensor The DS18B20 is a digital thermometer which can be powered from 3 5 5V and measures temperature between 55 and 125 Degrees Celsius The thermometer s resolution is user selectable between 9 and 12 bits Each such sensor that is manufactured has its own unique 64bit ROM code which acts to identify a particular device when multiple devices are connected to the same 1 wire bus The type we are using comes in a TO 92 package with three leads Pin 1 is ground and connects to the GND terminal of CON3 Pin 2 is the DQ line which connects to the 1 wire bus while Pin 3 can be left disconnected and is used to supply power to the sensor it should be between 3 5 5V with respect to the GND terminal In this example we are going to connect only the DQ line to the 1 wire bus 1 Wire Bus Hardware Connections The 1 wire bus drivers in the USB Data Logger s firmware can function in two distinct modes that reflects their underlying implementation In the default mode the UART peripheral is used to access the 1 wire bus In this mode two digital pins are required and must be connected together to the single 1 wire bus terminal of the sensor The two pins can be connected together at the CON4 terminals This mode is preferred because it does not require real time timing but it has the drawback that two pins rather than one pin are required In any case since more than one 1 wire sensor can be connected to the same
44. START CUSTOM SCRIPT header runningAverages Set the constant to be the number of readings to keep numberOfReadings 8 script runningAverages This custom script shows how to keep a running average of a reading by storing only the last 8 readings and averaging them to get the actual value by Mauro Grassi the variable N stores the number of readings that we have captured SN 0 The following is used to point to the current place in the circular buffer P 0 The following array is used to store the latest readings X numberOfReadings 0 Say we are measuring a voltage although any variable value can be averaged in the same way MINMAXSET 0 openADC 0 WHILE 1 Get the reading V readV 0 IF MINMAXSET IF V lt MIN MIN V ELSE IF V gt MAX MAX V ELSE intialize the min amp max values MIN SV MAX V MINMAXSET 1 Store the reading X P J V Increment the pointer IF P lt numberOfReadings 1 j ELSE P P 1 The buffer is circular so wrap to the beginning P 0 Increment the number of readings acquired N N 1 Compute the average IF N lt numberOfReadings A sum amp X 0 N N ELSE A sum amp X 0 numberOfReadings numberOfReadings PRINT The running average after N readings is A NEWLINE PRINT The Maximum is MAX The Minimum i
45. USB Data Logger User Manual This User Manual refers to the Software Firmware Version 9 90 Other versions may differ in some details By Mauro Grassi Tips A note on the Installation of the Windows PC Host Software As an addendum to the instructions given in the original series of articles in SILICON CHIP December 2010 January February 2011 the PC Host uses the Windows default programs to open files to display them the default program depends on the extension of the file The most common extensions used by the PC host are txt the default program is usually NotePad but this can be overridden The next most common file extension used by the PC Host is bin indicating a binary file Windows OSs will not usually be setup to automatically display this type of file Therefore we recommend installing the freeware binary file viewer XVI32 which can be downloaded from the following website http www chmaas handshake de delphi freeware xvi32 xvi32 htm In this document we give the correct syntax for all the built in global functions and global variables as well as the define constants We also give a description of the scripting language used The global functions and global variables are given in alphabetical order Scripting Language Commands Variables are Local or Global so are Functions Local variables functions have scope only within the script on the other hand global variables functions have scope for all
46. a separated list of arguments and prints out their values to the scripts log file or open pipes The syntax is print lt arg 1 gt lt arg 2 gt lt arg N gt where each argument can be any expression or a print function command or a newline command OPENPIPES openPipes this command is used to open a number of pipes for the script The script s output through the print command is then sent to all open pipes The syntax is openPipes lt pipes gt where the value lt pipes gt is a logical OR of all the pipes to open The pipe codes are defined as define constants CLOSEPIPES closePipes this command is used to close a number of pipes for the script The script s output through the print command is sent to all open pipes The syntax is closePipes lt pipes gt where the value lt pipes gt is a logical OR of all the pipes to open The pipe codes are defined as define constants CLEARFILE clearFile this command is used to define a new log file for the script The argument is a comma separated list of arguments as in the print command that will form the file name for the new log file for the script If a file of that name already exists it will be deleted The syntax is clearFile lt arg 1 gt lt arg 2 gt lt arg N gt where each argument is as for the print command RESET reset this command simply resets the current script to begin execution anew The syntax is reset OPENFILE openFile this command is used to defi
47. a terminal block These are power lines that can be used to supply external sensors or provide external power for the circuit itself the pinouts are shown in Table 2 Pin Pin Pin Function Pin Comments Number Name 1 DO Frequency Input Digital Digital Function 0 3 3V signal output 0 5V Input or Output signal input 2 D1 Frequency Input Digital Digital Function 0 3 3V signal output 0 5V Input or Output signal input 3 D2 Frequency Input Digital Digital Function 0 3 3V signal output 0 5V Input or Output signal input 4 D3 Frequency Input Digital Digital Function 0 3 3V signal output 0 5V Input or Output signal input 5 D4 A0 Analog Frequency Input Analog Frequency Input 0 3 6V signal can also Digital Input or Output be used for digital functions 6 D5 A1 Analog Frequency Input Analog Frequency Input 0 3 6V signal can also Digital Input or Output be used for digital functions j A2 Analog Input Analog Input 0 13 8V signal 8 A3 Analog Input Analog Input 0 13 8V signal Table 1 shows the pinouts for CON4 Pin Number Pin Name Pin Function amp Comments 1 GND Ground Reference 0V 2 VDD 3 3V rail from REG1 can supply around 50mA max for external sensors Always powered Use this to supply small sensors that consume little power VIN Input for External Voltage Source 5 5V to 7V DC 4 VDD HIGH 3 3V rail from REG2 can supply ar
48. abled or disabled in the Device Settings group box and are logged to a file called syslog txt on the memory card You can download the log file and view it by going to the Device gt Show System Log menu when the USB Data Logger is connected You can also clear the log as the default behaviour is to append new data to old data A sample few lines from the system log are shown below these are useful for troubleshooting Time Unavailable USB Data Logger Version 9 60 Global PORs 4 Local PORs 1 Time Unavailable Memory Card Detected Total Size 2 0 GB Free Size 2 0 GB Time Unavailable VM s Running 1 of 2 Time Unavailable The Following VM s Are Loaded oneScript csvScript The first line shows the firmware version and the number of power cycles that the USB Data Logger has undergone this is the Global PORs reading The Local PORs are the number of times the memory card scripts have been reset This happens when the memory card is inserted anew for example The next line shows the memory card detected including its total size and the free size Next the number of scripts loaded is shown VM s scripts as each script is a separate virtual machine and how many of those are running In this example 1 is running and 1 is paused The fourth line shows the names of the scripts that are loaded Remember that you can give your scripts any names you like to easily identify them Other system logging events are the following Th
49. achine can execute its own custom machine code but unlike a microcontroller it is implemented in software In this case the firmware on the PIC18F27J53 microcontroller implements the VM and the Windows PC host implements both the VM and the compiler for this language The source code is compiled into machine code and stored on a file on the memory card The VM engine is capable of multitasking which means more than one custom script can run at a time It also incorporates a virtual memory engine as well full details can be found on the SILICON CHIP website downloads area Jan 2011 This means that unlike a PICAXE the RAM Random Access Memory and program space available to each running script is much bigger than the few kilobytes available on the PIC itself and is cached to disk In other words only a small amount is ever present in the microcontroller s memory at any time any accesses outside of that cause a cache miss and go to disk ie to the memory card This will be explained in more detail in next month s article Since there is a lot of variation in how manufacturers of digital sensors implement their interfaces having the USB Data Logger run custom scripts allows it to read almost any type of digital sensor Even analog sensors many of which are ratiometric differ in their linear transfer function That s the main reason that the USB Data Logger implements a VM and its custom scripting language As a consequence it also
50. am for Windows OSs that can be used to change the settings of the data logger and unlock all its features Features at a glance e Large storage using an MMC SD SDHC memory card FAT file system e USB Full Speed device 12Mbps connection to PC and host PC program for Windows OSs e Digital Sensor Support 1 I2C Cnter IC 2 One Wire Dallas 3 Full Duplex Serial Port UART Universal Asynchronous Receiver Transmitter e Analog Sensor Support 12 bit ADC Voltage 5 accuracy e Analog Sensor Support frequency signal up to 192kHz e Analog Sensor Support 32 bit counters e Scripting Language allows many different sensors to be used e Low Power around 1 5mA in standby mode e Flexible Power Options 1 Battery Powered using two AAA batteries or 2 USB powered or 3 External 5 5V to 7V DC power source e NiMH batteries can be recharged using USB power or external power source trickle charge e Can connect an external voltage reference for greater than 5 accuracy on ADC inputs e Battery Protection to prevent over discharge e Real Time Clock Calendar Introduction This project is intended as a low cost and low power data logger that can collect vast amounts of information onto a memory card together with time and date information You can connect many different types of analog and digital sensors and it is even possible to connect a GPS Global Positioning System module to log space coordinates too Suppose you have
51. and point of difference from other data loggers This allows it to interface to many different sensors easily It also makes it highly configurable and this means that if you have a logging application in mind and you are in doubt whether this data logger can be used for it the answer is almost certainly In this article we guide you through the construction and installation of the Windows driver and PC software The latter is used to compile custom scripts that you can write to tell the data logger how to read a sensor and then tell it what to do with the data This means that this data logger can not only log data it can also analyse the data At the end of this article we run through a number of scenarios and give example custom scripts These are a good starting point for learning to write your own custom scripts So let s run through a few things the USB Data Logger can do If you have a weather station you can log a whole day s worth of temperatures and then compute the average or the daily maximum and minimum say in a spare time window at midnight If you have a number of digital sensors connected to the I2C bus you can send commands to read from them log their values or send commands to power them down during extended periods where no logging needs to occur the USB Data Logger itself will go to standby mode during extended periods to save power You can read from a sensor and execute code depending on the reading report
52. are option A window similar to the one shown in Fig X will appear Choose Browse my computer for driver software An open file dialog will appear and you should navigate to the directory where you unzipped the driver files using the Browse button as shown in Fig X Choose the USBMemoryCardDataLogger inf file that appears On recent Windows OS versions eg Vista and Windows 7 a security message will appear as shown in Fig X Click Install this driver software anyway Windows should then proceed to install the driver This may take a few minutes depending on your system Once complete a window should appear saying that Windows has successfully updated your driver software If the driver is installed correctly you should be able to see the USB Data Logger in Device Manager of course it needs to be connected using a USB cable and powered on under the Libusb Win32 Devices group That completes the installation of the driver Launching the PC Host Software For Windows To use the USB Data Logger with a Windows PC you use the included executable program usbdatalogger exe It is included in the zipped archive you downloaded and extracted earlier that also contains the Windows driver files You may want to create a shortcut to this file on your desktop for easy access If so right click on it and choose Send To Desktop Once that is done you can launch the program by clicking on the desktop icon easy The PC host
53. by other running scripts as opposed to global variables which can Local variables always start with a single character Global variables always start with two characters in analogy with global and local functions Once the temperature is computed and stored in the local variable T which is a 32 bit floating point value the next statement logs the result into the memory card A typical line would read The temperature is 21 4 degrees Celsius PRINT is a built in command and it takes as argument a comma separated list Each item in the list is either a constant string enclosed in quotes or an expression in this case the value of T or a special print command In this case we are using the NEWLINE print command to add a line return to the log file The last line is another built in command SLEEP and it takes a single numeric argument which is the number of seconds to suspend execution of the script for It simply puts the script to sleep for the specified period letting other scripts run The script will be awoken after this period and begin execution after the SLEEP command In this case since it is the last statement in the WHILE loop a new value will be read and logged and the process will repeat indefinitely There is another command for sending a script to sleep it is the SLEEPUNTIL command or sleepUntil if in lowercase Unlike the SLEEP command it takes an absolute time in the future as argument F
54. charging a battery in this way can take up to 15 hours Of course you can recharge the cells more quickly using an external charger too if you wish In our case we are presenting the project for use with two 900mAh NiMH batteries so we aim for a charging current of around 45mA 45 0 05 900 Thus we choose a resistor of value approximately 3 0 2 5 0 045 approx 10 The regulator can be assumed to output around 3 3 0 3 3 0V since there is a series Schottky diode and the average voltage of two NiMH cells is around 2 5V each cell will be between 1 1 and 1 4V in normal operation so we take an average Diode D2 bypasses the 10 resistor when no charging is taking place Note that if you are using non rechargeable alkaline batteries together with a power source you should not install the 10 resistor R17 In this case D2 provides reverse polarity protection against a reversed battery connection too Although the USB Data Logger is designed to be low power and can run for long periods on just two AAA batteries for very long term logging you should connect a 6V SLA battery Suitable batteries include the following a 6V SLA battery rated for say 12Ah Jaycar SB 2497 or a number of 6V SLA 1300mAh batteries wired in parallel Jaycar SB 2495 which you can recharge externally Memory Card The USB Data Logger uses a memory card MMC SD SDHC for storage They are ideal for this application because they are of large capacity
55. cheap easily acquired low power and reliable Currently capacities from 16MB up to 32GB are available A normally open NO switch inside the memory card socket CON1 is used to detect when the memory card is inserted into or removed from its socket It has a single 33k pull up resistor The memory card is powered by the 3 3V rail but the supply to it can be controlled using Q1 a 2N7000 FET Field Effect Transistor which has its drain connected to the memory card s GND connections The FET needs a substantial voltage at its gate to turn on properly this is derived using a voltage doubler circuit around diodes D3 and DS The basic doubler is formed using a 10nF green cap capacitor and D5 and is driven by the microcontroller using a square wave generated by one of its output compare peripherals at the RP13 pin pin 13 of IC1 When functioning as a doubler the IO pin pin 17 of IC1 that also controls LED1 is brought high When the signal at RP13 is close to OV the 10nF capacitor charges to close to 3 3 0 6 2 7V through D5 0 6V is the voltage drop of D5 a 1N4004 diode When the signal at RP13 goes high the capacitor is in series to effectively double the voltage at the cathode of D5 well close enough 3 3 2 7 6V In other words the signal at the cathode of D5 is a square wave of roughly double the amplitude of the signal at RP13 This square wave is smoothed via diode D3 and the 4 7uF tantalum capacitor which form a peak
56. cript is stored along with its object code on the memory card allowing the code to be later easily edited You use this window to write custom scripts that can then be compiled and sent to the USB Data Logger You can load a text file into this window too The default font size is suitable for normal reading however for those readers who have trouble reading small print you can scale the font by going to the Window menu The window below that one is the log window it gives you feedback about the current operations of the PC Host the entries are also time stamped There is a button Clear Log Window that will clear this window otherwise you can scroll up and down using the scroll bar To compile a script you enter the source and press F10 This only compiles it and if there are no syntax errors it is stored locally on the PC host In order to upload the script to the USB Data Logger you need to select a local script right click it and choose Send PC Script in the green Host Scripts window Alternative for convenience you can press F11 to compile the source AND send it to the USB Data Logger even more convenient you can send all local scripts to the USB Data Logger by pressing Shift F11 After compilation the Compile button will light green if it succeeded there were no errors although there may be warnings and red otherwise if there were syntax errors In the latter case the first error i
57. ct if 1 is not given get the minutes of the local time from the RTCC Real Time Clock Calendar otherwise if l vmTime get the minutes of the script s time Syntax getMonth 1 Effect if 1 is not given get the month of the local time from the RTCC Real Time Clock Calendar otherwise if l vmTime get the month of the script s time Syntax getPipes Effect return the currently enabled pipes The result can be a combination of the following serialPipe filePipe usbPipe fileNamePipe Syntax Effect RTCC systemLogPipe SerialInPipe getSeconds 1 g if 1 is not given get the seconds of the local time from the Real Time Clock Calendar otherwise if 1 vmTime get the seconds of the script s time Syntax getSizeUART Effect returns the current size of serial port input pipe Syntax getTotalSeconds 1 Effect if no argument is given return the total number of seconds from the default time 1 Jan 2011 00 00 00 until the local time otherwise if 1 vmTime from the default time to the script s time Syntax getTotalSecondsDiv 1 2 Effect if one argument is given return the total number of seconds from the default time 1 Jan 2011 00 00 00 until the local time divided by 150 otherwise if 2 vmTime from the default time to the script s time divided by 1 gt 0 Syntax
58. ctions and which are user defined functions the latter always start with only one character Now this particular function takes one argument which is the channel number In this case openADC 0 simply configures the AO pin as an analog input The next statement PRECISION 1 is a built in command rather than a built in global function It simply configures the number of decimal points for printing floating point values used later on to display the temperature Then the program enters its main loop where it will execute its infinite loop This is the WHILE 1 built in command that executes the block of code enclosed in its curly brackets whenever the condition is non zero as in C The next line reads T readV 0 0 25 0 028 and should be self explanatory There are built in rules for which arithmetic operators take precedence over others for eg multiplication takes precedence over addition so that 8 3 2 26 rather than 40 but you can use brackets whenever in doubt Apart from the four arithmetic operators you can also use the exponent and modulo operators note that unlike in C is used for XOR The statement simply computes the temperature T by reading the voltage at channel 0 using the built in global function readV subtracts 0 25 from the value and divides the result by 0 028 It stores the result in the local variable T Local variables are local to the current script so cannot be accessed
59. cy input Syntax readv 1 Effect return the voltage level in Volts at the analog input pin 1 assuming the default voltage dividers have been used Syntax receivedNMEAUART Effect returns 1 if a valid NMEA sentence has been received on the serial port input pipe otherwise 0 Syntax resetOneWire Effect send a reset pulse to the OneWire bus Syntax rnd 1 Effect returns a pseudo random number modulo 1 Syntax sendOneWireCommand 1 2 3 4 Effect send the command 1 with data packet of 2 bits in mode 3 and with optional 4 ms pullup to the OneWire bus Syntax sendOneWireCommandRomCode 1 2 3 4 Effect send the command 1 with data packet of 2 bits in mode 3 and with optional 4 ms pullup to the OneWire bus Uses the Rom Code Buffer As Buffer Syntax setADCSupplyRef 1 Effect set the ADC reference voltage to 1 provided it is within reasonable bounds Syntax setDay 1 2 Effect if only one argument is given set the day of the local time to 1 otherwise if 2 vmTime set the day of the script s time to 1 Syntax setHour 1 2 Effect if only one argument is given set the 24 hour time hour of the local time to 1 otherwise if 2 vmTime set the year of the script s time to 1 Syntax setIO S1 2
60. detector circuit Now when functioning as a doubler LED1 can be turned on for small periods to flash if necessary without affecting the gate voltage in any meaningful way This higher voltage is used to turn on Q1 through a 10 resistor The latter is simply there to prevent excessive currents to flow in the unlikely event that the thin insulating layer between gate and channel inside Q1 is destroyed The pull down 330k resistor simply turns off Q1 in the absence of a driving signal from the microcontroller When power is cut to the memory card the driving signal from RP13 is stopped and the IO pin simply controls the LED except that it functions as an open collector output being either low to turn on the LED or tri stated to turn the LED off The firmware automatically adjusts the drive LED1 and the RP13 output as appropriate Using this circuit the microcontroller can turn power to the memory card on or off In periods of extended idle time ie when not logging for extended periods the microcontroller will go to sleep and turn off the supply to the memory card to conserve power For short logging periods the memory card will not be turned off as the initialization sequence would take too long relative to the logging period Therefore the higher the frequency of logging the higher the power use in actual practice this will be a compromise Memory Card SPI Connection The SPI Serial Peripheral Interface peripheral of IC
61. e obtained online at the SILICON CHIP website According to the DS18B20 s datasheet the 0x33 command is used to read the sensor s ROM code So once this command executes the ROM code is stored in the globally defined buffer 0neWireBuffer We then proceed to print out the result using the PRINT command and the base built in command which prints the value of its first argument in this case the local variable A in the base given by the second argument and in a format of fixed with given by the last argument in this case 2 digits So a typical output of this custom script is as follows Connecting to One Wire Sensor Ok The ROM Code is 0x28 0xCB 0x8A 0xC2 0x02 0x00 0x00 0x7E You will notice that the last byte is the computed CRC of the other bytes the actual CRC polynomial used is x 8 x 5 x 4 1 There is a builtin global function crcOneWire that can be used to compute the CRC This can be used to check transmissions between 1 wire devices and the USB Data Logger Reading a GPS Module The USB Data Logger can connect to a GPS module using its on board UART serial port To do this there are specific built in global functions that can be used to produce the required CRC signature for the NMEA commands The module we developed the firmware with is the EM 408 GPS module from Altronics K 1131 This module has featured in a number of SILICON CHIP projects to date Its power supply requirements can be as high as 75mA at 3 3V so y
62. e are 5 Schottky diodes to go in next Unlike the resistors these need to be oriented correctly their cathodes are indicated by a grey stripe The pad on the PC board that should connect to the anode is shown on the top overlay silkscreen as an A you can also refer to the component overlay if in doubt The TO 220 regulator is next REG2 It mounts horizontally on the PC board You should bend the leads by a right angle allowing around 7mm of lead Secure it to the board with a single M3 nut and screw before soldering not after as this can unduly stress the leads Then proceed to solder in the three leads The IC sockets can now be installed If you don t have a 28 pin 0 3 socket you can use two 14 pin sockets Be certain that the IC sockets are oriented to match the component overlay with their notches in the right position This will mean the microcontroller will be inserted with the correct orientation later on Moving on you will need to install the capacitors making sure that the correct value and type is placed in the corresponding place on the PC board To do this you should refer to the component overlay Note that there are four types monolithic ceramic tantalum and electrolytic The electrolytic capacitor is polarised and must be installed with the correct orientation The negative terminal is marked on the body of the capacitor and the positive terminal is marked on the top overlay silk screen on the PC board usin
63. e entering the main loop executing some code and going to sleep until the next cycle begins again This is a good template to start a new script from Of course what you do is up to you The VM engine is multitasking so scripts are suspended after a certain amount of time if they don t voluntarily go to sleep The ability to run custom scripts from the memory card allows this USB Data Logger to interface to almost any sensor you can think of as well as do novel things like analyse the data or monitor the sensors ie take different actions on certain conditions being met In next month s final article we will run through the PC host program telling you how to compile and run custom scripts on the USB Data logger More details and examples including a Tips amp Tricks section on how to use the custom scripting language will be given as well SC BREAK OUT PANEL How the Universal USB Data Logger Works The USB Data Logger is different to most data loggers as it incorporates support for a scripting language It is supplied with its own compiler and virtual machine VM engine A virtual machine is simply put a software implementation of a real machine Implied in the term machine is processing machine ie a processor that can execute instructions to add and subtract numbers branch on a certain condition call subroutines among others An example of a well known VM is the PICAXE which runs on a PIC This virtual m
64. e script is running on the USB Data Logger the Console window will show real time output it is a serial pipe through the USB connection On the other hand if the script is running locally the Console window will show the simulated output Device Settings There are only a few settings which can be modified by the user for the USB Data Logger itself These are shown in the right hand area of the PC Host program These are as follows Time Synchronisation Enable Auto Time to allow the PC host to automatically synchronise the time with the USB Data Logger whenever it is first connected If unclicked you can still synchronise the time manually using the Time menu Note that the PC Host program checks to see when the last time was that the USB Data Logger was synchronised and also looks at the difference in time between its local time and the USB Data Logger s time It will prompt for confirmation if the times are very different Other settings that you can change are as follows You can also enable or disable the System Log Enabling the system log is useful for troubleshooting and system activity is logged to a file on the memory card but there is an overhead associated with keeping the log The last setting to enable or disable is the Undervoltage protection If enabled the USB Data Logger will go into standby mode using very little power whenever the battery voltage is below the value shown in the numeric bo
65. ed by the sensor For example if you have a temperature sensor you can monitor its value and turn on or off an external relay if the value is outside a specific range These are just some examples of what is possible If you ve ever programmed before it should be very easy to understand and write programs for the USB Data Logger the scripting language s syntax is simple and loosely based on C We now explain how the USB Data Logger is built it is a small and simple PC board and should take only a few hours to assemble If you purchase the USB Data Logger as a kit it will be supplied with a double sided PC board and all the specified components including the preprogrammed microcontroller Construction The Universal USB Data Logger is built on a double sided PC board coded 04112101 and measuring 60 x 78 mm Before commencing inspect the board for hairline cracks or unintended shorts between tracks If you are satisfied that the PC board looks ok you can proceed If you have any doubts about the connectivity of tracks you can use a DMM to check them Start the construction by soldering in the SMT Surface Mount Technology boost regulator REG1 which is a TPS61097 33DBVT in a SOT23 5 pin package You will need a fine tipped soldering iron and a steady hand This mounts on the top of the board Position it over its pads it can only go one way and secure it in position using some tape Make sure that you leave pin 5 uncovered
66. ents to form a compound statement that is true when at least one is true Operators The following operators can be used in a conditional statement or in an arithmetic expression Operator Function Example H Addition A 45 54 A then equals 99 Subtraction A 10 1 A then equals 9 K Multiplication A 2 8 A then equals 16 Division A 4 5 A then equals 0 8 ia Exponent A 2 3 A then equals 8 Modulo A 16 5 A then equals 1 Equality A 12 the result is non zero if A is equal to 12 0 otherwise a Non Equality A 12 the result is non zero if A is not equal to 12 0 otherwise gt Greater than or A gt 12 the result is non zero if A is greater than or equal to 12 0 equal to otherwise lt Less than ori A lt 12 the result is non zero if A is less than or equal to 12 0 equal to otherwise gt Greater than A gt 12 the result is non zero if A is greater than 12 0 otherwise lt Less than A lt 12 the result is non zero if A is less than 12 0 otherwise Address of This operator returns the address of a variable Size of This operator returns the size of a variable Assignment A 23 Assign the value 23 to variable A Local Variables amp Global Variables Local variables names begin with a single character followed by a letter and then any number of letters and numbers
67. erence voltage Syntax getDay 1 Effect if 1 is not given get the day of the local time from the RTCC Real Time Clock Calendar otherwise if 1 vmTime get th day of the script s time Syntax getDaysInMonthYear 1 2 Effect if no arguments are given returns the number of days in the local time s month otherwise returns the number of days in year 2 and month 1 Syntax getErroruUART Effect return the serial port input error register and then clear any error The error register can be a combination of the following constants rrorOverRunUART rrorOverFlowUART rrorUnderFlowUART Syntax getHour 1 Effect if 1 is not given get the 24 hour time hour of the local time from the RTCC Real Time Clock Calendar otherwise if 1 vmTime get th hours of the script s time Syntax getI2c 1 2 Effect reads up to 2 bytes from I2C address 1 into the I2C buffer Syntax getI2CTwoBytes 1 Effect Syntax Effect Syntax Effect yntax Ffect reads 2 bytes from I2C address 1 into the S SI2C buffer getIO 1 get the level of the digital input pin on 1 getLastRxUART returns the last received character from the serial port getLocalTime load the script s time register with the local time from the RTCC Real Time Clock Calendar Syntax getMinutes 1 Effe
68. g a sign Similarly the tantalum capacitors have their anodes indicated on their bodies by a sign The two crystals should be installed next The correct crystal must be installed in its designated place refer to the component overlay if in doubt X1 is the 20MHz crystal while X2 is the smaller 32 768kHz crystal For X2 its leads are delicate and you should take care with them While X1 mounts so that it sits flush with the top of the PC board X2 sits above the PC board pushing it in too far would over stress its thin leads The same caveat applies to Q1 the 2N7000 FET It can only go in one way and its leads should not be pushed too far as they can be overstressed too Next install the two switches One is a momentary pushbutton switch S2 while the other is a mini toggle switch S1 Refer to the component overlay for their correct positions They have three leads that need to be soldered as well as a single mounting pin which can be soldered to help anchor them in place The 8 way and 4 way horizontal terminal block headers can go in next clearly they must face outwards It remains to install the 2 way pin plug for the battery that also faces outwards While there use the corresponding 2 way header socket Altronics P 5472 Jaycar HM 3402 to solder to the 2 AAA battery holder Jaycar PH 9226 Make sure you orient the positive red wire and negative black wire correctly The positive terminal on the PC board is
69. ge three different modes are used LOW MEDIUM and HIGH frequency and the mode will be changed automatically by the firmware to suit the frequency to achieve the best accuracy For example for frequencies below about 1kHz a special LOW FREQUENCY mode is used whereas above around 12kHz a special HIGH FREQUENCY mode is used instead Reading a Counter Input Reading a 32 bit counter value is just as easy as logging a frequency input In this case simply replace the openFrequency 0 statement by either a openRisingCounter or openFallingCounter statement selecting to increment the count on a rising or falling edge and replace the readFrequency 0 statement by a readCounter 0 statement of course you should change the PRINT statement to suit your needs Note that for counters the value is cleared set to 0 whenever it is opened So the counter can be reopened to clear it Reading an I2C Temperature Sensor In this section we cover how to read from a digital temperature sensor using the I2C bus For this example we are going to use the Analog Devices AD7414 temperature sensor It is a 10 bit temperature to digital converter using the I2C bus The one we are using comes in a SOT 23 6 pin package Two pins are for the supply voltage which is 3 3V so can be powered directly by the USB Data Logger There are two pins AS and ALERT which are input and outputs respectively The AS input can be used to choo
70. he machine code is programmed into the USB Data Logger s non volatile memory Those images are then executed by the microcontroller using a virtual machine This allows very complex arithmetic expressions to be computed and logged and makes this project a very powerful data logger We will explain how to use the scripting language in an upcoming article as we ve run out of room this month Stay tuned SC Universal USB Data Logger Part 2 BY Mauro Grassi In last month s first part we described the circuit of the Universal USB Data Logger and some of its features In this month s article we give the full construction details explain how to install the Windows driver and software and outline how the data logger is used As mentioned the main feature of this USB Data Logger is its Scripting Language which makes it very versatile this allows it to interface to many different sensors easily Note Although we have quoted the standby current consumption at around 1 5mA this only applies when the USB Data Logger is being powered from the two AAA cells When using either USB power or an external power source the standby current is around 12mA due to the higher consumption of the linear regulator The assumption is that when using either USB or external power a bigger capacity power source is used so the extra consumption is not an issue Introduction The USB Data Logger supports a custom scripting language which is its main feature
71. his has the effect of speeding up time for the simulation of a script This is useful to simulate custom scripts with very long logging periods File Transfer Server In normal operation you will manually enter the source code for a script in the editor window Then press F10 to compile the script You can select whether the code is optimized or not by clicking the Optimize Code option This has the effect of improving the output of the compiler by removing some redundant instructions the compiler implements a simple form of copy propagation that can however result in a substantial saving in both program space and speed Assuming the script compiled OK it will be added to the local scripts in the Host Scripts window in green Then left clicking on it once and right clicking it will allow you to send it to the USB Data Logger Choose Send PC Script and if all is ok the script will appear in the Device Scripts window see Figs A to B Print Functions There are a number of print functions that can be used with the builtin print command the most common are shown in Table 1 Refer to the SILICON CHIP website for full details Among the functions that can be used with the PRINT command are those for displaying the time the duration since the USB Data Logger was started since its time was last synchronised etc The Hardware Connections For frequency or counter inputs you must make sure the signal is within 0 5V o
72. igured to generate an interrupt when the output of the comparator goes from low to high this happens when S2 is pressed When this happens a timer is started that measures how long S2 is held down for The USB Data Logger recognises both a short press less than a second and a long press more than 1 5 seconds Once the key press is registered the timer is shut down to save power and the firmware rearms the comparator interrupt after a hold off delay S2 can be used to start and stop the data logging and for other functions when the USB Data Logger is connected to a PC We will describe the user operation in more detail in next month s article LED Indicator The USB Data Logger has a single blue 3mm LED that is used to give feedback on the current mode of operation in the absence of a USB connection to a PC The blue LED has a current limiting 470 resistor and is driven using a single general purpose IO pin of the microcontroller RC6 In next month s article we will cover what the LED indicates Most of the time the LED is off to save power Extensive Sensor Support This data logger can read many different types of sensors that s why we are calling it a Universal USB Data Logger There are eight pins to connect external sensors and they are accessed through CON4 which is a terminal block The pin outs are shown in Table 1 be sure to check the comments for each pin There are an additional four pins that make up CON3 also
73. in We ve selected the UART using the define constant oenWireUsingUART as the argument The second argument selects the digital pin number in this case DO for the physical connection In the case that the one wire bus is implemented using a UART the two relevant pins are the selected pin and the next one so if the second argument is 3 the relevant two pins are D3 and D4 Consequently the valid arguments when using the UART mode are 0 to 4 while if using the general IO mode you can select 0 to 5 After that command executes the one wire bus is opened Then the script enters the main loop where it first tries to reset the one wire bus using the built in global function resetOneWire This resets all devices on the one wire bus by bringing it low for a short period This command returns a non zero value if it succeds and zero otherwise It would return 0 if for example there was no sensor connected so it can be used to not only reset the one wire bus but also to detect sensors on it If the result is 0 we simply print an error message and retry again in 3 seconds If the reset succeeds we send a one wire command numbered 0x33 hexadecimal using the sendoneWireCommand 0x33 64 oneWireRead 0 built in global function The command code is written to the bus and then 64 bits are read from the sensor and stored in the global variable oneWireBuffer Full details of the meaning of the arguments to all global builtin functions can b
74. in some cases you will want to name the script yourself or cause the log file to be created each time the script starts rather than data being appended each time There are two builtin commands for doing this called openFile and clearFile The command clearFile is like the print command in that it takes as argument a comma separated list for eg clearFile myLogFile txt What it does is create a new log file with the specified name This command should be at the start of the custom script and will cause the file with name myLogFile txt to be created each time this command is run It also sets it as the log file for this script so subsequent output will go to this file This has the effect of clearing the log each time the command is executed So restarting the script will erase the log file Similarly the command openFile myLogFile txt simply sets the file myLogFile txt as the script s log file but unlike the clearFile command it does not clear the log but subsequent logging is appended to the file that s the main difference between the clearFile and openFile commands Note that you can also use non constant strings as arguments to these two commands Note that in the case above the file name will depend on the value of the local variable A So if A is 0 the log file name will be myLog0 txt Reading a 1 wire Dallas Temperature Sensor In this example we are going to give the code for reading from a D
75. ing an internal low drop out regulator This regulator needs a decoupling capacitor on the VDDCORE VCAP pin pin 6 of IC1 here we use a 10uF tantalum capacitor There is also a 100nF monolithic decoupling capacitor on the supply rail close to the microcontroller The 3 3V rail is derived using a low power synchronous boost regulator IC the TPS61097 33 from Texas Instruments REG1 This switchmode IC can convert an input voltage between 0 9V and 3 3V into a regulated 3 3V rail that can supply up to 100mA to the circuit It uses a minimum of external components just two capacitors and one inductor In our case we use a 100uH RF choke for the inductor L1 and a 22uF tantalum capacitor amp a 220uF low ESR electrolytic for bypassing It comes in a space saving SOT 23 5 pin SMD Surface Mount Device package that is however not difficult to solder by hand We use tantalum capacitors for their small size and high capacitance values This switchmode regulator is ideal in this application because of its superior efficiency over linear regulators and allows the circuit to be powered from just two AAA cells This has two main advantages cells are expensive so using two rather than three decreases the cost secondly using two AAA cells allows them to be trickle charged from a 3 3V rail since their voltage will not exceed about 2 8V when fully charged Power can be supplied in three ways using two AAA batteries there is a two pin header CONS to
76. ing point variable The default is 0 the syntax is precision lt num gt where lt num gt is the number of decimal places NEWLINE newline used as an argument to the PRINT print command to print a newline PF pf print function command is used as an argument to the PRINT print command to print a specific type of data The syntax is pf lt function gt where function is one of a number of defined constants IF if used to conditionally execute a block of code The syntax is if lt conditional gt lt block gt The block of code lt block gt is executed only if lt conditional gt is non zero If lt block gt consists of a single statement the curly brackets can be omitted but a semi colon must terminate the statement ELSE else can be used with the IF if command to conditionally execute two blocks of code The syntax is if lt conditional gt lt block 1 gt else lt block 2 gt The block of code lt block 1 gt is executed only if lt conditional gt is non zero otherwise lt block 2 gt is executed If lt block 1 gt consists of a single statement the curly brackets can be omitted same applies for block 2 but a semi colon must terminate the statement HEADER Sheader keyword used to define the header of a script The syntax is header lt name gt lt header code gt Every script must have a header defined by the header keyword but the header code body can be empty PRINT print this command takes a comm
77. is makes it cheaper than it would otherwise be using a freely available Microchip software library It is possible to use two or more memory cards with the same USB Data Logger hardware In that case the setttings stored on the memory card take precedence over the ones stored in FLASH The settings are automatically synchronised as needed when the memory card is first detected Since the memory card can be pulled out of its socket at any time we do not recommend this that means that a write to the memory card can be interrupted and fail The firmware uses check sums to increase the likelihood that the data is OK If the settings on the memory card give a bad check sum the settings on the onboard flash memory are used instead This adds a layer of redundancy to the settings In any case you can save and restore the settings to your PC using the PC Host program as well as restore the defaults These options are for both the PC Host program itself in the Host menu and for the USB Data Logger itself in the Device menu Overview of the PC Host Program It will take some time to become accustomed to using the PC host program but it has been designed to be easy to use As you can see in Fig 1 there are a number of windows menus and check boxes The largest black window on the left is the editor window You can load and save files from the editor to the file system using the File menu top left Note that the source code for each s
78. ise 0 local local local local local time time time time time returns the arc sine of 1 if 1 is between 1 and 1 otherwise 0 Effect fill the rom code buffer with the contents of the one wire buffer at offset 1 Syntax copyRomCodeBuf ferToOneWireBuf fer 1 Effect copy the contents of the rom code buffer to the one wire buffer at offset 1 Syntax cos 1 Effect returns the cosine of the angle in radians Syntax decimalToBcd 1 Effect returns the BCD equivalent of decimal value 1 Syntax exp 1 Effect returns the value of to the power of 1 where e is the natural constant Syntax flashLED 1 Effect flash the onboard LED LED3 on 1 times system limited Syntax flashLEDDuration 1 2 Effect flash the onboard LED LED3 on 1 times for 2 ms each time system limited Syntax frac 1 Effect returns the fractional part of 1 Syntax gced 1 2 Effect returns the greatest common divisor of 1 and 2 Syntax getADCRef Effect compute the ADC reference voltage by measuring in real time the internal band gap reference voltage Syntax getADCRefIfVBGVEquals 1 Effect return the ADC reference voltage if the voltage of the band gap reference VBG is 1 Syntax getADCSupplyRef Effect get the ADC ref
79. l time clock calendar increments without firmware intervention to provide accurate timekeeping There are no switches to set the time and date instead the time is set using a Windows PC and the USB connection The time and date will be automatically synchronised with the PC once the host program is used to connect to the USB Data Logger Battery Protection The secondary oscillator is only switched off when the USB Data Logger goes into deep sleep mode This happens only if the firmware detects that the batteries are in a state of dangerously low charge and in that case the core is shut down and goes into deep sleep to prevent them from discharging any further which could damage them In this special mode the contents of the SRAM are lost and the timekeeping will fail This is done to minimise any further drain of the batteries The USB Data Logger will require a reset how to do this is explained in next month s article This should not happen in normal operation however Note that when logging the microcontroller spends most of its time sleeping thus reducing the power consumption until the next logging timeout occurs While sleeping the RTCC still operates to maintain accurate timekeeping Flexible Power Options The entire circuit of the USB Data Logger is powered from a 3 3V rail This includes the microcontroller and the memory card While the microcontroller is powered by 3 3V its core runs from a 2 5V rail derived us
80. llows you to compile custom scripts and send them to the USB Data Logger It also allows you to simulate the running of a script locally without needing the USB Data Logger to be powered on note that some hardware features of the USB Data Logger are not emulated locally For example reading an analog input will always read 0 locally Most of the features of the VM engine are simulated accurately though including the use of virtual memory and the logging output It s possible to do something in the PC host simulator that can t be done on the device that is speed up the time This allows you to simulate logging scripts with very long periods faster than in realtime The time scaling factor can be set and the Scale Time option can be enabled by clicking on the checkbox The PC Host program also allows you to access the entire file system on the memory card and transfer files to and from the device to the PC This is a convenient way of retrieving logs since the memory card need not be removed there is a speed penalty though compared to using a memory card reader with your PC Persistent Settings Both the PC Host program and the USB Data Logger itself remember their last settings Moreover the settings of the USB Data Logger are stored in two places on the memory card and in the onboard FLASH program memory of the microcontroller The latter is used to implement a virtual EEPROM since the PIC18F27J53 does not have onboard EEPROM th
81. mFileName Value 11 0x0B Effect print function constant displays the script s log s file name Syntax vmTime Value hy ORLA Effect print function constant displays the script s time register Syntax vmTimeDuration Value 24 0x18 Effect print function constant displays the duration since the script was last restarted Syntax vmTimeFileName Value 19 0x13 Effect print function constant displays the script s time as a string suitable for a file name Syntax vmTimeFileNameDat Value 20 0x14 Effect print function constant displays the script s date as a string suitable for a file name Syntax vmTimeFileNameNumeric Value 21 0x15 Effect print function constant displays the script s time as a numeric string suitable for a file name Syntax vmTimeFileNameNumericDate Value 22 0x16 Effect print function constant displays the script s date as a numeric string suitable for a file name Syntax vmTimeFuture Value 9 0x09 Effect print function constant displays the next matching time argument in the future corresponding to the script s time register Syntax vmTimelfSet Value 18 0x12 Effect print function constant displays the script s time register if it is set Syntax vmTimeOrDuration Value 23 Ox17 Effect print function constant displays the script s time if it is set or the duration since the script was last restarted Built
82. mK 5 T w a H FW yntax Ffect pauseVM 1 pause if 1 amp pause 0 or unpause if 1 amp noPause 0 the ID 1 primeProduct 1 returns the product of the prime divisors of 1 putI2c 1 2 writes up to 2 bytes to I2C address 1 from the I2C buffer putI2cByte 1 2 writes byte 2 to I2C address 1 putI2CTwoBytes 1 2 3 writes bytes 2 and 3 to 12C address 1 putUART 1 writes a character to the serial port readADC 1 return the voltage level in Volts at the input to the microcontroller corresponding to analog input pin 1 Syntax Effect regulator Fw yntax ffe Q qT FLW me 2 T w x FN mK 5 C w a readADCP return the voltage level in Volts at the input to REG1 the boost readComparator get the output state of the internal comparator connected to S2 readCounter 1 return the value of the counter on the pin 1 counter input readEE 1 return the value of the byte of general non volatile memory at address 1 EEPROM emulated on memory card Syntax readEEFloat 1 Effect return the 32 bit floating point value of general non volatile memory at address 1 EEPROM emulated on memory card Syntax readFrequency 1 Effect return the frequency of the signal on the pin 1 frequen
83. modes nanowatt XLP series its serial peripherals SPI I2C UART DMA Direct Memory Access support for the SPI peripheral up to 10 output compare capture peripherals one of three comparators the 12bit ADC system with internal band gap reference the comparator voltage reference module and the very useful PPS Peripheral Pin Select feature Details of these are discussed below Primary and Secondary Oscillators The microcontroller uses two oscillators the primary oscillator uses a 20MHz crystal X1 and associated 33pF ceramic loading capacitors that provides the main system clock The oscillator output is divided by 5 and multiplied by 12 using an internal PLL stage to derive the single 48MHz clock used by the USB peripheral USB Full speed device 12Mbps and the core The core runs at 12MIPs which is its highest rated speed The firmware implements a full speed USB device and connects to a PC using a USB cable via CON2 a USB Type B connector We provide a driver to use with Windows OSs as well as instructions on how to install it in a later article The USB Data Logger has its own VID Vendor ID and PID Product ID pair sub licenced by Microchip Real Time Clock And Calendar The secondary oscillator uses a 32 768kHz watch crystal X2 and two 12pF ceramic loading capacitors This oscillator is almost always powered even when the microcontroller is sleeping and is used for timekeeping by the RTCC peripheral inside IC1 This rea
84. n DO D3 and 0 3 6V on D4 DS If your signal is not within these limits the easiest way to interface it to the USB Data Logger is to use a common emitter buffer stage using a single transistor For I2C sensors they must connect to D0 SCL clock and D1 SDA data For One Wire sensors they can connect to any of the six digital pins D0 D5 you must configure the correct pin number in the script The same applies to the serial port you normally specify the Transmit and Receive pin numbers the baudrate and the mode Note that the serial port supports high baud rates up to 0 5Mbps The User Interface Long Presses and Short Presses As previously mentioned the USB Data Logger accepts both a short press and a long press on S2 the pushbutton switch on the left in the normal orientation Standby Power In normal standby mode during extended periods without logging activity the current drawn by the USB Data Logger is around 560uA 850uA In full sleep in battery protection mode the current draw is around 560uA we did quote the standby power conservatively at 1 5mA in Part 1 Subsequent testing together with firmware improvements have allowed us to bring this much lower The special power saving features of the PIC18F27J53 microcontroller allowing most peripherals power to be switched on and off greatly aids in the power saving This is the current drawn by the USB Data Logger itself and does not take into account the power drawn
85. n error on the serial port errorUnderFlowUART 4 0x04 there was a receive Rx serial port input pipe underflow error execModeNoRestart 1 0x01 use the no restart execution mode no restart on HALT fileNamePipe 16 0x10 a pipe used to set the file name for the script s log file filePipe 16384 0x4000 the log file pipe for the script Syntax Value Effect GPRMCNumBytesToMatch 32 0x20 number of bytes output by the automatic match for GPS GPRMC NMEA sentences gt Syntax Value Effect used to determine when a match occurs the S Snmea outputPtr will be this number to indicate a good match GPSDecodingUART 64 0x40 enable automatic NMEA sentence decoding on the serial port input GPS GPRMC sentence decoding Syntax Value Ef E fect Syntax Value Ef E fect Syntax Value Ef E fect highIO 1 0x01 a high level on the IO pin inputIO 1 0x01 indicates the IO pin is to be opened as an input interruptRxUART 8 0x08 nables interrupt receive on the serial port system limited amp not currently implemented Syntax Value Ef E fect Syntax Value Ef E schema fect Syntax Value Ef E fect Syntax Value Ef E fect lowIO 0 0x00 a low level on the IO pin matchUARTString 26 OxlA print function constant displays the contents of the NMEA string
86. n the source will be highlighted and the line and column number as well as information about the error will be displayed in the log window This makes it easy to correct the error and retry Note that there is a handy help window in grey on the right which lists all the defined constants and global functions Each global function is listed with a number in parentheses indicating the number of arguments that the global function takes Global define constants are also shown together with their value To the right of the editor window there are two windows coloured red the first lists the file system on the memory card of the USB Data Logger if it is connected The red window to the right of that shows the number of scripts that are loaded in current versions of the firmware up to 8 custom scripts can be loaded and running at any time Each script s name is shown together with a one byte unique ID in hexadecimal see Fig X Script Windows Below the two red windows there are two green windows which show exactly the same information but applying to the local PC host program ie how many scripts are loaded and the local filesystem see Fig 2 While the file system on the device is relative to the root folder of the memory card the local PC Host file system is relative to the working directory of the executable program With the two file system windows for device and host the files are listed in alphabetical order and their size is shown
87. nd sends its output to all enabled pipes By default the logging file is enabled You can enable and disable the other pipes by using the openPipes and closePipes built in commands This is a more efficient way of sending the same output to more than one destination as the source does not need to be recomputed every time For example to enable logging to both the log file and the serial port you would run this command openPipes serialPipe filePipe The openPipes command simply logically ORs the argument with a word that controls the pipe output for the script Similarly the closePipes command logically ANDs the logical negation of the argument The serialPipe and filePipe values are define constants that specify respectively the serial port pipe output and the logging file output File Management Memory Mapped IO Each running script has a log file that stores all the output of the script The file is memory mapped which means that a small amount of it is stored in RAM and any accesses out of that window go to disk By default the file is appended each time a print statement is executed The default filename for the log file for each script is logXX txt where XX is the unique two digit hexadecimal id of the script For example if the script has an ID of 0x04 the default log file will be log04 txt etc The PC Host will allocate the ID to the script when it is created and sent to the USB Data Logger Now
88. nds Syntax showWeekDay Value 2 0x02 Effect display the day of the week Syntax ShowYear Value 64 0x40 Effect display the year Syntax SsystemLogPipe Value 4096 0x1000 Effect a pipe used to log entries to the system log file Syntax time Value 1 Ox01 Effect print function constant displays the local time Syntax timeDuration Value 8 0x08 Effect print function constant displays the duration since the time was last synchronised with the PC Host Syntax timeFileName Value 3 0x03 Effect print function constant displays the local time as a string suitable for a file name Syntax timeFileNameDat Value 4 0x04 Effect print function constant displays the local date as a string suitable for a file name Syntax timeFileNameNumeric Value 5 0x05 Effect print function constant displays the local time as a numeric string suitable for a file name Syntax timeFileNameNumericDate Value 6 0x06 Effect print function constant displays the local date as a numeric string suitable for a file name Syntax timelfSet Value 2 0x02 Effect print function constant displays the local time if it is set Syntax timeOrDuration Value 7 Ox0O7 Effect print function constant displays the local time if it is set or the duration since the last POR Power On Reset Syntax usbPipe Value 8192 0x2000 Effect a serial pip mulated over the USB connection to the PC Host Syntax v
89. ne a new log file for the script The argument is a comma separated list of arguments as in the print command that will form the file name for the log file for the script If a file of that name already exists it will be appended to The syntax is openFile lt arg 1 gt lt arg 2 gt lt arg N gt where each argument is as for the print command SERIAL serial this command is the same as the PRINT print command except the output is sent only to the serial port pipe for the script rather than to all open pipes NMEA nmea this command is the same as the SERIAL serial command except each character of the output is added to a running transmit CRC by repeatedly XORing the value the global variable serial TxCRC holds the CRC The CRC can then be displayed at the end of the line using the pf nmea print function to add the CRC sequence at the end of the NMEA command This is useful for interfacing to NMEA compliant devices such as a GPS module MATCHNMEA matchNMEA this command takes as argument a comma separated list consisting of a match string for matching incoming NMEA packets on the serial port On a match the input is processed The string is made up of the following commands s literal string match the literal string exactly comma marks the end and can t be matched in the string use the c option to match the comma c char match the character exactly match any character amp store it match a
90. ng a single series Schottky diode D4 As the maximum input voltage to the LM3940 is 7 5V and since the voltage drop of the Schottky diode will be around 0 3V we recommend that the input voltage at CON3 be strictly between 5 5V and 7V DC We envisage that the most common use will be to connect a 6V SLA Sealed Lead Acid battery or if mains power is available a 6V DC plugpack If you plan to use a 12V battery you will not be able to connect it directly to this input You could use a simple LM7805 or LM7806 regulator between your 12V battery and the power input to the circuit at pin 3 of CON3 if you wish Remember to provide bypass capacitors though However if you want to use the data logger in your car the easiest way is to purchase a USB charger that plugs into your car s cigarette lighter socket and provides a regulated SV In the absence of external power the two AAA batteries provide power to the boost regulator through a series Schottky diode D2 In our testing we used two AAA 900 950mAh batteries Jaycar SB 1723 Altronics S 4742C If AAA batteries and either the USB or external power source are used the voltage produced by the linear regulator REG2 will trickle charge the batteries using a simple resistor to limit the rate of charge This value of resistor is chosen so that the charging current is around 0 05 C where C is the power rating of the battery This amount is considered safe for indefinite charging and fully
91. ng over time The USB Data Logger has four analog inputs which can be used for this purpose labelled AO A3 Remember that two of the analog sensors are for low voltages 0 3 6V and two are for higher voltages 0 13 8V as explained in last month s first part They simply differ only in the voltage divider used Your analog sensor would typically have a voltage proportional to the measured quantity ie be ratio metric In this example we ll cover how to connect an Analog Devices AD22103 temperature sensor there are many different types of analog sensor and you will have to consult the datasheet for your device to configure it properly But the general method should be similar to this example The AD22103KTZ is a three pin temperature sensor in a TO 92 package Two pins are for the supply 3 3V and the third pin is the voltage output proportional to temperature and between 0 and 3 3V While many analog sensors are ratiometric they may differ in the specific linear transfer function Luckily all can be used with this data logger To connect it connect the output pin to one of the four analog input pins in this example we ll use AO as it is suitable for 0 3 6V The transfer function of the AD22103 temperature sensor is according to its datasheet given by Vo Vs 3 3 0 25 0 028T where Vo is the voltage at its output terminal Vs is the supply voltage to the sensor and T is the temperature between 0 and 100 in degrees Celsiu
92. ny character but do not store the result d n n 1 9 match up to n decimal digits and store the output x n n 1 9 match up to n hex digits and store the output o end the command string rE match a floating point number For example the command matchNMEA sGPRMC d2d2f cA d2f d3f f f d2d2d2 can be used to match NMEA sentences from a GPS module in the format GPRMC FUNCTION function this keyword is used to define a local function It can then be called from anywhere in the code to implement procedural abstraction The syntax is function lt functionname gt lt num gt lt block gt The lt functionname gt must start with a single character lt num gt holds the number of arguments to the function Each argument can then be referred to in the code block lt block gt by using the expression lt n gt where lt n gt is the nth argument passed For example 2 refers to the second argument passed DECIMAL decimal this command can be used in a comma separated argument to the print command and other commands using the same comma separated argument list to override the default printing of a number set by the precision command This command forces the display to be a decimal number with the indicated number of decimal points The syntax is decimal lt value gt lt num gt where lt value gt is the value and lt num gt is the number of decimal places BASE base this command can be used in
93. o the FILE cache of the current script Syntax SScache ram Effect base pointer to the RAM cache of the current script Syntax SScache rom Effect base pointer to the ROM cache of the current script Syntax SScache stack Effect base pointer to the STACK cache of the current script Syntax SScourse Effect 32 bit floating point value indicating course over ground heading in degrees set by the system if a GPS module is present and outputting valid GPS GPRMC NMEA sentences through the serial port Syntax SSfile Effect the memory mapped log file output for the VM Syntax SSfileName Effect the current script s log file name buffer Syntax SShardware Effect base pointer to the hardware descriptors of the current script Syntax SShardware 1I2C Effect base pointer to the hardware descriptor for the I2C port of the current script Syntax SShardware I12C busRate Effect the current bus rate in kHz of the I2C port of the current script Syntax SShardware SPI Effect base pointer to the hardware descriptor for the SPI port of the current script Syntax SShardware SPI ckdidocspin Effect the CLK DI DO and CS pin register of the SPI port of the current script Syntax SShardware SPI mode Effect the current mode of the SPI port of the current script Syntax SShardware oneWire Effect base pointer to the hardware descriptor for the oneWire port of the current script Syn
94. of 1 if 1 is between 1 and 1 addDays 1 2 if only one argument is given add 1 gt 0 days to the if 2 vmTime add 1 days to the script s time addHours 1 2 if only one argument is given add 1 gt 0 hours to the m if 2 vmTime add 1 hours to the script s time addMinutes 1 2 if onl y one argument is given add 1 gt 0 minutes to the if 2 vmTime add 1 minutes to the script s time addMonths 1 2 if only one argument is given add 1 gt 0 months to the if 2 vmTime add 1 months to the script s time addSeconds 1 2 if only one argument is given add 1 gt 0 seconds to the if 2 vmTime add 1 seconds to the script s time asin 1 close close clos closes clos close clos clos atan 1 returns the arc tangent of 1 bcdToDecimal 1 returns the decimal equivalent of the BCD value 1 calibrateADC perform an automatic real time calibration of the ADC system clearUART clears the serial port input pipe closeADC 1 closeCapture 1 pin 1 as analog input the frequency or counter input on pin 1 el2C the I2C bus e10 1 the digital IO pin 1 eOneWire clos closes clos closes the OneWire bus eSPI the SPI bus eUART the serial port copyOneWireBuf ferToRomCodeBuf fer 1 otherw
95. onth s final article we give detailed instructions on how to get an example custom script running and logging We explain in as much detail as space allows the various features of this project and try to give an idea of what can be done with it There s a lot to get through so once you ve installed the driver you will want to connect to the USB Data Logger using your PC and the supplied PC Host program Memory Card Firstly you will need an MMC SD SDHC memory card formatted with a FAT FAT32 file system You can use Windows to format the memory card You will usually want to choose the Quick Format option and should select the Restore Card Defaults in the format menu Once you ve formatted the memory card you can power down the USB Data Logger and insert the memory card and reapply power Launching the PC Host Program You can launch the PC Host Program by double clicking the icon A window should appear as shown in Fig l When the USB Data Logger is connected and powered on the PC Host will automatically detect it and connect to it In the title bar you will see the connection status and the firmware version of the USB Data Logger and the PC Host version These numbers will normally match but not necessarily Note that the USB Data Logger also incorporates a USB bootloader that can be used to easily upgrade the firmware The procedure for this is discussed below PC Host Program Menu System The supplied PC Host program a
96. or example writing SLEEPUNTIL 16 00 10 will suspend the execution of the script until just after 4pm Now suppose you wanted to display the reading as Fahrenheit as well Then you could change the PRINT statement to PRINT The temperature is T degrees Celsius or T 9 5 32 degrees Fahrenheit NEWLINE Logging the Time Another thing you can do is time stamp the logging You can do this using one of the built in print functions PF TIME PF stands for PRINT FUNCTION and is used with the built in PRINT command In this case you would replace the PRINT statement with the following PRINT PF TIME The temperature is T degrees Celsius NEWLINE Reading A Frequency Input Reading a frequency rather than a voltage is just as easy The basic script would look like the following START CUSTOM SCRIPT HEADER myFrequencySensorHeader i SCRIPT myFrequencySensorScript Basic Script Showing How To Read and Log a Frequency Input by Mauro Grassi openFrequency 0 PRECISION 3 WHILE 1 i PRINT The Frequency is readFrequency 0 Hz newline SLEEP 5 END CUSTOM SCRIPT In this case after initalizing the frequency input and setting the PRINT PRECISION to 3 decimal places the main loop begins executing and logging the frequency on that pin in Hz every 5 seconds Note that the frequency can be anywhere between 0 1Hz and 192kHz To cover this wide ran
97. ou will need to provide either USB power or an external power source to use it effectively using two AAA cells will just not be enough as the boost regulator can only supply 100mA and the microcontroller and memory card can use more than 25mA at full speed NMEA Sentence Decoding There is some built in support for decoding a number of NMEA sentences including GPSS GGA and RMC Once the GPS module has been configured and this is as easy as configuring a serial port you simply select the baud rate the Transmit and Receive pins and the mode the script will listen for GPS data from the module You can then log the location using the PF print function commands together with the PRINT command Producing a CSV file Producing a CSV Comma Separated Values file for importing into a spreadsheet is easy Simply use the PRINT command For example the following custom script produces two columns in a CSV file format of a linear function the result of importing this log file into Open Office Calc is shown in Fig X You can then easily graph the data that was logged START CUSTOM SCRIPT header csvScript j empty header script csvScript openFile myCSVFile csv This script shows how it is possible to produce a CSV file for importing into a common spreadsheet program like Exel or Open Office Calc by Mauro Grassi Configure the ADC input openADC 0 NUM is a local variable that keeps track of how many readings
98. ound 250mA max as long as either USB power or external power is present Use this to supply more power hungry sensors Table 2 shows the pinouts of CON3 Analog Sensors The simplest sensors output a voltage proportional to the quantity they measure For example a ratiometric temperature sensor would indicate the temperature by a varying output voltage that is proportional to the ambient temperature Other sensors such as accelerometers can indicate acceleration on an axis by a varying voltage too Up to four analog sensors using voltage as the dependent variable can be used There are two different types of analog inputs which form two pairs AO and Al form one low voltage pair while A2 and A3 form a higher voltage pair They only differ in the voltage divider ratio used For analog sensors with outputs between OV and 13 8V you should use analog inputs A2 and A3 pins 7 and 8 of CON4 This is because each of these analog inputs have a voltage divider formed by 15k and 4 7k resistors and are bypassed by a 100nF monolithic capacitor Since the maximum voltage that the microcontroller can digitize is around 3 3V this gives the maximum voltage of 13 8V 13 8 3 3 4700 19700 On the other hand analog inputs AO and A1 pins 5 and 6 of CON4 use a volage divider formed by 470 and 4 7k resistors and are also bypassed by a 100nF monolithic capacitor Therefore these two inputs can accept voltages in the range
99. qrt SA newline print The sine is sin SA newline print The cosine is cos SA newline print The tangent is tan SA newline print e to the power of A 100 is exp SA 100 newline print The natural log is ln SA newline print The log base 10 is log10 A newline print The arcosine of SA 100 is acos A 100 newline print The arcsine of SA 100 is asin A 100 newline print The arctangent of A 100 is atan A 100 newline SA SA 1 END CUSTOM SCRIPT Typical output would be The argument SA is 63 0000 Absolute Value is 63 0000 The square root is 7 9373 The integer part of the sqrt is 7 0000 The fractional part of the sqrt is 0 9373 The sine is 0 1674 The cosine is 0 9859 The tangent rS 0 1697 e to the power of A 100 is 1 8776 The natural log is 4 1431 The log base 10 is 1 7993 The arcosine of SA 100 is 0 8892 The arcsine of A 100 is 0 6816 The arctangent of A 100 is 0 5622 The argument SA is 64 0000 Absolute Value is 64 0000 The square root is 8 0000 The integer part of the sqrt is 8 0000 The fractional part of the sqrt is 0 0000 The sine is 0 9200 The cosine is 0 3919 The tangent is 2 3479 e to the power of A 100 is 1 8965 The natural log is 4 1589 The log base 10 is 1 8062 The arcosine of SA 100 is 0 8763 The arcsine of A 100 is 0 6945 The arctangent of A 100 is 0 5693 The argument SA is 65 0000 Absolute Value is
100. r scripts are running or not you can press S2 short press The feedback will be as follows 1 flash means there are scripts running and logging 3 flashes means there are no scripts running In order to stop logging and interrupt all scripts you can press S2 long press The LED will flash 3 times to indicate that the scripts are now paused In order to restart them you press S2 long press again to get 1 flash from the LED to indicate running mode The USB Data Logger will automatically go into standby if there are no scripts loaded or they are all paused USB Bootloader for Firmware Upgrades Note we recommend using the USB connection power while performing a firmware update Ideally the PC Host would be a laptop with battery backup In any case the whole process takes less than two minutes and is designed to be robust As mentioned the USB Data Logger incorporates a USB bootloader that can be used to update the firmware to add new features or fix any bugs A screen grab of the bootloader is shown in Fig X When powered off the USB Data Logger can be brought into bootloader mode by holding S2 pressed while applying power Launching the PC Host program will then result in the bootloader interface instead of the normal interface You can also enter the USB bootloader through the About menu item choose the About gt Enter USB Bootloader submenu While in bootloader mode the blue LED LED3 will flash periodically
101. rHeader SCRIPT myFrequencySensorScript Basic Script Showing How To Read and Log a Frequency Input by Mauro Grassi openFrequency 0 PRECISION 3 WHILE 1 PRINT The Frequency is readFrequency 0 Hz newline SLEEP 5 END CUSTOM SCRIPT Typical Output of the above script would be he Frequency is 0 000 Hz he Frequency is 3012 048 Hz he Frequency is 3012 048 Hz he Frequency is 5319 149 Hz he Frequency is 0 000 Hz he Frequency is 180 044 Hz he Frequency is 180 044 Hz he Frequency is 180 044 Hz he Frequency is 120 029 Hz he Frequency is 120 029 Hz he Frequency is 2 642 Hz The Frequency is 2 642 Hz The Frequency is 3 394 Hz The Frequency is 7 519 Hz The Frequency is 7 519 Hz he Frequency is 7 519 Hz he Frequency is 4504 505 Hz he Frequency is 4504 505 Hz Reading an I2C sensor START CUSTOM SCRIPT header myI2CHeader Basic Script Showing How To Read and Log a Temperature from an AD7414 digital I2C sensor by Mauro Grassi Define a Constant which is the sensor s I2C Address I2C_ADDRESS 0x92 script myI2CScript Open the I2C bus running at 400kHz opentT2c 400 precision 3 print The Bus Speed is S Shardware I2C busRate while 1 Write the Address Register RESULT putI2CByte I2C_ADDRESS 0 iff SRESULT Read Two Bytes
102. rent script SSvm W the accumulator of the current script S vm addressModes the adressModes of the DS and SS registers of the current script S vm execDone the execution counter register of the current script vm execID execution ID of the current script vm execLimit the execution limit register of the current script vm execMode execution mode of the current script vm execPriority the execution priority register of the current script S vm execState execution state of the current script SS vm lastError last run time error of the current script S vm lastIndirect the last indirect status register of the current script vm pipeMode za FN FW wn FW Aw Fl wn Fl wn Fw Fw Fin FAW mh S AW FAW FAW FAW Fw orn FAW ae AW Hh K nta hh 3 Mh DO qT ct o w Fh Pp ct ow Fh Pp ct ta nta ec Hh fec mh 5 h S mh S C ct ct w w w Hh 3 ct ie Ca nta nta ect nta ect nta ect nta ect nta ect ecu ect the tax ect fect th vm the vm th nabled pipes of the current script resetVector reset vector register of the current script SleepMode the N A N A SSvm base poi SSvm day SSvm hours SSvm minu SSvm mont SSvm seconds SSvm SSvm SSvm register of the script s time register register of the script s time register SSvm
103. ript is a separate file You can also transfer files update the real time clock and other functions The main feature is the custom scripting language support and we describe this next Introduction to the Scripting Language The scripting language is a light weight functional language implemented on a virtual machine that incorporates virtual memory support and a modified Harvard architecture The best way to start is to see some sample code which we present in the sections that follow The PC host program converts the source code to machine code that then executes on the USB Data Logger At this stage it s customary to give the Hello World program which looks like this START CUSTOM SCRIPT HEADER helloWorldHeader Empty header SCRIPT helloWorldScript Simple Hello World program for the USB Data Logger by Mauro Grassi PRINT Hello World NEWLINE END CUSTOM SCRIPT A script consists of a header declared by the HEADER keyword followed by its name which you can choose followed by the header s body enclosed in curly brackets The header can contain settings to alter the default behaviour of the script but in most cases its body will be empty and the defaults can be used In these examples we ve used capital letters for all the keywords to easily identify them but the compiler accepts keywords in lower case letters as well ie all lower case or all upper case letters it is a syntax error to have
104. s MIN NEWLINE SLEEP 1 END CUSTOM SCRIPT We conclude this article by listing some tips and tricks Tips amp Tricks In this section we present some tips and tricks that may not be immediately obvious Tip 1 You can omit the SMT boost regulator from the circuit and the PC board and have the USB Data Logger powered solely from the linear regulator assuming you only want to use it with a PC with USB power In this case you can omit REG1 L1 and place a link between the VDD HIGH and the 3 3V pins of CON3 simply place a link between pins 2 and 4 of CON3 This would be suitable for high school students using the USB Data Logger in a classroom as a teaching aid to writing their own custom scripts In this case the USB Data Logger is a low cost development tool Tip 2 Improving the Accuracy of the ADC System Connecting an external Voltage Reference The ADC on the 18F27J53 microcontroller operates at 12bits of resolution however the reference voltage used can have an error as high as 5 in the worst case although the typical case is much better and less than 1 we ve measured voltages within 0 5 in our testing In any case if greater accuracy is desired the way to implement it is to connect a good voltage reference to one of the analog inputs Note that the resistor divider values are within 1 and so this needs to be taken into account you could also remove them from the PC board if you wish provided the vol
105. s The Counter is up to 13 events The Counter is up to 14 events The Counter is up to 15 events The Counter is up to 16 events The Counter is up to 17 events The Counter is up to 18 events The Counter is up to 19 events The Counter is up to 20 events The Counter is up to 21 events The Counter is up to 22 events The Counter is up to 23 events The Counter is up to 24 events The Counter is up to 24 events The Counter is up to 24 events The Counter is up to 24 events The Counter is up to 24 events The Counter is up to 24 events The Counter is up to 24 events The Counter is up to 24 events The Counter is up to 24 events The Address Of amp Size Of Operators The address of operator is a unary operator that returns the address of the variable instead of its value For example if A is a local variable that was previously declared writing print The Address of A is amp A newline It is also possible to get the size of a variable in memory in Bytes by using the unary operator In this case you would write print The Size of A is A newline would print the address of the variable in local memory Built In Global Variables The following global variables are defined Syntax SST2C Effect the I2C internal buffer Syntax SSSPI Effect the SPI buffer Syntax SScache file Effect base pointer t
106. s For the sake of simplicity let s assume that Vs 3 3 so the equation becomes Vo 0 25 0 028T Rearrange this equation to get the temperature as a function of the output voltage T Vo 0 25 0 028 A custom script to read this sensor and log its value every minute would be the following START CUSTOM SCRIPT HEADER myAnalogSensorHeader i SCRIPT myAnalogSensorScript i Basic Script Showing How To Read and Log an Analog Sensor by Mauro Grassi openADC 0 PRECISION 1 WHILE 1 T readV 0 0 25 0 028 PRINT The Temperature is T degrees Celsius newline SLEEP 60 END CUSTOM SCRIPT This script is largely self explanatory we run through a few basics that are not obvious Variables which store data as 32 bit floating point numbers and Functions which execute code can be both Local and Global Local ones can only be accessed by the custom script and are defined there Globals can be accessed by all running scripts and are implemented internally Execution begins at the openADC 0 statement As mentioned each statement ends with a semi colon like in C The openADC statement is a built in global function Full details of the custom scripting language s syntax built in functions built in global variables can be downloaded from the SILICON CHIP website in the Jan 2011 downloads folder Their names always start with two characters so it s easy to tell which are built in fun
107. s are dangerously low in voltage indicating they have been discharged too much the microcontroller will take protective action going into deep sleep as previously explained Pushbutton Action Note that there is also a momentary SPDT switch S2 that is in parallel with the lower 4 7k resistor of the divider Pressing this switch brings the voltage at the AN4 pin close to GND and so the microcontroller can detect that the pushbutton is being pressed and take appropriate action The firmware uses the output of an internal comparator to sense the switch press The AN4 pin shares its function with the C1INC pin the latter is connected to the inverting input of an internal comparator of IC1 The non inverting input of the comparator is connected to an internal voltage reference generated by a separate module inside the microcontroller This voltage reference can be controlled by the firmware and is derived using an internal resistor ladder network from the supply voltage to IC1 The threshold is set at around 0 4V by the firmware meaning that any voltage at the AN4 input below this makes the output of the comparator go high Since there is a 2 1 voltage divider on this input this means that the comparator goes low when S2 is not pressed and the voltage at the input to REGI is above around 0 8V which should always be the case when the circuit is being powered Hence the output of the comparator is normally low The comparator module is conf
108. s the digital IO pin LOW when the voltage is below the minimum the maximum and minimum are constants defined in the header We define the switching thresholds allowing for hysteresis maximumVoltage 1 0 minimumVoltage 0 7 This example script also uses a local function SCRIPT monitoring Define a Local Function function writeOnoff 1 if 1 print ON print OFF Basic Script Showing How To Read and Log an Analog Sensor by Mauro Grassi Execution Begins here after the local function definitions clearFile monitoring output txt openADC A0 PRECISION 2 WHILE 1 SV readVv A0 if V lt maximumVoltage AND SV gt minimumVoltage within range so don t do anything else if V lt minimumVoltage setIO D0 lowIO else print pf timelfSet setIO DO highIO The Voltage is we use a local function call here writeOnOfft getIO D0 print newline sleep 5 END CUSTOM SCRIPT This script produces output like the following m ue ue ue ue ue ue ue ue ue ue m m m m m m m m m 25 25 25 25 25 25 25 25 25 29 Cy Grr Sy Ey Cy Cg Ey Cy E n 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011 PYPPYPVDYAPVDYPDP Dp a a a a a a a a a a
109. se one of three I2C addresses to potentially use more than one of these on the same bus the three addresses are chosen by a high low or floating pin We ve configured ours so that the I2C address is 0x92 hexadecimal The ALERT output pin will change if configured when the temperature exceeds the set limits We are not using this feature in this example but you could write your own custom script to do just this The remaining two pins are the SCL clock and SDA data lines of the I2C interface and these should connect to the digital pins DO and D1 respectively on the USB Data Logger Reading the datasheet of the AD7414 sensor tells you how to read the temperature value This particular sensor is used by reading and writing to 4 internal 8 bit registers One register at address 0 holds the MSB 8bits of the value you can just read this for a good approximation or read again the extra 2 bits for the full resolution Address 1 holds the Configuration Register which holds the extra 2 bits of temperature information as well as extra bits to control the power to the sensor you can put it in standby to save power and set the alert function mentioned above The other two registers hold the Minimum and Maximum Temperatures for the alert function which we don t use in this example The way writing works is as follows the first write sets the address of the next write For example if we want to write to the register at address 2 we fir
110. ssue the full power savings will not be made unless the minimum logging period of all executing scripts is above the threshold for going into sleep Below this threshold the microcontroller does not switch off power to certain components including the memory card because otherwise the initialization sequence for the memory card would take too long This period is set by software and is currently set at 5 seconds You will therefore get the best battery life if your logging scripts execute sleep periods of greater than or equal to this time Of course you can write your scripts so that the period changes being more frequent at certain times of the day and to revert back to a longer period in off peak times You should compare this standby current to the average current when the USB Data Logger is going at full speed with most peripherals powered and writing to a memory card The power consumption in that case can be as high as 25mA or more Note that the USB Data Logger will NOT go into standby while the PC Host program is connected Multiplexed Hardware Peripherals One of the great things about the PPS Peripheral Pin Select feature of the PIC18F27J53 microcontroller is that it allows the on board peripherals to be multiplexed to a number of different pins We take advantage of this by making most of the digital sensor pins fully configurable This not only simplifies the PC board design but it also allows the onboard peripherals
111. st write 2 and then the value to write to at address 2 Similarly for reading you first write the address then read from the sensor So to read the value at address 1 for example you first write 1 and then read from the device one byte A program to read the temperature from the AD7414 is as follows START CUSTOM SCRIPT HEADER myI2CHeader Basic Script Showing How To Read and Log a Temperature from an AD7414 digital I2C sensor by Mauro Grassi Define a Constant which is the sensor s I2C Address 12C_ADDRESS 0x92 j SCRIPT myI2CScript Open the I2C bus running at 400kHz openI2C 400 PRECISION 3 WHILE 1 Write the Address Register RESULT putl2CByte I2C_ADDRESS 0 if RESULT Read Two Bytes From The Sensor the address increments automatically RESULT getI2C 12C_ADDRESS 2 if SRESULT Compute the Temperature T 12C 0 12C 1 256 0 PRINT The Temperature is T degrees Celsius NEWLINE else PRINT Error NEWLINE SLEEP 30 END CUSTOM SCRIPT In this script we first define a constant I2C_ADDRESS in the header it can also be defined in the script We then use it in all places of the code that take the I2C address of the sensor as an argument This is a good thing to do since if we later want to change the I2C address we simply need to change one value the 0x92 rather than all places where it is used Define constants always star
112. sy access You can either glue it to the top piece or screw it to the top piece but we ve left it unattached for our prototype The two pieces of the case are held in place using an additional four screws also supplied with the case Of these two are 20mm long and are used for the two top holes in the normal orientation with the memory card at top while the rest are 9mm long and are used for the two bottom holes These four screws mount through the bottom of the bottom piece upwards the two bottom holes are not normally visible on the bottom of the bottom piece of the case but they can be accessed by opening the battery compartment That completes the construction of the USB Data Logger and you can proceed to installing the PC software to use with it Installing the Windows Driver and Software The USB Data Logger requires that a driver be installed on your Windows PC for it to work with your PC and the supplied PC host program The installation of the driver is easy and only needs to be done once In this section we give a step by step guide on how to do this as follows After the driver installation we cover how to install the Windows software Assuming you have followed the construction instructions you should now have a fully operational USB Data Logger You will need a Type A to Type B USB Full Speed cable A suitable single USB cable can be purchased from Jaycar or Altronics Jaycar WC 7700 Altronics P 1911A In any
113. t address 1 if 2 is between 0 and 65535 otherwise 0 Syntax sumSquares 1 2 Effect returns the sum of the squares of 2 numbers starting at address 1 if 2 is between 0 and 65535 otherwise 0 Syntax sysRead 1 Effect return the value of the byte of system memory at address 1 Syntax sysReadFloat 1 Syntax w Effect wri memory at addre Syntax w Effect wri the SPI bus Syntax w Effect wri the value read Quick Templates Effect return the 32 bit floating point value of system memory at address 1 Syntax sysWrite 1 2 Effect write the byte 2 to system memory address 1 Syntax CQsysWriteFloat 1 2 Effect write the 32 bit floating point value 2 to system memory address 1 Syntax tan 1 Effect returns the tangent of the angle in radians Syntax toggleIO 1 Effect toggle the level of the IO pin 1 Syntax writeEE 1 2 Effect write the byte 2 to general non volatile memory at address 1 EEPROM emulated on memory card T riteEEFloat 1 2 te the 32 bit floating point value 2 to general non volatile ss 1 EEPROM emulated on memory card T riteSPI 1 te 1 to the SPI bus simultaneously return the value read from riteSPINoCS 1 te 1 to the SPI bus without asserting CS simultaneously return from the SPI bus Example Scripts Follo
114. t to switch an IO pin to high or low accordingly you could use the code segment IF V gt VMIN AND V lt VMAX setlO 2 highIO j ELSE j In the same way that setIO sets the state of an output pin the getIO function reads the digital input For example the following function toggles an IO pin setlO 2 lowl0 setlO 2 getlO 2 where is the unary NOT operator like in C Built In Maths Functions There are a number of builtin maths functions which substantially speed up calculations these could be implemented in a custom script but they would be much slower than the builtin functions due to the substantial overhead of implementing the virtual machine Trigonometric exponential and logarithm square root and power functions are implemented as well as some built in functions for quickly adding up tables of numbers One such function is the sum builtin function which can be used to take averages and is used in the example below Computing Averages Monitoring Minimum and Maximum Values It is possible to keep a running average for a variable and to display the averaged value To do this we need to store the last N readings and then average them The storage window is circular so we forget old readings as we add new ones only keeping the last N readings In the process it is also possible to keep track of the minimum and maximum values A custom script to accomplish this is shown below
115. t with a character which is supposed to be reminiscent of the define preprocessor directive in C Note that these define constants can be redefined but the compiler will warn you if this happens We first open the I2C bus and declare it to run at 400kHz using the built in global function openI2C We then set the precision to 3 decimal places and enter the main loop We declare a local variable called RESULT which takes the value returned by the built in global function putI2CByte The latter takes two arguments The first is the I2C address the second is the single byte to write to the I2C bus In this case we simply write 0 to the sensor to set the address 0 3 to read from In this case we are interested in reading addresses 0 and 1 so we write 0 The putl2CByte function returns a value of 1 if the command succeeded or 0 otherwise For example if there is no sensor connected the function will fail We check for this using the built in command IF ELSE which executes the first block of code if the condition evaluates to non zero or the last command block otherwise If the function returns 0 it logs an ERROR message and goes to sleep for 30 seconds before retrying Otherwise we attempt to read from the sensor using the built in global function getI2C This function takes two arguments the first is the address and the second is the number of bytes to read Note that the address register inside the sensor
116. tage reference s output is within 0 3 3V In this example we are using an LM336 2 5 voltage reference diode whose output is nominally 2 5V with an accuracy as good as 2 there is an LM336B version with better accuracy at 1 Now the way to use the voltage reference is as follows START CUSTOM SCRIPT header voltageReferenceScript Define the Voltage Reference s nominal voltage we are using an LM336 2 5 voltageReferenceNominal 2 5 script voltageReferenceScript an example custom script showing how to use an external voltage reference to improve the accuracy of the ADC conversions by Mauro Grassi Assume the LM336 2 5 voltage reference is connected to AO and the relevant voltage to convert is connected to Al openADC 0 openADC 1 WHILE 1 First read the reference ADC voltage at the input of the ADC pin REFERENCE readADC 0 Read the voltage on the Al pin the readV function unlike the readADC function takes into account the voltage dividers on the analog input pins V readV 1 PRINT The voltage at A1 is V NEWLINE Compute the correction factor IF SREFERENCE gt 0 K voltageReferenceNominal REFERENCE ELSE K 1 0 PRINT The voltage at Al with correction for the voltage reference is V K NEWLINE SLEEP 3 END CUSTOM SCRIPT Tip 3 There s a tip relating to installing the driver The USB Data Logger will go into standby and
117. tax SShardware oneWire mod Effect the current mode of the oneWire port of the current script Syntax SShardware oneWireSerial Effect base pointer to the hardware descriptor for the serial port of oneWire port of the current script Syntax SShardware oneWireSerial baudRate Effect the baud rate divided by 10 of the serial port of the oneWire port of current script Syntax SShardware oneWireSerial mode Effect the current mode of the serial port of the oneWire port of the current script Syntax Effect SShardware oneWireSerial txrxpin the Tx and Rx pin register of the serial port of the oneWire port of current script Syntax SShardware serial Effect base pointer to the hardware descriptor for the serial port of the current script Syntax SShardware serial baudRate Effect the baud rate divided by 10 of the serial port of the current script Syntax SShardware serial mode Effect the current mode of the serial port of the current script Syntax SShardware serial txrxpin Effect the Tx and Rx pin register of the serial port of the current script Syntax SSindirect Effect indirect memory access to W Syntax SS latitude Effect 32 bit floating point value indicating latitude in degrees lt 0 indicates South gt 0 indicates North set by the system if a GPS module is present and outputting valid GPS GPRMC NMEA sentences through the serial port Syntax SSlongitude
118. ter two are connected transposed to the DO Data Out and DI Data In lines respectively of the memory card These lines are used to transmit and receive data in conjunction with the clock line SCK which is generated by the microcontroller The SPI bus runs at 12MHz in this application which is the fastest that the microcontroller will allow The bar CS line is pulled high by a 33k resistor to disable the memory card by default and the data output line from the memory card is also pulled high by a 33k resistor Sensing the Supply Voltage The microcontroller monitors the supply voltage to the boost regulator REG1 using an ADC Analog Digital Converter input AN4 at pin 7 of IC1 The microcontroller can convert the analog voltage at this pin to a 12 bit number When powered using two AAA batteries this voltage will be at most around 2 7V since the maximum cell voltage is around 1 4V per cell and there is a Schottky diode in series with the positive battery terminal On the other hand when power is provided to REG2 either through the USB or externally the voltage at this point will be close to 3V since the output of REG2 is around 3 3V and there is also a Schottky diode in series with its output Now the voltage at this point passes through a voltage divider formed from two 4 7k resistors and is bypassed using a 100nF monolithic capacitor The microcontroller monitors the supply voltage regularly In the case that the batterie
119. the character to the log file for this script print char C continue toggle the digital output togglelIO D0 END CUSTOM SCRIPT Using the serial Port As output The following script shows how to use the serial port as an output pipe It also shows how to connect to a NMEA device for eg a GPS module using the built in commands for NMEA sentences The USB Data Logger can automatically decode GPSS GPRMC NMEA sentences from GPS modules such as the EM408 available from Altronics There is also software support for matching arbitrary NMEA sentences and parsing the information contained in them START CUSTOM SCRIPT header simpleGPS This script shows how to use the UART to connect to a GPS module such as the EM408 from Altronics by Mauro Grassi The USB Data Logger can automatically decode GPSS GPRMC NMEA sentences but other NMEA sentences can be decoded as well script simpleGPSs Create A new Log File for this script from scratch GPSDecoder txt clearFile GPSDecoder txt Initialise the UART pin DO is Tx pin Dl is Rx Baudrate 4800 bps is the default for the GPS module the special GPS decoding mode is enabled by using the define constant in the mode definition when opening the serial port GPSDecodingUART openUART GPSDecodingUART noRxInvUART noTxInvUART 4800 D0 D1
120. tings will be lost so it is advisable to save the settings before hand using the PC Host program s Device gt Save Settings option Upgrading the bootloader itself Using the Serial Boot Loader The USB Data Logger incorporates a second bootloader that works using the serial port on pins D5 Tx and D4 Rx It works using 115200 bps no parity one stop bit 8 data bits You can use a USB to serial converter if your PC does not have a native serial port Go to About gt Enter Serial Bootloader and the PC host software will scan your serial ports and prompt you to connect to one Once inside the bootloader you can perform a full update of the firmware including updating the USB bootloader and the USB code that s why it uses a different physical medium This will rarely need to be done but is there just in case Continuing on from Part 2 s examples last month we give some more custom scripts to give an idea of how to use the different peripheral features Using Pipes The output of a custom script is a serial stream Logically it is simply a pipe which is the term used to describe this stream Think of it as a pipe into which you put data and it ends up somewhere else in exactly the same order that s the pipe analogy The logging file is a pipe The serial port is another pipe There are others there is the USB serial pipe which is a serial stream over the USB connection to the PC host program The PRINT comma
121. tions global string variables names begin with two characters although there are none defined at this version stage For example the following script shows how local string variables can be used they are assigned using comma separated lists same as with the PRINT print command START CUSTOM SCRIPT HEADER counter A simple script showing how to use local string variables And a counter By Mauro Grassi SCRIPT counter The following is a local string variable SUSU events s aa Open a counter on input D0 it counts falling edges Opening the counter also clears it ie sets it to 0 openFallingCounter D0 Remember the last count while 1 A The Counter is up to readCounter D0 print A U newline sleep 1 END CUSTOM SCRIPT Typical output would be he Counter is up to 0 events The Counter is up to 0 events The Counter is up to 0 events The Counter is up to 0 events The Counter is up to 1 events The Counter is up to 2 events The Counter is up to 3 events The Counter is up to 4 events The Counter is up to 5 events The Counter is up to 6 events The Counter is up to 7 events The Counter is up to 8 events The Counter is up to 9 events The Counter is up to 10 events The Counter is up to 11 events The Counter is up to 12 event
122. to the right if facing the connector and is indicated by a on the top overlay silk screen refer to the component overlay if in doubt The USB TYPE B vertical mounting socket can go in next see overlay It has two mounting tabs that secure it in place and these can be soldered to their pads Then solder the four small pads It remains to solder in the single 3mm blue LED These should be soldered in with the correct orientation and you can cut out a 15mm cardboard spacer so that the LED s body sits at the correct height from the PC board That completes the construction of the USB Data Logger leave IC1 the microcontroller out of its socket before continuing we need to check the supply rail before we do that Powering Up for the First Time You should use 2 AAA batteries to check the supply rails We recommend you use 2 NiMH 900 950mAh batteries Jaycar PH 9226 Altronics S 4742C Of course you can use any AAA NiMH cells here of more or less capacity but you may have to change the 10 charging resistor in parallel with D2 depending on your battery type The formula to use was given in last month s Part 1 article If the 2 AAA batteries are not charged you should charge them before proceeding This may take a few hours A suitable charger is the Jaycar MB 3549 or the Altronics A 0283 With the batteries charged insert them into the battery holder and plug them into CONS also marked with BATT on the top overla
123. u 23 Dec 2010 05 42 01 Destroy 2 VM s Destroying a VM is the terminology for resetting it It has the effect of restarting the script as if it was a POR Thu 23 Dec 2010 05 42 11 Holding In the Holding state all script execution is paused You can toggle the holding state on and off by using a long press on S2 Note that after Holding any loaded scripts will be restarted LED Behaviour The behaviour of the blue LED LED3 gives feedback but it is used sparingly to save power When the USB Data Logger is first powered on the blue LED will flash assuming it has not booted into the bootloader where different LED sequences apply see below LED Behaviour While PC Host is Connected The LED behaves differently when the PC Host is connected and when it is not When the PC Host is connected the LED will follow the activity from the PC host for example it will flash in quick succession when a file is being transferred Once the PC Host is disconnected the LED behaves in standalone mode as described below LED in Standalone Mode The blue LED will flash periodically at about once per second then start flashing 3 times in quick succession as the USB Data Logger prepares to execute any loaded scripts Once the scripts start executing the LED will remain off The LED will glow very dimly as set by the 330k resistor when the USB Data Logger is in standby mode In order to give the user feedback on whethe
124. ue used to accumulate the CRC checksum for NMEA sentence output Syntax SSserial error Effect the last error status of the serial input pipe buffer Syntax S serial getPtr Effect the serial input pipe buffer read location pointer Syntax SS serial lastRx Effect the last received character on the serial port Syntax SS serial newRx Effect indicates that a new character has been received in the serial port input pipe cleared automatically when accessed using the global function newRxXUART Syntax SSserial pipeState Effect the status of the serial input pipe buffer Syntax S serial putPtr Effect the serial input pipe buffer write location pointer Syntax SSspeed Effect 32 bit floating point value indicating ground speed in knots set by the system if a GPS module is present and outputting valid GPS GPRMC NMEA sentences through the serial port Syntax SStemp Effect temporary buffer system limited Syntax ven Effect base address of VM environment Syntax S ven vmExecLimit Effect VM environment execution limit Syntax SS ven vmID Effect VM environment script ID buffer Syntax S ven vmLogFileCache Effect VM environment log file cache base address Syntax S ven vmLogFileName Effect VM environment log file name buffer Syntax S ven vmMinimumPeriod Effect VM environment minimum sleep period Syntax S ven vmMinimumSleepPeriod Effect VM environment minimum sleep period in seconds Syntax SSven vmMode
125. w We now give a number of example scripts that show how to use the global functions to perform some common logging tasks These can be used as templates and customised as needed All the source code for these scripts is provided with the software firmware code as well to make them easy to adapt to new logging tasks Reading an Analog Input START CUSTOM SCRIPT HEADER myAnalogSensorHeader SCRIPT myAnalogSensorScript Basic S cript Showing How To Read and Log an Analog Sensor By Mauro Grassi openADC PRECISION WHILE 1 0 1 T readV 0 0 25 0 028 PRINT The Temperature is T degrees Celsius newline SLE EP 5 END CUSTOM SCRIPT A typical output of the above script would be The Temperature is 8 9 degrees Celsius The Temperature is 8 9 degrees Celsius The Temperature is 8 9 degrees Celsius The Temperature is 8 9 degrees Celsius The Temperature is 8 9 degrees Celsius The Temperature is 8 9 degrees Celsius The Temperature is 8 5 degrees Celsius The Temperature is 103 1 degrees Celsius The Temperature is 103 5 degrees Celsius The Temperature is 103 7 degrees Celsius The Temperature is 103 2 degrees Celsius The Temperature is 8 6 degrees Celsius The Temperature is 64 7 degrees Celsius Reading a Frequency Counter input START CUSTOM SCRIPT HEADER myFrequencySenso
126. we ve logged NUM 0 PRECISION 2 WHILE 1 PRINT decimal NUM 0 readV 0 NEWLINE SLEEP 1 END CUSTOM SCRIPT Controlling IO Pins The digital pins DO D5 can also function as general purpose IO pins and can be configured to be inputs or outputs In the former case the digital level high or low can be read from the pin in the latter case the pin can function as a digital output high or low under the script s control Note that all the IO pins are accessible by all the custom scripts that are running and so in most cases you will need to control a pin in such a manner that the asynchronous execution of another script will not interfere with it This will usually mean that each script will have exclusive control of an IO pin For example to set D2 as an output the command is openlO 2 outputIO To set D3 as an input the command is openlO 3 inputIO Note that inputIO and outputIO are define constants defined globally To close the pin you can use the closelO function which takes a single argument the channel number It simply makes the pin an input so that other functions multiplexed with that pin can take precedence Once the IO pin is opened you can set the value by using the setIO function for example to set D2 to a high level use the command setIO 2 highIO For example if you are monitoring a variable V so that it lies between VMIN and VMAX and you wan
127. x to its right The default is 1 80V remember there is a Schottky diode drop between the battery and the pin at this voltage Status Bar In the Status Bar at the bottom of the window see Fig 3 going from left to right there is a progress bar and a USB indicator showing the number of bytes being transferred through the USB This is periodically reset to 0 and is updated when transferring files to and from the PC Next to that is shown the Device Time which is the time of the RTCC Real Time Clock Calendar on the USB Data Logger or the Local Time Next to that is a variable display you can vary which setting is shown by clicking on the label which can show among other things the time the USB Data Logger was last synchronised the absolute difference in time between the local time and the USB Data Logger s time the relative error in the time etc To the right of that there is another variable display that can be changed by clicking on it It can display the VDD voltage of the microcontroller the Vin voltage at the input to REG1 and it can then estimate the source voltage Vsrc whether the USB Data Logger is being powered using rechargeable cells or an external USB power source Note that we say rechargeable cells because alkaline cells have a higher voltage and may be reported as external USB power Host Settings You can enable the Scale Time option and set the speed up factor in the numeric box to its right T
128. xOT Effect analog channel A1 multiplexed with digital channel D5 Syntax A2 Value 2 0x02 Effect analog channel A2 Syntax Value T E Syntax Value T E Syntax Value Ef E Syntax Value p a Syntax Value aru E Syntax Value T pa Syntax Value Ef E Syntax Value Ef E Syntax Value nl a Syntax Value Ef E Syntax Value Ef E Syntax Value Ef E Syntax Value T E Syntax Value Ef E Syntax Value Ti E Syntax Value T E fect fect fect fect fect fect fect fect fect fect fect fect fect fect fect fect A3 3 0x03 analog channel A3 D0 0 0x00 digital channel DO D1 1 0x01 digital channel D1 D2 24 0X02 digital channel D2 D3 3 0x03 digital channel D3 D4 4 0x04 digital channel D4 multiplexed with analog channel A0 D5 5 0x05 digital channel D5 multiplexed with analog channel Al defaultExecMode 0 0x00 use the system default execution mode restart on HALT defaultPriority 65535 OxFFFF use the system default execution priority defaultUART 0 0x00 default options for the serial port errorOverFlowUART 2 0x02 there was a receive Rx serial port input pipe overflow error errorOverRunUART 1 0x01 there was a receive Rx overru
129. y silkscreen Now measure using a DMM between pins 1 GND and 2 VDD of CON3 You may need to plug in the 4 way screw terminal socket before you do this In any case you should measure close to 3 3V here If you don t disconnect the batteries immediately and recheck your work Check around REG1 you can measure the voltage at its input and its output If you are not measuring much voltage at the output at all it could be because diode D2 is incorrectly orientated If you did measure close to 3 3V all is ok and you can disconnect power Now insert IC1 into its 28 pin socket making sure it is correctly orientated with its notch matching the component overlay Installing in the Specified Case If you ve checked the voltage rails are OK you can proceed to install it in its specified case The USB Data Logger was designed to fit in a plastic instrument case Altronics H 0342 or H 0343 It mounts using four of eight screws supplied with the case 7 mm long see photo The cut outs diagrams for the case are shown in Fig X There are 5 cut outs required on the bottom piece of the case one each for the two switches one each for the two terminal blocks and one slot for the memory card Additionally there are two cut outs required on the top piece of the case one for the USB socket and one for the blue 3mm LED The 2 x AAA battery holder solders straight to the PC board and is stored in the battery compartment of the case for ea

USB Data Logger User Manual

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