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Refined Use Case Model - Electrical and Computer Engineering

1. University of Puerto Rico Mayagiiez Campus Department of Electrical and Computer Engineering uTracker Project Final Report Prepared for Manuel A Jimenez Ph D Associate Professor INEL 4217 Section 070 Professor Manuel A Jimenez By Group Position Aware Jos A Figueroa Omar A Candelaria Pedro J Nieves Yadiel Lamb November 21 2005 GPS uTracker Final Report Abstract The GPS uTracker is an electronic device that uses the Global Positioning System technology to acquire position coordinates data and analyze it providing the user with a range of data feedback including distance between two points and direction The device has multiple applications some as simple as finding a car in a parking lot others as needful as an expeditions guide and some as important as surveying The system is developed to be portable low power and relatively low cost while providing a high efficiency and precision feedback to the user through a simple interface The GPS satellite data is collected through a single chip GPS receiver the Sony GXB5210 and processed using the Atmel AT89C51RC2 a microcontroller which is based in the Intel 8051 architecture GPS uTracker Final Report 1 Table Of Contents 1 Introduction eseseeeoeeeooeoeoeoeoeoeoeoeoeoeoeocoeoeoeoeoeoeoeoeoeoeoeoeoessesssososososososossso 4 P U O 5 2 AGP S Introductio A SO Rk 5 DD Direction Calculation AAA a coco a a a seas ed a aa 5 de D
2. Latitude Upper 22 5 Middle 45 Longitude Figure 3 Destination Vector Range We can map the destination vector by finding in which quadrant it lies and what is the ratio between latitude and longitude Let s go over an example to clarify the previous statement GPS uTracker Final Report 7 Suppose the destination vector is 1 0 0 1 If we look in the quadrant diagram the quadrant that has positive latitude and a negative longitude is the third quadrant Then we take the ratio between latitude and longitude absolute values Ratio 1 0 0 1 10 This ratio is greater than 2 41 which is the tangent value at the dividing line between the upper 22 5 degrees and the middle 45 degrees We automatically know it must be in the upper 22 5 degrees Taking the quadrant as 3 the direction must be north Now suppose the user is looking to the south the calculation would go like this dir_to_move dest _ dir compass _ dir 8 mod 8 dir _to_ move north south 8 mod 8 dir_to_ move 0 4 8 mod8 dir_to move 4 south This means that the user must turn 180 degrees to find the destination location A better example would be the vector 1 0 0 1 which is located in quadrant 1 The ratio is again 10 which means that it is in the upper 22 5 degrees in the destination vector range The direction is south for this quadrant Now suppose the user is facing the south west direction dir_to_move dest _
3. Update screen only when necessary Update only the parts of the screen that changed The microcontroller communicates with the GPS chip by means of a serial communication channel Each time a new character is sent or received an interrupt is generated Is of great importance that all this characters be received The loss of one of these characters will cause the parser to stop processing the current GPS message to prevent the presentation of incorrect data to the user The first step to prevent this problem is to give the serial interrupt the highest priority of all the interrupts In case a serial interrupt is generated at the same time that a keyboard or timer interrupt is generated the serial interrupt will be handled first This will allow us to receive all the characters of the GPS message Additionally limitation of the amount of operations inside of the interrupt was necessary The problem was the serial interrupt had precedence before any other interrupt type but that does not include itself In case a serial interrupt was generated before the previous was handled the received character was lost The solution was to include only the necessary code to add the character to the receive buffer The processing of the character was delegated to the main process At the beginning of the GPS message reception the characters were added faster that they could be handled but after the complete message was received the main process was able to
4. t also be too complicated since it is supposed to attract a general market of users of all types and social classes In that way the system can t be too technologically oriented In the same manner it couldn t be sensitive to signal interference since it has to work on different types of environments and not in a single specified and controlled location The project was later proposed to Dr Manuel Jimenez which understood the uses which the device will have in present day society and approved it He also suggested the implementation of the Global Positioning System GPS technology as the method to provide location awareness to the device The main idea for the development and functionality of the device was then conceived The system will work by obtaining the current position coordinates by means of the standard latitude and longitude measurements through a GPS signal receiver chip Then the device will provide the user a mean to store this coordinates into memory and later be able to compare the current position with the one in memory providing the user with analysis feedback including distance between the two points and direction By implementing the system in this way the device would have a wide range of different uses some including expeditions and surveying applications The GPS chip selected was the Sony GXB5210 distributed and provided by Synergy which was interfaced using an Atmel AT89C51RC2 which is based in the Intel 805
5. respect of top of the device The arrow displayed will change as the device is rotated horizontally TRACKING STATE From the tracking screen the Up and Down button can be used to scroll between screens accessible in the Track State These screens are the track screen the current coordinate screen and the tracked coordinate screen The tracked coordinate screen corresponds to the screen of the selected memory location to be tracked in On State If the Up button is pressed while in the track screen the display screen will change to show the current coordinate screen To return to the track screen while in the current coordinate screen the Down button must be pressed If the Down button is pressed while in the track screen the display screen will change to show the tracked coordinate screen To return to the track screen while in the tracked coordinate screen the Up button must be pressed If the Track button is pressed the system will toggle back to On State where it will be possible to store new coordinates in memory locations or track another coordinate from a different memory location While in Track State the Set button is disabled E Stand by Mode The uTracker features a power saving stand by mode to prevent unnecessary battery power consume while the system is left with the power on and unattended This mode is only accessible when the system is in On State and it is toggled automatically by the system If the device is l
6. 79 11P35 P25 Pe ke Ica 7 1C4 47 WRIPSS P2407 i Jg RD P3 7 P23 PEN pa wo TAZ P2265 A a o ATALI P21 i T 10uF e P20 Reset Intel 80C51 5V 1 5K AT89C51RC2 8 7 E a al LCD1 88 a 8 de 1 5K PO as gt gt 33pF o RW Paaa am re N P2 0 7E al PZA aloa IH 11 0592MHZ N P2 2 9 26 prs 7 082 4x20 LCD DB3 P2 4 11 P2 5 led 33pF P26 13 PB5 NP27 241089 DB7 g 2 GPS uTracker V2 5 Voltage Current T Dmc20481NY Group Position Aware INEL 4217 Microprocessor Interfacing Prof Manuel Jim nez Figure 10 Tracker Hardware Schematic The utracker schematic shows the final hardware implementation of the tracking system The diagram shows the interface for each of the components that where used for our application A voltage source of 5 volts is required for the LCD and Digital compass Similarly a source of 3 3 volts is required for the GPS and 8052 chips Port 0 of the AT89C51RC2 require external pull up resistors in order to output TTL level signals All other interfacing design parameters where selected in order to comply with the manufacturers datasheets GPS uTracker Final Report 20 Auto ISP Interfacing lt P3 1TxD ALOR 7 as R2 ct e c2 c2 Figure 11 Atmel ISP Circuit for AT89c51RC2 UART Programming The programming of the AT89C51RC2 required the Atmel s recommended ISP programming circuit The programming circuit uses a straight serial cable to communicate with the microcontroller v
7. at the single degree level Instead it indicate us the direction we are facing north south west east north east north west south east and south west This is enough for our purposes because we do not give directions at degree level either The compass provides us the information in digital format using 4 output pins We connect it directly into the microcontroller and poll the pins for input each time we need them As stated in the description section the compass will be on only when the device is in tracking mode To control the compass we will use a transistor which will connect the power supply to the compass and will be controlled by an output pin of the microprocessor Below is the pseudo code to handle the compass Subroutine obtain_compass direction Read least significant compass pin Read second compass pin Read third compass pin Read most significant compass pin Use look table to identify the direction Store it in internal memory End Subroutine Subroutine turn_compass_on Write zero to compass control pin End Subroutine Subroutine turn_compass off Write one to compass control pin End Subroutine GPS uTracker Final Report 56 LCD Display To interact with the user the device will use the push buttons for input and the LCD display for output The device contains a 4 x 20 LCD display which is appropriate for the amount of information we are going to display The given LCD is based th
8. catch up with processing For all the timed animations a single hardware timer was used We could have used another timer because the microcontroller had 3 timers One of them is used for the serial communications and one is used for the timed events Having only one timer improved the efficiency of the system because the number of interrupts is kept to a minimum giving more processor time to handling the general procedures The keyboard interrupt extension of the microcontroller was used to handle the push buttons This interrupt is not present in the basic 8051 microcontroller it is an GPS uTracker Final Report 63 extension of the Atmel at89c51 This interrupt is generated when one of the push buttons is pressed which allows us to handle all the button presses Previously the external interrupt was going to be used for this purpose but that approach had the problem of not reporting a button press when one of the other buttons was already pressed When handling the buffered data we have many options to make the process simpler and faster The first was the GPS chip provided us with very detailed information much for which we does not need to concern about The approach was to only interpret what we needed and discard all the unnecessary information The GPS have the capability to output 8 messages each of which gave the information in different formats Our implementation only uses the GPGGA message which provides the latitude long
9. digital compass The GPS chip will be receiving new coordinates every 2 seconds and the direction will be calculated according to direction of the user which is why the compass is turned on Now that we understand every mode of operation we can go through all the functionality of the device and describe each feature in detail The description provided here is general we state what can be done and how the user will do it We say which device will be used in every action but we don t say how we are going to interface with it That s the purpose of a later section Component Interfacing GPS uTracker Final Report 29 When any of the push buttons is pressed the user interface is shown At the press of the button the chip will go into on state and the list of coordinates will be displayed At this screen the scroll buttons will be used to navigate through the stored and the current coordinates When the correct coordinate is selected the user has the option of setting a new coordinate or tracking one of the stored ones Scroll ON STATE Down Scroll Down ON STATE Scroll Down ON STATE Scroll Down ON STATE Scroll Down ON STATE Figure 17 Scroll Down Display GPS uTracker Final Report 30 Scroll Up ON STATE Scroll Up ON STATE Scroll Up ON STATE Scroll Up ON STATE Scroll Up ON STATE Figure 18 Scroll Up Display When the user presses the set button the selected coordinate will be replaced by t
10. dir compass _ dir 8 mod 8 dir_to_move south south _ west 8 mod 8 dir_to_move 4 3 8 mod8 dir_to move 1 north _ west If the user is looking south_west he she must then move straight and to the right to find the south GPS uTracker Final Report 8 3 Discussion 3 1 Block Diagram The ptracker hand held device can be viewed as a combination of 5 sub system blocks The hearth of the utracker system is the 8052 microcontroller The 8052 is in constant communication with the GPS and digital compass blocks The above sub systems are used to provide the tracking information that is used for our application The GPS chip is used for the constant transmission of global coordinates whereas the digital compass provides the current cardinal coordinate that the user is directed at The interface block provides for the human interface with the device Its main components are the LCD display and four push buttons The 8052 controls the interface by providing the data transmission for the LCD and the interrupt handling of the pushbuttons The battery pack sub system provides for the 5V and 3 3V voltage levels that are required by the devices Set Location LCD Data Port P2 0 P2 7 LCD Control Port P0 5 P 0 7 Keypad Port P1 0 P1 3 Power Line Battery Pack Power Line Serial Communica
11. direction is calculated using the relative direction and the quadrant See the theory section for more details about the functionality of each of these subroutines GPS uTracker Final Report 45 Stop the pending animations Disable the standby timer Disable the Transition Timer Reset the inputs Figure 29 General Stage Changing Sequence The preceding procedure is executed each time a change of state occurs It is necessary because it resets many parameters to a default state Animations and timers are reset so they do not conflict with the next state procedure The first step is to disable any pending animations so they do not continue when going to the next state The standby and transition timers are disabled and are only enabled if the next state is the On or To standby state respectively The inputs are reset so no unhandled input is passed to the next state and the screen is updated to reflect the new state GUI GPS uTracker Final Report 46 Check the state ofthe GPS signal Parse the GPS message Incre mentally Update any pending animations Update the screen Figure 30 GPS Data Parsing Sequence For the On Track To Standby and Initialization states the above procedures are done in addition to the specific procedure of each of the states They are presented here instead of presenting them in each of the states flow charts to simplify the exposition of the information in those flow charts Basicall
12. efficiency and reliability in software have declined in importance Many mayor software companies are accustomed to releasing bug fixes for their programs The efficiency factor has declined in importance by the advent of very fast micro processors 3GHz gt However for the embedded market these aspects are as or more important than they were decades ago Embedded applications are used in hospitals planes and military for which reliability is not an option is a requirement The failure of any of these systems can cost millions of dollars and more important they can cost people s life For efficiency we have to take into account that these systems contain slow microcontrollers This is done to decrease the cost of the units and to reduce power consumption The more efficient the software is the slower the microcontroller that can be used In embedded applications faster software means less cost Our project not being the exception to the rule was designed with reliability and efficiency in mind Many factors in our application environment can cause the failure of the system which range from simple graphical interface problems to serial communication failures Incorrect handling of errors can cause the system to malfunction and incorrect data will be displayed to the user As our application has to perform complex calculations find the direction calculate the distance it has to be implemented efficiently The system has to cope w
13. handled 4 bytes data types were only necessary for storing coordinates With the exception of the buffers all the variables are in the 128 bytes of internal memory which the microcontroller handles faster than the additional 1024 of external memory The last data type optimization was to change most of the floating point operations to integer operations which gave us performance gains and better precision Finally a number of general optimizations were applied to the code We used macros for single statements functions The macros provided us with a way to better organize the code without incurring in a performance penalty Compiler general optimizations were turned so the overhead of expression calculation was keep to a minimum The screen was only updated when necessary This prevented the flashing that occurs when the screen is changing to fast and provided a performance gain Additionally only parts of the screen that changed were updated This is done to provide a smoother display and again to obtain better performance GPS uTracker Final Report 65 4 Part List Part List AT89C51RC2 3CSIM Intel 8052 Microprocessor GPS Single Chip Module With Integrated Antenna Sony GXB5210 Push Button 4 x 20 LCD Display DMC20434 Dinsmore 1490 Digital Compass 3 3 V Voltage Regulator 5 0 V Voltage Regulator Quad Inverting Three State Gate 741514 Inverting Schmitt Trigger 82 kQ Resistor 4 7 kQ Resistor 1 kQ Resistor 8 7 kQ Resist
14. microcontroller that was chosen for our application The situation can be improved by taking into account that the compass direction is a unit vector As such the magnitude does not need to be computed Instead of using the above formula we simplified the calculation by taking into account that the compass only provides eight directions To calculate the direction we must map the destination direction to one of the cardinal directions North South East West North East North West South East and South West Then we compare the compass and destination directions to identify in which direction to move The following formula is used when we have the destination mapped to a cardinal direction dir_to_move dest _ dir compass _ dir 8 mod 8 The above calculation should maintain the destination and compass directions between 0 and 7 as to maintain the direction to move within this range Below is a table and diagram that illustrate the code assignment for each cardinal direction Direction Code Direction Code North 0 North West 1 West 2 South West 3 South 4 South East 5 East 6 North East 7 GPS uTracker Final Report Figure 1 Cardinal Coordinate Mapping We now have to map the destination direction to a cardinal direction The procedure is simple Below are two diagrams used to better illustrate the procedure Quadrant 0 Quadrant 1 Figure 2 Quadrant Calculation
15. us to write to flash memory This as being a persistent are of storage provides us with a way to store coordinates for later use The idea is to store hundreds of coordinates and then select the ones we want and put them in internal memory In addition the names of the locations could be stored with the coordinates For example we could give the UPRM name to the UPRM coordinates The uTracker does not provide a mechanism to add a keyboard to it So a PC will be used to download the information to the device by means of a USB port The user could go to a database of coordinates in the internet and download the ones she wants and then use the device to track them The process can also be reversed If the system becomes Bluetooth enabled coordinates can be shared among the devices Later the user could upload the new coordinates and use the PC to look them in a map Finally the chip will regularly write the current coordinates to flash memory When the device is turned on it could check the stored coordinates and use them for the first approximation instead of using the predefined ones GPS uTracker Final Report 71 8 References 1490 Digital Compass Images SI Inc 2005 lt http www imagesco com articles 1490 01 html gt Atmel Corporation AT89C51RC2 Datasheet Atmel Corporation AT89C51RC2 Product Card Atmel Corporation 2005 lt http www atmel com dyn products product_card asp family id 604 amp family_name 8051 Architectur
16. 1 microcontroller architecture and technology GPS uTracker Final Report 4 2 Theory 2 1 GPS Introduction The Global Positioning System GPS is a satellite based navigation system offering precision navigation capability Originally designed for military use civilian access has been permitted to specific parts of the GPS Users can expect a position accuracy of 25 m or better in three dimensions The GPS signal is available 24 hours per day throughout the world and in all weather conditions The equipment necessary to receive and process GPS signals is affordable and reliable and does not require atomic clocks or antenna arrays In its most basic terms GPS determines the position of the user by triangulation By knowing the position of the satellite and the distance from the satellite combinations of satellites can be used to determine the exact position of the receiver The fundamental means for GPS to determine distance is the use of time By using accurate time standards and by measuring changes in time distance is computed GPS ranging signals are broadcast on two frequencies L1 1575 42 MHz and L2 1227 6 MHz of which the L1 frequency is available for civilian use The GPS signal consists of a repetitive binary signal that receivers use to determine the time at which the code was sent from the satellite as shown The waveform from the satellite is matched with an internally generated waveform within the receiver The time differ
17. 2kQ resistor we can use a capacitor of 0 1uF The signal is interfaced via Schmitt trigger inverters to improve signal quality Compass To calculate the direction the user must follow to find its target location we need two types of information the direction of the target and the direction the user is facing To obtain the direction of the target location the GSP chip is used To obtain the direction the user is facing a digital compass is used The digital compass interface follows the parameters and test schematic that was supplied with the datasheet LCD Display To interact with the user the device will use the push buttons for input and the LCD display for output The device contains a 4 x 20 LCD display which is appropriate for the amount of information we are going to display The given LCD is based the HD44780U standard which specifies a set of rules and commands that most of the character based LCD support We are only going to use some of the capabilities of the LCD component the necessary to display the information to the user The hardware interface to the LCD display is straight forward The interface for the RS and E signals requited the addition of two 4 7kQ pull up resistors in order to drive TTL level signals to the LCD GPS uTracker Final Report 22 GPS Chip The most complex of the device components is the GPS chip The chip selected for this project is the Sony GXB5210 single GPS chip This chip is a co
18. Button Press Enable Serial Communication Awake the GPS Chip Enable the LCD 40 The Standby state is different from the others in that it is not executed continuously while the device is in it The Standby state is interrupted when the microcontroller is put in standby and it continues when the user presses any of the push buttons When going into Standby mode a command is sent to the GPS chip to put it into low power mode Below is a flowchart of the process of sending the command to the GPS chip After the command is sent serial communications are disabled The parser is reset to eliminate any remaining parse data The parser will start in a clean state when the microcontroller is awakened The LCD is disabled to reduce power consumption Finally the microcontroller is put into low power mode From this state it can only exit when a keyboard or external interrupt occurs The device has nothing connected to the external interrupts which means the microcontroller could only be awakened by a push button press When a push button is pressed the microcontroller receives the keyboard interrupt the keyboard interrupt will be explained in the microcontroller section At this time the microcontroller is awakened and the interrupt is processed Serial communications are again enabled and the GPS chip is awakened The process to awaken the GPS chip is shown below It essentially consists of sending a command to the GPS chip wh
19. ET TRACK UP and DOWN The UP and DOWN buttons are used to move through the stored coordinates The SET button is used to add new locations and the TRACK button is used to find a stored location Each push button is connected to a given pin in the microcontroller When one of this buttons is pressed the microcontroller will raise a keyboard interrupt The interrupt based approach provides many advantages The first advantage is that all the button presses will be reported polling the inputs does not guarantee that The second is that our code will have better structure we will handle the state of the device using an event driven architecture Below is the pseudo code for the management of the push buttons Subroutine handle keyboard interrupt Read SET button pin and store it in internal memory Read TRACK button pin and store it in internal memory Read UP button pin and store it in internal memory Read DOWN button pin and store it in internal memory End Subroutine GPS uTracker Final Report 55 Compass To calculate the direction the user must follow to find its target location we need two types of information the direction of the target and the direction the user is facing To obtain the direction of the target location the GSP chip is used To obtain the direction the user is facing a digital compass is used The compass used in this device is Dinsmore 1490 Digital Compass This compass does not provide us with measurements
20. ISCUSS O I EEES TE A E A E O R E 9 DV Block Diagrama enea A E a aaa 9 3 2 Power EA e a uae Duros ea oo Tea do 10 3 3 Timing AA SA A a O a A cage ays 13 3 3 1 Setial COR ICA di 14 332 CCD Dita AA A ARE 15 3 3 3 Track Baton Pr nd tia 16 3 3 4 Set B tton Pressed O II A A dis 17 34Memory MD Aid 18 a o A A A O A iai 20 3 6 Hardware Termination Eve tc 24 Al A ON 25 DT A MSTA O aay E E n T E A aAA 25 3 7 2 Complete Usage DES a ade olas 27 SS Flow Charts E TS A A hastens 34 3 14 General Pseudo CO 50 3 7 5 Component meda das 55 3 8 Software Termination Level oooooconocococinonicoccnononaccnnonananonononnnncononnononoonnannnnconnananonn 61 3 9 Efficiency and Trustworthiness vi 25002 joc clos teh aca cars boned Ca aa eo iac ida 62 4 Part Lista sSianeiaaeaetasserastendunseasdbeiseetes 66 US A inosus crides ssostni Saoer rine soei Eoia oi 67 6 CONCISO ii A ies 68 A O osar aoo siso da eie ce aooiie Sokeat estea sano castio keii ia 69 8 Referent A A O 72 9 User Manta A A A 73 Appendix A AT89C51RC2 Datasheet o concocccncononccconcnncncononoconanccnocacannnos 77 Appendix B Sony GXB5210 Datasheet eessooessoeessoosscsoesssoosssoesesooseso 77 Appendix C DMC20434 LCD Display Datasheet ooossooesooeessooessoos000 77 Appendix D Dinsmore 1490 Digital Compass Datasheet 000 77 Appendix E Program Listing eessesssoooessoesssocessoeessocsesoesesooosssseessosseso 77 GPS uTracker Final Report 2 List of Illustrat
21. ON STATE Figure 15 Initializing Display The second mode of operation is standby In this mode of operation the microcontroller Atmel at89c51 is in standby the GPS chip is in low power mode and all the other components are off This mode is entered when the device is on but it has been unutilized for 30 seconds or more The stored coordinates are preserved the GPS updates the coordinates every 10 seconds but the microcontroller does not process them The coordinates are updated regularly to prevent the GPS chip to go into the warm state When the GPS chip enters the warm state later coordinates queries will last around 30 seconds instead of the 2 seconds when the device is in the hot state GPS uTracker Final Report 28 Standby Display ON STATE 30 seconds inactive TO STANDBY STATE 2 Seconds STANDBY STATE Any Button Press ON STATE Figure 16 Standby Display If any button is pressed the device will go into the On state In this mode of operation the microcontroller is on the LCD display is on the compass is off and the GPS chip is in active state updating the coordinates every 2 seconds The user will be able to interact with the device in the on state which makes the LCD necessary Note the compass is off in this state because it is not needed When the user presses the track button the device enters in the last state the tracking state In this mode of operation all the components are on including the
22. T port programming of the AT89C51RC2 that was used for the programming of the microcontroller The serial interface variables for the UART data parsing and buffering cover the address space from 03FFFh to 7FFFh GPS uTracker Final Report 19 3 5 Hardware Schematic The general schematic of the system is structured in the following manner 5V 5V 5V 5V A N a o ES 82k re 82 S 82k Zo 82k _ tit T a ra Gag fai AUF AUF AUF AUF 1110 5 7 g wt 3 trl ds 7 1c4 P1 0 ij ij j i ie Down Up Track Set PTZ sliy os PEAN 7104 ot alos 1C4 3 3V 3 3V 5V Fi Pul Up Resistors c9 E EARN a TT ll age obs Yo Ic2 10uF 2 si Se se Ici S 5 amp oe oe ox gt P1 0 4 74 4 71 2 1K 1K 1K 1K 0 Alo vec 2 e 2 Backup 9 SPIT fet oo la Sl reset GPS Module o xl 163 Ol NECE 212 Pot e 5 BR0 hiinas 7 Apra Po2 pe 4Jer1 2 Tan 8 le Lf P1 4 aiD h El 80 gt c3 PTS Pr Pia pose RXDO BO soa c2 4 PTE Pr lp1 5 Poa 26 Digital Compass c1 A PTT SPLIT Pte POS PO 7 E co P17 PoS S POS mel 2 Sony GXB5240 last poz 2 p 1 e 1490 Digital Compass RDIP3O EANPPT mars psen E 3 3V ie 1B jinttP3 3 p27 p35 Bae 10K ae P26 PB ipt dia
23. acker device Switch Button Press Initialize the device parameters and IO subsystem Initialize the LCD dis play Initialize the GPS Chip Initialization Animation Figure 20 System Initialization Procedure GPS uTracker Final Report 34 When the on off switch is moved to the on position power is applied to all the components The microcontroller and GPS chip are reset by means of hardware All the system variables are set to default values and the coordinates are set to an approximation of the current coordinate The IO system is then initialized The serial port is programmed to give the appropriate baud rate and to generate interrupts for transmission and reception of characters The transmission and reception buffers are initialized and the GPS message parser is started Timer 0 is initialized to control all the timed events of the uTracker software like animations and the standby count down timer The ports are programmed for input or output for input a one is written to the pin The pins that receive the push button inputs are set to generate an interrupt when the button is pressed The next step is to initialize the LCD display which requires a predefined sequence of command After the LCD is initialized the screen is cleared and the initialization screen is presented This screen will be animated until the end of the initialization phase Finally the GPS chip is initialized Below is a flowchart of the GPS ch
24. al scenario of the tracking device s usage Images of the device s display are provided at the end of this section The images provide a visual description for each state of the process Note that the format of the display is free to change in the near future but the general functionality of the device will stay the same The following scenario provides a general description of the device operation from the user s point of view A complete description of the device s usage is presented in the next section We begin our scenario with the device in the off state The first time the device is turned on it will initialize and the first GPS coordinates would be received At this stage the device will be displaying a busy message to the user indicating the device is preparing to provide its required functionality This stage will take a considerable amount of time around 15 seconds but later queries will be considerably faster 2 seconds The initialization time would be used to setup the UART communication parameters and to stabilize the internal signals The first coordinates will be stored in memory so that the user does not need to press the set button the first time the device is turned on If the user wants to set a new location he she will need to press the set button to obtain the new coordinates Note that the device does not need to be turned off this operation is only done to increase battery life In the case that device was activ
25. architecture The handling of data types with greater sizes is emulated by software The emulation of a floating point number required first the emulation of a 4 byte integer data type and above that the emulation of a floating point data type Using floating point math incurs a performance penalty but is necessary for our application The method that we used reduced the number of these operations The previous discussion only talks about the direction calculation but the distance also has to be calculated Again the traditional methods are too time consuming The distance calculation between a pair of latitude and longitude required the use of the GPS uTracker Final Report 64 spherical coordinate system The distance is calculated by using the cosine and sine functions which are too expensive to make in the microcontroller A solution could be to use a lookup table that contains the values of these functions but that would need 360 floating point entries for each of the tables giving a total of 2880 bytes too much for a microcontroller What we did was to perform a linear approximation of the distance When using this linear approximation for distances of around 10 000 the maximum for our system the error ranged between 0 1 5 As the microcontroller is based on an 8 bit architecture we tried to maintain the size of the device variables to the minimum possible Most variables are in the 1 byte 2 byte range which are efficiently
26. atitude is negative and longitud return quadrant 2 else if latitude is positive and longitud return quadrant 3 end if EndSubroutine Find the relative direction Subroutine find relative direction if ratio of latitude to longitude gt 2 41 return 0 else if ratio of latitude to longitude lt 0 41 else end if Subroutine calculate direction quadrant return 2 return 1 End Subroutine Longit if direc ude gt Latitude tion 2 Wes t or East if quadrant 0 or quadrant 1 ret else ret end if urn west urn east Latitude gt Longitude else if direction 0 North or South if quadrant 0 or quadrant 3 return north else return south end if GPS uTracker Final Report direction 53 Middle 45 degrees else return 1 quadrant 2 end if End Subroutine Identify the direction the user must move to Subroutine find direction to move return dest direction compass direction end Subroutine GPS uTracker Final Report 8 mod 8 54 3 7 5 Component Interfacing Switch Button The purpose of the switch button is to toggle the equipment between on and off To realize its function it only has to disconnect the circuit from the power supply No code is necessary to handle this component Push Buttons The device has 4 push buttons among its components S
27. cations that prevented us to add features to the system that were not in the original specification But the ideas are exposed here so later groups can implement them for their projects Ideas e Hardware Use an analog compass Use an inclination sensor Provide the microcontroller programming circuit in the device e Power Management Control the speed of the microcontroller Control the contrast of the LCD Provide a backup battery for the GPS chip e Additional Functionality Provide a better user interface Provide more detail about the GPS signal Provide an atomic clock Use the counter extension for timed events management e Flash Memory Store more coordinates Store the name of the coordinate s location Caching the last coordinate to sent to the chip at startup e Bluetooth amp USB Interchange locations with other devices Upload new locations taken from other devices and lookup them in the map Download new locations GPS uTracker Final Report 69 When we found the digital compass the idea of having the direction given in digital format was simple When we were making the device we found this was not completely true The problem was the compass is not very precise and assigns more range to some cardinal directions North occupies 65 of the top two quadrants A better approach will be to use an analog compass which will give use better precision and will allow us to select the directio
28. e HD44780U standard which specifies a set of rules and commands that most of the character based LCD support We are only going to use some of the capabilities of the LCD component the necessary to display the information to the user To display the information to the user we need the following capabilities e We must be able to initialize the LCD e Clear the screen e Set the cursor position at a specific location e Write a character to the screen Below is the code necessary to provide the previous functionality Explanations of each code snippet are provided as well Subroutine init _LCD send _reset_command 0x30 send _reset_command 0x30 send_reset_command 0x30 send_init command 8 bit bus send _init_command 4 character display send _init_command turn LCD on send _ init_command turn cursor on send _init_command automatic cursor positioning End Subroutine Subroutine send init_command command code Prepare to send command Set command code Send the command wait_until command finishes End Subroutine Subroutine wait_until_command finishes while not maximum number of iterations and not ready poll ready flag End Subroutine GPS uTracker Final Report 57 Subroutine clear screen Prepare to send command Set clear command code Send the command wait until command finishes End Subroutine Subroutine write_character character Prepare to send command Enab
29. e amp pa rt_id 2854 gt Atmel Corporation C51 API Program Examples Atmel Corporation AT89C51RC2 Product Card Atmel Corporation 2005 lt http www atmel com dyn products product_card asp family id 604 amp family_name 8051 Architecture amp pa rt_id 2854 gt Atmel Corporation FLIP 2 4 4 for Windows Flip 2005 lt http www atmel com dyn products product_card asp family id 604 amp family name 8051 Architecture amp part_id 2854 gt Atmel Corporation Hardware Interface Connection Examples for C51 MCU Atmel Corporation AT89C51RC2 Product Card Atmel Corporation 2005 lt http www atmel com dyn products product_card asp family_id 604 amp family_n ame 8051 Architecture amp part_id 2854 gt EdSim51 The 8051 Simulator for Lecturers and Students NyCelt LLC 2005 lt http www edsim5 1 com gt How to control a HD44780 based Character LCD Peter Ouwenhand 22 Jan 2005 lt http home iae nl users pouweha Icd Icd shtml gt Synergy Systems LLC SONY GXB5210 GPS RECEIVER DATA Board Level GPS Products 2005 lt http www synergy ps com SONY 20GXB5210 20GPS 20 Receiver 20Data pdf gt The 8052 Online Reference Vault Information Services LLC 14 Sept 2005 lt http www 8052 com gt Vahid Givargis Embedded Systems Design A Unified Hardware Software Introduction John Wiley amp Sons 2002 GPS uTracker Final Report 72 9 User Manual A Device Components P
30. e direction This improves performance because the calculations are only done when they are needed If the up button is pressed in this state the device presents the current coordinates Additional up button presses have no effect when the device is already presenting the current coordinates To return to the track screen the down button must be pressed In this screen if the down button is pressed the destination coordinates are presented Additional down button presses have no effect when the device is already presenting the destination coordinates To return to the track screen the up button must be pressed The set button has no effect in this state Set button presses are simply ignored When the track button is pressed the device goes to the On state again Below is the flowchart for the calculate direction subroutine GPS uTracker Final Report 44 Calculate the destination dire ction Calculate difference between destination and current coordinates Determine the quadrant of the direction Calculate the relative direction Calculate the absolute direction Figure 28 Destination Direction Calculation Sequence The first step is to calculate the different between the destination and current locations This will give us the destination vector The next step is to calculate in which quadrant the vector resides and which of the three possible directions inside a given quadrant it is pointing at Finally the absolute
31. e is entered the current coordinates will be displayed The user can use the Up and Down buttons to move the menu up or down respectively When the user is looking at the current coordinates he she can press the Down button to see the first stored coordinate If he she presses the Down button a second time the second stored coordinate will be displayed and the same applies for the third coordinate pressing the Down button when looking at the third coordinate will switch the display to the current coordinates menu again The functionality of the Up button is similar to the Down button only that the menu scrolls up instead of down If the Set button is pressed while selecting one of the stored coordinates one of two things can happen If the GPS signal is present the selected coordinate will be set to the current coordinates If the GPS signal is not present an animation of the GPS signal indicator will be displayed Note that when the user is looking at the current coordinates the Set button does not have any effect The Track button is used to go to the Track state where the current selected coordinate will be tracked using the GPS chip and the compass The functionality of the Track button is similar to the Set button If the GPS signal is not present the non signal animation will be shown and if the user is looking at the current coordinates the Track button has no effect We can note at the beginning of the state the compass is di
32. e off and device on with track mode on The power consumption for each operating mode is calculated next e Device OFF All components are turned off Total Power P sony GxB5210 P Intel 8052 P LCD 4x20 P Digital Compass 0 mW 0mW 0mW 0mW Total Power 0 mW e Standby After 15 seconds of inactivity the device is switched to standby mode This mode is only reachable if the device is On with track mode Off During this mode the GPS chip is in standby and the LCD Screen and Digital Compass are switched off Total Power P sony GxB5210 P Intel 3052 P LCD 4x20 P Digital Compass 0 033 mW 31 000mW 0mW 0mW Total Power 31 123 mW e Device On with track mode Off The system is on but the position information is updated every minute The GPS chip is in standby until the information is requested by the timer The Digital Compass chip is turned off Total Power P Sony GXB5210 signal acquisition T P Intel 8052 P LCD 4x20 P Digital Compass 231 mW 31 09mW 50mW 0mW Total Power 211 09 mW e Device On with track mode On The system is on and updating the position information every 2 seconds The GPS and Digital Compass chips are on during the operation Total Power P Sony GXB5210 Tracking Mode T P Intel 3052 P LCD 4x20 P Digital Compass 165 mW 31 09mW 50mW 150mW Total Power 396 09 mW GPS uTracker Final Report 11 The maximum power consumption of the device occurs when the d
33. e prior to the moment of adding a new location the user will have to press the set button to add the current coordinates to the list of tracking locations At the time the user wants to find the stored location she will press the track button The device will present a list of the most recent stored locations 3 at this time and the user will chose the appropriate coordinate using the scroll buttons up and down and press the track button again to begin the tracking process The device will begin to give directions to the user until the user finds the target location At this time the user will press the track button to deactivate the tracking mechanism GPS uTracker Final Report 25 The following figure shows the LCD interface of the device as it switches from each stage General Utilization Display OFF STATE INIT STATE 45 secs ON STATE Track Button Press TRACKING STATE Any Button Press ON STATE Figure 13 LCD Interface General Utilization GPS uTracker Final Report 26 3 7 2 Complete Usage Description In the previous section we provided a general description of the device functionality The purpose of this section is to provide a more detailed description now from the point of view of the device itself Many aspects of the device functionality were omitted from the previous section because they are not really needed in a typical scenario They are important features however and they will be explained here
34. ecial case where the letters CURR are displayed showing that it s the current coordinates screen After the desired location is selected press the Set button to save the current coordinates into that location The screen will be automatically refresh and show the coordinates stored The Up and Down buttons can now be used to select another screen and store the coordinates into another location or to return to the current coordinates screen To track a stored coordinate scroll through the memory locations screen until the display screen shows the location and values of the desired coordinates to be tracked Press the Track button to select the stored coordinate and set the system to Track State D Track State When the device enters into Track State the track screen is shown in the display screen The track screen displays the information obtained from the analysis and comparison of the current coordinate of the device obtained from the GPS satellites and the coordinate stored in memory In the bottom right part of the screen below the letters ALT the difference in altitude is shown in meters In the center of the screen below the letters DIST the linear distance between the two coordinates is displayed in meters In the bottom left part of the screen below letters DIR one of eight arrows is displayed This arrow points to the direction where the tracking coordinate is located with GPS uTracker Final Report 75
35. eft in the On State for more than 30 seconds without receiving any input from the user the system will display the stand by screen to announce that it is about to enter to the stand by mode This screen is displayed for 2 seconds and then the display screen is turned off and internal system activity is reduced The device returns to the On State when it detects that a button has been pressed GPS uTracker Final Report 76 Appendix A AT89C51RC2 Datasheet Note Files found inside project CD Appendix B Sony GXB5210 Datasheet Note Files found inside project CD Appendix C DMC20434 LCD Display Datasheet Note Files found inside project CD Appendix D Dinsmore 1490 Digital Compass Datasheet Note Files found inside project CD Appendix E Program Listing Note Files found inside project CD GPS uTracker Final Report 77
36. en down end if Stop tracking if button track is pressed Disable the Compass Go to the On state end if State To Standby GPS uTracker Final Report 51 Check if a button is pressed if any button is pressed Go to the On state end if Transition time elapsed if transition time is greather or equal to 2 seconds Go to the Standby state end if State Standby SetGPSLowPowerMode DisableSerialCommunications ResetParser DisableLCD StopMicro Activated by interrupt EnableSerialCommunication SetGPSActiveMove EnableLCD Go to the On state State All Parse incomming GPS data Update the screen End State Machine End While End Program Maintains the index between 1 3 Subroutine WrapValue index numValues return index 1 numValues numValues 1 End Subroutine Calcuate the destination direction Subroutine calculate dest direction find quadrant find relative direction calculate direction quadrant direction End subroutine GPS uTracker Final Report 52 Find the quadrant where the destination vector is located and longitude is positive is negative is negative Subroutine find quadrant if latitude is positive and longitude is positive return quadrant 0 else if latitude is negativ return quadrant 1 else if l
37. ence between matching waveforms is used to compute the distance from a satellite The GPS constellation is composed of 24 satellites 21 active satellites and three orbital spares To calculate a two dimensional position at least three satellites are necessary For a three dimensional position at least 4 satellites are necessary As the number of satellites in view is increased the location error decreases 2 2 Direction Calculation Most of the work involved with GPS is handled internally by the Sony GPS chip What remains to be done is to ask the chip for the destination coordinates and the current coordinates and use that information to arrive at the target location Essentially what we must do to find the target is to find the angle between the destination vector and the compass orientation For example if the destination direction is west and the compass orientation we are looking at that direction is east the device GPS uTracker Final Report 5 should specify that we must move backwards to find the location or turn 180 degrees and move forward Our biggest concern is to do this efficiently The formula to calculate the angle between two vectors is given below if VleV2 angle cos V1 V2 The above formula requires too many computing resources for our application The operation requires a dot product two magnitudes and a division not to consider the inverse cosine that are very hard to perform with the
38. erial Output Port Figure 5 Timing interaction of multiple serial port commands in succession GPS uTracker Final Report 14 3 3 2 LCD Data LCD Data Papa AA D0 D7 LCD Input Enable LCD Read Write 00 AG LCD Backlight fe LCD Buffer Enable eee Button Input Figure 6 Data output and interaction with LCD display when a button is pressed GPS uTracker Final Report 15 3 3 3 Track Button Pressed Track Button Micro Tx Port Micro Rx Port Compass Port LCD Port O A Gf O AAA AN OOU _ AAA SET Figure 7 Timing interaction of the tracking command operation GPS uTracker Final Report 16 3 3 4 Set Button Pressed Set Button Micro Tx Port Uy A ee Micro Rx Port A IT E LCD Port A Figure 8 Timing interaction of the set command operation GPS uTracker Final Report 17 3 4 Memory Map The internal memory of the AT89C51RC2 microcontroller is organized in the following manner The AT89C51RC2 has the following memory areas e User memory area 16 32 KB size e ROM bootloader memory 2 KB size e Hardware security byte for configuration information and security levels e XAF area for ISP Boot Status Byte BSB Software Boot Vector SBV Software Security Byte SSB Notes 1 Refer to A T89C51RC2 RB2 or A T89C51IC2 datasheets and boot loader datasheets for HSB and XAF description 2 As boot loader is in ROM memory no erase or write action is possible on this area Int
39. ernal and External Data Memory Address OFFh or 3FFh OFFh OFFh Upper i 128 Bytes piece Internal RAM Register Direct Accesses Indirect Accesses XRAM 80h 7Fh General IRAM amp Stack Space Lower 30h 128 Bytes 28h Bits Internal RAM E 20h 00 7F Variables Space Directo indect 187 E register 00 00 00 Banks HSB bye Y A XAF few bytes OFFFFh FFFFh n 2 KB ROM A Wa Programing External F800h m Data Memory 7FFFh Serial Interface Variables A re y and Buffer for UART PON ey dede GPS Communication 3FFFh 16 32 KB User Flash Application OOFFh up to O3FFh Application Code Area 0000 MINI 0000 Figure 9 AT89C51RC2 Memory Mapping GPS uTracker Final Report 18 The code for our application covers both the internal OOh OFFh and external memory areas OOFFh OFFFFh The internal address space was divided as follows The 8052 uses address space 00h to 28h as register bank and bits space The area from 30h to 7Fh is used to store all the programming variables for our application except for the serial buffering and parsing variables that require more address space than available Address space from 80h to OFFh is reserved on the 8052 for the special function registers The external address space is not completely accessible for user programming The boot loader ROM area OF800h OFFFFh is used by the FLIP programming tool as an In System Programming tool for the UAR
40. evice is set to Tack Mode in which case every component is on for the tracking operation Given the previous analysis the maximum power consumption of the device is calculated as 396 09mW The calculation of the approximate running time with batteries is based on the maximum power consumption of the components and the battery s mAh capacity Battery 5 AA Duracell MN1500 2850mAh Runtime in Track Mode On Power Comsumption 396 09 mW Aproximate Amperage 50 9 42 10 30mA 99 42 mA Time 2850 mAh 99 42 mA 28 66 hours Runtime in Track Mode Off Power Comsumption 211 09 mW Aproximate Amperage 50 9 42 10 mA 69 42 mA Time 2850 mAh 69 42 mA 41 05 hours Runtime in Standby Mode Power Comsumption 31 123 mW Aproximate Amperage 50 9 42 mA 59 42 mA Time 2850 mAh 59 42mA 47 96 hours GPS uTracker Final Report 12 3 3 Timing Analysis The minimum working frequency of the system will be determined by analyzing the reaction time requirements for each peripheral The system consist of 8052 microcontroller Sony GXB5210 single chip GPS receiver Dinsmore 1490 Digital Compass LCD Display and four push buttons for general input The LCD Display reacts to inputs only and doesn t send any acknowledge of data received It is assumed to react whiting the specified reaction times for each internal operation The digital compass has the timing limitations of a regular water based compass It provides co
41. he current coordinates If the user presses the track button the system will enter tracking state and it will track the selected coordinate Note that if the user is looking at the current coordinates or the GPS signal is not present the Set and Track buttons are disabled An animation is show when the user tries to set or track coordinates when the GPS signal is not present GPS uTracker Final Report 31 Track State ON STATE Track Button Press TRACKING STATE Up button Press TRACKING STATE Down button Press TRACKING STATE Down button Press TRACKING STATE Up button Press TRACKING STATE Track button Press ON STATE Figure 19 Track Mode Display GPS uTracker Final Report The device provides useful information while in track mode which means that a different user interface is used This interface shows the direction of the destination location the distance and difference of altitude between the user and the target location If the user presses the up button while in track mode the current coordinates are presented If the user presses the down button the destination coordinates are presented To stop tracking mode press the Track button and device will go into On state again When the device remains inactive for more than 30 seconds it will enter standby mode GPS uTracker Final Report 33 3 7 3 System Flow Charts The following section explains the operating flow charts for the operation of the UTr
42. ia Atmel s FLIP programming tool Required parts for the circuit were one MAX232 driver five 0 1uF capacitor one 10 UF capacitor instead of the 1 UF capacitor that is recommended four 10 kQ resistor one 1 kQ resistor for the discharge of the10 UF capacitor two 2N3904 NPN transistors for the automatic RESET and PSEN signal handling The final implementation of the programmer added three Schmitt trigger inverters for the correction of the programming RESET and PSEN signal Switch Button and Reset The purpose of the switch button is to toggle the equipment between on and off To realize its function it only has to disconnect the circuit from the power supply The circuit parameters where taken from Atmel s ISP programming schematic with a capacitor parameter modification from 1uF to 10uF The Parameter modification was made in order to better the reset signal of the microprocessor The reset signal drives the reset of both the 8052 and GPS chips via Schmitt trigger inverters to improve signal quality GPS uTracker Final Report 21 Push Buttons The device has 4 push buttons among its components SET TRACK UP and DOWN The UP and DOWN buttons are used to move through the stored coordinates The SET button is used to add new locations and the TRACK button is used to find a stored location The push buttons where interfaced with a de bouncing circuit Vi Val 5 ee Our calculations assume 1 5 68ms V 2 5V V jing 5V Using an 8
43. ich indicates to the GPS chip to calculate the location at every moment When the GPS chip was put in low power mode the chip calculated the location every 10 seconds now it calculates it every second The LCD is enabled and cleared to eliminate previous data Then the chip is put into the On state again Put the GPS in Low Power Mode Send Command aPLM 10 ME Wait for acknowledgement Figure 25 GPS Low Power Mode Switching GPS uTracker Final Report 41 Awake the GPS Chip Wait for the acknowledgement Figure 26 GPS Power Up Mode Switching GPS uTracker Final Report 42 Enable the Compass Calculate the destination direction New GPS Data Get the compass orientation Determine the direction to move towards the destination Up Button Pressed Move Menu Up Down Button Pressed Move Menu Down On State Figure 27 Track Mode Operating Sequence GPS uTracker Final Report At the beginning of this state the compass is enabled This is the only state where the compass is enabled because it is necessary to calculate the direction to move towards the destination The direction vector is calculated every time that a new coordinate is received A later section of this document explains this process in greater detail Essentially we only map the destination direction when a new data arrives but once every cycle we need to calculate th
44. in more detail We now proceed to provide the complete description of the device s functionality with all its features and modes of operation Once again images of the device s display are provided at the end of this section The images and written information complement to provide a complete description of the device We begin by giving a description of the device itself The tracking device is composed of 6 items a LCD display 4 push buttons 1 switch an Atmel at89c51 microcontroller a SONY GPS chip and a digital compass The purpose of each of these components will be explained when they come up in the device s operation description The tracking device can be in four states of operation off standby on and track Turn Off ON STATE Devi ce On Button Switch OFF STATE Figure 14 Off Mode Display When the device is in the off state all the components are turned off they are not in standby When the device enters this state all the stored information is lost The stored coordinates are deleted so later attempts to find the stored locations will fail In this state the device consumes no power everything is off which is the reason of providing it the battery life will be extended if the device is in this state when the user is not using it The system is taken into and out of this state using the switch component GPS uTracker Final Report 27 Initializing Display OFF STATE INIT STATE 45 secs
45. ions Figure 1 Cardinal Coordinate Mapping sscccsccesccssssseseccsscceesccssaserscsssncesacsssscssnessnes 7 Figure 2 Quadrant ale acon ii e es ii ii ai i iaa 7 Figure 9 Destination Vector RA a Sah it ar Aaa a ne Ge ote alt a 7 Figure 4 1 Tracker Block DIA PIM A AO RO O 9 Figure 5 Timing interaction of multiple serial port commands in succession 14 Figure 6 Data output and interaction with LCD display when a button is pressed 15 Figure 7 Timing interaction of the tracking command operation cceeeceeseeseereeeeees 16 Figure 8 Timing interaction of the set command operation ceceeeeseeeeeeeeceeeeeeeeeees 17 Figure 9 AT89C51RC2 Memory Mapping ccccecccessseceseceseceeeeeeseecteceseeneeeenseeeaeenes 18 Figure 10 Tracker Hardware Schematic iii its 20 Figure 11 Atmel ISP Circuit for AT89c51RC2 UART Programming c eee 21 Figure 12 PEO PEL ds 24 Figure 13 LCD Interface General Utilization dida 26 Figure T4 Off Mode islas 2T Figure 15 Initializing Display eh fess fur A els ace uceciage Matante 28 Figure 16 Standby Display it dildo ds 29 Figure 17 Scroll Down Display ita 30 Figure 18 AA O pe ncaiaclavccnmouwecs 31 Figure 19 Track Mode Disp iio 32 Figure 20 System Initialization Procedure oooonccnncnnocnncnnoncnnnconcconcnononnncnnc co nonnnonnnonncnnn ns 34 Figure 21 Sony GXB5210 Initialization Sequence ee eeeeseceeeneeeeeeeeeeeceseeneeeneeeneess 36 Figu
46. ip initialization sequence which requires the sending of two commands The first command indicates to the GPS chip that we only need one of its messages the GPGGA message and that we want it every 2 seconds Receiving the message every 2 seconds will allow us to parse the data before the next message is received The second command is used to provide an approximate location This will allow the GPS chip to acquire the GPS signal faster This is currently set to the Puerto Rico coordinates to allow fast reception of the location information Finally the device waits for the GPS chip to receive the commands and goes to the On state GPS uTracker Final Report 35 Initialize the Sony GPS Chip Send Command a NC 20000000 Send Command PM N1Sd00W067d00 Figure 21 Sony GXB5210 Initialization Sequence GPS uTracker Final Report 36 Disable the Compass Start the Standby Timer Move Menu Up Reset Standby Timer Down S Button TE Move Menu Pressed Down Reset NO Standby Timer YES Set selected coordinate equal to the current coordinate Reset NO Standby Timer Track YES Button Track State Pressed YES To Standby State Figure 22 On State Operating Sequence GPS uTracker Final Report 37 In the On State the device provides the user a scrollable menu In this menu he she is able to check the current coordinates and three stored coordinates The first time the On stat
47. is found the parser knows the GPGGA message follows because it is the only enabled message The GPGGA string is extracted and checked to see if this is the GPGGA message The UTC time is then skipped Then the latitude is extracted by means of the procedure outlined in the second flow chart for obtaining number values Note the procedure adds all the characters to the buffer and then changes them to a number The north indicator is skipped Now the latitude must be extracted by using the same method used for the latitude The West indicator is skipped Following is the GPS signal indicator It is skipped because we are using the number of satellites to know if the signal is present or not The number of satellites is then extracted and converted to a number Finally the altitude is obtained and the rest of the message is discarded Note from the second flow chart that the decimal point is read but not added to the buffer This is done to build an integer number not a floating point number This means that 18 000000 will be converted to 18 000000 18000000 Using integer math will allow us to obtain better precision in the calculations and the calculations will be done faster GPS uTracker Final Report 49 3 7 4 General Pseudo Code The device operation is controlled by a driving subroutine This subroutine will call the component handling subroutines to do its work The next section describes the code for handling each component in th
48. is section we only explain the general handling subroutines Program uTracker Loop forever While TRUE Check the GPS signal isGPSSignalPresent State machine State Machine State Init ResetDeviceVariables InitTOSubsystem InitLCD InitGPSChip Go to the On State State On Reset the tim if any button pressed ResetStandbyTimer end if Move the menu up if button up is pressed curr coord wrapValue curr coord 1 end if Move the menu down if button down is pressed curr coord wrapValue curr coord 1 end if Set the current coordinates if button set is pressed if GPSSignalPresent selected coord curr coord else GPS uTracker Final Report 50 ShowNonSignalAnimation end if end if Track the coordinates if button track is pressed if GPSSignalPresent Enable the compass Go To the Track State else ShowNonSignalAnimation end if end if If the standby time elapsed if inactive for 30 seconds Go to To Standby end if State Track Check if the destination direction should be calculated if new data calculate dest direction end if Identify the direction the user must move to find direction to move Move the menu up if button up is pressed and the screen current coords move screen up end if Move the menu down if button down is pressed and screen dest coords move scre
49. ith many processes at the same time The GPS data has to be received and parsed the directions and distances have to be calculated the GUI has to be updated all of this at the same time A list is presented below with all the optimizations and measurements taken to develop a reliable and efficient system Each of these measurements is better explained in the following paragraphs Note they are grouped for better comprehension of their usability and contribution to the system reliability and efficiency Measurements e Interrupt Handling Give more priority to the serial interrupt Implement serial data buffering Limit quantity of operations to execute inside interrupts Use only one timer for all the timed events Use the keyboard interrupt instead of the external interrupt e GPS Data Manipulation Incremental parsing Only process one of the 8 GPS messages GPS uTracker Final Report 62 Set initial coordinates Don t turn off the GPS chip put it into low power mode instead e Direction amp Distance Calculation Calculate the direction only when new data arrives Calculate the direction efficiently Linear approximation of the distance e Data Manipulation Use internal memory whenever possible Use the smallest data types for a given situation Use integers whenever possible Limit the quantity of floating point operations e General Optimizations Use macros instead of subroutines Enable compiler optimization
50. itude altitude and number of satellites At the beginning of the program the chip is told to output only that message to simplify the parsing process When new data arrived it was put in the buffer to be later processed We have two approaches here one was to receive the complete message and then parse it the second was to be parsing the message as it was received We chose the second we parse the data as it is coming This allows us to use the time between characters receptions to process the data To obtain the GPS signal faster approximate coordinates are given to the chip This allows the GPS system to obtain the signal faster Additionally the GPS is never turned off when the device is on to prevent the long wait time needed for the first location output The chip is put into standby state in which it computes the location slowly but does not loose the necessary information for performing fast reception later When new data arrives the destination direction is calculated This calculation is not performed every time because it is a time consuming process floating point operations etc The issue of calculating the direction efficiently is better explained in the theory section here we only give a brief summary Using traditional methods to find the angle between the destination direction and the user orientation a considerably amount of floating operations would be needed The microcontroller we are using is based on an 8 bit
51. le character writing Set the character data Send the command wait_until command finishes End Subroutine Subroutine set_cursor position row col Prepare to send command Set cursor position code Prepare option flag based on row and column Send the command wait_until command finishes End Subroutine The previous code snippets refer many times to prepare send command set command code and send command An example assembly program is shown below CLR EN CLR RS MOV DATA 38h SETB EN CLR EN LCALL WAIT LCD The above code clears the EN input which is necessary to set the command code clear set cursor position etc Then the RS input is clear to indicate this is a command if it were one then the command code will be a character to print The command code is moved into the input ports of the LCD display which in this case is an initialization command Then the EN bit is set to load the command into the LCD and finally it is again cleared to execute the command The wait subroutine waits until the command has executed GPS uTracker Final Report 58 GPS Chip The most complex of the device components is the GPS chip The chip selected for this project is the Sony GXB5210 single GPS chip This chip is a complete implementation of a GPS receiver no external components are needed to make it perform its intended function One of the main aspects of the GXB5210 that influenced in this decision
52. low is the pseudo code to provide this configuration Subroutine configure serial Set SCON to work in Mode 1 with input and output enable Set TH1 to generate 4800 baud rate Set gps baud to 10 Request port 0 update End Subroutine Commands sent to the GPS module through the serial port are ASCII based with parameters All the commands require the system to wait for an echo of the command as a confirmation that the command has indeed been received before allowing another command to be received Main command input will be as follows Subroutine serial command com param Send command through serial port one character at a time GPS uTracker Final Report 59 Wait for command echo before proceeding If echo is not received in some time resend command End Subroutine After configuring the serial port the next step is to configure the GPS Module itself to begin the message output procedure that occurs every second The commands used for the module configuration will be NC which is going to be used to configure the GGA sentence from the National Marine Electronics Association NMEA standard as the single message outputted from the 8 available WLK to set the walk mode as on and CD which will be used to perform a cold start of the chip allowing the beginning of the message outputs Subroutine configure GPS module Send command NC with parameters to set GGA output at 1Hz Send command WLK
53. mplete implementation of a GPS receiver no external components are needed to make it perform its intended function The final hardware implementation added two LEDs and 1 5kQ resistors two limit the current threw the LEDS The LEDs provide the appropriate feedback in order to debug UART signal errors 11 0592 MHz Crystal The crystal interface follows the standard parameters for the 8052 interfacing that are specified in the AT89C51RC2 datasheet GPS uTracker Final Report 23 3 6 Hardware Termination Level The prototype developed in this project has all of the necessary components for it to be a functional device We still wanted more features to be added to the prototype The unit needs to have a backup battery of 3V added to the GPS receiver in order to reduce the time for the receiver to triangulate the initial position The receiver would then be able to have in memory all of the almanac data from the last position it received before it was turned off Another important feature we wanted to add to this prototype is to have the ISP programming hardware integrated By adding this we don t have to take out the microprocessor to have it programmed the programming is done with out any unnecessary handling of the microprocessor This will reduce the opportunity of damaging any of the static sensitive components Figure 12 Prototype GPS uTracker Final Report 24 3 7 Software Plan 3 7 1 General Usage We proceed to describe a typic
54. n appropriately Additionally as the compass becomes imprecise when the inclination is greater than 25 degrees we could use an inclination sensor to detect when we need to modify the input data to decrease the error in the direction information We also wanted to include the programming circuit inside the device so the programming and testing of the system became easier What is currently done is to program the chip then take it out of the programming circuit and put it in the device s circuit which delays the testing procedure Later generations could make the circuit in place Another area that could be improved is power management The system is portable which means it should run on batteries and has to consume the minimum amount of power We have many ideas in this respect of which the first one is to make a backup circuit for the GPS chip The chip has the ability of preserving memory when a little amount of voltage is applied to one of its pins If it preserves the memory when power is not applied to it we could turn it off in the standby mode Remember we don t do this right now because the chip is slow acquiring the signal the first time But if it has the data already in memory it will be faster acquiring the signal after coming out of standby The second idea is to provide the user a mechanism that she could use to control the contrast of the LCD which is one of the devices that consume more power The third would be to cont
55. ntinuous data feedback but doesn t show any significant changes in the output in less than 2 seconds We can conclude that even if the compass needs a continuous data request for direction information it won t be a limiting factor in the timing of the whole system The GXB5210 chip is the only chip that can be considered as a limiting factor in the timing analysis of the whole system The GPS chip can be configured to have a baud rate of 4800 9600 19200 or 38400 It provides an output of 8 different NMEA standard messages with the fastest frequency working at 1Hz each However our system will only use one of these messages to get all the necessary data With an output rate of 4800 baud the chip can keep up to 6 of the 8 different output messages with its fastest frequency of 1Hz That being know we re using the 4800 baud rate as the transmission rate of the serial communication of our system since it is the minimum necessary for it to work and it s the less power consuming option An 11 MHz crystal can be used to generate the appropriate UART frequency of 8052 microcontroller Using mode 1 of the serial communication port the timer TH1 must be set to 244 for us to be able to set the baud rate of our system to 4800 The following are the timing diagrams for the serial communication interface LCD data track and set button operations GPS uTracker Final Report 13 3 3 1 Serial Communication Serial Input Port lt Echo gt S
56. oordinates of Puerto Rico and its surrounding areas ON STATE The device will now automatically start to connect with the Global Positioning System satellites and try to obtain its current location coordinates We suggest that the device is used outside to allow a better communication with the GPS satellites While the device is still looking for connection an X character will appear at the bottom right location of the screen After the device has acquired connection the character will change from an X into a number and the current coordinates will be displayed This number informs the number of satellites to which the system is currently connected The device takes an average time of one to three minutes to connect C On State After the device is connected it s ready to save and track coordinates To save coordinates the device must be in On State From the current coordinates screen the Up and Down buttons are used to scroll through memory can be stored into different locations to later be tracked GPS uTracker Final Report 74 Scroll Up ON STATE Scroll Up ON STATE Scroll Up ON STATE Scroll Up ON STATE Scroll Up ON STATE To save the current coordinates into a memory location press the Up or Down buttons to scroll screens to the screen of the desired memory location The number of the memory location is shown in the upper left corner of the screen The number ranges from 1 to 3 and a sp
57. or 1 5 kQ Resistor 82 kQ Resistor 10k Q Resistor 10 uF Capacitor 0 1 uF Capacitor 33 pF Capacitor 11 05982 Mhz Clock LED Connector FFC FPC 1MM 10POS VERT ZIF Flat Flex Cable 4 Battery Holder AA Duracell MN1500 2850 mAh GPS uTracker Final Report Quantity OA RANANAWAANHAANAFARARAHRP HHH 3 66 5 Cost Analysis Part Unit price Bulk price Minimum quantity ATS9C51RC2 3CSIM 8052 microprocessor 8 46 3 67 1000 Dinsmore 1490 Digital Compass 15 95 9 85 1000 Sony GXB5210 Single Chip GPS 49 72 47 60 100 DMC20434 LCD Display 35 52 20 21 500 Push Buttons 100g Operating Force 0 21 0 19 100 Resistors 1 00 0 25 1000 Capacitors 0 15 0 05 100 Battery Holder 0 93 0 42 100 LM317T Adjustable Voltage Regulator x2 0 83 0 52 500 LM7805 5 0V Voltage Regulator 0 25 0 17 500 CD74HC125E Three State Gate 0 72 0 2394 1000 74LS14DR Inverting Schmitt Trigger 0 55 0 154 1000 Connector FFC FPC IMM 10POS VERT ZIF 1 84 0 64421 5000 Flat Flex Cable 4 3 35 3 35 Totals 119 48 87 32 Note Bulk prices are expected to be lower at final version production because of custom developed ICs and industry special prices The analysis shows that the product has a marketable production price The most expensive parts of the system are the GPS single chip module and the LCD display We believe that these parts can get lower prices
58. ower Switch Display Screen Up Down Buttons Set Button Track Button Battery Socket These are the main components of the uTracker with their functions l coordinate screens The device supports a total of 3 different coordinates that Display screen Is the only output display of the system Presents the On State and Track State screens as well as other information Push Buttons a Up Down Buttons Scroll through the different screens in the On State and Track State b Set Button Used only in On State Stores current position coordinates in selected memory location c Track Button Toggles between On State and Track State Selects stored position coordinates to track Power Switch Turns device on or off GPS uTracker Final Report 73 4 Battery Socket Stores batteries The device requires 5 AA batteries to work Batteries not included B Getting Started To turn on the GPS uTracker place 5 AA batteries in the battery socket and use the power switch After the device is turned on the start up screen will be shown on the display Please allow at least 5 seconds while the device initializes INIT STATE After the initializing is done the device will enter to the On State and will display the initial approximation coordinates These coordinates are latitude 18 N longitude 67 W and altitude 10 meters These values are an initial approximation of the current coordinates and are set according to the c
59. re 22 On State Operating Sequence lesie chy davies sega tbedeendeece rece tealaecs 37 Figure 23 To Stand By Operating Sequence sccsscssscescsscesssessscesescssesssacesnasees 39 Figure 24 Stand By Operating Sequence air iii 40 Figure 25 GPS Low Power Mode Switching ceceeeeccsecceseceseceeeeeeceseceaeceeeaeeeneeseees 4 Figure 26 GPS Power Up Mode Switching cccccccccssecsseceseceeseeeeeceseceeeeeeeeeeeenaeenes 42 Figure 27 Track Mode Operating Sequeira is 43 Figure 28 Destination Direction Calculation Sequence oooconnconocnnccnonnnonconncononononanonncnnnons 45 Figure 29 General Stage Changing Sequeira 46 Figure 30 GPS Data Parsons do das 47 Figure 31 Detailed View of the GPS Data Parsing Sequence oocoooocnncccoonoconoconnnonnncnnnonns 48 Figure 32 GPS Da ta Number Par isis 49 GPS uTracker Final Report 3 1 Introduction The work was based on a simple idea to help people find their cars in the concrete jungle that are today parking lots It has become a common problem of our present society and the purpose of the project was to create a device such that would help to solve it Even though the problem was becoming more and more common no one had thought of doing an electronic solution to this problem However we saw that it was time for such a device to be developed The device would have to be portable low power and capable of location detection through wireless methods The system couldn
60. rol the speed of the microprocessor The Atmel at89c51 has the capability of reducing its frequency of operation without interfering with the serial communication speed We could use the 11 059MHZ crystal to provide the necessary baud rate and internally put the micro to run at a slower frequency For production of the device we think a better user interface is needed Not something at the level of cell phones but something better than we have now We see a user interface with more animations a better menu and more options We also want to display more information about the GPS signal This information could include the quality of the signal the speed at which the user is moving and the current time The topic of time is very important because with GPS we have an atomic clock at our disposition The idea is to update the clock based on the GPS data When the signal is not present we could use the internal timer to update the clock When the GPs signal is acquired again the system will then update the clock to conform to the new GPS data GPS uTracker Final Report 70 The microcontroller we use have for extension an array of counters that can be used to count the number of overflows of the timer 0 This allows us to use these counters instead of the software timers that are currently used to control timed events With this measure we can provide the system with a greater degree of precision than it has right now The microcontroller also allows
61. sabled and the standby count down timer is started In this state the compass is not used it is disabled to reduce power consumption The count down timer will expire in 30 seconds When any of the buttons is pressed the counter is reset If the interval ends the GPS chip is put in the To Standby state GPS uTracker Final Report 38 To Standby State Start Transition Timer Any Button Pressed Transition Time Hapsed Figure 23 To Stand By Operating Sequence The To Standby state is a very simple state The device enters this state temporarily before going into the Standby state If the user presses a button while this state is active the device is switched to the On state If at the end of a small interval of time the user has not pressed any of the buttons the system goes to the Standby state The main idea behind this state is to allow the user to cancel the Standby state This will prevent the microcontroller and the GPS from going into standby The state translates to the system switching to a less power consuming mode that will take a considerably amount of time to start again A screen is presented to the user when the device is in this state so she knows the device is going into standby GPS uTracker Final Report 39 Figure 24 Stand By Operating Sequence GPS uTracker Final Report Standby State Put the GPS in Low Power Mode Disable Serial Communication Disable the LCD Stop Micro Push
62. sues that still need some consideration are only a few The most important issue is the accuracy of the GPS chip while getting the current location The chip does a good job getting the current location with a margin of 20 meters However for some applications this is not enough but can be corrected using mean value algorithms and approximations Also a more precise calibration of the digital compass can be done to allow the system to have a higher and more exact direction calculation We understand that this device has a wide range of uses in different areas of work and that it also can be integrated to be part of a larger system to perform a more specific task This may be only the first prototype of a device that will ultimately have a wide range of applications in society GPS uTracker Final Report 68 7 Future Work The GPS system allows us to implement a great variety of applications For this project the original view was a little constrained The idea was to use the device to help people find their car in the parking lot After some thought we realized that our system had many more applications These applications ranged from helping people lost in the forest to helping you to find your friends location At the end of the semester we finished the development of a device that performs its original functionality it will help you to find your car not at the precision we wanted but enough to be usable In the process we have many compli
63. tion Port 8051 Microprocessor GPS Control Port PO 0 PO 2 Digital Compass Data Port P14 P1 7 Digital Compass C Figure 4 Tracker Block Diagram GPS uTracker Final Report GPS Module with Integrated 3 2 Power Consumption The power consumption of the tracking device is computed with the following devices The analysis takes into account the minimum and maximum power requirements for each of the components Sony GXB5210 Operating voltage 3 1 V 3 7 V Selection of 3 3 V Operating current 50 70 mA 50 mA during tracking 70mA during acquisition Backup Power 3 3V 10 uA Max Power 259mW Min Power during tracking 165 mW Min Power during acquisition 231 mW Max Power during standby mode 0 033 mW Atmel 80C51 Operating voltage 2 7 5 5 V Selection of 3 3 V Operating Current 9 42 mA 11 059 MHz Power Consumption normal mode 31 09 mW Power Consumption idle mode 27 45 mW LCD 4 x 20 Operating Voltage 5 V Operating Current 10mA Power Consumption 50 mW Digital Compass Operating Voltage 5 20 V Selection of 5 V Operating Current 30 mA Power Consumption 150 mW GPS uTracker Final Report 10 The power consumption is calculated for each operating mode of the device The system provides for four different operating modes device off standby device on with track mod
64. to turn walking mode on Send command CD to perform a cold start of the system End Subroutine Other commands that will be used during the system operation will be PLM to put the GPS module in a low power mode in which it will generate less output messages and thus making it less power consuming SR to perform a hot start or a warm start after returning from the low power mode and resuming normal tracking and ATM to get the current time GPS uTracker Final Report 60 3 8 Software Termination Level The device software includes all the main system functionalities They provide all the necessary functions for data acquisition from the GPS receiver chip and the analysis algorithms to provide the system with the distance between the two points Also the system provides 3 memory slots to save the selected coordinates and a stand by mode to help lower power consumption A part of the software that is still being implemented is to create a better algorithm to calculate the distance and direction between the two points Because of the low accuracy of they GPS receiver chip software have to be done to generate a better accuracy using average calculations and other methods Other software functions may be added to change the user interface and provide different functions depending on the application intended for the device GPS uTracker Final Report 61 3 9 Efficiency and Trustworthiness In recent years the aspects of
65. was the simplicity of the system having everything including antenna integrated into one single low power unit Our device is going to be hand held portable and battery powered These characteristics made the GXB5210 the ideal choice since it saved space in our system while also having low power consumption The Sony GXB5210 is constructed upon the Sony CXD2951 chip which works using a simple ASCII protocol that is ideal for simple systems This data is transmitted using serial communication which works well with the 8052 microprocessor UART serial data communication support This device communicates using the serial port It is based on an ASCII command interface The device receives ASCII messages using the serial port and then it responds with the requested information To interface with this equipment we must be able to send characters by the serial port If we can send individual characters then the remaining functionality can be built based on the basic character sending functionality To send the data we must first configure the serial port We ll be configuring the serial port to be used in Mode 1 working at a baud rate of 4800 and with 8 data bits The serial mode 1 uses the Timer 1 to set the baud rate so it must also be configured to produce the necessary baud rate The baud rate of the GPS Module is also configured using the second and third bit of Port 0 which must be set to 10b to set the 4800 baud rate on the GPS Module Be
66. when bought for mass production and that they can be easy acquired from distributors maybe with the possibility of supply contracts GPS uTracker Final Report 67 6 Conclusion After all the analysis was done and the system requirements were all considered the final result is a design that has succeeded in satisfying all the expected needs that the device was required to reach our proposed goals The system uses the Global Positioning System effectively to analyze current position and the software programming stores these values in memory which are later compared and present valuable information to the user using simple but direct algorithms that manage to provide the constant feedback that the user will expect in using a system like this while using a low power microcontroller like the AT89C51RC2 Specific hardware design choices were done to allow the system have a configurable power management options that are switched through the working cycle of the device Also because of the GPS technology properties the system is free of interference while working outdoors and since the position information is calculated using the GPS satellites the system can be considered to be independent of location Finally the user interface of the system was done to be as simple as possible and thus making the device easy to understand and use which allows it to have diverse market options for a wide range of different customers The design is
67. y the system is always checking the GPS signal and updating the screen The screen is updated regularly but not too fast to prevent flashing of the screen Any enabled animation is updated and presented to the user Finally the system parses the part of the GPS message that has been received The GPS parsing is done incrementally As each character is received the parser is already parsing and checking the data for errors This allows the parser to use the time between character receptions to process the information Another approach would be to received the complete message and then parse it But parsing incrementally is much more efficient as it use the processor computing power to the maximum Below is the flowchart of the parsing procedure GPS uTracker Final Report 47 Receives character string quality Figure 31 Detailed View of the GPS Data Parsing Sequence Get the latitude Skip N Get the longitude Skip W Get the of satellites Get the altitude GPS uTracker Final Report The flowchart of the procedure for getting the number values follows YES Add to number buffer Assemble number Next State value Finally this is the GPGGA message used for reference Figure 32 GPS Data Number Parsing SGPGGA 012041 1800 0000 N 06500 0000 W 2 07 01 2 00101 2 M 039 2 M 04 0000 42 The parser starts looking for the character When it

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