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Professor Julian Schmoke - ECT295L“The Road Toward Completion…”ECT295L - Applied Project - Final Report          Thomas de...
Table of ContentsAbstract ...................................................................................................
AbstractThis report is a written documentation and explanation of operation of the work completed during theconstruction, ...
Introduction         It certainly has been an interesting journey. That is, the trip through college on the road towardsmy...
Preparing to Stride…        Week 1        It was during week one when all had begun to really soak into reality. I was exc...
o    1 - female data header (10X2)            o    1 - Nylon Spacer            o    1 - Screw (M 3-10)     A Printed Part...
of the 1490 module into the PCB, I quicklysoldered each pin and trimmed off all ofthe excess lead. A visible bridge waspre...
Being very careful to align pin one with the printed diagram on the PCB itself, (Notch alignment), I staredbriefly at my a...
reading.        After testing and showing my wife my compass and how it worked, I returned to my desk andconnected my Comp...
With the fun of my “playing” with my device had begun to sour, I then turned my attention tothe FlowCode program that was ...
branch is followed through the program, the instruction is skipped and the program follows throughuntil the binary represe...
Within the DISPLAY macro, there is a decision instruction that is conditional upon the value ofthe variable FLAG. If the F...
video cards, I found a card that had a two pin                                                           power connector t...
there might be a short between the two wires because each wire is still covered by the protective outerinsulation. Ultimat...
FYD_5421AS SEGMENT      F    H    E     N     G1   A    L    G2   Decimal                                                 ...
FYD_5421AS SEGMENT      F    H    E     N     G1   A    L    G2   Decimal                                                 ...
FYD_5421AS SEGMENT          F     H     E     N      G1    A    L     G2    Decimal                                       ...
Final Steps…        Week 7        My final week of academics was a week of reflection regarding the weeks that had passed,...
A Well Deserved Rest…        Conclusion        Constructing this circuit was a great deal of fun. Gaining a strong passion...
References             Datasheet Archive (2010). "FYD-5421Ax Datasheet, Circuit, PDF, & Application Note     Results" Retr...
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The Road Toward Completion

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This is what I submitted with my presentation for my final project.

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Transcript of "The Road Toward Completion"

  1. 1. Professor Julian Schmoke - ECT295L“The Road Toward Completion…”ECT295L - Applied Project - Final Report Thomas de Jesus - D03177173 6/1/2011
  2. 2. Table of ContentsAbstract ......................................................................................................................................................... 3Introduction .................................................................................................................................................. 4Preparing to Stride… ..................................................................................................................................... 5 Week 1 ...................................................................................................................................................... 5 Week 2 ...................................................................................................................................................... 6A Few Feet Down the Road… ........................................................................................................................ 7 Week 3 ...................................................................................................................................................... 7Pausing to Read the Map… ........................................................................................................................... 9 Week 4 ...................................................................................................................................................... 9Modifications Along the Way… ................................................................................................................... 12 Week 5 .................................................................................................................................................... 12 Week 6 .................................................................................................................................................... 14Final Steps… ................................................................................................................................................ 18 Week 7 .................................................................................................................................................... 18A Well Deserved Rest… ............................................................................................................................... 19 Conclusion ............................................................................................................................................... 19References .................................................................................................................................................. 20
  3. 3. AbstractThis report is a written documentation and explanation of operation of the work completed during theconstruction, inspection, and modification of the Digital Navigation Board that I, Thomas de Jesus, wasassigned to complete during my attendance of ECT295L under the guidance of Professor Julian Schmoke.The digital navigation board is more commonly described as a “digital compass” and will be referred to,as such, for the remainder of this document.
  4. 4. Introduction It certainly has been an interesting journey. That is, the trip through college on the road towardsmy education. It seems like only yesterday I was “down and out” and desperate for a change. I retired tobed that evening, with an appointment scheduled with Elvis Aparicio, my admissions advisor. I woke upthe next day with a plan. I wasn’t standing still anymore. I was finally moving forward. During my “career” as a DeVry University student, I had imagined along the way about thesefinal moments and speculating as to what the final project might consist of. I’ve had many assumptionsregarding so, including everything from being assigned to build a transistor radio to being assigned tobuilding my own device using whatever parts I had accumulated over the years and based on my owndesign. Now, I find myself at the end of the road. Seven weeks ago, I was introduced to my final project.How fitting that would be a digital compass. Nice! This is just what I need to find my way to my success. So, I began the final steps toward the end of my journey documenting every step along the way.What you are about to read is that documentation of my journey. I hope you enjoy reading my report asmuch as I have enjoyed participating in my final class.Enjoy.
  5. 5. Preparing to Stride… Week 1 It was during week one when all had begun to really soak into reality. I was excited when I hadreceived my little brown box from the school’s online bookstore a week or two before classes hadbegun. Opening the box, I found a small green board inside, along with a bag full of components,including resistors, small capacitors, a microcontroller, a digital display, a 9-volt DC battery connector,and, a weird cylindrical device with pins coming out of it. I had already guessed that it might be acompass, but, I have learned, over the last few years, not to begin jumping into assumptions about whatclasses might require or consist of, too quickly. At the beginning of week 1 my restrained assumptions were confirmed. We were to construct adigital compass device. With my task in hand, I laid all of my parts out on my desk and began toinventory my parts.My ECT295L Compass Kit box contained…:  A 9V Battery and Battery Connector  A Printed Circuit Board  A Cylinder of Solder  2 Bags of components containing: o 2 - ceramic capacitors (10pf) o 2 - monolithic capacitors (1µf) o 2 - ceramic resistors (220Ω, 1/4 W) o 1 - ceramic resistor (10kΩ, 1/4 W) o 1 - SIP resistor network (100kΩ, (8,7)) o 1 - electrolytic capacitor (10µf) o 1 - dual alphanumeric display (FYD-5421-AS) o 1 - PIC Microcontroller (PIC16F72) o 1- 28 pin IC socket o 1 - compass sensor module (1490) o 1 - jumper (1X2) o 1 - shorting jumper o 1 - voltage regulator (5 V) o 1 - Set of rubber feet (3)
  6. 6. o 1 - female data header (10X2) o 1 - Nylon Spacer o 1 - Screw (M 3-10)  A Printed Parts List  All accounted for!Satisfied with my parts inventory, I anxiously awaited my chance to put my compass together. Week 2 It was finally in week two that we began the real technicals of the project. The weeklyassignment was stated to begin assembly and inspection of the compass by first soldering the compassmodule onto the Printed Circuit Board (PCB). Protruding from the bottom of the compass module are 12leads separated in sets of three and they work similar to a transistor, or, even a switch. Encased in the center housing of the compass there is a magnetic sensor that detects the slightmagnetic field that is emanated from the earth’s northern hemisphere, or more specifically, the NorthPole. Once the “needle” of the internal compass-mechanics transitions over, or, stops over, atransistor/directional set within the compass, the analog output of electrical current travels into themicrocontroller input(s). Analog to digital conversion is done by the PIC16F72 (Microchip TechnologyInc., 2005) microcontroller and a binary output results from the outputs of the microcontroller. Thisoperation will be defined in this later in this document. The leads for the 1490 Digital Compass Module are very tiny. After allowing my soldering iron toheat up, and after properly tinning the tip of it, I was ready to test my recently-found skill of soldering. Ipreviously soldered components to a PCB during an earlier course while constructing a small power-supply unit, but, the leads of the compass module are exceptionally small and it seemed fitting that thiswould be the first component installed. After first trimming the leads un-evenly to simplify the insertion
  7. 7. of the 1490 module into the PCB, I quicklysoldered each pin and trimmed off all ofthe excess lead. A visible bridge waspresent at first, however, it was easilycorrected and the short was opened. After feeling satisfied with mywork, I began to measure the reverse sideof the PCB where the compass sensor wasinstalled to test for shorted or, bridged connections. Most of the measurements taken were as expected(Infinite Ω indicating an OPEN result), however, while confirming and testing the connections on the PCBwith my test leads reversed, the measurements were extremely incorrect (Approximately 0.4Ω) andshould have measured around 290kΩ (Approx). After some time of trying to decide what had gonewrong, I discovered that I was in fact testing my compass PCB with the ground incorrectly assumed.Correcting this by measuring from the correct ground location and re-performing all of themeasurements, I was presented with the expected results (Approximately 295kΩ). Repeating these teststo determine the connectivity between the remaining compass leads and respective grounds, Imeasured satisfactory results each time, indicating a good installation of my compass module.A Few Feet Down the Road… Week 3 Feeling highly confident by my previous week’s success, I was eager to complete the rest of mynavigation board. The rest of the components were comparably easier to solder to the PCB, rather thanthe 1490 compass sensor itself, and I soon had a nearly completed digital compass before me. Afterfinishing my solder work by affixing my 9-Vdc battery supply cable/connector, I carefully inserted thePIC16F72 microcontroller into the matching microcontroller socket I had previously soldered to the PCB.
  8. 8. Being very careful to align pin one with the printed diagram on the PCB itself, (Notch alignment), I staredbriefly at my accomplishment. Soldered to the back of my PCB is the data header that connects allows for a user to program the PIC16F72 microcontroller using a programming device, such as, a Multi-Programmer board. The compass attaches to the data bus header of the multi-programmer board which provides communication amongst the compass microcontroller. The unfortunate flaw is that since the data header is only placed on the back-side of the PCB, the compass lays at a severe angle. This eliminates the compasses functionality while it is laying on a surface. Included with my kit was asingle screw and nylon spacer which I would assume is intended for leveling the compass. Confusingly,the single screw and plastic spacer are useless and still cause the compass to be uneven when placed ona level surface. The included rubber feet also offered to assistance as each pad is very thin and provideno elevation. Setting the screw, spacer, and rubber feet aside, I connected my 9Vdc battery and placed the small black power-jumper over the On/Off jumper pins and checked for any out-of-the-box functionality. To my satisfaction, the LED driven display ignited with life and the letter N was displayed indicating the orientation of the compass as being north. During my extensive testing of the compass, I was able to determine at that time that the module would “stick” on a particular direction if the compass is not perfectly level when trying to get a directional
  9. 9. reading. After testing and showing my wife my compass and how it worked, I returned to my desk andconnected my Compass to my multi-programmer board and downloaded the standard version of thecompass program that was pre-written in a program called FlowCode. After briefly examining theFlowCode program for curiosity’s sake, I compiled the program into a HEX file, which is a file readableand uploadable to the microcontroller connected to the compass PCB. After quickly loading the HEX file into aseparate program called PPPv3, I connected mymulti-programmer board to my USB cable andsent the file to the compass microcontroller.After a brief blink on the display and a successmessage generated by PPPv3, the compass reallydisplayed no change in functionality whichindicated the program had been uploaded andwas working correctly.Pausing to Read the Map… Week 4 At this point in my journey, I had completely assembled and programmed the digital compassand was very pleased with its operation. A few walks around the backyard, the house, and following mywife while she cleaned, would correctly display the orientation of the compass, in my hand, in all eightnavigational directions (Each direction displayed as N, S, E, W, NW, NE, SE, SW).
  10. 10. With the fun of my “playing” with my device had begun to sour, I then turned my attention tothe FlowCode program that was instructing my device to function. Upon opening the FlowCode programI had already noticed that the entire program was encased in a “loop while” condition, causing theprogram to effectively loop in operation once the program has been initialized. In the case of my digitalcompass, the simple act of applying power and placing the on/off jumper in the ON position, sets theprogram to run immediately, beginning with the definition of variables, in the calculation instruction andpertinent to the program, and then into the infinite loop. That would definitely explain why there is no need to press a button to get a directional reading. In the next input condition a variable is defined as NEW_DIR which will be utilized by the microcontroller as a binary input. This binary input determines the direction the top of the PCB is facing. In other words, the NEW_DIR variable is set by the compass sensor’s output which is associated with its orientation. The next conditional argument in the FlowCode program is a program macro that actually isintended to prevent the display from flickering, and also, to prevent the display from skipping adirection while it is being rotated. This is essentially a repeated test to see if there has been any changein direction to prevent such flickering. The next instruction in line is the first of eight decision (Yes/No) instructions to help determinethe measured input from the compass sensor into the microcontroller. As mentioned before, eachdirection causes a binary representation on the inputs of the microcontroller. If the input is read by themicrocontroller as the binary number 0011 the internal program correctly interprets this as the decimalnumber 3, which in turn would prompt a YES answer to the decision instruction for North East. If the NO
  11. 11. branch is followed through the program, the instruction is skipped and the program follows throughuntil the binary representation of the input reflects a YES response. Once a decision has been determined as YES, the real transfer from input to output begins. TheYES branch of the decision instruction continue to a calculation condition that sets the decimal value ofthe required binary representation to illuminate the tiny LED segments within the alphanumeric display.Further investigation of the datasheet (Datasheet Archive, 2010) for the FYD-5421AS display, Idiscovered that each LED is assigned a letter code that specifies which pin-to-segment similarities causefor each direction to be defined as an N for north, etcetera. Additionally, each digit is segmented similarly over two different ports, port B and Port C. Byutilizing the variables FIRST_D_1, to manipulate port B (IC outputs B0-7), and/or, FIRST_D_2, tomanipulate port C (IC outputs C0-7), the LED’s segments for the first alphanumeric digit will light upaccording to the decimal/binary output. Similarly, using the variables Second_D_1, for port B andSecond _D_2 for port C, the segments for the second digit will display according to the binary outcome. I was pleased that it was all making sense to me in some slight way. Although I had someunderstanding of the overall program operation as it was written, I would not discover the editablevariables that would change the displayed output of the compass until a later week. Finally, I hadfollowed the compass program to the final (functional) instruction that would happen to be the DISPLAYmacro. This macro is the work behind the resulting calculations performed when a decision branch hastaken a YES path through the directional calculation variables.
  12. 12. Within the DISPLAY macro, there is a decision instruction that is conditional upon the value ofthe variable FLAG. If the FLAG variable is determined to be true or false, the YES or NO branch isfollowed and a calculation instruction on each branch, along with two sandwiched output instructions,allows for the program to light the segments on either the first alphanumeric digit, or the second digit.Earlier there was mention of the definition of variables that were set before the program loop wasinitialized. Among these variables is the FLAG variable and is initially set to 16 which actually will causethe second digit to be read first as decided by the decision instruction. During each branch and centeredbetween the port outputs, the variable FLAG is alternated between 16 and 32 causing each branch to beexamined by the program as necessary to display both display digits. The Flowcode program left so much to be explained! Nevertheless, it was understood by me atthat point in time and I was tremendously excited to see which direction my project would continuetake me.Modifications Along the Way… Week 5 With everything moving smoothly and my assembled and programmed compass kit stillperforming to my delight, I turned my attention to the next phase in learning, which would happen tobe, the alteration of the FlowCode program and additional wiring to the compass PCB. It was made clearthis week and confirmed through further investigation of the compass schematic, that three of theoutputs of the microcontroller were, in fact, not connected to any of the LED segment pins on the LEDcomponent. Before tackling the unconnected pin issue, I needed to fix the battery cable a second time. Whiledemonstrating my compass for family and friends, I found that the wires are really week and whenhandled too frequently, will break loose from the PCB. And so, digging through my box of spare and old
  13. 13. video cards, I found a card that had a two pin power connector that was used for the fan. After removing the solder from the card holding the plastic power connector and clipping the connector from the fan wires, I removed the solder from the V supply terminals of my board and did my best to open the existing holes that were once there. With a little sweat and after some slight bending, the board-side of the fan connectorwas soldered in satisfactorily, and stable. Then, I soldered the wires from the clip of the connector to thewires of the battery cable for my compass. This in fact left the wires for the battery too long, in myopinion, and so, using the smallest standard screwdriver in my arsenal, I was able to work the pins out ofthe connector that joined to the old fan wires, remove the old wire and solder the internal connectorsdirectly to the battery wire, and then, firmly inserted the connector back into the plastic connectorhousing. After all was completed, I checked the power levels to ensure that there were solid connectionsthrough the connector and my measurements were exact. The 9.23 Vdc measured directly from thebattery was also measured at the power jumper, and the back-side of the V connectors on the PCB.Finally, I was ready to “connect-the-bits”. This posed as somewhat of a challenge for me at first. Looking at the schematic and throughdatasheets for the PIC16F72 and the FYD-5421AS display component, I was able to determine which pinswere in fact not connected, and where they should be connected to complete a connection to theremaining LED segments. Working essentially from top-to-bottom in relation to the microcontrollersymbol of the compass schematic, versus, the display symbol of the datasheet for the displaycomponent, I had predetermined and visualized which pins to connect on the back of my compass PCB. Fortunately, I was able to correctlyconnect each of the unconnected pinsaccordingly. Unfortunately, after placing thewire jumpers where I would end up doingso, I caused two of the wires to cross overeach other. The concern is very little that
  14. 14. there might be a short between the two wires because each wire is still covered by the protective outerinsulation. Ultimately, I had connected microcontroller pin 14, to FYD-5421AS pin 4 (yellow wire),microcontroller pin 13 to FYD-5421AS pin 15 (white wire), and finally, microcontroller pin 11 to FYD-5421AS pin 4 (red wire). Still satisfied with my progress, and my compass still functional with the originalcompass program, I moved forward and began to alter the FlowCode program. Week 6 This would be the last week I had spent completing my compass modifications. I began thisweek with some confusion regarding the standard compass FlowCode, and the modifications that wouldchange the N, S, etc, representations of navigational direction to instead display arrows that wouldconsistently represent north. It was over the course of the last couple weeks that I had discovered thatthe display segments were a binary representation, converted to a decimal value, and that this could becompleted by changing the decimal values in the decision instructions for the variables FIRST_D_1,FIRST_D_2, SECOND_D_1, and SECOND_D_2 variables. The tables below outline the changes I hadimplemented to each decimal value, including a graphic of each arrow the values would display. Onlyone alphanumeric digit is displayed in my examples due to the fact that both alphanumeric digits, pereach direction, show identical representations of arrows.FYD_5421AS SEGMENT F H E N G1 A L G2 Decimal ValueIC PORT B B7 B6 B5 B4 B3 B2 B1 B0BINARY OUTPUT FROM IC 0 0 0 1 0 0 1 0 18FYD_5421AS SEGMENT D C CC1 CC2 M J B K Decimal ValueIC PORT C C7 C6 C5 C4 C3 C2 C1 C0BINARY OUTPUT FROM IC 0 0 0 0 1 1 0 0 12 NORTH
  15. 15. FYD_5421AS SEGMENT F H E N G1 A L G2 Decimal ValueIC PORT B B7 B6 B5 B4 B3 B2 B1 B0BINARY OUTPUT FROM IC 0 1 0 0 0 0 1 1 67FYD_5421AS SEGMENT D C CC1 CC2 M J B K Decimal ValueIC PORT C C7 C6 C5 C4 C3 C2 C1 C0BINARY OUTPUT FROM IC 0 0 0 0 1 0 0 0 8 NORTHEASTFYD_5421AS SEGMENT F H E N G1 A L G2 Decimal ValueIC PORT B B7 B6 B5 B4 B3 B2 B1 B0BINARY OUTPUT FROM IC 0 0 0 0 1 0 1 1 11FYD_5421AS SEGMENT D C CC1 CC2 M J B K Decimal ValueIC PORT C C7 C6 C5 C4 C3 C2 C1 C0BINARY OUTPUT FROM IC 0 0 0 0 0 0 0 1 1 EASTFYD_5421AS SEGMENT F H E N G1 A L G2 Decimal ValueIC PORT B B7 B6 B5 B4 B3 B2 B1 B0BINARY OUTPUT FROM IC 0 0 0 1 0 0 0 1 17FYD_5421AS SEGMENT D C CC1 CC2 M J B K Decimal ValueIC PORT C C7 C6 C5 C4 C3 C2 C1 C0BINARY OUTPUT FROM IC 0 0 0 0 0 1 0 1 5 SOUTHEAST
  16. 16. FYD_5421AS SEGMENT F H E N G1 A L G2 Decimal ValueIC PORT B B7 B6 B5 B4 B3 B2 B1 B0BINARY OUTPUT FROM IC 0 1 0 0 0 0 0 0 64FYD_5421AS SEGMENT D C CC1 CC2 M J B K Decimal ValueIC PORT C C7 C6 C5 C4 C3 C2 C1 C0BINARY OUTPUT FROM IC 0 0 0 0 1 1 0 1 13 SOUTHFYD_5421AS SEGMENT F H E N G1 A L G2 Decimal ValueIC PORT B B7 B6 B5 B4 B3 B2 B1 B0BINARY OUTPUT FROM IC 0 1 0 0 1 0 1 0 74FYD_5421AS SEGMENT D C CC1 CC2 M J B K Decimal ValueIC PORT C C7 C6 C5 C4 C3 C2 C1 C0BINARY OUTPUT FROM IC 0 0 0 0 0 1 0 0 4 SOUTHWESTFYD_5421AS SEGMENT F H E N G1 A L G2 Decimal ValueIC PORT B B7 B6 B5 B4 B3 B2 B1 B0BINARY OUTPUT FROM IC 0 1 0 1 1 0 0 1 89FYD_5421AS SEGMENT D C CC1 CC2 M J B K Decimal ValueIC PORT C C7 C6 C5 C4 C3 C2 C1 C0BINARY OUTPUT FROM IC 0 0 0 0 0 0 0 0 0 WEST
  17. 17. FYD_5421AS SEGMENT F H E N G1 A L G2 Decimal ValueIC PORT B B7 B6 B5 B4 B3 B2 B1 B0BINARY OUTPUT FROM IC 0 0 0 1 1 0 0 0 24FYD_5421AS SEGMENT D C CC1 CC2 M J B K Decimal ValueIC PORT C C7 C6 C5 C4 C3 C2 C1 C0BINARY OUTPUT FROM IC 0 0 0 0 1 0 0 1 9 NORTHWEST Having this information firmly in hand, I began to change the variables using the values for PORTB as the decimal value for the variable FIRST_D_1 and PORT C as the decimal for the variable FIRST_D_2.This indeed changed the left alphanumeric display to display an arrow. Again, just as before, I alteredthe variable for the SECOND_D_1 using the decimal value for PORT B and SECOND_D_2 wasprogrammed with the decimal value for PORT C. Once all of the values in each of the calculation boxes had been changed, I was able to directlyprogram the microcontroller on mycompass using the same method as I hadused when programming it with thestandard compass FlowCode program.Once the upload was completed, Iremoved my compass from theprogrammer board and connected the9Vdc battery to my compass. Success!Each direction was correctly displayingthe arrow I had indicated by my work.
  18. 18. Final Steps… Week 7 My final week of academics was a week of reflection regarding the weeks that had passed, andthe events that had occurred. Once all had been completed, the functionality became very clear. Oncepower has been applied, the voltageis carried through the power supplycircuit and output through the Vddsupply which activates themicrocontroller and compass sensor.The internally saved program beginsto run by first setting variablesimportant to the program’sfunctionality. The needle within thecompass sensor module passes overany combination of three terminalsand a switch-like result occurs that activates a signal int the inputs of the microcontroller (A0…A3). Asdetermined by the decimal values saved into the FlowCode program, the binary/decimal output is sentthrough the output pins of the microcontroller which are then transmitted to the LED display. Eachoutput of the PIC16F72 microcontroller is connected to each LED segment of the FYD-5421-AS displaymodule. This signal then illuminates the indicated led segment, forming the desired output, which is anycombination of alphanumeric characters, including some symbols. A resistor network is used to regulatethe current into the microcontroller and the compass module.
  19. 19. A Well Deserved Rest… Conclusion Constructing this circuit was a great deal of fun. Gaining a strong passion for computers andelectronics at a young age, I had always been extremely fascinated with the science of electricity. Fromthe simple powering-on of my home computer, to the detailed 3D graphics displayed, the circuitry thatprovides the means is the most incredible discovery of all time, in my opinion. I am proud of theaccomplishments I have achieved, with the help of DeVry, and I know that the road before me towardsmy future has widened and expanded with many new possibilities. Though this class is over, and I have reached the end of this academic road, I realize that this isreally only a short rest. In the very near future I will continue to learn more about the science ofelectricity and further examine the compass I had constructed, along with a power-supply I had builtbefore, and just see how far I can explore my favorite scientific realm. Future improvements mightinclude a larger microcontroller, along with a larger display that would display larger words to associatewith each direction. I also plan to eventually encase my compass in a solid housing that would serve toboth protect the circuits inside, and provide ease of use when holding in the palm of my hand. Please allow me to take this time to thank you, the reader, for reading my final project-report.
  20. 20. References Datasheet Archive (2010). "FYD-5421Ax Datasheet, Circuit, PDF, & Application Note Results" Retrieved June 18, 2011, from http://www.datasheetarchive.com/FYD-5421Ax- datasheet.html Microchip Technology Inc. (2005). “PIC16F72 Data Sheet: 28-Pin, 8-Bit CMOS FLASH Microcontroller with A/D/ Converter” Retrieved June 18, 2011, from http://ww1.microchip.com/downloads/en/DeviceDoc/39597C.pdf

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