Alphanumeric LCD infrared control via computer`s parallel port
Contents
1. P2 1 AD9 vss 21 P2 0 AD8 Fig 1 6 AT89C51ED2 Pin Configuration Courtesy of ATMEL 10 1 1 5 EDE Parallel Serial Transceiver IC This integrated circuit as it name explains is a device that changes parallel data into serial and vice versa It works with standard TTL voltage 5 volts and has the capability of converting words of 8 bits The circuit is intended to be used logging data to a PC or control hardware via the PC ports like in this project s case Itis BAUD selectable so it can operate at both 2400 and 9600 BAUD speed It can work either as a half duplex transmitter half duplex receiver or half duplex bi directional transceiver The circuit encapsulation is shown in figure 1 7 EDE300 Data Direction Output Latch 1 birt XMIT 18 Serial Transmit 0 2400 1 9600 ei BAUD Rcv 17 Serial Receive O Local 1 Host SS Mode osc1 16 Oscillator Connection Connect to 5V DC 4 5V OSCH 15 Oscillator Connection Digital Ground 5 GND 5V 14 Connect to 5V DC Data I O Pin O ke DO Di 13 Data I O Pin 7 Data I O Pin1 7 D1 D 12 Datal O Pin 6 Data I O Pin 2 a D2 D5 In Datal OPin5 Data I O Pin 3 dE D3 D4 10 Datal O Pin 4 Fig 1 7 EDE300 Pin Configuration Courtesy of ELAB Digital Engineering Inc 1 1 6 Hitachi LMO16L Alphanumeric LCD module The LMO16L is an alphanumeric Liquid Crystal Module that can display two lines of 16 characters each No backlight is provided with this model It uses Super2. because these are secure operative systems that do not allow the access to memory locations so easily Many workarounds for this issue have been proposed The one used and tested for the present project is the use of the UserPort program Userport is a kernel mode driver for Windows NT 2000 that gives access to the users to the I O ports With this the direct hardware access from an executable file can be done just like under a Windows 98 enviroment The driver can be used for the following purposes e To run software on Windows NT 2000 that normally only runs on Windows 95 98 ME e To easily access hardware like the parallel port and other I O ports D cnarrcvene o BR Char Rev exe has encountered a problem and needs to close We are sorry for the inconvenience ser If you were in the middle of something the information you were working on e sent might be lost Dalarna 2006 For more information about this error click here Debug Port LPT1 0x378 selected Next character to send Carriage Return char to terminate gt gt g Fig 2 13 Error message The way to use the UserPort software is by copying the UserPort sys file provided in the kit to the path Windir System32 Drivers Then the UserPort exe file should be executed Figure 2 14 shows the screen that is displayed 39 MM UserPort 1 0 Tomas Franzon c 2001 SEE All User Mode Processes Grant List Through UserPort
3. 18 Ground 19 Ground 20 Ground 21 Ground 22 Ground 23 Ground 24 Ground 25 Ground Table 2 1 Pins used in parallel port 2 1 2 EDE 300 and Infrared Light Emitting Diode The EDE 300 integrated circuit is very important for the proper function of the project since it is the one that takes charge of coding the parallel data received from the PC s port and then converts to a serial data After the input parallel data has been received it is send as a serial data to a power stage part before it is send via the Infrared LED to the other part of the circuit Since the transmission speed is not a critical matter for this project the maximum data sending transfer rate was selected 9600 bps The circuit has the option of both 9600 and 2400 bps Two EDE 300 circuits are used in the project one to serialize the data received from the parallel port and the second one that does the opposite capturing the data from the IR receiver and sending it as a parallel word to the microcontroller Both circuits are configured to work in Local Control Mode which means that they are constantly scanning for new data to be converted either to serial or parallel depending on the side of the IR transmission the circuit is working This means that the MODE pin third is set to a logic O zero or low voltage The baud rate as explained earlier is set to 9600 None parity 8 bits 1 stop bit by placing pin number 2 Baud Rate to a logic 1 one
4. Grant List Enter Grant Intervall Ge Ox3fF a Grant Intervall 0x000 0x3ff Defaults Defaults Driver UserPort SYS Start Update Stop 2 es e Fig 2 14 UserPort initial screen After UserPort is initialized a range of user addresses must be provided For the scope of this project the memory addresses are 0x0278 0x0378 and 0x03BC corresponding to each one of the possible parallel ports in a computer Two options can be followed now The first one is to open all the range of port addresses from 0x0277 to Ox03BD which will cover even more than the needed addresses For security reasons it is recommended just to add the ranges of the known ports being them 0x0277 0x0279 0x0377 0x0379 and Ox03BB 0x03BD as it is shown in figure 2 15 E UserPort 1 0 Tomas Franzon c 2001 AE All User Mode Processes Grant List Ene SS AUserPort Grant List Enter Grant Intervall ES Grant Intervall 0x000 0x3ff 0x0388 0x038 Dl al Add a 277 279 SES 377 379 E Defaults Defaults Driver UserPort SYS Start Update Stop st Exit Fig 2 15 Adding the addresses to UserPort After the proper addresses have been established the program should be started by clicking on the start button When the program is running the software created for this project will run correctly 40 3 Results For the final construction of the whole device the whole project was built in eac
5. 3 If something else is typed the program will notify the user as it can be seen on figure 2 9 and then it will prompt for a valid option There is no timeout or maximum number of tries so if the software must be stopped the window should be closed 36 Dis har Rey 2 Exp EE Welcome to the program that will send data to LCD The way this program works is by prompting the user to type in the desired character then it will be sent to the LCD connected in the remote location The program will terminate when Carriage Return is sent as character Programmed by Hector Jaramillo Cantu Hogskolan Dalarna 2666 9939999999909 9999999000008 NEE EEN EEN Please define define which parallel port be used 1 2 3 gt gt w INVALID SELECTION PLESE TRY AGAIN Please define define which parallel port be used 1 2 3 gt gt m Fig 2 9 Invalid selection banner When a valid option has been selected the program also confirms both the address and the port number that will be used through the whole program It is important to notice that once this port has been selected it cannot be changed until the program is closed and started again Figure 2 10 shows the example of a valid choice and how the program confirms the port address Ar har Rev XO PODOODODODODODODOODODODODODODODE Welcome to the program that will send data to LCD The way this program works is by prompting the user to type in the desired character then it will be
6. Twisted Nematic Liquid Crystal and the way of driving is via passive matrix It only needs one 5V power supply and the characters are displayed in gray color The 14 pins needed for control are shown in figure 1 8 Something that is important to mention is that the main controller is the Large Scale Integrated LSI HD44780U built in the module Also the HD44100R LCD driver is mounted as an aid for the electronic driving of the module A more detailed description of these driving circuits will be provided in the following sub sections 11 INTERNAL PIN CONNECTION L Instruction code input H Data input H Data reed LCD module gt MPU L Data write LCD module MPU Data bus line Note 1 2 13 Joe Cre osr ur Fig 1 8 Pin connection for the LM016L module Courtesy of Hitachi 1 1 7 HD44780U LCD Controller Driver The HD44780U is a dot matrix liquid crystal display controller and driver Large Scale Integration circuit able to display alphanumerics Japanese kana characters and symbols It can drive a dot matrix either under 4 or 8 bit logic One single chip can display up to one 8 character line or two 8 character lines Its character generator ROM can generate up to 208 5x8 dot character fonts and 32 5x10 dot character fonts for a total of 240 different character fonts It uses a low power supply TTL compatible which makes it suitable for battery powered applications and low power consumption Some of the product f
7. electrons go from the N type material into the P type one This movements cause energy to be released and this energy can be photons All the diodes release photons but the human eye cannot see all of them because this depends on the different photon frequency The Visible LED VLED is the kind that is formed with materials where the material gap is wide enough to determine a certain photon frequency and therefore can have different colors as well Something important is also that LED s are constructed in a certain way that the most number of photons are released Also the LED encapsulation is constructed in a specific way so the produced light is oriented to a certain place as figure 1 3 shows in a diagram Fig 1 3 LED construction diagram Courtesy of HowStuffWorks Inc When a LED is forward biased the electrons that cross the PN material junction from the n type material and travel to the holes of the p type one When the recombination takes place the electrons that have recombined release energy in the form of light and heat Electroluminescence is the process that describes when a large exposed surface area on one layer of the semiconductor material permits the photons to be emitted as visible light Gallium Arsenide GaAs LEDs project infrared radiation while Gallium Arsenide Phosphide GaAsP show yellow or red light and Gallium Phosphide GaP produce red or green light LEDs emit light as a reaction to an applied fo
8. gt A Character A sent succesfully Next character to send Carriage Return char to terminate gt gt Fig 2 11 Character sending and confirmation The program will go on asking for characters to be sent to the port until the character of carriage return is sent which will indicate the program to terminate This means that when the program requests for a character the user should hit two times in a row the enter key When this is done a banner explaining the ending of the program will appear and then one last key press will be requested to close the window Figure 2 12 illustrates this procedure of x INVALID SELECTION PLESE TRY AGAIN Please define define which parallel port be used 1 2 3 gt gt 1 Port LPT1 8x378 selected Next character to send Carriage Return char to terminate gt gt A Character A sent succesfully Next character to send Carriage Return char to terminate gt gt g Character g sent succesfully Next character to send Carriage Return char to terminate gt gt Thanks for using this software Press any key to finish Fig 2 12 Program ending 38 2 4 1 Special considerations The present program is intended to work on Microsoft Windows operative system based personal computers If the computer is running Windows 95 98 the program will work without any problems at all When a version of Windows NT 2000 XP runs the program an error is produced shown in figure 2 13
9. important and useful tool for data transfer since its introduction back in the early 1980 s It provides enhanced speed compared to its predecessor the serial port up to theoretically 5 times faster The history of the parallel port goes back to the times when Centronics a top printer developing company introduced what is now called Standard Parallel Port which was a unidirectional port used to connect the printer to the computer After this time IBM released the PS 2 line of computers which included a bi directional port with 8 wires and a transfer rate of 150KB sec and above The people in IBM developed a 25 pin connector DB 25 which was able to send 8 bits of data at the same time This led to a new interest in the companies in releasing products that would take full advantage of the port capabilities Furthermore the companies Intel Zenith and Xircom created a new standard called Enhanced Parallel Port which can transfer information at rates of 1000KB sec This new standard was intended to be used with other devices rather than only printers such as storage devices Microsoft also released after another standard called Enhanced Capability Port which provides a transfer rate of up to 2000KB sec The IEEE released in 1994 the IEEE 1284 standard which includes the specifications for EPP and ECP devices that are needed to fulfill in order to make them work Most of the computers auto detect the working mode Tables 1 1 and 1 2 s
10. mounted on the LCD module The ports connected from the AT89C51ED2 to the LCD module are the complete PORT 1 as the data byte and pins P3 5 P3 6 and P3 7 as the signals of R W RS and EN respectively The section for the schematics will illustrate how the physical connections are achieved 21 The first task that it performs after powering up is to initialize the display sending the corresponding signals as the HD44780U datasheet explains and which are shown in figure 2 3 This routine is performed to ensure that the proper initialization is done according to the supply voltage First on DB4 or DBS a high signal is sent and a wait of more than 4 1 milliseconds should be done After waiting the same signal is sent again but after the wait should be of more than 100 microseconds After that the last initialization steps explained in the next paragraph are performed Power on Wait for more than 15 ms Wait for more than 40 ms after Vog rises to 4 5 V after Voc rises to 2 7 V 7 RS R WDB7 D80 DB5 D84 DB3082 DB1 D80 SE cannot be checked before this instruction 0 0 0 0 alc N ee Function set Interface is bits long Wait for more than 4 1 ms R WDB7 DB6 DBS DB4 DB3 D82 DB1 D80 SE cannot be checked before this instruction oo 0 1 IA A Function set Interface is bits long Wait for more than 100 ys RS RWDB7 086 DBS D84 DB3D82DB1D80 BF cannot be checked before this instruction 0 0500 4 4 200 908 Fu
11. of logic abstraction The circuit layout can be seen in figure 2 5 The data flow starts from the infrared reception unit that captures the data sent from the other circuit Then it is transferred serially to the EDE300 which is configured as a serial to parallel transceiver by having the Dir Latch pin 1 set to Vcc 5V This device then takes care of sending the data as a parallel word to the AT89C51ED2 microcontroller As it was explained before the AT89C51ED2 takes care of sending the proper signals to the HD44780U LCD controller mounted on the alphanumeric LCD The fact that many LCD modules use this driver gives the whole unit a big shot in portability so in case a different module wants to be used it can be replaced and the whole system will still work Some details that are considered in the wiring of the AT89C51ED2 is that the PSEN and the ALE pins are not connected since all the code is stored without the use of any external device memory Also the EA enable pin is set correctly as the microntroller needs to work in order to operate the LCD module properly 24 Finally it is important to mention that a push button is added to the RST pin of the device in case the microcontroller is needed to be reset 25 Fig 2 5 Receiving circuit 26 2 3 Source code The present subsection will provide the source codes used both for the user interface in the computer and for the microcontroller Then an explanation of the different d
12. or high voltage This two signals are set equally to both circuits The signal that changes from one to another is the one of the first pin Data Direction Latch which refers of the data flow direction This means that for the circuit that receives the parallel data and converts to serial the pin should be connected to logic 0 zero and viceversa As it is clearly stated in the datasheet the connections should be made taking special care not to send data to 18 the output terminals depending on each case Table 2 2 summarizes the pin configuration for each one of the two EDE 300 used Pin name number Parallel to serial Serial to parallel Data direction latch 1 Low 0 High 1 Baud Rate 2 High 1 High 1 Mode 3 Low 0 Low 0 5V in 4 High 1 High 1 GND 5 Low 0 Low 0 Data I O 0 6 Input Output Data I O 1 7 Input Output Data I O 2 8 Input Output Data I O 3 9 Input Output Data I O 4 10 Input Output Data I O 5 11 Input Output Data I O 6 12 Input Output Data I O 7 13 Input Output 5V in 14 NC NC Osc2 4MHz OSC 4MHz OSC Osc1 4MHz OSC 4MHz OSC Serial Rev NC Input Serial Xmit Output NC Table 2 2 EDE 300 circuits signals 2 1 3 Power Stage This is an important part of the circuit added to enhance the performance of the infrared transmission The output from the EDE 300 might not be enough to have an strong signal that wil
13. signal ace 80 x 8 bits register driver Address 7 counter 40 bit 40 bit Segment shift atch signal register circuit driver Input a Data 1 output gt register buffer DR LCD drive voltage Busy T selector flag Character Character generator generator RAM ROM CGRAM CGROM 64 bytes 9 920 bits VV Paralle serial converter e and attribute circuit Cursor and blink controller VI V2 V3 V4 V5 Fig 1 8 HD44780U Block Diagram Courtesy of Hitachi 13 As it was explained in the description this circuit controls the dot matrix providing the necessary driving waveforms for the Liquid Crystal This signals consist of 16 common signal drivers and 40 segment signal drivers Something that is interesting for the scope of this project is the use of the Character generator ROM CGROM The CGROM generates the character patterns from 8 bit codes store a table that corresponds to the ASCII table 1 1 8 HD44100R LCD Driver with 40 channel outputs This integrated driving circuit is also mounted on the LMO16L LCD module and it provides an aid to the HD44780U The device has two sets of 20 bit bi directional shift registers 20 data latch flip flops for data storage and 20 LCD driver circuits The HD44780U sends the serial data which is then converted into parallel and the supplied to the display in the proper waverforms It is a general liquid crystal display driver that can drive static o
14. the chosen resistors worked good as well As a second part of this test the IR receiver was tested parallel since it was receiving the signals from the encoding IR LED An Oscilloscope was able to determine that the proper signals were being received 3 3 AT89C51ED2 debugging After the previous tests were accomplished the code for the microcontroller was developed The final approach was to achieve an Intel HEX file in order to be able to put the set of instructions into the chip The compiler used was the student 41 version of Keil uVision3 With this compiler also different debugs to simulate the Input and Output data were performed In the end the HEX file was created and programmed into de AT89C51ED2 with the proper device 3 4 Final assembly The final stage was to wire all the components together Test boards were used with cable to wire everything as in the schematic and a 5 Volt power source for each one of the parts since it is the power needed to drive the circuits There were some problems encountered in the first approach as expected since some of the boards were not wired correctly Therefore a multimeter was used in order to follow each one of the cables until the problem was found and solved After this was fixed the system was tested again and it was almost fully functional but there was a small problem with the timing coming from the user interface program Therefore the delay method was modified in orde
15. using this software printf n nPress any key to finish n getch Method presenta that displays the banner of the program void presenta void PETE LC NTE ere RRR IRI RK e IIE IIR IR IRIE I I IR AR RK AK KE KEKKKKKKKKKKKKKEN ELE nee e RRR ee er ee RIE IIR e re re er ere IK KEKKKKKKKKKKKKKENW printf nk Char ROV EE er AREER IR MY A printf AnXtWelcome to the program that will send data to LCD printf n tThe way this program works is by prompting the user printf Anlitto type in the desired character then it will be sent printf Anitto the LCD connected in the remote location printf AnltThe program will terminate when Carriage Return is sent as character printf AnltProgrammed by Hector Jaramillo Cantu Hogskolan Dalarna 2006 PEACE CNT EFRAIN RRR RR TIO RIOR RIO RI CAR EI IK KRKKKKKKKK RARA RAM s PETC LCN EERE A E RRR III EIA ee IR IER RR EII ER KKKKKKKKKK KK KKK KW S recibe Main Method void main void presenta 29 Main Method This method is included as an essential part of every C and C code It does not receive any variables and it also does not return anything as it is declared as a void It contains only one code line that calls the presenta method Presenta Method This method takes care of displaying some basic information about the program in the form of a banner It does not receive or send
16. 3 AT89C51ED2 DEBUGGING ue a 41 3A FINAL ASSEMBLY aii A A Ad 42 4 POSSIBLE APPLICATIONS AND CHALLENGES o coconoccconocconoccconocccnnoccono 43 5 CONCLUSIONS eege Eder 44 6 REFERENCES 0 45 1 Introduction Project s Proposal In present times the use of remote controlled devices or data transfer has become more interesting and important both for the commercial and research interests Different ways of achieving this goal have been developed through the years Some of them include Microwaves Fiber Optics Radiofrequency and Infrared light The current thesis work proposes a valid way to send characters to a remote placed alphanumeric Liquid Crystal Display The tools used to achieve this project are a Microsoft Windows based Personal Computer with a parallel port This computer will be running a C based program that will take charge of receiving characters from the user On the parallel port of the computer a circuit will be connected This circuit will take care of coding the signal and to send it via infrared LED On the other side a receiving circuit will be placed next to an Atmel AT89C51 microcontroller which will take care of driving the attached alphanumeric liquid crystal display The used LCD will be controlled with the help of the HD44780 driver already mounted on the module 1 1 Background On this section a description of the different components used will be presented Later on the role in the whole project will be explai
17. A RARA RARA RARA RARA RAS void delay void int for i 0 i lt 10000 1 for j 1000 j gt 0 j for i 0 i1 lt 10000 i for 3 1000 3 gt 0 3 BRR KR KK KR KR I I I I RK KK K Method recibe that sets the correct port address according to the user input received the character s to be sent and determines the flow control of the program until it is finished FER I I I IR KK KK void recibe void char dato A op bas int puerto while op 1 amp amp op 2 amp amp op 3 Validates the LPT port printf n nPlease define define which parallel port be used 1 2 3 gt scanf Sc c amp op amp bas if op 1 puerto LPT1 printf AninPort LPT1 0x378 selected n n else puerto LPT2 printf n nPort LPT2 0x278 selected n n else 28 puerto LPT3 printf n nPort LPT3 0x3BC selected n n else printf nINVALID SELECTION PLESE TRY AGAIN while dato 10 printf nNext character to send Carriage Return char to terminate gt scanf Sc c amp dato amp bas Character is received if dato 10 Check if Carriage Return was not received manda puerto dato Send character to the port delay manda puerto 0 printf AnCharacter c sent succesfully n dato else If Carriage Return was received the program is finished printf n nThanks for
18. Alphanumeric LCD infrared control via computer s parallel port H ctor Jaramillo Cantu Master thesis Display Technology 2006 Nr E3460MT DALARNA universty college LCD Engineering Programme Reg number Extent Master in Display Technology E3460MT 15 ECTS Name of student Year Month Day H ctor Jaramillo Cant 2006 06 10 Supervisor Examiner Company Department Supervisor at the Company Department H gskolan Dalarna Jonas Birgerson Alphanumeric LCD infrared control via computer s parallel port Keywords Parallel port Infrared microcontrolle1 wireless remote control LCD telecommunications Summary The present work will explain a method to achieve a remote controlled via IR LED alphanumeric Liquid Crystal Display In modern times the remote access of different devices has become quite popular therefore the aim of this project is to provide a useful tool that will integrate common and easy to access devices The system includes a C language based user interface an assembly language code for the AT89C5IED2 microcontroller instructions and some digital electronic circuits needed for the driving and control of both the LCD and the infrared communication as well as the PC with a parallel port The interaction of all the devices provides a whole system that can be helpful in different applications or it can be separated into each one of its different stages to take the best advantage as possible H gskolan
19. Dalarna Visiting address R da v gen 3 Borl nge Telephone 023 77 80 00 Postal address 781 88 Borl nge Fax 023 77 80 50 I INDEX 1 INDEX iaa idas 3 1 INTRODUCTION co ccncesvscsnesenndstcveescecucsssudetesnvescesetovcetecevcudeseoey dotesescsoosssedseivsedsuces 4 PROJECT S PROPOSAL suscitada iii Eden 4 1 1 BACKGROUND enee ege A ens oe mee ne 4 1 1 1 C programming language ii AA Rice eee 4 1 1 2 Eeer 5 1 1 3 Light Emitting Diodes ici a a 6 1 1 4 Atmel ATSICIIED2 ads 9 1 1 5 EDE Parallel Serial Transceiver IC ooon 11 1 1 6 Hitachi LMOI6L Alphanumeric LCD mode 11 1 1 7 HD44780U LCD Conroaller friver 12 1 1 8 HD44100R LCD Driver with 40 channel ouimuts 14 1 2 PROJECT S BLOCK DIAGRAM id E Ee 15 2 PROJECT DEVELOPMENT ssssciveassscvcessvnsescacese sess tesnsuosisouwcesbesdevaasebevccptevsseeese 17 2 1 COMPONENT DESCRIPTION 83 ste uns aide ins teas oh heuer BEE 17 DVD EE 17 2 1 2 EDE 300 and Infrared Light Emitting Didde 18 2 13 POWELL AA EN AS A 19 DAR reception neers A iia 20 2 1 5 EDE 300 interaction with Atmel ATSOCH TED 21 216 AUNCEATSIC SAPD 210 E AA AAA 21 22 SCHEMATICS in 23 2 2 1 Infrared sending EEN 23 2 2 2 Infrared EE 24 2 3 SOURCE CODE a ii at 27 2 3 1 User EE 27 DD DINE ODD IID COU sas inhaa dis 32 2 4 USER MANUAL FOR THE SOFTWARE cscsccserscesesscdecssnedennsessnaccestensacsnszeanens 36 DASS PECIAL Eerst d e 39 DRE DR EN KE 41 3 1 USER INTERFACE PROGRAM cisuicico ninia tri ENEE 41 Se 41 3
20. Princeton University Press USA 2002 ISBN 0 691 08672 9 EDE 300 Parallel Serial Transceiver IC datasheet E LAB Digital Engineering Inc USA 1996 FLOYD Thomas L Electronic Devices Merril Publishing Company USA 1988 ISBN 0 675 20883 1 FRANZON Tomas UserPort Documentation 2001 Email tomas franzon O hotmail com HF44780U Dot Matrix Liquid Crystal Display Controller Driver datasheet Hitachi Ltd Japan 1998 PEACOCK Craig Interfacing the Standard Parallel Port Beyond Logic webpage June 15 2005 URL http www beyondlogic org spp parallel htm TYSON Jeff How Parallel Ports Work How Stuff Works 1998 2006 URL http computer howstuffworks com parallel port htm 45
21. T ETB RS OV DATO A EN R EN CALL WAIT_LCD Main This is where program starts The tag takes care of calling the sub methods of INIT_LCD and CLEAR_LCD and then transfers the control of the program to the STDBY tag Stdby The instructions that follow this tag are performed in a cycle since the main task of the program after the LCD has been initialized is to wait for a character to be received and then to send it to the module The first instruction MOV A READ reads the data from the READ port to the Accumulator Then this data is compared with zero so in case a zero was received JZ STDBY the port will be checked again in a cycle This cycle is broken when a value different from zero is received so the program calls the WRITE_TEXT routine explained later Then the value of zero is placed again on the Accumulator MOV A 0h and the cycle to wait for a character starts again JMP STDB Y Wait_lcd This subroutine is important because as it is explained in the HD44780U datasheet when the LCD module is done with an instruction a signal will be sent on the DB7 pin The current subset of instructions takes care of check for that 34 signal so the next LCD instruction can be performed It is important to mention also that a timeout of 255 tries is added in case the signal never comes as a way of preventing a potential infinite loop that would cause the malfunction of the program T
22. any parameters since its main task is to display only The final line calls the recibe method Recibe Method This is a very important method for the correct function of the whole program since it takes care of asking and setting for the proper port address that will be used as well as receiving and validating the characters from the user that will be sent It does not receive any parameters and it does not return anything either It uses 4 local variables The first 3 dato op amp bas are characters and the last one puerto is an integer value Here is a short description of each one of the variables and what are they used for e dato It is initialized with the character A so the character receiving cycle can start This variable stores the character typed by the user e op This variable stores the value of the parallel port that will be used through the whole program e bas This is a garbage collector character used to store the carriage return key that is pressed after an option from the program has been selected e puerto This variable stores the value of the selected port and once it is set is not changed until the program is terminated The start of the program is by validating that either choices 1 2 or 3 are selected each one corresponding to the address of a parallel port If something invalid is typed like a character or a higher number the program will send a 30 notification message and then pro
23. ata manipulation will be provided as well as a user manual for the program 2 3 1 User interface code The programming language for the user interface was C as it was mentioned previously The application is a windows console and it was compiled under Microsoft Visual C Figure 2 6 describes the algorithm that was followed No Yes Receive character d from user NI No Was CR received Fig 2 6 User interface program algorithm The code is shown next and an explanation of the different methods will be provided afterwards 27 RRR KR KK KK KK I I IK KK OK The present program is used to capture characters from the keyboard and send them to the parallel port of a computer It should be compiled with Microsoft Visual C For windows NT 2000 XP UserPort should be running along KAAKAA AKAK AKK KKA KK KA K KA K K A K K K K K k k k k kkk S include lt conio h gt include lt stdio h gt define LPT1 0x378 888 define LPT2 0x278 632 define LPT3 0x3BC 956 RRR KR KK KK kkk kkk KKK KKK KKK KKK KKK KK KKK KKK KK K Kk I KK K Method manda to send the character to the parallel port receives both the port number and the character to be sent as parameters KAAKAA I I kkk I OR KK S void manda int port char dat _outp port dat RRR KK KK KK RARA RARA RARA RARA RARA RARA RARA RARA RARA RARA RARA RARA RARA Method to create a time delay KARA RARA RARA RARA RARA RARA RARA RARA RARA RARA RAR
24. e microntroller with a timeout of 256 times If a reset signal is applied to the microcontroller then the LCD will be cleared because it is configured to work like that from the initialization routine 2 2 Schematics The present subsection will describe mainly with images how the physical and electrical connections were made on the whole project 2 2 1 Infrared sending circuit The part of the project that takes care of the parallel port reception and infrared encoding is shown on figure 2 4 It can be seen how everything starts from the DB 25 connector which corresponds to the PC port The data pins 2 9 are connected to the inputs of the EDE300 DO D7 As it was explained earlier this EDE300 is configured as a parallel to serial transceiver therefore the Dir Latch pin 1 is connected to a low voltage input 23 VEE Tomke a a E a R ee REE e TEEN DSUB25F Fig 2 4 Infrared encoding circuit The crystal is also placed in the appropriate pins of the integrated circuit so it works correctly It is important to see how all the stages are placed together including the power stage where the infrared transmission LED is driven by the transistor s collector current in order to enhance the range of the device 2 2 2 Infrared receiving circuit This part of the system is more complex than the previous one due to the inclusion of both the AT89C51ED2 and the LCD module since they both require a higher level
25. eatures are e 5x 8 and 5x10 dot matrix possible e Low power operation support 2 7 to 5 5V e Wide range of liquid crystal display driver power 3 0 to 11V e Liquid crystal drive waveform A One line frequency AC waveform e Correspond to high speed MPU bus interface 2 MHz when VCC 5V e 4 bit or 8 bit MPU interface enabled e 80x 8 bit display RAM 80 characters max e 9 920 bit character generator ROM for a total of 240 character fonts 208 character fonts 5x8 dot 12 32 character fonts 5x10 dot e 64x 8 bit character generator RAM 8 character fonts 5 8 dot 4 character fonts 5 10 dot e 16 common x 40 segment liquid crystal display driver e Programmable duty cycles 1 8 for one line of 5x8 dots with cursor 1 11 for one line of 5x10 dots with cursor 1 16 for two lines of 5x8 dots with cursor e Wide range of instruction functions Display clear cursor home display on off cursor on off display character blink cursor shift display shift e Pin function compatibility with HD44780S e Automatic reset circuit that initializes the controller driver after power on e Internal oscillator with external resistors e Low power consumption The block diagram for the HD44780U is shown in figure 1 8 below Timing generator OSC1 OSCH circuit instruction 7 S register IR a e Ana Display COM to MPU presi ay data RAM 16 bit Common COM1 rach DDRAM shift
26. ecoded by a microprocessor The output of this sensor is connected to the other EDE 300 As it was explained previously this second integrated circuit is configured to have the serial pin as input and the parallel data pins as output to the microcontroller In the next sub section a more detailed explanation of how the microcontroller is connected and configured will be provided and later on the source codes will also be provided 2 1 5 EDE 300 interaction with Atmel AT89C51ED2 The communication between the microcontroller and the serial to parallel configured EDE 300 is very important because it determines the last stage before the LCD starts to display the characters that were originally typed by the user As it was explained earlier the serial data is detected by the IR receiving device then sent to the properly connected EDE 300 The output of this circuit is the parallel word which contains the code of the character according to the HD44780U table which also has some correspondence with the ASCII table The AT89C51ED2 reads the character from the port and then sends it through the output pins into the LCD so it can be displayed In the following sub section a more detailed explanation of how the microcontroller behaves will be provided 2 1 6 Atmel AT89C51ED2 logic The tasks of this microcontroller in the reception circuit are quite crucial since it takes care of sending the proper signals and characters to the HD44780U circuit
27. h one of its different modules The main purpose of doing it by layers was to be able to isolate each one of them in case any problems or wrong design should be found and be able to correct without affecting the project as a whole unit As each one of the parts were tested the results were achieved by stages A whole idea of the system was sketched in the beginning but as the design was started to be made the chunks were modified in order to proper function The project was divided in different blocks as this project report is so the particular analysis of the modules could be analyzed individually 3 1 User interface program First the user interface C program was created Different tests were done and at the end the best was to use the Microsoft Visual C compiler because of its friendly interface and easy way to handle Also the way to handle port access was easy and the debugging interface was useful to identify the former errors and warnings incode A debug was ran many times to ensure the programs robustness before it was tested with the wiring cables First just a series of LEDs were used to ensure that the correct data was sent through the proper parallel port being this part successful 3 2 Power stage The second part consisted on testing the power stage In the electronics lab the proper current was applied to the transistor and to the IR LED ensuring that the proper and needed current was flowing This was correctly done and
28. he first instruction MOV RO 0FFh sets the timeout of 255 using Register 0 as the counter for the number of tries Then a tag of WAIT_1 is placed as a sub loop that will take place for the countdown The next 3 instructions CLR EN CLR RS and SETB RW send the appropriate signals to the LCD to let it know that the instruction has been performed After this is done the whole data bus is set to high voltage in all pins for electronic reasons since when a zero is received the signal on that pin will go to a low voltage Then the port is read again MOV A DATO and the data pin 7 is checked JNB ACC 7 SALIR If the pin is still in high voltage then the value of Register 0 is decremented and the cycle is done again DINZ RO WAIT_1 After the previous cycle is done 255 times or the low signal is received on pin 7 whatever happens first the pins for EN and RW are cleared again and the subroutine returns the control to the previous set of instructions that called it Init_Icd This is where program starts The tag takes care of calling the sub methods of INIT_LCD and CLEAR_LCD and then transfers the control of the program to the STDBY tag Clear_Icd This method follows the instructions provided in the HD44780U manual to clear the data on the display First the instruction of 01H is sent through the data bus Then the EN enable pin is manipulated turned on and off so the instruction is executed After the WAIT _LCD routine is called t
29. how the pinout description of EPP and ECP respectively Pin EPP Signal Pin EPP Signal Pin EPP Signal 1 Write 10 Interrupt 19 Ground 2 Data 0 11 Wait 20 Ground 3 Data 1 12 Spare 21 Ground 4 Data 2 13 Spare 22 Ground 5 Data 3 14 Data Strobe 23 Ground 6 Data 4 15 Spare 24 Ground 7 Data 5 16 Reset 25 Ground 8 Data 6 17 Address Strobe 9 Data 7 18 Ground Table 1 1 EPP pinout description Pin ECP Signal Pin ECP Signal Pin ECP Signal 1 HostCLK 10 PeriphCLK 19 Ground 2 Data 0 11 PeriphACK 20 Ground 3 Data 1 12 nACK reverse 21 Ground 4 Data 2 13 X Flag 22 Ground 5 Data 3 14 Host ACK 23 Ground 6 Data 4 15 PeriphRequest 24 Ground 7 Data 5 16 nReverseRequest 25 Ground 8 Data 6 17 1284 Active 9 Data 7 18 Ground Table 1 2 ECP pinout description One important characteristic of the parallel port is that it uses the connector called DB 25 This connector illustrated in figure 1 1 consists of 25 pins shaped in a D form The computers generally include a female connector 13 1 25 14 25 pin D SUB female at the PC Fig 1 1 DB 25 connector Courtesy of HowStuffWorks Inc 1 1 3 Light Emitting Diodes To describe the Light Emitting Diode LED first some background of the diode working principles must be provided The diode is a semiconductor device it is able to transport electric current typically made of alum
30. inum gallium arsenide AlGaAs To make the device working the pure material should be doped a method which consists of adding impurities so the material can be better in conducting the current This state is achieved by either adding holes or extra electrons to the material When the material has extra electrons it is said that has a negative charge therefore it is called N type On the other hand when the material has extra holes the charge is positive therefore it is called P type material The diode task is then to compromise two sections of N type and P type material bonded together with electrodes on each end This causes the current to flow in only one direction When no voltage is applied to the diode no current flows and therefore the holes of the P type material are filled with the extra electrons of the N type material The way to connect the diode to work properly is illustrated in figure 1 2 where it can be seen that the negative part of the power supply is connected to the N type material and the same is done with the positive part of the power supply and the P type zone gt Current flows across this junction lo mal Fig 1 2 Correct connection of a diode Courtesy of HowStuffWorks Inc The light on a diode is produced when its atoms release photons as a source of energy The photons are released because of the change of conduction band from the electrons As it was explained before the
31. ject consists of two main blocks The first one covers the part that captures and sends the infrared data and the second one includes the receiving circuit and the LCD module Figures 1 10 and 1 11 refer to the block diagram of each one of the blocks PC running C based Electronic circut Power stage attached console program to attached to parallel to IR LED m charge capture user s typed port converting of sending the data characters parallel data mto serial Fig 1 10 Block diagram of IR sending 15 IR signal Electronic circutt detector that that transforms converts pulses serial signal into into electric parallel data current Microcontroller in charge of sending characters and drving LCD LCD module displaying characters typed n PC Fig 1 11 Block Diagram for IR receive stage Both blocks complement each other In the upcoming section an explanation of how each one of the blocks interact with each other as well as a description of which devices belong to each one will be provided 16 2 Project Development In this part a more extensive description of the followed procedure and applied components will be provided First a description of how the components were used as well as their role in the whole project will be made then the schematics and source codes will be provided with the necessary explanation 2 1 Component description 2 1 1 Parallel port For the scope of thi
32. l reach the other side Also demanding too much current can cause malfunction that is a strong reason to add this power stage This is a very basic power stage provided by one NPN bipolar general purpose transistor BC549 Figure 2 1 shows the simulation of the power stage assuming that 25mA the maximum rate is provided by the EDE300 The resistors were calculated so the transistor current does not exceed the 100mA Also in the simulation two amperimeters are placed to measure the electric current flowing from the interesting points 19 N Multimeter XMM3 x ee E E aE Multimeter XMM1 CH i g m A a e a Cf i H set Fig 2 1 Circuit simulation of the power stage 2 1 4 IR reception On the other circuit the first component needed is the infrared receptor The device used for this purpose is the Everlight Miniature Type IRM 8601S shown in figure 2 2 It consists of a photodiode with an integrated circuit encapsulated in a metal case which makes it resistant to different noises and ambient light Fig 2 2 Picture of IRM 8601S 20 It is important to mention that it consumes low power making it reliable for different applications Also it has CMOS and TTL levels compatibility which makes it very suitable for the current project The pin diode and preamplifier are assembled on a lead frame the epoxy package is designed as an IR filter The demodulated output signal can directly be d
33. mpt again for a valid option until this has been received When this happens a confirmation banner will be shown on the screen The next part of the program consists of prompting the user for a character to be sent to the port This prompt will go on until a carriage return ASCII code A in hex is received which will terminate the program When a character is received the program calls the manda method which takes care of sending the characters to the port providing the parameters of the character and the port number stored in the dato and puerto variables respectively After this is done the delay method is called and then the manda method is called again this time sending a value of 0 zero instead of the dato variable This is performed because according to program logic after a character is sent a signal of zero is sent to let the microcontroller on the other side know that no new character has been typed Finally a banner that informs the success in sending the character is displayed on screen and the cycle for character receiving starts again When the carriage return character is received a banner indicates that the program is finished and the getch instruction is performed so the user can type any key to close the window Delay Method The task of this method is to create a time delay for the data to be sent to the parallel port the to the circuit It is used between the sending of a character and the sendi
34. nction set Interface is bits long BF can be checked after the following instructions When BF is not checked the waiting tme between nstructions is longer than the execution instuction time See Table 6 Function set Interface is 8 bits long Specify the RS R WDB7 D80 DB5 D84 DB3 D82 DB1 D80 number of display lines and character font 0 N Ers The number of display lines and character font lon 0 8 0 bot oo yl cannot be changed after this point 0 0 0 0 1 0 0 Display off VD Display clear Entry mode set Intialization ends Fig 2 3 LCD Routine steps As it will be explained later on the source codes section the AT89C51ED2 is constantly checking the input port connected to the EDE300 This is PORT 0 consisting on the 8 bits from pin 0 0 to pin 0 7 According to the logic of the program while no character is being sent a value of zero all the pins will be in low voltage will be read causing the microcontroller to keep scanning that port 22 until a different value is received This different should be the character code and therefore it will send the appropriate signals for the character to be displayed The sequence is first to send a high voltage to RS signal then move the read byte code to the output port Port 1 and then set the EN signal so the display executes the write data command After as it is explained in the HD44780U datasheet the LCD sends a busy signal on pin DB7 which is checked by th
35. ned in detail 1 1 1 C programming language C is a widely used programming language that sometimes is referred as a high level assembly or portable assembly It can be compiled in a straightforward way using a single pass compiler C compilers can be developed in a relatively easy way due to the fact of the small feature set and low level abstraction Thanks to this fact it offers quite good portability this meaning that the codes can be compiled in different operating systems and computer architectures without having to do major changes in it It was started to be developed in the early 1970 s in AT amp T Bell Labs As it became more and more popular it started to replace the BASIC language as the popular language to program microcomputers In 1983 the the American National Standards Institute ANSI formed a committee X3J11 to establish a standard specification of C After a long and arduous process the standard was completed in 1989 and ratified as ANSI X3 159 1989 Programming Language C This version of the language is often referred to as ANSI C Some minor modifications were made by the International Organization for Standardization ISO and by the year of 1990 it was also adopted It is quite common to find C compilers for different processors and operating systems and also most of them are well optimized object or machine code 1 1 2 Parallel port The parallel port also known as printer port has been a very
36. ng of a zero through the parallel port so the EDE300 circuit has enough time to do its transceiver job This consists of two sets of nested for instructions It does not receive or return any parameters Manda Method D This method consists of one instruction only which is _outp This instruction is very important because it performs the data transfer to the parallel port This instruction receives as parameters the address of the port as well as the data that is going to be sent The method does not return any value but it receives the parameters of the port and the data as the integer variable port and the character variable dat respectively 31 2 3 2 AT89C51ED2 code The language used to program the microcontroller was assembly language according to the instruction set provided by the manufacturer According to the logic of the assembly language it does not contain different methods but tags that lead to instructions The algorithm used for the program is shown in figure 2 7 Initialize LCD module Yes Was zero received No Write character to LCD Fig 2 7 AT89C51ED2 program algorithm It was mentioned earlier that Port 1 is used as the data communications port to the LCD therefore the mnemonic of DBO DB7 was assigned to each one of the pins as well as the whole port is called DATO to be managed through the whole program The signals of RW RS and EN were assigned to pin 3 5 pin 3 6 and pin 3 7
37. o wait for the LCD to finish processing the instruction 35 Write_text In this routine the instructions to write the data to the LCD are followed as the datasheet for HD44780U indicate First the RS Register Select is set on then the received data from the EDE 300 is sent to the data bus After the EN enable pin is manipulated turned on and off and the wait routine is called before it returns the control to the method that called originally 2 4 User Manual for the software The way to start the program is by running the Char Rcv exe executable file provided with the system The first screen will display a banner shown on figure 2 8 that introduces the user to the program On this initial screen the user is prompted to choose the LPT Parallel port that will be used to transfer the data ex C Documents and Settings d Mis documentos LCD Thesis Debug Char Rcv exe ROO har Ko exe Welcome to the program that will send data to LCD The way this program works is by prompting the user to type in the desired character then it will be sent to the LCD connected in the remote location The program will terminate when Carriage Return is sent as character Programmed by Hector Jaramillo Cantu Hogskolan Dalarna 2666 EEE EEE EEE EEE EE PEE NEE EEN EE EEN ENEE EEN Please define define which parallel port be used 1 2 3 gt gt m Fig 2 8 Char Rcv initial screen Notice that the program can only accept options 1 2 or
38. r dynamic liquid crystal and can be applied as a common or segment driver The device features are e Liquid crystal display driver with serial parallel conversion function e Serial transfer facilitates board design e Capable of interfacing to liquid crystal display controllers HD43160AH LCTC HD61830 61830B LCD II HD44780S HD44780U LCD IIA HD66780 LCD E HD66702 LCD HD44790 HD66710 e 40 internal liquid crystal display drivers e Internal serial parallel conversion circuits 20 bit shift register x2 20 bit data latch x2 e Display bias Static to 1 5 e Power supply Internal logic Vec 2 7 to 5 5V Liquid crystal display driver circuit Vec Veg 3 to 13V e Separation of internal logic from liquid crystal display driver circuit increases applicable controllers and liquid crystal types e CMOS process Figure 1 9 shows the block diagram for the device 14 Y Y20 LCD Drivers Latch signal fi 20 bit latch v1 V2 V3 V4 CL Shift direction CL2 it signa 20 bit bidirectional shift register FCS Shift direction M v1 V2 v5 V6 Ya1 Yao Fig 1 9 Block Diagram for HD44100R Courtesy of Hitachi As it can be seen from the previous description this driver works in good company with the HD44780U by providing the proper signals needed to drive the liquid crystal segments The group of segments is what creates one complete character 1 2 Project s block diagram The pro
39. r to get an appropriate timing to synchronize the whole unit 42 4 Possible applications and challenges The current project can have different applications that can go from toys to computer peripherals to even devices that can help disabled people depending on the point of view It covers different topics from C programming to different fields of electronics as well as the Liquid Crystal Display driving The whole project is an approach for what could be made into a more robust system It provides the basis for wireless communication that can be used in a single room One first challenge can be to use different ports from the computer and be able to connect to serial or even USB depending on which kind of computer is used Another challenge can be to extend the operative system menu not only to Windows but maybe to be able to use the whole system in a Macintosh or UNIX Linux system This would require a complete remake of the user application software Maybe even another language rather than C C can be used but the same logic should be followed in order to keep the rest of the project working Something that can also be taken care of is the enhance of the power stage of the infrared led to enlarge the distance range that the controller can operate Something that can also be done would be to change the transmission medium and instead of using an IR LED use something else like Radio Frequency microwaves or some kind of telecommunication
40. respectively Finally the mnemonic of READ was given to Port 0 which takes care of receiving the parallel data from the EDE300 before it is sent to the LCD module The whole program code is shown below and after an explanation of the instructions sorted by tag is provided 32 Program for the Atmel Al drive LCD to LCD Coded by H ctor Jaramil lo Cant for the Master Display Technology H gskolan Dalarna DBO EQU P1 DB1 EQ DB2 EQ DB3 EQ DB4 DB5 DB6 DB7 YWYHNDUBWNHER OH www dd UU Ut KE ARI EQU PO 10 E HU D H DOP org 0 MAIN CALL INIT_LCD CALL CLEAR_LCD JMP STDBY STDBY MOV A REA JZ STDBY CALL WRITE MOV A 0h JMP STDBY EXT WAIT_LCD MOV RO 0FFh WATT gd LA EN RS RW DATO 0FFh EN DATO CC 7 SALIR RO WAIT_1 P EN RW INIT_LCD R RS OV DATO 38h TB EN EN RS DATO 0Eh EN EN RS DATO 06h EN N L T VAIT_LCD TB VAIT_LCD T TB Kal POVZORONZOrRONZO GE D W C aay VAIT_LCD Borl nge Sweden 2006 33 T89C51ED2 used to initial receive a parallel byte and send as a character lize and Thesis in CLEAR_LCD CLR RS MOV DATO 01h SETB EN CLR EN R R CALL WAIT_LCD SN WRITE_TEX
41. rial communications The microcontroller design can bring down the clock frequency to any value which is a good characteristic so power consumption can be reduced without any data loss All these features make the device powerful for applications with the 9 need of pulse width modulation high frequency input output and counting capabilities like corded phones smart card readers alarms etc Figures 1 5 and 1 6 show respectively the block diagram for the AT89C51ED2 and the 40 pin encapsulation used for the current project E a 3 Go On e lt x lt gt w ER S LE Se Y Flash EEPROM XTALA1 64K x8 XTALA2 c5 col ALE PRO PSEN EA Parallel UO Ports amp BOOT Regulator RD 2 fa E External Bus oct Si g pe J PFD 3 imer gt ROM ar jie 21 a 2 W Loge 117 wo RESET TO T1 INTO INTA PO P1 P2 P3 P4 MISO 1 Alternate function of Port 1 2 Alternate function of Port 3 Fig 1 5 AT89C51 Block Diagram Courtesy of ATMEL P1 0 T2 40 vcc P1 1 T2EX SS 39 PO 0 ADO P1 2 ECI 381 P0 1 AD1 P1 3CEX0 377 PO 2 AD2 P1 4 CEX1 36 P0 3 AD3 35 P0 4 4D4 y PO S ADS 33 P0 6 AD6 P1 5 CEX2 MISO P1 6 CEX3 SCK P1 7CEX4 MOSI RST H PO 7 AD7 P3 0 RxD 10 31 EA P3 1 TxD AT89C51ED2 gt H ALE PROG P3 2 INTO PDIL40 gt H PSEN P3 3 INTT P2 7 AD15 P3 4 T0 ee P35 T1 2 5 4D13 P3 6 WR 25 i P2 4 AD12 e P2 3 AD11 P3 7 RD XTAL2 237 P2 2 AD10 XTAL1 22
42. rward current The amount of light output is directly proportional to the forward current as figure 1 4 can illustrate Infrared LEDs can be used in optical coupling applications often in cooperation with fiber optics as well as remote control applications for short distances Light output vs Forward Current 120 100 E 80 o 3 60 ke 2 amp 40 ge 20 0 0 2 4 6 8 10 If mA Fig 1 4 Output light vs Forward current The way to apply IR LED technology to telecommunications can be in short range and computer peripherals as well as hand held devices Commonly the Infrared Data Association IrDA publishes different standards related to this matter The way to apply an IR LED is by emitting radiation into a narrow beam that is then modulated to encode the data and then received on a silicon photodiode that transforms the received data into electric current 1 1 4 Atmel AT89C51ED2 According to the datasheet provided by the manufacturer the AT89C51ED2 has 64 Kbyte Flash memory that can be used both for code and data This memory can be programmed in either serial or parallel mode depending on the software used It also has 256 bytes of internal RAM a 9 source 4 level interrupt controller and three timers The total amount of nonvolatile memory EEPROM consists of 2048 bytes Also it has a programmable counter array a XRAM or 1792 bytes a Hardware Watchdog timer and some other features regarding the se
43. s device such as TCP IP UDP or IPX The add of any of these options would drastically change the original design and logic of the programs 43 5 Conclusions Many challenges were encountered during the develop of the current project First the original design had to be modified several times in order to correct possible non working situations and to correct the needed details in order to make the system to work as planned and expected This project itself covers different areas focusing more on the electronics driving of an LCD module and its interaction with different devices In the present times there are a few devices that work as standalone This means that most of the time the systems integrate different technologies to be able to perform a certain specific task This project is a clear example of how the devices need to interact together As it was mentioned earlier this work just presents one possible way of making this wireless communication possible This means that different approaches can be proposed as well as developing extra features for the system 44 6 References 1 2 3 4 5 6 7 8 A brief history of parallel ports Thaddeus Computing Inc 2005 URL http www palmtoppaper com ptphtml 45 45c0000d htm C Programming Language Wikipedia the free encyclopedia 14 May 2006 URL http en wikipedia org wiki C_ programming language COLLINS Peter J Liquid Crystals
44. s project there is no real difference in using an EPP or ECP parallel port since the main task that it accomplish is to send the data to the electronic circuit that later codes into the infrared signal The connector used is then a DB 25 male with 8 wires that go from pins 2 9 which correspond to the Data signals 0 7 often called Data Register and one wire used for common node GND which goes from pins 18 to 25 The corresponding base addresses for the Parallel port can be 0x278 0x378 and 0x3BC which are also the same addresses needed to access the data register and send the required information If the user does not know to which one corresponds the one in the PC it can be checked by going to the Hardware Profiles option on the Windows Control Panel where the proper address value will be displayed The software coded for the present project gives an option for manually selecting the proper port which will be explained later Table 2 1 illustrates which pins of the port and where they connect to in the electronic circuit were used Note that only one of the ground signals is used but all of them are displayed for better comprehension of the model I 5 Parallel port signal NC Data 0 Data 1 Data 2 Data 3 Data 4 Data 5 Data 6 Data 7 NC NC OO jo IN ID jo JO JP J ak ch O 17 12 NC 13 NC 14 NC 15 NC 16 NC 17 NC
45. sent to the LCD connected in the remote location The program will terminate when Carriage Return is sent as character Programmed by Hector Jaramillo Cantu Hogskolan Dalarna 20666 EEEE EEEE EEEE EEEE E E E 999000000 SHOOT Please define define which parallel port be used 1 2 3 gt gt w INVALID SELECTION PLESE TRY AGAIN Please define define which parallel port be used 1 2 3 gt gt 1 Port LPT1 x378 selected Next character to send Carriage Return char to terminate gt gt Fig 2 10 Selection of parallel port After the proper port has been selected the program will prompt for the character to be sent to the port The user then should type one character and then carriage return The program will send a confirmation of the sent data and prompt again for another character as it can be seen on figure 2 11 37 BEE KEE RCE U ET Welcome to the program that will send data to LCD The way this program works is by prompting the user to type in the desired character then it will be sent to the LCD connected in the remote location The program will terminate when Carriage Return is sent as character Programmed by Hector Jaramillo Cantu Hogskolan Dalarna 2006 Please define define which parallel port be used 1 2 3 gt gt w INVALID SELECTION PLESE TRY AGAIN Please define define which parallel port be used 1 2 3 gt gt 1 Port LPT1 x378 selected Next character to send Carriage Return char to terminate gt
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