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MOVING MESSAGE DISPLAY HELP

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by brasky, Jul 1, 2008.

  1. brasky

    brasky New Member

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    Hi Binu. I must thank you immensely for restimulating my interest in Microcontroller programming. I'm a regular to ur site. it is simply the best
    in microcontroller designs. I have been trying to design a MOVING MESSAGE DISPLAY interfaced to pc keyboard but am confused.
    PLEASE, I will be very greatful if U can help me.It will be a dream fulfillment. You can reply me with this email address: brasky_info@yahoo.com
  2. Binu

    Binu Administrator

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    Search the forum for Moving message display and there is another thread running with this topic.

    For PC keyboard interface please visit the CODE LIBRARY page.
  3. brasky

    brasky New Member

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    Thanks Binu. I was able to get something on moving message display
    though it was very difficult for me. I got the schematics and will try it out. But i have problem with how to write a software that will store the data(5bytes) per character into EEPROM and then display.
  4. Binu

    Binu Administrator

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    if you are a beginner try some other project else try a simple 8x8 matrix display system and go it step by step and this project will not be suitable for beginners.:(
  5. brasky

    brasky New Member

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    Sir, i think you misunderstood me. I'm not a beginner in Microcontroller just that i had been away for sometime. I have built a 7x20 dot matrix screen(ie 4 7x5screens) and it is working fine. i used PIC16F877A and did another with 89S51.But they displayed fixed message in table.

    Now, my problem is that i want to change the message displayed at will using any input device say keyboard or PC.
    I will be grateful if you can give me idea on how to store the data in EEPROM and change them anytime i want. PLease help
  6. brasky

    brasky New Member

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    since i use a 7x5 screen that is 7rows by 5 columns, i use 5 bytes to represent a character on screen for example the character E is represented in table as 7Fh,49h,49h,41h,41h which is 5bytes for one letter. How do i change the stored data in EEPROM if i am using PCkeyboard while the dot matrix is on. Because i know that pressing any key on the keyboard say the letter E, the equivalent in ASCII will be generated(which is 1byte) and obviously i will need to convert the ASCII code to 5byte as above before storing in EEPROM. The help i need is how do i implement this conversion before storage in software.
    Help me with the Algorithm. PLEASE HELP ME!
  7. Binu

    Binu Administrator

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    You can use a Look-up table to get the equivalent 5bytes for a single byte from Pc/keyboard.

    Do it like this, assume that you have press "A" and the ascii character is 41.

    CJNE A,#41H,NEXT ;check if the value in the Acc is 41h
    CALL GET_BYTES_FOR_A
    RET

    NEXT: CJNE A,#42H,NEXT1 ;check if the value in the Acc is 42h
    CALL GET_BYTES_FOR_B
    RET

    NEXT1:
  8. brasky

    brasky New Member

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    Thanks Binu. I have built the circuit for the moving message using your
    circuit and it worked perfectly. Thank you very much.

    First thing first. The project is working fine now. It is time for me to focus on changing the displayed message at will as i requested for ab initio. I made alot of sense from the last algorithm. But i want to perfect on storing and deleting bytes to and fro I2C. I guess that is where the messages will be stored OR can i change the message code from keyboard using PROGRAM MEMORY?

    2. How can i learn from the scratch details on interfacing I2C.if any link i'll be grateful. still trying to study that in code library.


    PLEASE I REALLY WANT TO KNOW HOW TO CODE AND USE THE I2C. THOUGH I WAS USED TO USING in-built EEPROM IN PICmicro but can get only 256bytes. i require more capacity hence i must use I2C. HELP. THANKS in advance.
  9. Binu

    Binu Administrator

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    [^]congrats for completing the first step, so you can easily jump all other steps.
    Yes interfacing I2C EEPROM you can achieve more characters and even pictures.

    For read and write the I2C memory please check other projects, most of the projects use EEPROM. Just take the code for reading and writing memory.

    Ok, whats the code which you use now to display, post it here so i can give more hints.
  10. brasky

    brasky New Member

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    Thanks for ur assistance. I'm so excited to be guided by a great person of ur kind. I used microchip and i am converting the code for use by 8051 with same principle so that others can benefit cos it's an 8051 forum. I use pic cos in kwara state where i live we rarely access it unlike the microchip devices.

    I have read the I2C code over and over again and it is making sense now. Help and questions will be after i paste the code so that u can go through it and assistant. Thanks again for ur time.
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