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Thread: cant get LCD to display anything, please help.

  1. #1
    Join Date
    Mar 2004

    cant get LCD to display anything,-sorted it now.

    hi cant get LCD to display anything, it is 40 x 2 HD44780 ive wired it accordin to the following (to parallel port)

    printer port LCD

    D0 (2) D0 (7)
    D1 (3) D1 (8)
    D2 (4) D2 (9)
    D3 (5) D3 (10)
    D4 (6) D4 (11)
    D5 (7) D5 (12)
    D6 (8) D6 (13)
    D7 (9) D7 (14)
    nSTRB (1) EN (6)
    nLF (14) nRW (5)
    INIT (16) RS (4)
    +10k pot between +5 and Gnd with wiper to pin3 of lcd.

    The pinout (shown above from various websites) matched up with the datasheet so it really seems pretty standard. ive double checked my wiring all seems fine!, the 5v supply is taken from the comp molex connector in the comp (checked 5v). im sure its all grounded right as i can read the voltages on my meter fine and ive checked it all for continuity.

    the software im running is:

    and ive played with:

    but cant get anything to display!!

    after searching i found out about lcdprint.exe but that doesnt display either!

    my port bias settings are set to EPP+ECP

    one assumption i did make when wireing is the numbering of the pins on the lcd as only pins 1 and 14 are numbered. so i assumed they are as follows:

    1 3 5 7 9 11 13
    2 4 6 8 10 12 14

    as i presume its designed to plug into a header! which would be wired in this way and not like the other possible solution!

    1 2 3 4 5 6 7
    8 9 10 11 12 13 14

    is that how they (generally) are wired?

    anything else i may of overlooked?

    (p.s. it hasnt got hot or smoked yet)
    (i went by the number marked on my p.port connector itsself (R.S.) so im pretty sure there right and its not a case of reading it the wrong way round!)

  2. #2
    FLAC DodgeCummins's Avatar
    Join Date
    Oct 2000
    DFW area
    Make sure the correct printer port settings are being used...not just the EPP ECP settings, but the actual I/O settings. and then make sure your testing programs are looking for that port.

    Other than that, if everything is working right, you should at least have a you? When you first turn it on, do you get a blank screen filled with boxes (I guess that wouldn't really be blank then)?

  3. #3
    Join Date
    Mar 2004
    Figured it out! my display is extended temp range so when driving it at 5v the contrast pin needs to go -ve to display anything! alteratively i can (and probably will) drive it at a higher voltage. i find that at 9v the contrast input must be at abou0.6V (where as i needed -2.8V before! -hence why i couldnt display anything!)


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