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Thread: 4bit lcd schematic

  1. #1
    Maximum Bitrate
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    Mar 2001
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    Cincinnati, Ohio
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    Question 4bit lcd schematic

    Ok, I hate to make so many topics in such a short time, but hopefully its helpful stuff for people that will search later.

    I am trying to connect my 4bit lcd to my computer. I'm pretty sure its hdd44780 compatible though.
    for some wierd reason it has 22 pins, the first 4 are all ground and connected together, the 6th through 9th, and the last 4 are all connected together, and are ground.
    I couldn't find the schematic for my lcd, but I got one from an LCD on EIO's website that had the same configuration.
    Do 4 bit lcds boot up the same as 8 bit and make one bar black all the way acrost?
    do 2x16's do that? I've only worked with 4x40s before.

    How do I connect it to the Parrallel port?
    here is the schematic
    There is a DB7 through DB4, So I tried connecting that to DB0 through DB3 on the 8 bit schematic (4 to 0, 5 to 1, 6 to 2, 7 to 3), but it doesn't seem to work.
    Could someone help me out?
    Clarion 200watt head unit w/ Aux in.
    Kicker 800watt 4 channel amp
    In a 96 Grand Prix SE.

  2. #2
    777
    777 is offline
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    Join Date
    Sep 2001
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    I have the same LCD and I hooked it up various ways and all I get is gibberish across both lines. If anyone can help, i'd be greatful.

  3. #3
    Raw Wave Rob Withey's Avatar
    Join Date
    Apr 2000
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    Bedfordshire, UK
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    Post

    I have hooked up my HDD44780 compatible 4x20 VFD with a 4 bit interface. The initialisation codes for 4 bit are significantly different from 8 bit initialisation on the HDD44780. I wrote my own display driver, so completely avoided the problem. I haven't yet uploaded source and schematics for my driver and parallel port hook up, perhaps one day.

    There are plenty of web sites out there that tell you how to program using a 4 bit interface, for example:
    http://www.doc.ic.ac.uk/~ih/doc/lcd/initiali.html

    I'm guessing that most of the LCD plugins out there assume an 8 bit interface.


    Rob
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

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