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Driving LCD 7-seg passive displays with PIC

Discussion in 'Electronic Basics' started by [email protected], Sep 17, 2008.

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  1. Guest

    I have a passive LCD with 8 7-seg digits plus point and some other
    symbol. It has 23 connections.
    I wish to drive it with a PIC that has LCD module built-in but I have
    seen that all PICs capable to drive LCD have only 4 commons. I
    supposed that was needed 1 common for each digit but probably I have
    to use bias plus multiplex. In this case how can I do? I have not
    found any application notes and info on internet. Thanks.
     
  2. You can use a port expander. Microchip has at least one of these, and
    there are app notes on how to use them. You can also use serial in -
    parallel out shift registers to drive these things. That is probably
    easier to control. Using these, you can drive all the bits with 3 GPIO
    pins. You will need 3 of them.

    http://www.allaboutcircuits.com/vol_4/chpt_12/4.html

    Regards,
    Bob Monsen
     
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