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Discussion in 'The Projects Forum' started by micro, May 3, 2006.

  1. micro

    Thread Starter Member

    Feb 10, 2006
    26
    0
    I just brought a HD44780 16x2 hitachi LCD. I have connected it to
    my PIC16f877 but there was only black boxes display on my LCD screen
    and no word on the screen. May I know how to test my LCD to make sure
    it is still function? Thanks. :D
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,163
    1,796
    It sounds like you forgot to provide for a contrast adjustment. This is an analog voltage that is between the supply rails. Try adjusting it if you have one. Go back to the data sheet if you don't.
     
  3. micro

    Thread Starter Member

    Feb 10, 2006
    26
    0

    Thanks, Papabravo. I do have a contrast adjustment between the supply rail on my LCD display. I have adjusted it but only can see the black boxes on my screen, may I know how do solve this problem? Thanks.
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,163
    1,796
    Do you have multiple voltages connected to the display, or only a positive Vdd and Ground? There should be a total of three connections to the contrast adjustment potentiometer, and you need to refer to the datasheet. As you turn the potentiometer the voltage on the contrast adjust pin will be between the voltages on either end of the potentiometer. Use a voltmeter and confirm that you can put the contrast adjust pin between the supply rails. The value of the potentiometer is also important. Again, please check the datasheet.

    When you have the contrast the way you want it you can replace the contrast adjustment with a simple voltage divider made up of fixed resistors.

    Most LCD devices have registers which can be read or written. Do you have a parallel interface or a serial interface?
     
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