128x64 Graphic LCD: Cant set vertical address past 32

Discussion in 'General Electronics Chat' started by Robin Mitchell, Dec 24, 2014.

  1. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
    732
    199
    Hi all,

    Yes its christmas eve and I am in the workshop!

    So I have a graphical LCD 128x64 based on the ST7920 driver but I cant get it to write anything to the graphical ram past vertical address 32. This means that only the top half of the display is working. The strange thing is that sometimes the bottom half is identical to the top half. Any ideas?

    All the best,
    Robin
     
  2. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
    732
    199
    Ok I solved my problem but I dont understand why this is happening:

    I can only set the vertical address to a number between 0 and 31. If I want to go to the vertical lines 32 to 63 I need to set the y address back to 0 but set the x address to 8 onward.

    For example:

    To go to x = 0 and y = 0 I would set x = 0 and y = 0
    To go to x = 0 and y = 33 I would set x = 8 and y = 0

    What LCD DO I have? Is this a different driver?
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    I was wondering the same thing. Is there some sort of part number on it you can share?

    Knowing that we could look up the data sheet.
     
  4. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
    732
    199
    Well its from china XD

    The ONLY number is 12864 which obviously means 128x64 pixels
    It works with the ST7920 instructions AND has a PSB pin. The VOUT pin seems to produce nothing and the RST signal resets on a low.
     
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