Sunday, July 6, 2014

Graphics LCD [GLCD]

I have some 128x64 Graphics LCDs that have been "sitting in inventory" for a long time. Probably got them from (they're AZDisplay AGM1264). They're KS0108-based, nothin but pixel control; there's no character set, the designer has to create all that himself.
A week or so ago I took one out and really started researching. I found a good site ( that was very helpful, especially with his simulator.

I wanted to write my own code (not pinch someone's "library"), that's how I roll. All credit to me (Hurrah!)

  • I found that the Enable (E) pin is actually a data latch.
  • The display comes up with all of the pixels dark (on), so they have to be cleared out.
  • There's a parameter that cannot be overlooked: Display Start Line, it's an Instruction. It doesn't default to zero and can be unpredictable that way. I wasn't doing anything with it and the display would come up with the top line of pixels dark (on). I thought that it was possibly a defective unit, but I remembered seeing an opaque note in the datasheet note about its use for scrolling, so I thought that I'd better get in there and plug something in - and that made my problem go away.
  • Its Vee is NOT an input for an external negative supply, it's the output of an on-board negative supply that gets wired to a contrast pot.  Unlike a lot of character LCDs (44780-based designs), you cannot get by with connecting Vo to Gnd.

So far I'm just using the left half to figure things out, less to manage.

The results (so far):

The same message, twice, but the second has "reverse field" characters.
Well, that's all for now.  I'll post back soon with more info, pics, and so on.

2015FEB20 - Kind of getting back into this.  Here's a pic of the pin out.

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