I'm writing some drivers for my SBC to drive an LCD of 20x4. However, I think the memory format is 40x4.

I can write characters just fine but I'm having trouble finding information on the bizarre memory format of it. From what I understand, it's defined somewhat like:



When I plot characters (and allow the cursor to automatically move), it fills up the "A" lines but the "B" lines never print. Actually, it seems like there is another page to the right just like the first page. Meaning, when I print past "ROW 0, COL 19", instead of going to the second line, there seems to be another 20 characters hidden to the right. It's like I have 80 characters total but only 40 can be seen (just the "A" lines).

I've tried searching for docs but everything I find is suited for Arduino. I suppose I could study the Arduino LCD library but I'd like to find a good list of commands, memory layouts, etc.

The good news is that I can successfully send commands and data. I just don't know what commands to send!

I have found some generic LCD command lists but none (that I've found) indicate the various memory layouts.

Thanks for any suggestions!

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Cat; the other white meat.

For the BBB... lines you must precharge an address of 0x40 + actual position. You need to use the SET DDRAM address command (0x80 + address). You also need to initialize the display to 2 lines (0b001x1000 / x: 8 or 4 bit I/F). The controller sees lines 1 & 3 as line 1 and 2 & 4 as line 2.

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6502 sources on GitHub: https://github.com/Klaus2m5

AH! Thanks Klaus.

I will give that a go later this evening.

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Cat; the other white meat.

FYI,

I am building some libraries to work with the LCD and the 65C02. I hope to get my Potpourri6502 completely documented and open-sourced as I go along. Warts and all.

Just a small way of giving back to the 6502 world.

"MOSTLY/SORTA" working code so far:

https://github.com/cbmeeks/Potpourri650 ... er/lcd.asm

I tried to keep everything within 80 columns. Old habit of mine. Even though I have large monitors. The 80 columns is nice to print out on old vintage printers too.

The main project will be hosted here:

https://github.com/cbmeeks/Potpourri6502

I hope to get the schematics and Gerbers up soon.

As I build a simple monitor, I will post that as well.

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Cat; the other white meat.

Thanks for sharing and open-sourcing your code!

You're welcome. But you may not be thanking me after you read it. LOL

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Cat; the other white meat.

See my LCD code at http://wilsonminesco.com/6502primer/LCDcode.asm . Note the writing of the function set three times in the initialization. We found, in a work project years ago, that this is necessary for a reliable initialization that works every time. We sometimes had problems, until an applications engineer faxed us (this was when the internet was in its infancy) an ap. note with this information. We never had trouble again.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Thanks for that tip!

Yeah, I've read your LCD code and learned a lot from it. I forgot about the three times. Fortunately, mine has been working but I've only used the ONE LCD module. So I could just be lucky.

I will make those changes as it's not a big deal and I like the reliability.

Thanks.

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Cat; the other white meat.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

That's pretty awesome!

I used to have a wide-carriage dot matrix printer that I tossed years ago. Why did I do that??

Fortunately, I just purchased a Panasonic KX-P2123 from a thrift store for $3.99. Looks to be in great shape. I have a couple Apple dot-matrix printers too IIRC.

I plan on hooking that printer up to the Potpourri6502 and do some old-school printing. You can even still buy ribbons for that Panasonic.

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Cat; the other white meat.

There are also re-inkers and re-inking services (which I've seen at local electronics swap meets), but I have not helped myself to them so far. I do have a box of old ribbons I would like to get re-inked. Fry's electronics still sells the ribbons for my old printers which I have several of, in standard width and the wide ones too. I have a box of green-line wide fanfold paper too.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

LCD library is really coming along. I'm supporting 20x4 at the moment but it wouldn't be too hard to support others.

I've updated the GitHub project too. Nothing too fancy but should be easy to follow as I like to document very well.

Eventually, I hope to reserve an 80 byte buffer that is linear so that you can just peek/poke into it and the LCD will be refreshed in the background. Would be really useful in BASIC too.

https://github.com/cbmeeks/Potpourri6502

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Cat; the other white meat.

Nice job on the libraray.

If it may be of any help... here's an HD44780 DDRAM Memory Map diagram I did awhile back for a 4x20 display.