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[Lcdproc] hd44780 weird display/driver problem

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  • From: bock AT (Goetz Bock)
  • Subject: [Lcdproc] hd44780 weird display/driver problem
  • Date: Mon Oct 7 20:56:01 2002

On Mon, Oct 07 '02 at 13:33, Nick Chidsey wrote:
> > Now, what's the matter here. An HD44780 HAS 80 bytes only. It can work
> > with two 40 char long lines. However, the data of the second 40
> > characters starts at address 64 (0x40), not 40 ! So there is some kinda
> > gap of 24 bytes. That means that 0x40 in the code is correct.
> I have to disagree... 40 bytes starting at 64 far overflows the 80 bytes of
> memory it has. On my unit anyway, [ ... ]
As we have discussed on this list recently there are some "HD44780
compatible" units that are not quite 100% compatible. I've a 20x4 that
has a HD66712U controller, that is claimed to be HD44780 compatible, but
it's not. I've written a patch (that's inclusion is currently discussed
in a different thread) that does the following:
- define a "aType" boolean, it it's false normal HD44780 initialisation
is done, if it's true:
- change the addressing sheme from 0x00, 0x40, 0x10 (or 0x14), 0x50 (or
0x58) for 16x? (or 20x?) to 0x00, 0x20, 0x40, 0x60.
- does some special initialisation to enable the 3/4th line.

Your 40x4 apparently is organised as a: 40x2
so if you don't get a seccond line, maybe you need a patch simmilar to
mine to enable the 2nd line (what would be the same character positiones
as the 3/4th line on my 20x4).

Do you happen to have the datasheed for your display, the one you posted
looked a lot like the regular HD44780, but I only skimmed through it.
Goetz Bock (c) 2002 as - Munich - Germany /"\
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