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[Lcdproc] hd44780 weird display/driver problem


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  • From: nchidsey AT bw.edu (Nick Chidsey)
  • Subject: [Lcdproc] hd44780 weird display/driver problem
  • Date: Mon Oct 7 21:28:02 2002

> 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
> 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).

I have a 40x2 display, not 40x4. I added most of your patch manually, I
did NOT add your separate driver, but added the rest of the code to the
other files, and I just continued to use the 8bit driver. However, your
initialization code that is in hd44780.c is only used if the lines are > 2,
and since I only have 2 lines, they are not used. So in fact I've just used
my own code for addressing, and I tried everything I could manage in terms
of initialization code. I've tried anywhere from 1 to 6 times of the
funcset command with all combinations I could think of with 8bit and/or the
TWOLINE and fontsize bits. I never found a combo that worked. Some
combinations displayed line 1 perfectly with no second line, but most (as
could be expected) did nothing.

> 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.

I bought mine on ebay, and the seller gave me the url I posted. That url
says that it works for all "DMC" models, and my display is labeled Optrex
DMC2066, that is all I can tell you unfortunately, besides the fact that
the chip is labeled HD44780A00 with an S in the top right corner :(

-nick






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