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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: Wed Oct 2 22:46:01 2002

Scratch that... I'm almost sure it's the TWOLINE bit not being received
properly by the unit for whatever reason (wrong initialization steps?)
After reading the section on DDRAM addressing in my docs, i'm moderately
sure there's only 80 bytes (NOT 0x80 bytes) of dd ram. So the
HD44780_position() function should do (y*40) instead of hex. When I do
this, I see the first line perfectly! (now it makes sense to me, that i was
seeing the 17th+ chars of the second line overlapping the first line,
coincidently, the 17th char of line 2 was being addressed at 80, and I
assume the unit was wrapping that to zero. However, why only some of the
chars were from line 2 and others were from 1, i'm not sure, maybe the way
lcdproc only incrementally updates?)

So.. here are the docs I'm reading.
http://mywebpages.comcast.net/biglittlekid/systems/LCD_DMC_manual.pdf
Secion 1.7.4 (page 15) says there are exactly 80 bytes. This works with my
theory about the wrapping.
Section 1.7.6.3 (page 17) says line two starts at 0x40, but I think it's
just wrong given the symptoms.
Now the important part is page 32, where it describes the initialization
steps. Note the extra stuff that lcdproc doesn't do. I have all this (but
no uPause after the third FUNCSET|8bit).

Right now everything seems good except I dont get the PC-poweron black line
which I can deal with, maybe this unit just doesn't do that... and I
simply dont get line 2. What can I do about the initialization to try to
get the unit to see that 2lines bit? Any suggestions?

-nick






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