LCM flicker

Carsten Haitzler (The Rasterman) raster at openmoko.org
Mon Mar 10 03:05:25 CET 2008


On Sun, 9 Mar 2008 21:53:24 +0100 joerg <joerg.twinklephone at gmx.de> babbled:

> > I took an LCM to pieces and there is one chip in the whole thing.
> We both know this means nothing nowadays ;-)
> 
> When i heard of red-only flicker (i own no NEO at all, so i'm sad i can't 
> reproduce), i had another look to the c-ds, and i see (p.7) the Red4 and Red5 
> data lines to be rerouted, by a strange redesign for GTA02 (probably to save 
> an R-Array chip), through U6002 (LPF?!?), whereas same datalines go to 
> R-array(! NO LPF) RP6005 in GTA01. Well i'm wondering... 

actually got blue flicker as well. interestingly if the signal to the actual
lcd (so this is internal to the lcm now) has both red and blu of equal value,
flicker stops. something about deliering both r and b signal either stops it or
somehow cancels it out/nullifies it in some way. green does not (seem) affected.

one thing it could be is the LSB of all channels is wobbling, and since R & B
have 1 less bit - it's much more noticable. green might flicker and we just
can't see it. what beats me though is the signal to the lcm is digital, so it's
not an analog interference pattern in alalogue data. you may have something
with your red4/5 there. check blue as well.

but here is what i do know for sure:

flickers:

RRGGBB (convert to 16bit RGB565 with bitshifts as you like)

  ff0000
  ffff00
  00ffff
  0000ff

does NOT (perceivably) flicker:

  ffffff
  00ff00
  ff00ff
  000000

nasty examples of clicker that are easy to visibly see:

  ff9100
  0091ff

somehow i am really dubious as to this being a glamo issue - it could be with
it sending wobbling bits on the LSB's of R & B - even G, but we don't notice it
due to it being half the magnitude, but this doesn't match with the result of
ff00ff or ffffff NOT flickering.

> Anyway i agree, it's best to "fix" the glamo, better than to hack the LCM
> 
> cheers
> jOERG
> 


-- 
Carsten Haitzler (The Rasterman) <raster at openmoko.org>




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