fyi
Begin forwarded message:
From: Andy Green <[EMAIL PROTECTED]>
Date: March 9, 2008 6:50:31 PM GMT+08:00
To: "Carsten Haitzler (The Rasterman)" <[EMAIL PROTECTED]>
Cc: Wolfgang Spraul <[EMAIL PROTECTED]>, Sean Moss-Pultz <[EMAIL PROTECTED]
>, William Lai <[EMAIL PROTECTED]>, "Tony Tu)" <[EMAIL PROTECTED]>,
matt_hsu <[EMAIL PROTECTED]>, Chia-I Wu <[EMAIL PROTECTED]>,
Werner Almesberger <[EMAIL PROTECTED]>
Subject: Re: LCM flicker
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Somebody in the thread at some point said:
hhmmm. then xrandr is lying to me, it claims 50hz. aqnd it claims
25hz for
landscape mode (which explains the much worse flicker).
It is true that landscape is 1/2 the rate of portrait currently, but
680
x 600 (the overscanned y and x) at 24.5MHz PCLK (41ns period) comes
out
to 16.6ms == 60Hz.
Either the refresh action we perform "beats" against another
oscialltor
inside the LCM ("booster" or this "internal" osciallator), or there
is
some kind of PWM trickery used to get the intensity levels that we
beat
against somehow.
i haven't found a pathological pattern yet - but it seems a smooth
gradient - in
ANY direction seems to bring it out. that doesn't help me figure
out what kind
of pathological pattern is causing it. for that matter a solid
orange color
region flickers too - all by itself. no gradient needed.
rgb: 255 145 0 does a wonder flickering job. this is totally
bizarre unles u
look at there being some temporal interference pattern on the r &
b signals
that doesn't affect g, and the interference pattern is inverted
between r & b.
Hum well it is a big clue for sure since we can make the problem come
and go depending on colour. I guess the first question we should
ask is
can the glamo being doing it really early in the actual pixel data
frame
by frame. I will try to fill the display with this colour and have
a look.
Another thing I noticed is that we have an insane RC filter on PCLK
currently, the signal quality on PCLK is pretty bad. But I can't
make a
story how that causes these outcomes.
- -Andy
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