From: "Chuck Meade" <chuck@ThePTRGroup•com>
To: "Mark Chambers" <markc@mail•com>,
"Fend, Matthias" <mfend@harris•com>,
<linuxppc-embedded@ozlabs•org>
Subject: RE: mpc8xx and LCD
Date: Thu, 29 Sep 2005 13:31:52 -0400 [thread overview]
Message-ID: <IIEEICKJLNEPBBDJICNGMEIAIMAA.chuck@ThePTRGroup.com> (raw)
In-Reply-To: <00c501c5c504$96c59780$0301a8c0@chuck2>
> >>Can you send a couple of links to the modules you are considering?
>
> >there are some 320x240 from EDT (Emerging Display Technologies) with
> S1D13305
> >S1D13700
> >http://www.actron.de/graphic_displays_edt.htm
> >
> >also from Powertip a 320x240 with S1D13305/ S1D13704 is available
> >http://www.actron.de/graphic_displays_powertip.htm
> >
> >and also from ampire is one ... (available /w or w/o Epson's S1D
> controller)
> >http://www.ampire.com.tw/AmpireCatalogue/P082-AT320240Q3.pdf
> >
>
> Ok, I see the problem with the S1D13305, but the S1D13704 looks ok.
> In order to work as a linux framebuffer, the cpu must be able to directly
> address
> pixels. You can't have a controller like the 13305 that makes you write a
> pixel address and then write the pixel. A controller like the 13704 just
> makes
> the pixel memory look like RAM, so it's easy to interface.
I have done this in the past when the cpu could not directly access the
pixels. I created a virtual framebuffer in RAM, and had a timer-driven
routine that regularly sent the contents of the virtual framebuffer to
the LCD device through the "register bottleneck" of the LCD device interface.
It actually worked well. I expected a big performance hit with all the
additional bus activity, but it was not bad (no, I don't remember any
numbers). The platform had a 48 MHz mpc8xx if I remember correctly,
and the LCD device was an old Epson chip that had a registered interface
(no direct access to pixels).
It is not an optimal situation, but if you find yourself stuck with an LCD
device that does not provide a RAM-like interface to the pixels, then it is
at least a known-working solution.
Chuck Meade
The PTR Group
next prev parent reply other threads:[~2005-09-29 19:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-29 13:45 AW: mpc8xx and LCD Fend, Matthias
2005-09-29 14:44 ` Mark Chambers
2005-09-29 17:31 ` Chuck Meade [this message]
-- strict thread matches above, loose matches on Subject: below --
2005-09-30 11:07 AW: " Fend, Matthias
2005-09-30 12:50 ` Mark Chambers
2005-09-29 6:53 Fend, Matthias
2005-09-29 12:52 ` Mark Chambers
2005-09-29 14:03 ` Dan Malek
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