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Re: lcd fun

From: Doug Sutherland <>
Date: Wed, 04 Sep 2002 17:06:04 -0500

Roger,

> I eventually soldered a chunk of laptop hard drive cable
> on and crimped onto that.  Tedious.  Very very tedious.

I've done this quite a few times. Remeber that data moves
very high speed over those wires. Crimping may not be
the best way. I did the same, soldering onto hard drive
cable, that works. Yes it's tedious, mindless work, but
it builds wearable-character <g>

> I have picture!  Yay!  Colors seem correct.  Can't get the
> backlight to fire up yet because it needs a rather thirsty
> 5A at startup (3A continual).

Wow, that a lot. I have run a VGA LCD with CCFL backlight
along with laptop hard drive, PCMCIA module, and even
other accessories like GPS and such. The only thing that
choked my system was trying to power a PCMCIA CDROM
drive from the PCMCIA slot while running the LCD.

> Unfortunately, the picture is not centered correctly in the
> screen.  It starts about 1/3 of the way down, and wraps
> around the top a tiny bit. The display is capable of 640x480,
> 640x400, and 640x350, depending on the polarity of the
> sync lines.

> It seems like it would default to 640x480, but who knows.
> And I would assume that the Advantech would also default
> to 640x480.

This is a BIOS thing. The standard VGA BIOS works with
my LCD, fortunately.

> So I'm currently assuming that it isn't a resolution mismatch,
> but rather that the timings are just off a bit.  (And until I learn
> how to get the console to boot in a non-standard display
> mode, I'll stick with this theory!)

The BIOS specifies the video timings. Sometimes the BIOS
needs to be tweaked for new timings, to work with different
LCDs. This may not be the problem, but then it might be.

> I remember dinking with timings by hand in an XF86Config
> file back in the day, but I have no idea what to do if the basic
> vga isn't in sync.

Before considering x-windows, the console should look
proper on the screen. If the console doesn't look right at
boot time, then tweaking x isn't going to fix that problem.

> Any suggestions?

Which LCD is this, do you have the data sheet, and are
you certain that the pins are mapped correctly, and that
you have good solder joints? Poor solder joints or even
attenuation of signals due to long cable length can screw
with things. How long is your cable?

  -- Doug

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