From what I can see, it communicates with the GameBoy in some sort of
digital-analog mix, and the image is interlaced. However, the voltages
to the actual LCD cells are fed in by the main board. These voltages
must be preceisly right (to an acccuracy somewhere below 0.1 mV; I
measured the min and max possible settings and they read as the same
value) or the LCD will flicker a lot, produce a terrible image and wear
out more quickly. There's a potentiometer on the main board that
controls this voltage. I'm not sure but I think it's kind of a DC
offset. I would think that this connects to the LCD as sort of a
driving current, which is modulated with the signal and sent to the cells.

I've never seen a good description of the GBA LCD circuitry, but it's
almost certainly based on the old GameBoy one. The original GB and GB
Pocket LCD communication is based in part on TV signal standards
(interlaced, refresh rate). Those screens could show 4 shades of grey,
which were encoded in two seperate signals, as a 2-bit digital value for
each pixel. The GBA can display color at 16 bit color depth. I doubt
that it sends 16 bits of data to the screen per pixel; my best guess is
that it uses something like RGB component video.

Maybe you or someone else can examine the signal sent by the GBA with an
oscilloscope and try to make some sense of it. It might be possible to
hook the camera reciever up to it directly if it has a component video
output. The refresh rate and (presumably) signal type are basically
correct, though you'd have to remove a few lines (TV is about 480 lines,
GBA is 160 lines) and probably split the H- and V-sync signals out.

Your best bet is probably a rather roundabout solution: Get one of
those GBA TV tuners and connect a TV format signal to the A/V in jack.
I have the old GBA TV tuner that they made before the SP was released,
and the SP won't fit in it. I had to chisel a bit out of the case
around the top of the GB connector and cut a bit out a the connector
board. Luckily, this only broke one trace wire, which I re-connected
with some solder and wrapping wire.

(On a side note: Why even use a GBA SP screen? There are plenty of
good small backlit TFT video monitors out there. For instance, I
recently saw a protable combination GameCube controller and screen
(about GBA sized) for $40.)

-Joe


amitpal singh wrote:

>Hi everyone,
> I'm currently working on a project for
>which i havet o connect a wireless camera receiver to
>the gameboy advance sp lcd screen. I was wondering if
>anyone could help me out with this issue. i have no
>schematic of the gameboy lcd neither the pinouts of
>it.
>i really appreciate any help i can get
>
>thanks
>Amit