Hi everyone!!

Thanks so much to everyone who made all the suggestions on this topic.
We're almost to implementation now, so I'll have to let you guys know how it
went.. And of course, all my source code will be available once it works, so
if anyone wants to use a Gameboy camera for a project, you might be able to
after all this is done.

So here's the general operation for what I'm planning to do.

(1) Startup sequence:  Clock in 8 registers (8bits each) serially in
succession into the camera. This sets up the various modes of operation.
Then you have to trigger it once to begin the exposure, wait for the
exposure time (tricky part here, especially if not clocking at the spec'd
500kHz!) and then start clocking out the analog values corresponding to the
pixels.

In case anyone has forgotten, the problem is to read and store 128x128
analog -> digital values for later sending to the PC.

(2) For clocking out the analog values, we set up some kind of DMA-type
system.  128x128 = 16384 = 2^14, so 14 bits of counter hardware will do
nicely to auto-increment the SRAM address.  The SRAM is a 70ns 256K (32Kx8)
chip.  We're using the only National A/D converter in a DIP package (that we
could find) that runs at less that 2us (500kHz) so that we can have the full
bit-accuracy of the ADC (although it's probably not necessary, anyway).  So
we set up the PWM on the PIC to run this so-called DMA system. Hopefully we
can get some kind of overflow signal from the counter (maybe 15 bits of
counter, in that case).  At 20MHz, the PWM happily (register = 9, duty cycle
reg = 5) runs at 500kHz, 50% to do all our clocking.  Then that overflow
signal, we can attach to an input, and poll, so that we know when to stop
sampling and send the data to the PC.

Well, if anyone has any questions about this, just let me know!!

I was hoping to implement a FIFO-system, but I couldn't find a decent FIFO
for the application.. 16Kx8 is a big FIFO, apparently, and availability in
DIP parts for any kind of memory seems quite poor (unless you want to pay
around $50CDN).

Thanks again for all the help in the past!

- Wade

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