Hi!
Brief update. First, I have found that I have a newer version of the firmware than reported on the SX100 wiki page (see page for details). Disappointing that Canon did not release an updater for people with older firmware versions. Hopefully we don't have to port CHDK twice after getting it working with DryOS (presumably that is what lives inside the camera)...
Second, I have got my camera into an infinite loop. I have also confirmed the LED addresses with the program that blinks the LEDs. More importantly, I have compiled the blinker program and watched the AF light blink away. A firmware dump is hopefully not too far away. First I must cook up a simple circuit (I have photocells (aka LDRs), not photodiodes) that outputs a mic level signal.
Great news, so your camera seems to respond ... Mine has the same fw as stated in the Wikia CHDK SX100 page ... I've only a "lens" error E18 in addition, nothing too bad I hope ...
BTW, I don't know if LDR are fast enough for your purposes ... if I rememeber right they have a response time of something like tens of milliseconds, way too slow for something like some kilobits per seconds as transfer speed ...
Anyway, next week I'll be back @work, where I can easily find all the necessary photodiodes ;-)
@fiamazo: you have done all the correct steps, but one detail might be wrong. The address at which you must enter "BOOTDISK" is might not necessarily be where AA 55 occurs. What I did was got to location 0x40 and just enter BOOTDISK, as in this thread:
http://forums.dpreview.com/forums/readflat.asp?forum=1010&thread=24983823&page=1
Ok ... I read somewhere that the boot sector was marked by the AA 55 sequence, I'll try with your address ... thanks!
One other thing I did was to fdisk the card and toggle the bootable flag for the partition on the card. I don't know if this made any kind of difference.
I did the same, with no success ... but I think it's related to the wrong BOOTDISK, plcace ...
Thanks again, I'm so happy that there's some brainstorming around the SX1000 ;-)
Cheers,
fiamazo
EDIT: Great! I "hanged" the camera in the while loop ... now it's time to make it blink ... fiamazo