hello, i am attempting to dump the firmware from a sd900. i got some phototransistors and have them connected up to the mic input of my machine. but while testing i am not getting any audio signal. the mic port is operational, tested with actual microphone.

is there something i am missing?

photodiods/transistors bought 1 2 3

I can't help you with your problem, but I would suggest that you post this question in the DpReview CHDK thread in the Canon talk forum. Its a pretty high traffic area, and is more likely to get noticed by someone who has done it before. Here's the link: DpReview CHDK thread. (Make sure you change the message subject so it telegraphs your need for assistance)

I also copied the text of your original message above to a new SD900 development page. you can find that here, and added a link to it on the For Developers page. It would be helpful if you could document on that page what you have done so far.