Yeah, I've been a bit worried about that too - unitech is completely unhelpful with respect to their device's operation. I hoped/assumed since retry is part of the PS2 specification the device would honor it, and it seems to work. Though I don't have a reliable method to check its operation.

I had considered a non interrupt approach but I'm not sure how that would look, as I've also got to poll a keypad, so I really need a way to quickly and robustly check if the reader has anything to send.

I suppose I could stay in the interrupt to collect an entire byte at a time? and only set my CHAR_RCVD flag once I've got an ascii char.. But I still run into the buffering problem.

I'll try that approach.

thank you.