For the serial tidbit you can't; it's one bit of data in and one out every time you send the data. So, you must send then change the data, send again, etc. That is why FireWire and USB aren't huge cables, they use serial arcitectture.

To test it, make it transmit a bit, make the electronics at the other end loop back to the input, and then when you recieve the input bit write what you got.

Cheers

I'll try to see what's with your project...