The Uno is a nice part, but if the target is small look at the Nano, it is smaller, lighter and probably less money. As far as the CROSSFIRE end I have not worked with it before. I looked and found a lot of different things with the same name. You might want to post a link to your parts showing technical information. Can you post a simple schematic or block diagram showing how this goes together. Please a hand drawing is much better then a frizzy picture.