Also: test the microcontroller module before you install it into something. Somehow this Teensy has no 3.3V on it's internal regulator and I have no idea if it was like that before I soldered it in or whether my board is shorting something somewhere. These are all things that I did know once, but it's been a while and I've filled by brains with other things since then :/
And finally: just because you have something in your parts drawer that you'd like to use doesn't mean it's the right design choice >_<