Despite the fact that the SAMv71 on the Xplained Ultra has tons of I/O, it was a challenge finding the kinds of I/O needed for this project that were accessible via connectors on the board.

I was originally going to plop an Arduino-compatible motor controller in the appropriate connector space on the Ultra, but turns out that the Arduino pin-out wasn't followed 100% so some functionality wasn't available where I needed it.  But I was able to find mostly what was needed on the two EXT connectors, with just a few pins being pulled from the Arduino's Analog Low connector.