[CronusWorks]

We used a Pololu A-Star 32U4 Micro (essentially an Arduino Leonardo) with our LEDs this year, and fed data to it from the serial port on the MXP without a level shifter (not actually necessary in this case). We only connected TX from the RoboRIO to RX on the Arduino, it was not bidirectional.

I don't know exactly how they coded it on the RoboRIO, but it just spit out a single byte every time it ran through the control loop and never had any of the issues you mentioned.