I solved my version of this problem.
First, I checked that the UARTSBee was working by using a terminal emulation app, and connecting the RX/TX to check for an echo.
Second, I realised that it was possible the ATMega on the controller board didn’t have any boot loader code, or if it did, it was corrupt.
So I flashed it using another Arduino Uno (remember the capacitor across reset and ground).
<LINK_TEXT text=“https://learn.sparkfun.com/tutorials/in … loader/all”>https://learn.sparkfun.com/tutorials/installing-an-arduino-bootloader/all</LINK_TEXT>
Finally I made sure to the use the latest library from GitHub. I’d been using an older one which didn’t work.
https://github.com/Seeed-Studio/Hercules_Motor_Driver
Of course. all this would have been unnecessary if there had been proper documentation!