SurferTim:
That is the next question. I would use the same testing procedure on the speed. Change the PWM cycle time on only one of the motors. Run it slowly up to full speed and back down to stopped with the PWM. Then try the other motor. Don't mess with the direction, just the speed. How does that do?
Not sure if I fried my motor board today,
and looks like the left motor channel got some problem, it only spins one way, when the sketch switch the input and tells it to reverse, the motor power led is on but it isnt spinning in reverse.
My arduino was powered by USB before when I tested the motor board, and the motor board connects to the 5V and GND of the arduino, with external lipo on the other side
Today I tried to plug a 12V DC power supply on the arduino board, then one channel start to behave strangely.
Then I tried switching digital pins and motors, it seems that one motor channel is having trouble going backwards