Thanks, NewInnovators - When I put the arduino in mbot mode (which is where I would like to use it) and check both the MakeBlock and Arduino extensions, then setting M1 digital pin 5 runs one motor (M1) and setting digital pin 6 runs the other (M2). Looking at the code for MeDCmotors, one pin is used for each motor, and a second pin reverses the motor. Setting pins 4 and 5 makes M1 run the other direction, but I have not been able to identify the pin that reverses M2. In the mbot mode, it seems unlikely that pins 9 and 10 would be used, because they are brought out on the RJ25 plug 1, and monitoring them when using the mbot motor commands shows no activity. It appears that 9, 10, 11 and 12 are not used for simple commands (although the distance sensors plug into RJ25 port 2), so I will try running the stepping motors driving the wheels with 11, 12, and 4 (or 5). Further information about this, perhaps especially from the MakeBlock staff, would be really appreciated.