I think I will use different motor drivers. I think that the UC3517 will work best as a stepper motor driver in this app. It will deliver about 3-times the current necessary to drive the motors, and has a simple imput logic control.... afterall, I don't want my PIC spending much time controlling motors. After my main processor, I think I will use a Microchip 16F648 to control the UC3517. Using the 648 to control subsystems simplifies things, but could slow them down too, but I doubt there will be a perceptable lag in performance. However, at this stage of development, performance is not an issue. Safety must be the primary attribute, followed by reliability, and then performance. If attribute 1 and 2 cannot be accomplished, #3 is of little importance. But enough of philosophy. The hardware can be accomplished in several ways, but the above shows a simple and totally practical way of achieving what is to be done with this robot. I come up with new tasks for it daily.