Will a ULN 2803 (8 darlington drivers) protect its inputs from back-EMF? In the case of a PIC driving a 2803 which drives the stepper motor coils, is there any danger of hurting the pic? I have mounted 2 5-wire stepper motors on a chassis (steering by differential drive). 4 PIC pins will drive both motors, with 2 XORs and 4 Inverters to derive the other signals for bi-phase (uni-polar) drive (0011, 0110, 1100, 1001) from (00,01,10,11). I will be trying the motors out with my parallel port first, to get the hang of them. Will any spikes get back to the PIC? Should I stick a 0.1uF or uF cap on each of the 4 PIC pins? Would the values of capacitance required depend on the speed of the stepping motors? Would opto-couplers be justified? What have I not considered? Any suggestions appreciated.