Hi, I am currently working on a small mobil robot platform based on this twin motor gear box. http://www2.towerhobbies.com/cgi-bin/wti0001p.pgm?Q=1&I=LXHA15&P=7 I plan on either hacking the slotted encoders from a mouse, or using Roman's Encoder-less speed control. http://www.romanblack.com/encoder.htm I plan on using one F628 @ 4mhz and an one L293D to control both motors. I assume using the int on change function for port B would be the best way to measure the rotation of both encoders ? If I use int on change and both encoders change will I continualy miss one int to service the other ? Will this cause me to interpret the distance travled incorrectly ? If anyone has suggestions or examples of a similiar project, they would be appreciated. Thanks, Kevin -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.