Having replaced the electronics in a BigTrak junior, I needed some way to control it from my BeagleBone. Initial experiments with driving the L293D directly from GPIO pins were quite successful but I quickly discovered the opto-encoders on the toy were extremely high resolution and needed some proper real-time interrupt based handling. Doing this from the high-level Linux based environment on the BeagleBone just sounded too much trouble to me so I looked around for something a bit lower level to handle the opto-encoder tick counting. I was torn between an Arduino Uno and the ChipKit Uno. In the end I went for the ChipKit for two reasons, the BeagleBone I/O is only 3.3V and not 5V tolerant at all. This would have meant level translators were required on any interface between the Arduino and BeagleBone, but the ChipKit is already 3.3V. The other reason was at full speed the motor encoder ticks come through about 1200 times a second, with two that means about 2500 interrupts a second. I've got no idea how big the interrupt overhead is for the Arduino but I thought if I handle 16 or 32 bit tick counters in the interrupt with that frequency it is going to get a bit close to the limits of available CPU cycles, the ChipKit is 32bit and has an 80MHz clock so plenty of time to do all I needed. The features I've used are all available on the Arduino, due to some pin function constraints you'll need to swap around the pin order a bit but the code should work okay on an Uno (provided it can keep up).