So we bought a motor driver for which unfortunately we let the purple smoke escape and we have decided to embarked upon the dark dark road of building our own primitive motor driver.

Do not do this. Just buy a better one.

Unless your goal is to have a learn or show off the DIY motor board, no one will be impressed. It’ll be a bitch, will cost just as much, not work all that great probably, and suck the enthusiasm out of the real project (In this case a murderous axes robot).

Anyhow, we had a little adventure with the book Practical Electronics for Inventors. We found a diagram for an h-bridge.

It was a boondoggle. The resistors were probably wrong and the P-channel mosfets were written with source and drain switched.