Today I was able to check out a few major milestones today. The first is that I determined that I can indeed control the steering servo and ESC via the ARM processor. I was a bit worried that they would not take a 3V3 signal over the normal 5V0. But I can put that worry behind me.
The second milestone was my first test of controlling the steering as a function of cross track error. Although I initially got the sign backwards, as I moved the robot from one side of the course to the other, the steering wheels turned appropriately. Admittedly this was a horribly simple test, but it dis verify the basics of a whole bunch of math.
Next major milestone is to get something to provide a heading (gyro, GPS, magnetometer, …) to start working on the steering and waypoint navigation logic.