Autonomous Code
 

Anyone have any info on how to program this? Does it just run the mainloop without regards to the SERIN command?

Somewhat yes, somewhat no.

Basically, it runs the program loop exactly as if it was in non-autonomous mode. The only difference is that all the variables from the OI (p1_x, p1_y, p1_sw_trig, etc) are set to 127 or 0, depending on whether it is an analog or digital input, respectively. The inputs on the RC (rc_sw1, sensor1, etc) still contain the correct values.

One of the bits of the competition mode byte is also set but I can't remember which. It's documented in the default code if you need to know.