[Skabana159]

What I have done in the past is quite different than your approach. Two years ago, while writing an auto-balancing routine, and last year for our gear-switching routine, I used an entirely seperate serin/serout loop. This is a sketch of what it might look like, if you were to set the motors to go forward for, say, 40 loops of time. Let us then assume that after 40 loops, it goes back to human control and your regular default program loop, called mainloop.

loopcnt var byte 'a byte to count loops by
loopcnt = 0
autoloop: 'our loop for autonomy
serin 'this takes data from sensors, get the right syntax from
the default program.
PWM1 = 254
PWM2 = 254
loopcnt = loopcnt + 1
if loopcnt = 40 then mainloop
serout 'this sends data to relays and speed controllers. get
syntax from default program
goto autoloop

I would not bother with the middle man of your joystick variables, p2_x and p2_y. Simply go straigt to your motor output variables, PWM#, or whatever meaningful alias you would give to them. The default program does warn against having more than one serin statement. It is okay as long as they are in seperate loops.