Table 1—Here’s a look at the pin assignments for the M68HC908GP20 onboard the Roboat. Serial GPS data for heading calculations is on PTE1.

Pin        Function
PTA1     SW5 disables GPS course updates (Roboat test mode)
PTA2     SW4 disables compass course updates (Roboat test mode)
PTA3     SW3 copies the present compass course into the GPS course (Roboat test mode)
PTB0     analog input from the trimmer that adjusts the central position of the rudder
PTB1     analog input from the digital compass Hall sensor 1
PTB2     analog input from the digital compass Hall sensor 2
PTC2     output, switches the electric motor and propeller (1 = off, 0 = on)
PTC4     output, powers down the GPS (1 = off, 0 = on)
PTD4     output, controls the proportional servo and rudder
PTD6     output, blinks the red led each time correct data from GPS are acquired
PTE1     input, receives serial data from GPS