Given an Arduino Mega with a genuine Arduino motor shield

Motors will be powered at 80 percent voltage

Input pins are 48, 49, 30, 26, 24, 22, 46, 47, 27, 25, 23, 45, 43

Output pins are 4

Motors are initially off

There are three stages:

Stage one starts when pin 45 goes high. Remain in stage one until exit condition is met:

Stage one:

If pin 25 is high, both motors on forward

If pin 27 is high, right motor forward and left motor reverse

If pin 23 is high, left motor forward and right motor reverse

If pin 43 goes high, exit stage one and start stage two

Remain in stage two until exit condition is met

Stage two:

Both motors off for 5 seconds

Both motors reverse for 5 seconds

Right motor forward and left motor reverse for 3 seconds

Stop both motors

If pin 24 is high, both motors on forward

If pin 26 is high, right motor forward and left motor reverse

If pin 22 is high, left motor forward and right motor reverse

If pin 30 goes high, exit stage two and start stage three

Stage three:

Stop motors

Make pin 41 high for one second, then low

Delay 23 seconds

Both motors reverse for 5 seconds

Right motor forward and left motor reverse for 5 seconds

Both motors off

Return to original condition, waiting for pin 45 to go high