Get a Makelangelo robot with the firmware already loaded.

Connect the white/red/black servo extension cable coming from RUMBA board EXP3 pins 2/4/6 to the servo connector.

do NOT connect to the 12v/5v pins on the right of block EXP3

Match the servo extension cable black wire to the servo red wire.

Match the servo orange wire to the extension white wire.

Turn the robot on. The robot will drive the output gear to 90 degrees automatically.

Turn off power and disconnect the servo.