This is from the Operator Interface reference guide at
http://www.ifirobotics.com/oi.shtml.
Pin 1: +5 Volts
Pin 2: Joystick Trigger Switch
Pin 3: X-Axis
Pin 4: Ground
Pin 5: Robot Feedback LED Driver
Pin 6: Y Axis
Pin 7: Joystick Thumb Switch
Pin 8: Robot Feedback LED Driver
Pin 9: Robot Feedback LED Driver
Pin 10: Aux Switch 1
Pin 11: Aux Analog
Pin 12: Ground
Pin 13: Wheel
Pin 14: Aux Switch 2
Pin 15: Robot Feedback LED Driver
On ports 2 and 4, pins 5, 8, 9, and 15 imitate the trigger, thumb, aux 1, and aux 2 on ports 3 and 1 respectively.