The Pinout

PinFunction
1+5VDC Source
2/A (stick 1 button 1)
31X (stick 1 horizontal)
4GND
5GND
61Y (stick 1 vertical)
7/B (stick 1 button 2)
8+5VDC Source
9+5VDC Source
10/D (stick 2 button 2)
112X (stick 2 horizontal)
12GND
132Y (stick 2 vertical)
14/C (stick 2 button 1)
15+5VDC Source

Every GND is the same. Every +5V is the same.

Analog Direction Inputs

Potentiometer inputs are 0-100kohm, linear. Directional inputs are read by a RC delay circuit, i.e. the time it takes a capacitor to recharge after being discharged determines the potentiometer positions.

Buttons

Button inputs have their pins held high by the computer, and are pulled low by the joystick when activated by the user.