Hacking the Xbox 360 controller

Step 3 Theres two traces for each button! WTF?

The switching is done differently on the 360 controller. There will be two traces for each button. We can't just ground/pullup one trace to make the X or Y function happen.

The trace on the left of the button will transmit a signal to the trace on the right of the button. This is important. As discussed before, the optocoupler is unidirectional. Do you see what I mean?

So for a common 6 pin photocoupler, such as the 4n27, pin 5 is the phototransistor collector. This must attach to the left trace for the respective button. Pin 4 is the phototransistor emittor. This has to be connected to the trace to the right of the button.

Now pin 1 of the coupler is the anode of the light emitting diode that is hidden inside of the chip. This means we can attach pin 1 to our positive rail.

Pin 2 is the cathode. So we can attach this to our chip... But wait a minute. If we won't put a resistor in there, somewhere, we will burn out the diode or our microcontroller.

Pin 3 is normally unused, so we can solder a small smt resistor between pin 2 and pin 3. Then we can attach out microcontroller output pin to pin 3 of the coupler.