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Analog Stick ContactsThe joystick contacts on the motherboard can be wired to external potentiometers to provide analog input. If you aren't familiar with how this type of potentiometer based joystick works, here is a basic summary. Potentiometers are variable resistors, inside them is a resistive material with three pins connected to it. On either end of the resistive material are the power and ground pins, these typically remain at a constant voltage. The third pin is called the wiper, this is just a piece of metal that can move along the resistive material (in this case the wiper is attached to the arm of the joystick). As the wiper moves closer to ground the voltage read from this pin approaches 0, as it moves closer to the power input the wiper voltage approaches whatever the supply voltage is. When the wiper is directly in the middle, its voltage will be half of the input voltage (in accordance with Ohm's law). By reading the voltage on the wiper pin, the psp is able to determine the position of the joystick at any time. Two different examples for providing analog input are shown in this post, one using an MCP4251 digital potentiometer, and another using hardwired Ps1 controller joysticks. When looking at your PSP motherboard in the way it would normally be oriented while using the PSP, the analog connections are as follows: [[ ] ] =GND[ [ ]] =X-Axis [[ ]] =+2.5v[ [ ]] =Y-AxisThe 2.5v supply to the joystick is not constant, but pulsed for approximately 200µs at 130Hz, this can be seen in the oscilloscope view below. These 2.5v pulses are only present when the running application requires input from the joystick, otherwise the joystick supply will be at a constant 0v.