HowStuffWorks Autopsy:
Inside an Xbox 360 Controller
No matter what they look like, most game controllers do the same thing. They translate a person's physical movements into ones and zeros - the language of computers.

An Xbox 360 controller has a D-pad and lots of buttons, like the Guide and A, B, X and Y buttons. These buttons don't look exactly alike, but they all work in the same way. When you press a button, it presses a switch that completes a circuit on the printed circuit board (PCB). With the exception of the shoulder and connect buttons, which use small, spring-loaded switches, the buttons use rubber dome switches. When you press a button, the dome's hard center completes a circuit. When you let go, the dome pops back up, breaking the circuit.


Look closely and you will see the rubber dome switches, the printed circuit board and more!

This is digital information - the circuits are either open or closed (1 or 0). Thumb sticks and triggers, on the other hand, are analog. Instead of just being on or off, they create a continually varying wave of electricity. These controls use circuits with variable resistors, and moving them changes the amount of resistance. This changes how much current travels through the circuit. For example, in a racing game, you can turn more sharply the farther you move the thumb stick. This electrical signal is an analog wave rather than a simple one or zero.


The switches up close
The controller's processor monitors all these circuits and knows which one corresponds to which button. A digital-to-analog converter lets the controller use radio waves, which are analog, to send this information to the console. It's up to the console to change the analog signal back into digital information it can use.

The controller also gives feedback to the player. Two small motors make the controller vibrate based on what happens in the game. Each motor spins a small weight, which shakes the controller. An accessory port also lets a player plug in headphones and other accessories.

Unlike wired controllers, which receive power from the console through a USB port, this controller requires batteries. A special kit can connect to the port in front of the controller to recharge them.


The accessory port
Here's how it all comes together: The first time you use your wireless controller:

  1. You install the batteries, press the Xbox Guide button and turn on your console. Four LEDs make the Guide button light up.
  2. You press the connect button to synch the controller with the console.
  3. You play your game, and the controller's processor monitors the circuits through the PCB.
  4. When you press a button, it closes a circuit.
  5. When you use the triggers or thumb sticks, the processor monitors which ones you use and how forcefully you use them.
  6. The controller translates all of this information into an analog signal and transmits it to the console using radio waves.
  7. The motors spin their weights based on what happens in the game.