How are the many signals of a N64 or Wii joystick sent to the console by only 2 wires?



  • I am curious as to how only 2 wires (perhaps 3 or 4) inside a N64 or Wii gamepad are able to send the many signals of the different inputs at once.

    It used to be that for just one ON/OFF input, we needed two wires. So why does it not take dozens of wires for the many inputs on a modern gamepad?



  • So the Wii Joystick uses a Blue Tooth interface which is a little different than the N64 controller. As a result this answer deals more with the latter than the former.


    The N64 controller uses a single transmission wire on which it encodes bits to send signals back to the N64 console. To accomplish this bits are encoded on that wire as follows:

    alt text

    This encoding can then be used to multiplex the connection and allow 32 bit communication. In the case of the N64 controller these bits are encoded thus:

    0   A
    1   B
    2   Z
    3   Start
    4   Directional Up
    5   Directional Down
    6   Directional Left
    7   Directional Right
    8   unknown (always 0)
    9   unknown (always 0)
    10  L
    11  R
    12  C Up
    13  C Down
    14  C Left
    15  C Right
    

    With the remaining 16 bits being used for the Analog Joystick (providing 8 degrees of control).

    More over, certain codes are transmitted for specialized function:

    To Init: send 03 80 01 followed by 34 80's
    To Start Rumble: 03 c0 1b followed by 32 01's
    To Stop Rumble: 03 c0 1b followed by 32 00's
    

    You can find more information in this vein here



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