Re: [PARPORT] Parallel port joystick problems

From: Matt Roberds (
Date: Thu Feb 15 2001 - 20:37:40 EST

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    >Date: Thu, 15 Feb 2001 14:34:28 +0200
    >From: Jari-Pekka Heini <>
    >I have attached a NES controller to my parallel port. Controller works
    >fine except one thing: I can only press two (2) buttons at a time. If
    >I press more than 2 buttons simultaneously, some of the buttons will go
    >off. I've tested this joystick in my friend's computer and it works for
    >him (he has the same build of the drivers and same kernel).

    I think NES joysticks actually speak a serial protocol instead of
    having discrete analog and digital inputs like PC joysticks. In
    other words, there is a microcontroller in them that needs reliable
    power to work right. Parallel ports don't have a "power" pin and
    can't provide much power from the data lines - you might be having
    trouble with the NES joystick drawing too much current from the
    parallel port. The amount of power the parallel port can supply
    varies with the port design, which could explain why it works on
    your friend's computer but not on yours.

    If this is the problem, you can probably verify it by connecting a
    voltmeter across the joystick's power and ground pins and watching
    it as you press various buttons. Or, try running the joystick's
    power line to a source of +5v power (try the PC joystick port,
    mouse port, keyboard port, or even a spare disk drive power connector)
    and see what happens. If this is not practical, maybe you'll have
    better luck with an add-in parallel port card or a different card
    than the one you are using. If nothing else is practical, you might
    try connecting a small electrolytic capacitor, say 10 to 47 uF or so,
    across the NES joystick's power and ground pins. You'll still be
    drawing a little too much current from the parallel port, but the
    capacitor may help to smooth out the power glitches that may be
    confusing your controller.

    I hope this helps!

    Matt Roberds

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