Help with "multiplexing" extra sensors for an Xbox 360 Drum controller

Discussion in 'The Projects Forum' started by Kaboom22, Nov 28, 2009.

  1. Kaboom22

    Thread Starter New Member

    Nov 27, 2009
    Ok, so here is the problem, I am trying to add additional inputs to a rock band 1 drum controller (that I purchased cheaply from my friend, who is thankfully incapable of operating devices without breaking them) so I can use it for DTXMania. It will also have a switch to disable the extra bits so the cymbals just replicate the normal inputs, so it can be used for normal Rock band on the 360, or for Frets on fire X.

    What I have decided is to sacrifice the DPad and use the directions to differentiate between multiple pads on the same input. So Blue + Up = Hi-hat Open, Blue + Down = Low Tom, Blue + Right = Ride Cymbal and a similar thing for other colours. Each colour is carefully chosen so when the directional inputs are disabled, the layout of the pads still make sense in rock band.

    At first, i tried wiring things up like the attached image (apologies for the dodgy ms paint drawing), but the diodes are affecting the signal in weird ways. I read in another thread that i might need a diode reversed across the connections to correct the waveform, but the results are intermittent. Looking at it on my ancient o-scope, the signal is nosier than the normal diminishing sinusoidal ripple that usually occurs from an impact, and sometimes no signal is seen at all. The reversed diode helps, but its still not good enough to be detected reliable by the xbox controller on each impact.

    I can use an opamp based circuit for every single input in place of the diode to buffer the signal without affecting it, but my feeling is there is an easier way, and i'm simply not understanding the basics well enough to see it. Plus, i have limited board space to work with.

    I hope that I've explained the problem clearly enough, i would be happy to answer any questions. This has been driving me nuts.
  2. SgtWookie


    Jul 17, 2007
    Your pads are piezo, right?

    I threw a couple more diodes in the mix:


    I was trying to help someone awhile back that was making some drum pads, but I forgot to add diodes like I did to yours. This prevents a large negative voltage from building up on the upper side of the piezo pad.

    Your other controllers might be interfering with the piezo pads. You might add diodes to them as well, and connect them to the right of the piezo's diodes.
  3. Kaboom22

    Thread Starter New Member

    Nov 27, 2009
    Yes, they are piezos. This is the extra diodes i mentioned earlier that I've already tried, but still no luck.

    The triggering circuits were not connected when I've been testing this, so I don't think its a problem. Its also nothing to do with the xbox controller itself, because i still see the same intermittent problem when its directly connected to the o-scope (with the diodes).

    Thanks though :)