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On the RPi 3 I would like to control a WS2811 LED strip with PWM (GPIO18) by keeping the audio working.

It looks like for the RPi Zero (I'm unsure for RPI 3 though) left and right channels of the built-in 3.5mm jack are hooked up to GPIO13 and GPIO18.

Is it possible to downmix audio to 1 channel so that we can use the audio jack in mono mode and keep GPIO18 free for the LED strip?

I've been trying the .asoundrc configuration below without success. It actually redirects L+R to L very well, but still conflicts with the LED strip:

pcm.monocard {
  slave.pcm card0
  slave.channels 2
  type route
  ttable {
    0.0 1
    1.0 1
    0.1 0
    1.1 0
  }
}
  • That configuration just outputs zero-valued samples on the right channel. I guess you have to reconfigure the GPIO pin itself. – CL. Nov 28 '16 at 7:52
  • @CL. Is this tuto the right way to do this? What is the goal in the end, disabling GPIO 18 as audio, forcing PWM on GPIO 18, ...? – myoan Nov 28 '16 at 23:04

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