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On a Raspberry Pi 3 with as of today latest firmware and raspbian, I have e.g. espeak "hi" or aplay some.wav working after booting into a small loudspeaker plugged into the jack (this is headless, no X11 desktop; no HDMI monitor connected).

Now as soon as I use GPIO (e.g. https://github.com/pololu/dual-mc33926-motor-driver-rpi/blob/master/example.py to run a Motor), even after that's finished and released anything it has to release (or does it?), then sound won't work anymore (until I reboot); e.g. aplay fails with:

aplay: pcm_write:1939: write error: Input/output error

How are playing sound and GPIO related on the RPi, and what do you have to do you use both together?

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The most likely clash is with GPIO 18/19/20/21 (pins 12/35/38/40).

PWM (medium quality audio) uses GPIO 18/19, PCM (high quality audio) uses GPIO 18/19/20/21.

Check to see what your motor driver is using which clashes and use alternative GPIO.

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  • Aha. Yep, motor indeed uses e.g. RaspiBcmPin GPIO_12 (in Pi4j "BROADCOM_PIN_NUMBERING"), see [1] Motors driver class source. Using alternative GPIO on that [2] Motor shield appears to require to cut traces on the board and re-soldering... :-( There is no (easier) way to make PWM or PCM use another GPIO instead, is there? [1] github.com/vorburger/dual-mc33926-motor-driver-pi4j/blob/… [2] pololu.com/product/2755
    – vorburger
    Aug 21 '16 at 15:14
  • @vorburger I don't think you can alter the GPIO used for audio. But I do not use audio at all on the Pi so I may be wrong.
    – joan
    Aug 21 '16 at 15:54

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