periph.io based cli for driving gpio pwm

Enable the desired pwm overlay in, for example:

dtoverlay=pwm-2chan,pin=12,func=4,pin2=13,func2=4

Make sure that audio is enabled:

dtparam=audio=on

$ echo "0.5" | rpi-pwm set -num 1

Values between 0 and 1 can be provided on standard input.

The bcm283x gpio driver uses /dev/gpiomem for gpio access, but also needs DMA for PWM. This means docker containers need to be run in privileged mode (with --privileged):

$ docker run --privileged --device /dev/gpiomem ...

This CLI uses a forked version of periph.io/host that supports PWM through sysfs when DMA isn't available (when running without --privileged).

It also uses files in /sys/firmware (to map gpio pin numbers to pwm numbers), which docker doesn't export by default, so additional security-opts are needed to export them. Alternatively, these files can be manually copied into the container.

$ docker run --user nobody:gpio --device /dev/gpiomem -v /sys:/sys \
  --security-opt systempaths=unconfined --security-opt apparmor=unconfined ...