First post here, a few months after having started with NixOS (this is an indirect compliment to the documentation and the community content - searching through it was enough up to today ).
I have installed and deployed NixOS on my RPI4, and I have the official RPI fan that is plugged on the GPIO pins. I’d like to control the fan speed based on the temperature of the CPU - the same way you can configure it in raspi-config in RaspiOS.
Is there something already packaged that I wouldn’t have found to do it already? And if not, how would you suggest I set this up?
I ended up with a working yet not super elegant solution
Here is the relevant part of my configuration file:
environment.systemPackages = with pkgs; [
haskellPackages.gpio
libraspberrypi
];
# service to control the fan
systemd.services.fan-control = {
description = "Control the fan depending on the temperature";
script = ''
/run/current-system/sw/bin/gpio init 18 out
temperature=$(/run/current-system/sw/bin/vcgencmd measure_temp | grep -oE '[0-9]+([.][0-9]+)?')
threshold=65
if /run/current-system/sw/bin/awk -v temp="$temperature" -v threshold="$threshold" 'BEGIN { exit !(temp > threshold) }'; then
/run/current-system/sw/bin/gpio write 18 hi
else
/run/current-system/sw/bin/gpio write 18 lo
fi
/run/current-system/sw/bin/gpio close 18 out
'';
};
systemd.timers.fan-control-timer = {
description = "Run control fan script regularly";
timerConfig = {
OnCalendar = "*-*-* *:0/1:00"; # Run every 10 minutes
Persistent = true;
Unit = "fan-control.service";
};
wantedBy = [ "timers.target" ];
};
).
