Official NixOS Wiki

NixOS on ARM/Raspberry Pi 4: Difference between revisions

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update state version to 24.11
m add udev rule for non-root access through libgpiod
 
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   system.stateVersion = "24.11";
   system.stateVersion = "24.11";
}
}
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=== <code>config.txt</code> ===
{{warning|Since 24.11, the option <code>boot.loader.raspberrypi</code> which included <code>firmwareConfig</code> is removed from <code>nixpkgs</code>, therefore changes have to be written to <code>config.txt</code> directly<ref>https://github.com/NixOS/nixpkgs/pull/241534</ref>}}
To edit options only available through <code>config.txt</code>, as of May 12, 2025, you can only do so non-declaratively:
{{commands|<nowiki>
$ sudo mount /dev/disk/by-label/FIRMWARE /mnt
$ sudo vim /mnt/config.txt # <-- make changes here
</nowiki>}}
For example, [https://www.raspberrypi-spy.co.uk/2020/11/overclocking-the-raspberry-pi-400/ overclocking] the Raspberry Pi 400 can be done by adding the following:
{{file|config.txt|text|<nowiki>
arm_freq=2000
over_voltage=6
</nowiki>}}
</nowiki>}}


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   # Enable audio devices
   # Enable audio devices
   boot.kernelParams = [ "snd_bcm2835.enable_hdmi=1" "snd_bcm2835.enable_headphones=1" ];
   boot.kernelParams = [ "snd_bcm2835.enable_hdmi=1" "snd_bcm2835.enable_headphones=1" ];
  boot.loader.raspberryPi.firmwareConfig = ''
    dtparam=audio=on
  '';
}
}
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{{file|config.txt|txt|<nowiki>
dtparam=audio=on
</nowiki>}}
</nowiki>}}


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The <code>extraRules</code> changes the owner of <code>gpiomem</code> and all other files needed for GPIO to work to <code>root:gpio</code> and changes the permissions to <code>0660</code>.
The <code>extraRules</code> changes the owner of <code>gpiomem</code> and all other files needed for GPIO to work to <code>root:gpio</code> and changes the permissions to <code>0660</code>.
Therefore, the root user and anyone in the gpio group can now access the GPIO pins.
Therefore, the root user and anyone in the gpio group can now access the GPIO pins.
Permissions on the <code>/dev/gpiochip*</code> devices are needed to support access through the newer '''GPIO character device''' interface (see [https://libgpiod.readthedocs.io/en/latest/ libgpiod]).


<syntaxHighlight lang="nix">
<syntaxHighlight lang="nix">
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     SUBSYSTEM=="gpio", KERNEL=="gpiochip*", ACTION=="add", RUN+="${pkgs.bash}/bin/bash -c 'chown root:gpio /sys/class/gpio/export /sys/class/gpio/unexport ; chmod 220 /sys/class/gpio/export /sys/class/gpio/unexport'"
     SUBSYSTEM=="gpio", KERNEL=="gpiochip*", ACTION=="add", RUN+="${pkgs.bash}/bin/bash -c 'chown root:gpio /sys/class/gpio/export /sys/class/gpio/unexport ; chmod 220 /sys/class/gpio/export /sys/class/gpio/unexport'"
     SUBSYSTEM=="gpio", KERNEL=="gpio*", ACTION=="add",RUN+="${pkgs.bash}/bin/bash -c 'chown root:gpio /sys%p/active_low /sys%p/direction /sys%p/edge /sys%p/value ; chmod 660 /sys%p/active_low /sys%p/direction /sys%p/edge /sys%p/value'"
     SUBSYSTEM=="gpio", KERNEL=="gpio*", ACTION=="add",RUN+="${pkgs.bash}/bin/bash -c 'chown root:gpio /sys%p/active_low /sys%p/direction /sys%p/edge /sys%p/value ; chmod 660 /sys%p/active_low /sys%p/direction /sys%p/edge /sys%p/value'"
    SUBSYSTEM=="gpio", KERNEL=="gpiochip*", ACTION=="add", RUN+="${pkgs.bash}/bin/bash -c 'chown root:gpio /dev/gpiochip* && chmod 0660 /dev/gpiochip*'"
   '';
   '';


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</syntaxhighlight>
</syntaxhighlight>


The the <code>spi0-0cd.dtso</code> file can be downloaded [https://github.com/raspberrypi/firmware/blob/master/boot/overlays/spi0-0cs.dtbo here].
The the <code>spi0-0cs.dtso</code> file can be downloaded [https://github.com/raspberrypi/firmware/blob/master/boot/overlays/spi0-0cs.dtbo here].
You might have to change the <code>compatible</code> field to "raspberrypi" in the dtbo file.
You might have to change the <code>compatible</code> field to "raspberrypi" in the dtbo file.


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   };  
   };  
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== Customizing & Generating SD image without installation step ==
There's a nix-community project to support fine-grained kernel & config.txt, and generate the image directly:
[https://github.com/nix-community/raspberry-pi-nix/ nix-community/raspberry-pi-nix]


== Notes about the boot process ==
== Notes about the boot process ==
Retrieved from "https://wiki.nixos.org/wiki/NixOS_on_ARM/Raspberry_Pi_4"