NixOS on ARM/Raspberry Pi 4: Difference between revisions

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   '';
</nowiki>}}
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==== Gpio and 1-wire ====
{{file|/etc/nixos/configuration.nix|nix|<nowiki>
  # add gpio group
  users.groups.gpio = {};
  # udev rule for gpio
  services.udev.extraRules = ''
    SUBSYSTEM=="bcm2835-gpiomem", KERNEL=="gpiomem", GROUP="gpio",MODE="0660"
    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'"
  '';
  # add user with gpio group
  users = {
    mutableUsers = false;
    users.mygpiouser = {
      isNormalUser = true;
      password = "mygpiouserpasswd";
      extraGroups = [ "wheel" "gpio" ];
    };
  };
# insert device tree snippet for 1-wire
  hardware.deviceTree = {
  enable = true;
  overlays = [
      {
        name = "w1-gpio-overlay";
        dtsText = ''
/dts-v1/;
/plugin/;
/ {
compatible = "brcm,bcm2711";
fragment@0 {
target-path = "/";
__overlay__ {
w1: onewire@0 {
compatible = "w1-gpio";
pinctrl-names = "default";
pinctrl-0 = <&w1_pins>;
gpios = <&gpio 4 0>;
rpi,parasitic-power = <0>;
status = "okay";
};
};
};
fragment@1 {
target = <&gpio>;
__overlay__ {
w1_pins: w1_pins {
brcm,pins = <4>;
brcm,function = <0>; // in (initially)
brcm,pull = <0>; // off
};
};
};
__overrides__ {
gpiopin =      <&w1>,"4",
<&w1_pins>,"brcm,pins:0";
pullup =        <&w1>,"rpi,parasitic-power:0";
};
};
        '';
      }
    ];
  };
</nowiki>}}
== Troubleshooting ==
== Troubleshooting ==


Retrieved from "https://wiki.nixos.org/wiki/NixOS_on_ARM/Raspberry_Pi_4"