View source for NixOS on ARM/Raspberry Pi

{{ARM/breadcrumb}}
<div class="infobox">
{|class="table"
!colspan="2" class="title"|Raspberry Pi Family
|-
|colspan="2"|[[File:raspberry_pi_3_glamour.jpg|frameless|256px|A Raspberry Pi 3 with enclosure.]]
|-
!colspan="2" class="title"|Raspberry Pi
|-
!Architecture
|ARMv6
|-
!colspan="2" class="title"|Raspberry Pi 2
|-
!Architecture
|ARMv7
|-
!colspan="2" class="title"|Raspberry Pi 3
|-
!Architecture
|AArch64 + ARMv7
|}
</div>
The Raspberry Pi family of devices is a series of single-board computers made by the Raspberry Pi Foundation. They are all based on Broadcom System-on-a-chip (SOCs). 

== Status ==

Only the ''Raspberry Pi 3 Family'' is supported upstream, with the AArch64 effort. Other Raspberry Pis are part of '''@dezgeg''''s porting efforts to ARMv6 and ARMv7.

The Linux kernel in use, except for the Raspberry Pi 1 family, is the mainline Linux kernel, and not the Raspberry Pi Foundation's fork. This could reduce compatibility with some add-on boards or third-party libraries<sup>[expanded explanation needed]</sup>.

The following table is intended to be updated by the NixOS contributors with the current status of the boards. For a list of products, [https://www.raspberrypi.org/products/ see the ''Products Archive]''.

{|class="wikitable"
|-
! Board name
! Architecture
! Support
|-
!colspan="3" style="text-align: left;"|Raspberry Pi 1
|-
| Raspberry Pi 1 Model A+
|rowspan="4" style="vertical-align: middle;"| armv6
| C*
|-
| Raspberry Pi 1 Model B+
| C
|-
| Raspberry Pi Zero
| C*
|-
| Raspberry Pi Zero W
| C*
|-
!colspan="3" style="text-align: left;"|Raspberry Pi 2
|-
| Raspberry Pi 2 Model B
| armv7
| C*
|-
!colspan="3" style="text-align: left;"|Raspberry Pi 3
|-
| Raspberry Pi 3 Model B
|rowspan="3" style="vertical-align: middle;"| AArch64<br /> ''+ armv7''
| YES
|-
| Raspberry Pi 3 Model B+
| YES
|-
| Raspberry Pi 3 Model A+
| ?
|}

''Support''
* YES: Supported architecture by Nixpkgs downstream and tested to be working.
* C: Community supported, and tested to be working.
* C*: Community supported, unverified but should be working.
* ? : Unverified, unknown if it will work.

The Raspberry Pi 3 Family is only supported as '''AArch64'''. Use as armv7 is community supported.

== Board-specific installation notes ==

First follow the [[NixOS_on_ARM#Installation|generic installation steps]] to get the installer image and install using the [[NixOS_on_ARM#NixOS_installation_.26_configuration|installation and configuration steps]].

=== Raspberry Pi (1) ===

The ARMv6 image boots out-of-the-box.

=== Raspberry Pi 2 ===

The ARMv7 image should boot out-of-the-box, though the author hasn't personally tested this.

=== Raspberry Pi 3 ===

Both the AArch64 and ARMv7 images boot out-of-the-box. Using the 64-bit AArch64 image is highly recommended, as the availability of binaries is much better and allows the use of the 64-bit instruction set.

For the UART console, edit <code>/extlinux/extlinux.conf</code> on the boot partition of the SD card to set <code>console=ttyS1,115200n8</code> in the kernel boot parameters, and use the following GPIO Pins with an USB-TTL connector: 
<syntaxhighlight>
GND         - 3rd in top row, black cable
GPIO 14 TXD - 4th in top row, white cable
GPIO 15 RXD - 5th in top row, green cable
</syntaxhighlight>
Use <code>nix-shell -p screen --run "screen /dev/ttyUSB0 115200"</code> to connect to the console. 
{{note|The mainline kernel (tested with nixos kernel 4.18.7) [https://github.com/raspberrypi/linux/wiki/Upstreaming#downstream-drivers does not include support for cpu frequency scaling] on the Raspberry Pi. To get higher clock speed, set [https://www.raspberrypi.org/documentation/configuration/config-txt/overclocking.md <code><nowiki>force_turbo=1</nowiki></code>] in <code>/boot/config.txt</code> }}
{{note|As of today (2018-01-13) the stable channel contains fixes for wifi for both the stable and the latest linux kernel. Check out {{pull|53747}} }}
<syntaxhighlight lang=nix>
{
  ...
  hardware.enableRedistributableFirmware = true;
  networking.wireless.enable = true;
}
</syntaxhighlight>

=== Raspberry Pi 3B+ ===

Here is a similar incantation as above, but for the Raspberry Pi 3B+:

<syntaxhighlight lang=nix>
{
  ...
  hardware.enableRedistributableFirmware = true;
  hardware.firmware = [
    (pkgs.stdenv.mkDerivation {
     name = "broadcom-rpi3bplus-extra";
     src = pkgs.fetchurl {
     url = "https://raw.githubusercontent.com/RPi-Distro/firmware-nonfree/b518de4/brcm/brcmfmac43455-sdio.txt";
     sha256 = "0r4bvwkm3fx60bbpwd83zbjganjnffiq1jkaj0h20bwdj9ysawg9";
     };
     phases = [ "installPhase" ];
     installPhase = ''
     mkdir -p $out/lib/firmware/brcm
     cp $src $out/lib/firmware/brcm/brcmfmac43455-sdio.txt
     '';
     })
  ];
  networking.wireless.enable = true;
}
</syntaxhighlight>

== Serial console==

Your <code>configuration.nix</code> will need to add <code>console=ttyS1,115200n8</code> to the <code>boot.kernelParams</code> configuration to use the serial console.

{{file|/etc/nixos/configuration.nix|nix|<nowiki>
{ config, pkgs, lib, ... }:
{
  boot.kernelParams = [
    "console=ttyS1,115200n8"
  ];
}
</nowiki>}}
== Camera ==

For the camera to work, you will need to add the following code to your configuration.nix: 

{{note| Two pull requests ({{pull|38490}} and {{pull|38342}}) are required to make this configuration.nix and the camera working.}}
{{file|/etc/nixos/configuration.nix|nix|<nowiki>
{ config, pkgs, lib, ... }:
{
  boot.loader.raspberryPi.enable = true;
  # Set the version depending on your raspberry pi. 
  boot.loader.raspberryPi.version = 3;
  # We need uboot
  boot.loader.raspberryPi.uboot.enable = true;
  # These two parameters are the important ones to get the
  # camera working. These will be appended to /boot/configuration.txt.
  boot.loader.raspberryPi.firmwareConfig = ''
    start_x=1
    gpu_mem=256
  '';
}
</nowiki>}}
{{note| A reboot is required to load the new firmware configuration.}}

To make the camera available as v4l device under <code>/dev/video0</code> the <code>bcm2835-v4l2</code> kernel module need to be loaded. This can be done by adding the following code to your configuration.nix: 

{{file|/etc/nixos/configuration.nix|nix|<nowiki>
{ config, pkgs, lib, ... }:
{
  boot.kernelModules = [ "bcm2835-v4l2" ];
}
</nowiki>}}
== Binary Cache ==

Depending on the architecture used, binary caches availability varies. Binary caches instructions are on the main [[NixOS on ARM#Binary cache|NixOS on ARM]] page. The following table describes the architectures supported by each board. 

{|class="wikitable"
|-
! Raspberry Pi 1
| armv6
|-
! Raspberry Pi 2
| armv7
|-
!rowspan="2" style="vertical-align: middle;"|Raspberry Pi 3
| armv7
|-
| AArch64
|}

== Notes about the boot process ==

It takes approximately 1 minute to boot a Pi 3B.

=== Raspberry Pi (all versions) ===

USB keyboards and HDMI displays should work, though some issues have been reported (see Troubleshooting below).

Using the 3.3v serial port via the pin headers (exact location depends on hardware version) will get u-boot output and, when configured, a Linux kernel console.

== Troubleshooting ==

=== Power issues ===

Especially with the power-hungry Raspberry Pi 3, it is important to have a [https://www.raspberrypi.org/documentation/hardware/raspberrypi/power/README.md sufficient enough power supply] or ''weirdness'' may happen. Weirdness may include:

* Lightning bolt on HDMI output "breaking" the display.
* Screen switching back to u-boot text
** Fixable temporarily when power is sufficient by switching VT (alt+F2 / alt+F1)
* Random hangs

This problem is a hard problem. It is caused by the Raspberry Pi warning about power issues, but the current drivers (as of 
Linux 4.14) have a hard time dealing with it properly. If the power supply is rated properly AND the cable is not incurring too much power losses, it may be required to disable the lightning bolt indicator so the display driver isn't messed up.<ref>https://logs.nix.samueldr.com/nixos/2017-12-20#1513784657-1513784714;</ref> The lightning bolt indicator can be disabled by adding the line <code>avoid_warnings=1</code> in config.txt<ref>https://www.raspberrypi.org/documentation/configuration/config-txt/README.md</ref>

{{note|A ''properly rated'' USB power supply, AND a good cable are necessary. The cable has to be short enough to not incur power losses through the length. Do note that thin and cheap cables usually have thinner copper wires, which in turn accentuates power losses.}}

===HDMI===

HDMI issues have been observed on the 18.09 AArch64 image. The display would hang on "Starting Kernel...", then act as if the HDMI cable was unplugged. Re-plugging the HDMI cable after boot fixed the issue, as did a different monitor and HDMI cable.

==== Early boot messages ====

To show boot messages from initrd with the mainline kernel, add this to <code>configuration.nix</code>.

<syntaxhighlight lang=nix>
{
  boot.initrd.kernelModules = [ "vc4" ];
}
</syntaxhighlight>

===Additional Troubleshooting===

Additional troubleshooting information may be found [https://elinux.org/R-Pi_Troubleshooting at elinux.org].

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