Add post Raspberry Pi camera on NixOS

content/2023-07-31-Raspberry-Pi-Camera-NixOS.markdown

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+---
+title: Raspberry Pi camera on NixOS
+---
+
+In this article I describe how I configured my Raspberry Pi V1 camera module
+working on my Raspberry Pi 3 running NixOS.
+
+The Raspberry Pi OS has [excellent support][RPi-Camera-Configuraiton] for many
+camera modules.  If you run the officialy supported operating system most
+cameras work without any further configuration.
+
+In my Homelab I don't use the Raspberry Pi OS, but I run NixOS on my Raspberry
+Pis.  This works reasonably well, but the camera module I own needs special
+configuration.
+
+# The "modern" camera stack
+
+In 2020 the Raspbery Pi team [released a new camera
+stack][libcameraAnnouncement] which provides better access to the internals of
+the camera system.  Today the legacy system, based on Broadcom proprietary
+software, is unsupported and obsolete.  Unfortunately, many online instructions
+and tutorials [still refer to the Broadcom stack][CameraNotDetected] which
+renders them irrelevant to the modern camera stack.
+
+The new camera stack is built out the following components:
+
+1. Linux kernel using board specific configurations
+1. Camera module specific drivers (in my case Omnivision OV5647 for my version 1 module)
+1. libcamera library built from Raspberry Pi
+1. rpicam-apps camera utilities from the Rapberry Pi foundation
+
+The next sections describe how I put these together on NixOS.
+
+## Kernel 
+
+The Nix Packages collections have a few variants of the Linux kernel.  The
+default one works on most hardware without any problems.  For my Raspberry Pi 3
+I select the `linux_rp3` kernel package, which is built from the Raspberry Pi
+foundation's fork.
+
+```
+{ pkgs, ...}:
+{
+  boot.kernelPackages = pkgs.linuxKernel.packages.linux_rpi3;
+}
+```
+
+## Camera driver (OV5647)
+
+```
+{ pkgs, ...}:
+{
+
+  boot.kernelPackages = pkgs.linuxKernel.packages.linux_rpi3;
+
+  https://wiki.nixos.org/wiki/NixOS_on_ARM/Raspberry_Pi#Camera
+
+  hardware.deviceTree.filter = "bcm2837-rpi-3*";
+  hardware.deviceTree.overlays = [
+    name = "ov5647-overlay";
+    dtsText = '''
+    ''';
+  ]
+}
+```
+
+## libcamera
+
+## rpi-apps
+
+
+[libcameraAnnouncement]: https://www.raspberrypi.com/news/an-open-source-camera-stack-for-raspberry-pi-using-libcamera/
+[CameraNotDetected]: https://forums.raspberrypi.com/viewtopic.php?t=362707
+[RPi-Camera-Configuration]: https://www.raspberrypi.com/documentation/computers/camera_software.html#configuration
+[NixWikiCamera]: https://wiki.nixos.org/wiki/NixOS_on_ARM/Raspberry_Pi#Camera