irberry

NixOS configuration for a Raspberry Pi 3 IR transmitter controllable using MQTT.

Prerequisites

The following instructions are specific to NixOS. It might be possible to build it on other platforms (as long as they have nix installed) but I haven't tried.

You should emulate aarch64 rather than cross-compiling it. Emulation will allow you to use NixOS's binary cache, which is much faster than compiling everything. Add the following options to your system's configuration.nix (and run nixos-rebuild switch afterwards):

boot.binfmt.emulatedSystems = [ "aarch64-linux" ];
nix.settings.extra-platforms = [ "aarch64-linux" "arm-linux" ];

Configuration

Wifi credentials are configured using the following environment variables:

• WIFI_SSID
• WIFI_PSK

The .envrc in this repo configures direnv to read .env. Add a .env file that looks like this:

WIFI_SSID="..."
WIFI_PSK="..."

These credentials will be set as global environment variables in the resulting NixOS installation. The build will fail if they are unset.

Installation

1. Build the sd card image by running

   make

2. Install the image on a SD card

   sudo dd if=./result/sd-image/nixos-sd-image-irberry.img of=/dev/sda bs=4096 conv=fsync

3. Put the SD card into the raspberry pi and start it up!

4. It'll take a minute or two for it to start, but once it's up and running change the password

   # initial password is 'changeme'
   ssh matt@<ip-address>
   passwd

5. The raspberry pi should now be connected to the MQTT broker and sending IR signals when commands are sent to the topic irberry/button!

Updating an existing installation

1. ssh into the raspberry pi

   ssh matt@<ip-address>

2. Update nix channels

   sudo nix-channel --update

3. Run nixos-rebuild switch, but be sure to open a root shell so the environment variables are set properly

   sudo bash
   nixos-rebuild switch