Controlling a Raspberry Pi over IR

I have a digital photo frame running on a Raspberry Pi hooked up to a small TV, and want an easy way to control playback. I already need a remote for the TV, so why not use that? Below I’ll go through the setup process I used to turn IR commands into key presses on a Pi running Bookworm, including an Ansible playbook for automating setup.

Manual Setup

The Hardware

The first thing we need is an IR receiver to physically sense the infrared signals broadcast by the remote. I scavenged one from a broken DVD player, but if you had to buy one, they’re pretty cheap.

Next, I wired that up to 5V and a GPIO pin from the Pi header, and we’re all set to move to software land.

Configuration

I set up a Raspberry Pi running the full Pi OS and installed a couple necessary packages. LIRC parses IR commands from the receiver and exposes them to user space, while xdotool¹ simulates key presses, which is how I’ll be controlling the browser-based slideshow.

sudo apt install lirc xdotool

Adding the following line² to the boot configuration at /boot/firmware/config.txt enables kernel support for the IR receiver on the connected GPIO pin:

dtoverlay=gpio-ir.gpio_pin=18

Remote IR codes vary between manufacturers and models, so LIRC needs a configuration file to know which codes correspond to which buttons for a given remote. I found a close match to my remote in the LIRC database and moved it to /etc/lirc/lircd.conf.d, where LIRC can automatically find it.

After a reboot, running irw and pressing some buttons while pointed at the receiver should result in correctly parsed commands:

$ irw

Next, we need a config file for irexec. This is where the magic of turning parsed commands into key presses happens, and it’s as simple as registering input commands like KEY_LEFT to output commands like xdotool key Left.

begin
    prog   = irexec
    button = KEY_LEFT
    config = xdotool key Left
end

The last step is to start running irexec in the background on startup, which I did by putting the following line in /etc/xdg/lxsession/LXDE-pi/autostart:

@irexec

With that, we’ve got IR command of the keyboard. For my setup, the left and right arrows navigate backward and forward, the up arrow brings up file metadata, and the play and pause buttons toggle playback.

Automating with Ansible

To avoid having to manually run that configuration again in the future, I automated the setup with Ansible.

Here’s my inventory that defines the target and some basic configuration:

---
clients:
  hosts:
    pi:
      ansible_host: 192.168.0.0
      ansible_user: pi
      remote_file: AKB74475403.lircd.conf
      gpio:
        ir: 18

And the playbook that duplicates the manual configuration steps from above:

---
- name: Setup Raspberry Pi for IR Remote Control
  hosts: clients
  gather_facts: false
  tasks:
    - name: Install packages
      become: true
      ansible.builtin.apt:
        update_cache: true
        pkg:
          - lirc
          - xdotool

    - name: Enable GPIO in boot config
      become: true
      ansible.builtin.lineinfile:
        path: /boot/firmware/config.txt
        line: dtoverlay=gpio-ir.gpio_pin={{ gpio.ir }}

    - name: Copy remote file
      become: true
      ansible.builtin.copy:
        src: {{ remote_file }}
        dest: /etc/lirc/lircd.conf.d
        owner: root
        group: root
        mode: "0644"

    - name: Configure irexec
      ansible.builtin.copy:
        src: lircrc
        dest: /home/{{ ansible_user }}/.config/lircrc
        owner: "{{ ansible_user }}"
        group: "{{ ansible_user }}"
        mode: "0644"

    - name: Autostart irexec
      become: true
      ansible.builtin.lineinfile:
        path: /etc/xdg/lxsession/LXDE-pi/autostart
        line: "@irexec"

    - name: Reboot to apply config
      become: true
      ansible.builtin.reboot: