Controller daemon for managing a ws2812b connected to a raspberry pi 3 b
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animations
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readme.md

RGBD

Version 1.0.0!

I'm writing a daemon for controlling my ws2812B RGB LED strips with my raspberry pi. Security is something of a concern, so this is written so as to never actually require root.

The main purpose behind most of this is so that I can easily dim the brightness on the lights (or change the lighting patterns/mood) from my phone, in my bed. Really.

Uses rpi_ws281x and colour.

You must be controlling your pi over SPI for this, so it can run as a non-root user. Specifically, you'll probably need to modify your /boot/config.txt and /boot/cmdline.txt as outlined in rpi_ws281x's readme.

DBUS is used for passing messages from the ctl script to the daemon. If you don't have a dbus session bus (i.e. from an X session), I've included some systemd unit files.

Wiring

My wiring setup is as follows:

  • Single pin connector from SPI 0 (GPIO 10) to DIN on the LED Strip
  • Raspi ground to ground on the LED Strip
  • Positive from a power supply to the 5V power line on the strip
  • Ground back into the negative on the power supply.

A 3.3V -> 5V voltage step is not required for the WS2812B, since (most) 2812B strips take 3.3-5V DIN, since DIN and power have been decoupled and no longer need to be run at the same voltage.

Setup

Install rpi_ws281x and colour (not strictly needed, but handy for animations). Make sure to follow the instructions for SPI as given in the rpi_ws281x repo.

rpi_ws281x must be from at least this commit or newer, so that rootless SPI works.

Installing

git clone https://github.com/pandorasfox/rgbd && cd rgbd
chmod +x ./installer
./installer install all

You can specify a variety of options to the installer for where files get installed to.

To use lightctl, make sure its install dir is in your $PATH. By default, it installs to ~/.local/bin.

You must be a member of the gpio group in order to run this code.

Usage

After installing the files, you should be able to just systemctl --user enable --now rgbd. You may need to tweak your config file.

See the included animation scripts for examples on how to create animations.

This project and root/sudo

A big part of why I wrote this daemon is so that animations can be dynamically loaded, and for good dynamic control of my lights. If something is going to be dynamically loading and executing script files, it should not be doing that as root.

This left me with a few options:

  • Run the animation scripts in a separate downgraded process, with limited shared resources. Pretty workable, but difficult to rig up animation timings.
  • Disallow dynamic config loading (boo).
  • Set up a root daemon we can control (less performant/communication is hard)
  • Run everything as our own user.

The last option was the best, but required a decent amount of setup to get right.

If you want the script to persist beyond your session, then you will need sudo rights to set some loginctl stuff, but that's it. For all regular usage, it can just stay running as a user daemon without any need for elevated permissions, ever.