A light organ using a WS2812B LED strip on a Raspberry Pi
The light organ is able to react to all sounds played as the user pi. If the Raspberry Pi is set up as a Spotify playback device or a Bluetooth speaker (as explained below), you can easily control the music remotely.
- A Raspberry Pi with Raspbian 10 (buster)
- A WS2812B LED strip or similar
- Clone the repo and install the python libraries in
requirements.txt - Correctly set up the WS2812B LED strip
- Play some music as the user pi
- Enjoy your light organ by executing the correct command
This project uses Poetry for dependency management, so it needs to be installed first, by following the steps at https://python-poetry.org/docs/#installation.
Executing poetry in the shell should show information on its usage.
Afterwards, clone the repository, set up a python virtual environment and install all the necessary packages with the following commands:
git clone https://github.com/BurningKarl/LightOrgan.git
cd LightOrgan
sudo apt install libatlas-base-dev
poetry shell
poetry installThe poetry shell command creates and activates a virtual environment in which we will install the required Python libraries.
The environment can be deactivated by exit and reactivated by executing poetry shell inside the LightOrgan folder.
This repository comes with a self-compiled wheel for llvmlite, as it is currently not available at https://piwheels.org/ but needed for audio analysis with librosa.
For reference, the guide to building llvmlite manually can be found at https://llvmlite.readthedocs.io/en/latest/admin-guide/install.html#building-manually.
I used https://github.com/jgarff/rpi_ws281x/blob/master/README.md to help me to set up my WS2812B LED strip. I decided to use the PCM method on GPIO 21 (pin 40), because
When using PCM you cannot use digital audio devices which use I2S since I2S uses the PCM hardware, but you can use analog audio.
and analog audio is enough for my purposes. This also has the advantage that it is very easy to set up:
- Connect the ground of the LED strip to ground of the Raspberry Pi (e.g. pin 6)
- Connect the 5V of the LED strip to 5V of the Raspberry Pi (e.g. pin 4)
- Connect the data line of the LED strip to pin 40
A useful map of all the pins on the Raspberry Pi can be found at https://pinout.xyz/#.
Once you connected all the wires, the LEDs will not automatically turn on.
You can test everything with sudo .venv/bin/python scripts/strandtest.py -c and the first six LEDs will start to light up in various colors and patterns.
The reason I have set LED_COUNT = 9 is that there is a limit to the number LEDs that you can use simultaneously with the Raspberry Pi as the only power source.
A single LED can use up to 60 mA of current, and it depends on the type of Raspberry Pi what currents it allows.
According to this sheet my Raspberry Pi 3B
has a recommended capacity for the power supply unit of 2.5A which I assume to be close to the current the default power supply unit will provide.
Using all 150 LEDs (5 m * 30 LEDs/m) at the same time leads to a maximum of 9A which is definitely above 2.5A.
You can obviously bypass these problems with an external power supply for the LED strip but if you don't decide to use one, be aware!
Check your audio setup by playing some music as the user pi.
Execute cvlc --play-and-exit example.mp3 using any audio file, and it should be played back via HDMI or connected headphones.
To make sure the audio can be recorded by the light organ script, run arecord -d 10 -f cd test.wav while the music is playing (you may use screen to execute both commands at the same time) to record 10 seconds of CD quality sound and play it back via aplay test.wav.
This should play back the recorded audio. If there is only silence, you need to do some troubleshooting.
To use the light organ, run
python run.pyIt starts capturing audio and visualizing it depending on the selected visualizer in visualize.py.
Without any changes 9 LEDs with rainbow colors will light up depending on the frequency decomposition of the currently playing audio.
LEDs closer to the start of the strip correspond to lower frequencies and those farther away correspond to higher frequencies (250 - 4000 Hz).
Some simple options such as the number of LEDs and the frequency of updates are exposed as command-line options (see python run.py --help).
Everything else can be changed by adapting the visualize.py script.
It is often more convenient to control the music through an external device. The following list contains guides to approaches I've tried so far.
Using Raspotify one can let the Raspberry Pi act as a Spotify playback device (only available for Spotify Premium users). First, set up Raspotify as explained in its README including the "Play via Bluetooth Speaker" section. Essentially, the "Play via Bluetooth Speaker" explains how to set up the systemd service as a user service such that the sound is played back as the user pi. This is essential here, because the python script can only pick up those sounds.
After a successful setup, the Spotify device "raspotify (...)" should appear.
To test whether the sound output of the Spotify Device can be captured by ALSA use arecord and aplay as explained above.
If you have a spare Bluetooth dongle, you can turn your Raspberry Pi into a Bluetooth speaker. I roughly followed the guide at https://github.com/jobpassion/raspberryPi/blob/master/BluetoothSpeaker.md but found that many steps were unnecessary, at least using the full installation of Raspbian.
First use sudo nano /etc/bluetooth/main.conf to edit the Bluetooth configuration.
Here, we need to uncomment the line #Class = 0x000100 and change it to Class = 0x00041C.
This is necessary so that the Raspberry Pi advertises itself as a device that can play audio.
Afterwards we need sudo systemctl restart bluetooth.service so that these changes are applied.
Because the PulseAudio settings are very sensible and already include the module-bluetooth-discover and module-bluetooth-policy modules, we only need to connect the external device (e.g. a smartphone) to the Raspberry Pi.
Execute bluetoothctl to gain access to the Bluetooth console.
Use power on and discoverable on to make the Raspberry Pi discoverable and connect to it using your other device.
While the pairing should work without issues the connection will be dropped shortly after.
This is because the Raspberry Pi does not yet trust the other device.
During the pairing process a line of the form
[NEW] Device <MAC address> <device name>
should come up on the bluetoothctl console.
You now have the MAC address of your device and can confirm using info <MAC> (where <MAC> is the MAC address) that this device is already paired but neither trusted nor connected.
Copy the MAC address and execute trust <MAC> followed by connect <MAC> to trust your device and connect to it.
Now your second device will redirect all audio to the Raspberry Pi where the light organ script can pick it up.
It is often useful to keep the program running in the background and take back control of the command-line.
To make this easier, I packaged it into a systemd user service.
cp lightorgan.service ~/.config/systemd/user/
systemctl --user daemon-reload
systemctl --user edit --full lightorgan.serviceThis will make the service file available to systemd and then open the file in an editor.
Make sure to change PROJECT_ROOT to the current folder (i.e. where run.py can be found), save your changes and close the editor.
Now, you can control the light organ with the following commands:
systemctl --user start lightorgan.service # Start the light organ
systemctl --user stop lightorgan.service # Stop the light organ
systemctl --user restart lightorgan.service # Restart the light organ
systemctl --user status lightorgan.service # Check if the light organ is runningIf you run into the error
libf77blas.so.3: cannot open shared object file: No such file or directory
when importing NumPy (or executing a script which uses NumPy), please refer to the explanations at https://numpy.org/devdocs/user/troubleshooting-importerror.html#raspberry-pi.
I used sudo apt install libatlas-base-dev to solve the issue.