Using an LED Ring with Raveberry

• raveberry

  20 701 6.0 Python

  A multi-user music server with a focus on participation

Raveberry is a project that makes parties more fun by allowing everybody to influence the music. With an LED ring in the transparent case of the Raspberry Pi, I tried to make it visually interesting as well. I want to share with you how the ring is connected and controlled, how I made the lights react to the music and how I modified the colors to make them a little more appealing.

• Mopidy

  62 7,921 9.3 Python

  Mopidy is an extensible music server written in Python

  

In the first video, you can see how the LEDs light up to the beat of the music in realtime. In order to produce this effect, multiple steps are necessary. First, mopidy (the music player) duplicates the audio output into a fake pulseaudio sink. cava then captures the audio from this sink and transforms it, splitting it into its frequencies. Raveberry maps these frequencies to colors from red to blue and lights up the LED ring accordingly. Since the transformation takes a short amount of time, the audio output is delayed by approximately that time to sync the light flashes with the beat. All in all, this allows for a pretty neat sound-reactive spectrum visualization on the LED ring.

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• rpi_ws281x

  15 1,740 2.5 C

  Userspace Raspberry Pi PWM library for WS281X LEDs

The LEDs are controlled via the SPI interface of the Raspberry Pi. The rpi_ws281x library is used to manage the ring from python code. The library also provides the possibility to control LEDs via PWM or PCM, however this either disables either analog or digital audio output, which is quite disadvantageous for a music server. On a Raspberry Pi 4, there is one thing to look out for: SPI requires a stable clock, and the Pi 4 throttles itself by default. This can be avoided by adding core_freq_min=500 to /boot/config.txt. Raveberry takes care of this during install if you enable LED visualization.

• cava

  37 3,773 7.8 C

  Cross-platform Audio Visualizer

In the first video, you can see how the LEDs light up to the beat of the music in realtime. In order to produce this effect, multiple steps are necessary. First, mopidy (the music player) duplicates the audio output into a fake pulseaudio sink. cava then captures the audio from this sink and transforms it, splitting it into its frequencies. Raveberry maps these frequencies to colors from red to blue and lights up the LED ring accordingly. Since the transformation takes a short amount of time, the audio output is delayed by approximately that time to sync the light flashes with the beat. All in all, this allows for a pretty neat sound-reactive spectrum visualization on the LED ring.

• audio-reactive-led-strip

  7 2,636 0.0 Python

  :musical_note: :rainbow: Real-time LED strip music visualization using Python and the ESP8266 or Raspberry Pi

LedFX sounds great if you want to control many different strips in a network. For a standalone Raspberry Pi, there is also this project, which I meant to try out for some time but did not come around to. It has a lot more features than my implementation.

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