This is a self indulgent project by Ben XO https://github.com/ben-xo

The idea is that you feed line level audio into a pin on an arduino, and you get pretty lights out on a strip of Neopixels (WS2812 or compatible).

Copyright Ben XO https://github.com/ben-xo All rights reserved.

THIS PROJECT IS NOT OPEN SOURCE. Whilst I have put the source code on GitHub, no part of this project is currently released under any open source license.

I reserve all rights and the right to change this license in future.

Kinda like this https://www.instagram.com/p/Bt-8dVqlZSi/ or this https://www.instagram.com/p/Bt-8dVqlZSi/

• Works from line-in
• Interrupt driven audio sampling - even with WS2812s (requires a slightly modified FastLED library at https://github.com/ben-xo/FastLED)
• A solid 180 frame per second with 60 WS2812s (or 125fps with 100 WS2812s) with no slow frames or dropped samples
• Beat detection and tempo estimation in realtime. Yep! All on a single Arduino
• 8 cool sound-reactive visualisers. These have been endlessly tinkered with so that they look okay at a range of input volumes and aren't TOO jarring when they change
• Automatic mode changing after a certain number of beats
• Effects work well for a range of music from house and techno to drum & bass
• Visualisers cope with things like DC Offset on the line-in
• push button to change modes
• Status LEDs driven using interrupt driven PWM (so no need for resistors on the status LEDs)
• Screensaver when the audio goes quiet. Because why not!
• Nice rainbow when you turn it on

First of all this should go without saying but LEAVE THE POWER DISCONNECTED until you're ready

You should load up config.h as that's where the pins are assigned - and double check these instructions against it.

Also, I refuse to draw an ASCII diagram so you'll have to interpret my words.

The audio input stage expects "0" to be at around 2.5v (i.e the mid range of the analog input).

Minimum would be something like:

• ground of audio connected to ground of arduino
• signal (left or right audio channel) connected to A0 through a 3.3uF electrolytic cap
• signal connected to ground via a 103 cap
• signal connected to ground and +5v through 100k resistors (to create a potential divider to get the signal to sit at 2.5v)

That's it.

• connect 4 LEDs from D8, D9, D10, and D11 to ground A, B, G and F on a 7-segment. These will show the mode and other things. (if you don't have a 7-seg, any LEDs will do). No resistors needed

  Note that quite a lot of stuff is configurable in the config.h BUT THESE ARE NOT because we rely on them being in the half of PORTB.

• connect 2 LEDs from A1 and A2 to ground. These flash in time for the beats. I would connect them to the 7 seg in 2 of the unused positions (I use the decimal point, and the low bar.)

• Configure to other pins if you want, avoid PORTB

• Pull D7 to ground through a 10k resistor. (if you don't and it floats the mode will go haywire)
• Connect a push button from D7 to pull up to 5v. That's it
• Configure to another pin if you want, but avoid PORTB

Connect some WS2812s or whatever through a 330 resistor to D6, in "the usual way".

Powering an Arduino and lights safely / effectively is a dark art.

Choose a PSU you trust. For 1 Arduino and 2x strips of 60 NeoPixels you probably don't need more than a 2A supply because we're never going to be turning all the lights on full white and leaving them on full white. See https://learn.adafruit.com/adafruit-neopixel-uberguide/powering-neopixels for TMI about how to calculate power usage.

You can wire a 5v supply directly to the 5v pins on the Arduino, but if you do that, you bypass the fuses on the Arduino and if your PSU turns out to be untrustworthy you may end up needing to buy a new Arduino.

You can power the Arduino and lights separately, but if you do, you must connect the GND pins together.

You'll know if you don't have enough power because the thing will keep rebooting (you get a nice rainbow every time it starts up)

If you wanna watch the frame rate (and time taken to do various stages in the main loop) on an oscilloscope, you can hook an oscilloscope to pins D2 and D3. You may need to add a resistor to pull them to GND, or 5v… or you might not need to do either!

If it's working correctly when you zoom in you should see 150Hz on D3 and "other stuff" on D2 which shows phases of the draw and render. (If you want to see the sample rate specifically, you'll need to comment out the usages of DEBUG_SAMPLE_RATE_PIN and uncomment the ones in sampler.h)

Very important: you need to build against a custom branch of FastLED!

1. Set up Arduino Studio (or arduino-cli)
2. Install FastLED lib
3. REPLACE FastLED lib with the version from https://github.com/ben-xo/FastLED . My version has modifications to enable interrupts in certain places in order to not drop samples.
4. Make sure the modified FastLED is checked out to the branch feature/ben-xo-integration-branch
5. Load vu3.ino into Arduino Studio
6. edit config.h . set your strip length. maybe comment out the DEBUG defines if i left them uncommented
7. program the arduino over USB. (or use ./build-and-upload.sh if you went with arduino-cli)

N.B You may want to upgrade avr-gcc to version 11. Setting this up is out of scope of the README.

Rough instructions for that:

• brew install arduino-cli
• brew tap osx-cross/avr
• brew install avr-gcc@11
• brew link avr-gcc@11
• modify ~/Library/Arduino15/packages/arduino/hardware/avr/1.8.3/platform.txt - change compiler.path to /usr/local/bin/
• use ./build-and-upload.sh instead of Arduio Studio to program the chip

Plug the audio in. Plug the power in. Adjust the volume...

Push button to change modes. Long press to reset to auto change. Long long press to reboot. Double click and triple click get you to an animated test mode and a static test mode. (I think)

There is a screensaver which kicks in after 15 seconds silence, but when there's a signal it is back to VU. You might need to adjust the levels low or high! Sensitivity CAN be adjusted with care in sampler.cpp (adjust "scale" in sampler.cpp), or with resistors etc.

Mac owners can make open Audio MIDI Setup to create a virtual soundcard that combines both the speakers AND the line-out, so that you can play audio out loud AND into the lights simultaneously. Neat trick

• You can attach LEDs (output, LED to GND) to the LED pins mentioned in config.h. They will show a binary of which mode is currently in effect. (They're even properly PWM'd so you don't need to attach resistors, like the lazy builder you always wanted to be!)
• if you hold down the button at start up it will enter test mode and the LEDs will be a simple level meter so you can test it before attaching. the Neopixel strip
• The output from the lights pin can drive two strips with the same data so you could put them back to back to make a VU twice as long reflected in the middle!

Whilst this project has evolved (slowly) from some sketches I found online, the current code is entirely my own work.

This is "what can I squeeze out of an Arduino" project the architecture is quite Arduino specific and heavily timer interrupt driven.

The main loop does does the following:

• processes all samples queued up in the sample buffer to calculate a rolling VU, DC offset and beat detection filter
• stores sample-accurate "beat" information, and recalculates the estimates tempo (which looks a lot better for drum & bass than just the kick detection on its own)
• renders a frame of visualiser
• outputs the LEDs using FastLED

Meanwhile, there are very fast interrupt handlers for sampling the audio, doing PWM on the status LEDs, and maintaining an accurate FPS.

Yeah! You do! I have no idea what to tell you, ask me questions on Twitter @benxo I have loads of ideas and none of them are important.

Thanks for coming to my TED talk

• Worked on it throughout 2017 to 2022
• Made it public in a fit of GitHub and Twitter dopamine-seeking on 11th June 2020
• Made it all-in-one with no second arduino required for beat detect and very fast 180fps Jan 2021

Have fun and no you can't use it commercially