Developed by Jonathan MacArt 2012-2020
Dependencies:
Tested using an Arduino Uno and individually addressable WS2811 LEDs, but other combinations are likely possible. In-use examples:
This provides a ready-to-use Arduino program for audio visualization via the fast Fourier transform (FFT). The signal is sent to individually addressable LEDs. Key features are:
-
The program reads pin A0 for an audio signal, which it expects to be conditioned to 2.5 V mean with +/- 2.5 V peak-to-peak (assuming you use a 5 V microcontroller). I describe my signal-conditioning circuit below.
-
The
fix_fftlibrary does most of the heavy lifting; it computes a fixed-point-precision, in-place FFT with significantly higher performance than a floating-point FFT. -
The program computes an exponential moving average of the FFT bins and sends this to user-defined LED bins using
FastLED. -
The program has two modes: active, FFT-based visualization, which it enters when an input signal is detected, and "standby" pre-programmed visualizations, to which it reverts otherwise. My principal use has been Christmas tree lighting, so the included visualizations are mostly along these lines. Others are certainly possible; just use the included ones as templates.
Your line-level audio signal most likely has a mean of 0 V; we need to shift this to the center of your ADC's range (e.g., 2.5 V for 5-volt devices). Unless you're using a 1.6-volt microcontroller, we also likely need to apply some gain. My input (line-level) audio signal is about 0.6 V peak-to-peak.
The following circuit applies a gain of 6x and shifts the signal to approximately 2.5 V mean. The line-level audio signal goes to Vin. Vout goes to your ADC.
Here's the built-up circuit on an Adafruit screw shield. I use a Texas Instruments TLE2021 Excalibur Op-Amp, but others will likely work too. The blue wire is Vin in the diagram above. Green provides the conditioned signal (Vout) to A0. Yellow (digital pin 10) sends the digital signal to the addressable LEDs.
A final shot showing the conditioned output of a 1 kHz sine wave at about +2.5 V mean.
