Spectrum Analyzer Revisited

Encouraged by the happy ending of the Swinging Needles project, I decided to revisit an earlier audio spectrum analyzer. This time, instead of programmatically processing analog signals, I used a VS1053 plugin to let the chip do the Fourier stuff.

Before even starting to read actual frequency band values, I wanted to test my sketch by reading the plugin’s default frequency settings from VS1053’s memory. However, some of these readings made no sense at all, up to the point that I suspected a faulty chip. It took me some time to find out that the chip needs a few seconds of audio input before it will tell you something useful, even if it concerns a fixed setting like number of frequency bands.

Once the above mystery was solved, things became very straightforward. What a versatile chip this VS1053 is! While playing a 320 Kbps internet radio station, it can easily handle 14 frequency bands and let an esp8266 at 160 MHz show the results on a 128×64 Oled display.

Running the test sketch (without amplifier/speakers).


Here’s the sketch that I wrote for testing: a fixed-station internet radio (no metadata, no audio buffer), just to show a 14 band spectrum analyzer on a 128×64 SH1106 Oled display. Used pins are for the rather rare Wemos D1 R1, so you’ll probably have to change them.


This is the content of the plugin.h file that needs to be in the directory of the sketch: