https://votecharlie.com/blog/2016/03/fft-examples.html
https://www.arduinolibraries.info/libraries/arduino-fft
Прочитать!
https://www.waitingforfriday.com/?p=53
http://wiki.openmusiclabs.com/wiki/ArduinoFHT
FFT для меги
http://arduino.ru/projects/analizator-spektra-zvuka-na-arduino
https://www.arduinolibraries.info/libraries/arduino-fft
http://wiki.openmusiclabs.com/wiki/ArduinoFFT