Arduino boards

 https://alselectro.wordpress.com/2017/05/14/arduino-pro-mini-how-to-upload-code/

https://www.portsfuture.com/wp-content/uploads/2019/03/Lesson-2-LED-Sound.pdf

http://www.whatimade.today/lets-make-some-signal-processing-with-an-arduino/

https://thesolaruniverse.wordpress.com/2019/08/20/connecting-a-128x64-oled-display-with-ssd1306-driver-to-an-arduino-with-a-spi-interface/