Quick note: ATmega based Arduino boards (UNO, Nano, Mini, Mega) takes about 100us to read an analogue input, so the maximum reading rate is about 10,000 times second. Below you can see a “CIE1931 Fade ...

What was your first Arduino program? Probably an LED blinker — that seems to be the “hello world” of microcontrolllers. You probably moved on to things a little more complicated pretty quickly.

Two encoders are used to recreate the famous Etch-A-Sketch interface, hooked up to an Arduino Nano that then communicates encoder data to the Pi over I2C, due to the limited GPIOs available.