The Arduino Uno-compatible board has an MCS-51 (often called 8051 instead) instead of the usual ATmega328P/ATmega168. Specifically, [ElectroBoy] uses the AT89S52.

Hardware Electronics flexible arduino Arduino Uno gets bendable "Flexduino" remake, flaunting a cheery yellow hue Say goodbye to boards that break when you flex them By Zo Ahmed August 27, 2024 at ...

Arduino UNO R4 Minima Both Arduino UNO R4 boards retain hardware compatibility with the UNO form factor and 5V operating voltage meaning you can keep using existing shields. They also add HID support ...

Massimo Banzi, co-founder and chairman of Arduino, announced the UNO R4 during Arduino Day 2023. He believes the UNO R4 is a new chapter in the UNO story and the perfect way to move forward, ...