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

The official Arduino team has this week revealed more details about the new Arduino UNO R4 development Board which will be officially launching in a few months time during May 2023. The ...

The Arduino UNO R4 Minima and the Arduino UNO R4 WiFi. But apart from the obvious wireless connectivity hinted by the name what other differences do the microcontrollers have.