Optiboot (an older version) is installed by default on the Arduino Uno and (as of 2018) official Arduino Nano boards. It can be installed on all older mega8, 168 or 328 based Arduinos. As of 2019, ...

This is the easiest and fastest way to get the LED Clock up and running. I mostly use "ESP-WROOM-32 Devkit" as microcontroller for my projects (I may will move to ESP32-C5 in the future as this is the ...