[Trent M. Wyatt]’s CPUVolt library provides a fast way to measure voltage using no external components, and no I/O pin. It only applies to certain microcontrollers, but he provides example Arduino ...
Arduino is launching new versions of the Uno board powered by a Renesas 32bit microcontroller. The Uno R4 comes in two versions: the basic Uno R4 Minima and the Espressif-equipped Uno R4 WiFi.