PWM pins work the same way across all Arduino boards, so you don't need to go out of your way to buy a Mega if you already have a board supporting PWM. On the Uno, Nano, and Mini, the PWM pins are ...

Enter the ExtraCore library for Arduino, a software library that turns two or more Arduinos into a multi-core microcontroller with more pins than you’ll ever need.

[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 Ar… ...