[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 ...

The term “Charileplexing” is not a familiar one for many electronics hobbyists. Charlieplexing is a technique proposed in early 1995 by Charlie Allen (at Maxim Integrated) for driving a multiplexed ...