This is a wiring diagram that [Soranne] put together when developing a method of programming PIC microcontrollers using an Arduino board. You can see that he takes care of the 12V issue by connecting ...

[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… ...