Content originally posted in LPCWare by frame on Mon Jan 14 12:22:59 MST 2013
Quote:
Is it possible to power some pins at 3.3V and some pins at 5V/12V.
No.
Except you want to kill your MCU.
Stick to 3.3V. Some pins may accept 5V as [B]input[/B],
but never generate more than 3.3V output.
To interface to 5V/12V circuitry, you need levelshifter/driver circuitry.
3.3V are by far enough to drive the base of a bipolar transistor, for instance.