fungus:
majenko:
"Never assume anything as it makes an Ass out if U and Me"They're CMOS chips, so they use MOSFETs. It's rare for BJTs to be in logic / MCU chips these days.
OK...I retract everything I said so far.
You don't need to retract everything... It's still the case that you can't (or certainly shouldn't) use digital IO pins as ground. Sinks, yes, but not grounds.