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Topic: Unused Analog Inputs Atmega328 - question (Read 1 time) previous topic - next topic

Lsnyman

If I am deploying a stand alone projevt and only use 1 of the analog inputs, does it provide any benefit to enable the pull up resistors on the unused pins?
I am thinking of stability more than  anything else.

Nick Gammon

It probably won't hurt. The analog reading is actually done "on command" (ie. when you do an analogRead), it isn't just reading away for its amusement. But setting unused pins to a known value is probably going to help keep noise out of the processor.

Lsnyman

Thank you Nick, So following what you said, I shouldnt add anything to the current draw either? The device is battery operated.

Nick Gammon

Well you could put in pull-down resistors to tie them low. That shouldn't consume much, if anything. Pull-ups will add to the current drawn (as you would expect) according to my measurements here:

http://www.gammon.com.au/forum/?id=11497

Nick Gammon

You can save substantial amounts of power by just running from 3.3V rather than 5V, BTW.

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