Switch contact debouncing. I found this resource helpful.

[wilfred]

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[SirNick]

That's a lesson every micro newbie has to learn the hard way.  I managed to reliably crash an Arduino with a mechanical rotary encoder by trying to use interrupts.  If you twirled the knob fast enough, it would lock up and/or restart.

That read-and-shift code works really well.  I consider that the ideal software debounce method, although I do tend to use the dumb routine (sample, wait 50ms, sample again, compare) for minor hobby projects.

[georges80]

Seems a little 'extreme' to just state not to connect a switch to an interrupt pin. I do that on most of my designs, wakeup on interrupt or pin change (interrupt). Once awake I then disable further interrupts on that pin and transition to a timer driver interrupt routine that then samples and debounces the switch. Very easy to implement.

So, yes, connecting a switch with bounce to an interrupt pin AND trying to use interrupts to detect switch status is not a good idea, but no reason to not use an interrupt pin as the wakeup source.

I can safely say that with several 10's of thousands of shipped boards that this scheme works 'just fine'...

cheers,
george.