[mannkind]

Interesting! I guess that I'm not using the lowest power mode[1], but for months now I have had a ATMega328P (running on 3-AA batteries) monitoring doors w/reed switches. I haven't had any trouble w/interrupts not firing on change.

1: I'm using Rocket Scream's LowPower.PowerDown for what it's worth.

[tonyd256]

Cool, there probably isn't a huge difference between idle and deep sleep modes so I'm sure it could still last a long time. In deep sleep you can still use the HIGH & LOW level interrupts but just not the CHANGE one.