External (pin change) interrupt and power consumption I want to write a lipoly powered arduino device that can be launched from sleep mode by pressing a certain key that is connected to ground. Usually, when no in sleep mode I enable the internal pull-up resistor for a definite level. But when in sleep mode, I assume this would drain to much power and hence I want to avoid it. Is it sufficient to just wait for a pin-change interrupt on the same port pin without the internal or an additional external pull-up resistor?
You must not leave CMOS inputs floating. This will increase power consumption, and as a worst result may damage the device. Use an external pull-up if you feel that the internal pull-up passes too much current.