Is this just the atmega chip itself providing the watchdog and power saving functionalities, and therefor the energy saving potential?
So all you need is activate it by code when you have time/cycles to spare in your implementation?

And if yes, are there any drawbacks associated with going into power saving mode and handing execution over to the watchdog (except from not being able to execute code during power saving, obviously)?
How about switching to power saving/watchdog more often for shorter amounts of time? Will there still be a benefit?

Thanks for your input =)
cun83

P.S.: First \o/

Why this guy, who know how to standby the Arduino, continues to use an external quartz while having plenty of internal clocks is difficult to understand !

The atmegaX8 series (like the atmega168) have a useful feature to get accurate periodic wake up and sleep operation.

You run the AVR on internal oscillator, I choose 1 MHz and change the clock divider to 4MHz so it will operate from 1.8V to 5.5V.

You connect a 32KHz watch crystal to the crystal connections of the AVR. Dont forget the load capacitors.

When you turn on timer 2 in asynchronous mode, and enable to use the crystal oscillator. You can go to power-save mode where most of the controller is powered down, but the timer 2 interrupt will periodically wake the AVR up.

Using the interrupt of timer 2, and the proper divisor you can wake up 1024 times per second. Useful for a small operating system scheduler.

I use this setup in a small wireless sensor network I am developing. I need a quite accurate timer to have reasonably accurate synchronisation between nodes. It is not really needed but improves power efficiency.

yay, arduino-a-day is here again.

Timed sleep states are a great power saver when you don’t need real-time availability. But what I’m interested in is how to permanently put it to sleep and wake it up on button press (ground int pin). I know it’s possible, but I haven’t found any good write ups on how to do this. I’ve read what’s out there, and nothing is really clear to me.

Yaaa, I think experts should start reading IEEE journals and stuff …

Mike: i dont think they were talking about you, you had a valid comment and i would also like to know how to wake on button.

that’s what I want, but I’m still not clear on how to implement that in my code.

Actually, my pin change setup story was not completely correct.

You just setup the pins, and there are 3 interrupts for each AVR port. If you wish to know what pin changed you need to keep a backup register so you can see what pin changed by XORing the backup register with the current port.

I hate geeks. I mean really hate them. Particularly the geekier-than-thou kind. “I mean arduino, is soooooooo mainstream dude, real men build their own microcontroller from two pins and a lemon.”