You can also use the power down mode, then TIMER0 is automatically disabled. I'll be going back to this soon since the RF12 watchdog approach isn't good enough yet. See http://news.jeelabs.org/2009/05/16/power-consumption-more-savings/ etc.
I wouldn't worry too much about waking up, even once a millisecond - the trick it to start up fast (fuse settings), to do little, and to go back to sleep as quickly as possible.
Thanks for the hints Kellerza!! I will try to check properly what is happening and compare with the current situation.
But yesterday I was too eager to just verify that the timer was indeed waking it up every msec, so I uploaded the sketch into another JeeNode, and added a serial port output on the loop. I was expecting a lot of output in between the 2 seconds wakeup of the watchdog, but these didn't come - all I got was a print every 2 seconds...so maybe indeed the power down mode is switching off the TIME0 like the key-master :) Jean-Claude said above.
I will try to investigate better these cases.
Meanwhile, just would like to report that the station has been outside, during the polar weather spell we are having here with consistent negative temperatures, for 25 days now, and still broadcasting! next time I open it I will try to implement the battery measuring with the 2 big resistors divider.
Sorry amvv, missed the power down mode in your code - Jean-Claude is right about that one disabling all timers.
I decided to implement the extra power saving by switching off the radio while sleeping, so today I opened up the weather station.
Good news: the battery, after more than one month is still at 4.08V while the system sleeps, which is the same as when I opened it a couple of weeks ago for water proofing...I start to think that they will last long!
So I put in the RF12_sleep() with no radio watchdog, and did some optimizations in the code, e.g. to switch off the light sensor as soon as possible, and reduce the processing instructions in the loop (there was one unnecessary "for"). I am also now sleeping for 8 seconds between cycles, and sending the packet 3 times in a row, to decrease lost packages...I was getting about 50% reception recently...Lets see if it improves.
I will put the code on the wiki soon.
With the multimeter, I could read 1.2uA, but it is not a very good multimeter...I could not make a reading when the sketch didn't have the rf12_sleep...couldn't figure out why...
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