Hey
Im working on a project which requires the Ndogo to wake up from power-down-mode every 3 hours.
What can I use to trigger to Ndogo to wake up?
I read something about a watchdog timer, but that one only lasts 8 seconds max. before interrupt.
Ive also seen people use a ‘RTC’, can I use this for my problem with a Ndogo?
thx
I remember something about that library that the prescaler /divider was set in the library.
you can alter it. it should increase the time past 8 seconds.
For how many seconds do you want it to sleep?
Err… more like 3 hours 
Unlike the Mbili, the Ndogo does not have an external RTC onboard.
You could use an DS3231 on an external break out board.
The library supports both periodic and a single scheduled interrupt (up to 24 hours in adavance).
You could either use a regular shorter term interrupt and test and then execute what tasks are due, or you could schedule a longer term interrupt for specific time between the tasks.
So that means my best options is to use a watchdog interrupt, keeping up a counter?
Yes, that might be a good way to start.
Just a note, if you were planning on using the millis() function, in some sleep modes the timer which increments that value is turned off.