Beginner's questions on nRF51822 timers

RE: Beginner's questions on nRF51822 timers

Stefan Birnir Sverrisson — Fri, 05 Jun 2015 14:27:22 GMT

Hi diode

First question: the application timers use RTC1 in the background.

Second question: Yes, that is correct, you can only wake up from System Off with reset, from GPIO or with the LPCOMP

RE: Beginner's questions on nRF51822 timers

diode — Tue, 02 Jun 2015 01:06:28 GMT

Thanks for your reply. For the first question, I realize the RTC is 24-bit, which makes sense in terms of my observation. I am still a little confused about the RTC vs Timer. What timer sources do those application timers use? I think they are two different things. For the second question, I probably meant the System Off mode. I thought it could be waken up by some internal interrupt (e.g. RTC), but it seems the only option will be GPIO event or a reset.

RE: Beginner's questions on nRF51822 timers

RK — Tue, 02 Jun 2015 00:06:19 GMT

I don't understand your first question because I'm not sure you actually asked a question. The limits on RTC for a given prescalar are in table 149 of the nRF51 series reference manual and yes at 0 the max is 512 seconds. APP_TIMER_TICKS() doesn't check for overflow, and you're overflowing it.

What do you mean by 'deep sleep' mode? No such mode is defined in the manual. There is System On - which has two different sleep modes, low power and low latency, both of which can be exited by a timer interrupt and there's System Off where the entire chip, including timers, is off and can only be woken up from a pin event or a reset.