RTC0 IRQ/event on overflow?

RE: RTC0 IRQ/event on overflow?

Gordon — Mon, 26 Sep 2016 14:15:28 GMT

Thanks - looks like a great solution. It's a shame it requires app_timer changes though - it's hard enough changing SDK versions even without having modified anything!

RE: RTC0 IRQ/event on overflow?

Susheel Nuguru — Sat, 24 Sep 2016 22:37:03 GMT

please go through this thread. @clemtaylor has implemented a good way of counting the overflows mostly using LFCLK. Even though the solution is on older SDK, it should not be too many API changes in app_timer in latest SDK

RE: RTC0 IRQ/event on overflow?

butch — Sat, 24 Sep 2016 15:23:03 GMT

Queueing a <512 second repeating timer is a simpler solution than I had in mind. The handler would tick the long-running clock MSB. But wouldn't you need to start it so that it expired exactly when the RTC rolls over? I don't understand why the RTC would stop (if the app_timer library is bulletproof)? But it would be nice to have an existing implementation of a long-running clock (using app_timer) that is provably correct. In my case I am not using SoftDevice, so I can use the RTC that app_timer is not using, at the expense of more current.

RE: RTC0 IRQ/event on overflow?

Gordon — Sat, 24 Sep 2016 14:07:34 GMT

Yes - enhancing app_timer would be really good. I guess simply queuing a <512 second repeating task would probably be fine, but some kind of example of doing this would be really helpful (especially to give me a bit more reassurance that the RTC would never stop).

RE: RTC0 IRQ/event on overflow?

butch — Sat, 24 Sep 2016 11:33:47 GMT

I have the same need. I think this is a request for an enhancement to app_timer: even if the app does not have any timers running, app_timer should generate an event/callback when the RTC rolls over so that the app can keep a long-running (64-bit) clock. Lacking that enhancement, as Gordon says, the app needs to always have a timer running with timeout less than 512 seconds. The handler for that timer checks the counter of the RTC to determine whether it has rolled over, and makes appropriate "ticks" on the high order bits of the long running clock. The timer must be for less than 512 seconds else the RTC rolls over twice, missing a tick on MSB of the long running clock. Maybe the request is for a long running clock library that wraps or cooperates with app_timer library. Or the request is for a reference to example code for a long-running clock that uses app_timer.

RE: RTC0 IRQ/event on overflow?

Gordon — Sat, 24 Sep 2016 09:12:58 GMT

ok, so what's the suggested solution for getting a usable RTC for getting the time on an nRF51? It seems like a common thing to want to do.

RE: RTC0 IRQ/event on overflow?

Susheel Nuguru — Fri, 23 Sep 2016 19:18:29 GMT

You are right that the softdevice is using RTC0 and you are not allowed to use it in anyways unless you use TImeslot API. How are you using RTC0?