nrf52832 timer

RE: nrf52832 timer

sreehari410 — Fri, 01 Dec 2017 12:36:39 GMT

I'm using the SDK V11.0, setting the RTC_config_frequency to 8 and the RTC to timeout at 24 hours (i.e 691200 ticks passed to nrf_drv_rtc_cc_set ()). I'm able to get the RTC timeout once after 24 hours with this configuration. Can you let me know how the SDK bug can affect the working of RTC?

RE: nrf52832 timer

Ankit — Fri, 01 Dec 2017 06:29:54 GMT

If I use app_timer, then at what frequency my soc will wake up? If app_timer is generic timer which wakes up every 10ms and if it counts for 24 hours on behalf of me, then it is not usefull to me as I want to sleep(soc must be sleeping) for max period of time.

RE: nrf52832 timer

Dave_couling — Fri, 01 Dec 2017 06:02:04 GMT

Why not just use an app_timer with a variable that you count up with in the handler. I believe (due to an SDK bug) ~4hrs was the maximum timeout you could set an RTC to. So after 6 timeouts you have your 24hrs elapsed

RE: nrf52832 timer

Joakim Jakobsen — Thu, 30 Nov 2017 13:22:34 GMT

I'm glad you were able so solve it!
Maybe you could convert the comment to an answer and mark it as correct, so that others can see that the issue has been resolved?
Best regards,
Joakim.

RE: nrf52832 timer

Ankit — Thu, 30 Nov 2017 13:19:40 GMT

Yes we got it what we want. And yes we are using RTC2 as RTC0 and RTC1 are not available and being used by Softdevice.

Thank you.

RE: nrf52832 timer

AmbystomaLabs — Thu, 30 Nov 2017 13:03:20 GMT

Ok, sounds like you have it figured out. I just wanted to remind you that if you use a soft device you can't use RTC0, but RTC1 and RTC2 are available.

RE: nrf52832 timer

Ankit — Thu, 30 Nov 2017 05:09:23 GMT

I changed RTC_freq to 8 and now I am able to configure RTC to count for 24 days. Yes we are using soft device s132_nrf52_2.0.0_softdevice.hex

RE: nrf52832 timer

AmbystomaLabs — Wed, 29 Nov 2017 15:00:43 GMT

Ankit, are you using a soft device?

RE: nrf52832 timer

Joakim Jakobsen — Wed, 29 Nov 2017 13:52:39 GMT

Hi Ankit.
When using a prescaler of 0, the RTC will overflow after 512 seconds. Like AmbystomaLabs said in his comment above, using the max prescaler value (2^12-1=4095) the RTC will overflow after 582.542 hours or ~24 days. More information here.

RE: nrf52832 timer

Ankit — Wed, 29 Nov 2017 08:29:24 GMT

Hi nordic support.

I have tried to do it using RTC in comparator mode, but it gives me a max sleep time of 512 seconds. I want a timer that can count for me for maximum time.

Can you share a sample code or a readily available example code? I am referring SDK V11.0.

RE: nrf52832 timer

AmbystomaLabs — Mon, 27 Nov 2017 14:23:08 GMT

The RTC will easily accommodate this and is the preferred method of handling sleep/wake cycles of the cpu since it is the lowest power clock. Since the RTC has a 12 bit prescaler and 24 bit counters with one compare event you can run it for 2^24/(32768/2^12) eighth second intervals or about 24 days before it overflows. The ISR from the RTC event will wake the processor up after you put it in low power mode.