nrf52dk systick calibration value

RE: nrf52dk systick calibration value

shreeharsha — Tue, 04 Apr 2017 06:29:06 GMT

Hi John DeWitt ,

This is how am configuring RTS as counter in RIOT OS. 1.RTT_DEV->EVENTS_TICK = 1; 2.RTT_DEV->EVTENSET = 1; 3.RTT_DEV->TASKS_CLEAR = 1; 4. rtt_init();,

RE: nrf52dk systick calibration value

John — Mon, 03 Apr 2017 14:12:13 GMT

Well, I'm not an expert on the Systick feature of the nRF52 as we use the RTC peripherals because they run while sleeping. I imagine if you don't need to save power by sleeping, using systick as a counter would be possible. That said the RTC is a real time counter and is really built for that job is there a reason you would prefer the Systick (we don't have any view of your application or requirements). How are you configuring the RTC where it is missing ticks?

RE: nrf52dk systick calibration value

shreeharsha — Mon, 03 Apr 2017 06:40:32 GMT

Hi John DeWitt,

Thanks for your reply. I still have couple of questions.

So is it not possible to use systick as counter on nordic nrf52dk.
Can I disable sd_app_evt_wait() and use systick.
I tired configuring RTC as counter but missing about 30-40 ticks for 5 sec. How to get accurate count value using RTC. Am running on RIOT OS.

Looking forward for your valuable reply.

Regards, Shreeharsha.I

RE: nrf52dk systick calibration value

John — Fri, 31 Mar 2017 20:47:40 GMT

Thanks, I learned something new today on that one. @shreeharsha could also reference this answer: systick

RE: nrf52dk systick calibration value

Turbo J — Fri, 31 Mar 2017 14:30:33 GMT

The systick does not run once you use power management function like sd_app_evt_wait().

Unless you wanted a cpu load gauge in tenth of a percent, you should better use one of the other timers.

Trap for young players: The systick works as long as you have the debugger connected - this puts the NRF into a higher power mode and disables sleep modes.