nrf52dk systick calibration value

[shreeharsha]

Hi, I have configured systick for 1msec value with Ticks=64000. When I read the systick calibration register value, the value is 0xc0000000. This indicates the Tenms register value is zero.

The description says SoC vendor has to provide this value. Can any one help on this.

Thanks in advance.

Regards, Shreeharsha I

[Turbo J]

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.

[John]

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

[shreeharsha]

Hi John DeWitt,

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

1. So is it not possible to use systick as counter on nordic nrf52dk.
2. Can I disable sd_app_evt_wait() and use systick.
3. 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

[John]

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?

[shreeharsha]

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();,