Method of high precision timer count

RE: Method of high precision timer count

Håkon Alseth — Tue, 04 Jun 2019 10:40:48 GMT

You can use interrupt priority 2, as levels 0 and 1 are reserved for the softdevice:

https://infocenter.nordicsemi.com/topic/sds_s132/SDS/s1xx/processor_avail_interrupt_latency/exception_mgmt_sd.html?cp=3_4_1_0_15_1

Kind regards,

Håkon

RE: Method of high precision timer count

yokokawa — Tue, 04 Jun 2019 00:20:21 GMT

I am using HFXO (32 MHz crystal).
I would like to raise the priority of the timer interrupt so as not to affect the BLE communication function. How far can you raise it?
Thank you.

RE: Method of high precision timer count

Håkon Alseth — Mon, 03 Jun 2019 11:59:24 GMT

Hi,

Timer-wise, both should have the same accuracy.

Both implementations use the CPU for incrementing a variable, where the PPI example uses two timers, one in counter mode, and one in capture/compare mode.

To get an accurate timer, remember to start the external HFCLK (NRF_CLOCK->TASKS_HFCLKSTART = 1;), as the default behavior is to run on the internal 64 MHz RC oscillator.

If you want to synchronize based on an external signal, I'd recommend that you look into the GPIOTE IN functionality, and use PPI to either count or provide an event on either rising or falling edge.

Kind regards,

Håkon

RE: Method of high precision timer count

yokokawa — Mon, 03 Jun 2019 00:07:31 GMT

Other than the above, is there any way to create a timer that counts correctly?
This timer needs to be synchronized with another device.