RE: HW control for RTC

Peter — Tue, 22 Sep 2015 05:29:52 GMT

If I understand you correctly, you want to use the RTC directly instead of using the timer library which is documented here infocenter.nordicsemi.com/index.jsp ?

If you use a softdevice, you need to check which RTC instance is available in the SoftDevice Specification. Good chances are that the RTC1 is available.

Here's an example of how to set the RTC up for a compare interrupt using only bare metal registers:

    NRF_RTC1->PRESCALER = 327;
	NRF_RTC1->INTENSET = (RTC_INTENSET_TICK_Enabled << RTC_INTENSET_TICK_Pos);
	NRF_RTC1->EVTENSET = (RTC_EVTENSET_TICK_Enabled << RTC_EVTENSET_TICK_Pos);
	
	NRF_RTC1->INTENSET = 
    (RTC_INTENSET_COMPARE0_Enabled << RTC_INTENSET_COMPARE0_Pos);
	NRF_RTC0->EVTENSET = 
    (RTC_EVTENSET_COMPARE0_Enabled << RTC_EVTENSET_COMPARE0_Pos);
	
    NVIC_SetPriority(RTC1_IRQn,3);
	NVIC_ClearPendingIRQ(RTC1_IRQn);
	NVIC_EnableIRQ(RTC1_IRQn);
	
	NRF_RTC1->TASKS_START = 1;
	
	NRF_RTC1->CC[0] = NRF_RTC1->COUNTER + 5;

Then just implement interrupt handler:

void RTC0_IRQHandler(void)
{
	
	if(NRF_RTC0->EVENTS_TICK )
	{
		...
     }
		NRF_RTC0->EVENTS_TICK = 0;
	}
	else if(NRF_RTC0->EVENTS_COMPARE[0])
	{
           ...
		
		NRF_RTC0->CC[0] = NRF_RTC0->COUNTER + 5;
		NRF_RTC0->EVENTS_COMPARE[0] = 0;
	}
}

RE: HW control for RTC

Petter Myhre — Mon, 21 Sep 2015 13:20:41 GMT

There is an RTC example in SDK 9.0.0, see this. Are you using a SoftDevice?