QDEC high power consumption

RE: QDEC high power consumption

Håkon Alseth — Fri, 21 Jun 2019 13:15:30 GMT

Try disabling the UART (nrf_log module). It'll keep the HFCLK running in sleep.

RE: QDEC high power consumption

bevis — Fri, 21 Jun 2019 07:22:12 GMT

I have the same question. According to the answers below, if LFCK is turned on, am I using it in the wrong way?And I'm a little confused about this result.The use of RTC on or off QDEC regularly to achieve low power consumption??Or something else?

RE: QDEC high power consumption

Sergiooo — Mon, 18 Jun 2018 08:57:06 GMT

Yes, it works excellent. QDEC draws only 0.8uA. RTC instance required, however. I am providing sample code in case someone would encounter same problems.

int main(void)
{  
	
	NRF_CLOCK -> TASKS_LFCLKSTART = 1;
	while((NRF_CLOCK -> LFCLKSTAT  & CLOCK_LFCLKSTAT_STATE_Msk) == 0);
	
	NRF_RTC0 -> PRESCALER = 60;
	NRF_RTC0 -> EVTENSET =1;
	NRF_RTC0 -> TASKS_START = 1;
	
	NRF_QDEC ->ENABLE = 1;
	NRF_QDEC ->SHORTS = 2;
	NRF_QDEC ->LEDPOL = 0;
	NRF_QDEC ->LEDPRE = 10;
	NRF_QDEC ->SAMPLEPER = 0;
	NRF_QDEC ->PSEL.A = 25;
	NRF_QDEC ->PSEL.B = 24;
	NRF_QDEC ->PSEL.LED = 20;	
	
	NRF_PPI ->CH[0].EEP = (uint32_t)&(NRF_RTC0 ->EVENTS_TICK);
	NRF_PPI ->CH[0].TEP = (uint32_t)&(NRF_QDEC->TASKS_START);
	NRF_PPI ->CHENSET=1;
	
	while(true){
	 __SEV();
	__WFI();
	__WFI();
	}	
	
}

RE: QDEC high power consumption

Sergiooo — Fri, 15 Jun 2018 12:36:47 GMT

Thank you for clarification. I will try to use PPI then. Unfortunately, encoder draws 15 mA while sensing, so there is no way to use GPIOTE

RE: QDEC high power consumption

Håkon Alseth — Fri, 15 Jun 2018 07:49:50 GMT

Hi,

The QDEC peripheral requires the 16M clock tree to run, which adds approx. 400 uA (depending on the HFCLK source) in sleep. The recommended method, wrt. power consumption, is to enable the QDEC when required, and disable it before going to sleep. You can use a pin-interrupt on both inputs to re-enable the QDEC when waking up from sleep.

Best regards,

Håkon