Using PPI to enable/disable HFCLK

[shyam]

Is it possible to use PPI and RTC to turn the HFCLK on or off ? (external Xtal)

Example - something like this ... NRF_PPI->CH[9].EEP = (uint32_t) &NRF_RTC0->EVENTS_COMPARE[1]; NRF_PPI->CH[9].TEP = (uint32_t) &NRF_CLOCK->TASKS_HFCLKSTART; NRF_PPI->CHENSET = PPI_CHENSET_CH9_Msk;

NRF_PPI->CH[10].EEP = (uint32_t) &NRF_RTC0->EVENTS_COMPARE[2]; NRF_PPI->CH[10].TEP = (uint32_t) &NRF_CLOCK->TASKS_HFCLKSTOP; NRF_PPI->CHENSET = PPI_CHENSET_CH10_Msk;

Does the PPI system require the HFCLK External Xtal to be operational ?

Also, if I can't use PPI to do the above, is there another way to do it ? Perhaps using shortcuts ? As I understand, shortcuts are only for use within the same peripheral and so probably not.

[shyam]

Hi Stephan

I tried your suggestion. See below. This code doesn't work. It asserts in the end (last line).

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ASSERT(((NRF_CLOCK->HFCLKSTAT & CLOCK_HFCLKSTAT_STATE_Msk) == (CLOCK_HFCLKSTAT_STATE_NotRunning << CLOCK_HFCLKSTAT_STATE_Pos) ) || \
               ((NRF_CLOCK->HFCLKSTAT & CLOCK_HFCLKSTAT_SRC_Msk) == (CLOCK_HFCLKSTAT_SRC_RC << CLOCK_HFCLKSTAT_SRC_Pos))); /* ensure clock is stopped */

NRF_RTC0->INTENCLR = RTC_INTENCLR_COMPARE1_Msk;
NRF_RTC0->EVTENCLR = RTC_EVTENCLR_COMPARE1_Msk;
NRF_PPI->CH[9].EEP = (uint32_t) &NRF_RTC0->EVENTS_COMPARE[1];
NRF_PPI->CH[9].TEP = (uint32_t) &NRF_CLOCK->TASKS_HFCLKSTART;
NRF_PPI->CHENSET |= PPI_CHENSET_CH9_Msk;
#define TEST_TICKS (3)
#define TICKS_TO_US(ticks) ((uint64_t)ticks*(uint64_t)1000000/32768)
NRF_RTC0->CC[1] = NRF_RTC0->COUNTER + TEST_TICKS;
nrf_delay_us(TICKS_TO_US(TEST_TICKS)); /* wait until RTC fires TEST_TICKS */
nrf_delay_us(TICKS_TO_US(TEST_TICKS)); /* a little extra wait to make sure */
nrf_delay_ms(2); /* Wait 1 ms of warmup time and an extra 1 ms to make sure */
ASSERT(((NRF_CLOCK->HFCLKSTAT & CLOCK_HFCLKSTAT_STATE_Msk) == (CLOCK_HFCLKSTAT_STATE_Running << CLOCK_HFCLKSTAT_STATE_Pos) ) && \
             ((NRF_CLOCK->HFCLKSTAT & CLOCK_HFCLKSTAT_SRC_Msk) == (CLOCK_HFCLKSTAT_SRC_Xtal << CLOCK_HFCLKSTAT_SRC_Pos)));

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