Can't get RTC to work with __RFE() but can make it work with __RFI()

Question

I can make the RTC work with interrupts and __WFI(). I absolutely can't get events and __RFE() to work for the RTC. However, it works if I replace the __RFE() with __NOP(), so the RTC and events *seem* to be configured properly.

I've just got to be missing something stupidly obvious. Any help would be appreciated.

Thanks.

Code included which works on a nrf52832 (PCA10040 board):

#include <stdbool.h>
#include <stdint.h>

// $SDK/modules/nrfx
#include "mdk/nrf52_bitfields.h"

#include "hal/nrf_gpio.h"
#include "hal/nrf_clock.h"
#include "hal/nrf_rtc.h"


#include "delay/nrf_delay.h"


#define PIN_LED 19 // LED1

static unsigned irq_counter = 0;



#define RTC_USE_IRQ 0
#define RTC_USE_EVENT 1


#if RTC_USE_IRQ

void RTC0_IRQHandler(void) {
    nrf_rtc_event_clear(NRF_RTC0,NRF_RTC_EVENT_TICK);
    irq_counter++;
    // every 8 IRQs, we toggle the led -> 1Hz rate
    if(irq_counter %8 == 0) nrf_gpio_pin_toggle(PIN_LED);
}

int main(void)  // THIS VERSION WORKS FINE
{
    nrf_gpio_cfg_output(PIN_LED);
    nrf_gpio_pin_set(PIN_LED); // LED is off


    // Irq setup
    NVIC_SetPriority(RTC0_IRQn, 15); // Lowes priority
    NVIC_ClearPendingIRQ(RTC0_IRQn);
    NVIC_EnableIRQ(RTC0_IRQn);

    // Start LFCLK clock
    nrf_clock_lf_src_set(NRF_CLOCK_LFCLK_RC); // 32KHz RC
    nrf_clock_task_trigger(NRF_CLOCK_TASK_LFCLKSTART);


    // Set prescaler to the max value (12-bit)
    // -> 8Hz counter frequency
    nrf_rtc_prescaler_set(NRF_RTC0,(1<<12) -1);
    nrf_rtc_event_enable(NRF_RTC0, NRF_RTC_INT_TICK_MASK); /* yes INT mask must be used here */
    nrf_rtc_int_enable(NRF_RTC0,NRF_RTC_INT_TICK_MASK);
    nrf_rtc_task_trigger(NRF_RTC0,NRF_RTC_TASK_START);

    while(1) {
        __WFI();
    };
}
#endif

#if RTC_USE_EVENT

int main(void)  // THIS VERSION FAILS
{
    nrf_gpio_cfg_output(PIN_LED);
    nrf_gpio_pin_set(PIN_LED); // LED is off

    // Start LFCLK clock
    nrf_clock_lf_src_set(NRF_CLOCK_LFCLK_RC); // 32KHz RC
    nrf_clock_task_trigger(NRF_CLOCK_TASK_LFCLKSTART);

    // Set prescaler to the max value (12-bit)
    // -> 8Hz counter frequency
    nrf_rtc_prescaler_set(NRF_RTC0,(1<<12) -1);
    nrf_rtc_event_enable(NRF_RTC0, NRF_RTC_INT_TICK_MASK); /* yes INT mask must be used here */
    nrf_rtc_task_trigger(NRF_RTC0,NRF_RTC_TASK_START);

    while(1) {
        if (nrf_rtc_event_pending(NRF_RTC0, NRF_RTC_EVENT_TICK)) {  // __WFE could be a NOP()--so you have to check
            nrf_rtc_event_clear(NRF_RTC0,NRF_RTC_EVENT_TICK);
            irq_counter++;
            // every 8 IRQs, we toggle the led -> 1Hz rate
            if(irq_counter %8 == 0) nrf_gpio_pin_toggle(PIN_LED);
        }

        __WFE();  // If you replace this with __NOP() things work fine--so events are triggering
    };
}

#endif

Vidar Berg · Accepted Answer

Hello, 
 The RTC peripheral itself will not generate an event to wake the processor. To make the RTC raise a system wide event that can wake the CPU you must connect the event signal to the NVIC by setting the INTENSET register. Please take a look at this thread: https://devzone.nordicsemi.com/f/nordic-q-a/53795/nrf52832-does-not-wake-up-on-event-using-__wfe I think it may answer your questions.

Can't get RTC to work with RFE() but can make it work with RFI()

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