RTC Compare Interrupt Doesn't Happen After Debugger Halted

Question

I am using the RTC1 compare event to generate a periodic interrupt. When I halt the bugger and and then run the interrupt doesn't occur. Looking at the RTC1 register set shows the counter value is greater than the compare register. See example pictures below. Is there are away to stop this or a work around?

image description

/* Copyright (c) 2013 Nordic Semiconductor. All Rights Reserved.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the license.txt file.
 */
#include <stdbool.h>
#include <stdint.h>
#include "nrf.h"
#include "nrf_gpio.h"
#include "nrf_delay.h"

#define BUTTON_0 (17)
#define BUTTON_1 (18)

#define LED_0 (21)
#define LED_1 (22)

#define LED_START (LED_0)
#define LED_STOP (LED_1)

#define BTN_PRESSED 0
#define BTN_RELEASED 1

int main(void)
{
    // Configure BUTTON0 as a regular input
    nrf_gpio_cfg_input(BUTTON_0, NRF_GPIO_PIN_NOPULL);
    
    // Configure BUTTON1 with SENSE enabled
    nrf_gpio_cfg_sense_input(BUTTON_1, NRF_GPIO_PIN_NOPULL, NRF_GPIO_PIN_SENSE_LOW);
    
    // Configure the LED pins as outputs
    nrf_gpio_range_cfg_output(LED_START, LED_STOP);
    
    nrf_gpio_pin_set(LED_0);
    
    // Internal 32kHz RC
    NRF_CLOCK->LFCLKSRC = CLOCK_LFCLKSRC_SRC_RC << CLOCK_LFCLKSRC_SRC_Pos;
    
    // Start the 32 kHz clock, and wait for the start up to complete
    NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
    NRF_CLOCK->TASKS_LFCLKSTART = 1;
    while(NRF_CLOCK->EVENTS_LFCLKSTARTED == 0);
       
  	// Configure the RTC to generate the ISR tick 
	NRF_RTC1->PRESCALER = 0;
    
    NRF_RTC1->INTENSET = RTC_INTENSET_COMPARE0_Msk;
    NRF_RTC1->EVTENSET = RTC_EVTENSET_COMPARE0_Msk;
    NRF_RTC1->CC[0] = 256;  // interrupt at ~128Hz

    NVIC_ClearPendingIRQ(RTC1_IRQn);
    NVIC_EnableIRQ(RTC1_IRQn);

    NRF_RTC1->TASKS_START = 1;
            
    // Configure the RAM retention parameters
    NRF_POWER->RAMON = POWER_RAMON_ONRAM0_RAM0On   << POWER_RAMON_ONRAM0_Pos
                     | POWER_RAMON_ONRAM1_RAM1Off  << POWER_RAMON_ONRAM1_Pos
                     | POWER_RAMON_OFFRAM0_RAM0Off << POWER_RAMON_OFFRAM0_Pos
                     | POWER_RAMON_OFFRAM1_RAM1Off << POWER_RAMON_OFFRAM1_Pos;
    
    while(1)
    {     
      // Enter System ON sleep mode
      __WFE();  
      // Make sure any pending events are cleared
      __SEV();
      __WFE();                
    }
}

void POWER_CLOCK_IRQHandler(void)
{
  while(1);
}

void RADIO_IRQHandler(void)
{
  while(1);
}

void UART0_IRQHandler(void)
{
  while(1);
}

void RTC1_IRQHandler(void)
{
      // This handler will be run after wakeup from system ON (RTC wakeup)
    if(NRF_RTC1->EVENTS_COMPARE[0])
    {
      NRF_RTC1->EVENTS_COMPARE[0] = 0;
      NRF_RTC1->CC[0] += 256;
      nrf_gpio_pin_toggle(LED_1);
    }
}

Thanks, Darren

RK · Accepted Answer

works fine for me - do this all the time - doing it right now. I can stop the debugger as long as I like, no problem getting the compare interrupt afterwards. 
 
 
 As your display shows, the compare event is triggered and the interrupt enable bit is set. Whilst those things are true, the interrupt will be triggered. So either it's disabled, all interrupts are disabled, or you have another interrupt on another event, of higher priority, which is constantly triggering because the event isn't cleared.

RTC Compare Interrupt Doesn't Happen After Debugger Halted

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