RTC compare event

[TML_YT]

I am testing the RTC example in nRF5 SDK v17.1.0.

This example shows LED1 switching at a rate of 8 Hz and LED2 lighting up after 3 seconds.

This is confirmed.

The programme shows that the action after 3 seconds is performed by a compare event interrupt, but only one entry is made to this interrupt.

I would like to repeat this interrupt every three seconds to make LED2 blink, but please tell me exactly how to change the programme.

[Jared]

Hi there,

You need to clear the counter and reset the compare interrupt like this:

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/** @file
 * @defgroup rtc_example_main main.c
 * @{
 * @ingroup rtc_example
 * @brief Real Time Counter Example Application main file.
 *
 * This file contains the source code for a sample application using the Real Time Counter (RTC).
 *
 */

#include "nrf.h"
#include "nrf_gpio.h"
#include "nrf_drv_rtc.h"
#include "nrf_drv_clock.h"
#include "boards.h"
#include "app_error.h"
#include <stdint.h>
#include <stdbool.h>

#define COMPARE_COUNTERTIME  (3UL)                                        /**< Get Compare event COMPARE_TIME seconds after the counter starts from 0. */

#ifdef BSP_LED_0
    #define TICK_EVENT_OUTPUT     BSP_LED_0                                 /**< Pin number for indicating tick event. */
#endif
#ifndef TICK_EVENT_OUTPUT
    #error "Please indicate output pin"
#endif
#ifdef BSP_LED_1
    #define COMPARE_EVENT_OUTPUT   BSP_LED_1                                /**< Pin number for indicating compare event. */
#endif
#ifndef COMPARE_EVENT_OUTPUT
    #error "Please indicate output pin"
#endif

const nrf_drv_rtc_t rtc = NRF_DRV_RTC_INSTANCE(0); /**< Declaring an instance of nrf_drv_rtc for RTC0. */

/** @brief: Function for handling the RTC0 interrupts.
 * Triggered on TICK and COMPARE0 match.
 */
static void rtc_handler(nrf_drv_rtc_int_type_t int_type)
{
    if (int_type == NRF_DRV_RTC_INT_COMPARE0)
    {
        nrf_gpio_pin_toggle(COMPARE_EVENT_OUTPUT);
        nrf_drv_rtc_counter_clear(&rtc);
        int err_code = nrf_drv_rtc_cc_set(&rtc,0,COMPARE_COUNTERTIME * 8,true);
        APP_ERROR_CHECK(err_code);
     
    }
    else if (int_type == NRF_DRV_RTC_INT_TICK)
    {
        nrf_gpio_pin_toggle(TICK_EVENT_OUTPUT);
    }
}

/** @brief Function configuring gpio for pin toggling.
 */
static void leds_config(void)
{
    bsp_board_init(BSP_INIT_LEDS);
}

/** @brief Function starting the internal LFCLK XTAL oscillator.
 */
static void lfclk_config(void)
{
    ret_code_t err_code = nrf_drv_clock_init();
    APP_ERROR_CHECK(err_code);

    nrf_drv_clock_lfclk_request(NULL);
}

/** @brief Function initialization and configuration of RTC driver instance.
 */
static void rtc_config(void)
{
    uint32_t err_code;

    //Initialize RTC instance
    nrf_drv_rtc_config_t config = NRF_DRV_RTC_DEFAULT_CONFIG;
    config.prescaler = 4095;
    err_code = nrf_drv_rtc_init(&rtc, &config, rtc_handler);
    APP_ERROR_CHECK(err_code);

    //Enable tick event & interrupt
    nrf_drv_rtc_tick_enable(&rtc,true);

    //Set compare channel to trigger interrupt after COMPARE_COUNTERTIME seconds
    err_code = nrf_drv_rtc_cc_set(&rtc,0,COMPARE_COUNTERTIME * 8,true);
    APP_ERROR_CHECK(err_code);

    //Power on RTC instance
    nrf_drv_rtc_enable(&rtc);
}

/**
 * @brief Function for application main entry.
 */
int main(void)
{
    leds_config();

    lfclk_config();

    rtc_config();

    while (true)
    {
        __SEV();
        __WFE();
        __WFE();
    }
}


/**  @} */

Alternatively:

static void rtc_handler(nrf_drv_rtc_int_type_t int_type)
{
    static int counter = 2;
    if (int_type == NRF_DRV_RTC_INT_COMPARE0)
    {
        nrf_gpio_pin_toggle(COMPARE_EVENT_OUTPUT);
        //Set compare channel to trigger interrupt after COMPARE_COUNTERTIME seconds
        int err_code = nrf_drv_rtc_cc_set(&rtc,0,((COMPARE_COUNTERTIME * 8)*counter) % 0x1000000,true);
        APP_ERROR_CHECK(err_code);
        counter++;
    }
    else if (int_type == NRF_DRV_RTC_INT_TICK)
    {
        nrf_gpio_pin_toggle(TICK_EVENT_OUTPUT);
    }
}

regards

Jared

[TML_YT]

Reply, thank you.

Regarding the first example.
Regarding clearing the counter in the interrupt and resetting the compare interrupt, I was trying the same code (two lines of the following).
     nrf_drv_rtc_counter_clear(&rtc);
     int err_code = nrf_drv_rtc_cc_set(&rtc,0,COMPARE_COUNTERTIME * 8,true);
I just did not have the 'APP_ERROR_CHECK(err_code)' statement.

The result was the same as when I did it, only one time into the 'if (int_type == NRF_DRV_RTC_INT_COMPARE0)' interrupt.
Thanks to the 'err code' I could see that it was stopping at 'NRF_BREAKPOINT_COND' in 'app_error_weak.c', but the cause was not clear to me.

Regarding the second example.
This method worked.
I would like to try to apply this method to change the repetition cycle and send packets in that cycle. By the way, when transmitting, I plan to use ESB for the protocol with low consumption.

[Jared]

Hi,

TML_YT said:

The result was the same as when I did it, only one time into the 'if (int_type == NRF_DRV_RTC_INT_COMPARE0)' interrupt.
Thanks to the 'err code' I could see that it was stopping at 'NRF_BREAKPOINT_COND' in 'app_error_weak.c', but the cause was not clear to me.

Strange, I tested this method and it worked for me. Could share the error message and check the return value from nrf_drv_rtc_cc_set()?

TML_YT said:

Regarding the second example.
This method worked.
I would like to try to apply this method to change the repetition cycle and send packets in that cycle. By the way, when transmitting, I plan to use ESB for the protocol with low consumption.

Good, then you have a working alternative

regards

Jared