ERROR Multiple definition of `RTC1_IRQHandler' using FreeRTOS

[asantos]

Hi, 

I am getting this compilation error when trying to use RTC1 in my program. I am already using RTC2 for a different function with no problems and I need two RTC timers.

Is the RTC1 already being used by FreeRTOS or any other module?

#include "board_basic.h"
#include "nrf52.h"
#include "boards.h"
#include "nrf_delay.h"
#include "nrf_drv_rtc.h"
#include "nrf_rtc.h"
#include "FreeRTOS.h"
#include "task.h"
#include "timers.h"
#include "semphr.h"
#include <stdio.h>
#include "sensor.h"
#include "itracker.h"
#include "nrf_log.h"
#include "nrf_drv_gpiote.h"

/**
 * @brief RTC instance number 
 *
 */
#define PERIODIC_RTC_BOX 1

/**
 * @brief RTC compare channel used
 *
 */
#define PERIODIC_RTC_BOX_CC 0
/**
 * @brief Number of RTC ticks between interrupts
 */
#define PERIODIC_RTC_BOX_US   20000000ULL			
#define PERIODIC_RTC_BOX_TICKS  (RTC_US_TO_TICKS(PERIODIC_RTC_BOX_US, RTC_DEFAULT_CONFIG_FREQUENCY))
/**
 * @brief RTC configuration
 */
static nrf_drv_rtc_config_t const m_rtc_config = NRF_DRV_RTC_DEFAULT_CONFIG;
/**
 * @brief RTC instance
 *
 * Instance of the RTC used for led blinking
 */
static nrf_drv_rtc_t const m_rtc = NRF_DRV_RTC_INSTANCE(PERIODIC_RTC_BOX);

/**
 * @brief Semaphore set in opt3001 interrupt event
 */
static SemaphoreHandle_t box_opened_semaphore = NULL;

static void periodic_rtc_handler(nrf_drv_rtc_int_type_t int_type)
{
    	NRF_LOG_DEBUG("Send data RTC handler");
    BaseType_t yield_req = pdFALSE;
	BaseType_t ret_val;
    ret_code_t err_code;
    err_code = nrf_drv_rtc_cc_set(
        &m_rtc,
        PERIODIC_RTC_BOX_CC,
        (nrf_rtc_cc_get(m_rtc.p_reg, PERIODIC_RTC_BOX_CC) + PERIODIC_RTC_BOX_TICKS) & RTC_COUNTER_COUNTER_Msk,
        true);
    APP_ERROR_CHECK(err_code);

   /* The returned value may be safely ignored, if error is returned it only means that
    * the semaphore is already given (raised). */
   UNUSED_VARIABLE(xSemaphoreGiveFromISR(box_opened_semaphore, &yield_req));
   // Request a context switch (switch to other task). Interrupt safe verison of taskYIELD()
   portYIELD_FROM_ISR(yield_req);
}

/**
 * @brief box_opened task entry function.
 *
 * @param[in] pvParameter   Pointer that will be used as the parameter for the task.
 */
void box_opened(void * pvParameter)
{	
	NRF_LOG_INFO("---------- BOX OPENED TASK ----------");
	// Utility vars
	int ret;
	ret_code_t err_code;

	// App data storage vars
	double temp = 0;
	double humidity = 0;
	double pressure = 0;
	int x = 0;
	int y = 0;
	int z = 0;
	float magnetic_x = 0;
	float magnetic_y = 0;
	float magnetic_z = 0;
	float light = 0;

	// Init GPIO & configure pin interrupt
	gpio_init();

	// Create rtc instance and compare channel
	NRF_LOG_DEBUG("Init box RTC instance");
    err_code = nrf_drv_rtc_init(&m_rtc, &m_rtc_config, periodic_rtc_handler);
    APP_ERROR_CHECK(err_code);
	
    err_code = nrf_drv_rtc_cc_set(&m_rtc, PERIODIC_RTC_BOX_CC, PERIODIC_RTC_BOX_TICKS, true);
    APP_ERROR_CHECK(err_code);
    // Enable RTC instance
	nrf_drv_rtc_enable(&m_rtc);
}

Thanks

[Einar Thorsrud]

Hi,

The FreeRTOS port use RTC1 for as a tick source, so it is not available to the application. You can see this from FreeRTOSConfig.h.

Are you sure you need an additional RTC? If you need it for some form of timers, then you can use FreeRTOS timers or the app_timer library (which is based on FreeRTOS timers in this case). These in turn use the FreeRTOS tick source, which is RTC1.

Note that it is possible to configure FreeRTOS to use SysTick instead of RTC1, but that is not recommended for several reasons (bad resolution, timer will not run when CPU is not running etc.).

[asantos]

Thanks,

I have found  a way of doing it without using any more timers.

Just one question,

Is it better to use RTC timer or app_timer / freeRTOS timer? 

Regards,

Adrian

[Einar Thorsrud]

Hi Adrian,

It doesn't really matter. The app timer library implementation for FreeRTOS uses FreeRTOS timers under the hood, so essentially it just depends on what API you prefer. The reason for having an app timer implementation for FreeRTOS is that it is needed to make all the other SDK modules that use the app timer work. If you might consider skipping FreeRTOS at some point, then using app timer might be a better option as then you would not have to change that part of the code.

[xavierl]

Hi, it appears that app_timer_start on app_timer_freertos only allows a time resolution of ~1ms. Is it possible to get a resolution of 0.1ms with FreeRTOS, just like how if I use app_timer.c?

[Einar Thorsrud]

Hi,

The time resolution depends on the tick rate, which is configured FreeRTOSConfig.h. You can increase configTICK_RATE_HZ to get a higher resolution. That might not be the best solution though, so an alternative could be to use a different timer (for instance another RTC instance or TIMER directly) if you need a higher resolution timer.