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PPI to SWI/EGU connection

SDK: 15.2
IDE: Keil
Softdevice: S132 v 6.0

General question about PPI connections.  Is it possible to setup a PPI channel, that when triggered by some event (e.g. value in RTC counter matches compare register CC[0]), triggers a software interrupt/handler where I can run some code?

Thanks,

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  • Yes, this is possible. I have put together a simple example if you want to test it out:

    /**
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     */
    /** @file
     *
     * @defgroup blinky_example_main main.c
     * @{
     * @ingroup blinky_example
     * @brief Blinky Example Application main file.
     *
     * This file contains the source code for a sample application to blink LEDs.
     *
     */
    
    #include <stdbool.h>
    #include <stdint.h>
    #include "nrf_delay.h"
    #include "boards.h"
    
    void SWI0_EGU0_IRQHandler(void)
    {
        /* Clear event register */
        NRF_EGU0->EVENTS_TRIGGERED[0] = 0;
    
        bsp_board_led_invert(BSP_BOARD_LED_0);
    }
    
    
    /* Start LF clock source for RTC */
    void clock_init()
    {
        NRF_CLOCK->LFCLKSRC = CLOCK_LFCLKSTAT_SRC_Xtal << CLOCK_LFCLKSTAT_SRC_Pos;
        NRF_CLOCK->TASKS_LFCLKSTART = 1;
        while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0);
    }
    void rtc_init()
    {
        NRF_RTC2->CC[0] = 32768;
        /* Event signal must be enabled explicitly unlike most other peripherals */
        NRF_RTC2->EVTENSET = RTC_EVTEN_COMPARE0_Msk;
        NRF_RTC2->TASKS_START = 1;
    }
    void ppi_interrupt_init()
    {
        /* 6 is the default int. priority used in SDK drivers */
        NVIC_SetPriority(SWI0_EGU0_IRQn, 6);
        NVIC_EnableIRQ(SWI0_EGU0_IRQn);
    
        NRF_EGU0->INTENSET = EGU_INTEN_TRIGGERED0_Msk;
    
        NRF_PPI->CH[0].EEP = (uint32_t) &NRF_RTC2->EVENTS_COMPARE[0];
        NRF_PPI->CH[0].TEP = (uint32_t) &NRF_EGU0->TASKS_TRIGGER[0];
        /* RTC does not have a SHORT to clear counter on compare match
           so using PPI instead */
        NRF_PPI->FORK[0].TEP = (uint32_t) &NRF_RTC2->TASKS_CLEAR;
    
        NRF_PPI->CHENSET = PPI_CHENSET_CH0_Msk;
    }
    
    /**
     * @brief Function for application main entry.
     */
    int main(void)
    {
        /* Configure board. */
        bsp_board_init(BSP_INIT_LEDS);
    
        clock_init();
        rtc_init();
        ppi_interrupt_init();
    
        /* Wait for interrupts */
        while (true)
        {
           __WFI();
        }
    }
    
    /**
     *@}
     **/
    

    The example is configured to toggle a LED from the EGU0 ISR once every second.

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