PPI to SWI/EGU connection

Question

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, 
 E

Vidar Berg · Answer

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

/**
 * Copyright (c) 2014 - 2019, Nordic Semiconductor ASA
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 *
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 *
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
/** @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.

PPI to SWI/EGU connection

Top Replies