nRF52x - Two ways to connect RADIO events to GPIOTE with PPI

method1_nrfx_drivers.c

// Pro: The nrfx drivers keep track of which PPI and GPIOTE channels are in used.

static void alloc_assign_enable_nrfx_ppi(nrf_ppi_channel_t* p_channel, 
                                          uint32_t event_end_point,
                                          uint32_t task_end_point)
{
#if (!NRFX_PPI_ENABLED)
#error "Require enabling NRFX_PPI_ENABLED in sdk_config.h. In nRF5 SDK, also check PPI_ENABLED (refer to apply_old_config.h)"
#endif

    nrfx_err_t err;

    if (!nrfx_gpiote_is_init())
    {
        APP_ERROR_CHECK(NRFX_ERROR_INVALID_STATE);
    }
    
    err = nrfx_ppi_channel_alloc(p_channel);
    APP_ERROR_CHECK(err);

    err = nrfx_ppi_channel_assign(*p_channel,
                                  event_end_point,
                                  task_end_point
                                  );
    APP_ERROR_CHECK(err);

    err = nrfx_ppi_channel_enable(*p_channel);
    APP_ERROR_CHECK(err);
}

static void config_then_enable_gpiote_via_nrfx(uint8_t port, uint8_t pin)
{
#if (!NRFX_GPIOTE_ENABLED)
#error "Require enabling NRFX_GPIOTE_ENABLED in sdk_config.h. In nRF5 SDK, also check GPIOTE_ENABLED (refer to apply_old_config.h)"
#endif
    nrfx_err_t err;

    nrfx_gpiote_out_config_t nrfx_gpiote_out_config_led_common = {
            .action     = NRF_GPIOTE_POLARITY_TOGGLE,
            .init_state = NRF_GPIOTE_INITIAL_VALUE_LOW,
            .task_pin   = true
    };
    err = nrfx_gpiote_out_init(NRF_GPIO_PIN_MAP(port, pin), &nrfx_gpiote_out_config_led_common);
    APP_ERROR_CHECK(err);

    nrfx_gpiote_out_task_enable(NRF_GPIO_PIN_MAP(port, pin));
}

static void radio_ppi_gpiote_setup_nrfx(void)
{
    nrfx_err_t err;

    err = nrfx_gpiote_init();
    APP_ERROR_CHECK(err);

    config_then_enable_gpiote_via_nrfx(LED_PORT, LED1_PIN);
    config_then_enable_gpiote_via_nrfx(LED_PORT, LED2_PIN);

    nrf_ppi_channel_t nrf_ppi_channel_set_led1;
    nrf_ppi_channel_t nrf_ppi_channel_clr_led1;
    nrf_ppi_channel_t nrf_ppi_channel_set_led2;
    nrf_ppi_channel_t nrf_ppi_channel_clr_led2;

    alloc_assign_enable_nrfx_ppi(
            &nrf_ppi_channel_clr_led1,
            nrf_radio_event_address_get(NRF_RADIO_EVENT_TXREADY),
            nrfx_gpiote_clr_task_addr_get(NRF_GPIO_PIN_MAP(LED_PORT, LED1_PIN))
    );
  
    alloc_assign_enable_nrfx_ppi(
            &nrf_ppi_channel_set_led1,
            nrf_radio_event_address_get(NRF_RADIO_EVENT_END),
            nrfx_gpiote_set_task_addr_get(NRF_GPIO_PIN_MAP(LED_PORT, LED1_PIN))
    );

    alloc_assign_enable_nrfx_ppi(
            &nrf_ppi_channel_clr_led2,
            nrf_radio_event_address_get(NRF_RADIO_EVENT_RXREADY),
            nrfx_gpiote_clr_task_addr_get(NRF_GPIO_PIN_MAP(LED_PORT, LED2_PIN))
    );

    alloc_assign_enable_nrfx_ppi(
            &nrf_ppi_channel_set_led2,
            nrf_radio_event_address_get(NRF_RADIO_EVENT_END),
            nrfx_gpiote_set_task_addr_get(NRF_GPIO_PIN_MAP(LED_PORT, LED2_PIN))
    );
}

method2_direct_register_write.c

// Con: need to keep track of which PPI and GPIOTE channels are in used.

static void radio_ppi_gpiote_setup_direct_register_macro(void)
{
#define LED_PORT  0
#define LED1_PIN  13
#define LED2_PIN  14
#define GPIOTE_CHANNEL_FOR_LED1   0 /* 0..7, can't reuse */
#define GPIOTE_CHANNEL_FOR_LED2   1 /* 0..7, can't reuse */
#define PPI_CHANNEL_FOR_LED1_SET  0 /* 0..19 for nRF52840, can't reuse */
#define PPI_CHANNEL_FOR_LED2_SET  1 /* 0..19 for nRF52840, can't reuse */
#define PPI_CHANNEL_FOR_LED1_CLR  2 /* 0..19 for nRF52840, can't reuse */
#define PPI_CHANNEL_FOR_LED2_CLR  3 /* 0..19 for nRF52840, can't reuse */

    NRF_GPIOTE->CONFIG[GPIOTE_CHANNEL_FOR_LED1] = (uint32_t)
            ( GPIOTE_CONFIG_MODE_Task << GPIOTE_CONFIG_MODE_Pos ) |
            ( LED_PORT << GPIOTE_CONFIG_PORT_Pos ) |
            ( LED1_PIN << GPIOTE_CONFIG_PSEL_Pos ) |
            //( GPIOTE_CONFIG_POLARITY_Toggle << GPIOTE_CONFIG_POLARITY_Pos ) |
            ( GPIOTE_CONFIG_OUTINIT_High << GPIOTE_CONFIG_OUTINIT_Pos );
    NRF_GPIOTE->CONFIG[GPIOTE_CHANNEL_FOR_LED2] = (uint32_t)
            ( GPIOTE_CONFIG_MODE_Task << GPIOTE_CONFIG_MODE_Pos ) |
            ( LED_PORT << GPIOTE_CONFIG_PORT_Pos ) |
            ( LED2_PIN << GPIOTE_CONFIG_PSEL_Pos ) |
            //( GPIOTE_CONFIG_POLARITY_Toggle << GPIOTE_CONFIG_POLARITY_Pos ) |
            ( GPIOTE_CONFIG_OUTINIT_High << GPIOTE_CONFIG_OUTINIT_Pos );

    NRF_PPI->CH[PPI_CHANNEL_FOR_LED1_CLR].EEP = 
            (uint32_t) (&NRF_RADIO->EVENTS_TXREADY);
    NRF_PPI->CH[PPI_CHANNEL_FOR_LED1_CLR].TEP = 
            (uint32_t) (&NRF_GPIOTE->TASKS_CLR[GPIOTE_CHANNEL_FOR_LED1]);

    NRF_PPI->CH[PPI_CHANNEL_FOR_LED1_SET].EEP = 
            (uint32_t) (&NRF_RADIO->EVENTS_END);
    NRF_PPI->CH[PPI_CHANNEL_FOR_LED1_SET].TEP = 
            (uint32_t) (&NRF_GPIOTE->TASKS_SET[GPIOTE_CHANNEL_FOR_LED1]);

    NRF_PPI->CH[PPI_CHANNEL_FOR_LED2_CLR].EEP = 
            (uint32_t) (&NRF_RADIO->EVENTS_RXREADY);
    NRF_PPI->CH[PPI_CHANNEL_FOR_LED2_CLR].TEP = 
            (uint32_t) (&NRF_GPIOTE->TASKS_CLR[GPIOTE_CHANNEL_FOR_LED2]);

    NRF_PPI->CH[PPI_CHANNEL_FOR_LED2_SET].EEP = 
            (uint32_t) (&NRF_RADIO->EVENTS_END);
    NRF_PPI->CH[PPI_CHANNEL_FOR_LED2_SET].TEP = 
            (uint32_t) (&NRF_GPIOTE->TASKS_SET[GPIOTE_CHANNEL_FOR_LED2]);

    NRF_PPI->CHENSET =  (0x1 << PPI_CHANNEL_FOR_LED1_CLR) | 
                        (0x1 << PPI_CHANNEL_FOR_LED1_SET) | 
                        (0x1 << PPI_CHANNEL_FOR_LED2_CLR) | 
                        (0x1 << PPI_CHANNEL_FOR_LED2_SET);
}