RE: Outputting 32.768kHz clock signal to a GPIO using GPIOTE and DPPI on an nRF5340-DK

Naeem Maroof — Wed, 07 Feb 2024 11:09:47 GMT

Hello,

I am not sure which source your code is based on, but I can see that you are setting up the endpoints for ppi channel:

// Connect TICK event of the RTC to the output pin using PPI and GPIOTE
NRF_PPI->CH[0].EEP = (uint32_t)&NRF_RTC0->EVENTS_TICK;
NRF_PPI->CH[0].TEP = (uint32_t)&NRF_GPIOTE->TASKS_OUT[0];

I can also see that this is something which is being done in the nrf_ppi_channel_endpoint_setup() function that is available in the nrf_ppi.h

NRF_STATIC_INLINE void nrf_ppi_channel_endpoint_setup(NRF_PPI_Type *    p_reg,
                                                      nrf_ppi_channel_t channel,
                                                      uint32_t          eep,
                                                      uint32_t          tep)
{
    p_reg->CH[(uint32_t) channel].EEP = eep;
    p_reg->CH[(uint32_t) channel].TEP = tep;
}

As on the 5340, there is DPPI, you can start by looking at the nrf_dppi.h and nrfx_gppi.h (within this file we have if-defined block that checks whether it is PPI or the DPPI) and the source files.

For example, in the nrfx_gppi_dppi.c, we have:

void nrfx_gppi_event_endpoint_setup(uint8_t channel, uint32_t eep)
{
    NRFX_ASSERT(eep);
    NRF_DPPI_ENDPOINT_SETUP(eep, channel);
}

void nrfx_gppi_task_endpoint_setup(uint8_t channel, uint32_t tep)
{
    NRFX_ASSERT(tep);
    NRF_DPPI_ENDPOINT_SETUP(tep, channel);
}

void nrfx_gppi_channel_endpoints_setup(uint8_t  channel, uint32_t eep, uint32_t tep)
{
    nrfx_gppi_event_endpoint_setup(channel, eep);
    nrfx_gppi_task_endpoint_setup(channel, tep);
}

where the MACRO (as below) defined in the nrf_dppi.h is used:

#define NRF_DPPI_ENDPOINT_SETUP(task_or_event, dppi_chan)                                        \
        (*((volatile uint32_t *)(task_or_event + NRF_SUBSCRIBE_PUBLISH_OFFSET(task_or_event))) = \
            ((uint32_t)dppi_chan | NRF_SUBSCRIBE_PUBLISH_ENABLE))

So probably you can call those functions available in the header files.

/BR, Naeem