Which GPIO on nRf52382 can be configured as timer?

Question

I'm using nRF 52383 and need one of the GPIO pins to clock an external device with 4MHz clock.
Can any GPIO be configured as clock output or is there a specific group of GPIO's that should be used for this purpose?
Looking forward to your reply. 
 Thank you
Brane

Øyvind Karlsen · Accepted Answer

Hi,

The following code using GPIOTE with PPI gives a 4MHz output on pin 18.

int main(void)
{
    nrf_gpio_range_cfg_output(18); //Configure pin 18 as output

    NRF_CLOCK->TASKS_HFCLKSTART = 1; //Start high frequency clock
    while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0)
    {
         //Wait for HFCLK to start
    }
    NRF_CLOCK->EVENTS_HFCLKSTARTED = 0; //Clear event
    
    
    //Configure GPIOTE to toggle pin 18 
    NRF_GPIOTE->CONFIG[0] = GPIOTE_CONFIG_MODE_Task << GPIOTE_CONFIG_MODE_Pos |
                            GPIOTE_CONFIG_POLARITY_Toggle << GPIOTE_CONFIG_POLARITY_Pos |
                            18 << GPIOTE_CONFIG_PSEL_Pos | 
                            GPIOTE_CONFIG_OUTINIT_Low << GPIOTE_CONFIG_OUTINIT_Pos;
    
    //Configure timer
    NRF_TIMER1->PRESCALER = 0;
    NRF_TIMER1->CC[0] = 2;  // Adjust the output frequency by adjusting the CC.
    NRF_TIMER1->SHORTS = TIMER_SHORTS_COMPARE0_CLEAR_Enabled << TIMER_SHORTS_COMPARE0_CLEAR_Pos;
    NRF_TIMER1->TASKS_START = 1;
    
    //Configure PPI
    NRF_PPI->CH[0].EEP = (uint32_t) &NRF_TIMER1->EVENTS_COMPARE[0];
    NRF_PPI->CH[0].TEP = (uint32_t) &NRF_GPIOTE->TASKS_OUT[0];
    
    NRF_PPI->CHENSET = PPI_CHENSET_CH0_Enabled << PPI_CHENSET_CH0_Pos;
    
    while (true)
    {
        // do nothing
    }
}

Because of pin crossbar almost any pin can be used, pin crossbar is essentially a mux that lets you chose any GPIO for any functionality. Please see the pin assignments for which pins are available for GPIO.

Best regards,

Øyvind