david Barriere

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6 years ago.

How works gpio_init for the targets Nordic nRF5x?

I don't understand how the GPIO initialization is working when considering the following:

The function void gpio_init(gpio_t *obj, PinName pin) is resetting the configuration for all pins.

nrf_drv_gpiote_init()
...
for (i = 0; i < NUMBER_OF_PINS; i++)
    {
        pin_in_use_clear(i);
    }

1 Answer

Ralph Fulchiero
6 years ago.

Hi David,

We have edited your question to include code tags to improve its readability.

The constructors for DigitalIn and DigitalOut will call gpio_init(), which in turn will call nrf_drv_gpiote_init() for the nRF52 targets. We can see your concern, but you might not have noticed this portion of the function:

    if (m_cb.state != NRF_DRV_STATE_UNINITIALIZED)
    {
        err_code = NRF_ERROR_INVALID_STATE;
        NRF_LOG_WARNING("Function: %s, error code: %s.",
                        (uint32_t)__func__,
                        (uint32_t)NRF_LOG_ERROR_STRING_GET(err_code));
        return err_code;
    }

Only on the first pass through the function will the initialization take place. On subsequent calls m_cb.state equals NRF_DRV_STATE_INITIALIZED (from line 252), so no initialization will be performed as the function will return prematurely.

Hopefully that satisfies your concern.

Regards, Ralph, Team Mbed

Accepted Answer

OK. but it seems strange to get a warning/error code for each (except the first) pin initialization !

posted by david Barriere 06 Nov 2018