How to configure default state of GPIO ouput

RE: How to configure default state of GPIO ouput

ampad — Tue, 09 Apr 2019 22:05:35 GMT

Digging through the code as @awneil suggested, I found that nrf_gpio_pin_set() simply updates the OUTSET register, so the pin does not need to be configured as output first. Calling this before configuring the pin as output results in the behavior I was looking for.

nrf_gpio_pin_set(pin);
nrf_gpio_cfg(pin,
    NRF_GPIO_PIN_DIR_OUTPUT,
    NRF_GPIO_PIN_INPUT_DISCONNECT,
    NRF_GPIO_PIN_NOPULL,
    NRF_GPIO_PIN_S0D1,
    NRF_GPIO_PIN_NOSENSE);

RE: How to configure default state of GPIO ouput

awneil — Tue, 09 Apr 2019 20:53:50 GMT

You can see the source of nrf_gpio_cfg() - it just writes to the PIN_CNF register.

Check the Product Specification for register descriptions & to see if there's an option to do what you want...

RE: How to configure default state of GPIO ouput

ampad — Tue, 09 Apr 2019 19:57:33 GMT

It does have an external pullup, I am configuring the pin in an open drain configuration using NRF_GPIO_PIN_S0D1 as the drive type as follows"

    nrf_gpio_cfg(pin,
        NRF_GPIO_PIN_DIR_OUTPUT,
        NRF_GPIO_PIN_INPUT_DISCONNECT,
        NRF_GPIO_PIN_NOPULL,
        NRF_GPIO_PIN_S0D1,
        NRF_GPIO_PIN_NOSENSE);

When this function is called, the pin is pulled low as the default state for the output pin is cleared. What I am looking for is a way for the value associated with the pin to be set to 1 (i.e. disconnected) at configuration time so that the pin is not pulled low.

RE: How to configure default state of GPIO ouput

Fred — Tue, 09 Apr 2019 19:15:06 GMT

Unless I understand it incorrectly, if you need to be sure that it is high even before you have started your program adn/or do the configuration, I guess you would required a pull-up on the board?