Problems using the nRF5340's P0.21 pin as a GPIO output

[seongbin]

Hello,

I am developing an nRF5340 custom board by setting the pins as shown below.

- P0.19: UART_RX
- P0.20 : UART_TX
- P0.21: GPIO Output

I have a problem when trying to use the P0.21 pin as a GPIO output that used to be used as UART_CTS on the nRF5340DK.

When I add below code in app.overlay file and set GPIO values to 0 and 1, it always outputs 0.

&pinctrl {

    uart0_default: uart0_default {

        group1 {

            psels = <NRF_PSEL(UART_TX, 0, 20)>;

        };

        group2 {

            psels = <NRF_PSEL(UART_RX, 0, 19)>;

            bias-pull-up;

        };

    };

    uart0_sleep: uart0_sleep {

        group1 {

            psels = <NRF_PSEL(UART_TX, 0, 20)>,

                <NRF_PSEL(UART_RX, 0, 19)>;

            low-power-enable;

        };

    };

}

However, if the above code is removed from the app.overlay file and the nrf5340_cpuapp_common-pinctrl.dtsi file of the nRF Connect SDK is modified as above, it works fine.

I think it is not correct to modify the nrf5340_cpuapp_common-pinctrl.dtsi file.

Could you please let me know if there is a way to use P0.21 by modifying the app.overlay file?

Regards,
Seongbin

[Øivind]

Hi,

Could you try replacing the instances of uart0_default and uart0_sleep with some other name?
For example, add _alt to the end.

Remember to replace the names in the uart0 node as well:

&uart0 {
    pinctrl-0 = <uart0_default_alt>;
    pinctrl-1 = <uart0_sleep_alt>;
};

[seongbin]

Hi Øivind,

Thank you for your reply.

I tried adding the code below to app.overlay but I have the same problem.

&pinctrl {

    uart0_default_alt: uart0_default_alt {

        group1 {

            psels = <NRF_PSEL(UART_TX, 0, 20)>;

        };

        group2 {

            psels = <NRF_PSEL(UART_RX, 0, 19)>;

            bias-pull-up;

        };

    };

    uart0_sleep_alt: uart0_sleep_alt {

        group1 {

            psels = <NRF_PSEL(UART_TX, 0, 20)>,

                <NRF_PSEL(UART_RX, 0, 19)>;

            low-power-enable;

        };

    };

}

&uart0 {
    pinctrl-0 = <uart0_default_alt>;
    pinctrl-1 = <uart0_sleep_alt>;
};

Regards,
Seongbin

[Øivind]

Could you try adding these two lines to your pinctrl node in the overlay?

&pinctrl {
    /delete-node/ uart0_default;
    /delete-node/ uart0_sleep;
    uart0_default_alt: uart0_default_alt {

[seongbin]

I tried adding the code below to app.overlay and my code but I have the same problem.

in app.overlay :

&pinctrl {

    /delete-node/ uart0_default;
    /delete-node/ uart0_sleep;
    
    uart0_default_alt: uart0_default_alt {
        group1 {
            psels = <NRF_PSEL(UART_TX, 0, 20)>;
        };
        group2 {
            psels = <NRF_PSEL(UART_RX, 0, 19)>;
            bias-pull-up;
        };
    };

    uart0_sleep_alt: uart0_sleep_alt {
        group1 {
            psels = <NRF_PSEL(UART_TX, 0, 20)>,
                <NRF_PSEL(UART_RX, 0, 19)>;

            low-power-enable;
        };
    };
};

&uart0 {
    pinctrl-0 = <&uart0_default_alt>;
    pinctrl-1 = <&uart0_sleep_alt>;
};

in my code : 

gpio_pin_configure_dt(&g_p0_21_gpio, GPIO_OUTPUT);
gpio_pin_set_dt(&g_p0_21_gpio, 0 or 1);

 

[Øivind]

Could I please see the build/zephyr/zephyr.dts file? Either attach the file, or copy it into a code block.