Drive Strength of UART pins

[mexco]

 I need to use High Drive Strength of pin used as TX of UART. How may it be done using zephyr ?

[Simon]

Try using the field nordic,drive-mode like it's done in nrf/boards/arm/nrf5340_audio_dk_nrf5340/nrf5340_audio_dk_nrf5340_cpuapp_common-pinctrl.dtsi. Set it to any of the modes defined in nrf-pinctrl.h

Best regards,

Simon

[mexco]

is it to be set in Overlay file or at the time of Initialization of pin using DT_GET_.... ? Please, write as per example

[Simon]

I think it should be enough setting it in the overlay, then I think the uart driver will set the drive through uart_nrfx_uarte.c-->pinctrl_apply_state()-->pinctrl_configure_pins() at boot.

Try reading the PIN_CNF-->DRIVE register after booting up and see if it's set correctly. You can read it from main() or just through nrfjprog.

For example if you're reading GPIO pin 0 (nonsecure), you read from address 0x40842500 (nonsecure) + 0x200 + (0 (P0.0) × 0x4) = 0x40842700

nrfjprog --memrd 0x40842700 --n 4

Best regards,

Simon

[mexco]

pls explain how to write in overlay ?

[Simon]

Add the following to an overlay file nrf9160dk_nrf9160_ns.overlay:

&pinctrl {
    uart0_default: uart0_default {
        group1 {
            psels = <NRF_PSEL(UART_TX, 0, 29)>,
                <NRF_PSEL(UART_RTS, 0, 27)>;
                nordic,drive-mode = <NRF_DRIVE_H0H1>;
        };
        group2 {
            psels = <NRF_PSEL(UART_RX, 0, 28)>,
                <NRF_PSEL(UART_CTS, 0, 26)>;
            bias-pull-up;
            nordic,drive-mode = <NRF_DRIVE_H0H1>;
        };
    };
};

I tested this with the hello world sample attached below:

hello_world_high_drive.zip

I built it with NCS v2.0.0 and the board nrf9160dk_nrf9160_ns. After flashing it to the board, I read the PIN_CNF of P0.29 (uart TX), and got the following result:

@$ nrfjprog --memrd 0x40842774 --n 4
0x40842774: 00000303                              |....|

0x303 is 0011 0000 0011 in binary, and if you look at PIN_CNF, you can see that 11 (3 in decimal) on position 8 and 9 corresponds to H0H1:

Best regards,

Simon

[mexco]

Hi.. I need same again but without using pinctrl. I need to use following style to set drive strentgh.

&uart2{

    current-speed = < 115200 >;

    tx-pin = <2>;

    rx-pin = <3>;

    status = "okay";

};

How , may it be done ?

Meanwhile, I temporarily added following  function and called it in uart_init() function by manually writing Pin Number as below:

NRF_STATIC_INLINE void nrf_gpio_cfg_output_strong(uint32_t pin_number)

{

    nrf_gpio_cfg(

        pin_number,

        NRF_GPIO_PIN_DIR_OUTPUT,

        NRF_GPIO_PIN_INPUT_DISCONNECT,

        NRF_GPIO_PIN_NOPULL,

        NRF_GPIO_PIN_H0H1,

        NRF_GPIO_PIN_NOSENSE);

}

void uart_init()

{

  ... 

  nrf_gpio_cfg_output_strong(2); // used Tx pin of UART2

  ......

}

Though above method worked very well, but is not recommendable, because Pin Number got fixed. How to get Pin Number as set in overlay file instead of fixed, I don't know ?