How to close pull-up resistor of the RX pin in NCS 1.9.1

[Hannibalhz]

Dear Nordic Engineers

I am study NCS 1.9.1 and I have a problem I would like to know.

I look for UART config in board_common.dts file, the RX default config is pull-up.

Then I look for nordic,nrf-uart-common.yaml file,I did not find other config to close the pull-up resistor on the RX pin.

So I would like to know how to close the pull-up resistor on the RX pin in NCS 1.9.1

Please give me some good suggestion.

Best regards.

.

[Simon]

If rx-pull-up is set by default in the board folder, you can remove it using /delete-property/, similar to how it's done here: https://github.com/nrfconnect/sdk-nrf/blob/v1.9.1/samples/bluetooth/hci_lpuart/boards/nrf9160dk_nrf52840.overlay#L9-L10 

Be aware when/if you upgrade to NCS v2.0.0, the pin configuration changes quite a bit: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/nrf/ug_pinctrl.html#migration-of-the-devicetree-files 

Best regards,

Simon

[Hannibalhz]

Dear Simon

Thank you for your suggestion.I try to add "/delete-property/ rx-pull-up" in .overlay file. It's  effective.

I study NCS2.0.0 and I have a new question.

As we all know, we can like the following to define uart in NCS1.9.1.

/* old board.dts */
&uart0 {
    ...
    tx-pin = <5>;
    rx-pin = <33>;
    rx-pull-up;
    ...
};

I read this link  https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/nrf/ug_pinctrl.html#migration-of-the-devicetree-files ,it means I must like the following to define uart in NCS2.0.0

&uart0 {
    ...
    pinctrl-0 = <&uart0_default>;
    pinctrl-1 = <&uart0_sleep>;
    pinctrl-names = "default", "sleep";
    ...
};
&pinctrl {
    uart0_default: uart0_default {
        group1 {
            psels = <NRF_PSEL(UART_TX, 0, 5)>;
        };
        group2 {
            psels = <NRF_PSEL(UART_RX, 1, 1)>;
            bias-pull-up;
        };
    };
    uart0_sleep: uart0_sleep {
        group1 {
            psels = <NRF_PSEL(UART_TX, 0, 5)>,
                    <NRF_PSEL(UART_RX, 1, 1)>;
            low-power-enable;
        };
    };
};

The link shows:

• default - Peripheral in working mode.

• sleep - Peripheral in sleep mode or low power mode.

So I would like to know the program must use default and sleep?  What's the difference between them?

If the program uses the together, how do they switch two mode in the program?

Best regards.

[Simon]

Could you open a new ticket about this? Since your initial question about the rx-pull-up field is answered?