RE: Configure second UART on nRF52840 DK

Kazi Afroza Sultana — Tue, 29 Oct 2024 12:46:36 GMT

Hello,

I can try to explain adding UART pin in device tree. You have to create a pinctrl.dtsi file. For example, if following pin set up are for your board-pinctrl.dtsi file (This is from our nrf52840 board file),

&pinctrl {
	uart0_default: uart0_default {
		group1 {
			psels = <NRF_PSEL(UART_TX, 0, 6)>,
				<NRF_PSEL(UART_RTS, 0, 5)>;
		};
		group2 {
			psels = <NRF_PSEL(UART_RX, 0, 8)>,
				<NRF_PSEL(UART_CTS, 0, 7)>;
			bias-pull-up;
		};
	};

	uart0_sleep: uart0_sleep {
		group1 {
			psels = <NRF_PSEL(UART_TX, 0, 6)>,
				<NRF_PSEL(UART_RX, 0, 8)>,
				<NRF_PSEL(UART_RTS, 0, 5)>,
				<NRF_PSEL(UART_CTS, 0, 7)>;
			low-power-enable;
		};
	};

	uart1_default: uart1_default {
		group1 {
			psels = <NRF_PSEL(UART_RX, 1, 1)>;
			bias-pull-up;
		};
		group2 {
			psels = <NRF_PSEL(UART_TX, 1, 2)>;
		};
	};

	uart1_sleep: uart1_sleep {
		group1 {
			psels = <NRF_PSEL(UART_RX, 1, 1)>,
				<NRF_PSEL(UART_TX, 1, 2)>;
			low-power-enable;
		};
	};

you can write this on overlay file with the same pin number but with different name (for example: uart0_default_alt instead of uart0_default)

All upstream boards define both default and sleep states. Overlays also need to define both.

If the board does not have the power management application, you can write like this

&pinctrl {
    uart0_default_alt: uart0_default_alt {
        ...
    };
};

&uart0 {
    ...
    pinctrl-0 = <&uart0_default_alt>;
    /delete-property/ pinctrl-1;
    pinctrl-names = "default";
    ...
};

&pinctrl {
    uart0_default_alt: uart0_default_alt {
        ...
    };
};

&uart0 {
    ...
    pinctrl-0 = <&uart0_default_alt>;
    /delete-property/ pinctrl-1;
    pinctrl-names = "default";
    ...
};

&pinctrl {
    uart0_default_alt: uart0_default_alt {
        ...
    };
};

&uart0 {
    ...
    pinctrl-0 = <&uart0_default_alt>;
    /delete-property/ pinctrl-1;
    pinctrl-names = "default";
    ...
};

&pinctrl {
    uart0_default_alt: uart0_default_alt {
        ...
    };
};

&uart0 {
    ...
    pinctrl-0 = <&uart0_default_alt>;
    /delete-property/ pinctrl-1;
    pinctrl-names = "default";
    ...
};

&pinctrl {
    uart0_default_alt: uart0_default_alt {
        ...
    };
};

&uart0 {
    ...
    pinctrl-0 = <&uart0_default_alt>;
    /delete-property/ pinctrl-1;
    pinctrl-names = "default";
    ...
};

&pinctrl {
    uart0_default_alt: uart0_default_alt {
        ...
    };
};

&uart0 {
    ...
    pinctrl-0 = <&uart0_default_alt>;
    /delete-property/ pinctrl-1;
    pinctrl-names = "default";
    ...
};

RE: Configure second UART on nRF52840 DK

Kazi Afroza Sultana — Mon, 28 Oct 2024 14:45:13 GMT

Hello,

P0.28 and P0.29 are for low frequency only. You should avoid the low frequency pins.

RE: Configure second UART on nRF52840 DK

Sameera Nasrin — Mon, 21 Oct 2024 11:26:59 GMT

Hi,

I have selected P0.28 and P0.29 for TX and RX respectively. I would like to confirm if these are the correct GPIO pins for second UART or uart1 on the nRF52840 DK. Additionally, I would appreciate it if someone could share an appropriate overlay file for enabling and configuring UART2 using these pins.

RE: Configure second UART on nRF52840 DK

Kazi Afroza Sultana — Mon, 21 Oct 2024 10:30:21 GMT

Hello,

You can select ay available GPIO pins for second UART. This link may help (+) Pin connection of second UART interface with nRF52840 - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)