RE: How to read data coming from an external board via UART with nrF5340?

dejans — Fri, 27 Jan 2023 17:48:19 GMT

Hi Miguel,

Welcome to the Nordic world. Regarding UART, there is echo_bot sample which can help you to get started with Nordic development. When building the sample for nRF52840dk_nrf52840 in VS Code, you can see UART configuration in nrf52840dk_nrf52840-pinctrl.dtsi and nrf52840dk_nrf52840.dts files: Here is relevant application part in VS Code:

Similar to Sandro's answer, relevant (UART) configuration from nrf52840dk_nrf52840-pinctrl.dtsi file is shown below.

/*
 * Copyright (c) 2022 Nordic Semiconductor
 * SPDX-License-Identifier: Apache-2.0
 */

&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;
		};
	};
...
};

In the same echo_bot sample, there is a file called nrf52840dk_nrf52840.dts with UART configuration shown below.

&uart0 {
	compatible = "nordic,nrf-uarte";
	status = "okay";
	current-speed = <115200>;
	pinctrl-0 = <&uart0_default>;
	pinctrl-1 = <&uart0_sleep>;
	pinctrl-names = "default", "sleep";
};

When building for nRF52840-DK board, both above-mentioned files are taken from <your_ncs_installation_folder>\zephyr\boards\arm\nrf52840dk_nrf52840 folder.

You can read more about devicetree and pin control in the documentation.

Best regards,
Dejan

RE: How to read data coming from an external board via UART with nrF5340?

Sandro_r — Fri, 27 Jan 2023 06:49:26 GMT

Hello Miguel,

If you followed this base example closely and it does not work, a likely problem is that the devicetree-overlay is not complete.

&uart0 {
		compatible = "nordic,nrf-uarte";
		reg = <0x8000 0x1000>;
		interrupts = <8 NRF_DEFAULT_IRQ_PRIORITY>;
		status = "okay";
		current-speed = <115200>;
		pinctrl-0 = <&uart0_default>;
		pinctrl-1 = <&uart0_sleep>;
		pinctrl-names = "default", "sleep";
};

&uart0_default {
		group1 {
				psels = <NRF_PSEL(UART_TX, 0, 29)>,
						<NRF_PSEL(UART_RTS, 0, 27)>;
		};
		group2 {
				psels = <NRF_PSEL(UART_RX, 0, 28)>,
						<NRF_PSEL(UART_CTS, 0, 26)>;
				bias-pull-up;
		};
};
&uart0_sleep {
		group1 {
				psels = <NRF_PSEL(UART_TX, 0, 29)>,
						<NRF_PSEL(UART_RX, 0, 28)>,
						<NRF_PSEL(UART_RTS, 0, 27)>,
						<NRF_PSEL(UART_CTS, 0, 26)>;
				low-power-enable;
		};
};

It should look something like that. You can choose the UART-GPIOs with the ‘psels’ properties in the ‘uartX_default’ and the ‘uartX_sleep’ nodes which are referenced in the ‘uart0’ node. To activate the UART driver the ‘status’ property in the ‘uart0’ node must be set to “okay”.

My process of creating the overlay is by looking up the needed nodes in the ‘Compiled devicetree output’ (which can be opened in the SDK) and referencing them in the overlay with ‘&LABEL’.

Regards,

Sandro