uart0 overlay for hello_world app

[Bret Foreman]

I've got a custom board based on the nRF52810 SoC. I want to use GPIO P0.06 for UART_TX and P0.08 for UART_RX. I used the new board wizard in nRF Connect to create a new board based on the nrf52810 and added the following overlay code:

&uart0 {
    status = "okay";
    compatible = "nordic,nrf-uart";
    tx-pin = < 6 >;
    rx-pin = < 8 >;
    current-speed = < 115200 >;
    parity = "none";
    rts-pin = < 0xffffffff >;
    cts-pin = < 0xffffffff >;
};

The app builds and appears to run (I can step in the debuger), but I'm not seeing the "Hello World" text output on GPIO pin P0.06.

I'm guessing I need to add some more stuff to my overlay file. What am I missing?

Project folder attached here.

7360.hello_world.zip

[Bret Foreman]

I'm continuing to research this issue. In the file C:\ncs\v2.2.0\zephyr\dts\bindings\serial\nordic,nrf-uart-common.yaml\nordic,nrf-uart-common.yaml I find that the terms tx-pin and rx-pin are deprecated if the "pin control driver" is not used. But I'm pretty sure I want to use pin control, since it's the way things are supported in the future. So I started researching the driver here:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/nrf/ug_pinctrl.html#ug-pinctrl

So I think the example I need is how to do an overlay file that uses pin control to re-map the UART pins with the nRF52 DK board.

Using the above guide, this is what my revised overlay file looks like, but it still doesn't work:

&pinctrl {
    uart0_default: uart0_default {
        group1 {
            psels = <NRF_PSEL(UART_TX, 0, 6)>;
        };
        group2 {
            psels = <NRF_PSEL(UART_RX, 1, 8)>;
            bias-pull-up;
        };
    };
};
&uart0 {
    pinctrl-0 = <&uart0_default>;
    pinctrl-names = "default";
};

Is there an example somewhere of how to do this for a UART?

[droidecahedron]

So I did something similar to you using pinctrl with an nRF52833 board and an app.overlay, for uart1

&pinctrl {
	uart1_default: uart1_default {
	   group1 {
		  psels = <NRF_PSEL(UART_TX, 1, 2)>,
				  <NRF_PSEL(UART_RX, 1, 1)>;
	   };
	};
	/* required if CONFIG_PM_DEVICE=y */
	uart1_sleep: uart1_sleep {
	   group1 {
		  psels = <NRF_PSEL(UART_TX, 1, 2)>,
				  <NRF_PSEL(UART_RX, 1, 1)>;
		  low-power-enable;
	   };
	};
 };

 &uart1 {
   compatible = "nordic,nrf-uarte";
   current-speed = <19200>;
   status = "okay";
   pinctrl-0 = <&uart1_default>;
   pinctrl-1 = <&uart1_sleep>;
   pinctrl-names = "default", "sleep";
 };

This did work for me. i'd double check to make sure your project is using the overlay.

[Bret Foreman]

I got it to work as well. I changed the code for my nRF52832, which has just one UART:

&pinctrl {
	uart0_default: uart0_default {
	   group1 {
		  psels = <NRF_PSEL(UART_TX, 0, 11)>,
				  <NRF_PSEL(UART_RX, 0, 13)>;
	   };
	};
	/* required if CONFIG_PM_DEVICE=y */
	uart0_sleep: uart0_sleep {
	   group1 {
		  psels = <NRF_PSEL(UART_TX, 0, 11)>,
				  <NRF_PSEL(UART_RX, 0, 13)>;
		  low-power-enable;
	   };
	};
 };

 &uart0{

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

[Bret Foreman]

I tried the same overlay file with my 52810 and it didn't work (no TX data seen). The board I have the 52810 SoC on has TX on pin 6 and RX on pin 8. I suspect the issue here is that there does not exist a DK board for the 52810 so nobody at Nordic has tried the UART overlay. But somebody at Nordic probably has a custom board on which they can try a Zephyr build with this overlay.

&pinctrl {
	uart0_default: uart0_default {
	   group1 {
		  psels = <NRF_PSEL(UART_TX, 0, 6)>,
				  <NRF_PSEL(UART_RX, 0, 8)>;
	   };
	};
	/* required if CONFIG_PM_DEVICE=y */
	uart0_sleep: uart0_sleep {
	   group1 {
		  psels = <NRF_PSEL(UART_TX, 0, 6)>,
				  <NRF_PSEL(UART_RX, 0, 8)>;
		  low-power-enable;
	   };
	};
 };

 &uart0{

   compatible = "nordic,nrf-uarte";
   current-speed = <19200>;
   status = "okay";
   pinctrl-0 = <&uart0_default>;
   pinctrl-1 = <&uart0_sleep>;
   pinctrl-names = "default", "sleep";
 };

Here's the dts file that the "create a new board" wizard gave me:

// Copyright (c) 2023 Nordic Semiconductor ASA
// SPDX-License-Identifier: Apache-2.0

/dts-v1/;
#include <nordic/nrf52810_qfaa.dtsi>

/ {
	model = "nrf52810_cm";
	compatible = "nrf52810-cm";

	chosen {
		zephyr,sram = &sram0;
		zephyr,flash = &flash0;
		zephyr,code-partition = &slot0_partition;
	};
};

&flash0 {
	partitions {
		compatible = "fixed-partitions";
		#address-cells = <1>;
		#size-cells = <1>;

		boot_partition: partition@0 {
			label = "mcuboot";
			reg = <0x0 0xc000>;
		};
		slot0_partition: partition@c000 {
			label = "image-0";
			reg = <0xc000 0xa000>;
		};
		slot1_partition: partition@16000 {
			label = "image-1";
			reg = <0x16000 0xa000>;
		};
		scratch_partition: partition@20000 {
			label = "image-scratch";
			reg = <0x20000 0xa000>;
		};
		storage_partition: partition@2a000 {
			label = "storage";
			reg = <0x2a000 0x6000>;
		};
	};
};

Here's the uart0 binding in the nrf52810.dtsi file:

		uart0: uart@40002000 {
			/* uart can be either UART or UARTE, for the user to pick */
			/* compatible = "nordic,nrf-uarte" or "nordic,nrf-uart"; */
			compatible = "nordic,nrf-uarte";
			reg = <0x40002000 0x1000>;
			interrupts = <2 NRF_DEFAULT_IRQ_PRIORITY>;
			status = "disabled";
		};