dts

/*
 * Copyright (c) 2020 The ZMK Contributors
 * SPDX-License-Identifier: MIT
 */

/dts-v1/;
#include <nordic/nrf52840_qiaa.dtsi>

/ {
	model = "nRF52840-MDK Dongle Dev Kit";
	compatible = "makerdiary,nrf52840_mdk_dongle";

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

	leds {
		compatible = "gpio-leds";
		led_green: led_green {
			gpios = <&gpio0 22 GPIO_ACTIVE_LOW>;
			label = "Green LED";
		};
		led_red: led_red {
			gpios = <&gpio0 23 GPIO_ACTIVE_LOW>;
			label = "Red LED";
		};
		led_blue: led_blue {
			gpios = <&gpio0 24 GPIO_ACTIVE_LOW>;
			label = "Blue LED";
		};
	};

	pwmleds {
		compatible = "pwm-leds";
		pwm_led_green: pwm_led_green {
			pwms = <&pwm0 22>;
			label = "Green PWM LED";
		};
		pwm_led_red: pwm_led_red {
			pwms = <&pwm0 23>;
			label = "Red PWM LED";
		};
		pwm_led_blue: pwm_led_blue {
			pwms = <&pwm0 24>;
			label = "Blue PWM LED";
		};
	};

	buttons {
		compatible = "gpio-keys";
		button0: button0 {
			gpios = <&gpio0 18 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;
			label = "Push button switch 0";
		};
	};

	/* These aliases are provided for compatibility with samples */
	aliases {
		led-green = &led_green;
		led-red   = &led_red;
		led-blue  = &led_blue;
		pwm-led-green = &pwm_led_green;
		pwm-led-red = &pwm_led_red;
		pwm-led-blue = &pwm_led_blue;
	};
};

&adc {
	status = "okay";
};

&gpiote {
	status = "okay";
};

&gpio0 {
	status = "okay";
};

&gpio1 {
	status = "okay";
};

&flash0 {
	/*
	 * For more information, see:
	 * http://docs.zephyrproject.org/latest/devices/dts/flash_partitions.html
	 */
	partitions {
		compatible = "fixed-partitions";
		#address-cells = <1>;
		#size-cells = <1>;

		sd_partition: partition@0 {
			label = "mbr";
			reg = <0x00000000 0x00001000>;
		};
		code_partition: partition@1000 {
			label = "code_partition";
			reg = <0x00001000 0x000d3000>;
		};

		/*
		 * The flash starting at 0x000d4000 and ending at
		 * 0x000f3fff is reserved for use by the application.
		 */

		/*
		 * Storage partition will be used by FCB/LittleFS/NVS
		 * if enabled.
		 */
		storage_partition: partition@d4000 {
			label = "storage";
			reg = <0x000d4000 0x00020000>;
		};

		boot_partition: partition@f4000 {
			label = "adafruit_boot";
			reg = <0x000f4000 0x0000c000>;
		};
	};
};

main.c

/*
 * Copyright (c) 2016 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <zephyr.h>
#include <device.h>
#include <devicetree.h>
#include <drivers/gpio.h>

/* 1000 msec = 1 sec */
#define SLEEP_TIME_MS   1000

/* The devicetree node identifier for the "led0" alias. */
#define LED0_NODE DT_ALIAS(led-blue)

#if DT_NODE_HAS_STATUS(LED0_NODE, okay)
#define LED0	DT_GPIO_LABEL(LED0_NODE, gpios)
#define PIN	DT_GPIO_PIN(LED0_NODE, gpios)
#define FLAGS	DT_GPIO_FLAGS(LED0_NODE, gpios)
#else
/* A build error here means your board isn't set up to blink an LED. */
#error "Unsupported board: led devicetree alias is not defined"
#define LED0	""
#define PIN	0
#define FLAGS	0
#endif

void main(void)
{
	const struct device *dev;
	bool led_is_on = true;
	int ret;

	dev = device_get_binding(LED0);
	if (dev == NULL) {
		return;
	}

	ret = gpio_pin_configure(dev, PIN, GPIO_OUTPUT | FLAGS);
	if (ret < 0) {
		return;
	}

	while (1) {
		gpio_pin_set(dev, PIN, (int)true);
		led_is_on = !led_is_on;
		k_msleep(SLEEP_TIME_MS);
	}
}