NRF52 developing without using device trees

Question

I have recently picked up NRF52DK development board with NRF52832 https://www.nordicsemi.com/Products/Development-hardware/nrf52-dk

I have setup my development environment using VSCode NRF Connect extension.

I have been reading and learning a little bit about the NRF52 and realized that all the example projects use device trees.

For example, the code to toggle the GPIO:

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

#define LED0_NODE DT_ALIAS(led0) // LED0_NODE = led0 defined in the .dts file

int main(void)
{
    static const struct gpio_dt_spec led = GPIO_DT_SPEC_GET(LED0_NODE, gpios);

    if (!device_is_ready(led.port))
    {
        return;
    }
    int ret;

    ret = gpio_pin_configure_dt(&led, GPIO_OUTPUT_ACTIVE);
    if (ret < 0)
    {
        return;
    }

    printf("Hello World! %s\n", CONFIG_BOARD);
    k_sleep(K_MSEC(1000));
    printf("Bye World! %s\n", CONFIG_BOARD);

    while (1)
    {
        ret = gpio_pin_toggle_dt(&led);
        if (ret < 0)
        {
            return;
        }
        k_msleep(1000);
    }

    return 0;
}

I dont like device trees at all and I have a couple of questions:

1. wonder if there is a way to write code without using device trees at all? Could you please provide GPIO initialization and toggling example code without using device trees as I could not find a single example without device trees at all.

2. device tree relies on having the dts as described here:

What if I have my own custom nrf52 board and not a development board. Would I need to define my own device tree?

Answer 1

Although I would HIGHLY recommend learning and embracing the use of Zephyr and its devicetrees, You can look into these alternatives.

• You can use the framework Nordic had before adapting Zephyr and nRF Connect SDK, called the nRF5 SDK, combined with their nrfx drivers. This is, as far as I know, completely baremetal.
• You can work around the devicetrees while still making your application on Zephyr by using the nrfx drivers, because they are available in the nRF Connect SDK.
• You can write your own drivers or use 3rd party drivers for stuff.

Answer 2

Device trees are used by the Zephyr framework. Other frameworks don't use them.

Alternatives you could look into are:

• Mbed
• libopencm3
• Arduino framework with nRF52 Ardunio Core