SDKv1.5.1 Blinky example with UART

Question

Dear Nordic support,

i'm evaluating the Nordic nRF52840_Dongle with the SDK 1.5.1, inlucing Zephyr etc. I could successfully compile and load the Blinky-example (..\ncs\v1.5.1\zephyr\samples\basic\blinky\build_nrf52840dongle_nrf52840) and manipulated it.

Now i am really struggeling to add a UART (a real UART, no CDC-USB) connection to the dongle. I promise i've read so many documentation (Zephyr, K-Config, Device-Tree, Nordic-SDK...). But i can't find answers...

---

1.) On which pins at the dongle, can i map the UART RX and TX pins?! Normally on a microcontroller i have a bunch of options, in the Nordic docs it looks like i can map them anywhere, can I? Precisely this configuration is feasible

zephyr.dts --

...

        uart0: uart@40002000 {
           reg = < 0x40002000 0x1000 >;
           interrupts = < 0x2 0x1 >;
           status = "okay";
           label = "UART_0";
           compatible = "nordic,nrf-uarte";
           current-speed = < 0x1c200 >;
           tx-pin = < 0x1f >;
           rx-pin = < 0x1d >;
           rts-pin = < 0x00 >;
           cts-pin = < 0x00 >;

...

2.) In the docs and even in the video the pins are numbered like "30", "31" and so on. But the in ref-maunal and the schematic there ist port number AND the pin number , e.g 0.12, 1.15, how do i address 1.15, when i want to used it as a UART pin in the config overlay file?

3.) In the picture below, there is my code of the blinky example, including my attemps of using the UART via the zephyr-API. The Problem is, that the "device_get_binding" - function returns a NULL-pointer. I have no idea why.

Thanks a lot.

Sören

Einar Thorsrud · Accepted Answer

Hi,

I have attached a modified project that is working here. This works both on the DK and dongle. I tested with the default board file (zephyr\boards\arm\nrf52840dongle_nrf52840\nrf52840dongle_nrf52840.dts) with the Tx pin being P0.20, but using another pin should be no problem.

Code:

Fullscreen 0636.main.c Download

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


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

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

#define LED0 DT_GPIO_LABEL(LED0_NODE, gpios)
#define PIN0 DT_GPIO_PIN(LED0_NODE, gpios)
#define FLAGS0 DT_GPIO_FLAGS(LED0_NODE, gpios)

#define LED1_NODE DT_ALIAS(led1)
#define LED1 DT_GPIO_LABEL(LED1_NODE, gpios)
#define PIN1 DT_GPIO_PIN(LED1_NODE, gpios)
#define FLAGS1 DT_GPIO_FLAGS(LED1_NODE, gpios)

#define UART0_NODE DT_NODELABEL(uart0)
#define UART0 DT_LABEL(UART0_NODE)
#define UART_LABEL		DT_LABEL(DT_NODELABEL(uart0))


void main(void)
{
	const struct device *green_led_handle;
	const struct device *red_led_handle;
	const struct device *uart_0_handle;
	bool led_is_on = true;
	volatile int ret;
	const uint8_t message[] = "Hello World! \n\r";

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

	red_led_handle = device_get_binding(LED1);
	if (red_led_handle == NULL)
	{
		return;
	}

	uart_0_handle = device_get_binding(UART_LABEL);

	if (!uart_0_handle) {
		return;
	}

	ret = gpio_pin_configure(green_led_handle, PIN0, GPIO_OUTPUT_ACTIVE | FLAGS0);
	if (ret < 0)
	{
		return;
	}

	ret = gpio_pin_configure(red_led_handle, PIN1, GPIO_OUTPUT_ACTIVE | FLAGS1);
	if (ret < 0)
	{
		return;
	}

	while (1)
	{
		gpio_pin_set(green_led_handle, PIN0, (int)led_is_on);
		led_is_on = !led_is_on;
		gpio_pin_set(red_led_handle, PIN1, (int)led_is_on);
		ret = uart_tx(uart_0_handle, message, sizeof(message), 100);
		k_msleep(SLEEP_TIME_MS);
	}
}

Config:

8015.prj.conf

Logic analyzer plot:

SoerenBirth · Answer

Thanks Einar, 
 
 The key was just one line in the prj.conf file 
 after i deleted CONFIG_UART_INTERRUPT_DRIVEN it immediately worked! The next question will be, how do i get the interrupt based transfer started. Best regards 
 
 S&ouml;ren

SDKv1.5.1 Blinky example with UART

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