basic UART sample for nRF Connect SDK

Question

Hi, 
 I am struggling to find a basic sample for UART communication in NCS. As an experienced Nrf5 SDK programmer, I find it very hard to convert my firmware to nRF Connect and Zephyr. There is no small and simple example in the NCS, the Zephyr website just lists of bunch of declarations, and searching the internet and devzone yields a bewildering amount of different solutions, dead links, with or without FIFO, UART or UARTE, incomprehensible config settings and lots of code that is documented as "not running", "unreliable" etc. I just need 2 UARTs to transmit commands to sensors and receive data from them, preferably under interrupt. 
 thx, 
 Henk

Stian Røed Hafskjold · Accepted Answer

Hi, I'm very sorry for keeping you waiting so long. Here is a basic UART loopback sample:

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

static uint8_t uart_buf[1024];

void uart_cb(const struct device *x, void *user_data)
{
	uart_irq_update(x);
	int data_length = 0;

	if (uart_irq_rx_ready(x)) {
		data_length = uart_fifo_read(x, uart_buf, sizeof(uart_buf));
		uart_buf[data_length] = 0;
	}
    uart_fifo_fill(x, uart_buf, data_length);
}

void main(void)
{

    const struct device *uart = device_get_binding("UART_2"); // Use UART2 for the loopback
	uart_irq_callback_set(uart, uart_cb);
	uart_irq_rx_enable(uart);
	uart_fifo_fill(uart, "UART loopback start!\r\n", 22);     // Output on UART2
	printk("UART loopback start!\n");                         // Output on UART0, which is default for logging
	while (1) {
		k_cpu_idle();
	}
}

In order to configure UART2, you can use an overlay file.

&uart2 {
	status = "okay";
	current-speed = <115200>;
	tx-pin = <31>;
	rx-pin = <30>;
};

The standard device configuration is located in "zephyr/boards/arm/nrf9160dk_nrf9160/nrf9160dk_nrf9160_common.dts", so the overlay file will change the uart2 entry.

EDIT: About the non standard baudrate, that's unfortunate, and the formula should be in the PS. I will follow up on that

Henk Pragt · Answer

Hi Stian, 
 after updating the toolchain to 1.6.1 the IDE got so fucked up I had to uninstall the whole set. Basic problem seemed to be that the compiler kept searching and finding files in other places then where they really were. Uninstalling nRF Connect did nog work either: I had to make a clean Windows install to get the IDE running again. GRUMBLE!!! Anyway, after all these hours of work, the problem with the UART flag has disappeared, so I consider this issue closed. 
 It is also closed because we have decided to give up on nRF Connect that, in our humble opinion, sucks big time. We are going to redesign the board with TI or Microchip processors so that in the future we will not be forced to throw away all our development just because Nordic has come up with yet another fancy IDE. 
 Thanks anyway for your help, 
 Henk

basic UART sample for nRF Connect SDK

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