Connect NRF52840 to QUECTEL BG96 to send AT Commands over Serial (RX,TX)

[BoReddy]

Hi,
I've been working with the nrf52840 DK which connects to a custom BLE sensor that we built.
The DK receives the sensor data over BLE. I'm using this sensor data to publish it to a private server.

I've connected the DK to a QUECTEL BG96 and want to send AT Commands to the BG96 over UART.

I'm fairly new to the nrf52840 and looking at the NRF connect SDK and the samples I'm able to send over the AT commands to the module over UART pins P0.06 and P0.08,

But I'm not able to receive anything back from the module to the DK. 

Can anyone please help me through this if there is any code using the NRF Connect SDK.

[Jared]

Hi,

What nRF Connect SDK version are you using? 

UART pins P0.06 and P0.08,

If you're using the development kit then P0.06 and P0.08 is already connected to the interface chip. Try switching pins to something else such as P0.02 and P0.03,

regards

Jared 

[BoReddy]

Hi, 
Thank you for such a quick reply
I'm using the nRF Connect SDK v2.5.0. 
I'm actually lost while trying to figure out the working.
Could you please help me with an example code if you have one.

[Jared]

Hi,

I can't write the code for you, it seems that you already have something. Maybe you can start with sharing that and I'll tell you where you can change the pins,

regards

Jared 

[BoReddy]

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

#include <string.h>

/* change this to any other UART peripheral if desired */
#define UART_DEVICE_NODE DT_CHOSEN(zephyr_shell_uart)

#define MSG_SIZE 32

/* queue to store up to 10 messages (aligned to 4-byte boundary) */
K_MSGQ_DEFINE(uart_msgq, MSG_SIZE, 10, 4);

static const struct device *const uart_dev = DEVICE_DT_GET(UART_DEVICE_NODE);

/* receive buffer used in UART ISR callback */
static char rx_buf[MSG_SIZE];
static int rx_buf_pos;

/*
 * Read characters from UART until line end is detected. Afterwards push the
 * data to the message queue.
 */
void serial_cb(const struct device *dev, void *user_data)
{
	uint8_t c;

	if (!uart_irq_update(uart_dev)) {
		return;
	}

	if (!uart_irq_rx_ready(uart_dev)) {
		return;
	}

	/* read until FIFO empty */
	while (uart_fifo_read(uart_dev, &c, 1) == 1) {
		if ((c == '\n' || c == '\r') && rx_buf_pos > 0) {
			/* terminate string */
			rx_buf[rx_buf_pos] = '\0';

			/* if queue is full, message is silently dropped */
			k_msgq_put(&uart_msgq, &rx_buf, K_NO_WAIT);

			/* reset the buffer (it was copied to the msgq) */
			rx_buf_pos = 0;
		} else if (rx_buf_pos < (sizeof(rx_buf) - 1)) {
			rx_buf[rx_buf_pos++] = c;
		}
		/* else: characters beyond buffer size are dropped */
	}
}

/*
 * Print a null-terminated string character by character to the UART interface
 */
void print_uart(char *buf)
{
	int msg_len = strlen(buf);

	for (int i = 0; i < msg_len; i++) {
		uart_poll_out(uart_dev, buf[i]);
	}
}

int main(void)
{
	char tx_buf[MSG_SIZE];

	if (!device_is_ready(uart_dev)) {
		// printk("UART device not found!");
		return 0;
	}

	/* configure interrupt and callback to receive data */
	int ret = uart_irq_callback_user_data_set(uart_dev, serial_cb, NULL);

	if (ret < 0) {
		if (ret == -ENOTSUP) {
			// printk("Interrupt-driven UART API support not enabled\n");
		} else if (ret == -ENOSYS) {
			// printk("UART device does not support interrupt-driven API\n");
		} else {
			// printk("Error setting UART callback: %d\n", ret);
		}
		return 0;
	}
	uart_irq_rx_enable(uart_dev);

	// print_uart("Hello! I'm your echo bot.\r\n");
	// print_uart("Tell me something and press enter:\r\n");

	/* indefinitely wait for input from the user */

	print_uart("AT\n");
	while (k_msgq_get(&uart_msgq, &tx_buf, K_FOREVER) == 0) {
		// print_uart("Echo: ");
		print_uart(tx_buf);
		print_uart("\n");
	}
	return 0;
}

I'm trying this code from the echo bot example. 

[Jared]

Hi,

The UART pins is set in the dts either through the overlay file, if overlay is not used then it's set in the board file. Try changing them and see if it resolves your issue.

regards

Jared