k_sem_take failed UART interrupts Bluetooth

Question

Hello together,

Im currently doing my bachelor thesis and my task is to develop a user interface that can control a NRF52840 and write some parameters over UART.

Im able receive data that I sent from a python script, but if I want to start advertising it gets interrupted and the error message says: ASSERTION FAIL [error == 0] @ WEST_TOPDIR/zephyr/subsys/bluetooth/host/hci_core.c:305 k_sem_take failed with error -11

I already looked at everything I found relating to that error message. It seems like the UART, which is interrupt driven and fifo, interrupts the bluetooth hci core. I dont have any idea how to fix that, since Im not really experienced with zephyr or embedde programming.

In general: I need some code that reads the UART and does not interrupt the bluetooth functionality of the board. I didn't find a different UART solution that worked, it doesn't has to be interrupt driven or fifo! I hope some of you may help me :)

Thank you in advance for your answers!

The code is as following:

#include <zephyr.h>

#include <zephyr/types.h>

#include <sys/byteorder.h>

#include <stddef.h>

#include <errno.h>

#include <sys/printk.h>

#include <drivers/uart.h>

#include <stdio.h>

#include <string.h>

#include <bluetooth/bluetooth.h>

#include <bluetooth/hci.h>

#include <bluetooth/gatt.h>

#include <bluetooth/gatt_dm.h>

#include <bluetooth/conn.h>

#include <bluetooth/uuid.h>

static uint8_t uart_buf[1024];

static uint8_t mfg_data[] = {0x23,0x66,0x61,0x75,0x38,0xC5,0xAB,0xA9,0xF1,0x47,0x26,0xF7,0x44,0x73,0x2A,0xE2};

static const struct bt_data ad[] = {

BT_DATA(BT_DATA_UUID128_ALL, mfg_data, 16)

};

static void start_adv(void)

{

int err;

err = bt_le_adv_start(BT_LE_ADV_NCONN, ad, ARRAY_SIZE(ad) ,NULL, 0);

if (err) {

printk("Advertising failed to start (err %d)\n", err);

return;

}

printk("Advertising successfully started \n");

}

static void uart_cb(const struct device *x, void *user_data)

{

//printk("*");

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;

}

char cmp_str[] = "a";

printk("%s\n", uart_buf);

if(!strcmp(uart_buf,cmp_str)){

start_adv();

}

void main(void)

{

const struct device *uart = device_get_binding("UART_0");

//uart_irq_callback_set(uart, uart_cb);

int uart1_data = 0;

uart_irq_callback_user_data_set(uart, uart_cb, &uart1_data);

uart_irq_rx_enable(uart);

printk("UART loopback start!\n");

int err;

printk("Starting Scanner/Advertiser Demo\n");

/* Initialize the Bluetooth Subsystem */

err = bt_enable(NULL);

if (err) {

printk("Bluetooth init failed (err %d)\n", err);

return;

}

if (IS_ENABLED(CONFIG_SETTINGS)) {

settings_load();

}

printk("\nBluetooth initialized \n");

}

The .conf file is the following:

CONFIG_BT=y

CONFIG_BT_CENTRAL=y

CONFIG_BT_PERIPHERAL=y

CONFIG_BT_BROADCASTER=y

CONFIG_BT_OBSERVER=y

CONFIG_BT_DEBUG_LOG=y

CONFIG_BT_GATT_CLIENT=y

CONFIG_BT_GATT_DM=y

CONFIG_NVS=y

CONFIG_SETTINGS=y

CONFIG_UART_INTERRUPT_DRIVEN=y

CONFIG_SERIAL=y

CONFIG_UART_ASYNC_API=y

CONFIG_RTT_CONSOLE=y

CONFIG_USE_SEGGER_RTT=y

user111520 · Accepted Answer

Hello 
 Running BLE and UART in parallel is indeed a common issue, as BLE tasks need to run with high priority to comply with the strict timing requirements of the BLE specification, which can easily interfere with your UART operations. I would recommend that you use the UARTE peripheral, which has EasyDMA support that allows you to send/receive data directly through RAM while BLE uses the CPU: 
 https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf52840%2Fuarte.html 
 http://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrfx/drivers/uarte/driver.html 
 This should solve your problem, and even gives you something cool to write about in your thesis. 
 This other guy is technically correct that it's good practice to keep blocking code out of your callback functions, and I'd recommend reading up on semaphores as a way to signal between threads, but I believe UARTE is a better solution to your issue. 
 Best regards, 
 Einar

k_sem_take failed UART interrupts Bluetooth

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