Issue about BLE_APP_UART and APP_TIMER

[davidz]

The SDK version is 16.0.0. I am using  NRF 52840 DK and testing the BLE data transmission with the example project BLE_APP_UART. I am using NRF Connect Desktop to communicate with the NRF52840 DK. The example is working well.

So I started modifying the BLE_APP_UART example and tried to simulate a sensor sending data to the NRF_Connect periodically. I used the APP Timer approach and when the timer causes an interrupt, then the program will call the timeout program and send data with ble_nus_data_send() command. When there is a BLE connection, then the program will start the timer with the function app_timer_start(). When the BLE connection is gone, then the program will stop the timer with the function app_timer_stop. The strange thing is that the program only work for the first time when the NRF connect Desktop connects to the NRF52840 DK via BLE. After the NRF connect desktop disconnects and reconnects, it connects for a brief time and then disconnects. The NRF52840 DK runs into error. What could be the reason? The following are the modified codes:

--------------------------------------

#define SENSOR_MEAS_INTERVAL APP_TIMER_TICKS(300) /* sensor interval */
APP_TIMER_DEF(m_sensor_timer_id); /**< sensor timer id. */

// Sensor timer time out handler

static void sensor_meas_timeout_handler(void * p_context)
{
UNUSED_PARAMETER(p_context);

static uint8_t data_array[BLE_NUS_MAX_DATA_LEN];
uint32_t err_code;
uint16_t length = 4;
static int i=0;
if(m_conn_handle!=BLE_CONN_HANDLE_INVALID)
{
i++;
data_array[0]=i;
data_array[1]=i+1;
data_array[2]=i+2;
data_array[3]=i+3;
err_code = ble_nus_data_send(&m_nus, data_array, &length, m_conn_handle);
if ((err_code != NRF_ERROR_INVALID_STATE) &&
(err_code != NRF_ERROR_RESOURCES) &&
(err_code != NRF_ERROR_NOT_FOUND))
{
APP_ERROR_CHECK(err_code);
// NRF_LOG_INFO("Error code is %d\r\n",err_code);
}
else NRF_LOG_INFO("Sending out data %dth time. connection handle %d\r\n",i,m_conn_handle);

}
}

// Timer initialization

static void timers_init(void)
{
ret_code_t err_code = app_timer_init();
APP_ERROR_CHECK(err_code);

// Create timers.
err_code = app_timer_create(&m_sensor_timer_id,
APP_TIMER_MODE_REPEATED,
sensor_meas_timeout_handler);
APP_ERROR_CHECK(err_code);

}

static void application_timers_start(void)
{
ret_code_t err_code;

// Start application timers.
err_code = app_timer_start(m_sensor_timer_id, SENSOR_MEAS_INTERVAL, NULL);
APP_ERROR_CHECK(err_code);

}

static void application_timers_stop(void)
{
ret_code_t err_code;
err_code=app_timer_stop(m_sensor_timer_id);
APP_ERROR_CHECK(err_code);
}

static void ble_evt_handler(ble_evt_t const * p_ble_evt, void * p_context)
{
uint32_t err_code;

switch (p_ble_evt->header.evt_id)
{
case BLE_GAP_EVT_CONNECTED:
NRF_LOG_INFO("Connected");
printf("\r\nconnected.\r\n");
err_code = bsp_indication_set(BSP_INDICATE_CONNECTED);
APP_ERROR_CHECK(err_code);
m_conn_handle = p_ble_evt->evt.gap_evt.conn_handle;
err_code = nrf_ble_qwr_conn_handle_assign(&m_qwr, m_conn_handle);
APP_ERROR_CHECK(err_code);
nrf_delay_ms(200);
application_timers_start();

break;

case BLE_GAP_EVT_DISCONNECTED:
NRF_LOG_INFO("Disconnected\r\n");
// LED indication will be changed when advertising starts.
m_conn_handle = BLE_CONN_HANDLE_INVALID;

application_timers_stop();

break;

.... 

}

[Sigurd]

Hi,

davidz said:

After the NRF connect desktop disconnects and reconnects, it connects for a brief time and then disconnects. The NRF52840 DK runs into error.

What disconnect reason did you get? 

What error did you run into on the nRF52840 DK?

[davidz]

The NRF Connect desktop shows the error "Disconnected from device E4:A6:2D:DE:55:B3, reason: BLE_HCI_CONNECTION_TIMEOUT".  The nRF52840 DK shows the error "void app_error_fault_handler(unsigned int id=0x00004001, unsigned int pc=0x0002fb6b, unsinged int info=0x200:0x00028D30", and "void app_error_handler(unsigned int error_code=0x00000000, unsigned int line_num=0x20002bec, const unint8_t*|0x00028BFA"

[Sigurd]

Try to set your project to Debug configuration, if you are using SES, you can do it like this:

In sdk_config.h, make sure that these defines have these values:

NRF_FPRINTF_FLAG_AUTOMATIC_CR_ON_LF_ENABLED 0
NRF_LOG_BACKEND_RTT_ENABLED 1
NRF_LOG_ENABLED 1

In app_error_weak.c,

add NRF_LOG_FLUSH(); above NRF_BREAKPOINT_COND;

The error-code, filename and line-number should then be printed in the SES Debug Terminal.

[davidz]

Thanks. Here is the output "<error> app: ERROR 13313 [Unknown error code] at D:\nrf5sdk1600\workspace\test0\ble_app_uart\main.c:126
PC at: 0x0002FB77".  It happened at the sensor_meas_timeout_handler(). Line 126 is where the program stopped. I actually used "NRF_LOG_INFO("Error code is %d\r\n",err_code);" to find out the error code before. I have a question: does ble_nus_data_send() function need to wait for something else after the BLE connection is re-established? It looks like the ble_nus_data_send() function caused the problem after the re-connection. 

static void sensor_meas_timeout_handler(void * p_context)
{
UNUSED_PARAMETER(p_context);

static uint8_t data_array[BLE_NUS_MAX_DATA_LEN];
uint32_t err_code;
uint16_t length = 4;
static int i=0;
if(m_conn_handle!=BLE_CONN_HANDLE_INVALID)
{
i++;
data_array[0]=i;
data_array[1]=i+1;
data_array[2]=i+2;
data_array[3]=i+3;
err_code = ble_nus_data_send(&m_nus, data_array, &length, m_conn_handle);
if ((err_code != NRF_ERROR_INVALID_STATE) &&
(err_code != NRF_ERROR_RESOURCES) &&
(err_code != NRF_ERROR_NOT_FOUND))
{
APP_ERROR_CHECK(err_code);    // Line 126
// NRF_LOG_INFO("Error code is %d\r\n",err_code);
}
else NRF_LOG_INFO("Sending out data %dth time. connection handle %d\r\n",i,m_conn_handle);

}
}

[Sigurd]

davidz said:

ERROR 13313

 13313 is the same as BLE_ERROR_GATTS_SYS_ATTR_MISSING. You can read about this error code e.g. in this post

[davidz]

Thank you Sigurd. I have solved the problem by moving the sensor data transmit to the main loop. It seems that the APP_timer interrupt does not work well with my sensor, which uses SPI bus to interface with the nrf52840.