custom service discovery in BLE_Central

[Prajakta]

Hi,

I want to develop central code to discover services of 3rd party device and to discover their services and read/write characteristics.

As seen many examples from SDK below is my understanding:

1. Include db_discovery_init() 

2. call ble_db_discovery_start() on BLE_GAP_EVT_CONNECTED event in ble_evt_handler().

3. While initlaizing need to init service which is going to discover as below:

like in BLE_blinky example,includes ble_lbs service as below :

static void db_disc_handler(ble_db_discovery_evt_t * p_evt)
{
    ble_lbs_on_db_disc_evt(&m_ble_lbs_c, p_evt);
}

So my question is:

While db_discovery_init() which service should initialize in db_disc_handler() for custom service discovery? when we don't know which service is advertising by other device.

And

How to discover the services and print this and its characteristics on console. Same as we can see in nrf Connect app. Please suggest or share suitable code except BLE_UART example code.

Please help me on this asap.

Regards,

Prajakta

[Hung Bui]

Hi Prajakta, 

The db_disc_handler() is where you handle the events from the db discovery library, for example when the discovery is complete, or when the service is not found. 

However, the db discovery module was not really made for generic service discovery. This means usually you need to provide the service UUID(s) you want to discover to the module before it started. 

To be able to do generic discovery (where you discovery all UUIDs) you would need to modify it a little bit. There is some discussion here. Please have a look and let me know if you have any question. 

[Prajakta]

I am using BLE_Blinky application, in that after connection done, in ble_evt_handler (),handle_assign function is there, then they called ble_db_discovery_start.

As per this discussion, need to call sd_ble_gattc_primary_services_discover.
1.So where I can call this function with parameters?

And

2. Can you help me for flow for service discovery from start(init) to end in example code.I am able to do it for ble_lbs_c service(blinky application). I am not getting how to replicate it for primary service discovery.

[Hung Bui]

You can start with calling sd_ble_gattc_primary_services_discover() , use connection handle of your current connection, start_handle of 1 and p_srvc_uuid = NULL. It will discover any service starting from handle 1. You call this function after BLE_GAP_EVT_CONNECTED event. 

Then you wait for BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP event inside ble_evt_handler() , when you receive this event, you can check how many service discovered and which handle range it covers inside the ble_gattc_service_t services[1]; in ble_gattc_evt_prim_srvc_disc_rsp_t struct of the event. 

Then you can continue to call sd_ble_gattc_primary_services_discover() with the last handle until you receive ATTRIBUTE_NOT_FOUND in the next correspondent event . 

[Prajakta]

After connection its not getting anything.
logs as below:

<info> app: Press button 4 to start scanning.
<info> app: Start scanning.
<info> app: Start scanning.
<info> app: Connected.

[Prajakta]

Code changes done in main.c as follows:

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

    // For readability.
    ble_gap_evt_t const * p_gap_evt = &p_ble_evt->evt.gap_evt;
   // ble_uuid128_t base_uuid = {UUID_BASE};
   //  uint8_t uuidType = 2;
    switch (p_ble_evt->header.evt_id)
    {
        // Upon connection, check which peripheral has connected (HR or RSC), initiate DB
        // discovery, update LEDs status and resume scanning if necessary. */
        case BLE_GAP_EVT_CONNECTED:
            NRF_LOG_INFO("Connected.");
            err_code = sd_ble_gattc_primary_services_discover(p_gap_evt->conn_handle,
                                                                    SRV_DISC_START_HANDLE,0);
    }
    break;
}

[Hung Bui]

Please check the return code of err_code , make sure it's = NRF_SUCCESS

Then please check for BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP event, same way as BLE_GAP_EVT_CONNECTED. 

May I ask if you have used Nordic chip in other projects before ? Or it's your first time working with Nordic chip ? 

[Prajakta]

Yes it gives NRF_SUCCESS.

Its first time i am working with nordic chip and also on BLE.

also i have checked in BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP event.
it doesnt come in that event. Also i have checked with 2-3 devices which have custom service.

[Hung Bui]

Could you please post your code where and how you check for BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP ? 

[Prajakta]

Fullscreen 5554.main.c Download

/**
 * Copyright (c) 2014 - 2018, Nordic Semiconductor ASA
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 *
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 *
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
/**
 * @brief BLE LED Button Service central and client application main file.
 *
 * This file contains the source code for a sample client application using the LED Button service.
 */

#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include "nrf_sdh.h"
#include "nrf_sdh_ble.h"
#include "nrf_sdh_soc.h"
#include "nrf_pwr_mgmt.h"
#include "app_timer.h"
#include "boards.h"
#include "bsp.h"
#include "bsp_btn_ble.h"
#include "ble.h"
#include "ble_hci.h"
#include "ble_advertising.h"
#include "ble_conn_params.h"
#include "ble_db_discovery.h"
#include "ble_lbs_c.h"
#include "nrf_ble_gatt.h"
#include "nrf_ble_scan.h"

#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"


#define CENTRAL_SCANNING_LED            BSP_BOARD_LED_0                     /**< Scanning LED will be on when the device is scanning. */
#define CENTRAL_CONNECTED_LED           BSP_BOARD_LED_1                     /**< Connected LED will be on when the device is connected. */
#define LEDBUTTON_LED                   BSP_BOARD_LED_2                     /**< LED to indicate a change of state of the the Button characteristic on the peer. */

#define SCAN_INTERVAL                   0x00A0                              /**< Determines scan interval in units of 0.625 millisecond. */
#define SCAN_WINDOW                     0x0050                              /**< Determines scan window in units of 0.625 millisecond. */
#define SCAN_DURATION                   0x0000                              /**< Timout when scanning. 0x0000 disables timeout. */

#define MIN_CONNECTION_INTERVAL         MSEC_TO_UNITS(7.5, UNIT_1_25_MS)    /**< Determines minimum connection interval in milliseconds. */
#define MAX_CONNECTION_INTERVAL         MSEC_TO_UNITS(30, UNIT_1_25_MS)     /**< Determines maximum connection interval in milliseconds. */
#define SLAVE_LATENCY                   0                                   /**< Determines slave latency in terms of connection events. */
#define SUPERVISION_TIMEOUT             MSEC_TO_UNITS(4000, UNIT_10_MS)     /**< Determines supervision time-out in units of 10 milliseconds. */

#define LEDBUTTON_BUTTON_PIN            BSP_BUTTON_0                        /**< Button that will write to the LED characteristic of the peer */
#define SCANNING_BUTTON      	  	  BSP_BUTTON_3                                    /**< abort any connections if any and start advertising/scan , non connectable scannable packets */

#define BUTTON_DETECTION_DELAY          APP_TIMER_TICKS(50)                 /**< Delay from a GPIOTE event until a button is reported as pushed (in number of timer ticks). */

#define APP_BLE_CONN_CFG_TAG            1                                   /**< A tag identifying the SoftDevice BLE configuration. */
#define APP_BLE_OBSERVER_PRIO           3                                   /**< Application's BLE observer priority. You shouldn't need to modify this value. */

NRF_BLE_SCAN_DEF(m_scan);                                       /**< Scanning module instance. */
BLE_LBS_C_DEF(m_ble_lbs_c);                                     /**< Main structure used by the LBS client module. */
NRF_BLE_GATT_DEF(m_gatt);                                       /**< GATT module instance. */
BLE_DB_DISCOVERY_DEF(m_db_disc);                                /**< DB discovery module instance. */
#define SRV_DISC_START_HANDLE  0x0001                    /**< The start handle value used during service discovery. */

#define UUID_BASE        {0x23, 0xD1, 0xBC, 0xEA, 0x5F, 0x78, 0x23, 0x15, \
                              0xDE, 0xEF, 0x12, 0x12, 0x00, 0x00, 0x00, 0x00}
static char const m_target_periph_name[] = "Nordic";     /**< Name of the device we try to connect to. This name is searched in the scan report data*/


/**@brief Function to handle asserts in the SoftDevice.
 *
 * @details This function will be called in case of an assert in the SoftDevice.
 *
 * @warning This handler is an example only and does not fit a final product. You need to analyze
 *          how your product is supposed to react in case of Assert.
 * @warning On assert from the SoftDevice, the system can only recover on reset.
 *
 * @param[in] line_num     Line number of the failing ASSERT call.
 * @param[in] p_file_name  File name of the failing ASSERT call.
 */
void assert_nrf_callback(uint16_t line_num, const uint8_t * p_file_name)
{
    app_error_handler(0xDEADBEEF, line_num, p_file_name);
}


/**@brief Function for the LEDs initialization.
 *
 * @details Initializes all LEDs used by the application.
 */
static void leds_init(void)
{
    bsp_board_init(BSP_INIT_LEDS);
}

/**@brief Function for enabling button input.
 */
static void buttons_enable(void)
{
    ret_code_t err_code = app_button_enable();
    APP_ERROR_CHECK(err_code);
}

/**@brief Function to start scanning.
 */
static void scan_start(void)
{
    ret_code_t err_code;
    NRF_LOG_INFO("Start scanning.");

    err_code = nrf_ble_scan_start(&m_scan);
    APP_ERROR_CHECK(err_code);

    bsp_board_led_off(CENTRAL_CONNECTED_LED);
    bsp_board_led_on(CENTRAL_SCANNING_LED);
}


/**@brief Handles events coming from the LED Button central module.
 */
/*
static void lbs_c_evt_handler(ble_lbs_c_t * p_lbs_c, ble_lbs_c_evt_t * p_lbs_c_evt)
{
    switch (p_lbs_c_evt->evt_type)
    {
        case BLE_LBS_C_EVT_DISCOVERY_COMPLETE:
        {
            ret_code_t err_code;

            err_code = ble_lbs_c_handles_assign(&m_ble_lbs_c,
                                                p_lbs_c_evt->conn_handle,
                                                &p_lbs_c_evt->params.peer_db);
            NRF_LOG_INFO("LED Button service discovered on conn_handle 0x%x.", p_lbs_c_evt->conn_handle);

            err_code = app_button_enable();
            APP_ERROR_CHECK(err_code);

            // LED Button service discovered. Enable notification of Button.
            err_code = ble_lbs_c_button_notif_enable(p_lbs_c);
            APP_ERROR_CHECK(err_code);
        } break; // BLE_LBS_C_EVT_DISCOVERY_COMPLETE

        case BLE_LBS_C_EVT_BUTTON_NOTIFICATION:
        {
            NRF_LOG_INFO("Button state changed on peer to 0x%x.", p_lbs_c_evt->params.button.button_state);
            if (p_lbs_c_evt->params.button.button_state)
            {
                bsp_board_led_on(LEDBUTTON_LED);
            }
            else
            {
                bsp_board_led_off(LEDBUTTON_LED);
            }
        } break; // BLE_LBS_C_EVT_BUTTON_NOTIFICATION

        default:
            // No implementation needed.
            break;
    }
}
*/

/**@brief Function for handling BLE events.
 *
 * @param[in]   p_ble_evt   Bluetooth stack event.
 * @param[in]   p_context   Unused.
 */
static void ble_evt_handler(ble_evt_t const * p_ble_evt, void * p_context)
{
    ret_code_t err_code;

    // For readability.
    ble_gap_evt_t const * p_gap_evt = &p_ble_evt->evt.gap_evt;
    ble_db_discovery_t * p_db_discovery = (ble_db_discovery_t *)p_context;
   // ble_uuid128_t base_uuid = {UUID_BASE};
   //  uint8_t uuidType = 2;
    switch (p_ble_evt->header.evt_id)
    {
        // Upon connection, check which peripheral has connected (HR or RSC), initiate DB
        // discovery, update LEDs status and resume scanning if necessary. */
        case BLE_GAP_EVT_CONNECTED:
            NRF_LOG_INFO("Connected.");
          //  err_code = ble_db_discovery_start(&m_db_disc, p_gap_evt->conn_handle);
           //            APP_ERROR_CHECK(err_code);

            //discovery_start(ble_db_discovery_t * const p_db_discovery, uint16_t conn_handle);
            NRF_LOG_INFO("Before discovery");
            err_code = sd_ble_gattc_primary_services_discover(p_gap_evt->conn_handle,
                                                                    SRV_DISC_START_HANDLE,NULL);
            APP_ERROR_CHECK(err_code);
            if (err_code == NRF_SUCCESS)
		   {
            	NRF_LOG_INFO("Discovery done successfully");
		   }
            else
            {
            	NRF_LOG_INFO("Failed Discovery");
            }
            // peripherals to connect to.
            bsp_board_led_on(CENTRAL_CONNECTED_LED);
            bsp_board_led_off(CENTRAL_SCANNING_LED);
        break;

        // Upon disconnection, reset the connection handle of the peer which disconnected, update
        // the LEDs status and start scanning again.
        case BLE_GAP_EVT_DISCONNECTED:
        {
            NRF_LOG_INFO("Disconnected.");
            scan_start();
        } break;

        case BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP:
                	NRF_LOG_DEBUG("Found service");
                    on_primary_srv_discovery_rsp(p_db_discovery, &(p_ble_evt->evt.gattc_evt));
        break;


        case BLE_GAP_EVT_TIMEOUT:
        {
            // We have not specified a timeout for scanning, so only connection attemps can timeout.
            if (p_gap_evt->params.timeout.src == BLE_GAP_TIMEOUT_SRC_CONN)
            {
                NRF_LOG_DEBUG("Connection request timed out.");
            }
        } break;

        case BLE_GAP_EVT_CONN_PARAM_UPDATE_REQUEST:
        {
            // Accept parameters requested by peer.
            err_code = sd_ble_gap_conn_param_update(p_gap_evt->conn_handle,
                                        &p_gap_evt->params.conn_param_update_request.conn_params);
            APP_ERROR_CHECK(err_code);
        } break;

        case BLE_GAP_EVT_PHY_UPDATE_REQUEST:
        {
            NRF_LOG_DEBUG("PHY update request.");
            ble_gap_phys_t const phys =
            {
                .rx_phys = BLE_GAP_PHY_AUTO,
                .tx_phys = BLE_GAP_PHY_AUTO,
            };
            err_code = sd_ble_gap_phy_update(p_ble_evt->evt.gap_evt.conn_handle, &phys);
            APP_ERROR_CHECK(err_code);
        } break;

        case BLE_GATTC_EVT_TIMEOUT:
        {
            // Disconnect on GATT Client timeout event.
            NRF_LOG_DEBUG("GATT Client Timeout.");
            err_code = sd_ble_gap_disconnect(p_ble_evt->evt.gattc_evt.conn_handle,
                                             BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
            APP_ERROR_CHECK(err_code);
        } break;

        case BLE_GATTS_EVT_TIMEOUT:
        {
            // Disconnect on GATT Server timeout event.
            NRF_LOG_DEBUG("GATT Server Timeout.");
            err_code = sd_ble_gap_disconnect(p_ble_evt->evt.gatts_evt.conn_handle,
                                             BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
            APP_ERROR_CHECK(err_code);
        } break;

        default:
            // No implementation needed.
            break;
    }
}


/**@brief LED Button client initialization.
 */
/*
static void lbs_c_init(void)
{
    ret_code_t       err_code;
    ble_lbs_c_init_t lbs_c_init_obj;

    lbs_c_init_obj.evt_handler = lbs_c_evt_handler;

    err_code = ble_lbs_c_init(&m_ble_lbs_c, &lbs_c_init_obj);
    APP_ERROR_CHECK(err_code);
}
*/

/**@brief Function for initializing the BLE stack.
 *
 * @details Initializes the SoftDevice and the BLE event interrupts.
 */
static void ble_stack_init(void)
{
    ret_code_t err_code;

    err_code = nrf_sdh_enable_request();
    APP_ERROR_CHECK(err_code);

    // Configure the BLE stack using the default settings.
    // Fetch the start address of the application RAM.
    uint32_t ram_start = 0;
    err_code = nrf_sdh_ble_default_cfg_set(APP_BLE_CONN_CFG_TAG, &ram_start);
    APP_ERROR_CHECK(err_code);

    // Enable BLE stack.
    err_code = nrf_sdh_ble_enable(&ram_start);
    APP_ERROR_CHECK(err_code);

    // Register a handler for BLE events.
    NRF_SDH_BLE_OBSERVER(m_ble_observer, APP_BLE_OBSERVER_PRIO, ble_evt_handler, NULL);
}


/**@brief Function for handling events from the button handler module.
 *
 * @param[in] pin_no        The pin that the event applies to.
 * @param[in] button_action The button action (press/release).
 */
static void button_event_handler(uint8_t pin_no, uint8_t button_action)
{
    ret_code_t err_code;

    switch (pin_no)
    {
        case LEDBUTTON_BUTTON_PIN:
            err_code = ble_lbs_led_status_send(&m_ble_lbs_c, button_action);
            if (err_code != NRF_SUCCESS &&
                err_code != BLE_ERROR_INVALID_CONN_HANDLE &&
                err_code != NRF_ERROR_INVALID_STATE)
            {
                APP_ERROR_CHECK(err_code);
            }
            if (err_code == NRF_SUCCESS)
            {
                NRF_LOG_INFO("LBS write LED state %d", button_action);
            }
            break;
        case SCANNING_BUTTON:
            scan_start();
            break;
        default:
            APP_ERROR_HANDLER(pin_no);
            break;
    }
}


/**@brief Function for handling Scaning events.
 *
 * @param[in]   p_scan_evt   Scanning event.
 */
static void scan_evt_handler(scan_evt_t const * p_scan_evt)
{
    ret_code_t err_code;

    switch(p_scan_evt->scan_evt_id)
    {
        case NRF_BLE_SCAN_EVT_CONNECTING_ERROR:
            err_code = p_scan_evt->params.connecting_err.err_code;
            APP_ERROR_CHECK(err_code);
            break;
        default:
          break;
    }
}



/**@brief Function for initializing the button handler module.
 */
static void buttons_init(void)
{
    ret_code_t err_code;

    //The array must be static because a pointer to it will be saved in the button handler module.
    static app_button_cfg_t buttons[] =
    {
        {LEDBUTTON_BUTTON_PIN, false, BUTTON_PULL, button_event_handler},
		{SCANNING_BUTTON, false, BUTTON_PULL, button_event_handler}
    };

    err_code = app_button_init(buttons, ARRAY_SIZE(buttons),
                               BUTTON_DETECTION_DELAY);
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for handling database discovery events.
 *
 * @details This function is callback function to handle events from the database discovery module.
 *          Depending on the UUIDs that are discovered, this function should forward the events
 *          to their respective services.
 *
 * @param[in] p_event  Pointer to the database discovery event.
 */
static void db_disc_handler(ble_db_discovery_evt_t * p_evt)
{
    ble_lbs_on_db_disc_evt(&m_ble_lbs_c, p_evt);
}


/**@brief Database discovery initialization.
 */
static void db_discovery_init(void)
{
    ret_code_t err_code = ble_db_discovery_init(db_disc_handler);
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for initializing the log.
 */
static void log_init(void)
{
    ret_code_t err_code = NRF_LOG_INIT(NULL);
    APP_ERROR_CHECK(err_code);

    NRF_LOG_DEFAULT_BACKENDS_INIT();
}


/**@brief Function for initializing the timer.
 */
static void timer_init(void)
{
    ret_code_t err_code = app_timer_init();
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for initializing the Power manager. */
static void power_management_init(void)
{
    ret_code_t err_code;
    err_code = nrf_pwr_mgmt_init();
    APP_ERROR_CHECK(err_code);
}


static void scan_init(void)
{
    ret_code_t          err_code;
    nrf_ble_scan_init_t init_scan;

    memset(&init_scan, 0, sizeof(init_scan));

    init_scan.connect_if_match = true;
    init_scan.conn_cfg_tag     = APP_BLE_CONN_CFG_TAG;

    err_code = nrf_ble_scan_init(&m_scan, &init_scan, scan_evt_handler);
    APP_ERROR_CHECK(err_code);


    err_code = nrf_ble_scan_filter_set(&m_scan, SCAN_NAME_FILTER, m_target_periph_name);
    APP_ERROR_CHECK(err_code);

    // Setting filters for scanning.
    err_code = nrf_ble_scan_filters_enable(&m_scan, NRF_BLE_SCAN_NAME_FILTER, false);
    APP_ERROR_CHECK(err_code);

}


/**@brief Function for initializing the GATT module.
 */
static void gatt_init(void)
{
    ret_code_t err_code = nrf_ble_gatt_init(&m_gatt, NULL);
    APP_ERROR_CHECK(err_code);
}


/**@ Function for settings scan filters.
 */
/*
static void scan_filters_set(void)
{
    ret_code_t err_code;
    //ble_uuid_t target_uuid = {.uuid = TARGET_UUID, .type = BLE_UUID_TYPE_BLE};

    err_code = nrf_ble_scan_filter_set(&m_scan, SCAN_NAME_FILTER, m_target_periph_name);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_ble_scan_filters_enable(&m_scan,
                       NRF_BLE_SCAN_NAME_FILTER,
                       false);

}
*/
/**@brief Function for handling the idle state (main loop).
 *
 * @details Handle any pending log operation(s), then sleep until the next event occurs.
 */
static void idle_state_handle(void)
{
    NRF_LOG_FLUSH();
    nrf_pwr_mgmt_run();
}


int main(void)
{
    // Initialize.
    log_init();
    timer_init();
    leds_init();
    buttons_init();
    power_management_init();
    ble_stack_init();
    scan_init();
    gatt_init();
    db_discovery_init();
    //lbs_c_init();
    buttons_enable();

    // Start execution.
    NRF_LOG_INFO("Blinky CENTRAL example started.");
    NRF_LOG_INFO("Press button 4 to start scanning.");
    // Turn on the LED to signal scanning.
    //bsp_board_led_on(CENTRAL_SCANNING_LED);

    // Enter main loop.
    for (;;)
    {
        idle_state_handle();
    }
}

Attaching main.c file in which i have done above changes in ble_evt_handler() function.

The base code of this code is BLE_blinky_app_c.

[Hung Bui]

Thanks for the code. How did  you check and find that BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP event never received ?
Please note that you are using NRF_LOG_DEBUG() if you don't enable logging to printout at debug level, you won't see the "Found Service"

Also when you call a function, please make sure you always check the return code.

I just tested here and this code worked fine for me.

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

    // For readability.
    ble_gap_evt_t const * p_gap_evt = &p_ble_evt->evt.gap_evt;

    switch (p_ble_evt->header.evt_id)
    {
        // Upon connection, check which peripheral has connected (HR or RSC), initiate DB
        // discovery, update LEDs status and resume scanning if necessary. */
        case BLE_GAP_EVT_CONNECTED:
        {
            NRF_LOG_INFO("Connected.");
            err_code = ble_lbs_c_handles_assign(&m_ble_lbs_c, p_gap_evt->conn_handle, NULL);
            APP_ERROR_CHECK(err_code);
      err_code = sd_ble_gattc_primary_services_discover(p_gap_evt->conn_handle,
                                                                    0x0001,NULL);

           // err_code = ble_db_discovery_start(&m_db_disc, p_gap_evt->conn_handle);
            APP_ERROR_CHECK(err_code);

            // Update LEDs status, and check if we should be looking for more
            // peripherals to connect to.
            bsp_board_led_on(CENTRAL_CONNECTED_LED);
            bsp_board_led_off(CENTRAL_SCANNING_LED);
        } break;
     case BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP:
                	NRF_LOG_INFO("Found service");
                    
        break;

[Prajakta]

Can you share me your output on terminal?

Calling on_primary_srv_discovery_rsp(p_db_discovery, &(p_ble_evt->evt.gattc_evt)) function under case BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP is it correct?

[Prajakta]

Thank you so much Hung Bui....

It also works for me.
but now the issue is in on_primary_srv_discovery_rsp.

if (p_ble_gattc_evt->conn_handle != p_db_discovery->conn_handle)
{
NRF_LOG_INFO("Return from on_primary_srv_discovery_rsp");
return;
}

is something i am doing wrong?