Central discovery service with multiple peripheral

[HuanVH]

Hello

I'm trying connect central to 4 peripheralPeripheral has 3 different customization services. When I connected to 4 peripheral, I encountered the problem of service collection not getting conn_handle like the conn_handle of discovery (deviceID in the image). I added a delay after every connected event of 200ms. But things are not satisfactory. The picture below shows the result I got from one service collection, and the other services have the same situation.

Collection service code of central

void ble_sensor_on_db_disc_evt(ble_sensor_t * p_sensor, const ble_db_discovery_evt_t * p_evt)
{
   
    //read data:sensor, error, bas
    if (p_evt->evt_type == BLE_DB_DISCOVERY_COMPLETE &&
        p_evt->params.discovered_db.srv_uuid.uuid == VNETGPS_SENSOR_SERVICE_READ &&
        p_evt->params.discovered_db.srv_uuid.type == p_sensor->uuid_type)
    {
        uint32_t i;

        ble_sensor_evt_t evt;

        evt.evt_type = BLE_SENSOR_EVT_DISCOVERY_COMPLETE;
        
        evt.conn_handle = p_evt->conn_handle;
        
        for (i = 0; i < p_evt->params.discovered_db.char_count; i++)
        {
            const ble_gatt_db_char_t * p_char = &(p_evt->params.discovered_db.charateristics[i]);
           
            switch(p_char->characteristic.uuid.uuid)
            {
                case VNETGPS_SENSOR_CHAR_SENSOR:
                {
                    evt.sensor.sensor_db.char_handle = p_char->characteristic.handle_value;
                    evt.sensor.sensor_db.sensor_cccd_handle = p_char->cccd_handle;
                }
                    break;
                case VNETGPS_SENSOR_CHAR_MORE:
                {
                    evt.more.more_db.char_handle = p_char->characteristic.handle_value;
                    evt.more.more_db.more_cccd_handle = p_char->cccd_handle;
                }
                    break;
                default:
                    break;
            }
        }
        if (p_sensor->conn_handle != BLE_CONN_HANDLE_INVALID)
        {
            if ((p_sensor->peer_sensor_db.sensor_cccd_handle == BLE_GATT_HANDLE_INVALID) &&
                (p_sensor->peer_sensor_db.char_handle == BLE_GATT_HANDLE_INVALID))
            {
                p_sensor->peer_sensor_db = evt.sensor.sensor_db;
            }

            if ((p_sensor->peer_more_db.more_cccd_handle == BLE_GATT_HANDLE_INVALID) &&
                (p_sensor->peer_more_db.char_handle == BLE_GATT_HANDLE_INVALID))
            {
                p_sensor->peer_more_db = evt.more.more_db;
            }
        }

        p_sensor->evt_handler(p_sensor, &evt);
    }   
}

event ble of central

 switch (p_ble_evt->header.evt_id) 
  {
    case BLE_GAP_EVT_CONNECTED:
    // start discovery of services.
//        memset(&m_db_disc[p_gap_evt->conn_handle], 0, sizeof(m_db_disc[p_gap_evt->conn_handle]));
        NRF_LOG_INFO("Connected.");
        err_code = ble_db_discovery_start(&m_db_disc[p_gap_evt->conn_handle], p_gap_evt->conn_handle);
        nrf_delay_ms(BLE_DISCOVERY_TIME);
        if (err_code != NRF_ERROR_BUSY) 
        {
          APP_ERROR_CHECK(err_code);
        }
        if (ble_conn_state_central_conn_count() < NRF_SDH_BLE_CENTRAL_LINK_COUNT) 
        {
          scan_start();
        }
    break;

    case BLE_GAP_EVT_DISCONNECTED:
        NRF_LOG_INFO("Disconnected.");
        if (ble_conn_state_central_conn_count() < NRF_SDH_BLE_CENTRAL_LINK_COUNT) 
        {
          scan_start();
        }
    break;

on peripheral

#define MIN_CONN_INTERVAL               MSEC_TO_UNITS(100, UNIT_1_25_MS)        /**< Minimum acceptable connection interval (0.1 seconds). */
#define MAX_CONN_INTERVAL               MSEC_TO_UNITS(200, UNIT_1_25_MS)        /**< Maximum acceptable connection interval (0.2 second). */
#define SLAVE_LATENCY                   0                                       /**< Slave latency. */
#define CONN_SUP_TIMEOUT                MSEC_TO_UNITS(1000, UNIT_10_MS)         /**< Connection supervisory timeout (4 seconds). */

#define FIRST_CONN_PARAMS_UPDATE_DELAY  APP_TIMER_TICKS(5000)                   /**< Time from initiating event (connect or start of notification) to first time sd_ble_gap_conn_param_update is called (5 seconds). */
#define NEXT_CONN_PARAMS_UPDATE_DELAY   APP_TIMER_TICKS(30000)                  /**< Time between each call to sd_ble_gap_conn_param_update after the first call (30 seconds). */
#define MAX_CONN_PARAMS_UPDATE_COUNT    3                                       /**< Number of attempts before giving up the connection parameter negotiation. */

I'm sorry, my english 

P/s: when I connect each device, this problem does not occur.

[HuanVH]

I have found the solution:
I have added the scan line after handler discovery, I think putting it there is more appropriate than putting it at event connected

void db_disc_handler(ble_db_discovery_evt_t *p_evt) {
    ble_sensor_on_db_disc_evt(&m_sensor[p_evt->conn_handle], p_evt);
    ble_write_on_db_disc_evt(&m_write[p_evt->conn_handle], p_evt);
    ble_angle_on_db_disc_evt(&m_angle[p_evt->conn_handle], p_evt);
    if (ble_conn_state_central_conn_count() < NRF_SDH_BLE_CENTRAL_LINK_COUNT) 
    {
        scan_start();
    }
}

[nine-fox]

Hi,

Thanks for your code! I met the same issue. And your code works quite well for me.

However, I think it would be better to put that code into NRF_BLE_SCAN_EVT_CONNECTED event, since at this stage, the discovery is already done.

How about it?

Thanks,

Vincent

[HuanVH]

i don't think so

When i used a breakpoint in NRF_BLE_SCAN_EVT_CONNECTED, i can't see anything of conn_handle available. But putting that code in db_disc_handler is not very optimal

And i'm finding the location, where discovery collection is already done

Sorry, my english not better