Connect to Generic Access Service with SDK 17.1.0

[ricardo.oliveira]

From the examples of SDK 17.1.0 (I'm Not using Zephyr), I'm trying to connect to a beacon's Generic Access Service, so I can read the characteristic 0x2A00 and then read it's name. But I'm not able to even connect to it yet.

I scanned the beacon and the service of this access service is: 00001800-0000-1000-8000-00805f9b34fb.

How can I achieve that?

Below is my code. 

static ble_uuid_t const m_nus_uuid =
{
    .uuid = 0x2A00,
    .type = BLE_UUID_TYPE_BLE
};
static ble_gap_scan_params_t const m_scan_param =
{
    .active        = 0x01,
    .interval      = NRF_BLE_SCAN_SCAN_INTERVAL,
    .window        = NRF_BLE_SCAN_SCAN_WINDOW,
    .filter_policy = BLE_GAP_SCAN_FP_ACCEPT_ALL,
    .timeout       = SCAN_DURATION,
    .scan_phys     = BLE_GAP_PHY_1MBPS,
};

static void db_discovery_init(void)
{
    ble_db_discovery_init_t db_init;

    memset(&db_init, 0, sizeof(ble_db_discovery_init_t));

    db_init.evt_handler  = db_disc_handler;
    db_init.p_gatt_queue = &m_ble_gatt_queue;

    ret_code_t err_code = ble_db_discovery_init(&db_init);
    APP_ERROR_CHECK(err_code);
}
void ble_evt_handler(ble_evt_t const * p_ble_evt)
{
    ret_code_t            err_code;
    ble_gap_evt_t const * p_gap_evt = &p_ble_evt->evt.gap_evt;
    ble_nus_c_evt_t nus_c_evt;

    if(p_ble_evt == NULL)
    {
        return;
    }

    if((m_ble_nus_c.conn_handle != BLE_CONN_HANDLE_INVALID)
       && (m_ble_nus_c.conn_handle != p_ble_evt->evt.gap_evt.conn_handle))
    {
        return;
    }

    switch(p_ble_evt->header.evt_id)
    {
        case BLE_GAP_EVT_CONNECTED:
        {
            err_code = ble_db_discovery_start(&m_db_disc, p_ble_evt->evt.gap_evt.conn_handle);
            APP_ERROR_CHECK(err_code);

            err_code = ble_nus_c_handles_assign(&m_ble_nus_c, p_ble_evt->evt.gap_evt.conn_handle, NULL);
            APP_ERROR_CHECK(err_code);
            
            break;
        }
        case BLE_GAP_EVT_DISCONNECTED:
        {
            if(p_ble_evt->evt.gap_evt.conn_handle == m_ble_nus_c.conn_handle
                && m_ble_nus_c.evt_handler != NULL)
            {
                nus_c_evt.evt_type = BLE_NUS_C_EVT_DISCONNECTED;
                m_ble_nus_c.conn_handle = BLE_CONN_HANDLE_INVALID;
                m_ble_nus_c.evt_handler(&m_ble_nus_c, &nus_c_evt);
            }
            break;
        }
        default:
            break;
    }
}
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;

        case NRF_BLE_SCAN_EVT_CONNECTED:
            myFlags.connected = true; //NEVER GOES TRUE
            break;

        case NRF_BLE_SCAN_EVT_SCAN_TIMEOUT:
            myFlags.scanning = false; //used to restart scanning if timeout
            break;

        default:
                break;
    }
}
static void scan_init(void)
{
    ret_code_t err_code = 0;
    nrf_ble_scan_init_t init_scan;

    memset(&init_scan, 0, sizeof(init_scan));
    init_scan.p_scan_param     = &m_scan_param;
    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_UUID_FILTER, &m_nus_uuid);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_ble_scan_filters_enable(&m_scan, NRF_BLE_SCAN_UUID_FILTER, false);
    APP_ERROR_CHECK(err_code);
}
void scan_start(void)
{
    ret_code_t err_code;

    (void) sd_ble_gap_scan_stop();

    //set params
    err_code = nrf_ble_scan_params_set(&m_scan, &m_scan_param);
    APP_ERROR_CHECK(err_code);

    //start scan
    err_code = nrf_ble_scan_start(&m_scan);
    APP_ERROR_CHECK(err_code);
}
int main(void)
{
    // Initialize.
    ble_stack_init();
    scan_init();
    gatt_init();
    db_discovery_init();

    scan_start();

    while (true)
    {
        // REST OF MY CODE
        // ....
        // ....
    }
}

[Sigurd]

Hi!

But I'm not able to even connect to it yet.

    err_code = nrf_ble_scan_filter_set(&m_scan, SCAN_UUID_FILTER, &m_nus_uuid);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_ble_scan_filters_enable(&m_scan, NRF_BLE_SCAN_UUID_FILTER, false);
    APP_ERROR_CHECK(err_code);

You are filtering on NUS UUID, but the beacon does not have the NUS UUID.

so I can read the characteristic 0x2A00 and then read it's name.

See this post on how to do that:  RE: Reading the central device name (smart phone) in nRF52DK(Peripheral) and printing on the terminal 

[ricardo.oliveira]

Sigurd said:

You are filtering on NUS UUID, but the beacon does not have the NUS UUID.

My beacon do not have an connectable UUID? Sorry I didn't get it.

I was able to connect to the beacon via it's MAC address, but for my development that is not useful. I should try to connect to any beacon of this type that is around, so I would not know all MAC address to connect to. After I connect to any nearby beacon, than I'd read it's name and so my program logic would start.

[Sigurd]

From the screenshot, the beacon seem to only have the Generic Access Service, and don't have e.g. the NUS service.

A BLE advertiser, can advertise different kind of data. e.g.  Incomplete/Complete UUID list of available services, Shortened/Complete Local Name, Tx Power Level, Manufacturer Specific Data, etc. If you want to find "your beacon" you need to advertise something that is unique for your beacons.

[ricardo.oliveira]

What I mean is, since I know my beacon is connectable, and suppose it has only the Generic Access Service, how can I connect to it and then read the device name in the UUID characteristic 0x2A00?

I saw the link you attached, but since I'm new to Ble and nordic, it still lacks informations for me.

What I did here was to set "init_scan.connect_if_match = false", and then in the BLE_GAP_EVT_ADV_REPORT case inside the callback of the event handler, I could see my beacon MAC and other informations, but I don't know how to proceed to connect to it and read that characteristic.

 

[Sigurd]

Could you post a screenshot on how the advertising data looks like for the beacon, e.g. using nRF Connect for mobile ?
Maybe there is some information apart from the MAC address that you can use to trigger a connect on.