nRF51822/ BLE nano: Connect to a blue tooth by address

[tyler]

I am developing a script that runs on the nRF51822/ BLE nano to connect to other devices using blue tooth low energy. To do this currently I am looking at the heart rate example that comes with the Nordic SDK. The problem I am having is that the central device in this example searches for peripheral with a certain UUID. I want to search for a device by blue tooth address instead of UUID. How do I do this?

[Jørgen Holmefjord]

Hi,

You can take a look at the Nordic UART Service Client example in the SDK. The address is present in the advertising packet and can be read as follows:

static void on_ble_evt(ble_evt_t * p_ble_evt)
{
    const ble_gap_evt_t * p_gap_evt = &p_ble_evt->evt.gap_evt;
    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GAP_EVT_ADV_REPORT:
        {
            const ble_gap_evt_adv_report_t * p_adv_report = &p_gap_evt->params.adv_report;
            printf("Advertising packet from: %02x%02x%02x%02x%02x%02x\r\n",
                      p_adv_report->peer_addr.addr[0],
                      p_adv_report->peer_addr.addr[1],
                      p_adv_report->peer_addr.addr[2],
                      p_adv_report->peer_addr.addr[3],
                      p_adv_report->peer_addr.addr[4],
                      p_adv_report->peer_addr.addr[5]
                      );
        }break; // BLE_GAP_EVT_ADV_REPORT
    }
}

Best regards,

Jørgen

[tyler]

So if I set p_adv_report->peer_addr.addr to the peripherals bluetooth address and run the example code it will work? I'm trying to enter my bluetooth address into the ble_central and can't find how to add it in and also remove the search for the heart beat UUID.

[Jørgen Holmefjord]

If you want to connect to a specified address you should do something like this:

static const uint8_t m_target_periph_addr[6] = {0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF};

if (memcmp(m_target_periph_addr, p_adv_report->peer_addr.addr, sizeof(p_adv_report->peer_addr.addr)) == 0)
{
    sd_ble_gap_connect(&p_gap_evt->params.adv_report.peer_addr,
                       &m_scan_param,
                       &m_connection_param);
}

[tyler]

Do I have to wait for the on_ble_evt to fire before doing this? Like basically I'm asking if I can just enter in an address and have the device connect or if you need to wait for them to find each other first?

[Jørgen Holmefjord]

Yes, you have to be in the scanning state and respond right after receiving the advertisement package when connecting. You cannot connect directly using the address.