pc-ble-driver (master) scan_start() reports only one device upon every invocation

[Prashant Ambardekar]

Hi,

I am trying to use latest pc-ble-driver. The code is based on pc-ble-driver-js. When I call sd_ble_gap_scan_start(), I get only one "device discovered" event. This happens on every invocation of sd_ble_gap_scan_start(). Is there any inherent change in the way sd_ble_gap_scan_start() is used? Do I need to change scan params or pass different size for adv_report_buffer?

My code looks like this:

    

    static uint8_t mp_data[BLE_GAP_ADV_SET_DATA_SIZE_EXTENDED_MAX_SUPPORTED] = { 0 };

    static ble_data_t m_adv_report_buffer;

    void Adapter::GapStartScan(uv_work_t *req)

    {

        auto baton = static_cast<StartScanBaton *>(req->data);

        m_adv_report_buffer.p_data = mp_data;

        m_adv_report_buffer.len = sizeof(mp_data);

        baton->result = sd_ble_gap_scan_start(baton->adapter, baton->scan_params, &m_adv_report_buffer);

    }

start scan, stop scan work fine, they do not return any error. similar code used to report multiple devices with SD 3.1.

Scan params are as follows

active= true
interval = 100
window = 20
timeout =  -1

extended = 0

report_incomplete_evts = 0

filter_policy = BLE_GAP_SCAN_FP_ACCEPT_ALL

scan_phys = BLE_GAP_PHY_1MBPS

I am using following h/w and s/w config

nRF 52840 dongle

Soft Device 140 6.1.0

pc-ble-driver (master)

Windows 10 64 bit

Node JS 9.4.0

[Einar Thorsrud]

Hi,

Which SoftDevice are you using? If you are using API version 6, then you have to call sd_ble_gap_scan_start() to continue scanning after receiving an advertising report.

[AmrutaZende]

What is the logic behind this change w.r.t v3.*?

[Einar Thorsrud]

The subsequent calls to sd_ble_gap_scan_start() signals to the SoftDevice that the application is ready to receive a new advertising report, instead of just flooding the application with advertising reports as they arrive. Scanning still continues in the background.

[AmrutaZende]

During the time I am scanning, how do I prevent my application from missing out on any advertisements?

Assume following timeline

T0 - I called sd_ble_gap_scan_start

T1 - I got the event BLE_GAP_EVT_ADV_REPORT and it took me X milliseconds to process this

T1+X - I called sd_ble_gap_scan_start in order to continue the scan

What happens to the advertisements that were received between T1 and (T1 + X)? 

Would they be queued and would I get the event BLE_GAP_EVT_ADV_REPORT again immediately after I call sd_ble_gap_scan_start again?

Is that what is meant by "Scanning still continues in the background"?