Simple Observing of nearby devices

RE: Simple Observing of nearby devices

guma — Tue, 20 Aug 2019 05:02:57 GMT

Hi Gordan

I have to advertise and scan the advertising packet and display rssi.

I have succesfully completed advertising. To simple code for scan i was looking for and came across your solution.

I want to know on peripheral i have beacon cide with device name.

on central : ble app uart code is that okay.?

kindly let me know .

Thanks in advance.

RE: Simple Observing of nearby devices

Rasul Kishov — Tue, 12 Jul 2016 10:51:29 GMT

Useful! Thank you. Saved me so much time and RAM :)

RE: Simple Observing of nearby devices

Einar Thorsrud — Thu, 11 Feb 2016 09:33:56 GMT

Thanks for posting your solution. That will be helpful for others with similar questions.

RE: Simple Observing of nearby devices

Gordon — Thu, 04 Feb 2016 14:12:00 GMT

Ok, in case anyone else is interested in this - with Einar's help:

#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. */


static void on_ble_evt(ble_evt_t * p_ble_evt) {
switch (p_ble_evt->header.evt_id) {
  // ...
  case BLE_GAP_EVT_ADV_REPORT: {
    // Advertising data received
    const ble_gap_evt_adv_report_t *p_adv = &p_ble_evt->evt.gap_evt.params.adv_report;
    printf("RSSI: %d\n", p_adv->rssi);
    // also data, address, etc in p_adv
    break;
  }
}

ble_gap_scan_params_t     m_scan_param;
// non-selective scan
m_scan_param.active       = 0;            // Active scanning set.
m_scan_param.selective    = 0;            // Selective scanning not set.
m_scan_param.interval     = SCAN_INTERVAL;// Scan interval.
m_scan_param.window       = SCAN_WINDOW;  // Scan window.
m_scan_param.p_whitelist  = NULL;         // No whitelist provided.
m_scan_param.timeout      = 0x0000;       // No timeout.

err_code = sd_ble_gap_scan_start(&m_scan_param);

// and stop with
err_code = sd_ble_gap_scan_stop();

This seems to work, however the advertising window of 50ms / 100ms means that you do tend to miss things. Is it ok to put the window up to 100ms as well? It seems to work.

RE: Simple Observing of nearby devices

Einar Thorsrud — Thu, 04 Feb 2016 12:52:04 GMT

Yes, that is correct. As long as you only scan for peripherals and never initiate a connection, you can set CENTRAL_LINK_COUNT to 0 in order to reduce the amount of RAM required by the SoftDevice.

RE: Simple Observing of nearby devices

Gordon — Thu, 04 Feb 2016 11:34:09 GMT

Thanks - so sd_ble_gap_scan_start is the magic function that's needed by the look of it, and you get a BLE_GAP_EVT_ADV_REPORT in on_ble_central_evt? Does the softdevice have to have CENTRAL_LINK_COUNT>0? Ideally not since there would be no link as such?

RE: Simple Observing of nearby devices

Einar Thorsrud — Thu, 04 Feb 2016 10:15:05 GMT

There is just one concurrent BLE Central & Peripheral example in SDK 11, the experimental BLE Relay Example. It is probably a bit more complex than what you need, but it demonstrates how the device can act as a peripheral (both advertising and keeping connections) and as a central (including scanning).