RSSI without connection

RE: RSSI without connection

mabensur — Sun, 13 Oct 2019 22:22:04 GMT

Complementing Anders Strand answer, when using SDK 15, things are a little different.

You can use examples\ble_central\ble_app_multilink_central as an starting point.

First you need to disable auto connect in scan_init() function:

static void scan_init(void)
{
    ret_code_t          err_code;
    nrf_ble_scan_init_t init_scan;

    memset(&init_scan, 0, sizeof(init_scan));

    init_scan.connect_if_match = false; // I CHANGED
    init_scan.conn_cfg_tag     = APP_BLE_CONN_CFG_TAG;

    //continues... 
}

Then on scan_evt_handler(scan_evt_t const * p_scan_evt) function you need to add a "case" on the "switch case" to look for

"NRF_BLE_SCAN_EVT_FILTER_MATCH" events.

This event will happen every time the scanner finds an device with advertising data accordingly to the filter set on scan_init() . In our case, devices advertising with "Nordic_Blinky" name.

Inside this "case" you can do the following:

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_FILTER_MATCH: //CASE ADDED
        {
            int read_rssi = p_scan_evt->params.filter_match.p_adv_report->rssi;
            
            //PRINTS PEER ID OF THE CURRENT SCAN
            NRF_LOG_RAW_INFO("PEER ID = ")
            for (int i = 0; i < BLE_GAP_ADDR_LEN; i++){
                NRF_LOG_RAW_INFO("%02x", p_scan_evt->params.connected.p_connected->peer_addr.addr[i]);
            }
            NRF_LOG_RAW_INFO("\r\n");
            
            //PRINTS RSSI VALUE
            NRF_LOG_RAW_INFO("RSSI = %d", read_rssi);
            NRF_LOG_RAW_INFO("\r\n");
            NRF_LOG_RAW_INFO("\r\n");
            
            
            //NRF_LOG_INFO("RSSI = %d", read_rssi);
            break;
        }

        default:
            break;
    }
}

RE: RSSI without connection

Anders Strand — Mon, 23 May 2016 06:51:38 GMT

Yes, it is in dbm.

RE: RSSI without connection

MicroXP — Fri, 20 May 2016 16:27:31 GMT

What are the units of p_adv_report->rssi? is it in dbm?

Thanks,

RE: RSSI without connection

Anders Strand — Mon, 07 Dec 2015 12:40:34 GMT

Every time you get a new BLE_GAP_EVT_ADV_REPORT event

RE: RSSI without connection

Fávero — Fri, 04 Dec 2015 16:22:11 GMT

Thanks!

When does the RSSI is updated? Everytime on_ble_evt is called?

RE: RSSI without connection

Anders Strand — Fri, 04 Dec 2015 15:10:55 GMT

See the scanning section of the BLE Central Tutorial.

In most SDK examples you will have the following function handling BLE events:

static void on_ble_evt(ble_evt_t * p_ble_evt)
{
    uint32_t              err_code;
    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;

The p_adv_report contains all the received advertisement data. You will find the rssi at p_adv_report->rssi.

See the documentation on the type ble_gap_evt_adv_report_t

RE: RSSI without connection

RK — Fri, 04 Dec 2015 11:41:13 GMT

Don't remember seeing an example. But the structure is documented, you receive the advertising event, check the rssi, if it's high enough for you, you call the connect on the peripheral. That's it.

RE: RSSI without connection

Fávero — Fri, 04 Dec 2015 11:29:41 GMT

Thank you! Could you please point an example on how to do that?

Fávero

RE: RSSI without connection

RK — Fri, 04 Dec 2015 11:23:15 GMT

Well yes - the RSSI received is in the advertising report event structure, ble_gap_evt_adv_report_t. So you can read it before you connect. You can also put the TX power in the advertising packet as well if you like so you have a good idea how close the device actually is to you.