RSSI without connection

[Fávero]

Simple question:

Is possible a central to evaluate RSSI before connecting to a peripheral?

The idea is to make central device connect and bond to a peripheral only if a determined RSSI is achieved.

Cheers

Fávero

[Anders Strand]

Every time you get a new BLE_GAP_EVT_ADV_REPORT event

[MicroXP]

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

Thanks,

[Anders Strand]

Yes, it is in dbm.

[mabensur]

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;
    }
}