nb_bt_mode(BT1, BT_MODE_SCAN);
for (i = 0; i < 20; i++) {
    
    devices = nb_bt_dev_list(BT1);
    printf("%d: %d\n", i, length(devices));
    for (d = 0; d < length(devices); d++) {
        dev_info = nb_bt_dev_info(BT1, devices[d]);
      
    }
    sleep(1);
}
nb_bt_mode(BT1, BT_MODE_OFF);