RE: Deleting Bonds then Restart Advertising does not enable Advertising w/ LE General Discoverable Mode

jj99 — Fri, 01 Nov 2019 20:56:24 GMT

I see, thank you for the detailed response Havard.

RE: Deleting Bonds then Restart Advertising does not enable Advertising w/ LE General Discoverable Mode

Håvard — Fri, 01 Nov 2019 19:05:41 GMT

Hello,

When the advertising is first initialized in main it supplies the advertising data to the advertising module with the flag

adv_flags = BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE;

Later, when we start advertising, we check if we are using the whitelist, and if we are, the flags are now replaced with

BLE_GAP_ADV_FLAG_BR_EDR_NOT_SUPPORTED

But the only case they are set back to BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE is if we call ble_advertising_restart_without_whitelist().

Ideally, we should set the flag back to BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE whenever the check for whitelist returns false.

(before:)

    if (use_whitelist(p_advertising))
    {
        p_adv_params->filter_policy = BLE_GAP_ADV_FP_FILTER_CONNREQ;

        // Set correct flags.
        ret = flags_set(p_advertising, BLE_GAP_ADV_FLAG_BR_EDR_NOT_SUPPORTED);
        VERIFY_SUCCESS(ret);

        p_advertising->adv_evt = BLE_ADV_EVT_FAST_WHITELIST;
    }

(after:)

    if (use_whitelist(p_advertising))
    {
        p_adv_params->filter_policy = BLE_GAP_ADV_FP_FILTER_CONNREQ;

        // Set correct flags.
        ret = flags_set(p_advertising, BLE_GAP_ADV_FLAG_BR_EDR_NOT_SUPPORTED);
        VERIFY_SUCCESS(ret);

        p_advertising->adv_evt = BLE_ADV_EVT_FAST_WHITELIST;
    }
    else
    {
        // Set correct flags.
        ret = flags_set(p_advertising, BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE);
        VERIFY_SUCCESS(ret);
    }

But if you want to avoid making changes to the module, the best workaround that I tested on my desk would what you found yourself. Using the restart function to set the flag in the correct state.

static void test_timeout(void * p_context)
{
    ble_advertising_restart_without_whitelist(&m_advertising);
    (void) sd_ble_gap_adv_stop(m_advertising.adv_handle);
    NRF_LOG_INFO("timeout!");
    delete_bonds();
}

For most of our examples, the bonds are cleared by holding button 2 during reset/power cycle. So the flag would always revert back to BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE whenever the whitelist is deleted because advertising_init() would be called again. Historically, peer devices have tended to ignore the flag(s) of the advertising packet. Which could be another reason this has gone unnoticed for a long time.

I will report this internally. Let me know if you have more problems with this and we will be happy to help out.