Android pairing pop-up appears twice

[Anthony Ambuehl]

I would like to establish bonding between my device and an android phone.

My device is acting as both a central and peripheral.  It functions in peripheral role in relation to the phone.  The mobile app is developed only for Android for now.

Application firmware is developed against SDK 16.

I am using peer_manager.  I call pm_init and pm_sec_params_set with

memset( &sec_param, 0, sizeof( ble_gap_sec_params_t ) );

// Security parameters to be used for all security procedures.
sec_param.bond = 1;
sec_param.mitm = 0;
sec_param.lesc = 1;
sec_param.keypress = 0;
sec_param.io_caps = BLE_GAP_IO_CAPS_NONE;
sec_param.oob = 0;
sec_param.min_key_size = 7;
sec_param.max_key_size = 16;
sec_param.kdist_own.enc = 1;
sec_param.kdist_own.id = 1;
sec_param.kdist_peer.enc = 1;
sec_param.kdist_peer.id = 1;

In the ble event handler for BLE_GAP_EVT_CONNECTED, I call

ble_gap_evt_t const *p_gap_evt = &pEvt->evt.gap_evt;

 pm_conn_secure( p_gap_evt->conn_handle, false );

( I have also tested using pm_handler_secure_on_connection with PM_HANDLER_SEC_DELAY_MS set to 75 and 500 mS )

I am NOTcalling pm_conn_sec_prams_reply at all.

I am calling pm_conn_sec_config_reply with allow_repairing = false

The problem I'm encountering is that the pairing pop-up is appearing twice to the user.  Is there a way to change the connection sequence so this pop-up only occurs 1 time?

[Anthony Ambuehl]

The second pairing pop-up only occurs when nrf_ble_lesc_request_handler() processes the LESC request and sd_ble_gap_lesc_dhkey_reply() is called.

Is it possible the softdevice is not handling the LESC reply correctly?

I haven't tested the LESC example yet, maybe this double pairing pop-up issue always occurs with Nordic's imlementation of LESC key processing?

[Anthony Ambuehl]

I have confirmed the ble_app_multirole_lesc_s140_pca10056 example gets the pairing pop-up twice.  The second pairing pop-up presents a PIN code.  This is not very useful since the PCA10056 does not have a display or keyboard inputs.

Our device also lacks a display and inputs.

For a device implementing "Just Works" with LESC key's.. is there a way to avoid this double pop-up?

[Anthony Ambuehl]

I also confirmed with an unmodified SDK17, in the ble_central_and_peripheral/experimental/ble_app_multirole_lesc example the pairing pop-up is sent twice with the second pop-up including a PIN number.

In my application with no I/O capabilities is there anyway to not have the second pop-up since there is no ability to enter a PIN?

[Simonr]

Hi

Sorry about the delayed reply, but we're currently working through the backlog after the Easter vacation. 

I see that the link you provided is related to an RTOS, are you using an RTOS like FreeRTOS in your application as well?

I would like to report this internally to the SoftDevice team so they can have a look at what's going on, but could you provide a sniffer trace file so we can get a look at what's going on over the air as well? As of now, I'm not sure how to avoid this second pop-up I'm afraid.

Best regards,

Simon

[Erikk]

I have encountered a similar issue.

It might be that the android phone just works like that for any kind of connection. For example when trying to connect with a passkey entry I also get two pairing dialogues/notifications. Here the difference is just that the second pairing request is actually required because it shows a PIN or something similar. But with just works the pairing dialogue is also shown, just does not have any PIN or require entering something.