CODED PHY enabled device is unscannable

RE: CODED PHY enabled device is unscannable

jabroni — Thu, 12 Sep 2024 01:34:33 GMT

Thank you for the clarification.

I am only using the B31 module as an advertiser, and my desktop pc as a scanner. My PC uses a standard microsoft bluetooth module and I can at least scan for devices and have the scan response show the B31 dev kit with CODED PHY enabled:

This could very well be a limitation of QT, and maybe a way around it would be to make an adaptor with a NINA B3 module that scan scan for CODED PHY enabled devices.

RE: CODED PHY enabled device is unscannable

Sigurd — Wed, 11 Sep 2024 09:29:11 GMT

Hi!

Scannable means that the scanner can send a scan request.

Connectable means that the scanner can send a connect request.

Are you using U-Blox NINA-B31 BLE for both the advertiser and scanner?

I'm not familiar with QT, but maybe it does not support CODED PHY and Extended Advertising PDUs. These was introduced in Bluetooth 5.0

RE: CODED PHY enabled device is unscannable

jabroni — Wed, 11 Sep 2024 01:55:40 GMT

Hi Sigurd ,

Thank you for the response and the info on extended connectable devices. I was not aware of this, but it is also defined in the core specification guide in section 2.3.1.5. It seems you are correct about what I expect vs what actually happens, and this case what actually happens is that with extended advertising enabled the device is not scannable, but is connectable.

I can see in the trace that with extended advertising enabled, the PDU type is set to AUX_ADV_IND which from the documentation states:

ADV_EXT_IND is over primary advertising channels and is used to indicate that an advertisement will be sent on a secondary advertisement channel. The information in ADV_EXT_IND will inform the scanner:

Which secondary advertising channel will be used by AUX_ADV_IND
Which PHY will be used by AUX_ADV_IND, 1M PHY, 2M PHY, or 1M Coded PHY
When AUX_ADV_IND will be presented on that specified secondary advertising channel

So basically the device is connectable, but just cannot be scanned. So how can I initiate a connection with an unscannable device?

I've attached the trace below and you can filter the device with: `btle.advertising_address == cc:f9:57:8b:a5:a4`

devzone.nordicsemi.com/.../wireshark_5F00_00001_5F00_20240911110007.pcapng

Looking at section 2.3.1.6 of the core specification, and the Extended Advertising Header in the trace, the Advertising Mode is set to "Connectable Non-scannable" with "Connectable Undirected" as the event type (if I have read this correctly):

I can't find anything in QT documentation so far in regards to passive/active scanning and this I will have to look into further.

This makes me wonder something - if the QT central application does not support switching between active and passive scanning, would a dongle configured for CODED PHY solve this? Still trying to understand how to actually connect to a non-scannable but connectable device.

RE: CODED PHY enabled device is unscannable

Sigurd — Tue, 10 Sep 2024 11:57:21 GMT

Hi!

Could you upload the nrf sniffer trace?

Note that you can't have extended, connectable and scannable. All extended connectable, are non-scannable. ref

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s140.api.v7.3.0/group___b_l_e___g_a_p___a_d_v___t_y_p_e_s.html