NFC Pairing with Type 2 versus Type 4 Tag

RE: NFC Pairing with Type 2 versus Type 4 Tag

Hung Bui — Mon, 19 Sep 2022 09:26:14 GMT

Hi Wes,

From what I can see from the code, after waking up from NFC, it will cycle through the bonded device list with the directed advertising. Each time the directed advertising timeout it will cycle to the next bonded device in the list and continue directed advertising. When the list is over, it will do the normal advertising.
Here is when it loops through the list of bonded device to do directed advertising and do regular advertising if the list is over:

Here is when the directed advertising timeout (1.25ms):

So in your case it should do normal advertising after the timeout.
What do you see when you connect the second phone to it ?

In my case here when I test with my phone, I had an issue that a new bond is started with my phone everytime I bring the phone to wake the board up. Maybe something to do with the phone that it wants to do new pairing when reading NFC.

RE: NFC Pairing with Type 2 versus Type 4 Tag

WesC — Sat, 17 Sep 2022 11:18:21 GMT

Hung

sorry for the delay. I will ask the customer for the sniffer. but he recently sent me an email

As for Tag 2/4, There was a period when even the peripheral_nfc_paring sample was not working for my Android phone.

It was not till after a reboot of my phone that it began to work, which leaves a big question as to why. But we have doubts whether that can be answered or not.

The sample itself will pair with a single phone. But once it has (and has then disconnected), the sample won't pair with a second phone apparently due to direct advertising to the first phone.

And only after a re-flash of the sample FW will it pair with the second phone.

Any thoughts?

RE: NFC Pairing with Type 2 versus Type 4 Tag

Hung Bui — Mon, 12 Sep 2022 12:45:40 GMT

Hi Wes,

It's a little bit hard to summarize from the sequence on how to reproduce the issue.
Could you list a step by step instruction on how to reproduce the issue ? Starting from a blank chip.

I would suggest to capture a sniffer trace of the process. We would need to see what exactly causing the issue. Please note that NFC would not involve after the device bonded. When re-encrypting the link the LTK will be used and that is stored on both side.

Error number 9 unfortunately doesn't give us much information. It means BT_SECURITY_ERR_UNSPECIFIED. A sniffer trace would help here.

[quote user=""]As for Type 4 vs Type 2 tags, I assumed type 4 would be more secure. [/quote]

I'm not so sure about the above statement, could you let me know you meant it's more secure regarding NFC communication or the OOB BLE pairing is more secure with Tag type 4 ?

[quote user=""]It also does not start advertising until an NFC touch occurs, so even a previously bonded unit cannot connect without NFC[/quote]

Regarding the above line, I guess it's just how it's designed with the example. You can either add code to start advertising (call advertising_start()) when booting up or call that when a button is pressed.