Unable to connect to specific Android devices (Samsung S21, and more)

[fr_adv]

Dear Nordic support team,

We are currently using a nRF52840 µC with NVS V.2.6.1 and sometimes the Android device acting as central, is unable to establish a BLE connection with the nRF52 peripheral. There is no bonding, the SMP protocol is not used, it's a simple BLE connection.

I know there are similar tickets open on this topic, especially this one, but I'm wondering if there are some news regarding this topic which is critical for us.

There is no notification on any BLE connection at application side when this issue occurs, the ".connected" callback is not called.

We have tried to get a Wireshark trace with the BLE sniffer, but I'm wondering if the capture is correct because we encounter issues sometimes with Wireshark and the BLE sniffer and miss the packets when the connection is established, which is quite annoying. But maybe you can still use thiis wireshark file and find any issue regarding the BLE connection ?

I will get back to you if we reproduce this issue and manage to have more Wireshark logs on this subject.

trame_ble_carte_74.pcapng

Best regards

Aurélien

[Hung Bui]

Hi Aurelien, 
What I can see in the trace is that the peripheral didn't receive or didn't response to the connect request from the phone: 

The phone continued to send (and resend) a packet 6 times before give up and the connection was considered terminated. 

The ticket you pointed to didn't go to the root cause of the issue so we don't know what exactly caused it and if it's the same issue as yours. 

Do you have any Filter Accept List (whitelist) implemented on the nRF52 ? 

Could you try to do a full erase (chiperase) of the chip and then flash a simple BLE application (peripheral_lbs for example) and test again  ? 

Could you try to test with other boards ? and with other phones ? 

[fr_adv]

Dear Hung Bui,

Thank you for your answer. Unfortunately this bug has very little occurence and is hard to catch.

Other boards did reproduce this issue, and on some other phones as well (Redmi Note 8 for instance) but for example it never occurs with iPhones.

We have no whitelist implemented.

I'll try to provide you another feedback if we manage to reproduce it.

Best regards,

Aurélien

[Hung Bui]

Hi Aurelien, 

If it rarely happen, it's most likely just interference ? If the peripheral couldn't catch the Connect request (due to packet corruption) it will result in what showed in the trace. 
Let us know if you find a way to reproduce the issue.