Peripheral Not Reconnecting After Being Forgotten by Central Device

[similingus]

I’m working with the nRF5340 and nNF Connect SDK 2.6.1. I’m encountering an issue where, after a central device (e.g. an Android phone) forgets a bonded peripheral device using nRF5340, the peripheral device becomes invisible to the central device. It no longer appears in the “Available devices” list within the Android Bluetooth settings.

It seems the peripheral still believes it’s bonded to the central device after being forgotten. Since the peripheral does not recognize it has been forgotten by the central device, it does not clear the bonding information.I have tried CONFIG_BT_SMP_ALLOW_UNAUTH_OVERWRITE=y based on this post similar to my situation, but this hasn't resolved the problem.

Is there a way to allow the peripheral to be rediscovered by the central device?

Any insights or suggestions would be greatly appreciated!

[dejans]

Hi,

Which application do you use on your Android phone and which on the other peer device?

Could this discussion or this one be helpful in your case?

Best regards,
Dejan

[similingus]

Hi Dejan, 

Thank you for your quick response.

I’m using Android’s Bluetooth setting for pairing and forgetting. On the peripheral side, I’m using Nordic’s Audio Application Unicast server, with no changes to the Bluetooth related configurations.

If you’re suggesting erasing the bonding information within the peripheral application when the central device forgets it, could you advise on an appropriate trigger for this? I’ve tried clearing the bonding information using bt_unpair when the directed advertising timeout caught in connected_cb. However, this timeout also happens during regular disconnections, which forces re-pairing every time the peripheral disconnects.

[dejans]

Hi,

Did you make any changes to the Audio Unicast Server application?

Which Android phone do you use?

Could you provide your project configuration on the peripheral device?

Which Kconfig options mentioned in this thread did you try to add to your project?

Best regards,
Dejan

[similingus]

To reproduce this issue, you can use the nRF5340 Audio DK with the Unicast Server application as-is, without ANY change. I'm testing on a Google Pixel 7a with Android 14.

I've also tried the following four Kconfig options:

• CONFIG_BT_ID_UNPAIR_MATCHING_BONDS=y
• CONFIG_BT_ID_ALLOW_UNAUTH_OVERWRITE=y
• CONFIG_BT_KEYS_OVERWRITE_OLDEST=y
• CONFIG_BT_SMP_ALLOW_UNAUTH_OVERWRITE=y

Unfortunately, none of these options resolved the issue of peripherals becoming invisible after being forgotten.

[dejans]

Hi,

Peripheral could have its "pair" button. When the button is pressed, the device should advertise with its identity address, name and general discoverable flag. This should ensure that device appears in the phone GUI.

Best regards,
Dejan