SoftDevice s332 v2.0.0 appears to hang on connection w/Motorola Edge 50

[grantrudd]

Hello,

We are investigating a compatibility issue between our devices running nRF5 SDK 12.3.0 with softdevice s332 v2.0.0 and a Motorola Edge 50 smartphone. From BLE sniffer traces, the softdevice appears to hang during some link layer transactions at the beginning of the connection for approximately 5 seconds before the connection is terminated and the device begins advertising again. Testing was done with nRF Connect running on the Edge 50.

My first instinct was possible incompatibility between some of the new BLE 5.3 features and the older BLE 4.2 implementation in the soft device, but this does not appear to be an issue on other BLE 5.3+ devices we have tested.

Attached is a sniffer trace of the hung connection. Does anything here look suspicious?

Thanks,

Grant

edge_50_rival.pcapng

[Vidar Berg]

Hello,

Thank you for providing the sniffer captures. I reviewed them but didn’t notice any obvious specification violations from either side, except that the peripheral (S332) stops responding to the central. Could you please check the disconnect reason reported by the peripheral?

Best regards,

Vidar

[grantrudd]

Hi Vidar,

Thanks for taking a look! I am getting `BLE_HCI_DIFFERENT_TRANSACTION_COLLISION 0x2A` in the disconnect event.

Grant

[Vidar Berg]

Hi Grant,

Thanks for confirming. It seems the issue might be related to the LL_CHANNEL_REPORTING_IND procedure (shown as an unknown control opcode in the WS trace) initiated by the phone. The SoftDevice correctly responds with LL_UNKNOWN since it does not support this procedure, which was introduced in Bluetooth v5.3. But the problem is that the Softdevice terminates the link after sending this response. I will confirm the details with R&D on Monday.

Vidar

[Vidar Berg]

Hi Grant,

Unfortunately, I can confirm that this is a bug in the softdevice. It is correct behavior that it responds with LL_UNKNOWN to the LL_CHANNEL_REPORTING_IND from the phone since it does not implement this feature, but it is not supposed to terminate the link afterward. Is it an option for you to update to a newer Softdevice through DFU? Channel reporting is not a feature which can be disabled in the Android app so I'm afraid there is not other workaround for this interoperability issue.

Vidar

[grantrudd]

Hi Vidar,

Thanks for the reply. Updating the softdevice is a possibility for us. I'll discuss this with out team and we will reach of if we need further support.

Thanks,

Grant