unexpected BLE_GATTC_EVT_TIMEOUT

[DmitrySol]

Hi.

We use nRF5_SDK_17.0.2_d674dde as central

And phone as peripheral.

Usually system works correctly for a long time.

But sometimes it enter in strange state.

Connections are broken every 30 seconds after successful connection.

I have think previously, it is because of no activity on NUS service.

So sending NUS message after BLE_NUS_C_EVT_DISCOVERY_COMPLET was added.

But it doesn't help.

Please teach a nature of this behavior and advice steps to prevent it.

Thanks. BR.

[Kenneth]

Hi,

30 seconds is typically a timeout for a procedure that is not handled. An on-air sniffer log would be very useful:

https://www.nordicsemi.com/Software-and-tools/Development-Tools/nRF-Sniffer-for-Bluetooth-LE 
https://infocenter.nordicsemi.com/pdf/nRF_Sniffer_BLE_UG_v3.2.pdf (there might be newer depending on when you read this)

Kenneth

[DmitrySol]

Thanks for answer.

But I can't catch log because of rarely problem.

We have logs from uart. But it is truncated because of size of buffers of host controller.

So I hesitate that it can be useful.

[Kenneth]

It will be difficult to debug without an on-air sniffer log. You can try to output all events that is occurring, and check if there is an event that only occur in one of the logs when disconnecting. E.g. output p_ble_evt->header.evt_id in ble_evt_handler(), though it will be many, but on the other end you are just looking for an event that does not occur in both logs.

Kenneth

[DmitrySol]

Perhaps someone have similar experience?
could you say more probable causes?

when security is established air logs would be useful?

In our case security established successfully. NUS works correctly.
And problem occurs 30 seconds after that.

[DmitrySol]

I can add some observation.

Today situation was repeated again.

Connections were established and closed time after time. Every 30 seconds.

When exchange of NUS messages was made connect was not closed after that over 30 seconds.

In our case when connection is established exchange NUS messages doesn't present.
Phone is as tag. Exchange by NUS messages present only when application on phone is activated.

IIn other case connection supprted  without NUS exchange. For detect phone in nearby.

Could be absence of NUS messages in some cases cause of BLE_GATTC_EVT_TIMEOUT?

[Kenneth]

We need a sniffer log to further help you. If you are interested in finding possible causes of BLE_GATTC_EVT_TIMEOUT in general I suggest to try to search for devzone BLE_GATTC_EVT_TIMEOUT. But without a sniffer log it is difficult to know what is the exact problem in your case. 

Kenneth

[DmitrySol]

Hi Kenneth

I have log now.

I have not found a means to attach log file.

So by this link is laid log file on google drive.

https://drive.google.com/file/d/1XdcAtE7gr8bz3XihdZCH7Q_fVNPmcKga/view?usp=sharing

Connection was encrypted. So only beginning is presented.

I hope that it would be useful.

BR. Dmitry.

[Kenneth]

I do believe we need to decrypt the data. You can find a description at the end of my reply here to get the LTK:
https://devzone.nordicsemi.com/f/nordic-q-a/66239/nrf52810-s112-background-reconnect-issue/271398#271398

Also see here:
https://devzone.nordicsemi.com/f/nordic-q-a/66239/nrf52810-s112-background-reconnect-issue/271467#271467 

With the LTK we should be able to decrypt the data.

Kenneth