nRF52840 random disconnection

[Dani]

Good morning,

We have a new equipment based on the nRF52840 and s140.

                Just now, a new problem has appeared and it is very strange, as it seems to be a ‘random’ error:

 

                We have already assembled tens of equipment, and most of them are perfectly working with any smartphone (using both your ‘nRF Connect’ application or our own application).

                But, we have a few smartphones that show a strange behavior: they are able to perfectly connect to some of our nRF52840-based equipment, and in a few ones, they are able to connect but they get disconnected after a few seconds. Same equipment is connecting to other smartphones without problems (without disconnecting).

                This is (step by step) what it is happening a few times:

• Equipment (nRF52840) is advertising.
• Smartphone stablish connection with equipment using pin number
• First time, the connection is perfectly working.
• If smartphone is disconnected and connected back again with same equipment (Already bonded), then connection is stablished but smartphone disconnects after 30”, approximately. Same behavior is happening with both nRF connect application and our own application. Looking at log in nRF application we see: ‘Connection terminated by peer (status 19)’or ‘GATT_CONN_TIMEOUT’

 

Why is it happening?

Which is the reason?

How can we solve this?

 

 Could you help us? (For your information, we have set MIN_CONN_INTERVAL to 7.5m and MAX_CONN_INTERVAL to 100ms)

Thank you

[Hung Bui]

Hi Daniel, 

I got the update from Brian Kim about your email discussion. I agree with Brian that the sniffer trace would play a very important role here to solve the issue. I have some comments: 

- Regarding the sniffer trace, I could see the communication because the link was encrypted. What you need to do is to either do Legacy pairing and use the sniffer to follow the initial bonding. Or use LESC but in debug mode. 

- Another option you can try is to turn off bonding and encryption requirement to see if the issue is related to bonding or not. If the issue remain, please capture a sniffer trace. 

- The disconnection happened at second 26th into the connection so it may not related to the 30seconds GAP/GATT timeout.

- Please try to do a chip erase on the defected board and test again.

- Please try to test using one of our example in the SDK, ble_app_proximity for example. 

[Dani]

Hi Hung,

I will try to catch the trace you are asking about (even without bonding encryption).

In what regards last two points: just to point out that same chip is perfectly working with other Smartphones. And as Brian probably has said to you regarding the smartphone that is showing problems:

- First connection (when entering pin code, bonding) has never problems

- Next connections (equipment already bonded, so pin is not asked) is when smartphone disconnects after this 26". Also, take into account that, sometimes, it works fine. 

- When other Smartphones connect to same equipment, they are always working fine.

- When affected Smartphone is connecting to other equipment, it is also working fine with most of them --> Problem appears with this Smartphone (and other models I sent to Brian) and a few nRF5240-based equipment (not to all of them: and all of them are identical)

Maybe it is a bit difficult to understand all the scenarios detailed above. If you need more details, maybe we can arrange a virtual meeting:  in this case, send me any link via mail.

Best regards,

Dani.