Ble peripherals(nrf5340dk) disconnect instantly after connecting with central(nrf5240 dongle) sometimes

[Bhavya Mathukiya]

Hi Team,

I am working on connecting multiple peripherals (nrf534odk) with a central (nrf52840-dongle), some times all the peripherals are able to connect with central smoothly, but some times few peripherals gets disconnected instantly after connection. Upon 1-2 time retry it may connect with the central. Here is my setup details.

Setup Detail:
SDK: NCS 2.1.0
Central: nrf52840-dongle
Peripherals: 10 * nrf5340dk

Sharing connect-disconnect log for reference. Here I am trying to connect peripheral with MAC F2:46:0E:DF:C2:4A. The peripheral gets connected and at the same time it gets disconnected with reason 0x3E. But upon retrying it gets connected successfully. What should be the possible cause of this behavior?

Thank you,

Bhavya

[Einar Thorsrud]

Hi,

0x3E is a standard Bluetooth error code that means that the connection failed to be established, which you will get if there are no successful connection events after the central sent the connection indication (see this post). It is not uncommon to get this from time to time when there are many active connections concurrently or if the RF environment is noisy etc. If the problem is the former, then you should see less of it with fewer concurrent connections and/or longer connection intervals or shorter event lengths. And if the cause is the latter, you should see less in a better RF environment. When this happens, the right thing to do is simply to try again until the connection is established successfully.

[Bhavya Mathukiya]

Hi Einar Thorsrud ,

Thanks for the response. Is there any retry mechanism in NCS so that central do retry itself to connect with peripheral in such cases. If yes maximum how many times does it retry?

[Einar Thorsrud]

Hi,

There is no built-in retry mechanism. You just need to try to connect again by calling bt_conn_le_create() again.