nrf52840 Dongle giving 0x3D reason on Disconnect after a while.

[noob_123]

Hi,

I have nrf52840-Dongle and nrf52833DK and it was working all good few days back with my code for BLE-UART (Centeral-nrf52840 Dongle and peripheral nrf52833DK) but now I found that the same code is not working as it should with the BLE for nrf52840 Dongle. I am using nrf52833 DK to connect to nrf52840-Dongle but it is connecting and disconnecting with reason 0x3D again and again. When I changed my dongle it worked fine and start sending and receiving data as it was doing previously.  

Can you please tell if this is a hardware related issue or something else that can be fixed?

Thank you

[Simonr]

Hi

Disconnect reason 0x3D means that a message failed a Message Integrity Check (MIC) which means the other end is required to disconnect by the specification, as the connection is no longer secure. This should only happen when the key used for encryption is wrong, and my guess is that you connected and bonded once, then perhaps erased the bonding information on either of the sides before trying to connect again with the old bonding info, which might result in an error like this as the wrong encryption will be returned from the side with no bonding information.

I think you should be able to get the device back up and running if you make sure bonding information on both devices is deleted, then connect and pair again. This was also reported just a few days ago, but there the issue was a phone having trouble with Bluetooth connections in some WiFi states.

Best regards,

Simon

[noob_123]

I updated the Firmware on both devices but still it is showing the same behavior with particular dongle. But if I change the dongle everything works fine. 
What else then updating the firmware can resolve this issue?

[Simonr]

Try deleting the bonding information on the nRF52833 peripheral as well in case that is the device that is keeping this "old" information hindering the Dongle from connecting correctly to it. You can also try doing a full erase using the nRF Connect Programmer application for example.

Best regards,

Simon

[noob_123]

I can erase all the Flash from nrf52833 using nRF Connect Programmer but how to fully erase nrf52840 dongle?

[Simonr]

Hi

Please note that if you erase the full flash on an nRF52840 Dongle you will need to do some soldering to reflash the the DFU bootloader that lets you flash projects directly to the Dongle (see the "Recover after an accidental UICR erase" section in our Dongle Programming tutorial for details.)

But in order to erase and program your nRF52840 Dongle using the Programmer app, you should be able to detect it as an Open DFU Bootloader when choosing your device. Please note that it must be in the Bootloader mode (press the side mounted button next to the white one while it is powered to enter the bootloader mode.

Best regards,

Simon