48-bit Bluetooth Address changes after OTA DFU

[Lorenzo]

Hi,

we've noticed that after performing an OTA DFU, the Bluetooth Address of the device changes as follows: new_address = old_address - 1

Example:
Address before OTA DFU: C7:4B:F6:07:74:0C

Address after OTA DFU: C7:4B:F6:07:74:0B

Is it a regular/necessary behaviour or there's a way to perform OTA DFU without changing the Bluetooth Address?

Thanks and best regards

[Simonr]

Hi

Yes, this is a default setting. We do this to solve the issue that central devices (phones/tablets etc.) may try to re-encrypt the connection if the address stays the same. This is the simplest way to do DFU without worrying about re-encryption and termination from the central device (Known issue with Android devices). 

If you want the DFU process to be encrypted you should send the bond information from the application to the bootloader. There are several ways to do this, one approach is detailed in this link. Note that this solution only works if you start with your application first, and then enter bootloader. You can use flash to share bond information with the application, and that will make it possible to start bootloader from reset.

For more information on DFU, please visit our DFU FAQ post.

Best regards,

Simon