Soft device enable and disable - [DFU] disconnected by the remote device

[AliMahmood123]

Hello all

I am facing a very strange issue, already searched the forum but didnt find anything like it.

Okay so I can get DFU to work. For our custom application we have to disable the soft device for some time for sensor acquisitions and re enable it at a later time for OTA upgrades.

I simply use nrf_sdh_disable_request() to de initialize the soft device successfully, which it does.

I later re - enable soft device using the standard ble calls in example code:

ble_stack_init();
    peer_manager_init();
    gap_params_init();
    gatt_init();
    advertising_init();
    services_init_2();
    conn_params_init();   
     
    //Start execution.
    application_timers_start();
    advertising_start(erase_bonds);

BLE gets initialized successfully, device is advertised and connects to as well. The problem is in DFU. When I attempt DFU, it keeps getting stuck into trying to switch to bootloader, repeatedly giving
"[DFU] disconnected by the remote device"

The logs then try to open the firmware file again, re initiating the process but nothing happen. I have spend quite some time on this and hit a blocker. Any help is appreciated. There must be a step I am missing during re-enabling the soft device

[AliMahmood123]

Oh Yes Vidar

It does reach the ble_dfu_buttonless_bootloader_start_finalize() function and goes till the end until nrf_pwr_mgt_shutdown. After that I am just lost, the android app keeps trying to re- connect and ends up giving the same [DFU] disconnected by the remote device error.

[Vidar Berg]

Ok, assuming you use the nRF connect app, do you see the device advertising in DFU mode if you go back to the scanning view?

[AliMahmood123]

Also Vidar
If you don't mind I got another question, I could also post a separate thread but it would be very easy if you could answer it here.

Okay so we wanted some sort of encryption in the DFU image. If I choose bond forwarding buttonless example and same for DFU Mode, I will be doing BLE bonding right?
Once I achieve that, all BLE communication should be theoretically encrypted by the Link Layer Encryption from Security Manager if BLE bonding is implemented

Is that the case, then it would suffice us a bit, or is it not?

[Vidar Berg]

The image will still be unencrypted on the DFU controller side even if the link is encrypted. So I'm not sure bond sharing will help much if the goal is to prevent potential adversaries from gaining access to your FW image.

Bond sharing can be help prevent unauthenticated users from initiating a DFU update even though the have a valid update package.

[AliMahmood123]

Thanks for such abrupt responses. Yes the FW will still be un encrypted, but we are developing our own app and I think we could manage that, right now we are just looking into BLE stuff

Bond sharing can be help prevent unauthenticated users from initiating a DFU update even though the have a valid update package.

And yes this point is also true, benefits us

But even if the image is unencrypted on DFU controller / Central side, it will be transmitted using Link Layer transmission right?