nRF52840 : update from a LTEM modem


My device is already implementing DFU over BLE and all is working fine. But now, I want to add the update over LTEM (Quectel BG77).

I want to proceed like this : 

 ('ko" means kilobyte (KB))

Step 1 => First, the current application on my host CPU (nRF52840) is dowloading the ".bin" and the ".dat" file from the last package availble by using FTP protocol and storing them into the bank2.

Step 2 => Then, the current application checks the checksum of the downloaded binary

Step 3 => Finally, if everything is ok, the application reboots and indicate to the bootloader to copy .bin into bank1 and then execute it.

Is it something that could work ? From what i understand, this is the easiest way to proceed.

Regarding step 1 and step 2, i'm not worried, it is more about step 3 where i have some questions : do I need to update the settings in the bootloader by myself ? How can i proceed ? 

Feel free to help if you have any suggestion ? 

Configuration : 

- SDK17.0.2

- nRF52840

- Soft device : S140