nRF HTTP FOTA download library and dependent updates

[Ligo George]

• While testing nRF FOTA download library we noticed that it supports only one image update at a time (download image, then reboot).
• Irrespective of the image (either application or second stage bootloader or network core), it is downloaded to the SECONDARY SLOT OF APPLICATION, as the image_num 0 is used everywhere.
• Does this means that we cannot use dependent image feature of Mcuboot ? For e.g. network core image can be considered as dependent image, as if there is any breaking changes in the BLE apis, and it can break the system we update only one image.
• How can we handle these situations with FOTA download library ?

[Hung Bui]

Hi Ligo, 

What I meant was to follow what we did in smp library to modify the Fota download library. 

I'm not 100% sure but as far as I can see the DFU Target library already support multiple images download. You may just need to select correct img_num when you upload the second image. 

You would need to make sure you have configured MCUBoot correctly so that it has the secondary_1 slot for receiving the netcore image. The DFU Target will copy the image to that location and then the MCUBoot and B0n (bootloader on the netcore) will take care of swapping the netcore image from there. 
My suggestion is to get familiar with normal BLE FOTA update of netcore and app core sample before you apply that to your HTTP FOTA application.