How to disable b0 and only keep MCUBoot? (Sysbuild and nested example configs make it hard.)

[Kyrre Aalerud]

I'm having a hard time replicating the config needed to be DFU compatible with a build from an earlier SDK version.
Earlier version used only a non upgradeable MCUBoot with upgradeable app and net images built as multi-image.
New needs to build on SDK 3.x and still be compatible with this initial flash layout and MCUBoot.

Due to the nested and convoluted configuration structure and the earlier project being based on nRF5340DK board with overlays it appears to now always bring in b0.
If I disable b0 I also loose boot_write_img_confirmed() meaning I most likely lost DFU from MCUBoot.

There must be something I am missing, but I do find the configuration docs very hard to navigate.

[Kyrre Aalerud]

Am I right in that this is caused by the SB_CONFIG_SECURE_BOOT_APPCORE sysbuild.conf directive?

[AHaug]

Kyrre Aalerud said:

Am I right in that this is caused by the SB_CONFIG_SECURE_BOOT_APPCORE sysbuild.conf directive?

Yes, SB_CONFIG_SECURE_BOOT_APPCORE enables NSIB. You should be able to use SB_CONFIG_SECURE_BOOT_NETCORE=y alone instead to enable b0n for the netcore and not b0, i.e NSIB 

Kind regards,
Andreas