dfu issues after migrating from ncs2.9.2 to ncs3.0.2

[ziv123]

hello Nordic

we are working with nrf52840/nrf52832 with ncs (currently on v3.0.2)

i have noticed that when i try to dfu a merged artifact of my version with the new mcuboot of ncs3.0.2 the device does not work after the dfu at all, it seems bricked no matter if i try to reset it after or even try to re flash the same version of merged file with the same mcuboot of ncs3.0.2 it does not respond .. only after flashing a lower version it returns to work (this part is very strange i think)

in previous version with ncs2.9.2 there was no issues with the dfu ..

under app/
sysbuild.conf
SB_CONFIG_BOOTLOADER_MCUBOOT=y
SB_CONFIG_BOOT_SIGNATURE_TYPE_RSA=y
SB_CONFIG_PARTITION_MANAGER=y
SB_CONFIG_PM_OVERRIDE_EXTERNAL_DRIVER_CHECK=y

sysbuild_swap.conf
SB_CONFIG_MCUBOOT_MODE_SWAP_SCRATCH=y

sysbuild_no_swap.conf
SB_CONFIG_MCUBOOT_MODE_SWAP_SCRATCH=n
SB_CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256=y

prj.conf under app/sysbuild/my_app/mcuboot/
CONFIG_FLASH=y
CONFIG_FLASH_xxxx_API=x
CONFIG_MAIN_STACK_SIZE=xxxx

1. any ideas what can be the cause and how can this be fixed ?

2. any idea how to debug the mcuboot using rtt ? i don't want to flash a version via cursor or vscode because then dfu will not work for some other signature reason 

best regards

Ziv

[Vidar Berg]

Hello Ziv,

Do I understand correctly that the application does not boot even after completely re-flashing the device with the merged.hex from the latest version? That would suggest that there is an issue with the new project/app and not really related to the DFU process. First step I would recommend is that you try to debug the new project to find out where the program hangs. Does the app run ok if you build without the bootloader?

Best regards,

Vidar