Unable to swap DFU image in dual-slot MCUboot setup on nRF52832 (bootable: false)

[Gabriel Cohen]

Title: Unable to swap DFU image in dual-slot MCUboot setup on nRF52832 (bootable: false)

Environment:

• Board: nRF52 DK (nrf52dk_nrf52832)

• MCUboot: v1.9.0 (built via Zephyr 3.5.99, NCS v2.5)

• Toolchain: Zephyr SDK 0.16.5

• West: 1.2.0

• cmake: 3.21.0

• Python: 3.9.13

• mcumgr (CLI): 0.0.0-dev (Nordic-published)

• Build command:

  west build --pristine --board nrf52dk_nrf52832 \
    -DCONF_FILE=debug.conf \
    -DBOARD_ROOT=... c:/Projects/THZ/GWB/GWB/nrf52_application
  

Partition layout (pm_static.yml):

storage_partition:
  address: 0x7A000
  size:    0x6000
  region:  flash_primary

MCUboot config (child_image/mcuboot.conf):

CONFIG_MCUBOOT_SERIAL=y
CONFIG_BOOT_SERIAL_UART=y
CONFIG_BOOT_SERIAL_WAIT_FOR_DFU=y
CONFIG_BOOT_SERIAL_WAIT_FOR_DFU_TIMEOUT=5000
CONFIG_MCUBOOT_SERIAL_DIRECT_IMAGE_UPLOAD=y
CONFIG_BOOT_SWAP_USING_MOVE=y
CONFIG_BOOT_VALIDATE_SLOT0=y
CONFIG_BOOT_SERIAL_NO_APPLICATION=y

(All other defaults from NCS mcuboot.conf.)

Debug config (debug.conf, acts as prj.conf in my build configuration):

CONFIG_BOOTLOADER_MCUBOOT=y
CONFIG_MCUBOOT_IMG_MANAGER=y
CONFIG_IMG_MANAGER=y
# BLE, UART, logging, GATT client, etc.

Application code:

• main.c calls boot_write_img_confirmed() at startup

• No other mcuboot-specific code changes

Build outputs:

• zephyr/app_update.bin is generated and uploaded via:

  mcumgr --conntype serial --connstring "dev=COM13,baud=115200" \
    image upload -n 2 debug_1/zephyr/app_update.bin
  

• Upload succeeds without errors

Observed behavior:

> mcumgr ... image list
Images:
 image=0 slot=0
    version: 0.0.0
    bootable: false
    flags:
    hash: bf59d59256986ab12a8ca770c8ebb5694dd69cdb26cc3ea4fc6853cb536b9992
 image=0 slot=1
    version: 0.0.0
    bootable: false
    flags:
    hash: 62cf5d15a4b457ed9af4cb887def7ab1a4c2aaa00e65b3fa692bc181a9aa4925
Split status: N/A (0)

• Both slots show bootable=false

• Trying to test the image:

  mcumgr ... image test 62cf5d15a4b457ed9af4cb887def7ab1a4c2aaa00e65b3fa692bc181a9aa4925
  Error: 8
  

• Error 8 indicates MCUMGR_ERR_NOT_SUPPORTED or invalid parameter

What I've tried (no success):

1. Adding a top-level VERSION file

2. Enabling various CONFIG_MCUMGR_* options for image management

Expected behavior:

• After upload:

  • Slot 1 should list with bootable: true

• mcumgr image test <hash> should return success and mark the image pending swap

• On reboot, MCUboot should perform swap/move and run the new firmware

Questions:

1. Why does MCUboot list bootable: false despite signing with the default MCUBoot key?

2. Why does image test return Error 8?

3. What is missing in my NCS/Zephyr build to produce a bootable image?

4. Are there any known issues or patches for Zephyr 3.5.99 mcuboot on nRF52?

Any insights into required CMake/Kconfig changes or build steps to restore proper DFU dual-slot swapping would be greatly appreciated!

— Thanks in advance for your help!

[Vidar Berg]

Hello,

Only a limited subset of the mcumgr commands are implemented in serial recover mode (https://docs.mcuboot.com/serial_recovery.html) and the update is expected to be uploaded directly to the primary slot.

Both slots show bootable=false

This seems to be a limitation when using serial recovery mode. The flag is always shown as false.

Adding a top-level VERSION file

Support for using VERSION filer was added in a later SDK release. In this version you can use the CONFIG_MCUBOOT_IMGTOOL_SIGN_VERSION symbol to specify the version to sign the image with. E.g., CONFIG_MCUBOOT_IMGTOOL_SIGN_VERSION="2.0.0".

• mcumgr image test <hash> should return success and mark the image pending swap

• On reboot, MCUboot should perform swap/move and run the new firmware

Swap and marking the image as pending is only supported when doing DFU via the app (https://academy.nordicsemi.com/courses/nrf-connect-sdk-intermediate/lessons/lesson-9-bootloaders-and-dfu-fota/topic/exercise-1-dfu-over-uart/).

• Why does MCUboot list bootable: false despite signing with the default MCUBoot key?

• Why does image test return Error 8?

• What is missing in my NCS/Zephyr build to produce a bootable image?

• Are there any known issues or patches for Zephyr 3.5.99 mcuboot on nRF52?

1. The flag is always shown as false in serial recovery mode

2. 8 ('MGMT_ERR_ENOTSUP') indicates that the command is not supported/implemented.

3. Does the bootloader not boot the main app on normal boot when you are not entering serial recovery mode?

4. I can't think of anything that should be relevant. I also tried to test it here now to be sure, but it worked on my end. Difference is that I uploaded the image directly to the primary slot (-n 1).

hello_world_serial_recovery.zip

Best regards,

Vidar