Sysbuild configuration for a updatable section containing firmware image and meta-data for external component

[Anthony Ambuehl]

NCS 2.7

NRF52840

Building with sysbuild, MCUBOOT, and 2 different applications (mfg and end-user)

My custom board includes a sensor fusion IMU from bosch.  The firmware that must be loaded for this IMU is ~133 KB.  My initial development effort embedded the imu firmware into the application image.  The resulting update image consumes more than 50% of the flash space, and therefore would require reserving space in the external flash for updates. 

The IMU is an excellent candidate for independent update.  It has a well defined communication interface that remains constant across versions.  It may also only need 1-2 updates over the product lifecycle.  

I modified my static partition to create a ext_fw partition area to contain the external firmware image. 

xt_fw:
  address: 0xc200
  end_address: 0x2F000
  region: flash_primary
  size: 0x22200
app:
  address: 0x2F000
  end_address: 0x94000
  region: flash_primary
  size: 0x65000
mcuboot:
  address: 0x0
  end_address: 0xc000
  placement:
    before:
    - mcuboot_primary
  region: flash_primary
  size: 0xc000
mcuboot_pad:
  address: 0xc000
  end_address: 0xc200
  placement:
    align:
      start: 0x1000
    before:
    - mcuboot_primary_app
  region: flash_primary
  size: 0x200
mcuboot_primary:
  address: 0xc000
  end_address: 0x94000
  orig_span: &id001
  - mcuboot_pad
  - ext_fw
  - app
  region: flash_primary
  size: 0x88000
  span: *id001
mcuboot_primary_app:
  address: 0xc200
  orig_span: &id002
  - ext_fw
  - app
  region: flash_primary
  size: 0x85E00
  span: *id002
mcuboot_secondary:
  address: 0x94000
  end_address: 0xfa000
  placement:
    after:
    - mcuboot_primary
    align:
      start: 0x1000
  region: flash_primary
  share_size:
  - mcuboot_primary
  size: 0x66000
nvs_storage:
  address: 0xfa000
  end_address: 0x100000
  placement:
    align:
      start: 0x1000
    before:
    - end
  region: flash_primary
  size: 0x6000
sram_primary:
  address: 0x20000000
  end_address: 0x20040000
  region: sram_primary
  size: 0x40000

From the board dts,I defined two zephyr memory regions.  One region holds meta data such as the image size, and external firmware image kernel version and a pointer to the firmware image data.  The other memory region holds the firmware image itself.

  

	flash@C200 {
		compatible = "zephyr,memory-region";
		reg = <0xC200 0x100>;
		zephyr,memory-region = "ext_fw_meta";
		status = "okay";
	};
	flash@C300 {
		compatible = "zephyr,memory-region";
		reg = <0xC300 0x22D00>;
		zephyr,memory-region = "ext_fw_data";
		status = "okay";
	};

I'm trying to figure out how to proceed with sysbuild to add another buildable image.

I added a sysbuild.cmake as documented docs.nordicsemi.com/.../index.html:

ExternalZephyrProject_Add(
	APPLICATION xx_bhi360_ext_fw_xx
	SOURCE_DIR ${ZEPHYR_BASE}/../app.git/bhi360_ext_fw
)

When I run the build by adding a build configuration within VS Code NRF Connect Extension I get an error about that the directory is empty:

-- west build: generating a build system
Loading Zephyr module(s) (Zephyr base): sysbuild_default
-- Found Python3: C:/ncs/toolchains/ce3b5ff664/opt/bin/python.exe (found suitable version "3.9.13", minimum required is "3.8") found components: Interpreter 
-- Cache files will be written to: D:/Flipperz/flipper_workspace/zephyr/.cache
-- Found west (found suitable version "1.2.0", minimum required is "0.14.0")
-- Board: thomas_b, qualifiers: nrf52840
Parsing D:/Flipperz/flipper_workspace/zephyr/share/sysbuild/Kconfig
Loaded configuration 'D:/Flipperz/flipper_workspace/app.git/app/build_1/_sysbuild/empty.conf'
Merged configuration 'D:/Flipperz/flipper_workspace/app.git/app/sysbuild.conf'
Configuration saved to 'D:/Flipperz/flipper_workspace/app.git/app/build_1/zephyr/.config'
Kconfig header saved to 'D:/Flipperz/flipper_workspace/app.git/app/build_1/_sysbuild/autoconf.h'
CMake Error at C:/ncs/toolchains/ce3b5ff664/opt/share/cmake-3.21/Modules/ExternalProject.cmake:2866 (message):
  No download info given for 'bhi360_ext_fw' and its source directory:

   D:/Flipperz/flipper_workspace/app.git/app/build_1/bhi360_ext_fw

  is not an existing non-empty directory.  Please specify one of:

   * SOURCE_DIR with an existing non-empty directory
   * DOWNLOAD_COMMAND
   * URL
   * GIT_REPOSITORY
   * SVN_REPOSITORY
   * HG_REPOSITORY
   * CVS_REPOSITORY and CVS_MODULE
Call Stack (most recent call first):
  C:/ncs/toolchains/ce3b5ff664/opt/share/cmake-3.21/Modules/ExternalProject.cmake:3700 (_ep_add_download_command)
  cmake/modules/sysbuild_extensions.cmake:350 (ExternalProject_Add)
  D:/Flipperz/flipper_workspace/app.git/bhi360_ext_fw/sysbuild.cmake:1 (ExternalZephyrProject_Add)
  cmake/modules/sysbuild_extensions.cmake:670 (include)
  cmake/modules/sysbuild_images.cmake:13 (sysbuild_add_subdirectory)
  cmake/modules/sysbuild_default.cmake:19 (include)
  D:/Flipperz/flipper_workspace/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:75 (include)
  D:/Flipperz/flipper_workspace/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:92 (include_boilerplate)
  D:/Flipperz/flipper_workspace/zephyr/share/sysbuild-package/cmake/SysbuildConfig.cmake:8 (include)
  template/CMakeLists.txt:10 (find_package)


-- 
   *****************************
   * Running CMake for mcuboot *
   *****************************

cmake doesn't seem to be copying the files from app.git/bhi360_ext_fw into the build folder.

Is this a fault in NCS 2.7 sysbuild that might be fixed if I go to a more recent release?

Is there an existing example of using sysbuild to add an additional image?

What configuration will I need to add for mcuboot to be able to update (one-at-a-time) both the application and the ext_fw partition?

[Vidar Berg]

Hello,

We do not have ready support for mutliple app images. If your design already includes external flash, I recommend relocating your secondary partition to this flash. Is the IMU a standalone separately linked application with its own vector table, or is it going to be linked as part of the main application? If it is the latter, it could make sense to have a look at the QSPI XIP split image implementation to see how you can split the app into two separate memory areas. 

https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/app_dev/bootloaders_dfu/sysbuild_image_ids.html 

[Anthony Ambuehl]

The IMU firmware gets downloaded to a processor inside the IMU.  It has no linkage with the application. Its similar to modem firmware.

We have external flash, and I will temporarily proceed with using the external flash to reach short term deadlines, but in the long term the end-user application needs the entire flash for the best user experience.

Is there someone at Nordic who can work with me to create a sample with multiple updatable sections?

[Vidar Berg]

Thanks for the clarification. I didn't know bosch had IMUs with their own MCU, so I assumed it was simply a library for the NRF application to process the IMU sensor data.

What configuration will I need to add for mcuboot to be able to update (one-at-a-time) both the application and the ext_fw partition?

This seems like something that should be handled in the application. MCUBoot does not support updating external DFU targets. Or is there a reason you want to do this in the bootloader?

[Anthony Ambuehl]

Well my main reasoning is that mcuboot has the keys and crypto libraries to verify the image, and is trusted to complete the firmware swap correctly.  In my other projects guaranteeing the safety and security of firmware updates was extremely high importance.

Also since this external firmware is loaded during the driver initialization process, it would also be necessary to restart the application regardless.

[Vidar Berg]

Does the IMU have NV storage for the firmware, or does it rely on the nRF to load the FW on every boot? Also, does the IMU perform any validation and activation steps for the FW update it receives from the nRF?