Automating merged.hex Patching After Build

[kelk]

Hello Nordic team,

I would like to automatically patch the merged.hex file each time I build my project. I’ve attempted to use extra_post_build in CMakeLists.txt, but my patching script still runs before the merged.hex file is generated.

From what I’ve read here https://devzone.nordicsemi.com/f/nordic-q-a/102010/adding-extra_post_build-step-from-out-of-tree-application, this behavior might be due to the CONFIG_BOOTLOADER_MCUBOOT macro.
Is there an alternative solution or recommended approach to ensure that my patching logic runs after merged.hex is fully created? i am using nrf 5340 and sdk 2.9.0

Thank you in advance!

Best regards,
kelk

[Susheel Nuguru]

Add a condition in your CMakeLists.txt using POST_BUILD for your execution something like below

if (DEFINED CONFIG_BOOTLOADER_MCUBOOT)
  add_custom_command(
    TARGET mergehex
    POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E env PYTHONPATH=${CMAKE_CURRENT_SOURCE_DIR}
            python ${CMAKE_CURRENT_SOURCE_DIR}/scripts/patch_hex.py
            ${CMAKE_BINARY_DIR}/merged.hex
  )
endif()

[kelk]

Hi,

I tested the provided code, but encountered the following error:

CMake Error at CMakeLists.txt:119 (add_custom_command):
  No TARGET 'mergehex' has been created in this directory.

To work around this, I manually added the target using:

add_custom_target(mergehex
--input ${CMAKE_BINARY_DIR}/../merged.hex
)

However, after doing so, the Python script does not get executed.

[Susheel Nuguru]

Sorry for that experience.

Can you please make sure that you have enabled the MCUBoot since this triggers the merged output via imgtool . I tested with this below 

my testing scripts/patch_hex.py contains (you might have different patch_hex.py)

import sys
print(f"Patching {sys.argv[1]} ...")
with open(sys.argv[1], "a") as f:
    f.write("\n# Patched!\n")

Adding below to the CMakeLists.txt

# Run patching script after merged.hex is fully generated
if(CONFIG_BOOTLOADER_MCUBOOT)
  add_custom_command(
    TARGET app
    POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E echo "Running post-build patch on merged.hex..."
    COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/scripts/patch_hex.py
            ${CMAKE_BINARY_DIR}/zephyr/merged.hex
    COMMENT "Post-build: patch_hex.py running after merged.hex is created"
    VERBATIM
  )
endif()

Make sure you do not have any typos. and make sure that CMAKE_CURRENT_SOURCE_DIR and  ${CMAKE_BINARY_DIR}/zephyr/merged.hex exists or replace them with the right directory.

west build -b nrf5340dk/nrf5340/cpuapp -p

should give something like 

Running post-build patch on merged.hex...
Patching build/zephyr/merged.hex ...

[kelk]

Hi,

The commad  is still being executed before the merged files are generated.

[0/24] Performing build step for 'ipc_radio'
ninja: no work to do.
[2/7] Linking C static library app\libapp.a
Running post-build patch on merged.hex...
[7/7] Linking C executable zephyr\zephyr.elf
Memory region Used Size Region Size %age Used
FLASH: 516152 B 916992 B 56.29%
RAM: 243496 B 450544 B 54.04%
IDT_LIST: 0 GB 32 KB 0.00%
Generating files from C:/projects/sw_b/build/sw_b/zephyr/zephyr.elf for board: cpn0003
image.py: sign the digest
image.py: sign the digest
[5/20] Performing build step for 'mcuboot'
ninja: no work to do.
[8/20] Performing build step for 'b0n'
ninja: no work to do.
[18/18] Generating ../merged.hex
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