Merged Hex File

[Aftab]

Hello,

Softdevice: 7.0.1, SDK: 16.0, Device: nRF52840

In the production, we want to save time programming the devices. So I'm using following command to combine bootloader, softdevice and app into unified/merged hex file then program it through bootloader. But my device gets stuck in the "DfuTarg" status and reseting puts it again into same state. Please let me know what can go wrong?

@echo off

SET BOOTLD=bootloader.hex
SET APPHEX=app.hex
SET SOFTDV=s140_nrf52_7.0.1_softdevice.hex

echo "## Merging SD, bootloader and app files"
mergehex -m %BOOTLD% %SOFTDV% %APPHEX% -o complete_file.hex
echo.

echo "## Erasing complete chip..."
nrfjprog --family nRF52 --eraseall
echo.

echo "## Programming existing merged file"
nrfjprog --program complete_file.hex --chiperase
echo.


echo "## Making device to reset"
nrfjprog --reset
echo.

:end
pause

[Vidar Berg]

Hello,

You need to generate and merge the Bootloader settings page as well. The settings page contains the information needed by the bootloader to verify and boot the application.

Here's an example of how you can generate it with nrfutil:

 nrfutil settings generate --family NRF52^
 --application %APPHEX%^
 --application-version-string "%APP_VERSION_STRING%"^
 --bootloader-version %BL_VERSION%^
 --bl-settings-version 2^
 --app-boot-validation VALIDATE_GENERATED_CRC^
 bl_settings.hex

[Aftab]

I tried this, created bl_settings.hex file but still the issue remains same. What should be the BL_VERSION or bootloader version value should be? I have taken the bootloader from SDk16.0 secure bootloader example.

[Vidar Berg]

Did you use pass the same %APPHEX% file as the one you used in the merged image? The bootloader will only boot the application image if it its computed CRC is the same as the one that is stored in the bootloader settings. You could also try to replace VALIDATE_GENERATED_CRC with NO_VALIDATION to skip the boot validation check and see if it makes any difference.

The Bootloader versioning is up to you to decide. You can start with version 1 if you want.

[Aftab]

The %APPHEX% is defined only once and same is used on both occasions.

I tried using NO_VALIDATION instead of VALIDATE_GENERATED_CRC.

The issue remains the same.

[Vidar Berg]

Sorry, I thought you were using the 52832, not the nrf52840. The "--family" argument must be set to NRF52840 instead of NRF52 then.

[Aftab]

Nop, this change did not work as well. 

[Vidar Berg]

Ok, I'm not sure if the problem is related to the Settings page then. Does the application run ok if you upload it through DFU instead of programming it directly with the debugger?

[Aftab]

Yes, the same app.hex works with same softdevice and bootloader. The only caveat is that the device needs to be power cycled after DFU update. The application, then runs normally. 

In the above case, the device remains in DFU mode no matter how many times it's power cycled.