NRFConnect MCUBoot Serial DFU not building

[BDA]

I am trying to build an application with Visual Studio Code using the nRF Connect SDK 1.7.1.  I want to use MCUBoot and have it configured for a Serial DFU.  I've modified my project's prj.conf file to include this line:

CONFIG_BOOTLOADER_MCUBOOT=y

and I do see that MCUBoot is now compiled in and runs prior to branching to my test application.  However, the serial DFU is not working; printing log statements inside the "#ifdef CONFIG_MCUBOOT_SERIAL" section of code makes it clear that that #define is missing.  I tried adding this line to my prj.conf:

CONFIG_MCUBOOT_SERIAL=y

But this results in compiler error for the prj.conf file:

prj.conf:2: warning: attempt to assign the value 'y' to the undefined symbol MCUBOOT_SERIAL

What is the correct way to enable serial DFU for an MCUBoot based project?

[BDA]

Ah.  I put CONFIG_MCUBOOT_SERIAL=y in the bootloader\mcuboot\boot\zephyr\prj.conf file directly and it works now.

[ovrebekk]

Hi Brendan

Good to hear you found a solution. 

In order to change the mcuboot configuration you can also set up a child_image folder in your project, so you don't have to change the configuration in the mcuboot folder directly. 

This is explained in Jimmy Wong's DFU blog, just search for "child_image" in the text:
https://jimmywongiot.com/2021/05/26/overview-on-mcuboot-zephyr-rtos/

Best regards
Torbjørn