How do I add another board and .conf file to an existing project?

RE: How do I add another board and .conf file to an existing project?

Menon — Mon, 24 Mar 2025 14:26:55 GMT

Hello,

prj.conf can be used to enable the configurations necessary for both boards, and you can place board-specific configs inside the boards folder. For example, see the project structure below.

my_project/
│── boards/
│   ├── spi_board.conf        
│   ├── qspi_board.conf      
│   ├── spi_board.overlay     
│   ├── qspi_board.overlay    
│── build/
│   ├── spi_board/    
│   ├── qspi_board/   
│── src/
│   ├── main.c
│── CMakeLists.txt
│── prj.conf  #(common config for both boards)

Take a look at the Zigbee light bulb sample to see how different configurations are used for different DKs. Also, check the boards folder here.

Kind Regards,

Abhijith

RE: How do I add another board and .conf file to an existing project?

lcj — Wed, 19 Mar 2025 12:51:29 GMT

In the directory you only have one prj.conf. What if one board uses QSPI and the other uses SPI and I want to enable them. Don't I need two prj.conf files, one for each board?

The SPI board needs this in the prj.conf file:

CONFIG_SPI=y
CONFIG_SPI_NOR=y

and the QSPI board needs this:

CONFIG_NORDIC_QSPI_NOR=y

Both of these I would set in a prj.conf file if I had seperate projects for each board, but if I had the same project for both boards wouldn't I need 3 configuration files:

one for both boards (prj.conf) where the configurations are the same
one for the SPI flash board
one for the QSPI flash board

Is this the way it works? How would I name them and where would I put them?

RE: How do I add another board and .conf file to an existing project?

Menon — Mon, 13 May 2024 12:51:12 GMT

Hello,

I am not sure if I understand you correctly, but you can create a project structure that includes different build configurations for each board. Something like below will be a project structure for two different boards:

project_folder
    - board_1
        - inc
            - *.h files
        - src
            -*.c files (including main.c)
        - CMakeLists.txt
        - board_1.overlay
        - prj.conf
    - board_2
        - inc
            - *.h files
        - src
            -*.c files (including main.c)
        - CMakeLists.txt
        - board_2.overlay
        - prj.conf
    - CMakeLists.txt
    - KConfig
    - prj.conf

In this structure, each board has its own directory with its own source files, header files, CMakeLists.txt, overlay file, and configuration file. The overlay file allows you to specify different settings for each build. You can specify which overlay file to use during the build configuration process using the -DDTS_OVERLAY_FILE argument. See the section on configuration files, which discusses selecting different configuration and overlay files. See the below devzone threads.

https://devzone.nordicsemi.com/support-private/support/301462

https://devzone.nordicsemi.com/support-private/support/305501

Kind Regards,

Abhijith

RE: How do I add another board and .conf file to an existing project?

lcj — Fri, 26 Apr 2024 12:19:12 GMT

The Dev Academy coverage on creating custom boards is great, btw, but I would love a little more depth on this topic. What would help me is the file structure for a project with multiple builds, each one targeting a different board. One board would be the DK with some peripheral attached, like a display, for a prototype. The second one would be a custom board, as discussed in the Dev Academy scenario.

It would show how the an overlay and conf file for each option along with a prj.conf. As the Dev Academy coverage of a custom board shows, there would be a conf and overlay file created in the custom board directory.

For the prototype DK the overlay default seems to be in the root and I don't know where the conf file is. When you create a new project the conf file is the prj.conf, but when you add the 2nd board, a customized board in this case, where do you put the settings for the original board if you need to pull them out of the prj.conf?

I read the link on configuration and tried to replicate, but a visual of the directory structure would be super helpful. I'm assuming the prj.conf would be merged with the prototype/dk board when that build is selected and merged with the custom board when that is selected. I just haven't been able to get it to work.

RE: How do I add another board and .conf file to an existing project?

lcj — Sun, 21 Apr 2024 12:26:11 GMT

I went through the tutorial. It was very helpful. I still am left with questions. I see three scenarios I need to support:

Prototype on a DK
Use an existing custom board
Create my own custom board

My question is moving from scenario 1 to 2 I need to alter the configuration to support both. There are some things I have in the prj.conf which I put in there to support the DK, which I still want to support. However, they also conflict with the existing custom board configuration, such as the display (ST7789 on the prototype and GC9A01A on the custom board). Therefore, the current setting of CONFIG_ST7789V=y in the prj.conf needs to be moved out into a configuration file which is only used if the nrf5340dk is used.

It seems like the prj.conf should be used for any configuration required for all board configurations (in this example dk, existing custom, personal custom). There are custom configuration options in the existing custom board, but I should not mess with too many of them. So how do I have a configuration file for each of the three scenarios above? A board specific configuration I can control. It may only be required for the first one but in that case should not be in the prj.conf. So where does it go and what is it named?

I referenced this link in my previous reply which I believe means that a file in the application root named:
prj_nrf5340dk_nrf5340_cpuapp.conf

I believe it would get incorporated, but the language is hard to decipher:

2. Otherwise, prj_<BOARD>.conf is used if it exists in the application configuration directory.

Does that mean it gets merged as "otherwise" seems to imply it's used in place of the prj.conf.

When I add the prj_nrf5340dk_nrf5340_cpuapp.conf I didn't see it merge when building. I see no reference to it but I do se:

Loaded configuration '/opt/nordic/ncs/v2.5.2/zephyr/boards/arm/nrf5340dk_nrf5340/nrf5340dk_nrf5340_cpuapp_defconfig'
Merged configuration '/Users/lj/Projects/GitHub/lj/xprototype/prj.conf'

RE: How do I add another board and .conf file to an existing project?

Menon — Wed, 17 Apr 2024 08:59:17 GMT

Hello,

In our Developer Academy tutorial, there is a chapter explaining how to add custom board support to the nRF Connect SDK. You can find exercises on creating new board definitions and hardware specifications.

Kind Regards,

Abhijith

RE: How do I add another board and .conf file to an existing project?

lcj — Tue, 16 Apr 2024 12:29:08 GMT

Ok. These are good links. Thank you. I do need to understand the process more completely and will read through them. I don't know if what I'm doing is considered a child image.

The second link includes coverage of _deconfig, which may be an option, but it's not really in the overlay is not in the boards directory because I'm using a DK. The third link covers the overlay, which is what I'm using. I suppose it's a legitimate question to ask if I am creating a prototype using a nrf5340 dk, do I create a directory in boards if I'm going to test on other similar boards, as I am doing now and evolve the prototype into a custom board.

For one build I have a nrf5340dk_nrf5340_cpuapp.overlay in the root and I was wondering if I created a nrf5340dk_nrf5340_cpuapp.conf in root if it would get merged with the prj.conf. This way the CONFIG_ST7789V=y line could be moved out of the prj.conf and into the nrf5340dk_nrf5340_cpuapp.conf and not interfere with the configuration of the 2nd build.

I will need to know how to create a custom board, but I built my code on a dk with a certain configuration and am now trying to see if it works on board somebody else built.

This link which you provided seemed the most helpful. I think this falls into the application configuration category. Maybe I need to do #2 "Otherwise, prj_<BOARD>.conf is used if it exists in the application configuration directory.", if the application configuration directory is the root with the prj.conf in it.

I read How to Optimize Zephyr Configuration and Overlays which was helpful as well.

RE: How do I add another board and .conf file to an existing project?

Hieu — Tue, 16 Apr 2024 07:07:56 GMT

Hi lcj,

For the specific purpose of setting up Devicetree and Kconfig for some specific boards, please check out the Permanent configuration changes to child images in this page: Multi-image builds — nRF Connect SDK 2.6.0 documentation (nordicsemi.com).
Even though you might not be using Multi-image build, it describes how use <board>.conf and <board>.overlay files to achieve what you want.
Almost all projects will want to use DFU, at which point, you will have Multi-image build anyway.

For how to use some generic Devicetree and Kconfig files that are only used in certain builds, please refer to these links:
Setting Kconfig configuration values — Zephyr Project documentation (nRF Connect SDK) (nordicsemi.com)
Devicetree HOWTOs — Zephyr Project documentation (nRF Connect SDK) (nordicsemi.com)

For all the links above, if time allows, I recommend giving their entire parent topic a read, not just the specific sections I linked.

Hieu