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

[lcj]

I have been working with some code for a nrf5340 DK and now want to add a custom board to the project as an additional build configuration, but I need to now pull out configurations which are set in the prj.conf as they conflict. For example the dk uses a st7789 display and the custom board uses a gc9a01. In my prj.conf I have CONFIG_ST7789V=y which now should not be in the prj.conf but a specific conf for the configured DK.

I had the dk overlay in the root directory. Do I create another directory under boards for my specific configuration of the DK and create a .conf file for it? Will that make it get automatically picked up? Since it's a nrf5340 dk, should I name the directory something else as not to conflict with the existing structure? By naming the conf file the same as the overlay (just different extension, conf vs overlay) does that mean it will get picked up? By putting the overlay in a different directory and referencing it in the build, does zephry know to look for a corresponding conf file automatically? 

This might be simple, but I haven't found a good explanation of this specific process which a novice like me could consume.

I'm using vs code and nrf connect (2.6) and zephyr.

[Menon]

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

[lcj]

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

1. Prototype on a DK
2. Use an existing custom board
3. 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'

[lcj]

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.