Usage of "custom_board.h" and "app_config.h" files in external project

[Sharon Vardi]

Hi,

In my project I'm working with a nrf52840 SoC and developing an application based on you'r SDK.

I would like to understand the proper way of using the "custom_board.h" and "app_config.h" files. if I understood correctly:

• I don't need to have a "sdk_config.h" file because according to the board type I'm using (in my case nrf52840) the compiler knows which sdk_config.h file he needs to compile from the variant of "sdk_config.h" files he has in its repository.
• If I want to override some of the default nrf52840 application configuration specified in the nrf52840 "sdk_config.h" file I need to:
  1. create an "app_config.h" file with the same attributes from the "sdk_config.h" file that I wish to change (but with the values that I want for my project).
  2. add the 'USE_APP_CONFIG' definition to the "c_preprocessor_definition" attribute in the Segger .emProject file
     That way the compiler will include all the content of my "app_config.h" file before the "sdk_config.h" file and my application definitions will preserve.
• I don't need to have a "custom_boards.h" file if the nrf52840 pin-map assignemnt works for me.
• If my board needs a different pin-map assignment than I need to:
  1. add the 'BOARD_CUSTOM' definition  to the "c_preprocessor_definition" attribute in the Segger .emProject file
  2. create a "custom_board.h" file which overrides the default bsp configurations mentioned in "board.h" file
     That way the compiler will include the content of the "custom_board.h" file before the "boards.h" file content and my board configurations will preserve
     

Is what I said here is correct?
thank you very much for your help.

[Kazi Afroza Sultana]

Hello,

You are almost correct. But it seems a bit unorganized for some steps. 

There is some relevant information you can follow:

This shows how to use configuration header file https://docs.nordicsemi.com/bundle/sdk_nrf5_v17.1.0/page/sdk_config.html.

and about custom board here (if he wants to use the BSP). https://docs.nordicsemi.com/bundle/sdk_nrf5_v17.1.0/page/sdk_for_custom_boards.html

We recommend not to use app_config.h as having two config files in a hierarchy only adds to complexity (adding extra layer) without giving any benefits in most cases. You can do changes in the sdk_config.h file instead. 

 Regarding custom board, it is better to create a board file even though your board configuration is as same as nordic board. According to the documentation (custom board one), it is recommended to start with the board file for a DK with the same chip and modify that as needed to match your custom board.

Thanks.

BR

Kazi

 

[Sharon Vardi]

But if my app_config.h file consist of several sonfiguration which are not to be found in the nrf52840 sdk_config.h file and other over-written configurations why would it be more complex to use it that way?

It seems simpler for me as a developer to use a specific configuration file (app_config.h) with all the relevant configurations or my project and it is un-attached to any HW sdk_config.h file (more flexible design) 

[Kazi Afroza Sultana]

Because the system is so you can have a sdk:config.h and a app_config.h file. But as we said before app_config.h will add extra layer.