Configuring nRF Connect examples

The nRF Connect example applications all come with a default configuration for building. Check the information on this page if you want to modify the application configuration or add new functionalities to build your own application based on the provided example. This page also contains information about the configuration structure, which can be useful to better understand the building process.

Configuring application

Changing the default application configuration can be done either temporarily or permanently. Changing configuration temporarily is useful for testing the impact of changes on the application behavior. Making permanent changes is better if you want to develop your own application, as it helps avoid repeating the configuration process.

Temporary changes to configuration

You can change the configuration temporarily by editing the .config file in the build/zephyr/ directory, which stores all configuration options for the application generated as a result of the build process. As long as you do not remove the current build directory or delete this file, your changes will be kept. However, if you do a clean build, your changes are gone, so it is not possible to save changes permanently this way.

Complete the following steps:

  1. Build the application by typing the following command in the example directory, with build-target replaced with the build target name of the kit, for example nrf52840dk_nrf52840:

     $ west build -b build-target
  2. Run the terminal-based interface called menuconfig by typing the following command:

     $ west build -t menuconfig

    The menuconfig terminal window appears, in which you can navigate using arrow keys and other keys, based on the description at the bottom of the window.

  3. Make the desired changes by following the menuconfig terminal instructions.

  4. Press Q to save and quit.

  5. Rebuild the application.

At this point, the configuration changes are applied to the output file and it can be flashed to the device.

Permanent changes to configuration

The permanent solution is based on modifying the Kconfig configuration files, which are used as components of the building process. This makes the changes persistent across builds.

The best practice to make permanent changes is to edit the main application configuration file prj.conf, which is located in the example directory. This will result in overriding the existing configuration values.

This method is valid for the majority of cases. If you are interested in understanding the big picture of the configuration process, read the Configuration structure overview section below.

Assigning values to Kconfig options

Assigning value to a configuration option is done by typing its full name preceded by the CONFIG_ prefix, and adding the = mark and the value.

Configuration options have different types and it is only possible to assign them values of proper type. Few examples:

  • Assigning logical boolean true value to the option: CONFIG_SAMPLE_BOOLEAN_OPTION=y

  • Assigning numeric integer 1234 value to the option: CONFIG_SAMPLE_INTEGER_OPTION=1234

  • Assigning text string “some_text” value to the option: CONFIG_SAMPLE_STRING_OPTION="some_text"

For more detailed information, read about setting Kconfig values in the nRF Connect SDK documentation.

Because Kconfig configuration files are used in the building process, make sure that you rebuild your application after editing them by typing the following command in the example directory, with build-target replaced with the build target name of the kit, for example nrf52840dk_nrf52840:

    $ west build -b build-target

Configuration structure overview

Zephyr RTOS and related software components, like drivers and libraries, provide a set of Kconfig files which define available configuration options and assign them default values for any application.

The application configuration is specified using Kconfig configuration files (*.conf), where available Kconfig options can be used and their default values overrided. Typically, there are many files having impact on the final configuration shape.

There is no need to modify all these files separately. See the following list for types of files you can find in the project and which of them are important from your perspective:

  • Build target configuration files. These are hardware-platform-dependent configuration files, which are automatically included based on the compilation build target name. They contain configuration for the kit and its peripherals.

  • Project configuration file. Every example application has its main configuration file called prj.conf that is located in the example directory. This file contains application-specific configuration or the most frequently changed options. Almost every configuration can be overridden in this file and probably this file is the most important one.

  • Overlays. Overlays are optional files usually used to extract configuration for some specific case or feature from the general application configuration. The main difference between them and the application prj.conf file is that they are not included automatically, so you can decide whether to build sample with or without them. Overlay files can be added to build by typing the following command in the example directory, with build-target replaced with the build target name (e.g. nrf52840dk_nrf52840) and overlay_file_name replaced with the overlay configuration file name (e.g. overlay-usb_support.conf):

      $ west build -b build-target -- -DOVERLAY_CONFIG=overlay_file_name

Read the Kconfig guide in the nRF Connect SDK’s Zephyr documentation if you are interested in getting more advanced and detailed information about the configuration structure.