Configuration Options

Introduction

ESP-MDF uses Kconfig system to provide a compile-time configuration mechanism. Kconfig is based around options of several types: integer, string, boolean. Kconfig files specify dependencies between options, default values of the options, the way the options are grouped together, etc.

Applications developers can use make menuconfig build target to edit components’ configuration. This configuration is saved inside sdkconfig file in the project root directory. Based on sdkconfig, application build targets will generate sdkconfig.h file in the build directory, and will make sdkconfig options available to component makefiles.

Using sdkconfig.defaults

When updating ESP-MDF version, it is not uncommon to find that new Kconfig options are introduced. When this happens, application build targets will offer an interactive prompt to select values for the new options. New values are then written into sdkconfig file. To supress interactive prompts, applications can either define BATCH_BUILD environment variable, which will cause all prompts to be suppressed. This is the same effect as that of V or VERBOSE variables. Alternatively, defconfig build target can be used to update configuration for all new variables to the default values.

In some cases, such as when sdkconfig file is under revision control, the fact that sdkconfig file gets changed by the build system may be inconvenient. The build system offers a way to avoid this, in the form of sdkconfig.defaults file. This file is never touched by the build system, and must be created manually. It can contain all the options which matter for the given application. The format is the same as that of the sdkconfig file. Once sdkconfig.defaults is created, sdkconfig can be deleted and added to the ignore list of the revision control system (e.g. .gitignore file for git). Project build targets will automatically create sdkconfig file, populated with the settings from sdkconfig.defaults file, and the rest of the settings will be set to their default values. Note that when make defconfig is used, settings in sdkconfig will be overriden by the ones in sdkconfig.defaults.

Configuration Options Reference

Subsequent sections contain the list of available ESP-MDF options, automatically generated from Kconfig files. Note that depending on the options selected, some options listed here may not be visible by default in the interface of menuconfig.

By convention, all option names are upper case with underscores. When Kconfig generates sdkconfig and sdkconfig.h files, option names are prefixed with CONFIG_. So if an option ENABLE_FOO is defined in a Kconfig file and selected in menuconfig, then sdkconfig and sdkconfig.h files will have CONFIG_ENABLE_FOO defined. In this reference, option names are also prefixed with CONFIG_, same as in the source code.

Customisations

when the Kconfig tool generates Makefiles (the auto.conf file) its behaviour has been customised. In normal Kconfig, a variable which is set to “no” is undefined. In MDF’s version of Kconfig, this variable is defined in the Makefile but has an empty value.

(Note that ifdef and ifndef can still be used in Makefiles, because they test if a variable is defined and has a non-empty value.)

When generating header files for C & C++, the behaviour is not customised - so #ifdef can be used to test if a boolean config item is set or not.