esp-idf/examples/build_system/cmake/multi_config

Multiple Build Configurations Example

(See the README.md file in the upper level 'examples' directory for more information about examples.)

This example demonstrates how to build multiple configurations of a single application. This can be useful in the following cases:

• Building binaries for multiple similar products from single codebase
• Building the application for development or production hardware
• Optimizing the application differently for development and production

This example contains three build configurations:

• Development configuration, described by sdkconfig.defaults file. This configuration is used by default if the application is built using idf.py build.
• Production configuration for product 1 ("Blinky Smart Light"), described in sdkconfig.prod1 file. This configuration is not built by default, however it can be built as shown in the next section. It is used together sdkconfig.prod_common, common configuration file for all products.
• Production configuration for product 2 ("Blinky Smart Switch"), described in sdkconfig.prod2 file. Differs from prod1 configuration only in product name.

For each configuration, a few configuration options are set:

• Project-specific Kconfig options, CONFIG_EXAMPLE_PRODUCT_NAME and CONFIG_EXAMPLE_FUNC_IMPL. These options are declared in component Kconfig.projbuild. These are used to demonstrate how to create and set project-specific options. These options are set differently in sdkconfig.defaults and sdkconfig.prod_common files.
  • CONFIG_EXAMPLE_PRODUCT_NAME is a simple string option. It is used to set the product name.
  • CONFIG_EXAMPLE_FUNC_IMPL is a choice option. It is used to select which of the two source files, func_dev.c or func_prod.c, is compiled and linked. See component CMakeLists.txt file for related logic.
• ESP-IDF configuration options, CONFIG_COMPILER_OPTIMIZATION_SIZE, CONFIG_BOOTLOADER_LOG_LEVEL_NONE, CONFIG_LOG_DEFAULT_LEVEL_NONE are set in sdkconfig.prod_common to illustrate a typical production configuration where log messages are disabled and optimization for size is used.

How to Use Example

Development build

In this example, Development configuration is specified in sdkconfig.defaults, so it is the default one. You can build the project as usual:

idf.py build

To flash the project and see the output, run:

idf.py -p PORT flash monitor

(To exit the serial monitor, type Ctrl-].)

Production build

To build one of the Production configurations, specify a different build directory and SDKCONFIG_DEFAULTS file. For example, to build prod1 configuration:

idf.py -B build_prod1 -D SDKCONFIG_DEFAULTS="sdkconfig.prod_common;sdkconfig.prod1" build

• -B build_prod1 sets the build directory to build_prod1
• -D SDKCONFIG_DEFAULTS="sdkconfig.prod_common;sdkconfig.prod1" selects sdkconfig.prod_common and sdkconfig.prod1 files to be used for creating app configuration (sdkconfig), instead of the usual sdkconfig.defaults. See the section below on how these two default configuration files are combined.

To flash the project and see the output, run:

idf.py -B build_prod1 -p PORT flash monitor

Note that it is not necessary to repeat -D SDKCONFIG_DEFAULTS=... option once the build directory has been created and sdkconfig file generated. For example, to build the project again, run:

idf.py -B build_prod1 build

To build and run the app with prod2 configuration, repeat the steps above, replacing prod1 with prod2.

Combining multiple files in SDKCONFIG_DEFAULTS

SDKCONFIG_DEFAULTS build system variable selects the file which contains the default app configuration, used when no sdkconfig file is present. If not specified, SDKCONFIG_DEFAULTS is set to "sdkconfig.defaults".

SDKCONFIG_DEFAULTS can be set to a different name from the command line, using -D flag of idf.py, as shown above. It can also be set from the project CMakeLists.txt file, before project.cmake is included.

It is possible to specify multiple files in this variable, separating them with semicolons. In the example given in the previous section, this is used to create a common config file for production builds and product-specific config files:

• product 1: sdkconfig.prod_common;sdkconfig.prod1
• product 2: sdkconfig.prod_common;sdkconfig.prod2

This way the common options do not need to be repeated in each of sdkconfig.prodN files.

Generated sdkconfig file

In this example, sdkconfig file is placed into the build directory, instead of the project root directory as it is done by default. This allows development and production builds to exist side by side. The location of sdkconfig file is set using SDKCONFIG variable in project CMakeLists.txt file.

Example Output

Development build output

I (310) cpu_start: Starting scheduler on PRO CPU.
I (0) cpu_start: Starting scheduler on APP CPU.
This app is built for running on: Blinky Development Board
func() from func_dev.c (Development) called.
See README.md for building and running other app configurations.

Production build output

When building with -DSDKCONFIG_DEFAULTS="sdkconfig.prod_common;sdkconfig.prod1" option:

This app is built for running on: Blinky Smart Light
func() from func_prod.c (Production) called.
See README.md for building and running other app configurations.

When building with -DSDKCONFIG_DEFAULTS="sdkconfig.prod_common;sdkconfig.prod2" option:

This app is built for running on: Blinky Smart Switch
func() from func_prod.c (Production) called.
See README.md for building and running other app configurations.