Multiple ESP32 targets - the future for the Espruino Build structure

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when building for multile targets how can the idf.py parameter called -SDKCONFIG_DEFAULTS simplify the application structure

The idf.py parameter --sdkconfig-defaults can simplify the application structure when building for multiple targets by allowing you to maintain a base configuration that's shared across all targets, while still accommodating target-specific configurations. This approach reduces redundancy and keeps your project organized.

How --sdkconfig-defaults Works

The --sdkconfig-defaults option in idf.py allows you to specify one or more files that contain default configuration options. These files are used as a base when generating the final sdkconfig file for the build. You can layer multiple configuration files on top of each other, enabling you to define a base configuration that's common across all targets and then overlay target-specific settings.

Simplified Application Structure

Here's how you can use --sdkconfig-defaults to simplify your project structure:

1. Base Configuration for Common Settings

Create a common configuration file, say sdkconfig.defaults, that includes all the settings that are common across all targets.

Example sdkconfig.defaults:

   CONFIG_FREERTOS_UNICORE=n
   CONFIG_PARTITION_TABLE_SINGLE_APP=y
   CONFIG_EXAMPLE_WIFI_SSID="MySSID"
   CONFIG_EXAMPLE_WIFI_PASSWORD="MyPassword­"

2. Target-Specific Configuration Files

For each target, create a separate configuration file that includes only the settings specific to that target.

Example sdkconfig.esp32:

   CONFIG_IDF_TARGET_ESP32=y
   CONFIG_ESP32_WIFI_STATIC_RX_BUFFER_NUM=1­0

Example sdkconfig.esp32s2:

   CONFIG_IDF_TARGET_ESP32S2=y
   CONFIG_ESP32S2_WIFI_STATIC_RX_BUFFER_NUM­=12

Example sdkconfig.esp32c3:

   CONFIG_IDF_TARGET_ESP32C3=y
   CONFIG_ESP32C3_WIFI_STATIC_RX_BUFFER_NUM­=8

3. Building with --sdkconfig-defaults

When you build for a specific target, you specify both the common defaults and the target-specific configuration file. This allows the build system to generate an sdkconfig that combines both configurations.

Example for ESP32:

   idf.py set-target esp32
   idf.py build --sdkconfig-defaults sdkconfig.defaults --sdkconfig-defaults sdkconfig.esp32

Example for ESP32-S2:

   idf.py set-target esp32s2
   idf.py build --sdkconfig-defaults sdkconfig.defaults --sdkconfig-defaults sdkconfig.esp32s2

Example for ESP32-C3:

   idf.py set-target esp32c3
   idf.py build --sdkconfig-defaults sdkconfig.defaults --sdkconfig-defaults sdkconfig.esp32c3

Benefits

• Reduced Redundancy: Common settings are centralized in sdkconfig.defaults, reducing the need to duplicate them across multiple target-specific sdkconfig files.
  
• Cleaner Project Structure: Your project remains organized with clearly defined configuration files for common and target-specific settings.
  
• Easier Maintenance: When you need to change a common setting, you only need to update sdkconfig.defaults, and the change will automatically apply to all targets.
  
• Flexibility: You can easily add new targets by creating a new target-specific configuration file and using it with the existing base configuration.
  
  

Example Directory Structure with --sdkconfig-defaults

my_project/
├── CMakeLists.txt
├── main/
│   ├── CMakeLists.txt
│   ├── main.c
├── components/
│   ├── component1/
│   │   ├── CMakeLists.txt
│   │   ├── component_code.c
│   └── component2/
│       ├── CMakeLists.txt
│       ├── ...
├── sdkconfig.defaults        # Common settings
├── sdkconfig.esp32           # ESP32-specific settings
├── sdkconfig.esp32s2         # ESP32-S2-specific settings
├── sdkconfig.esp32c3         # ESP32-C3-specific settings
└── CMakeLists.txt

By using --sdkconfig-defaults, you streamline the process of managing configurations across multiple targets while keeping your project tidy and maintainable.