Espressif ESP32-S2 User Manual

Chapter 2. API Reference
Initialization functions never store the pointer to the configuration structure, so it is safe to allocate the structure on
the stack.
The application must initialize all fields of the structure. The following is incorrect:
esp_timer_create_args_t my_timer_args;
my_timer_args.callback = &my_timer_callback;
/* Incorrect! Fields .arg and .name are not initialized */
esp_timer_create(&my_timer_args, &my_timer);
Most ESP-IDF examples use C99 designated initializers for structure initialization, since they provide a concise way
of setting a subset of fields, and zero-initializing the remaining fields:
const esp_timer_create_args_t my_timer_args = {
.callback = &my_timer_callback,
/* Correct, fields .arg and .name are zero-initialized */
};
C++ language doesn’t support the designated initializers syntax until C++20, however GCC compiler partially
supports it as an extension. When using ESP-IDF APIs in C++ code, you may consider using the following pattern:
esp_timer_create_args_t my_timer_args = {};
/* All the fields are zero-initialized */
my_timer_args.callback = &my_timer_callback;
Default initializers
For some configuration structures, ESP-IDF provides macros for setting default values of fields:
httpd_config_t config = HTTPD_DEFAULT_CONFIG();
/* HTTPD_DEFAULT_CONFIG expands to a designated initializer.
Now all fields are set to the default values.
Any field can still be modified: */
config.server_port = 8081;
httpd_handle_t server;
esp_err_t err = httpd_start(&server, &config);
It is recommended to use default initializer macros whenever they are provided for a particular configuration structure.
2.7.3 Private APIs
Certain header files in ESP-IDF contain APIs intended to be used only in ESP-IDF source code, and not by the appli-
cations. Such header files often contain private or esp_private in their name or path. Certain components,
such as hal only contain private APIs.
Private APIs may be removed or changed in an incompatible way between minor or patch releases.
2.7.4 Components in example projects
ESP-IDF examples contain a variety of projects demonstrating usage of ESP-IDF APIs. In order to reduce code
duplication in the examples, a few common helpers are defined inside components that are used by multiple examples.
This includes components located in common_components directory, as well as some of the components located in
the examples themselves. These components are not considered to be part of the ESP-IDF API.
It is not recommended to reference these components directly in custom projects (via EXTRA_COMPONENT_DIRS
build system variable), as they may change significantly between ESP-IDF versions. When starting a new project
based on an ESP-IDF example, copy both the project and the common components it depends on out of ESP-IDF,
and treat the common components as part of the project. Note that the common components are written with examples
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Espressif ESP32-S2 Specifications

General

Brand	Espressif
Model	ESP32-S2
Category	Single board computers
Language	English