Espressif ESP32-S2 User Manual

Chapter 2. API Reference
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// 5. Unregistering an unneeded handler
esp_event_handler_unregister_with(loop_handle, MY_EVENT_BASE, MY_EVENT_ID, run_
,→on_event);
...
// 6. Deleting an unneeded event loop
esp_event_loop_delete(loop_handle);
}
Declaring and defining events
As mentioned previously, events consists of two-part identifers: the event base and the event ID. The event base
identifies an independent group of events; the event ID identifies the event within that group. Think of the event base
and event ID as a person’s last name and first name, respectively. A last name identifies a family, and the first name
identifies a person within that family.
The event loop library provides macros to declare and define the event base easily.
Event base declaration:
ESP_EVENT_DECLARE_BASE(EVENT_BASE)
Event base definition:
ESP_EVENT_DEFINE_BASE(EVENT_BASE)
Note: In IDF, the base identifiers for system events are uppercase and are postfixed with _EVENT. For example,
the base for wifi events is declared and defined as WIFI_EVENT, the ethernet event base ETHERNET_EVENT, and
so on. The purpose is to have event bases look like constants (although they are global variables considering the
defintions of macros ESP_EVENT_DECLARE_BASE and ESP_EVENT_DEFINE_BASE).
For event ID’s, declaring them as enumerations is recommended. Once again, for visibility, these are typically
placed in public header files.
Event ID:
enum {
EVENT_ID_1,
EVENT_ID_2,
EVENT_ID_3,
...
}
Default Event Loop
The default event loop is a special type of loop used for system events (WiFi events, for example). The handle for
this loop is hidden from the user. The creation, deletion, handler registration/unregistration and posting of events is
done through a variant of the APIs for user event loops. The table below enumerates those variants, and the user
event loops equivalent.
Espressif Systems 836
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Espressif ESP32-S2 Specifications

General

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