Espressif ESP32-S2 User Manual

Chapter 2. API Reference
API Reference
The API of the USB Host Library is separated into the following header files. However, it is sufficient for applications
to only #include "usb/usb_host.h" and all of USB Host Library headers will also be included.
• usb/include/usb/usb_host.h contains the functions and types of the USB Host Library
• usb/include/usb/usb_helpers.h contains various helper functions that are related to the USB protocol such as
descriptor parsing.
• usb/include/usb/usb_types_stack.h contains types that are are used across multiple layers of the USB Host
stack.
• usb/include/usb/usb_types_ch9.h contains types and macros related to Chapter 9 of the USB2.0 specification
(i.e., descriptors and standard requests).
Header File
• components/usb/include/usb/usb_host.h
Functions
esp_err_t usb_host_install(const usb_host_config_t *config)
Install the USB Host Library.
• This function should only once to install the USB Host Library
• This function should be called before any other USB Host Library functions are called
Return esp_err_t
Parameters
• [in] config: USB Host Library configuration
esp_err_t usb_host_uninstall(void)
Uninstall the USB Host Library.
• This function should be called to uninstall the USB Host Library, thereby freeing its resources
• All clients must have been deregistered before calling this function
• All devices must have been freed by calling usb_host_device_free_all() and receiving the
USB_HOST_LIB_EVENT_FLAGS_ALL_FREE event flag
Return esp_err_t
esp_err_t usb_host_lib_handle_events(TickType_t timeout_ticks, uint32_t *event_flags_ret)
Handle USB Host Library events.
• This function handles all of the USB Host Library’s processing and should be called repeatedly in a loop
• Check event_flags_ret to see if an flags are set indicating particular USB Host Library events
Note This function can block
Return esp_err_t
Parameters
• [in] timeout_ticks: Timeout in ticks to wait for an event to occur
• [out] event_flags_ret: Event flags that indicate what USB Host Library event occurred
esp_err_t usb_host_lib_unblock(void)
Unblock the USB Host Library handler.
• This function simply unblocks the USB Host Library event handling function
(usb_host_lib_handle_events())
Return esp_err_t
esp_err_t usb_host_client_register(const usb_host_client_config_t *client_config,
usb_host_client_handle_t *client_hdl_ret)
Register a client of the USB Host Library.
• This function registers a client of the USB Host Library
• Once a client is registered, its processing function usb_host_client_handle_events() should be called re-
peatedly
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Espressif ESP32-S2 Specifications

General

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