USB Host

Warning

The USB Host Library API is a beta version thus is subject to change.

The document provides information regarding the USB Host Library. This document is split into the following sections:

Overview

The USB Host Library (hereinafter referred to as the Host Library) is the lowest public facing API layer of the ESP-IDF USB Host Stack. In most cases, applications that require USB Host functionality will not need to interface with the Host Library directly. Instead, most applications will use the API provided by a host class driver that is implemented on top of the Host Library.

However, users may want to use the Host Library directly for some of (but not limited to) the following reasons:

  • The user needs to implement a custom host class driver such as a vendor specific class driver

  • The user has a requirement for a lower level of abstraction due to resource/latency requirements

Features & Limitations

The Host Library has the following features:

  • Supports Full Speed (FS) and Low Speed (LS) Devices

  • Supports all four transfer types (Control, Bulk, Interrupt, and Isochronous)

  • Allows multiple class drivers to run simultaneously (i.e., multiple clients of the Host Library)

  • A single device can be used by multiple clients simultaneously (e.g., composite devices)

  • The Host Library itself (and the underlying Host Stack) does not internally instantiate any OS tasks. The number of tasks are entirely controlled by how the Host Library interface is used. However, a general rule of thumb regarding the number of tasks is (the number of host class drivers running + 1).

Currently, the Host Library (and the underlying Host Stack) has the following limitations:

  • Only supports a single device, but the Host Library’s API is designed for multiple device support.

  • Only supports Asynchronous transfers

  • Transfer timeouts are not supported yet

Architecture

Diagram of the Key Entities of USB Host Functionality

Diagram of the key entities involved in USB Host functionality

The diagram above shows the key entities that are involved when implementing USB Host functionality. These entities are:

  • The Host Library

  • Clients of the Host Library

  • Devices

  • Host Library Daemon Task

Host Library

The Host Library is the a lowest public facing layer of the USB Host Stack. Any other IDF component (such as a class driver or a user component) that needs to communicate with a connected USB device can only do so using the Host Library API either directly or indirectly.

The Host Library’s API is split into two sub-sets, namely the Library API and Client API.

  • The Client API handles the communication between a client of the Host Library and one or more USB devices. The Client API should only be called by registered clients of the Host Library.

  • The Library API handles all of the Host Library processing that is not specific to a single client (e.g., device enumeration). Usually, the library API is called by a Host Library Daemon Task.

Clients

A client of the Host Library is a software component (such as a host class driver or user component) that uses the Host Library to communicate with a USB device. Generally each client has a one-to-one relation with a task, meaning that for a particular client, all of its Client API calls should be done from the context of the same task.

By organizing the software components that use the Host Library’s into clients, the Host Library can delegate the handling of all client events (i.e., the events specific to that client) to the client’s task. In other words, each client task is responsible for all the required processing and event handling associated with the USB communication that the client initiates.

Daemon Task

Although the Host Library delegates the handling of client events to the clients themselves, there are still Library events (i.e., events that are not specific to a client) that need to be handled. Library event handling can include things such as:

  • Handling USB device connection, enumeration, and disconnection

  • Rerouting control transfers to/from clients

  • Forwarding events to clients

Therefore, in addition to the client tasks, the Host Library also requires a task (usually the Host Library Daemon Task) to handle all of the library events.

Devices

The Host Library hides the details of device handling (such as connection, memory allocation, and enumeration) from the clients. The clients are provided only with a list of already connected and enumerated devices to choose from. During enumeration, each device is configured to use configuration 1.

It is possible for a two or more clients to simultaneously communicate with the same device as long as they are not communicating to the same interface. However, multiple clients can simultaneously communicate with the same device’s default endpoint (EP0), which will result in their control transfers being serialized.

For a client to communicate with a device, the client must:

  1. Open the device using the device’s address. This lets the Host Library know that the client is using that device.

  2. Claim the interface(s) that will be used for communication. This prevents other clients from claiming the same interface(s).

  3. Send transfers to the endpoints in the claimed interface. The client’s task is responsible for handling its own processing and events.

Usage

The Host Library (and the underlying Host Stack) will not create any tasks. All tasks (i.e., the client tasks and the Daemon Task) will need to be created by the class drivers or the user. Instead, the Host Library provides two event handler functions that will handle all of the required Host Library processing, thus these functions should be called repeatedly from the client tasks and the Daemon Task. Therefore, the implementation of client tasks and the Daemon Task will be the largely centered around the invocation of these event handler functions.

Host Library & Daemon Task

Basic Usage

The Host Library API provides usb_host_lib_handle_events() to handle library events. This function should be called repeatedly, typically from the daemon task. Some notable features regarding usb_host_lib_handle_events() are:

  • The function can block until a library event needs handling

  • Event flags are returned on each invocation. These event flags are useful for knowing when the Host Library can be uninstalled.

A bare-bones Daemon Task would resemble something like the following code snippet:

#include "usb/usb_host.h"

void daemon_task(void *arg)
{
    ...
    bool exit = false;
    while (!exit) {
        uint32_t event_flags;
        usb_host_lib_handle_events(portMAX_DELAY, &event_flags);
        if (event_flags & USB_HOST_LIB_EVENT_FLAGS_NO_CLIENTS) {
            ...
        }
        if (event_flags & USB_HOST_LIB_EVENT_FLAGS_ALL_FREE) {
            ...
        }
        ...
    }
    ...
}

Note

See the peripherals/usb/host/usb_host_lib example for a full implementation of the Daemon Task

Lifecycle

Graph of Typical USB Host Library Lifecycle

Graph of Typical USB Host Library Lifecycle

The graph above illustrates the typical lifecycle of the Host Library with multiple clients and devices. Specifically, the example involves…

  • two registered clients (Client 1 and Client 2)

  • two connected devices (Device 1 and Device 2), where Client 1 communicates with Device 1 and Client 2 communicates with Device 2.

With reference the graph above, the typical lifecycle involves the following key stages.

  1. The Host Library is installed by calling usb_host_install().

    • Installation must be done before any other Host Library API is called.

    • Where usb_host_install() is called (e.g., from the Daemon Task or another task) will depend on the synchronization logic between the Daemon Task, client tasks, and the rest of the system.

  2. Once the Host Library is installed, the clients can be registered by calling usb_host_client_register().

    • This is typically called from the client task (where the client task waits for a signal from the Daemon Task).

    • This can be called elsewhere if necessary as long it is called after usb_host_install().

  3. Device 1 connects and is then enumerated.

    • Each registered client (in this case Client 1 and Client 2) are notified of the new device by way of the USB_HOST_CLIENT_EVENT_NEW_DEV event.

    • Client 1 opens Device 1 and begins communication with it.

  4. Similarly Device 2 connects and is enumerated.

    • Client 1 and 2 are notified of a new device (via a USB_HOST_CLIENT_EVENT_NEW_DEV event).

    • Client 2 opens Device 2 and begins communication with it.

  5. Device 1 suddenly disconnects.
  6. Client 1 completes its clean up and deregisters by calling usb_host_client_deregister().

    • This is typically called from the client task before the task exits.

    • This can be called elsewhere if necessary as long as Client 1 has already completed its clean up.

  7. Client 2 completes its communication with Device 2. Client 2 then closes Device 2 and deregisters itself.

    • The Daemon Task is notified of the deregistration of all clients by way the USB_HOST_LIB_EVENT_FLAGS_NO_CLIENTS event flag as Client 2 is the last client to deregister.

    • Device 2 is still allocated (i.e., not freed) as it is still connected albeit not currently opened by any client.

  8. The Daemon Task decides to cleanup as there are no more clients.

  9. Once the Daemon Task has verified that all clients have deregistered and all devices have been freed, it can now uninstall the Host Library by calling usb_host_uninstall().

Clients & Class Driver

Basic Usage

The Host Library API provides usb_host_client_handle_events() to handle a particular client’s events. This function should be called repeatedly, typically from the client’s task. Some notable features regarding usb_host_client_handle_events() are:

  • The function can block until a client event needs handling

  • The function’s primary purpose is to call the various event handling callbacks when a client event occurs.

The following callbacks are called from within usb_host_client_handle_events() thus allowing the client task to be notified of events.

  • The client event callback of type usb_host_client_event_cb_t which delivers client event messages to the client. Client event messages indicate events such as the addition or removal of a device.

  • The USB transfer completion callback of type usb_transfer_cb_t which indicates that a particular USB transfer previously submitted by the client has completed.

Note

Given that the callbacks are called from within usb_host_client_handle_events(), users should avoid blocking from within the callbacks as this will result in usb_host_client_handle_events() being blocked as well, thus preventing other pending client events from being handled.

The following code snippet demonstrates a bare-bones host class driver and its client task. The code snippet contains:

  • A simple client task function client_task that calls usb_host_client_handle_events() in a loop.

  • Implementations of a client event callback and transfer completion callbacks.

  • Implementation of a simple state machine for the class driver. The class driver simply opens a device, sends an OUT transfer to EP1, then closes the device.

#include <string.h>
#include "usb/usb_host.h"

#define CLASS_DRIVER_ACTION_OPEN_DEV    0x01
#define CLASS_DRIVER_ACTION_TRANSFER    0x02
#define CLASS_DRIVER_ACTION_CLOSE_DEV   0x03

struct class_driver_control {
    uint32_t actions;
    uint8_t dev_addr;
    usb_host_client_handle_t client_hdl;
    usb_device_handle_t dev_hdl;
};

static void client_event_cb(const usb_host_client_event_msg_t *event_msg, void *arg)
{
    //This is function is called from within usb_host_client_handle_events(). Don't block and try to keep it short
    struct class_driver_control *class_driver_obj = (struct class_driver_control *)arg;
    switch (event_msg->event) {
        case USB_HOST_CLIENT_EVENT_NEW_DEV:
            class_driver_obj->actions |= CLASS_DRIVER_ACTION_OPEN_DEV;
            class_driver_obj->dev_addr = event_msg->new_dev.address; //Store the address of the new device
            break;
        case USB_HOST_CLIENT_EVENT_DEV_GONE:
            class_driver_obj->actions |= CLASS_DRIVER_ACTION_CLOSE_DEV;
            break;
        default:
            break;
    }
}

static void transfer_cb(usb_transfer_t *transfer)
{
    //This is function is called from within usb_host_client_handle_events(). Don't block and try to keep it short
    struct class_driver_control *class_driver_obj = (struct class_driver_control *)transfer->context;
    printf("Transfer status %d, actual number of bytes transferred %d\n", transfer->status, transfer->actual_num_bytes);
    class_driver_obj->actions |= CLASS_DRIVER_ACTION_CLOSE_DEV;
}

void client_task(void *arg)
{
    ... //Wait until Host Library is installed
    //Initialize class driver objects
    struct class_driver_control class_driver_obj = {0};
    //Register the client
    usb_host_client_config_t client_config = {
        .is_synchronous = false,
        .max_num_event_msg = 5,
        .async = {
            .client_event_callback = client_event_cb,
            .callback_arg = &class_driver_obj,
        }
    };
    usb_host_client_register(&client_config, &class_driver_obj.client_hdl);
    //Allocate a USB transfer
    usb_transfer_t *transfer;
    usb_host_transfer_alloc(1024, 0, &transfer);

    //Event handling loop
    bool exit = false;
    while (!exit) {
        //Call the client event handler function
        usb_host_client_handle_events(class_driver_obj.client_hdl, portMAX_DELAY);
        //Execute pending class driver actions
        if (class_driver_obj.actions & CLASS_DRIVER_ACTION_OPEN_DEV) {
            //Open the device and claim interface 1
            usb_host_device_open(class_driver_obj.client_hdl, class_driver_obj.dev_addr, &class_driver_obj.dev_hdl);
            usb_host_interface_claim(class_driver_obj.client_hdl, class_driver_obj.dev_hdl, 1, 0);
        }
        if (class_driver_obj.actions & CLASS_DRIVER_ACTION_TRANSFER) {
            //Send an OUT transfer to EP1
            memset(transfer->data_buffer, 0xAA, 1024);
            transfer->num_bytes = 1024;
            transfer->device_handle = class_driver_obj.dev_hdl;
            transfer->bEndpointAddress = 0x01;
            transfer->callback = transfer_cb;
            transfer->context = (void *)&class_driver_obj;
            usb_host_transfer_submit(transfer);
        }
        if (class_driver_obj.actions & CLASS_DRIVER_ACTION_CLOSE_DEV) {
            //Release the interface and close the device
            usb_host_interface_release(class_driver_obj.client_hdl, class_driver_obj.dev_hdl, 1);
            usb_host_device_close(class_driver_obj.client_hdl, class_driver_obj.dev_hdl);
            exit = true;
        }
        ... //Handle any other actions required by the class driver
    }

    //Cleanup class driver
    usb_host_transfer_free(transfer);
    usb_host_client_deregister(class_driver_obj.client_hdl);
    ... //Delete the task and any other signal Daemon Task if required
}

Note

An actual host class driver will likely supported many more features, thus will have a much more complex state machine. A host class driver will likely also need to:

  • Be able to open multiple devices

  • Parse an opened device’s descriptors to identify if the device is of the target class

  • Communicate with multiple endpoints of an interface in a particular order

  • Claim multiple interfaces of a device

  • Handle various errors

Lifecycle

The typical life cycle of a client task and class driver will go through the following stages:

  1. Wait for some signal regarding the Host Library being installed.

  2. Register the client via usb_host_client_register() and allocate any other class driver resources (e.g., allocating transfers using usb_host_transfer_alloc()).

  3. For each new device that the class driver needs to communicate with:

    1. Check if the device is already connected via usb_host_device_addr_list_fill().

    2. If the device is not already connected, wait for a USB_HOST_CLIENT_EVENT_NEW_DEV event from the client event callback.

    3. Open the device via usb_host_device_open().

    4. Parse the device and configuration descriptors via usb_host_get_device_descriptor() and usb_host_get_active_config_descriptor() respectively.

    5. Claim the necessary interfaces of the device via usb_host_interface_claim().

  4. Submit transfers to the device via usb_host_transfer_submit() or usb_host_transfer_submit_control().

  5. Once an opened device is no longer needed by the class driver, or has disconnected (as indicated by a USB_HOST_CLIENT_EVENT_DEV_GONE event):

    1. Stop any previously submitted transfers to the device’s endpoints by calling usb_host_endpoint_halt() and usb_host_endpoint_flush() on those endpoints.

    2. Release all previously claimed interfaces via usb_host_interface_release().

    3. Close the device via usb_host_device_close().

  6. Deregister the client via usb_host_client_deregister() and free any other class driver resources.

  7. Delete the client task. Signal the Daemon Task if necessary.

Examples

Host Library Examples

The peripherals/usb/host/usb_host_lib demonstrates basic usage of the USB Host Library’s API to implement a pseudo class driver.

Class Driver Examples

The USB Host Stack provides a number examples that implement host class drivers using the Host Library’s API.

CDC-ACM

MSC

  • A host class driver for the Mass Storage Class (Bulk-Only Transport) is current implemented as an example found via peripherals/usb/host/msc.

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.

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

Note

If skip_phy_setup is set in the install configuration, the user is responsible for ensuring that the underlying Host Controller is enabled and the USB PHY (internal or external) is already setup before this function is called.

Parameters

config – [in] USB Host Library configuration

Returns

esp_err_t

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

Note

If skip_phy_setup was set when the Host Library was installed, the user is responsible for disabling the underlying Host Controller and USB PHY (internal or external).

Returns

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

  • This function should never be called by multiple threads simultaneously

Note

This function can block

Parameters

  • timeout_ticks – [in] Timeout in ticks to wait for an event to occur

  • event_flags_ret – [out] Event flags that indicate what USB Host Library event occurred.

Returns

esp_err_t

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())

Returns

esp_err_t

esp_err_t usb_host_lib_info(usb_host_lib_info_t *info_ret)

Get current information about the USB Host Library.

Parameters

info_ret – [out] USB Host Library Information

Returns

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 repeatedly

Parameters

  • client_config – [in] Client configuration

  • client_hdl_ret – [out] Client handle

Returns

esp_err_t

esp_err_t usb_host_client_deregister(usb_host_client_handle_t client_hdl)

Deregister a USB Host Library client.

  • This function deregisters a client of the USB Host Library

  • The client must have closed all previously opened devices before attempting to deregister

Parameters

client_hdl – [in] Client handle

Returns

esp_err_t

esp_err_t usb_host_client_handle_events(usb_host_client_handle_t client_hdl, TickType_t timeout_ticks)

USB Host Library client processing function.

  • This function handles all of a client’s processing and should be called repeatedly in a loop

  • For a particular client, this function should never be called by multiple threads simultaneously

Note

This function can block

Parameters

  • client_hdl – [in] Client handle

  • timeout_ticks – [in] Timeout in ticks to wait for an event to occur

Returns

esp_err_t

esp_err_t usb_host_client_unblock(usb_host_client_handle_t client_hdl)

Unblock a client.

  • This function simply unblocks a client if it is blocked on the usb_host_client_handle_events() function.

  • This function is useful when need to unblock a client in order to deregister it.

Parameters

client_hdl – [in] Client handle

Returns

esp_err_t

esp_err_t usb_host_device_open(usb_host_client_handle_t client_hdl, uint8_t dev_addr, usb_device_handle_t *dev_hdl_ret)

Open a device.

  • This function allows a client to open a device

  • A client must open a device first before attempting to use it (e.g., sending transfers, device requests etc.)

Parameters

  • client_hdl – [in] Client handle

  • dev_addr – [in] Device’s address

  • dev_hdl_ret – [out] Device’s handle

Returns

esp_err_t

esp_err_t usb_host_device_close(usb_host_client_handle_t client_hdl, usb_device_handle_t dev_hdl)

Close a device.

  • This function allows a client to close a device

  • A client must close a device after it has finished using the device (claimed interfaces must also be released)

  • A client must close all devices it has opened before deregistering

Note

This function can block

Parameters

  • client_hdl – [in] Client handle

  • dev_hdl – [in] Device handle

Returns

esp_err_t

esp_err_t usb_host_device_free_all(void)

Indicate that all devices can be freed when possible.

  • This function marks all devices as waiting to be freed

  • If a device is not opened by any clients, it will be freed immediately

  • If a device is opened by at least one client, the device will be free when the last client closes that device.

  • Wait for the USB_HOST_LIB_EVENT_FLAGS_ALL_FREE flag to be set by usb_host_lib_handle_events() in order to know when all devices have been freed

  • This function is useful when cleaning up devices before uninstalling the USB Host Library

Returns

  • ESP_ERR_NOT_FINISHED: There are one or more devices that still need to be freed. Wait for USB_HOST_LIB_EVENT_FLAGS_ALL_FREE event

  • ESP_OK: All devices already freed (i.e., there were no devices)

  • Other: Error

esp_err_t usb_host_device_addr_list_fill(int list_len, uint8_t *dev_addr_list, int *num_dev_ret)

Fill a list of device address.

  • This function fills an empty list with the address of connected devices

  • The Device addresses can then used in usb_host_device_open()

  • If there are more devices than the list_len, this function will only fill up to list_len number of devices.

Parameters

  • list_len – [in] Length of the empty list

  • dev_addr_list – [inout] Empty list to be filled

  • num_dev_ret – [out] Number of devices

Returns

esp_err_t

esp_err_t usb_host_device_info(usb_device_handle_t dev_hdl, usb_device_info_t *dev_info)

Get device’s information.

  • This function gets some basic information of a device

  • The device must be opened first before attempting to get its information

Note

This function can block

Parameters

  • dev_hdl – [in] Device handle

  • dev_info – [out] Device information

Returns

esp_err_t

esp_err_t usb_host_get_device_descriptor(usb_device_handle_t dev_hdl, const usb_device_desc_t **device_desc)

Get device’s device descriptor.

  • A client must call usb_host_device_open() first

  • No control transfer is sent. The device’s descriptor is cached on enumeration

  • This function simple returns a pointer to the cached descriptor

Note

No control transfer is sent. The device’s descriptor is cached on enumeration

Parameters

  • dev_hdl – [in] Device handle

  • device_desc – [out] Device descriptor

Returns

esp_err_t

esp_err_t usb_host_get_active_config_descriptor(usb_device_handle_t dev_hdl, const usb_config_desc_t **config_desc)

Get device’s active configuration descriptor.

  • A client must call usb_host_device_open() first

  • No control transfer is sent. The device’s active configuration descriptor is cached on enumeration

  • This function simple returns a pointer to the cached descriptor

Note

This function can block

Note

No control transfer is sent. A device’s active configuration descriptor is cached on enumeration

Parameters

  • dev_hdl – [in] Device handle

  • config_desc – [out] Configuration descriptor

Returns

esp_err_t

esp_err_t usb_host_interface_claim(usb_host_client_handle_t client_hdl, usb_device_handle_t dev_hdl, uint8_t bInterfaceNumber, uint8_t bAlternateSetting)

Function for a client to claim a device’s interface.

  • A client must claim a device’s interface before attempting to communicate with any of its endpoints

  • Once an interface is claimed by a client, it cannot be claimed by any other client.

Note

This function can block

Parameters

  • client_hdl – [in] Client handle

  • dev_hdl – [in] Device handle

  • bInterfaceNumber – [in] Interface number

  • bAlternateSetting – [in] Interface alternate setting number

Returns

esp_err_t

esp_err_t usb_host_interface_release(usb_host_client_handle_t client_hdl, usb_device_handle_t dev_hdl, uint8_t bInterfaceNumber)

Function for a client to release a previously claimed interface.

  • A client should release a device’s interface after it no longer needs to communicate with the interface

  • A client must release all of its interfaces of a device it has claimed before being able to close the device

Note

This function can block

Parameters

  • client_hdl – [in] Client handle

  • dev_hdl – [in] Device handle

  • bInterfaceNumber – [in] Interface number

Returns

esp_err_t

esp_err_t usb_host_endpoint_halt(usb_device_handle_t dev_hdl, uint8_t bEndpointAddress)

Halt a particular endpoint.

  • The device must have been opened by a client

  • The endpoint must be part of an interface claimed by a client

  • Once halted, the endpoint must be cleared using usb_host_endpoint_clear() before it can communicate again

Note

This function can block

Parameters

  • dev_hdl – Device handle

  • bEndpointAddress – Endpoint address

Returns

esp_err_t

esp_err_t usb_host_endpoint_flush(usb_device_handle_t dev_hdl, uint8_t bEndpointAddress)

Flush a particular endpoint.

  • The device must have been opened by a client

  • The endpoint must be part of an interface claimed by a client

  • The endpoint must have been halted (either through a transfer error, or usb_host_endpoint_halt())

  • Flushing an endpoint will caused an queued up transfers to be canceled

Note

This function can block

Parameters

  • dev_hdl – Device handle

  • bEndpointAddress – Endpoint address

Returns

esp_err_t

esp_err_t usb_host_endpoint_clear(usb_device_handle_t dev_hdl, uint8_t bEndpointAddress)

Clear a halt on a particular endpoint.

  • The device must have been opened by a client

  • The endpoint must be part of an interface claimed by a client

  • The endpoint must have been halted (either through a transfer error, or usb_host_endpoint_halt())

  • If the endpoint has any queued up transfers, clearing a halt will resume their execution

Note

This function can block

Parameters

  • dev_hdl – Device handle

  • bEndpointAddress – Endpoint address

Returns

esp_err_t

esp_err_t usb_host_transfer_alloc(size_t data_buffer_size, int num_isoc_packets, usb_transfer_t **transfer)

Allocate a transfer object.

  • This function allocates a transfer object

  • Each transfer object has a fixed sized buffer specified on allocation

  • A transfer object can be re-used indefinitely

  • A transfer can be submitted using usb_host_transfer_submit() or usb_host_transfer_submit_control()

Parameters

  • data_buffer_size – [in] Size of the transfer’s data buffer

  • num_isoc_packets – [in] Number of isochronous packets in transfer (set to 0 for non-isochronous transfers)

  • transfer – [out] Transfer object

Returns

esp_err_t

esp_err_t usb_host_transfer_free(usb_transfer_t *transfer)

Free a transfer object.

  • Free a transfer object previously allocated using usb_host_transfer_alloc()

  • The transfer must not be in-flight when attempting to free it

  • If a NULL pointer is passed, this function will simply return ESP_OK

Parameters

transfer – [in] Transfer object

Returns

esp_err_t

esp_err_t usb_host_transfer_submit(usb_transfer_t *transfer)

Submit a non-control transfer.

  • Submit a transfer to a particular endpoint. The device and endpoint number is specified inside the transfer

  • The transfer must be properly initialized before submitting

  • On completion, the transfer’s callback will be called from the client’s usb_host_client_handle_events() function.

Parameters

transfer – [in] Initialized transfer object

Returns

esp_err_t

esp_err_t usb_host_transfer_submit_control(usb_host_client_handle_t client_hdl, usb_transfer_t *transfer)

Submit a control transfer.

  • Submit a control transfer to a particular device. The client must have opened the device first

  • The transfer must be properly initialized before submitting. The first 8 bytes of the transfer’s data buffer should contain the control transfer setup packet

  • On completion, the transfer’s callback will be called from the client’s usb_host_client_handle_events() function.

Parameters

  • client_hdl – [in] Client handle

  • transfer – [in] Initialized transfer object

Returns

esp_err_t

Structures

struct usb_host_client_event_msg_t

Client event message.

Client event messages are sent to each client of the USB Host Library in order to notify them of various USB Host Library events such as:

  • Addition of new devices

  • Removal of existing devices

Note

The event message structure has a union with members corresponding to each particular event. Based on the event type, only the relevant member field should be accessed.

Public Members

usb_host_client_event_t event

Type of event

uint8_t address

New device’s address

struct usb_host_client_event_msg_t::[anonymous]::[anonymous] new_dev

New device info

usb_device_handle_t dev_hdl

The handle of the device that was gone

struct usb_host_client_event_msg_t::[anonymous]::[anonymous] dev_gone

Gone device info

struct usb_host_lib_info_t

Current information about the USB Host Library obtained via usb_host_lib_info()

Public Members

int num_devices

Current number of connected (and enumerated) devices

int num_clients

Current number of registered clients

struct usb_host_config_t

USB Host Library configuration.

Configuration structure of the USB Host Library. Provided in the usb_host_install() function

Public Members

bool skip_phy_setup

If set, the USB Host Library will not configure the USB PHY thus allowing the user to manually configure the USB PHY before calling usb_host_install(). Users should set this if they want to use an external USB PHY. Otherwise, the USB Host Library will automatically configure the internal USB PHY

int intr_flags

Interrupt flags for the underlying ISR used by the USB Host stack

struct usb_host_client_config_t

USB Host Library Client configuration.

Configuration structure for a USB Host Library client. Provided in usb_host_client_register()

Public Members

bool is_synchronous

Whether the client is asynchronous or synchronous or not. Set to false for now.

int max_num_event_msg

Maximum number of event messages that can be stored (e.g., 3)

usb_host_client_event_cb_t client_event_callback

Client’s event callback function

void *callback_arg

Event callback function argument

struct usb_host_client_config_t::[anonymous]::[anonymous] async

Async callback config

Macros

USB_HOST_LIB_EVENT_FLAGS_NO_CLIENTS

All clients have been deregistered from the USB Host Library

USB_HOST_LIB_EVENT_FLAGS_ALL_FREE

The USB Host Library has freed all devices

Type Definitions

typedef struct usb_host_client_handle_s *usb_host_client_handle_t

Handle to a USB Host Library asynchronous client.

An asynchronous client can be registered using usb_host_client_register()

Note

Asynchronous API

typedef void (*usb_host_client_event_cb_t)(const usb_host_client_event_msg_t *event_msg, void *arg)

Client event callback.

  • Each client of the USB Host Library must register an event callback to receive event messages from the USB Host Library.

  • The client event callback is run from the context of the clients usb_host_client_handle_events() function

Enumerations

enum usb_host_client_event_t

The type event in a client event message.

Values:

enumerator USB_HOST_CLIENT_EVENT_NEW_DEV

A new device has been enumerated and added to the USB Host Library

enumerator USB_HOST_CLIENT_EVENT_DEV_GONE

A device opened by the client is now gone

Functions

const usb_standard_desc_t *usb_parse_next_descriptor(const usb_standard_desc_t *cur_desc, uint16_t wTotalLength, int *offset)

Get the next descriptor.

Given a particular descriptor within a full configuration descriptor, get the next descriptor within the configuration descriptor. This is a convenience function that can be used to walk each individual descriptor within a full configuration descriptor.

Parameters

  • cur_desc – [in] Current descriptor

  • wTotalLength – [in] Total length of the configuration descriptor

  • offset – [inout] Byte offset relative to the start of the configuration descriptor. On input, it is the offset of the current descriptor. On output, it is the offset of the returned descriptor.

Returns

usb_standard_desc_t* Next descriptor, NULL if end of configuration descriptor reached

const usb_standard_desc_t *usb_parse_next_descriptor_of_type(const usb_standard_desc_t *cur_desc, uint16_t wTotalLength, uint8_t bDescriptorType, int *offset)

Get the next descriptor of a particular type.

Given a particular descriptor within a full configuration descriptor, get the next descriptor of a particular type (i.e., using the bDescriptorType value) within the configuration descriptor.

Parameters

  • cur_desc – [in] Current descriptor

  • wTotalLength – [in] Total length of the configuration descriptor

  • bDescriptorType – [in] Type of the next descriptor to get

  • offset – [inout] Byte offset relative to the start of the configuration descriptor. On input, it is the offset of the current descriptor. On output, it is the offset of the returned descriptor.

Returns

usb_standard_desc_t* Next descriptor, NULL if end descriptor is not found or configuration descriptor reached

int usb_parse_interface_number_of_alternate(const usb_config_desc_t *config_desc, uint8_t bInterfaceNumber)

Get the number of alternate settings for a bInterfaceNumber.

Given a particular configuration descriptor, for a particular bInterfaceNumber, get the number of alternate settings available for that interface (i.e., the max possible value of bAlternateSetting for that bInterfaceNumber).

Parameters

  • config_desc – [in] Pointer to the start of a full configuration descriptor

  • bInterfaceNumber – [in] Interface number

Returns

int The number of alternate settings that the interface has, -1 if bInterfaceNumber not found

const usb_intf_desc_t *usb_parse_interface_descriptor(const usb_config_desc_t *config_desc, uint8_t bInterfaceNumber, uint8_t bAlternateSetting, int *offset)

Get a particular interface descriptor (using bInterfaceNumber and bAlternateSetting)

Given a full configuration descriptor, get a particular interface descriptor.

Note

To get the number of alternate settings for a particular bInterfaceNumber, call usb_parse_interface_number_of_alternate()

Parameters

  • config_desc – [in] Pointer to the start of a full configuration descriptor

  • bInterfaceNumber – [in] Interface number

  • bAlternateSetting – [in] Alternate setting number

  • offset – [out] Byte offset of the interface descriptor relative to the start of the configuration descriptor. Can be NULL.

Returns

const usb_intf_desc_t* Pointer to interface descriptor, NULL if not found.

const usb_ep_desc_t *usb_parse_endpoint_descriptor_by_index(const usb_intf_desc_t *intf_desc, int index, uint16_t wTotalLength, int *offset)

Get an endpoint descriptor within an interface descriptor.

Given an interface descriptor, get the Nth endpoint descriptor of the interface. The number of endpoints in an interface is indicated by the bNumEndpoints field of the interface descriptor.

Note

If bNumEndpoints is 0, it means the interface uses the default endpoint only

Parameters

  • intf_desc – [in] Pointer to thee start of an interface descriptor

  • index – [in] Endpoint index

  • wTotalLength – [in] Total length of the containing configuration descriptor

  • offset – [inout] Byte offset relative to the start of the configuration descriptor. On input, it is the offset of the interface descriptor. On output, it is the offset of the endpoint descriptor.

Returns

const usb_ep_desc_t* Pointer to endpoint descriptor, NULL if not found.

const usb_ep_desc_t *usb_parse_endpoint_descriptor_by_address(const usb_config_desc_t *config_desc, uint8_t bInterfaceNumber, uint8_t bAlternateSetting, uint8_t bEndpointAddress, int *offset)

Get an endpoint descriptor based on an endpoint’s address.

Given a configuration descriptor, get an endpoint descriptor based on it’s bEndpointAddress, bAlternateSetting, and bInterfaceNumber.

Parameters

  • config_desc – [in] Pointer to the start of a full configuration descriptor

  • bInterfaceNumber – [in] Interface number

  • bAlternateSetting – [in] Alternate setting number

  • bEndpointAddress – [in] Endpoint address

  • offset – [out] Byte offset of the endpoint descriptor relative to the start of the configuration descriptor. Can be NULL

Returns

const usb_ep_desc_t* Pointer to endpoint descriptor, NULL if not found.

void usb_print_device_descriptor(const usb_device_desc_t *devc_desc)

Print device descriptor.

Parameters

devc_desc – Device descriptor

void usb_print_config_descriptor(const usb_config_desc_t *cfg_desc, print_class_descriptor_cb class_specific_cb)

Print configuration descriptor.

  • This function prints the full contents of a configuration descriptor (including interface and endpoint descriptors)

  • When a non-standard descriptor is encountered, this function will call the class_specific_cb if it is provided

Parameters

  • cfg_desc – Configuration descriptor

  • class_specific_cb – Class specific descriptor callback. Can be NULL

void usb_print_string_descriptor(const usb_str_desc_t *str_desc)

Print a string descriptor.

This funciton will only print ASCII characters of the UTF-16 encoded string

Parameters

str_desc – String descriptor

static inline int usb_round_up_to_mps(int num_bytes, int mps)

Round up to an integer multiple of endpoint’s MPS.

This is a convenience function to round up a size/length to an endpoint’s MPS (Maximum packet size). This is useful when calculating transfer or buffer lengths of IN endpoints.

  • If MPS <= 0, this function will return 0

  • If num_bytes <= 0, this function will return 0

Parameters

  • num_bytes – [in] Number of bytes

  • mps – [in] MPS

Returns

int Round up integer multiple of MPS

Type Definitions

typedef void (*print_class_descriptor_cb)(const usb_standard_desc_t*)

Print class specific descriptor callback.

Optional callback to be provided to usb_print_config_descriptor() function. The callback is called when when a non-standard descriptor is encountered. The callback should decode the descriptor as print it.

Structures

struct usb_device_info_t

Basic information of an enumerated device.

Public Members

usb_speed_t speed

Device’s speed

uint8_t dev_addr

Device’s address

uint8_t bMaxPacketSize0

The maximum packet size of the device’s default endpoint

uint8_t bConfigurationValue

Device’s current configuration number

const usb_str_desc_t *str_desc_manufacturer

Pointer to Manufacturer string descriptor (can be NULL)

const usb_str_desc_t *str_desc_product

Pointer to Product string descriptor (can be NULL)

const usb_str_desc_t *str_desc_serial_num

Pointer to Serial Number string descriptor (can be NULL)

struct usb_isoc_packet_desc_t

Isochronous packet descriptor.

If the number of bytes in an Isochronous transfer is larger than the MPS of the endpoint, the transfer is split into multiple packets transmitted at the endpoint’s specified interval. An array of Isochronous packet descriptors describes how an Isochronous transfer should be split into multiple packets.

Public Members

int num_bytes

Number of bytes to transmit/receive in the packet. IN packets should be integer multiple of MPS

int actual_num_bytes

Actual number of bytes transmitted/received in the packet

usb_transfer_status_t status

Status of the packet

struct usb_transfer_s

USB transfer structure.

Public Members

uint8_t *const data_buffer

Pointer to data buffer

const size_t data_buffer_size

Size of the data buffer in bytes

int num_bytes

Number of bytes to transfer. Control transfers should include the size of the setup packet. Isochronous transfer should be the total transfer size of all packets. For non-control IN transfers, num_bytes should be an integer multiple of MPS.

int actual_num_bytes

Actual number of bytes transferred

uint32_t flags

Transfer flags

usb_device_handle_t device_handle

Device handle

uint8_t bEndpointAddress

Endpoint Address

usb_transfer_status_t status

Status of the transfer

uint32_t timeout_ms

Timeout (in milliseconds) of the packet (currently not supported yet)

usb_transfer_cb_t callback

Transfer callback

void *context

Context variable for transfer to associate transfer with something

const int num_isoc_packets

Only relevant to Isochronous. Number of service periods (i.e., intervals) to transfer data buffer over.

usb_isoc_packet_desc_t isoc_packet_desc[]

Descriptors for each Isochronous packet

Macros

USB_TRANSFER_FLAG_ZERO_PACK

Terminate Bulk/Interrupt OUT transfer with a zero length packet.

OUT transfers normally terminate when the Host has transferred the exact amount of data it needs to the device. However, for bulk and interrupt OUT transfers, if the transfer size just happened to be a multiple of MPS, it will be impossible to know the boundary between two consecutive transfers to the same endpoint.

Therefore, this flag will cause the transfer to automatically add a zero length packet (ZLP) at the end of the transfer if the following conditions are met:

  • The target endpoint is a Bulk/Interrupt OUT endpoint (Host to device)

  • The transfer’s length (i.e., transfer.num_bytes) is a multiple of the endpoint’s MPS

Otherwise, this flag has no effect.

Users should check whether their target device’s class requires a ZLP, as not all Bulk/Interrupt OUT endpoints require them. For example:

  • For MSC Bulk Only Transport class, the Host MUST NEVER send a ZLP. Bulk transfer boundaries are determined by the CBW and CSW instead

  • For CDC Ethernet, the Host MUST ALWAYS send a ZLP if a segment (i.e., a transfer) is a multiple of MPS (See 3.3.1 Segment Delineation)

Note

See USB2.0 specification 5.7.3 and 5.8.3 for more details

Note

IN transfers normally terminate when the Host as receive the exact amount of data it needs (must be multiple of MPS) or the endpoint sends a short packet to the Host(For bulk OUT only). Indicates that a bulk OUT transfers should always terminate with a short packet, even if it means adding an extra zero length packet

Type Definitions

typedef struct usb_device_handle_s *usb_device_handle_t

Handle of a USB Device connected to a USB Host.

typedef struct usb_transfer_s usb_transfer_t

USB transfer structure.

This structure is used to represent a transfer from a software client to an endpoint over the USB bus. Some of the fields are made const on purpose as they are fixed on allocation. Users should call the appropriate USB Host Library function to allocate a USB transfer structure instead of allocating this structure themselves.

The transfer type is inferred from the endpoint this transfer is sent to. Depending on the transfer type, users should note the following:

  • Bulk: This structure represents a single bulk transfer. If the number of bytes exceeds the endpoint’s MPS, the transfer will be split into multiple MPS sized packets followed by a short packet.

  • Control: This structure represents a single control transfer. This first 8 bytes of the data_buffer must be filled with the setup packet (see usb_setup_packet_t). The num_bytes field should be the total size of the transfer (i.e., size of setup packet + wLength).

  • Interrupt: Represents an interrupt transfer. If num_bytes exceeds the MPS of the endpoint, the transfer will be split into multiple packets, and each packet is transferred at the endpoint’s specified interval.

  • Isochronous: Represents a stream of bytes that should be transferred to an endpoint at a fixed rate. The transfer is split into packets according to the each isoc_packet_desc. A packet is transferred at each interval of the endpoint. If an entire ISOC URB was transferred without error (skipped packets do not count as errors), the URB’s overall status and the status of each packet descriptor will be updated, and the actual_num_bytes reflects the total bytes transferred over all packets. If the ISOC URB encounters an error, the entire URB is considered erroneous so only the overall status will updated.

Note

For Bulk/Control/Interrupt IN transfers, the num_bytes must be a integer multiple of the endpoint’s MPS

Note

This structure should be allocated via usb_host_transfer_alloc()

Note

Once the transfer has be submitted, users should not modify the structure until the transfer has completed

typedef void (*usb_transfer_cb_t)(usb_transfer_t *transfer)

USB transfer completion callback.

Enumerations

enum usb_speed_t

USB Standard Speeds.

Values:

enumerator USB_SPEED_LOW

USB Low Speed (1.5 Mbit/s)

enumerator USB_SPEED_FULL

USB Full Speed (12 Mbit/s)

enum usb_transfer_type_t

The type of USB transfer.

Note

The enum values need to match the bmAttributes field of an EP descriptor

Values:

enumerator USB_TRANSFER_TYPE_CTRL
enumerator USB_TRANSFER_TYPE_ISOCHRONOUS
enumerator USB_TRANSFER_TYPE_BULK
enumerator USB_TRANSFER_TYPE_INTR
enum usb_transfer_status_t

The status of a particular transfer.

Values:

enumerator USB_TRANSFER_STATUS_COMPLETED

The transfer was successful (but may be short)

enumerator USB_TRANSFER_STATUS_ERROR

The transfer failed because due to excessive errors (e.g. no response or CRC error)

enumerator USB_TRANSFER_STATUS_TIMED_OUT

The transfer failed due to a time out

enumerator USB_TRANSFER_STATUS_CANCELED

The transfer was canceled

enumerator USB_TRANSFER_STATUS_STALL

The transfer was stalled

enumerator USB_TRANSFER_STATUS_OVERFLOW

The transfer as more data was sent than was requested

enumerator USB_TRANSFER_STATUS_SKIPPED

ISOC packets only. The packet was skipped due to system latency or bus overload

enumerator USB_TRANSFER_STATUS_NO_DEVICE

The transfer failed because the target device is gone

Unions

union usb_setup_packet_t
#include <usb_types_ch9.h>

Structure representing a USB control transfer setup packet.

See Table 9-2 of USB2.0 specification for more details

Public Members

uint8_t bmRequestType

Characteristics of request

uint8_t bRequest

Specific request

uint16_t wValue

Word-sized field that varies according to request

uint16_t wIndex

Word-sized field that varies according to request; typically used to pass an index or offset

uint16_t wLength

Number of bytes to transfer if there is a data stage

struct usb_setup_packet_t::[anonymous] [anonymous]
uint8_t val[8]

Descriptor value

union usb_standard_desc_t
#include <usb_types_ch9.h>

USB standard descriptor.

All USB standard descriptors start with these two bytes. Use this type when traversing over configuration descriptors

Public Members

uint8_t bLength

Size of the descriptor in bytes

uint8_t bDescriptorType

Descriptor Type

struct usb_standard_desc_t::[anonymous] [anonymous]

USB descriptor attributes

uint8_t val[2]

Descriptor value

union usb_device_desc_t
#include <usb_types_ch9.h>

Structure representing a USB device descriptor.

See Table 9-8 of USB2.0 specification for more details

Public Members

uint8_t bLength

Size of the descriptor in bytes

uint8_t bDescriptorType

DEVICE Descriptor Type

uint16_t bcdUSB

USB Specification Release Number in Binary-Coded Decimal (i.e., 2.10 is 210H)

uint8_t bDeviceClass

Class code (assigned by the USB-IF)

uint8_t bDeviceSubClass

Subclass code (assigned by the USB-IF)

uint8_t bDeviceProtocol

Protocol code (assigned by the USB-IF)

uint8_t bMaxPacketSize0

Maximum packet size for endpoint zero (only 8, 16, 32, or 64 are valid)

uint16_t idVendor

Vendor ID (assigned by the USB-IF)

uint16_t idProduct

Product ID (assigned by the manufacturer)

uint16_t bcdDevice

Device release number in binary-coded decimal

uint8_t iManufacturer

Index of string descriptor describing manufacturer

uint8_t iProduct

Index of string descriptor describing product

uint8_t iSerialNumber

Index of string descriptor describing the device’s serial number

uint8_t bNumConfigurations

Number of possible configurations

struct usb_device_desc_t::[anonymous] [anonymous]

USB descriptor attributes

uint8_t val[18]

Descriptor value

union usb_config_desc_t
#include <usb_types_ch9.h>

Structure representing a short USB configuration descriptor.

See Table 9-10 of USB2.0 specification for more details

Note

The full USB configuration includes all the interface and endpoint descriptors of that configuration.

Public Members

uint8_t bLength

Size of the descriptor in bytes

uint8_t bDescriptorType

CONFIGURATION Descriptor Type

uint16_t wTotalLength

Total length of data returned for this configuration

uint8_t bNumInterfaces

Number of interfaces supported by this configuration

uint8_t bConfigurationValue

Value to use as an argument to the SetConfiguration() request to select this configuration

uint8_t iConfiguration

Index of string descriptor describing this configuration

uint8_t bmAttributes

Configuration characteristics

uint8_t bMaxPower

Maximum power consumption of the USB device from the bus in this specific configuration when the device is fully operational.

struct usb_config_desc_t::[anonymous] [anonymous]

USB descriptor attributes

uint8_t val[9]

Descriptor value

union usb_iad_desc_t
#include <usb_types_ch9.h>

Structure representing a USB interface association descriptor.

Public Members

uint8_t bLength

Size of the descriptor in bytes

uint8_t bDescriptorType

INTERFACE ASSOCIATION Descriptor Type

uint8_t bFirstInterface

Interface number of the first interface that is associated with this function

uint8_t bInterfaceCount

Number of contiguous interfaces that are associated with this function

uint8_t bFunctionClass

Class code (assigned by USB-IF)

uint8_t bFunctionSubClass

Subclass code (assigned by USB-IF)

uint8_t bFunctionProtocol

Protocol code (assigned by USB-IF)

uint8_t iFunction

Index of string descriptor describing this function

struct usb_iad_desc_t::[anonymous] [anonymous]

USB descriptor attributes

uint8_t val[9]

Descriptor value

union usb_intf_desc_t
#include <usb_types_ch9.h>

Structure representing a USB interface descriptor.

See Table 9-12 of USB2.0 specification for more details

Public Members

uint8_t bLength

Size of the descriptor in bytes

uint8_t bDescriptorType

INTERFACE Descriptor Type

uint8_t bInterfaceNumber

Number of this interface.

uint8_t bAlternateSetting

Value used to select this alternate setting for the interface identified in the prior field

uint8_t bNumEndpoints

Number of endpoints used by this interface (excluding endpoint zero).

uint8_t bInterfaceClass

Class code (assigned by the USB-IF)

uint8_t bInterfaceSubClass

Subclass code (assigned by the USB-IF)

uint8_t bInterfaceProtocol

Protocol code (assigned by the USB)

uint8_t iInterface

Index of string descriptor describing this interface

struct usb_intf_desc_t::[anonymous] [anonymous]

USB descriptor attributes

uint8_t val[9]

Descriptor value

union usb_ep_desc_t
#include <usb_types_ch9.h>

Structure representing a USB endpoint descriptor.

See Table 9-13 of USB2.0 specification for more details

Public Members

uint8_t bLength

Size of the descriptor in bytes

uint8_t bDescriptorType

ENDPOINT Descriptor Type

uint8_t bEndpointAddress

The address of the endpoint on the USB device described by this descriptor

uint8_t bmAttributes

This field describes the endpoint’s attributes when it is configured using the bConfigurationValue.

uint16_t wMaxPacketSize

Maximum packet size this endpoint is capable of sending or receiving when this configuration is selected.

uint8_t bInterval

Interval for polling Isochronous and Interrupt endpoints. Expressed in frames or microframes depending on the device operating speed (1 ms for Low-Speed and Full-Speed or 125 us for USB High-Speed and above).

struct usb_ep_desc_t::[anonymous] [anonymous]

USB descriptor attributes

uint8_t val[7]

Descriptor value

union usb_str_desc_t
#include <usb_types_ch9.h>

Structure representing a USB string descriptor.

Public Members

uint8_t bLength

Size of the descriptor in bytes

uint8_t bDescriptorType

STRING Descriptor Type

uint16_t wData[]

UTF-16LE encoded

struct usb_str_desc_t::[anonymous] [anonymous]

USB descriptor attributes

uint8_t val[2]

Descriptor value

Macros

USB_DESC_ATTR
USB_B_DESCRIPTOR_TYPE_DEVICE

Descriptor types from USB2.0 specification table 9.5.

USB_B_DESCRIPTOR_TYPE_CONFIGURATION
USB_B_DESCRIPTOR_TYPE_STRING
USB_B_DESCRIPTOR_TYPE_INTERFACE
USB_B_DESCRIPTOR_TYPE_ENDPOINT
USB_B_DESCRIPTOR_TYPE_DEVICE_QUALIFIER
USB_B_DESCRIPTOR_TYPE_OTHER_SPEED_CONFIGURATION
USB_B_DESCRIPTOR_TYPE_INTERFACE_POWER
USB_B_DESCRIPTOR_TYPE_OTG

Descriptor types from USB 2.0 ECN.

USB_B_DESCRIPTOR_TYPE_DEBUG
USB_B_DESCRIPTOR_TYPE_INTERFACE_ASSOCIATION
USB_B_DESCRIPTOR_TYPE_SECURITY

Descriptor types from Wireless USB spec.

USB_B_DESCRIPTOR_TYPE_KEY
USB_B_DESCRIPTOR_TYPE_ENCRYPTION_TYPE
USB_B_DESCRIPTOR_TYPE_BOS
USB_B_DESCRIPTOR_TYPE_DEVICE_CAPABILITY
USB_B_DESCRIPTOR_TYPE_WIRELESS_ENDPOINT_COMP
USB_B_DESCRIPTOR_TYPE_WIRE_ADAPTER
USB_B_DESCRIPTOR_TYPE_RPIPE
USB_B_DESCRIPTOR_TYPE_CS_RADIO_CONTROL
USB_B_DESCRIPTOR_TYPE_PIPE_USAGE

Descriptor types from UAS specification.

USB_SETUP_PACKET_SIZE

Size of a USB control transfer setup packet in bytes.

USB_BM_REQUEST_TYPE_DIR_OUT

Bit masks belonging to the bmRequestType field of a setup packet.

USB_BM_REQUEST_TYPE_DIR_IN
USB_BM_REQUEST_TYPE_TYPE_STANDARD
USB_BM_REQUEST_TYPE_TYPE_CLASS
USB_BM_REQUEST_TYPE_TYPE_VENDOR
USB_BM_REQUEST_TYPE_TYPE_RESERVED
USB_BM_REQUEST_TYPE_TYPE_MASK
USB_BM_REQUEST_TYPE_RECIP_DEVICE
USB_BM_REQUEST_TYPE_RECIP_INTERFACE
USB_BM_REQUEST_TYPE_RECIP_ENDPOINT
USB_BM_REQUEST_TYPE_RECIP_OTHER
USB_BM_REQUEST_TYPE_RECIP_MASK
USB_B_REQUEST_GET_STATUS

Bit masks belonging to the bRequest field of a setup packet.

USB_B_REQUEST_CLEAR_FEATURE
USB_B_REQUEST_SET_FEATURE
USB_B_REQUEST_SET_ADDRESS
USB_B_REQUEST_GET_DESCRIPTOR
USB_B_REQUEST_SET_DESCRIPTOR
USB_B_REQUEST_GET_CONFIGURATION
USB_B_REQUEST_SET_CONFIGURATION
USB_B_REQUEST_GET_INTERFACE
USB_B_REQUEST_SET_INTERFACE
USB_B_REQUEST_SYNCH_FRAME
USB_W_VALUE_DT_DEVICE

Bit masks belonging to the wValue field of a setup packet.

USB_W_VALUE_DT_CONFIG
USB_W_VALUE_DT_STRING
USB_W_VALUE_DT_INTERFACE
USB_W_VALUE_DT_ENDPOINT
USB_W_VALUE_DT_DEVICE_QUALIFIER
USB_W_VALUE_DT_OTHER_SPEED_CONFIG
USB_W_VALUE_DT_INTERFACE_POWER
USB_SETUP_PACKET_INIT_SET_ADDR(setup_pkt_ptr, addr)

Initializer for a SET_ADDRESS request.

Sets the address of a connected device

USB_SETUP_PACKET_INIT_GET_DEVICE_DESC(setup_pkt_ptr)

Initializer for a request to get a device’s device descriptor.

USB_SETUP_PACKET_INIT_GET_CONFIG(setup_pkt_ptr)

Initializer for a request to get a device’s current configuration number.

USB_SETUP_PACKET_INIT_GET_CONFIG_DESC(setup_pkt_ptr, desc_index, desc_len)

Initializer for a request to get one of the device’s current configuration descriptor.

  • desc_index indicates the configuration’s index number

  • Number of bytes of the configuration descriptor to get

USB_SETUP_PACKET_INIT_SET_CONFIG(setup_pkt_ptr, config_num)

Initializer for a request to set a device’s current configuration number.

USB_SETUP_PACKET_INIT_SET_INTERFACE(setup_pkt_ptr, intf_num, alt_setting_num)

Initializer for a request to set an interface’s alternate setting.

USB_SETUP_PACKET_INIT_GET_STR_DESC(setup_pkt_ptr, string_index, lang_id, desc_len)

Initializer for a request to get an string descriptor.

USB_STANDARD_DESC_SIZE

Size of dummy USB standard descriptor.

USB_DEVICE_DESC_SIZE

Size of a USB device descriptor in bytes.

USB_CLASS_PER_INTERFACE

Possible base class values of the bDeviceClass field of a USB device descriptor.

USB_CLASS_AUDIO
USB_CLASS_COMM
USB_CLASS_HID
USB_CLASS_PHYSICAL
USB_CLASS_STILL_IMAGE
USB_CLASS_PRINTER
USB_CLASS_MASS_STORAGE
USB_CLASS_HUB
USB_CLASS_CDC_DATA
USB_CLASS_CSCID
USB_CLASS_CONTENT_SEC
USB_CLASS_VIDEO
USB_CLASS_WIRELESS_CONTROLLER
USB_CLASS_PERSONAL_HEALTHCARE
USB_CLASS_AUDIO_VIDEO
USB_CLASS_BILLBOARD
USB_CLASS_USB_TYPE_C_BRIDGE
USB_CLASS_MISC
USB_CLASS_APP_SPEC
USB_CLASS_VENDOR_SPEC
USB_SUBCLASS_VENDOR_SPEC

Vendor specific subclass code.

USB_CONFIG_DESC_SIZE

Size of a short USB configuration descriptor in bytes.

Note

The size of a full USB configuration includes all the interface and endpoint descriptors of that configuration.

USB_BM_ATTRIBUTES_ONE

Bit masks belonging to the bmAttributes field of a configuration descriptor.

USB_BM_ATTRIBUTES_SELFPOWER
USB_BM_ATTRIBUTES_WAKEUP
USB_BM_ATTRIBUTES_BATTERY
USB_IAD_DESC_SIZE

Size of a USB interface association descriptor in bytes.

USB_INTF_DESC_SIZE

Size of a USB interface descriptor in bytes.

USB_EP_DESC_SIZE

Size of a USB endpoint descriptor in bytes.

USB_B_ENDPOINT_ADDRESS_EP_NUM_MASK

Bit masks belonging to the bEndpointAddress field of an endpoint descriptor.

USB_B_ENDPOINT_ADDRESS_EP_DIR_MASK
USB_BM_ATTRIBUTES_XFERTYPE_MASK

Bit masks belonging to the bmAttributes field of an endpoint descriptor.

USB_BM_ATTRIBUTES_XFER_CONTROL
USB_BM_ATTRIBUTES_XFER_ISOC
USB_BM_ATTRIBUTES_XFER_BULK
USB_BM_ATTRIBUTES_XFER_INT
USB_BM_ATTRIBUTES_SYNCTYPE_MASK
USB_BM_ATTRIBUTES_SYNC_NONE
USB_BM_ATTRIBUTES_SYNC_ASYNC
USB_BM_ATTRIBUTES_SYNC_ADAPTIVE
USB_BM_ATTRIBUTES_SYNC_SYNC
USB_BM_ATTRIBUTES_USAGETYPE_MASK
USB_BM_ATTRIBUTES_USAGE_DATA
USB_BM_ATTRIBUTES_USAGE_FEEDBACK
USB_BM_ATTRIBUTES_USAGE_IMPLICIT_FB
USB_EP_DESC_GET_XFERTYPE(desc_ptr)

Macro helpers to get information about an endpoint from its descriptor.

USB_EP_DESC_GET_EP_NUM(desc_ptr)
USB_EP_DESC_GET_EP_DIR(desc_ptr)
USB_EP_DESC_GET_MPS(desc_ptr)
USB_STR_DESC_SIZE

Size of a short USB string descriptor in bytes.

Enumerations

enum usb_device_state_t

USB2.0 device states.

See Table 9-1 of USB2.0 specification for more details

Note

The USB_DEVICE_STATE_NOT_ATTACHED is not part of the USB2.0 specification, but is a catch all state for devices that need to be cleaned up after a sudden disconnection or port error.

Values:

enumerator USB_DEVICE_STATE_NOT_ATTACHED

The device was previously configured or suspended, but is no longer attached (either suddenly disconnected or a port error)

enumerator USB_DEVICE_STATE_ATTACHED

Device is attached to the USB, but is not powered.

enumerator USB_DEVICE_STATE_POWERED

Device is attached to the USB and powered, but has not been reset.

enumerator USB_DEVICE_STATE_DEFAULT

Device is attached to the USB and powered and has been reset, but has not been assigned a unique address. Device responds at the default address.

enumerator USB_DEVICE_STATE_ADDRESS

Device is attached to the USB, powered, has been reset, and a unique device address has been assigned. Device is not configured.

enumerator USB_DEVICE_STATE_CONFIGURED

Device is attached to the USB, powered, has been reset, has a unique address, is configured, and is not suspended. The host may now use the function provided by the device.

enumerator USB_DEVICE_STATE_SUSPENDED

Device is, at minimum, attached to the USB and is powered and has not seen bus activity for 3 ms. It may also have a unique address and be configured for use. However, because the device is suspended, the host may not use the device’s function.

Provide feedback about this document