USB 主机

[English]

本文档提供了 USB 主机库的相关信息，按以下章节展开：

概述

USB 主机库（以下简称主机库）是 USB 主机栈的最底层，提供面向公众开放的 API。应用程序使用 USB 主机功能时，通常无需与主机库直接交互，而是使用某个主机 Class 驱动提供的 API，这些主机 Class 驱动构建在主机库之上。

然而，由于以下的某些原因（但不仅限于此），有时你可能需要直接使用主机库：

  • 需要实现自定义主机 Class 驱动程序

  • 需要更低级别的抽象

特性和限制

主机库具有以下特性：

  • 支持全速 (FS) 和低速 (LS) 设备。

  • 支持四种传输类型，即控制传输、块传输、中断传输和同步传输。

  • 支持多个 Class 驱动程序同时运行，即主机的多个客户端同时运行。

  • 单个设备可以由多个客户端同时使用，如复合设备。

  • 主机库及其底层主机栈不会在内部自动创建操作系统任务，任务数量完全由主机库接口的使用方式决定。一般来说，任务数量为 （运行中的主机 Class 驱动程序数量 + 1）。

目前，主机库及其底层主机栈存在以下限制：

  • 仅支持单个设备，而主机库的 API 支持多设备。

  • 仅支持异步传输。

  • 仅支持使用发现的首个配置，尚不支持变更为其他配置。

  • 尚不支持传输超时。

架构

USB 主机功能的关键实体

USB 主机功能涉及的关键实体

上图展示了使用 USB 主机功能时涉及的关键实体，包括：

  • 主机库

  • 主机库的 客户端

  • 设备

  • 主机库的 守护进程任务

主机库

主机库是 ESP-IDF USB 主机栈中面向公众开放的最底层的 API 层。任何其他 ESP-IDF 组件（如 Class 驱动程序或用户组件），如果需要与连接的 USB 设备通信，只能直接或间接使用主机库 API。

主机库 API 分为两类，即 库 API 和 客户端 API。

  • 客户端 API 负责主机库的客户端与一或多个 USB 设备间的通信，该 API 只能由主机库的注册客户端调用。

  • 库 API 负责主机库处理的通信中不特定于单个客户端的通信，如设备枚举。该 API 通常由主机库的守护进程任务调用。

客户端

主机库的客户端指使用主机库与 USB 设备通信的软件组件，如主机 Class 驱动程序或用户组件。每个客户端通常与任务间存在一对一关系，这表明，对特定客户端而言，其所有客户端 API 都应该在同一任务的上下文中调用。

通过将使用主机库的软件组件进行分类，划分为独立的客户端，主机库可以将所有客户端特定事件的处理委托给客户端对应的任务。换句话说，每个客户端任务负责管理与其对应的客户端之间的所有 USB 通信操作和事件处理，无需关心其他客户端的事件。

守护进程任务

尽管主机库将客户端事件的处理委托给客户端本身，但仍然需要处理主机库事件，即不特定于客户端的事件。主机库事件处理可能涉及以下内容：

  • 处理 USB 设备的连接、枚举和断连

  • 将控制传输从/向客户端进行重定向

  • 将事件转发给客户端

因此，除客户端任务外，主机库也需要一个任务来处理所有的库事件，这个任务通常是主机库守护进程任务。

设备

主机库隔离了客户端与设备处理的细节，包括连接、内存分配和枚举等，客户端只需提供已连接且已枚举的设备列表供选择。默认情况下，在枚举过程中，每个设备都会自动配置为使用找到的第一个配置，即通过获取配置描述符请求返回的第一个配置描述符。对于大多数标准设备，通常将第一个配置的 bConfigurationValue 设置为 1。启用选项 CONFIG_USB_HOST_ENABLE_ENUM_FILTER_CALLBACK 后，可以选择不同的 bConfigurationValue。获取更多详细信息，请参阅 Multiple configuration Support_。

只要不与相同接口通信，两个及以上的客户端可以同时与同一设备通信。然而，多个客户端同时与相同设备的默认端点（即 EP0）通信，将导致它们的控制传输序列化。

要与设备通信，客户端必须满足以下条件：

  1. 使用设备地址打开设备，告知主机库，客户端正在使用该设备。

  2. 获取将用于通信的接口，防止其他客户端获取相同的接口。

  3. 通过已经获取了使用权的设备接口的端点通信通道发送数据传输。客户端的任务负责处理其与 USB 设备通信相关的操作和事件。

用法

主机库及底层主机栈不会创建任何任务，客户端任务和守护进程任务等均需由 Class 驱动程序或用户自行创建。然而，主机库提供了两个事件处理函数，可以处理所有必要的主机库操作，这些函数应从客户端任务和守护进程任务中重复调用。因此，客户端任务和守护进程任务的使用将主要集中于调用这些事件处理函数。

主机库与守护进程任务

基本用法

主机库 API 提供了 usb_host_lib_handle_events()，可以处理库事件。该函数需要反复调用，通常是从守护进程任务中调用。函数 usb_host_lib_handle_events() 有以下特点：

  • 该函数会持续阻塞，直至需要处理库事件。

  • 每次调用该函数都会返回事件标志，有助于了解卸载主机库的时机。

最基础的守护进程任务通常类似以下代码片段：

#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) {
            ...
        }
        ...
    }
    ...
}

备注

了解守护进程任务的完整示例，请前往 peripherals/usb/host/usb_host_lib。

生命周期

USB 主机库典型生命周期

USB 主机库典型生命周期

上图展示了 USB 主机库的典型生命周期，其中涉及多个客户端和设备。具体而言，示例涉及以下内容：

  • 两个已注册的客户端（客户端 1 和客户端 2）。

  • 两个已连接的设备（设备 1 和设备 2），其中客户端 1 与设备 1 通信，客户端 2 与设备 2 通信。

参考上图可知，典型 USB 主机库生命周期包括以下关键阶段：

  1. 调用 usb_host_install()，安装主机库。

    • 调用任意主机库 API 前，请确保已完成主机库安装。

    • 调用 usb_host_install() 的位置（如从守护进程任务或其他任务中调用）取决于守护系统任务、客户端任务和系统其余部分间的同步逻辑。

  2. 安装完主机库后，调用 usb_host_client_register() 注册客户端。

    • 该注册函数通常从客户端任务调用，而客户端任务需等待来自守护进程任务的信号。

    • 调用过 usb_host_install() 后，如有需要，也可以在其他地方调用该注册函数。

  3. 设备 1 连接，并进行枚举。

    • 每个已注册的客户端（本案例中为客户端 1 和客户端 2）都会通过 USB_HOST_CLIENT_EVENT_NEW_DEV 事件得到新设备的通知。

    • 客户端 1 开启设备 1，并与之通信。

  4. 设备 2 连接，并进行枚举。
  5. 设备 1 突然断开连接。

    • 客户端 1 通过 USB_HOST_CLIENT_EVENT_DEV_GONE 得到通知，并开始清理，关闭和释放客户端 1 与设备 1 之间的关联资源。

    • 客户端 2 不会收到通知，因为它并未开启设备 1。

  6. 客户端 1 完成清理，调用 usb_host_client_deregister() 注销客户端。

    • 该注销函数通常在任务退出前，从客户端任务中调用。

    • 如有需要，只要客户端 1 已完成清理，也可以在其他地方调用该注销函数。

  7. 客户端 2 完成与设备 2 的通信，随后关闭设备 2，并自行注销。

    • 由于客户端 2 是最后一个注销的客户端，通过 USB_HOST_LIB_EVENT_FLAGS_NO_CLIENTS 事件标志，守护进程任务可以得知，所有客户端已注销。

    • 设备 2 未释放，仍会进行分配，因为虽然没有任何客户端打开设备 2，但它仍处于连接状态。

  8. 所有客户端注销后，守护进程任务开始清理。

  9. 一旦守护进程任务确认所有客户端均已注销，且所有设备均已释放，便可调用 usb_host_uninstall()，卸载主机库。

客户端与 Class 驱动程序

基本用法

主机库 API 提供函数 usb_host_client_handle_events()，可以处理特定客户端事件。该函数需要反复调用，通常是从客户端任务中调用。函数 usb_host_client_handle_events() 有以下特点：

  • 该函数可以持续阻塞，直至需要处理客户端事件。

  • 该函数的主要目的是发生客户端事件时，调用多个事件处理回调函数。

以下回调函数均从 usb_host_client_handle_events() 中调用，因此客户端任务能够获取事件通知。

  • 类型为 usb_host_client_event_cb_t 的客户端事件回调函数会将客户端事件消息传递给客户端，提示添加、移除设备等事件。

  • 类型为 usb_transfer_cb_t 的 USB 传输完成回调函数表明，先前由客户端提交的特定 USB 传输已完成。

备注

考虑到上述回调函数从 usb_host_client_handle_events() 中调用，应避免在回调函数内部阻塞，否则将导致 usb_host_client_handle_events() 阻塞，阻止其他待处理的客户端事件得到处理。

以下代码片段展示了一个基础的主机 Class 驱动程序及其客户端任务，代码片段中包括：

  • 一个简单的客户端任务函数 client_task，它会在循环中调用 usb_host_client_handle_events()。

  • 使用客户端事件回调函数和传输完成回调函数。

  • 一个用于 Class 驱动程序的简单状态机。该 Class 驱动程序仅支持打开设备，发送 OUT 传输到 EP1，然后关闭设备。

#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)
{
    //该函数从 usb_host_client_handle_events() 中调用，请勿在此阻塞，并尽量保持简洁
    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; //存储新设备的地址
            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)
{
    //该函数从 usb_host_client_handle_events() 中调用，请勿在此阻塞，并尽量保持简洁
    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)
{
    ... //等待主机库安装
    //初始化 Class 驱动程序对象
    struct class_driver_control class_driver_obj = {0};
    //注册客户端
    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);
    //分配一个 USB 传输
    usb_transfer_t *transfer;
    usb_host_transfer_alloc(1024, 0, &transfer);

    //事件处理循环
    bool exit = false;
    while (!exit) {
        //调用客户端事件处理函数
        usb_host_client_handle_events(class_driver_obj.client_hdl, portMAX_DELAY);
        //执行待处理的 Class 驱动程序操作
        if (class_driver_obj.actions & CLASS_DRIVER_ACTION_OPEN_DEV) {
            //开启设备，声明接口 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) {
            //发送一个 OUT 传输到 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) {
            //释放接口，关闭设备
            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;
        }
        ... //处理其他 Class 驱动程序要求的行为
    }

    //清理 Class 驱动程序
    usb_host_transfer_free(transfer);
    usb_host_client_deregister(class_driver_obj.client_hdl);
    ... //删除客户端任务。如有需要，向守护进程任务发送信号。
}

备注

在实际应用中，主机 Class 驱动程序还能支持更多功能，因此也存在更复杂的状态机。主机 Class 驱动程序可能需要：

  • 能够开启多个设备

  • 解析已开启设备的描述符，确定设备是否是目标 Class

  • 按特定顺序，与接口的多个端点通信

  • 声明设备的多个接口

  • 处理各种错误情况

生命周期

客户端任务与 Class 驱动程序的典型生命周期包括以下关键阶段：

  1. 等待与主机库有关的信号完成安装。

  2. 通过 usb_host_client_register() 注册客户端，并分配其他的 Class 驱动程序资源，如使用 usb_host_transfer_alloc() 分配传输。

  3. 对于 Class 驱动程序需要与之通信的各个新设备：

    1. 调用 usb_host_device_addr_list_fill()，检查设备是否已连接。

    2. 如果设备尚未连接，则等待客户端事件回调函数的 USB_HOST_CLIENT_EVENT_NEW_DEV 事件。

    3. 调用 usb_host_device_open() 开启设备。

    4. 分别调用 usb_host_get_device_descriptor() 和 usb_host_get_active_config_descriptor()，解析设备和配置描述符。

    5. 调用 usb_host_interface_claim()，声明设备的必要接口。

  4. 调用 usb_host_transfer_submit() 或 usb_host_transfer_submit_control()，向设备提交传输。

  5. 一旦 USB_HOST_CLIENT_EVENT_DEV_GONE 事件表示，Class 驱动程序不再需要已打开的设备，或者设备断开连接：

    1. 在这些端点上调用 usb_host_endpoint_halt() 和 usb_host_endpoint_flush()，停止先前提交的传输。

    2. 调用 usb_host_interface_release()，释放先前声明的所有接口。

    3. 调用 usb_host_device_close()，关闭设备。

  6. 调用 usb_host_client_deregister() 注销客户端，并释放其他 Class 驱动程序资源。

  7. 删除客户端任务。如有需要，向守护进程任务发送信号。

示例

主机库示例

peripherals/usb/host/usb_host_lib 演示了如何使用 USB 主机库 API 来安装和注册客户端、等待设备连接、打印设备信息和处理断开连接，并重复这些步骤，直到退出应用程序。

Class 驱动程序示例

USB 主机栈提供了大量示例，展示了如何通过使用主机库 API 创建主机 Class 驱动程序。

CDC-ACM

  • 通信设备 Class（抽象控制模型）的主机 Class 驱动程序通过 乐鑫组件注册表 作为受管理的组件分发。

  • 示例 peripherals/usb/host/cdc/cdc_acm_host 演示了使用 CDC-ACM 主机驱动程序组件，实现 ESP32-S3 与 USB CDC-ACM 设备的通信。

  • 示例 peripherals/usb/host/cdc/cdc_acm_vcp 演示了如何扩展 CDC-ACM 的主机驱动程序，以支持 VCP 设备（即虚拟通信端口设备，如 CP210x、FTDI FT23x 或 CH34x），以及如何使用 CDC-ACM API 控制设备并发送数据。

  • 示例 esp_modem 中也使用了 CDC-ACM 驱动程序，该程序在这些示例中与蜂窝模块通信。

MSC

  • 大容量存储 Class（仅支持批量传输）的主机 Class 驱动程序已部署到 乐鑫组件注册表。

  • 示例 peripherals/usb/host/msc 演示了如何使用 USB 大容量存储类来访问、读取、写入和操作 USB 闪存驱动器，包括处理 USB 重新连接和反初始化 USB 主机堆栈。

HID

  • HID（人机接口设备）的主机 class 驱动作为托管组件通过 乐鑫组件注册表 分发。

  • 示例 peripherals/usb/host/hid 演示了如何在 ESP32-S3 上实现基本的 USB 主机 HID 类驱动，以便与 USB HID 设备（如键盘和鼠标）进行通信，并持续扫描设备的连接状态。一旦连接成功，即获取 HID 报告。

UVC

  • USB 视频设备 Class 的主机 Class 驱动程序作为托管组件通过 乐鑫组件注册表 分发。

  • 示例 peripherals/usb/host/uvc 演示了如何使用 libuvc 库从 USB 摄像头捕获视频，并通过托管 TCP 服务器将视频流通过 Wi-Fi 传输，同时提供了使用 player.py 脚本在 PC 上查看捕获视频的选项。

主机栈配置

非兼容设备支持

为了支持某些非兼容或具有特定行为的 USB 设备，可以对 USB 主机栈进行配置。

USB 设备可能是热插拔的，因此必须配置电源开关和设备连接之间的延迟，以及设备内部电源稳定后的延迟。

枚举配置

在枚举已连接 USB 设备的过程中，需要给一些事件配置合适的间隔时间以确保设备正常运行。

USB 根集线器上电和连接事件时序

USB 根集线器上电和连接事件时序

上图展示了与连接设备时开启端口电源和热插拔设备相关的所有间隔时间。

  • 端口复位或恢复运行后，USB 系统软件应提供 10 毫秒的恢复时间，此后连接到端口的设备才会响应数据传输。

  • 恢复时间结束后，如果设备收到 SetAddress() 请求，设备必须能够完成对该请求的处理，并能在 50 毫秒内成功完成请求的状态 (Status) 阶段。

  • 状态阶段结束后，设备允许有 2 毫秒的 SetAddress() 恢复时间。

备注

有关连接事件时序的更多信息，请参阅 通用串行总线 2.0 规范 > 第 7.1.7.3 章 连接和断开信令。

可通过 Menuconfig 选项设置 USB 主机栈的可配置参数。

多项配置支持

对于具有多项配置的 USB 设备，可以在设备枚举过程中指定所需的配置编号。

枚举过滤器

枚举过滤器是类型为 usb_host_enum_filter_cb_t 的回调函数。从新连接的 USB 设备上读取设备描述符后，USB 主机栈会在枚举过程开始时调用枚举过滤器，从而为用户提供读取的设备描述符。借助此回调，用户得以：

  • 选择 USB 设备的配置。

  • 过滤应该进行枚举的 USB 设备。

在 menuconfig 中启用 CONFIG_USB_HOST_ENABLE_ENUM_FILTER_CALLBACK 选项即可启用枚举过滤器。可以通过设置 usb_host_config_t::enum_filter_cb 来指定回调函数，该函数会在调用 usb_host_install() 时传递至主机库。

API 参考

USB 主机库的 API 包含以下头文件，但应用程序调用该 API 时只需 #include "usb/usb_host.h"，该头文件包含了所有 USB 主机库的头文件。

Header File

  • components/usb/include/usb/usb_host.h

  • This header file can be included with:

    #include "usb/usb_host.h"

  • This header file is a part of the API provided by the usb component. To declare that your component depends on usb, add the following to your CMakeLists.txt:

    REQUIRES usb

    or

    PRIV_REQUIRES usb

Functions

esp_err_t usb_host_install(const usb_host_config_t *config)

Install the USB Host Library.

  • This function should be called only once to install the USB Host Library

  • This function should be called before any other USB Host Library functions are called

备注

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.

参数

config -- [in] USB Host Library configuration

返回

  • ESP_OK: USB Host installed successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_INVALID_STATE: USB Host Library is not in correct state to be installed (eg. the library itself of one of it's drivers is already installed)

  • ESP_ERR_NO_MEM: Insufficient memory

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

备注

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).

返回

  • ESP_OK: USB Host uninstalled successfully

  • ESP_ERR_INVALID_STATE: USB Host Library is not installed, or has unfinished actions

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

备注

This function can block

参数

  • 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.

返回

  • ESP_OK: No events to be handled

  • ESP_ERR_INVALID_STATE: USB Host Library is not installed

  • ESP_ERR_TIMEOUT: Semaphore waiting for events has timed out

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())

返回

  • ESP_OK: USB Host library unblocked successfully

  • ESP_ERR_INVALID_STATE: USB Host Library is not installed

esp_err_t usb_host_lib_info(usb_host_lib_info_t *info_ret)

Get current information about the USB Host Library.

参数

info_ret -- [out] USB Host Library Information

返回

  • ESP_OK: USB Host Library info obtained successfully

  • ESP_ERR_INVALID_STATE: USB Host Library is not installed

  • ESP_ERR_INVALID_ARG: Invalid argument

esp_err_t usb_host_lib_set_root_port_power(bool enable)

Power the root port ON or OFF.

  • Powering ON the root port will allow device connections to occur

  • Powering OFF the root port will disconnect all devices downstream off the root port and prevent any further device connections.

备注

If 'usb_host_config_t.root_port_unpowered' was set on USB Host Library installation, users must call this function to power ON the root port before any device connections can occur.

参数

enable -- [in] True to power the root port ON, false to power OFF

返回

  • ESP_OK: Root port power enabled/disabled

  • ESP_ERR_INVALID_STATE: Root port already powered or HUB driver not installed

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

参数

  • client_config -- [in] Client configuration

  • client_hdl_ret -- [out] Client handle

返回

  • ESP_OK: USB Host Library client registered successfully

  • ESP_ERR_INVALID_STATE: USB Host Library is not installed

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_NO_MEM: Insufficient memory

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

参数

client_hdl -- [in] Client handle

返回

  • ESP_OK: USB Host Library client deregistered successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

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

备注

This function can block

参数

  • client_hdl -- [in] Client handle

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

返回

  • ESP_OK: No event to be handled

  • ESP_ERR_INVALID_STATE: USB Host Library is not installed

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_TIMEOUT: Semaphore waiting for events has timed out

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.

参数

client_hdl -- [in] Client handle

返回

  • ESP_OK: Client unblocked successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

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.)

参数

  • client_hdl -- [in] Client handle

  • dev_addr -- [in] Device's address

  • dev_hdl_ret -- [out] Device's handle

返回

  • ESP_OK: Device opened successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

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 de-registering

备注

This function can block

参数

  • client_hdl -- [in] Client handle

  • dev_hdl -- [in] Device handle

返回

  • ESP_OK: Device closed successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_NOT_FOUND: Device address not found among opened devices

  • ESP_ERR_INVALID_STATE: The client never opened the device, or the client has not released all the interfaces from the device

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

返回

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

  • ESP_ERR_INVALID_STATE: Client must be deregistered

  • 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_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.

参数

  • list_len -- [in] Length of the empty list

  • dev_addr_list -- [inout] Empty list to be filled

  • num_dev_ret -- [out] Number of devices

返回

  • ESP_OK: Device list filled successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

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

备注

This function can block

参数

  • dev_hdl -- [in] Device handle

  • dev_info -- [out] Device information

返回

  • ESP_OK: Device information obtained successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

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

备注

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

参数

  • dev_hdl -- [in] Device handle

  • device_desc -- [out] Device descriptor

返回

  • ESP_OK: Device descriptor obtained successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

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

备注

This function can block

备注

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

参数

  • dev_hdl -- [in] Device handle

  • config_desc -- [out] Configuration descriptor

返回

  • ESP_OK: Active configuration descriptor obtained successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

esp_err_t usb_host_get_config_desc(usb_host_client_handle_t client_hdl, usb_device_handle_t dev_hdl, uint8_t bConfigurationValue, const usb_config_desc_t **config_desc_ret)

Get get device's configuration descriptor.

  • The USB Host library only caches a device's active configuration descriptor.

  • This function reads any configuration descriptor of a particular device (specified by bConfigurationValue).

  • This function will read the specified configuration descriptor via control transfers, and allocate memory to store that descriptor.

  • Users can call usb_host_free_config_desc() to free the descriptor's memory afterwards.

备注

This function can block

备注

A client must call usb_host_device_open() on the device first

备注

bConfigurationValue starts from index 1

参数

  • client_hdl -- [in] Client handle - usb_host_client_handle_events() should be called repeatedly in a separate task to handle client events

  • dev_hdl -- [in] Device handle

  • bConfigurationValue -- [in] Index of device's configuration descriptor to be read

  • config_desc_ret -- [out] Returned configuration descriptor

返回

  • ESP_OK: Configuration descriptor obtained successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_NOT_SUPPORTED: Invalid bConfigurationValue value (the device does not have this configuration value)

  • ESP_ERR_NO_MEM: Insufficient memory

esp_err_t usb_host_free_config_desc(const usb_config_desc_t *config_desc)

Free a configuration descriptor.

This function frees a configuration descriptor that was returned by usb_host_get_config_desc()

参数

config_desc -- [out] Configuration descriptor

返回

  • ESP_OK: Configuration descriptor freed successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

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.

备注

This function can block

参数

  • client_hdl -- [in] Client handle

  • dev_hdl -- [in] Device handle

  • bInterfaceNumber -- [in] Interface number

  • bAlternateSetting -- [in] Interface alternate setting number

返回

  • ESP_OK: Interface claimed successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_INVALID_STATE: USB Host is not a correct state to claim an interface

  • ESP_ERR_NOT_FOUND: Interface or EP not found

  • ESP_ERR_NO_MEM: Insufficient memory

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

备注

This function can block

参数

  • client_hdl -- [in] Client handle

  • dev_hdl -- [in] Device handle

  • bInterfaceNumber -- [in] Interface number

返回

  • ESP_OK: Interface released successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_INVALID_STATE: Client never opened the USB Device, or interface currently can not be freed

  • ESP_ERR_NOT_FOUND: Interface number not found in the list of interfaces

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

备注

This function can block

参数

  • dev_hdl -- [in] Device handle

  • bEndpointAddress -- [in] Endpoint address

返回

  • ESP_OK: Endpoint halted successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_NOT_FOUND: Endpoint address not found

  • ESP_ERR_INVALID_STATE: Endpoint pipe is not in the correct state/condition to execute a command

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

备注

This function can block

参数

  • dev_hdl -- [in] Device handle

  • bEndpointAddress -- [in] Endpoint address

返回

  • ESP_OK: Endpoint flushed successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_NOT_FOUND: Endpoint address not found

  • ESP_ERR_INVALID_STATE: Endpoint pipe is not in the correct state/condition to execute a command

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

备注

This function can block

参数

  • dev_hdl -- [in] Device handle

  • bEndpointAddress -- [in] Endpoint address

返回

  • ESP_OK: Endpoint cleared successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_NOT_FOUND: Endpoint address not found

  • ESP_ERR_INVALID_STATE: Endpoint pipe is not in the correct state/condition to execute a command

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()

参数

  • 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

返回

  • ESP_OK: Transfer object allocated successfully

  • ESP_ERR_NO_MEM: Insufficient memory

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

参数

transfer -- [in] Transfer object

返回

  • ESP_OK: Transfer object freed successfully

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.

参数

transfer -- [in] Initialized transfer object

返回

  • ESP_OK: Transfer submitted successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_NOT_FINISHED: Transfer already in-flight

  • ESP_ERR_NOT_FOUND: Endpoint address not found

  • ESP_ERR_INVALID_STATE: Endpoint pipe is not in a correct state to submit transfer

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.

参数

  • client_hdl -- [in] Client handle

  • transfer -- [in] Initialized transfer object

返回

  • ESP_OK: Control transfer submitted successfully

  • ESP_ERR_INVALID_ARG: Invalid argument

  • ESP_ERR_NOT_FINISHED: Transfer already in-flight

  • ESP_ERR_NOT_FOUND: Endpoint address not found

  • ESP_ERR_INVALID_STATE: Endpoint pipe is not in a correct state to submit transfer

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

备注

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

bool root_port_unpowered

If set, the USB Host Library will not power on the root port on installation. This allows users to power on the root port manually by calling usb_host_lib_set_root_port_power().

int intr_flags

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

usb_host_enum_filter_cb_t enum_filter_cb

Enumeration filter callback. Enable CONFIG_USB_HOST_ENABLE_ENUM_FILTER_CALLBACK to use this feature. Set to NULL otherwise.

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()

备注

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

Header File

  • components/usb/include/usb/usb_helpers.h

  • This header file can be included with:

    #include "usb/usb_helpers.h"

  • This header file is a part of the API provided by the usb component. To declare that your component depends on usb, add the following to your CMakeLists.txt:

    REQUIRES usb

    or

    PRIV_REQUIRES usb

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.

参数

  • 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.

返回

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.

参数

  • 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.

返回

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).

参数

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

  • bInterfaceNumber -- [in] Interface number

返回

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.

备注

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

参数

  • 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.

返回

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.

备注

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

参数

  • 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.

返回

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.

参数

  • 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

返回

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.

参数

devc_desc -- [in] 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

参数

  • cfg_desc -- [in] Configuration descriptor

  • class_specific_cb -- [in] Class specific descriptor callback. Can be NULL

void usb_print_string_descriptor(const usb_str_desc_t *str_desc)

Print a string descriptor.

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

参数

str_desc -- [in] 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

参数

  • num_bytes -- [in] Number of bytes

  • mps -- [in] MPS

返回

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.

Header File

  • components/usb/include/usb/usb_types_stack.h

  • This header file can be included with:

    #include "usb/usb_types_stack.h"

  • This header file is a part of the API provided by the usb component. To declare that your component depends on usb, add the following to your CMakeLists.txt:

    REQUIRES usb

    or

    PRIV_REQUIRES usb

Structures

struct usb_parent_dev_info_t

Parent device information.

Public Members

usb_device_handle_t dev_hdl

Device's parent handle

uint8_t port_num

Device's parent port number

struct usb_device_info_t

Basic information of an enumerated device.

Public Members

usb_parent_dev_info_t parent

Device's parent information

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)

备注

See USB2.0 specification 5.7.3 and 5.8.3 for more details

备注

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 bool (*usb_host_enum_filter_cb_t)(const usb_device_desc_t *dev_desc, uint8_t *bConfigurationValue)

Enumeration filter callback.

This callback is called at the beginning of the enumeration process for a newly attached device. Through this callback, users are able to:

  • filter which devices should be enumerated

  • select the configuration number to use when enumerating the device

The device descriptor is passed to this callback to allow users to filter devices based on Vendor ID, Product ID, and class code.

Attention

This callback must be non-blocking

Attention

This callback must not submit any USB transfers

Param dev_desc

[in] Device descriptor of the device to enumerate

Param bConfigurationValue

[out] Configuration number to use when enumerating the device (starts with 1)

Return

bool

  • true: USB device will be enumerated

  • false: USB device will not be enumerated

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.

备注

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

备注

This structure should be allocated via usb_host_transfer_alloc()

备注

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)

enumerator USB_SPEED_HIGH

USB High Speed (480 Mbit/s)

enum usb_transfer_type_t

The type of USB transfer.

备注

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

Header File

  • components/usb/include/usb/usb_types_ch9.h

  • This header file can be included with:

    #include "usb/usb_types_ch9.h"

  • This header file is a part of the API provided by the usb component. To declare that your component depends on usb, add the following to your CMakeLists.txt:

    REQUIRES usb

    or

    PRIV_REQUIRES usb

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] USB_DESC_ATTR

USB descriptor attributes

uint8_t val[USB_SETUP_PACKET_SIZE]

Descriptor value

union usb_device_status_t
#include <usb_types_ch9.h>

Structure representing a USB device status.

See Figures 9-4 Information Returned by a GetStatus() Request to a Device of USB2.0 specification for more details

Public Members

uint16_t self_powered

1 - Device is currently self-powered, 0 - bus powered

uint16_t remote_wakeup

1 - the ability of the device to signal remote wakeup is enabled, 0 - the ability of the device to signal remote wakeup is disabled.

uint16_t reserved

reserved

struct usb_device_status_t::[anonymous] USB_DESC_ATTR

Packed

uint16_t val

Device status 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] USB_DESC_ATTR

USB descriptor attributes

uint8_t val[USB_STANDARD_DESC_SIZE]

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] USB_DESC_ATTR

USB descriptor attributes

uint8_t val[USB_DEVICE_DESC_SIZE]

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

备注

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] USB_DESC_ATTR

USB descriptor attributes

uint8_t val[USB_CONFIG_DESC_SIZE]

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] USB_DESC_ATTR

USB descriptor attributes

uint8_t val[USB_IAD_DESC_SIZE]

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] USB_DESC_ATTR

USB descriptor attributes

uint8_t val[USB_INTF_DESC_SIZE]

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] USB_DESC_ATTR

USB descriptor attributes

uint8_t val[USB_EP_DESC_SIZE]

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] USB_DESC_ATTR

USB descriptor attributes

uint8_t val[USB_STR_DESC_SIZE]

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_GET_STATUS(setup_pkt_ptr)

Initializer for a GET_STATUS request.

Sets the address of a connected device

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.

备注

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.

Must be set

USB_BM_ATTRIBUTES_SELFPOWER

Self powered

USB_BM_ATTRIBUTES_WAKEUP

Can wake-up

USB_BM_ATTRIBUTES_BATTERY

Battery powered

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_W_MAX_PACKET_SIZE_MPS_MASK

Bit masks belonging to the wMaxPacketSize field of endpoint descriptor.

USB_W_MAX_PACKET_SIZE_MULT_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_EP_DESC_GET_MULT(desc_ptr)
USB_EP_DESC_GET_SYNCTYPE(desc_ptr)
USB_EP_DESC_GET_USAGETYPE(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

备注

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.

维护注意事项

备注

有关 USB 主机栈内部实现的更多细节，请参阅 USB Host Maintainers Notes (Introduction)。

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