usb 音频类描述符及其说明(usb audio descriptor)

最新推荐文章于 2025-10-20 11:04:10 发布

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最新推荐文章于 2025-10-20 11:04:10 发布 · 2.1w 阅读

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CC 4.0 BY-SA版权

文章标签：

#descriptor #audio #interface #terminal #asynchronous #string

本文介绍了USB音频设备的描述符，包括设备、配置、接口、终端等描述符，重点解析了音频控制接口和音频流接口的设置，以及如何通过描述符实现设备的音频输入输出功能。内容涵盖USB描述符的结构、拓扑图和音频处理细节。

写在前面：

前两天拿到一个产品，也就是一speakerphone；以前自己也参加过音频类USB设备的研发，当然只是单独的speaker或microphone，也曾经想过怎么让同一USB设备即作speaker输出又作microphone输入，只不过没有具体去实现。当拿到这个speakerphone后就有一种去实现这样一个USB设备的冲动，于是就有了这篇文章.......

先给出完整的usb描述符供参考：

const unsigned char Demo_DeviceDescriptor[] =
{
//Device:USB1.10,Vid=0x0435,Pid=0x2430,bNumConfigurations = 0x01,
0x12,       //Length
0x01,    //DescriptorType
0x10,0x01, //bcdUSB
0x00,     //DeviceClass
0x00,     //DeviceSubClass
0x00,      //DeviceProtocol
0x08,    //bMaxPacketSize 8
0x35,0x04, //idVendor........
0x30,0x24, //idProduct........
0x01,0x00, //bcdDevice
1,     //iManufacturer
2,        //iProduct
3,         //iSerialNumber
0x01       //bNumConfigurations
};

/* USB Configuration Descriptor */
/*   All Descriptors (Configuration, Interface, Endpoint, Class, Vendor */
const unsigned char Demo_ConfigDescriptor[] =
{
//Configuration:wTotalLength = 0x00be,NumInterfaces = 0x03,
0x09,    //Length
0x02,    //DescriptorType : ConfigDescriptor
0xbe,0x00, //TotalLength:0x00be
0x03,     //NumInterfaces:3
0x01,    //ConfigurationValue
0x00,    //Configuration String
0x80,    //Attributes:Bus Power
0xfa,     //MaxPower = 0xfa*2ma

//standard interface AC descriptor(Interface 0, Alternate Setting 0):
//bNumEndpoints = 0x00,bInterFaceClass = 0x01(audio),bInterfaceSubClass = 0x01(audio ctl),
0x09,    //Length
0x04,    //DescriptorType:Inerface
0x00,     //InterfaceNum:0
0x00,       //AlternateSetting:0
0x00,       //NumEndpoint:0
0x01,       //InterfaceClass:audio
0x01,      //InterfaceSubClass:audio ctl
0x00,      //InterfaceProtocol
0x00,      //Interface String

//class-specific AC interface descriptor,audio interface(0x24),audio control header(0x01),
//Total Length 0x0048,Number of streaming interface 2,interfaceNr 2,1
0x0a,    //Length
0x24,      //DescriptorType:audio interface descriptor
0x01,     //DescriptorSubType:audio control header
0x00,0x01, //bcdADC:audio Device Class v1.00
0x48,0x00, //TotalLength:0x0048
0x02,     //InCollection:2 AudioStreaming interface
0x02,      //InterfaceNr(2) - AS #1 id AudioStreaming interface 2 belongs to this AudioControl interface
0x01,     //InterfaceNr(1) - AS #2 id AudioStreaming interface 1 belongs to this AudioControl interface

//USB Microphone IT:audio interface descriptor,audio control input terminal(0x02),terminal id 0x01,
//Microphone(0x0201),Input Terminal(0x02),2 channel:Left Front,Right Front
0x0c,    //Length
0x24,    //DescriptorType:audio interface descriptor
0x02,    //DescriptorSubType:Input Terminal
0x01,     //TerminalID:0x01