主机:WIN10 64位
设备:STM32F411+PCM5102
STM32CubeMX版本:V6.0.1
JAVA:JDK 11
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写这篇文章主要是给自己备忘,因对USB协议规范没有系统的了解,可能有些地方理解不是很正确。
配置CubeMX生成的工程项目,目录结构如下,主要划分为HAL层(包含了驱动层),协议层和应用层,
![](https://img-blog.csdnimg.cn/20200919081224954.png)
驱动层:stm32f4xx_ii_usb.c,提供USB硬件寄存器的配置
HAL层:stm32f4xx_hal_pcd.c,对驱动进行封装,给上层提供统一接口
协议层:usbd_core.c usbd_ctlreq.c usbd_ioreq.c,USB基础协议解析
usbd_audio.c,audio class协议解析,提供功能接口
应用层:应用功能的实现
代码文件层次结构及调用关系:
![](https://img-blog.csdnimg.cn/20200919135622522.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x1b3Rvbmc4Ng==,size_16,color_FFFFFF,t_70)
设备描述符层次结构:
![](https://img-blog.csdnimg.cn/20200919093011471.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x1b3Rvbmc4Ng==,size_16,color_FFFFFF,t_70)
1、一个USB设备只有一个设备描述符和一个配置描述符,而接口描述符可以有多个
2、从上图可以看出usb speaker有两个接口描述符,I/F 0为音频控制接口,描述了一个输入终端IT,特征单元FU和一个输出终端OT;输入终端IT为音频流类型,是一个逻辑通道,数据来源于音频流接口;输出终端OT为speaker类型,即表明数据是输出到一个实际的speaker上面;特征单元FU描述了该音频流所支持的能力,如支持mute和调节volume。I/F 1为音频流接口,该接口通过描述符指定与IT进行关联,即该音频流为指定的IT提供数据。
3、音频控制接口I/F 0没有端点,所有控制信息都是通过默认端点0进行通讯
4、音频流接口I/F 1定义了两个setting,第一个为setting 0,没有任何端点,当USB枚举完成后,会默认使用这个setting;第二个为setting 1,有实际的物理端点,当电脑选择该USB Speaker作为音频输出时,会选择该setting。
![](https://img-blog.csdnimg.cn/20200919143841569.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x1b3Rvbmc4Ng==,size_16,color_FFFFFF,t_70)
配置描述符:
/* USB AUDIO device Configuration Descriptor */
__ALIGN_BEGIN static uint8_t USBD_AUDIO_CfgDesc[USB_AUDIO_CONFIG_DESC_SIZ] __ALIGN_END =
{
/* Configuration 1 */
0x09, /* bLength */
USB_DESC_TYPE_CONFIGURATION, /* bDescriptorType */
LOBYTE(USB_AUDIO_CONFIG_DESC_SIZ), /* wTotalLength 109 bytes*/
HIBYTE(USB_AUDIO_CONFIG_DESC_SIZ),
0x02, /* bNumInterfaces */
0x01, /* bConfigurationValue */
0x00, /* iConfiguration */
0xC0, /* bmAttributes BUS Powred*/
0x32, /* bMaxPower = 100 mA*/
/* 09 byte*/
/* USB Speaker Standard interface descriptor */
AUDIO_INTERFACE_DESC_SIZE, /* bLength */
USB_DESC_TYPE_INTERFACE, /* bDescriptorType */
0x00, /* bInterfaceNumber */
0x00, /* bAlternateSetting */
0x00, /* bNumEndpoints */
USB_DEVICE_CLASS_AUDIO, /* bInterfaceClass */
AUDIO_SUBCLASS_AUDIOCONTROL, /* bInterfaceSubClass */
AUDIO_PROTOCOL_UNDEFINED, /* bInterfaceProtocol */
0x00, /* iInterface */
/* 09 byte*/
/* USB Speaker Class-specific AC Interface Descriptor */
AUDIO_INTERFACE_DESC_SIZE, /* bLength */
AUDIO_INTERFACE_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_CONTROL_HEADER, /* bDescriptorSubtype */
0x00, /* 1.00 */ /* bcdADC */
0x01,
0x27, /* wTotalLength = 39*/
0x00,
0x01, /* bInCollection */
0x01, /* baInterfaceNr */
/* 09 byte*/
/* USB Speaker Input Terminal Descriptor */
AUDIO_INPUT_TERMINAL_DESC_SIZE, /* bLength */
AUDIO_INTERFACE_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_CONTROL_INPUT_TERMINAL, /* bDescriptorSubtype */
0x01, /* bTerminalID */
0x01, /* wTerminalType AUDIO_TERMINAL_USB_STREAMING 0x0101 */
0x01,
0x00, /* bAssocTerminal */
0x01, /* bNrChannels */
0x00, /* wChannelConfig 0x0000 Mono */
0x00,
0x00, /* iChannelNames */
0x00, /* iTerminal */
/* 12 byte*/
/* USB Speaker Audio Feature Unit Descriptor */
0x09, /* bLength */
AUDIO_INTERFACE_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_CONTROL_FEATURE_UNIT, /* bDescriptorSubtype */
AUDIO_OUT_STREAMING_CTRL, /* bUnitID */
0x01, /* bSourceID */
0x01, /* bControlSize */
AUDIO_CONTROL_MUTE, /* bmaControls(0) */
0, /* bmaControls(1) */
0x00, /* iTerminal */
/* 09 byte*/
/*USB Speaker Output Terminal Descriptor */
0x09, /* bLength */
AUDIO_INTERFACE_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_CONTROL_OUTPUT_TERMINAL, /* bDescriptorSubtype */
0x03, /* bTerminalID */
0x01, /* wTerminalType 0x0301*/
0x03,
0x00, /* bAssocTerminal */
0x02, /* bSourceID */
0x00, /* iTerminal */
/* 09 byte*/
/* USB Speaker Standard AS Interface Descriptor - Audio Streaming Zero Bandwith */
/* Interface 1, Alternate Setting 0 */
AUDIO_INTERFACE_DESC_SIZE, /* bLength */
USB_DESC_TYPE_INTERFACE, /* bDescriptorType */
0x01, /* bInterfaceNumber */
0x00, /* bAlternateSetting */
0x00, /* bNumEndpoints */
USB_DEVICE_CLASS_AUDIO, /* bInterfaceClass */
AUDIO_SUBCLASS_AUDIOSTREAMING, /* bInterfaceSubClass */
AUDIO_PROTOCOL_UNDEFINED, /* bInterfaceProtocol */
0x00, /* iInterface */
/* 09 byte*/
/* USB Speaker Standard AS Interface Descriptor - Audio Streaming Operational */
/* Interface 1, Alternate Setting 1 */
AUDIO_INTERFACE_DESC_SIZE, /* bLength */
USB_DESC_TYPE_INTERFACE, /* bDescriptorType */
0x01, /* bInterfaceNumber */
0x01, /* bAlternateSetting */
0x01, /* bNumEndpoints */
USB_DEVICE_CLASS_AUDIO, /* bInterfaceClass */
AUDIO_SUBCLASS_AUDIOSTREAMING, /* bInterfaceSubClass */
AUDIO_PROTOCOL_UNDEFINED, /* bInterfaceProtocol */
0x00, /* iInterface */
/* 09 byte*/
/* USB Speaker Audio Streaming Interface Descriptor */
AUDIO_STREAMING_INTERFACE_DESC_SIZE, /* bLength */
AUDIO_INTERFACE_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_STREAMING_GENERAL, /* bDescriptorSubtype */
0x01, /* bTerminalLink */
0x01, /* bDelay */
0x01, /* wFormatTag AUDIO_FORMAT_PCM 0x0001 */
0x00,
/* 07 byte*/
/* USB Speaker Audio Type III Format Interface Descriptor */
0x0B, /* bLength */
AUDIO_INTERFACE_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_STREAMING_FORMAT_TYPE, /* bDescriptorSubtype */
AUDIO_FORMAT_TYPE_I, /* bFormatType */
0x02, /* bNrChannels */
0x02, /* bSubFrameSize : 2 Bytes per frame (16bits) */
16, /* bBitResolution (16-bits per sample) */
0x01, /* bSamFreqType only one frequency supported */
AUDIO_SAMPLE_FREQ(USBD_AUDIO_FREQ), /* Audio sampling frequency coded on 3 bytes */
/* 11 byte*/
/* Endpoint 1 - Standard Descriptor */
AUDIO_STANDARD_ENDPOINT_DESC_SIZE, /* bLength */
USB_DESC_TYPE_ENDPOINT, /* bDescriptorType */
AUDIO_OUT_EP, /* bEndpointAddress 1 out endpoint */
USBD_EP_TYPE_ISOC, /* bmAttributes */
AUDIO_PACKET_SZE(USBD_AUDIO_FREQ), /* wMaxPacketSize in Bytes (Freq(Samples)*2(Stereo)*2(HalfWord)) */
AUDIO_FS_BINTERVAL, /* bInterval */
0x00, /* bRefresh */
0x00, /* bSynchAddress */
/* 09 byte*/
/* Endpoint - Audio Streaming Descriptor*/
AUDIO_STREAMING_ENDPOINT_DESC_SIZE, /* bLength */
AUDIO_ENDPOINT_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_ENDPOINT_GENERAL, /* bDescriptor */
0x00, /* bmAttributes */
0x00, /* bLockDelayUnits */
0x00, /* wLockDelay */
0x00,
/* 07 byte*/
} ;
USB Device Tree Viewer查看到的设备信息:
![](https://img-blog.csdnimg.cn/20200919132859136.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x1b3Rvbmc4Ng==,size_16,color_FFFFFF,t_70)