// Device Descriptor
{
    0x12,    // bLength
    USB_DESCRIPTOR_DEVICE,    // bDescriptorType
    USBW(0x0200),    // USB 2.0
    0xFF,   // bDeviceClass
    0x00,   // bDeviceSubclass
    0x00,   // bDeviceProtocol
    0x40,    // bMaxPacketSize0
    USBW(USB_VENDOR_BRAG),    // idVendor
    USBW(USB_PRODUCT_BRAG_DD2),    // idProduct
    USBW(0x0001),    // bcdDevice    :Device Release Number
    0x01,    // iManufacturer
    0x02,    // iProduct
    0x00,    // iSerialNumber
    0x01    // bNumConfigurations
},

// Configuration Descriptor
{
  // std configuration descriptor
    0x09,    // bLength
    USB_DESCRIPTOR_CONFIG,    // bDescriptorType
    USBW(USB_CFGDESCSIZE),    // wTotalLength
    0x01,    // bNumInterfaces
    0x01,    // bConfigurationValue
    0x00,    // iConfiguration
    0xC0,    // bmAttributes
    0x00,    // bMaxPower

  // Interface descriptor
    0x09,    // bLength
    USB_DESCRIPTOR_IFACE,    // bDescriptorType
    0x00,    // bInterfaceNumber
    0x00,    // bAlternateSetting
    0x03,    // bNumEndpoints
    0xFF,    // bInterfaceClass
    0x00,    // bInterfaceSubClass
    0x00,    // bInterfaceProtocol
    0x00,    // iInterface

  // Endpoint descriptor (OUT EP2)
    0x07,    // bLength
    USB_DESCRIPTOR_ENDPOINT,    // bDescriptorType
    0x02,    // bEndpointAddress    : D0..D3 - ep num; D7 - IN endpoint
    0x02,    // bmAttributes
    USBW(0x200),    // wMaxPacketSize
    0x01,    // bInterval

  // Endpoint descriptor (IN EP4)
    0x07,    // bLength
    USB_DESCRIPTOR_ENDPOINT,    // bDescriptorType
    0x84,    // bEndpointAddress    : D0..D3 - ep num; D7 - IN endpoint
    0x02,    // bmAttributes
    USBW(0x200),    // wMaxPacketSize
    0x01,    // bInterval

  // Endpoint descriptor (IN EP1)
    0x07,    // bLength
    USB_DESCRIPTOR_ENDPOINT,    // bDescriptorType
    0x81,    // bEndpointAddress    : D0..D3 - ep num; D7 - IN endpoint
    0x02,    // bmAttributes
    USBW(0x40),    // wMaxPacketSize
    0x80    // bInterval
},
#if USB_CFGDESCSIZE & 1
    0,
#endif

// LangID
    {USB_DESCRIPTOR_STRING_SIZE(1),USB_DESCRIPTOR_STRING,USB_LANG_EN_US},
// Manufacturer
{
    USB_DESCRIPTOR_STRING_SIZE(4),USB_DESCRIPTOR_STRING,
    'B',0,'r',0,'a',0,'g',0
},
// Product
{
     USB_DESCRIPTOR_STRING_SIZE(12),USB_DESCRIPTOR_STRING,
    'D',0,'i',0,'g',0,'i',0,'D',0,'e',0,'g',0,'a',0,'n',0,' ',0,'I',0,'I',0
}

С изохрлоном ясно. А ошибки-то вот откуда возьмутся, если используем хороший экранированный USB кабель, и нормально разведена плата? Вы изохрон пользуете?

const struct usbDevDesc UsbDevDesc={
    sizeof(struct usbDevDesc),
    USB_DESCRIPTOR_DEVICE,
    0x0200,    // USB 2.0
    0xEF,   // bDeviceClass
    0x02,   // bDeviceSubclass
    0x01,   // bDeviceProtocol
    USB_EP0_MAXSIZE,
    USB_VENDOR_BRAG,
    USB_BRAG_PRODUCT_DD,
    0x0001,        // Serial
    0x01,    // iManufacturer
    0x02,    // iProduct
    0x00,    // iSerialNumber
    0x01    //bNumConfigurations
};

const struct usbAuCfgDesc UsbCfgDesc={
    {
        sizeof(struct usbStdCfgDesc),
        USB_DESCRIPTOR_CONFIG,
        sizeof(struct usbAuCfgDesc),
        1,    //interfaces
        1,    //bConfigurationValue
        0,    //iConfiguration
        0xC0,    //SelfPowered
        0    //bMaxPower
    },
   /* Audio Control Interface */
    {
        sizeof(struct usbStdIfDesc),
        USB_DESCRIPTOR_IFACE,
        0,    //bInterfaceNumber
        0,    //bAlternateSetting
        0,    //bNumEndpoints
        0x01,    //AUDIO
        0x01,    //AUDIOCONTROL
        0,    
        0    //iInterface
    },
    {
        sizeof(struct usbCsAcDesc),
        0x24,    //CS_INTERFACE
        0x01,    //HEADER
        0x0100,    //bcdADC
        sizeof(struct usbCsAcDesc)+sizeof(struct usbCsItDesc)+
            sizeof(struct usbCsOtDesc), //wTotalLength
        USB_AUDIO_IFS,
        1    //baInterfaceNr
    },
    {
        sizeof(struct usbCsItDesc),
        0x24,    //CS_INTERFACE
        0x02,    //INPUT_TERMINAL
        0x01,    //bTerminalID
        0x0200,    //Input Undefined term type
        0x00,    //bAssocTerminal
        2,    //bNrChannels
        0x00000003, //wChannelConfig
        0,    //iChannelNames
        0    //iTerminal
    },
    {
        sizeof(struct usbCsOtDesc),
        0x24,   //CS_INTERFACE
        0x03,    //OUTPUT_TERMINAL
        0x02,   //bTerminalID
        0x0101, //Usb Streaming
        0x00,    //bAssocTerminal
        0x01,    //bSourceID (from input terminal)
        0       //iTerminal
    },
   /* Zero Bandwidth (alt setting 0) */
    {
        sizeof(struct usbStdIfDesc),
        USB_DESCRIPTOR_IFACE,
        1,    //bInterfaceNumber
        0,    //bAlternateSetting
        0,    //bNumEndpoints
        0x01,    //AUDIO
        0x02,    //AUDIOSTREAMING
        0,
        0    //iInterface
    },
   /* Audio Streaming descriptor (alt setting 1) */
    {
        sizeof(struct usbStdIfDesc),
        USB_DESCRIPTOR_IFACE,
        1,    //bInterfaceNumber
        1,    //bAlternateSetting
        1,    //bNumEndpoints
        0x01,    //AUDIO
        0x02,    //AUDIOSTREAMING
        0,
        0    //iInterface
    },
    {
        sizeof(struct usbAuCsAsDesc),
        0x24,   //CS_INTERFACE
        0x01,    //AS_GENERAL
        0x02,    //bTerminalLink (Out Terminal)
        0x01,    //bDelay
        0x0001    //wFormatTag (PCM format)
    },
    {
        sizeof(struct usbAuCsFmt1Desc),
        0x24,    //CS_INTERFACE
        0x02,    //FORMAT_TYPE
        0x01,    //FORMAT_TYPE1
        0x02,    //bNrChannels
        0x03,    //3 bytes/frame
        24,    //24 bits/sample
        0x01,    //bSamFreqType - One frequency supported
        {B3VAL(96000)}    //tSamFreq
    },
   /* IN ISO Endpoint 1 */
    {
        {sizeof(struct usbAuStdAsIsoEpDesc),
        USB_DESCRIPTOR_ENDPOINT,
        0x81,    //IN endpoint 1
        0x01,    //Isochronous, No synchronous, Data endpoint
        64,    //wMaxPacketSize
        9},    //packets per frame
        0,0    //bRefresh, bSynchAddress
    },
    {
        sizeof(struct usbAuCsAsIsoEpDesc),
        0x25,    //CS_ENDPOINT
        0x01,    //EP_GENERAL
        0x00,    //bmAttributes
        0x00,    //bLockDelayUnits
        0x0000    //wLockDelay
    }
};