static uint8_t  usbd_audio_Init (void  *pdev, uint8_t cfgidx)
{  
    /* Open EP OUT/IN */
    DCD_EP_Open(pdev, AUDIO_OUT_EP, AUDIO_OUT_PACKET, USB_OTG_EP_ISOC);
    DCD_EP_Open(pdev, AUDIO_IN_EP, AUDIO_IN_PACKET, USB_OTG_EP_ISOC);
    
        DCD_EP_Tx (pdev, AUDIO_IN_EP, bufs, 3);
        
    /* Initialize the Audio output Hardware layer */
    if (AUDIO_OUT_fops.Init(USBD_AUDIO_FREQ, DEFAULT_VOLUME, 0) != USBD_OK){ return USBD_FAIL; }

    /* Prepare Out endpoint to receive audio data */
    DCD_EP_PrepareRx(pdev, AUDIO_OUT_EP, (uint8_t*)IsocOutBuff, AUDIO_OUT_PACKET);

    return USBD_OK;
}

/* Configuration 1 */
0x09, /* bLength */
USB_CONFIGURATION_DESCRIPTOR_TYPE, /* bDescriptorType */
LOBYTE(AUDIO_CONFIG_DESC_SIZE), /* wTotalLength 118 bytes*/
HIBYTE(AUDIO_CONFIG_DESC_SIZE),
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_INTERFACE_DESCRIPTOR_TYPE, /* 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 */
0x02, /* bNrChannels */
0x03, /* wChannelConfig 0x0003 - Left&Right; 0x0000 - Mono; 0x0004 - FrontCenter */
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) */
0x00, /* 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 */
0x02, /* wTerminalType 0x0302, headphones*/
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_INTERFACE_DESCRIPTOR_TYPE, /* 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_INTERFACE_DESCRIPTOR_TYPE, /* bDescriptorType */
0x01, /* bInterfaceNumber */
0x01, /* bAlternateSetting */
0x02, /* 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 */
0x00, /* bDelay */
0x01, /* wFormatTag AUDIO_FORMAT_PCM 0x0001*/
0x00,
/* 07 byte*/

/* USB Speaker Audio Type I Format Interface Descriptor */
0x0B, /* bLength */
AUDIO_INTERFACE_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_STREAMING_FORMAT_TYPE, /* bDescriptorSubtype */
AUDIO_FORMAT_TYPE_I, /* bFormatType */
0x02, /* bNrChannels */
AUDIO_FRAME_SIZE, /* bSubFrameSize; bytes per frame */
AUDIO_BITRESOLUTION, /* bBitResolution; bits per sample */
0x01, /* bSamFreqType only one frequency supported */
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_ENDPOINT_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_OUT_EP, /* bEndpointAddress 1 out endpoint, 0х01*/
USB_ENDPOINT_TYPE_ISOCHRONOUS | (1<<2), /* bmAttributes, isochronus, async */
AUDIO_PACKET_SZE(USBD_AUDIO_FREQ), /* wMaxPacketSize in Bytes (Freq(Samples)*2(Stereo)*2(HalfWord)) */
0x01, /* bInterval */
0x01, /* bRefresh */
AUDIO_IN_EP, /* bSynchAddress */
/* 09 byte*/

/* Endpoint - Audio Streaming Descriptor*/
AUDIO_STREAMING_ENDPOINT_DESC_SIZE, /* bLength */
AUDIO_ENDPOINT_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_ENDPOINT_GENERAL, /* bDescriptor */
0x00, /* bmAttributes, default 0x00 */
0x00, /* bLockDelayUnits */
0x00, /* wLockDelay */
0x00,
/* 07 byte*/


/* Endpoint 2 - Standard Descriptor, FB */
AUDIO_STANDARD_ENDPOINT_DESC_SIZE, /* bLength */
USB_ENDPOINT_DESCRIPTOR_TYPE, /* bDescriptorType */
AUDIO_IN_EP, /* bEndpointAddress 2, in FB endpoint, 0х81*/
USB_ENDPOINT_TYPE_ISOCHRONOUS|(1<<4), /* bmAttributes, feedback endpoint(explict) */
0x03, 0x00, /* wMaxPacketSize in Bytes */
0x01, /* bInterval */
0x05, /* bRefresh */
0x00, /* bSynchAddress */
/* 09 byte*/

/* Endpoint, EP3 ISO OUT - Standard Descriptor */\
  AUDIO_STANDARD_ENDPOINT_DESC_SIZE, /* bLength */\
  USB_ENDPOINT_DESCRIPTOR_TYPE,      /* bDescriptorType */\
  ADC_DATA_O_EP_LOG,               /* bEndpointAddress */\
  EP_ISO_OUT_ATTRIB,                 /* bmAttributes */\
  WBVAL(SAMPL_PER_FRAME_48 * SubFrameSize * 2), /* wMaxPacketSize */\
  0x01,                              /* bInterval */\
  0x00,                              /* bRefresh */\
  ADC_DATA_OUT_EP_SYNC_ADDR,         /* bSynchAddress */\

static uint8_t bufs[3];
uint32_t FB_rate = (USBD_AUDIO_FREQ == 44100)? (44 << 14) + ((1 << 14) / 10) : (USBD_AUDIO_FREQ / 1000) << 14;

bufs[0] = (uint8_t)(FB_rate);
bufs[1] = (uint8_t)(FB_rate >> 8);
bufs[2] = (uint8_t)(FB_rate >> 16);

DCD_EP_Flush(&USB_OTG_dev, AUDIO_IN_EP);
DCD_EP_Tx (&USB_OTG_dev, AUDIO_IN_EP, bufs, 3);

void USB_SOF_Event(void)
{
//STORE_DMA_SAMPLES();
STORE_DD_OUT_STATUS();
STORE_DD();

if ((USB_DeviceAddress != 0)&&(USB_Configuration != 0))
{
uint32_t numOutEP, numFBackEP, numInEP;

numOutEP = ProcessOutEP();
numFBackEP = ProcessFeedbackEP();
numInEP = ProcessInEP(numOutEP);

STORE_NUM_SAMPLES(numOutEP);

if ((iso_in_size == 44*4)||(iso_in_size == 48*4))
{
numFBackEP *=4;
}
else if ((iso_in_size == 44*6)||(iso_in_size == 48*6))
{
numFBackEP *=6;
}
else
{
//should never happen
}

STORE_NUM_FB_SAMPLES(numFBackEP / (1<<14));
STORE_NUM_IN_SAMPLES(numInEP);
}
SOF_EV();
}

uint32_t ProcessFeedbackEP()
{
int32_t fb = getFeedbackValue();

if (fb == 0)
{
DBG_INFO_MSG("ProcessFeedbackEP ERROR!!!! FeedbackRate = 0x%X =========================",FeedbackRate);
}
#if (USB_ADC_SYNC_MODE == USB_ADC_SYNC_MODE_EXPLISIT_FB)

IsoFBBuff = fb;

#if (USB_DMA_FB == 0) // sw copy for FEEDBACK EP

USB_WriteEP(ADC_F_BACK_EP_LOG, (uint8_t*)&IsoFBBuff, 3);

#else // (USB_DMA_FB == 0) DMA copy for FEEDBACK EP

//DD_ISO_FB_Mem[0] = 0;
//DD_ISO_FB_Mem[1] = (1<<16) | (1<<4); //isoc packet, length = 1 packet
DD_ISO_FB_Mem[0] = (uint32_t)DD_ISO_FB_Mem;
DD_ISO_FB_Mem[1] = (1<<16) | (1<<4) | (1<<2); //isoc packet, length = 1 packet
DD_ISO_FB_Mem[2] = (uint32_t)&IsoFBBuff;
DD_ISO_FB_Mem[3] = 0;
DD_ISO_FB_Mem[4] = (uint32_t)&InfoFBBuf;
InfoFBBuf = 3|0x10000;

#endif //(USB_DMA_FB == 0) SW/DMA copy for FEEDBACK EP
#endif //(USB_ADC_SYNC_MODE == USB_ADC_SYNC_MODE_EXPLISIT_FB)

return fb;
}