/*!
    \file    audio_core.c
    \brief   USB audio device class core functions

    \version 2020-08-01, V3.0.0, firmware for GD32F30x
    \version 2020-12-07, V3.0.1, firmware for GD32F30x
*/

/*
    Copyright (c) 2020, GigaDevice Semiconductor Inc.

    Redistribution and use in source and binary forms, with or without modification, 
are permitted provided that the following conditions are met:

    1. Redistributions of source code must retain the above copyright notice, this 
       list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright notice, 
       this list of conditions and the following disclaimer in the documentation 
       and/or other materials provided with the distribution.
    3. Neither the name of the copyright holder nor the names of its contributors 
       may be used to endorse or promote products derived from this software without 
       specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 
OF SUCH DAMAGE.
*/

#include "audio_out_itf.h"
#include "audio_core.h"
#include <string.h>

#define USBD_VID                     0x28E9U
#define USBD_PID                     0x9574U

#ifdef USE_USB_AUDIO_MICPHONE
extern volatile uint32_t count_data;
extern const char wavetestdata[];
#define LENGTH_DATA    (1747 * 32)
#endif

/* local function prototypes ('static') */
static uint8_t audio_init (usb_dev *udev, uint8_t config_index);
static uint8_t audio_deinit (usb_dev *udev, uint8_t config_index);
static uint8_t audio_req_handler (usb_dev *udev, usb_req *req);
static uint8_t audio_set_intf (usb_dev *udev, usb_req *req);
static uint8_t audio_ctlx_out (usb_dev *udev);
static uint8_t audio_data_in (usb_dev *udev, uint8_t ep_num);
static uint8_t audio_data_out (usb_dev *udev, uint8_t ep_num);
static uint8_t usbd_audio_sof (usb_dev *udev);

usb_class_core usbd_audio_cb = {
    .init      = audio_init,
    .deinit    = audio_deinit,
    .req_proc  = audio_req_handler,
    .set_intf  = audio_set_intf,
    .ctlx_out  = audio_ctlx_out,
    .data_in   = audio_data_in,
    .data_out  = audio_data_out,
    .SOF       = usbd_audio_sof
};

#define VOL_MIN        0U    /* Volume Minimum Value */
#define VOL_MAX        100U  /* Volume Maximum Value */
#define VOL_RES        1U    /* Volume Resolution */
#define VOL_0dB        70U   /* 0dB is in the middle of VOL_MIN and VOL_MAX */

/* note:it should use the c99 standard when compiling the below codes */
/* USB standard device descriptor */
const usb_desc_dev audio_dev_desc =
{
    .header = 
     {
         .bLength          = USB_DEV_DESC_LEN, 
         .bDescriptorType  = USB_DESCTYPE_DEV
     },
    .bcdUSB                = 0x0200U,
    .bDeviceClass          = 0x00U,
    .bDeviceSubClass       = 0x00U,
    .bDeviceProtocol       = 0x00U,
    .bMaxPacketSize0       = USB_FS_EP0_MAX_LEN,
    .idVendor              = USBD_VID,
    .idProduct             = USBD_PID,
    .bcdDevice             = 0x0100U,
    .iManufacturer         = STR_IDX_MFC,
    .iProduct              = STR_IDX_PRODUCT,
    .iSerialNumber         = STR_IDX_SERIAL,
    .bNumberConfigurations = USBD_CFG_MAX_NUM
};

/* USB device configuration descriptor */
const usb_desc_config_set audio_config_set = 
{
    .config = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_config), 
             .bDescriptorType = USB_DESCTYPE_CONFIG 
         },
        .wTotalLength         = AUDIO_CONFIG_DESC_SET_LEN,
        .bNumInterfaces       = 0x01U + CONFIG_DESC_AS_ITF_COUNT,
        .bConfigurationValue  = 0x01U,
        .iConfiguration       = 0x00U,
        .bmAttributes         = 0xC0U,
        .bMaxPower            = 0x32U
    },

    .std_itf = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_itf), 
             .bDescriptorType = USB_DESCTYPE_ITF 
         },
         .bInterfaceNumber    = 0x00U,
         .bAlternateSetting   = 0x00U,
         .bNumEndpoints       = 0x00U,
         .bInterfaceClass     = USB_CLASS_AUDIO,
         .bInterfaceSubClass  = AUDIO_SUBCLASS_CONTROL,
         .bInterfaceProtocol  = AUDIO_PROTOCOL_UNDEFINED,
         .iInterface          = 0x00U
    },

    .ac_itf = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_AC_itf), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE 
         },
         .bDescriptorSubtype  = 0x01U,
         .bcdADC              = 0x0100U,
         .wTotalLength        = AC_ITF_TOTAL_LEN,
         .bInCollection       = CONFIG_DESC_AS_ITF_COUNT,
#ifdef USE_USB_AUDIO_MICPHONE
         .baInterfaceNr0       = 0x01U,
#endif
#ifdef USE_USB_AUDIO_SPEAKER
         .baInterfaceNr1       = 0x02U
#endif
    },

#ifdef USE_USB_AUDIO_MICPHONE
    .mic_in_terminal = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_input_terminal), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE
         },
         .bDescriptorSubtype  = 0x02U,
         .bTerminalID         = 0x01U,
         .wTerminalType       = 0x0201U,
         .bAssocTerminal      = 0x00U,
         .bNrChannels         = 0x02U,
         .wChannelConfig      = 0x0003U,
         .iChannelNames       = 0x00U,
         .iTerminal           = 0x00U
    },

    .mic_feature_unit = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_mono_feature_unit), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE 
         },
         .bDescriptorSubtype  = AUDIO_CONTROL_FEATURE_UNIT,
         .bUnitID             = AUDIO_IN_STREAMING_CTRL,
         .bSourceID           = 0x01U,
         .bControlSize        = 0x01U,
         .bmaControls0        = AUDIO_CONTROL_MUTE,
         .bmaControls1        = AUDIO_CONTROL_VOLUME,
         .iFeature            = 0x00U
    },

    .mic_out_terminal = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_output_terminal), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE
         },
         .bDescriptorSubtype  = AUDIO_CONTROL_OUTPUT_TERMINAL,
         .bTerminalID         = 0x03U,
         .wTerminalType       = 0x0101U,
         .bAssocTerminal      = 0x00U,
         .bSourceID           = 0x02U,
         .iTerminal           = 0x00U
    },
#endif

#ifdef USE_USB_AUDIO_SPEAKER
    .speak_in_terminal = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_input_terminal), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE
         },
         .bDescriptorSubtype  = AUDIO_CONTROL_INPUT_TERMINAL,
         .bTerminalID         = 0x04U,
         .wTerminalType       = 0x0101U,
         .bAssocTerminal      = 0x00U,
         .bNrChannels         = 0x02U,
         .wChannelConfig      = 0x0003U,
         .iChannelNames       = 0x00U,
         .iTerminal           = 0x00U
    },

    .speak_feature_unit = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_mono_feature_unit), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE 
         },
         .bDescriptorSubtype  = AUDIO_CONTROL_FEATURE_UNIT,
         .bUnitID             = AUDIO_OUT_STREAMING_CTRL,
         .bSourceID           = 0x04U,
         .bControlSize        = 0x01U,
         .bmaControls0        = AUDIO_CONTROL_MUTE,
         .bmaControls1        = AUDIO_CONTROL_VOLUME,
         .iFeature            = 0x00U
    },

    .speak_out_terminal = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_output_terminal), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE
         },
         .bDescriptorSubtype  = AUDIO_CONTROL_OUTPUT_TERMINAL,
         .bTerminalID         = 0x06U,
         .wTerminalType       = 0x0301U,
         .bAssocTerminal      = 0x00U,
         .bSourceID           = 0x05U,
         .iTerminal           = 0x00U
    },
#endif

#ifdef USE_USB_AUDIO_MICPHONE
    .mic_std_as_itf_zeroband = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_itf), 
             .bDescriptorType = USB_DESCTYPE_ITF 
         },
         .bInterfaceNumber    = 0x01U,
         .bAlternateSetting   = 0x00U,
         .bNumEndpoints       = 0x00U,
         .bInterfaceClass     = USB_CLASS_AUDIO,
         .bInterfaceSubClass  = AUDIO_SUBCLASS_AUDIOSTREAMING,
         .bInterfaceProtocol  = AUDIO_PROTOCOL_UNDEFINED,
         .iInterface          = 0x00U
    },

    .mic_std_as_itf_opera = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_itf), 
             .bDescriptorType = USB_DESCTYPE_ITF 
         },
         .bInterfaceNumber    = 0x01U,
         .bAlternateSetting   = 0x01U,
         .bNumEndpoints       = 0x01U,
         .bInterfaceClass     = USB_CLASS_AUDIO,
         .bInterfaceSubClass  = AUDIO_SUBCLASS_AUDIOSTREAMING,
         .bInterfaceProtocol  = AUDIO_PROTOCOL_UNDEFINED,
         .iInterface          = 0x00U
    },

    .mic_as_itf = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_AS_itf), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE 
         },
         .bDescriptorSubtype  = AUDIO_STREAMING_GENERAL,
         .bTerminalLink       = 0x03U,
         .bDelay              = 0x01U,
         .wFormatTag          = 0x0001U,
    },

    .mic_format_typeI = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_format_type), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE 
         },
         .bDescriptorSubtype  = AUDIO_STREAMING_FORMAT_TYPE,
         .bFormatType         = AUDIO_FORMAT_TYPE_I,
         .bNrChannels         = MIC_IN_CHANNEL_NBR,
         .bSubFrameSize       = 0x02U,
         .bBitResolution      = MIC_IN_BIT_RESOLUTION,
         .bSamFreqType        = 0x01U,
         .bSamFreq[0]         = (uint8_t)USBD_MIC_FREQ,
         .bSamFreq[1]         = USBD_MIC_FREQ >> 8U,
         .bSamFreq[2]         = USBD_MIC_FREQ >> 16U
    },

    .mic_std_endpoint = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_std_ep), 
             .bDescriptorType = USB_DESCTYPE_EP 
         },
         .bEndpointAddress    = AUDIO_IN_EP,
         .bmAttributes        = USB_ENDPOINT_TYPE_ISOCHRONOUS,
         .wMaxPacketSize      = MIC_IN_PACKET,
         .bInterval           = 0x01U,
         .bRefresh            = 0x00U,
         .bSynchAddress       = 0x00U
    },

    .mic_as_endpoint = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_AS_ep), 
             .bDescriptorType = AUDIO_DESCTYPE_ENDPOINT 
         },
         .bDescriptorSubtype  = AUDIO_ENDPOINT_GENERAL,
         .bmAttributes        = 0x00U,
         .bLockDelayUnits     = 0x00U,
         .wLockDelay          = 0x0000U,
    },
#endif

#ifdef USE_USB_AUDIO_SPEAKER
    .speak_std_as_itf_zeroband = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_itf), 
             .bDescriptorType = USB_DESCTYPE_ITF 
         },
         .bInterfaceNumber    = 0x02U,
         .bAlternateSetting   = 0x00U,
         .bNumEndpoints       = 0x00U,
         .bInterfaceClass     = USB_CLASS_AUDIO,
         .bInterfaceSubClass  = AUDIO_SUBCLASS_AUDIOSTREAMING,
         .bInterfaceProtocol  = AUDIO_PROTOCOL_UNDEFINED,
         .iInterface          = 0x00U
    },

    .speak_std_as_itf_opera = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_itf), 
             .bDescriptorType = USB_DESCTYPE_ITF 
         },
         .bInterfaceNumber    = 0x02U,
         .bAlternateSetting   = 0x01U,
         .bNumEndpoints       = 0x01U,
         .bInterfaceClass     = USB_CLASS_AUDIO,
         .bInterfaceSubClass  = AUDIO_SUBCLASS_AUDIOSTREAMING,
         .bInterfaceProtocol  = AUDIO_PROTOCOL_UNDEFINED,
         .iInterface          = 0x00U
    },

    .speak_as_itf = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_AS_itf), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE 
         },
         .bDescriptorSubtype  = AUDIO_STREAMING_GENERAL,
         .bTerminalLink       = 0x04U,
         .bDelay              = 0x01U,
         .wFormatTag          = 0x0001U,
    },

    .speak_format_typeI = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_format_type), 
             .bDescriptorType = AUDIO_DESCTYPE_INTERFACE 
         },
         .bDescriptorSubtype  = AUDIO_STREAMING_FORMAT_TYPE,
         .bFormatType         = AUDIO_FORMAT_TYPE_I,
         .bNrChannels         = SPEAKER_OUT_CHANNEL_NBR,
         .bSubFrameSize       = 0x02U,
         .bBitResolution      = SPEAKER_OUT_BIT_RESOLUTION,
         .bSamFreqType        = 0x01U,
         .bSamFreq[0]         = (uint8_t)USBD_SPEAKER_FREQ,
         .bSamFreq[1]         = USBD_SPEAKER_FREQ >> 8U,
         .bSamFreq[2]         = USBD_SPEAKER_FREQ >> 16U
    },

    .speak_std_endpoint = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_std_ep), 
             .bDescriptorType = USB_DESCTYPE_EP 
         },
         .bEndpointAddress    = AUDIO_OUT_EP,
         .bmAttributes        = USB_ENDPOINT_TYPE_ISOCHRONOUS,
         .wMaxPacketSize      = SPEAKER_OUT_PACKET,
         .bInterval           = 0x01U,
         .bRefresh            = 0x00U,
         .bSynchAddress       = 0x00U
    },

    .speak_as_endpoint = 
    {
        .header = 
         {
             .bLength         = sizeof(usb_desc_AS_ep), 
             .bDescriptorType = AUDIO_DESCTYPE_ENDPOINT 
         },
         .bDescriptorSubtype  = AUDIO_ENDPOINT_GENERAL,
         .bmAttributes        = 0x00U,
         .bLockDelayUnits     = 0x00U,
         .wLockDelay          = 0x0000U,
    }
#endif
};

/* USB language ID descriptor */
static const usb_desc_LANGID usbd_language_id_desc = 
{
    .header = 
     {
         .bLength         = sizeof(usb_desc_LANGID), 
         .bDescriptorType = USB_DESCTYPE_STR
     },

    .wLANGID = ENG_LANGID
};

/* USB manufacture string */
static const usb_desc_str manufacturer_string = 
{
    .header = 
     {
         .bLength         = USB_STRING_LEN(10), 
         .bDescriptorType = USB_DESCTYPE_STR,
     },
    .unicode_string = {'G', 'i', 'g', 'a', 'D', 'e', 'v', 'i', 'c', 'e'}
};

/* USB product string */
static const usb_desc_str product_string = 
{
    .header = 
     {
         .bLength         = USB_STRING_LEN(14), 
         .bDescriptorType = USB_DESCTYPE_STR,
     },
    .unicode_string = {'G', 'D', '3', '2', '-', 'U', 'S', 'B', '_', 'A', 'u', 'd', 'i', 'o'}
};

/* USBD serial string */
static usb_desc_str serial_string = 
{
    .header = 
     {
         .bLength         = USB_STRING_LEN(12), 
         .bDescriptorType = USB_DESCTYPE_STR,
     }
};

/* USB string descriptor */
void *const usbd_audio_strings[] = 
{
    [STR_IDX_LANGID]  = (uint8_t *)&usbd_language_id_desc,
    [STR_IDX_MFC]     = (uint8_t *)&manufacturer_string,
    [STR_IDX_PRODUCT] = (uint8_t *)&product_string,
    [STR_IDX_SERIAL]  = (uint8_t *)&serial_string
};

usb_desc audio_desc = {
    .dev_desc    = (uint8_t *)&audio_dev_desc,
    .config_desc = (uint8_t *)&audio_config_set,
    .strings     = usbd_audio_strings
};

/*!
    \brief      initialize the AUDIO device
    \param[in]  udev: pointer to USB device instance
    \param[in]  config_index: configuration index
    \param[out] none
    \retval     USB device operation status
*/
static uint8_t audio_init (usb_dev *udev, uint8_t config_index)
{
    static usbd_audio_handler audio_handler;

    memset((void *)&audio_handler, 0, sizeof(usbd_audio_handler));

#ifdef USE_USB_AUDIO_MICPHONE
{
    usb_desc_std_ep std_ep = audio_config_set.mic_std_endpoint;

    usb_desc_ep ep = {
        .header           = std_ep.header,
        .bEndpointAddress = std_ep.bEndpointAddress,
        .bmAttributes     = std_ep.bmAttributes,
        .wMaxPacketSize   = std_ep.wMaxPacketSize,
        .bInterval        = std_ep.bInterval 
    };

    /* initialize Tx endpoint */
    usbd_ep_setup (udev, &ep);
}
#endif

#ifdef USE_USB_AUDIO_SPEAKER
{
    audio_handler.isoc_out_rdptr = audio_handler.isoc_out_buff;
    audio_handler.isoc_out_wrptr = audio_handler.isoc_out_buff;

    usb_desc_std_ep std_ep = audio_config_set.speak_std_endpoint;

    usb_desc_ep ep = {
        .header           = std_ep.header,
        .bEndpointAddress = std_ep.bEndpointAddress,
        .bmAttributes     = std_ep.bmAttributes,
        .wMaxPacketSize   = std_ep.wMaxPacketSize,
        .bInterval        = std_ep.bInterval 
    };

    /* initialize Rx endpoint */
    usbd_ep_setup (udev, &ep);

    /* initialize the audio output hardware layer */
    if (USBD_OK != audio_out_fops.audio_init(USBD_AUDIO_FREQ_16K, DEFAULT_VOLUME, 0U)) {
        return USBD_FAIL;
    }

    /* prepare OUT endpoint to receive audio data */
    usbd_ep_recev (udev, AUDIO_OUT_EP, (uint8_t*)audio_handler.isoc_out_buff, SPEAKER_OUT_PACKET);
}
#endif

    udev->dev.class_data[USBD_AUDIO_INTERFACE] = (void *)&audio_handler;

    return USBD_OK;
}

/*!
    \brief      de-initialize the AUDIO device
    \param[in]  udev: pointer to USB device instance
    \param[in]  config_index: configuration index
    \param[out] none
    \retval     USB device operation status
*/
static uint8_t audio_deinit (usb_dev *udev, uint8_t config_index)
{
#ifdef USE_USB_AUDIO_MICPHONE
    /* deinitialize AUDIO endpoints */
    usbd_ep_clear(udev, AUDIO_IN_EP);
#endif

#ifdef USE_USB_AUDIO_SPEAKER
    /* deinitialize AUDIO endpoints */
    usbd_ep_clear(udev, AUDIO_OUT_EP);

    /* deinitialize the audio output hardware layer */
    if (USBD_OK != audio_out_fops.audio_deinit(0U)) {
        return USBD_FAIL;
    }
#endif

    return USBD_OK;
}

/*!
    \brief      handle the AUDIO class-specific requests
    \param[in]  udev: pointer to USB device instance
    \param[in]  req: device class-specific request
    \param[out] none
    \retval     USB device operation status
*/
static uint8_t audio_req_handler (usb_dev *udev, usb_req *req)
{
    uint8_t status = REQ_NOTSUPP;

    usbd_audio_handler *audio = (usbd_audio_handler *)udev->dev.class_data[USBD_AUDIO_INTERFACE];

    usb_transc *transc_in = &udev->dev.transc_in[0];
    usb_transc *transc_out = &udev->dev.transc_out[0];

    switch (req->bRequest) {
    case AUDIO_REQ_GET_CUR:
        transc_in->xfer_buf = audio->audioctl;
        transc_in->remain_len = req->wLength;

        status = REQ_SUPP;
        break;

    case AUDIO_REQ_SET_CUR:
        if (req->wLength) {
            transc_out->xfer_buf = audio->audioctl;
            transc_out->remain_len = req->wLength;

            udev->dev.class_core->command = AUDIO_REQ_SET_CUR;

            audio->audioctl_len = req->wLength;
            audio->audioctl_unit = BYTE_HIGH(req->wIndex);

            status = REQ_SUPP;
        }
        break;
        
    case AUDIO_REQ_GET_MIN:
        *((uint16_t *)audio->audioctl) = VOL_MIN;
        transc_in->xfer_buf = audio->audioctl;
        transc_in->remain_len = req->wLength;
        status = REQ_SUPP;
        break;

    case AUDIO_REQ_GET_MAX:
        *((uint16_t *)audio->audioctl) = VOL_MAX;
        transc_in->xfer_buf = audio->audioctl;
        transc_in->remain_len = req->wLength;
        status = REQ_SUPP;
        break;

    case AUDIO_REQ_GET_RES:
        *((uint16_t *)audio->audioctl) = VOL_RES;
        transc_in->xfer_buf = audio->audioctl;
        transc_in->remain_len = req->wLength;
        status = REQ_SUPP;
        break;

    default:
        break;
    }

    return status;
}

/*!
    \brief      handle the AUDIO set interface requests
    \param[in]  udev: pointer to USB device instance
    \param[in]  req: device class-specific request
    \param[out] none
    \retval     USB device operation status
*/
static uint8_t audio_set_intf(usb_dev *udev, usb_req *req)
{
    udev->dev.class_core->alter_set = req->wValue;

    return USBD_OK;
}

/*!
    \brief      handles the control transfer OUT callback
    \param[in]  udev: pointer to USB device instance
    \param[out] none
    \retval     USB device operation status
*/
static uint8_t audio_ctlx_out (usb_dev *udev)
{
#ifdef USE_USB_AUDIO_SPEAKER
    usbd_audio_handler *audio = (usbd_audio_handler *)udev->dev.class_data[USBD_AUDIO_INTERFACE];

    /* handles audio control requests data */
    /* check if an audio_control request has been issued */
    if (AUDIO_REQ_SET_CUR == udev->dev.class_core->command) {
        /* in this driver, to simplify code, only SET_CUR request is managed */

        /* check for which addressed unit the audio_control request has been issued */
        if (AUDIO_OUT_STREAMING_CTRL == audio->audioctl_unit) {
            /* in this driver, to simplify code, only one unit is manage */

            /* call the audio interface mute function */
            audio_out_fops.audio_mute_ctl(audio->audioctl[0]);

            /* reset the audioctl_cmd variable to prevent re-entering this function */
            udev->dev.class_core->command = 0U;

            audio->audioctl_len = 0U;
        }
    }
#endif

    return USBD_OK;
}

/*!
    \brief      handles the audio IN data stage
    \param[in]  udev: pointer to USB device instance
    \param[in]  ep_num: endpoint number
    \param[out] none
    \retval     USB device operation status
*/
static uint8_t audio_data_in (usb_dev *udev, uint8_t ep_num)
{
#ifdef USE_USB_AUDIO_MICPHONE
        if(count_data < LENGTH_DATA){
            /* Prepare next buffer to be sent: dummy data */
            usbd_ep_send(udev, AUDIO_IN_EP,(uint8_t*)&wavetestdata[count_data],MIC_IN_PACKET);
            count_data += MIC_IN_PACKET;
        } else {
            usbd_ep_send(udev, AUDIO_IN_EP,(uint8_t*)wavetestdata,MIC_IN_PACKET);
            count_data = MIC_IN_PACKET;
        }
#endif

    return USBD_OK;
}

/*!
    \brief      handles the audio OUT data stage
    \param[in]  udev: pointer to USB device instance
    \param[in]  ep_num: endpoint number
    \param[out] none
    \retval     USB device operation status
*/
static uint8_t audio_data_out (usb_dev *udev, uint8_t ep_num)
{
#ifdef USE_USB_AUDIO_SPEAKER
    usbd_audio_handler *audio = (usbd_audio_handler *)udev->dev.class_data[USBD_AUDIO_INTERFACE];

    /* increment the Buffer pointer or roll it back when all buffers are full */
    if (audio->isoc_out_wrptr >= (audio->isoc_out_buff + (SPEAKER_OUT_PACKET * OUT_PACKET_NUM))) {
        /* all buffers are full: roll back */
        audio->isoc_out_wrptr = audio->isoc_out_buff;
    } else {
        /* increment the buffer pointer */
        audio->isoc_out_wrptr += SPEAKER_OUT_PACKET;
    }

    /* Toggle the frame index */  
    udev->dev.transc_out[ep_num].frame_num = 
    (udev->dev.transc_out[ep_num].frame_num)? 0U:1U;

    /* prepare out endpoint to receive next audio packet */
    usbd_ep_recev (udev, AUDIO_OUT_EP, (uint8_t*)(audio->isoc_out_wrptr), SPEAKER_OUT_PACKET);

    /* trigger the start of streaming only when half buffer is full */
    if ((0U == audio->play_flag) && (audio->isoc_out_wrptr >= (audio->isoc_out_buff + ((SPEAKER_OUT_PACKET * OUT_PACKET_NUM) / 2U)))) {
        /* enable start of streaming */
        audio->play_flag = 1U;
    }
#endif

    return USBD_OK;
}

/*!
    \brief      handles the SOF event (data buffer update and synchronization)
    \param[in]  udev: pointer to USB device instance
    \param[out] none
    \retval     USB device operation status
*/
static uint8_t usbd_audio_sof (usb_dev *udev)
{
#ifdef USE_USB_AUDIO_SPEAKER
    usbd_audio_handler *audio = (usbd_audio_handler *)udev->dev.class_data[USBD_AUDIO_INTERFACE];

    /* check if there are available data in stream buffer.
       in this function, a single variable (play_flag) is used to avoid software delays.
       the play operation must be executed as soon as possible after the SOF detection. */
    if (audio->play_flag) {
        /* start playing received packet */
        audio_out_fops.audio_cmd((uint8_t*)(audio->isoc_out_rdptr),  /* samples buffer pointer */
                                 SPEAKER_OUT_PACKET,          /* number of samples in Bytes */
                                 AUDIO_CMD_PLAY);             /* command to be processed */

        /* increment the Buffer pointer or roll it back when all buffers all full */
        if (audio->isoc_out_rdptr >= (audio->isoc_out_buff + (SPEAKER_OUT_PACKET * OUT_PACKET_NUM))) {
            /* roll back to the start of buffer */
            audio->isoc_out_rdptr = audio->isoc_out_buff;
        } else {
            /* increment to the next sub-buffer */
            audio->isoc_out_rdptr += SPEAKER_OUT_PACKET;
        }

        /* if all available buffers have been consumed, stop playing */
        if (audio->isoc_out_rdptr == audio->isoc_out_wrptr) {
            /* Pause the audio stream */
            audio_out_fops.audio_cmd((uint8_t*)(audio->isoc_out_buff),   /* samples buffer pointer */
                                     SPEAKER_OUT_PACKET,          /* number of samples in Bytes */
                                     AUDIO_CMD_PAUSE);            /* command to be processed */

            /* stop entering play loop */
            audio->play_flag = 0U;

            /* reset buffer pointers */
            audio->isoc_out_rdptr = audio->isoc_out_buff;
            audio->isoc_out_wrptr = audio->isoc_out_buff;
        }
    }
#endif

    return USBD_OK;
}