path: root/usb/device/audio-speaker/audio-speaker.dir

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//------------------------------------------------------------------------------
/// \dir
///
/// !!!Purpose
///
/// This directory provides definitions, structs and functions for a USB Audio
/// Class device - USB audio-speaker demo, to implement an USB desktop speaker.
///
/// !!!Contents
/// There are two things for the implement of the audio-speaker device driver:
/// - Implement the audio-speaker driver structs and functions for the device,
///   to initialize, to handle audio class specific requests and dispach
///   standard requests in USBD callbacks, to read/write through assigned USB
///   endpoints,
/// - Create the audio-speaker device's descriptors that should be passed to
///   the USBDDriver instance on initialization, so that the host can 
///   recognize the device as a USB audio "desktop speaker" device.
///
/// For more information about what a particular group contains, please refer to
/// "USB Audio Speaker Device".
//------------------------------------------------------------------------------

/**
 \page "USB Audio Speaker Device"
 This page describes how to use the USB framework to produce a USB Audio Class
 Device driver.

 !!!References
 - "AT91 USB device framework"
 - "USB Device Enumeration"
 - <a href="http://www.usb.org/developers/docs/usb_20_040908.zip">
   Universal Serial Bus Revision 2.0 specification
   </a> (.zip file format, size 9.80 MB)
 - <a href="http://www.usb.org/developers/devclass_docs/audio10.pdf">
   Audio Device Document 1.0</a>
 - <a href="http://www.usb.org/developers/devclass_docs/frmts10.pdf">
   Audio Data Formats 1.0</a>
 - <a href="http://www.usb.org/developers/devclass_docs/termt10.pdf">
   Autio Terminal Types 1.0</a>

 !!!Audio Speaker Driver API
 - AUDDSpeakerDriver_Initialize
 - AUDDSpeakerDriver_RequestHandler
 - AUDDSpeakerDriver_Read

 !!!Audio Desktop Speaker Description
 The %device described here is a USB desktop speaker. It receives a stero
 %audio data stream from the Host over its Audio Streaming interface. The used
 Audio Data Format is 16-bit 48KHz 2-channel PCM (or mono 16-bit 32KHz PCM for
 sam7s chips). The following is the internal topology of the speaker.

 \image USBAudioSpeaker.png "USB Desktop Speaker Topology"

 The %audio function contains one Onput Terminal that represents the actual
 speaker output element, followed by the Digital-to-Analog Converter (DAC).
 The digital input stream of the host enters the %audio function through the
 single Input %Pin of the Output terminal. There is a Feature Unit on the
 %audio stream, to mute or unmute the speaker. The Input Terminal is the
 representation within the %audio fucntion of the USB OUT endpoint that
 eventually receives the %audio data stream from the Host. The internals of the
 %audio function are presented to the Host through the (mandatory) AudioControl
 interface wheras the USB OUT endpoint resides in the AudioStreaming interface.

 !!!Descriptor Hierarchy
 This USB Desktop Speaker %device includes the AudioControl interface
 (interface 0) and a single AudioStreaming interface (interface 1). The
 AudioStreaming interface features two alternate settings. The first alternate
 setting (Alternate Setting 0) has zero bandwidth associated with it so that
 switching to this alternate setting effectively frees all allocated bandwidth
 on the USB for this device. Zero bandwidth is indicated by the lack of a
 streaming endpoint. Alternate Setting 1 is the operational part of the
 interface and it has one isochronous OUT endpoint. Figure presents the
 descriptor hierarchy.

 \image UsbAudioSpeakerDescriptors.png "USB Desktop Speaker Hierarchy"

 !!!Descriptors
 The following sections present all the descriptors that are used to describe
 the %device.

 All descriptors are combined into a list and pass to USBDDriver_Initialize
 invoked in AUDDSpeakerDriver_Initialize.

\code
const USBDDriverDescriptors auddSpeakerDriverDescriptors;
\endcode

 !!Device Descriptor
\code
const USBDeviceDescriptor deviceDescriptor;
\endcode
||Offset||Field||Size||Value||Description
|0|bLength|1|0x12|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x01|DEVICE descriptor (USBGenericDescriptor_DEVICE).
|2|bcdUSB|2|0x0200|2.00 - current revision of USB specification.
|4|bDeviceClass|1|0x00|Device defined at interface level.
|5|bDeviceSubClass|1|0x00|Unused.
|6|bDeviceProtocol|1|0x00|Unused.
|7|bMaxPacketSize0|1|0x08|8 bytes (BOARD_USB_ENDPOINTS_MAXPACKETSIZE(0)).
|8|idVendor|2|0x03EB|Atmel Vendor ID (AUDDSpeakerDriverDescriptors_VENDORID).
|10|idProduct|2|0x6128|Product ID (AUDDSpeakerDriverDescriptors_PRODUCTID).
|12|bcdDevice|2|0x0100|Device Release Code\n
                      (AUDDSpeakerDriverDescriptors_RELEASE).
|14|iManufacturer|1|0x01|Index to manufacture name in Unicode\n
                         (manufacturerDescriptor).
|15|iProduct|1|0x02|Index to product name in Unicode (productDescriptor).
|16|iSerialNumber|1|0x03|Index to serial number in Unicode\n
                         (serialNumberDescriptor).
|17|bNumConfigurations|1|0x01|One configuration.

 !!Configuration Descriptor
\code
const AUDDSpeakerDriverConfigurationDescriptors configurationDescriptors;
\endcode
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x02|CONFIGURATION descriptor\n
                         (USBGenericDescriptor_CONFIGURATION).
|2|wTotalLength|2|0x????|Length of the total configuration block in bytes\n
                         including this descriptor\n
                         (AUDDSpeakerDriverConfigurationDescriptors)
|4|bNumInterfaces|1|0x02|Two interfaces.
|5|bConfigurationValue|1|0x01|ID of this configuration.
|6|iConfiguration|1|0x00|Unused.
|7|bmAttributes|1|0x??|BOARD_USB_BMATTRIBUTES
|8|bMaxPower|1|0x32|100mA Max. %power consumption.\n
                    USBConfigurationDescriptor_POWER(100)

 !!AudioControl Interface Descriptor
 The AudioControl interface describes the %device structure (%audio function
 topology) and is used to manipulate the Audio Controls.

 !Standard AC Interface Descriptor
 The AudioControl interface has no dedicated endpoints associated with it. It
 uses the default pipe (endpoint 0) for all communication purposes. Class-
 specific AudioControl Requests are sent using the default pipe. There is no
 Status Interrupt endpoint provided.

 See USBInterfaceDescriptor.
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x04|INTERFACE descriptor\n
                          (USBGenericDescriptor_INTERFACE).
|2|bInterfaceNumber|1|0x00|Index of this interface.
|3|bAlternateSetting|1|0x00|Index of this setting.
|4|bNumEndpoints|1|0x00|0 endpoints.
|5|bInterfaceClass|1|0x01|AUDIO (AUDControlInterfaceDescriptor_CLASS).
|6|bInterfaceSubClass|1|0x01|AUDIO_CONTROL\n
                             (AUDControlInterfaceDescriptor_SUBCLASS).
|7|bInterfaceProtocol|1|0x00|Unused.
|8|iInterface|1|0x00|Unused.

 !Class-specific AC Interface Descriptor
 The Class-specific AC interface descriptor is always headed by a Header
 descriptor that contains general information about the AudioControl interface.
 It contains all the pointers needed to describe the AudioInterface Collection,
 associated with the described %audio function.
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\n
                          (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubtype|1|0x01|HEADER subtype (AUDGenericDescriptor_HEADER).
|3|bcdADC|2|0x0100|Revision of class specification - 1.0
|5|wTotalLength|2|0x????|Total size of class specific descriptors\n
                         (AUDDSpeakerDriverAudioControlDescriptors).
|7|bInCollection|1|0x01|Number of streaming interfaces.
|8|baInterfaceNr(1)|1|0x01|AudioStreaming interface 1 belongs to this AudioControl interface.

 !Input Terminal Descriptor for playback
 This descriptor describes the Input Terminal that represents the USB pipe from
 the Host PC. Its Output Pin is connected to the Input Pin of the Feature Unit
 ...
||Offset||Field||Size||Value||Description
|0|bLength|1|0x0C|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\n
                         (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubType|1|0x02|INPUT_TERMINAL subtype\n
                             (AUDGenericDescriptor_INPUTTERMINAL).
|3|bTerminalID|1|0x00|ID of this Input Terminal\n
                     (AUDDSpeakerDriverDescriptors_INPUTTERMINAL).
|4|wTerminalType|2|0x0101|Terminal is USB stream\n
                         (AUDInputTerminalDescriptor_USBSTREAMING).
|6|bAssocTerminal|1|0x01|Associated to Output Terminal\n
                         (AUDDSpeakerDriverDescriptors_OUTPUTTERMINAL).
|7|bNrChannels|1|0x02|Two channel.
|8|wChannelConfig|2|0x0003|Left plus right front channel.
|10|iChannelNames|1|0x00|Unused.
|11|iTerminal|1|0x00|Unused.

 !Output Terminal Descriptor for playback
 ...
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\n
                         (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubType|1|0x03|OUTPUT_TERMINAL subtype\n
                             (AUDGenericDescriptor_OUTPUTTERMINAL).
|3|bTerminalID|1|0x01|ID of this Output Terminal\n
                     (AUDDSpeakerDriverDescriptors_OUTPUTTERMINAL).
|4|wTerminalType|2|0x0301|Terminal is Desktop speaker.
|6|bAssocTerminal|1|0x01|Associated to Input Terminal\n
                         (AUDDSpeakerDriverDescriptors_INPUTTERMINAL).
|7|bSourceID|1|0x02|From Feature Unit\n
                     (AUDDSpeakerDriverDescriptors_FEATUREUNIT).
|8|iTerminal|1|0x00|Unused.

 !Feature Unit Descriptor for playback
 ...
||Offset||Field||Size||Value||Description
|0|bLength|1|0x0A|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\n
                         (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubType|1|0x02|FEATURE_UNIT subtype\n
                             (AUDGenericDescriptor_FEATUREUNIT).
|3|bUnitID|1|0x02|ID of this Feature Unit\n
                  (AUDDSpeakerDriverDescriptors_FEATUREUNIT).
|4|bSourceID|1|0x00|From Input Terminal\n
                    (AUDDSpeakerDriverDescriptors_INPUTTERMINAL).
|5|bControlSize|1|0x01|1 byte per channel for controls
|6|bmaControls|3|0x000001|Master channel mute control, no other controls.
|9|iFeature|1|0x00|Unused.

 !!AudioStreaming Interface Descriptor
 The AudioStreaming interface has two possible alternate settings.

 !Zero-bandwidth Alternate Setting 0
 Alternate setting 0 is a zero-bandwidth setting, used to relinquish the
 claimed bandwidth on the bus when the microphone is not in use. It is the
 default setting after power-up. The zero bandwidth is implemented by
 specifying that this alternate setting of the interface has no endpoints
 associated with it (bNumEndpoints=0). The collection of descriptors for this
 alternate setting reduces to the standard interface descriptor.

 Standard AS Interface Descriptor (USBInterfaceDescriptor)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x04|INTERFACE descriptor\n
                          (USBGenericDescriptor_INTERFACE).
|2|bInterfaceNumber|1|0x01|Index of this interface.
|3|bAlternateSetting|1|0x00|Index of this setting.
|4|bNumEndpoints|1|0x00|0 endpoint.
|5|bInterfaceClass|1|0x01|AUDIO (AUDStreamingInterfaceDescriptor_CLASS).
|6|bInterfaceSubClass|1|0x02|AUDIO_STREAMING\n
                             (AUDStreamingInterfaceDescriptor_SUBCLASS).
|7|bInterfaceProtocol|1|0x00|Unused (AUDStreamingInterfaceDescriptor_PROTOCOL).
|8|iInterface|1|0x00|Unused.

 !Operational Alternate Setting 1
 Alternate setting 1 is the operational setting of the interface. It contains
 the standard and class-specific interface and endpoint descriptors.

 Standard AS Interface Descriptor (USBInterfaceDescriptor)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of USBInterfaceDescriptor in bytes.
|1|bDescriptorType|1|0x04|INTERFACE descriptor\n
                          (USBGenericDescriptor_INTERFACE).
|2|bInterfaceNumber|1|0x01|Index of this interface.
|3|bAlternateSetting|1|0x01|Index of this setting.
|4|bNumEndpoints|1|0x01|1 endpoint.
|5|bInterfaceClass|1|0x01|AUDIO (AUDStreamingInterfaceDescriptor_CLASS).
|6|bInterfaceSubClass|1|0x02|AUDIO_STREAMING\n
                             (AUDStreamingInterfaceDescriptor_SUBCLASS).
|7|bInterfaceProtocol|1|0x00|Unused (AUDStreamingInterfaceDescriptor_PROTOCOL).
|8|iInterface|1|0x00|Unused.

 Class-specific AS General Interface Descriptor (AUDStreamingInterfaceDescriptor)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x06|Size of AUDStreamingInterfaceDescriptor in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\n
                          (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubType|1|0x01|GENERAL subtype\n
                             (AUDStreamingInterfaceDescriptor_GENERAL).
|3|bTerminalLink|1|0x02|Unit ID of the Input Terminal\n
                        (AUDDSpeakerDriverDescriptors_INPUTTERMINAL).
|4|bDelay|1|0x00|No interface delay.
|5|wFormatTag|2|0x0001|PCM Format (AUDFormatTypeOneDescriptor_PCM).

 Type I Format Type Descriptor (AUDFormatTypeOneDescriptor1)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x0B|Size of AUDFormatTypeOneDescriptor1 in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\
                         (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubType|1|0x02|FORMAT_TYPE subtype\n
                             (AUDStreamingInterfaceDescriptor_FORMATTYPE).
|3|bFormatType|1|0x01|FORMAT_TYPE_I (AUDFormatTypeOneDescriptor_FORMATTYPEONE).
|4|bNrChannels|1|0x02|2 channels (AUDDSpeakerDriver_NUMCHANNELS).
|5|bSubFrameSize|1|0x02|Two bytes per audio subframe\n
                        (AUDDSpeakerDriver_BYTESPERSAMPLE).
|6|bBitResolution|1|0x10|16 bits per sample\n
                         (AUDDSpeakerDriver_BYTESPERSAMPLE * 2).
|7|bSamFreqType|1|0x01|One frequency supported.
|8|tSamFreq|3|4800|4800Hz (AUDDSpeakerDriver_SAMPLERATE).

 Standard %Endpoint Descriptor (AUDEndpointDescriptor)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of AUDFormatTypeOneDescriptor1 in bytes.
|1|bDescriptorType|1|0x24|ENDPOINT descriptor (USBGenericDescriptor_ENDPOINT).
|2|bEndpointAddress|1|0x04\nTest|OUT endpoint 4\n
                           See USBEndpointDescriptor_ADDRESS\n
                           See AUDDSpeakerDriverDescriptors_DATAOUT.
|3|bmAttributes|1|0x01|Isochronous, not shared\n
                       (USBEndpointDescriptor_ISOCHRONOUS).
|4|wMaxPacketSize|2|0x????|BOARD_USB_ENDPOINTS_MAXPACKETSIZE().
|6|bInterval|1|0x01|One packet per frame.
|7|bRefresh|1|0x00|Unused.
|8|bSynchAddress|1|0x00|Unused.

 Class-specific Isochronous Audio Data Endpoint Descriptor
 (AUDDataEndpointDescriptor)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x07|Size of AUDDataEndpointDescriptor in bytes.
|1|bDescriptorType|1|0x25|CS_ENDPOINT descriptor\n
                          (AUDGenericDescriptor_ENDPOINT).
|2|bDescriptorSubType|1|0x01|GENERAL subtype\n
                             (AUDDataEndpointDescriptor_SUBTYPE).
|3|bmAttributes|1|0x00|No sampling frequency control\n
                       no pitch control\n
                       no packet padding.
|4|bLockDelayUnits|1|0x00|Unused.
|5|wLockDelay|2|0x0000|Unused.

 !!String Descriptors
 There are three string descriptors available. The Manufacturer, Product and
 Serial Number descriptor.

 See manufacturerDescriptor, productDescriptor, serialNumberDescriptor.

 !!!Requests
 The Audio Speaker Driver supports all necessary standard requests, and some
 class-specific requests.

 USBDCallbacks_RequestReceived is used to filter all requests,
 AUDDSpeakerDriver_RequestHandler is invoked to handle Audio Class requests
 and forward standard request to AUDDSpeakerDriver_RequestHandler.

 !!Standard requests
 Set Interface request should be processed to control bandwidth allocation.

 !Set Interface
 USBDDriverCallbacks_InterfaceSettingChanged is re-implemented to handle the
 event.
||Offset||Field||Size||Value||Description
|0|bmRequestType|1|0x01|D7:0=Host to Device.\n
                        D6..5:00=Standard Request.\n
                        D4..0:00001=Recipient is interface.
|1|bRequest|1|0x0B|SET_INTERFACE.
|2|wValue|2|0x0000\n
              or\n
            0x0001|Zero bandwidth or normal isochronous operation.
|4|wIndex|2|0x0001|Interface number of the AudioStreaming interface.
|6|wLength|2|0x0000|No Parameter Block.

 !!Class-specific requests
 The only class-specific Request supported is the Set/Get Feature Unit Control
 Request. For mute control of the Feature Unit.

 !Set Feature Unit Control Request
||Offset||Field||Size||Value||Description
|0|bmRequestType|1|0x01|D7:0=Host to Device.\n
                        D6..5:01=Class Request.\n
                        D4..0:00001=Recipient is interface.
|1|bRequest|1|0x01|SET_CUR.
|2|wValue|2|0x0100|Mute control (AUDFeatureUnitRequest_MUTE) of\n
                   Master channel (AUDDSpeakerDriver_MASTERCHANNEL).
|4|wIndex|2|0x0200|Feature Unit (AUDDSpeakerDriverDescriptors_FEATUREUNIT)\n
                and\n
                AudioControl Interface (AUDDSpeakerDriverDescriptors_CONTROL).
|6|wLength|2|0x0001|Paramter Block Length
 
 The one-byte Parameter Block contains the new bMuted value for Feature
 Control.

 !Get Feature Unit Control Request
||Offset||Field||Size||Value||Description
|0|bmRequestType|1|0x01|D7:0=Host to Device.\n
                        D6..5:01=Class Request.\n
                        D4..0:00001=Recipient is interface.
|1|bRequest|1|0x81|GET_CUR.
|2|wValue|2|0x0100|Mute control (AUDFeatureUnitRequest_MUTE) of\n
                   Master channel (AUDDSpeakerDriver_MASTERCHANNEL).
|4|wIndex|2|0x0200|Feature Unit (AUDDSpeakerDriverDescriptors_FEATUREUNIT)\n
                and\n
                AudioControl Interface (AUDDSpeakerDriverDescriptors_CONTROL).
|6|wLength|2|0x0001|Paramter Block Length
 
 The one-byte Parameter Block contains the new bMuted value for Feature
 Control.

 !!!Modify the Device Driver
 You can modify your project from the USB Audio Demoes:
 - usb-device-audio-speaker-ac97-project
 - usb-device-audio-speaker-project

 !!Change Device ID and Display
 All Device ID and Display Strings are in AUDDSpeakerDriverDescriptors.c.

 !Device IDs
 You can find "Audio Speaker Device Codes"
 - AUDDSpeakerDriverDescriptors_VENDORID
 - AUDDSpeakerDriverDescriptors_PRODUCTID
 - AUDDSpeakerDriverDescriptors_RELEASE

 !Display Strings
 You can modify the string descriptors
 - manufacturerDescriptor
 - productDescriptor
 - serialNumberDescriptor

 !!!Add Recorder Function
 See "USB Audio Recorder".

*/

/**
 \page "USB Audio Recorder"
 This page describes how to add recorder function into the
 "USB Audio Speaker Device", So that you can learn how to extend your audio
 device driver from current Audio Speaker demo.

 !!!Description
 To add %audio record function, new Input Terminal, Output Termnial and Feature
 Unit is added.

 \image UsbAudioSpeakerRecorder.png "USB Desktop Speaker Hierarchy"


 !!!Modify the configuration descriptor:
 New descriptor for the terminals and unit should be added, and according
 interface, too.

 \image UsbAudioSpeakerRecorderDescriptors.png "USB Desktop Speaker Descriptors"



 !!Terminal Descriptors and Unit Descriptor
 ...
 !Input Terminal Descriptor for recording
 ...
||Offset||Field||Size||Value||Description
|0|bLength|1|0x0C|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\n
                          (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubType|1|0x03|INPUT_TERMINAL subtype\n
                             (AUDGenericDescriptor_INPUTTERMINAL).
|3|bTerminalID|1|0x03|ID of this Input Terminal\n
                      (AUDDSpeakerDriverDescriptors_INPUTTERMINAL_REC).
|4|wTerminalType|2|0x0403|Terminal is Speaker Phone\n
                         (AUDInputTerminalDescriptor_SPEAKERPHONE).
|6|bAssocTerminal|1|0x04|Associated to Output Terminal\n
                         (AUDDSpeakerDriverDescriptors_OUTPUTTERMINAL_REC).
|7|bNrChannels|1|0x02|Two channel.
|8|wChannelConfig|2|0x0003|Left plus right front channel.
|10|iChannelNames|1|0x00|Unused.
|11|iTerminal|1|0x00|Unused.

 !Output Terminal Descriptor for recording
 ...
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\n
                          (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubType|1|0x04|OUTPUT_TERMINAL subtype\n
                             (AUDGenericDescriptor_OUTPUTTERMINAL).
|3|bTerminalID|1|0x04|ID of this Output Terminal\n
                     (AUDDSpeakerDriverDescriptors_OUTPUTTERMINAL_REC).
|4|wTerminalType|2|0x0301|Terminal is USB stream\n
                         (AUDOutputTerminalDescriptor_USBTREAMING).
|6|bAssocTerminal|1|0x03|Associated to Input Terminal\n
                         (AUDDSpeakerDriverDescriptors_INPUTTERMINAL_REC).
|7|bSourceID|1|0x05|From Feature Unit\n
                     (AUDDSpeakerDriverDescriptors_FEATUREUNIT_REC).
|8|iTerminal|1|0x00|Unused.

 !Feature Unit Descriptor for recording
 ...
||Offset||Field||Size||Value||Description
|0|bLength|1|0x0A|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\n
                          (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubType|1|0x02|FEATURE_UNIT subtype\n
                             (AUDGenericDescriptor_FEATUREUNIT).
|3|bUnitID|1|0x05|ID of this Feature Unit\n
                   (AUDDSpeakerDriverDescriptors_FEATUREUNIT_REC).
|4|bSourceID|1|0x03|From Input Terminal\n
                     (AUDDSpeakerDriverDescriptors_INPUTTERMINAL_REC).
|5|bControlSize|1|0x01|1 byte per channel for controls
|6|bmaControls|3|0x000001|Master channel mute control, no other controls.
|9|iFeature|1|0x00|Unused.

 !!Interface Descriptor and Endpoint Descriptor for recording
 ...

 !Zero-bandwidth Alternate Setting 0
 Standard AS Interface Descriptor (USBInterfaceDescriptor)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of this descriptor, in bytes.
|1|bDescriptorType|1|0x04|INTERFACE descriptor\n
                         (USBGenericDescriptor_INTERFACE).
|2|bInterfaceNumber|1|0x02|Index of this interface.
|3|bAlternateSetting|1|0x00|Index of this setting.
|4|bNumEndpoints|1|0x00|0 endpoint.
|5|bInterfaceClass|1|0x01|AUDIO (AUDStreamingInterfaceDescriptor_CLASS).
|6|bInterfaceSubClass|1|0x02|AUDIO_STREAMING\n
                             (AUDStreamingInterfaceDescriptor_SUBCLASS).
|7|bInterfaceProtocol|1|0x00|Unused (AUDStreamingInterfaceDescriptor_PROTOCOL).
|8|iInterface|1|0x00|Unused.

 !Operational Alternate Setting 1
 Standard AS Interface Descriptor (USBInterfaceDescriptor)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of USBInterfaceDescriptor in bytes.
|1|bDescriptorType|1|0x04|INTERFACE descriptor\n
                         (USBGenericDescriptor_INTERFACE).
|2|bInterfaceNumber|1|0x02|Index of this interface.
|3|bAlternateSetting|1|0x01|Index of this setting.
|4|bNumEndpoints|1|0x01|1 endpoint.
|5|bInterfaceClass|1|0x01|AUDIO (AUDStreamingInterfaceDescriptor_CLASS).
|6|bInterfaceSubClass|1|0x02|AUDIO_STREAMING\n
                             (AUDStreamingInterfaceDescriptor_SUBCLASS).
|7|bInterfaceProtocol|1|0x00|Unused (AUDStreamingInterfaceDescriptor_PROTOCOL).
|8|iInterface|1|0x00|Unused.

 Class-specific AS General Interface Descriptor (AUDStreamingInterfaceDescriptor)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x06|Size of AUDStreamingInterfaceDescriptor in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\n
                         (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubType|1|0x01|GENERAL subtype\n
                             (AUDStreamingInterfaceDescriptor_GENERAL).
|3|bTerminalLink|1|0x02|Unit ID of the Input Terminal\n
                        (AUDDSpeakerDriverDescriptors_INPUTTERMINAL).
|4|bDelay|1|0x00|No interface delay.
|5|wFormatTag|2|0x0001|PCM Format (AUDFormatTypeOneDescriptor_PCM).

 Type I Format Type Descriptor (AUDFormatTypeOneDescriptor1)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x0B|Size of AUDFormatTypeOneDescriptor1 in bytes.
|1|bDescriptorType|1|0x24|CS_INTERFACE descriptor\n
                          (AUDGenericDescriptor_INTERFACE).
|2|bDescriptorSubType|1|0x02|FORMAT_TYPE subtype\n
                             (AUDStreamingInterfaceDescriptor_FORMATTYPE).
|3|bFormatType|1|0x01|FORMAT_TYPE_I (AUDFormatTypeOneDescriptor_FORMATTYPEONE).
|4|bNrChannels|1|0x02|2 channels (AUDDSpeakerDriver_NUMCHANNELS).
|5|bSubFrameSize|1|0x02|Two bytes per audio subframe\n
                        (AUDDSpeakerDriver_BYTESPERSAMPLE).
|6|bBitResolution|1|0x10|16 bits per sample\n
                         (AUDDSpeakerDriver_BYTESPERSAMPLE * 2).
|7|bSamFreqType|1|0x01|One frequency supported.
|8|tSamFreq|3|4800|4800Hz (AUDDSpeakerDriver_SAMPLERATE).

 Standard %Endpoint Descriptor (AUDEndpointDescriptor)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x09|Size of AUDFormatTypeOneDescriptor1 in bytes.
|1|bDescriptorType|1|0x24|ENDPOINT descriptor (USBGenericDescriptor_ENDPOINT).
|2|bEndpointAddress|1|0x85|IN endpoint 5\n
                           USBEndpointDescriptor_ADDRESS()\n
                           AUDDSpeakerDriverDescriptors_DATAIN
|3|bmAttributes|1|0x01|Isochronous, not shared\n
                       (USBEndpointDescriptor_ISOCHRONOUS).
|4|wMaxPacketSize|2|0x????|BOARD_USB_ENDPOINTS_MAXPACKETSIZE(5).
|6|bInterval|1|0x01|One packet per frame.
|7|bRefresh|1|0x00|Unused.
|8|bSynchAddress|1|0x00|Unused.

 Class-specific Isochronous Audio Data Endpoint Descriptor
 (AUDDataEndpointDescriptor)
||Offset||Field||Size||Value||Description
|0|bLength|1|0x07|Size of AUDDataEndpointDescriptor in bytes.
|1|bDescriptorType|1|0x25|CS_ENDPOINT descriptor\n
                          (AUDGenericDescriptor_ENDPOINT).
|2|bDescriptorSubType|1|0x01|GENERAL subtype\n
                             (AUDDataEndpointDescriptor_SUBTYPE).
|3|bmAttributes|1|0x00|No sampling frequency control\n
                       no pitch control\n
                       no packet padding
|4|bLockDelayUnits|1|0x00|Unused.
|5|wLockDelay|2|0x0000|Unused.

 !!!Modified methods for new function
 Several methods modified for new recorder function.

 !!Request handlers callbacks
 Add handler for new Interface, Terminal and Unit IDs.
 See AUDDSpeakerDriver_RequestHandler.

 !!Add function for recording USB stream
 See AUDDSpeakerDriver_Write.
*/