Transistor Gijutsu, October 2014, Special Features Chapter 9, Software of the Function Generator トランジスタ技術2014年10月号 特集第9章のソフトウェア わがまま波形発生器のソフトウェア

Dependencies:   USBDevice mbed

Information

tg_201410s8_AD7714 トランジスタ技術 2014年 10月号 第9章のソフトウェア

Program for Section 9 in October. 2014 issue of the Transistor Gijutsu
(Japanese electronics magazine)

概要

このプログラムは、ソフトウエアDDSにより、任意の波形を出力(2ch)します。 特徴は次のとおりです。

  • PWM出力をDAコンバータとして利用します。
  • 周波数や波形、バースト条件などを個別に設定できる独立した出力を2チャネル持っています。
  • 周波数分解能0.023mHz
  • 周波数範囲0.023mHz~10kHz
  • 各チャネルにそれぞれ、波形の先頭で出力されるトリガ出力があります。
  • 出力波形を関数で定義できます。
  • 休止波数、出力波数、を設定することでバースト波形が出力できます。

ファイル

このソフトウエアは、次のファイルから構成されています。

  • DDS.cpp - DDSによる波形発生
  • main.cpp - main()関数

詳細については、10月号の記事および上記ファイル中のコメントを参照してください。

Revision:
0:f1ecca559ec3
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/USBDevice/USBAudio/USBAudio.cpp	Fri Aug 29 08:33:17 2014 +0000
@@ -0,0 +1,618 @@
+/* Copyright (c) 2010-2011 mbed.org, MIT License
+*
+* Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+* and associated documentation files (the "Software"), to deal in the Software without
+* restriction, including without limitation the rights to use, copy, modify, merge, publish,
+* distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
+* Software is furnished to do so, subject to the following conditions:
+*
+* The above copyright notice and this permission notice shall be included in all copies or
+* substantial portions of the Software.
+*
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
+* BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+#include "stdint.h"
+#include "USBAudio.h"
+#include "USBAudio_Types.h"
+
+
+
+USBAudio::USBAudio(uint32_t frequency_in, uint8_t channel_nb_in, uint32_t frequency_out, uint8_t channel_nb_out, uint16_t vendor_id, uint16_t product_id, uint16_t product_release): USBDevice(vendor_id, product_id, product_release) {
+    mute = 0;
+    volCur = 0x0080;
+    volMin = 0x0000;
+    volMax = 0x0100;
+    volRes = 0x0004;
+    available = false;
+
+    FREQ_IN = frequency_in;
+    FREQ_OUT = frequency_out;
+
+    this->channel_nb_in = channel_nb_in;
+    this->channel_nb_out = channel_nb_out;
+
+    // stereo -> *2, mono -> *1
+    PACKET_SIZE_ISO_IN = (FREQ_IN / 500) * channel_nb_in;
+    PACKET_SIZE_ISO_OUT = (FREQ_OUT / 500) * channel_nb_out;
+
+    // STEREO -> left and right
+    channel_config_in = (channel_nb_in == 1) ? CHANNEL_M : CHANNEL_L + CHANNEL_R;
+    channel_config_out = (channel_nb_out == 1) ? CHANNEL_M : CHANNEL_L + CHANNEL_R;
+
+    SOF_handler = false;
+
+    buf_stream_out = NULL;
+    buf_stream_in = NULL;
+
+    interruptOUT = false;
+    writeIN = false;
+    interruptIN = false;
+    available = false;
+
+    volume = 0;
+
+    // connect the device
+    USBDevice::connect();
+}
+
+bool USBAudio::read(uint8_t * buf) {
+    buf_stream_in = buf;
+    SOF_handler = false;
+    while (!available || !SOF_handler);
+    available = false;
+    return true;
+}
+
+bool USBAudio::readNB(uint8_t * buf) {
+    buf_stream_in = buf;
+    SOF_handler = false;
+    while (!SOF_handler);
+    if (available) {
+        available = false;
+        buf_stream_in = NULL;
+        return true;
+    }
+    return false;
+}
+
+bool USBAudio::readWrite(uint8_t * buf_read, uint8_t * buf_write) {
+    buf_stream_in = buf_read;
+    SOF_handler = false;
+    writeIN = false;
+    if (interruptIN) {
+        USBDevice::writeNB(EP3IN, buf_write, PACKET_SIZE_ISO_OUT, PACKET_SIZE_ISO_OUT);
+    } else {
+        buf_stream_out = buf_write;
+    }
+    while (!available);
+    if (interruptIN) {
+        while (!writeIN);
+    }
+    while (!SOF_handler);
+    return true;
+}
+
+
+bool USBAudio::write(uint8_t * buf) {
+    writeIN = false;
+    SOF_handler = false;
+    if (interruptIN) {
+        USBDevice::writeNB(EP3IN, buf, PACKET_SIZE_ISO_OUT, PACKET_SIZE_ISO_OUT);
+    } else {
+        buf_stream_out = buf;
+    }
+    while (!SOF_handler);
+    if (interruptIN) {
+        while (!writeIN);
+    }
+    return true;
+}
+
+
+float USBAudio::getVolume() {
+    return (mute) ? 0.0 : volume;
+}
+
+
+bool USBAudio::EP3_OUT_callback() {
+    uint32_t size = 0;
+    interruptOUT = true;
+    if (buf_stream_in != NULL) {
+        readEP(EP3OUT, (uint8_t *)buf_stream_in, &size, PACKET_SIZE_ISO_IN);
+        available = true;
+        buf_stream_in = NULL;
+    }
+    readStart(EP3OUT, PACKET_SIZE_ISO_IN);
+    return false;
+}
+
+
+bool USBAudio::EP3_IN_callback() {
+    interruptIN = true;
+    writeIN = true;
+    return true;
+}
+
+
+
+// Called in ISR context on each start of frame
+void USBAudio::SOF(int frameNumber) {
+    uint32_t size = 0;
+
+    if (!interruptOUT) {
+        // read the isochronous endpoint
+        if (buf_stream_in != NULL) {
+            if (USBDevice::readEP_NB(EP3OUT, (uint8_t *)buf_stream_in, &size, PACKET_SIZE_ISO_IN)) {
+                if (size) {
+                    available = true;
+                    readStart(EP3OUT, PACKET_SIZE_ISO_IN);
+                    buf_stream_in = NULL;
+                }
+            }
+        }
+    }
+
+    if (!interruptIN) {
+        // write if needed
+        if (buf_stream_out != NULL) {
+            USBDevice::writeNB(EP3IN, (uint8_t *)buf_stream_out, PACKET_SIZE_ISO_OUT, PACKET_SIZE_ISO_OUT);
+            buf_stream_out = NULL;
+        }
+    }
+
+    SOF_handler = true;
+}
+
+
+// Called in ISR context
+// Set configuration. Return false if the configuration is not supported.
+bool USBAudio::USBCallback_setConfiguration(uint8_t configuration) {
+    if (configuration != DEFAULT_CONFIGURATION) {
+        return false;
+    }
+
+    // Configure isochronous endpoint
+    realiseEndpoint(EP3OUT, PACKET_SIZE_ISO_IN, ISOCHRONOUS);
+    realiseEndpoint(EP3IN, PACKET_SIZE_ISO_OUT, ISOCHRONOUS);
+
+    // activate readings on this endpoint
+    readStart(EP3OUT, PACKET_SIZE_ISO_IN);
+    return true;
+}
+
+
+// Called in ISR context
+// Set alternate setting. Return false if the alternate setting is not supported
+bool USBAudio::USBCallback_setInterface(uint16_t interface, uint8_t alternate) {
+    if (interface == 0 && alternate == 0) {
+        return true;
+    }
+    if (interface == 1 && (alternate == 0 || alternate == 1)) {
+        return true;
+    }
+    if (interface == 2 && (alternate == 0 || alternate == 1)) {
+        return true;
+    }
+    return false;
+}
+
+
+
+// Called in ISR context
+// Called by USBDevice on Endpoint0 request
+// This is used to handle extensions to standard requests and class specific requests.
+// Return true if class handles this request
+bool USBAudio::USBCallback_request() {
+    bool success = false;
+    CONTROL_TRANSFER * transfer = getTransferPtr();
+
+    // Process class-specific requests
+    if (transfer->setup.bmRequestType.Type == CLASS_TYPE) {
+
+        // Feature Unit: Interface = 0, ID = 2
+        if (transfer->setup.wIndex == 0x0200) {
+
+            // Master Channel
+            if ((transfer->setup.wValue & 0xff) == 0) {
+
+                switch (transfer->setup.wValue >> 8) {
+                    case MUTE_CONTROL:
+                        switch (transfer->setup.bRequest) {
+                            case REQUEST_GET_CUR:
+                                transfer->remaining = 1;
+                                transfer->ptr = &mute;
+                                transfer->direction = DEVICE_TO_HOST;
+                                success = true;
+                                break;
+
+                            case REQUEST_SET_CUR:
+                                transfer->remaining = 1;
+                                transfer->notify = true;
+                                transfer->direction = HOST_TO_DEVICE;
+                                success = true;
+                                break;
+                            default:
+                                break;
+                        }
+                        break;
+                    case VOLUME_CONTROL:
+                        switch (transfer->setup.bRequest) {
+                            case REQUEST_GET_CUR:
+                                transfer->remaining = 2;
+                                transfer->ptr = (uint8_t *)&volCur;
+                                transfer->direction = DEVICE_TO_HOST;
+                                success = true;
+                                break;
+                            case REQUEST_GET_MIN:
+                                transfer->remaining = 2;
+                                transfer->ptr = (uint8_t *)&volMin;
+                                transfer->direction = DEVICE_TO_HOST;
+                                success = true;
+                                break;
+                            case REQUEST_GET_MAX:
+                                transfer->remaining = 2;
+                                transfer->ptr = (uint8_t *)&volMax;
+                                transfer->direction = DEVICE_TO_HOST;
+                                success = true;
+                                break;
+                            case REQUEST_GET_RES:
+                                transfer->remaining = 2;
+                                transfer->ptr = (uint8_t *)&volRes;
+                                transfer->direction = DEVICE_TO_HOST;
+                                success = true;
+                                break;
+
+                            case REQUEST_SET_CUR:
+                                transfer->remaining = 2;
+                                transfer->notify = true;
+                                transfer->direction = HOST_TO_DEVICE;
+                                success = true;
+                                break;
+                            case REQUEST_SET_MIN:
+                                transfer->remaining = 2;
+                                transfer->notify = true;
+                                transfer->direction = HOST_TO_DEVICE;
+                                success = true;
+                                break;
+                            case REQUEST_SET_MAX:
+                                transfer->remaining = 2;
+                                transfer->notify = true;
+                                transfer->direction = HOST_TO_DEVICE;
+                                success = true;
+                                break;
+                            case REQUEST_SET_RES:
+                                transfer->remaining = 2;
+                                transfer->notify = true;
+                                transfer->direction = HOST_TO_DEVICE;
+                                success = true;
+                                break;
+                        }
+                        break;
+                    default:
+                        break;
+                }
+            }
+        }
+    }
+    return success;
+}
+
+
+// Called in ISR context when a data OUT stage has been performed
+void USBAudio::USBCallback_requestCompleted(uint8_t * buf, uint32_t length) {
+    if ((length == 1) || (length == 2)) {
+        uint16_t data = (length == 1) ? *buf : *((uint16_t *)buf);
+        CONTROL_TRANSFER * transfer = getTransferPtr();
+        switch (transfer->setup.wValue >> 8) {
+            case MUTE_CONTROL:
+                switch (transfer->setup.bRequest) {
+                    case REQUEST_SET_CUR:
+                        mute = data & 0xff;
+                        updateVol.call();
+                        break;
+                    default:
+                        break;
+                }
+                break;
+            case VOLUME_CONTROL:
+                switch (transfer->setup.bRequest) {
+                    case REQUEST_SET_CUR:
+                        volCur = data;
+                        volume = (float)volCur/(float)volMax;
+                        updateVol.call();
+                        break;
+                    default:
+                        break;
+                }
+                break;
+            default:
+                break;
+        }
+    }
+}
+
+
+
+#define TOTAL_DESCRIPTOR_LENGTH ((1 * CONFIGURATION_DESCRIPTOR_LENGTH) \
+                               + (5 * INTERFACE_DESCRIPTOR_LENGTH) \
+                               + (1 * CONTROL_INTERFACE_DESCRIPTOR_LENGTH + 1) \
+                               + (2 * INPUT_TERMINAL_DESCRIPTOR_LENGTH) \
+                               + (1 * FEATURE_UNIT_DESCRIPTOR_LENGTH) \
+                               + (2 * OUTPUT_TERMINAL_DESCRIPTOR_LENGTH) \
+                               + (2 * STREAMING_INTERFACE_DESCRIPTOR_LENGTH) \
+                               + (2 * FORMAT_TYPE_I_DESCRIPTOR_LENGTH) \
+                               + (2 * (ENDPOINT_DESCRIPTOR_LENGTH + 2)) \
+                               + (2 * STREAMING_ENDPOINT_DESCRIPTOR_LENGTH) )
+
+#define TOTAL_CONTROL_INTF_LENGTH    (CONTROL_INTERFACE_DESCRIPTOR_LENGTH + 1 + \
+                                      2*INPUT_TERMINAL_DESCRIPTOR_LENGTH     + \
+                                      FEATURE_UNIT_DESCRIPTOR_LENGTH    + \
+                                      2*OUTPUT_TERMINAL_DESCRIPTOR_LENGTH)
+
+uint8_t * USBAudio::configurationDesc() {
+    static uint8_t configDescriptor[] = {
+        // Configuration 1
+        CONFIGURATION_DESCRIPTOR_LENGTH,        // bLength
+        CONFIGURATION_DESCRIPTOR,               // bDescriptorType
+        LSB(TOTAL_DESCRIPTOR_LENGTH),           // wTotalLength (LSB)
+        MSB(TOTAL_DESCRIPTOR_LENGTH),           // wTotalLength (MSB)
+        0x03,                                   // bNumInterfaces
+        DEFAULT_CONFIGURATION,                  // bConfigurationValue
+        0x00,                                   // iConfiguration
+        0x80,                                   // bmAttributes
+        50,                                     // bMaxPower
+
+        // Interface 0, Alternate Setting 0, Audio Control
+        INTERFACE_DESCRIPTOR_LENGTH,            // bLength
+        INTERFACE_DESCRIPTOR,                   // bDescriptorType
+        0x00,                                   // bInterfaceNumber
+        0x00,                                   // bAlternateSetting
+        0x00,                                   // bNumEndpoints
+        AUDIO_CLASS,                            // bInterfaceClass
+        SUBCLASS_AUDIOCONTROL,                  // bInterfaceSubClass
+        0x00,                                   // bInterfaceProtocol
+        0x00,                                   // iInterface
+
+
+        // Audio Control Interface
+        CONTROL_INTERFACE_DESCRIPTOR_LENGTH + 1,// bLength
+        INTERFACE_DESCRIPTOR_TYPE,              // bDescriptorType
+        CONTROL_HEADER,                         // bDescriptorSubtype
+        LSB(0x0100),                            // bcdADC (LSB)
+        MSB(0x0100),                            // bcdADC (MSB)
+        LSB(TOTAL_CONTROL_INTF_LENGTH),         // wTotalLength
+        MSB(TOTAL_CONTROL_INTF_LENGTH),         // wTotalLength
+        0x02,                                   // bInCollection
+        0x01,                                   // baInterfaceNr
+        0x02,                                   // baInterfaceNr
+
+        // Audio Input Terminal (Speaker)
+        INPUT_TERMINAL_DESCRIPTOR_LENGTH,       // bLength
+        INTERFACE_DESCRIPTOR_TYPE,              // bDescriptorType
+        CONTROL_INPUT_TERMINAL,                 // bDescriptorSubtype
+        0x01,                                   // bTerminalID
+        LSB(TERMINAL_USB_STREAMING),            // wTerminalType
+        MSB(TERMINAL_USB_STREAMING),            // wTerminalType
+        0x00,                                   // bAssocTerminal
+        channel_nb_in,                          // bNrChannels
+        (uint8_t)(LSB(channel_config_in)),                 // wChannelConfig
+        (uint8_t)(MSB(channel_config_in)),                 // wChannelConfig
+        0x00,                                   // iChannelNames
+        0x00,                                   // iTerminal
+
+        // Audio Feature Unit (Speaker)
+        FEATURE_UNIT_DESCRIPTOR_LENGTH,         // bLength
+        INTERFACE_DESCRIPTOR_TYPE,              // bDescriptorType
+        CONTROL_FEATURE_UNIT,                   // bDescriptorSubtype
+        0x02,                                   // bUnitID
+        0x01,                                   // bSourceID
+        0x01,                                   // bControlSize
+        CONTROL_MUTE |
+        CONTROL_VOLUME,                         // bmaControls(0)
+        0x00,                                   // bmaControls(1)
+        0x00,                                   // iTerminal
+
+        // Audio Output Terminal (Speaker)
+        OUTPUT_TERMINAL_DESCRIPTOR_LENGTH,      // bLength
+        INTERFACE_DESCRIPTOR_TYPE,              // bDescriptorType
+        CONTROL_OUTPUT_TERMINAL,                // bDescriptorSubtype
+        0x03,                                   // bTerminalID
+        LSB(TERMINAL_SPEAKER),                  // wTerminalType
+        MSB(TERMINAL_SPEAKER),                  // wTerminalType
+        0x00,                                   // bAssocTerminal
+        0x02,                                   // bSourceID
+        0x00,                                   // iTerminal
+
+
+        // Audio Input Terminal (Microphone)
+        INPUT_TERMINAL_DESCRIPTOR_LENGTH,       // bLength
+        INTERFACE_DESCRIPTOR_TYPE,              // bDescriptorType
+        CONTROL_INPUT_TERMINAL,                 // bDescriptorSubtype
+        0x04,                                   // bTerminalID
+        LSB(TERMINAL_MICROPHONE),               // wTerminalType
+        MSB(TERMINAL_MICROPHONE),               // wTerminalType
+        0x00,                                   // bAssocTerminal
+        channel_nb_out,                         // bNrChannels
+        (uint8_t)(LSB(channel_config_out)),                // wChannelConfig
+        (uint8_t)(MSB(channel_config_out)),                // wChannelConfig
+        0x00,                                   // iChannelNames
+        0x00,                                   // iTerminal
+
+        // Audio Output Terminal (Microphone)
+        OUTPUT_TERMINAL_DESCRIPTOR_LENGTH,      // bLength
+        INTERFACE_DESCRIPTOR_TYPE,              // bDescriptorType
+        CONTROL_OUTPUT_TERMINAL,                // bDescriptorSubtype
+        0x05,                                   // bTerminalID
+        LSB(TERMINAL_USB_STREAMING),            // wTerminalType
+        MSB(TERMINAL_USB_STREAMING),            // wTerminalType
+        0x00,                                   // bAssocTerminal
+        0x04,                                   // bSourceID
+        0x00,                                   // iTerminal
+
+
+
+
+
+
+        // Interface 1, Alternate Setting 0, Audio Streaming - Zero Bandwith
+        INTERFACE_DESCRIPTOR_LENGTH,            // bLength
+        INTERFACE_DESCRIPTOR,                   // bDescriptorType
+        0x01,                                   // bInterfaceNumber
+        0x00,                                   // bAlternateSetting
+        0x00,                                   // bNumEndpoints
+        AUDIO_CLASS,                            // bInterfaceClass
+        SUBCLASS_AUDIOSTREAMING,                // bInterfaceSubClass
+        0x00,                                   // bInterfaceProtocol
+        0x00,                                   // iInterface
+
+        // Interface 1, Alternate Setting 1, Audio Streaming - Operational
+        INTERFACE_DESCRIPTOR_LENGTH,            // bLength
+        INTERFACE_DESCRIPTOR,                   // bDescriptorType
+        0x01,                                   // bInterfaceNumber
+        0x01,                                   // bAlternateSetting
+        0x01,                                   // bNumEndpoints
+        AUDIO_CLASS,                            // bInterfaceClass
+        SUBCLASS_AUDIOSTREAMING,                // bInterfaceSubClass
+        0x00,                                   // bInterfaceProtocol
+        0x00,                                   // iInterface
+
+        // Audio Streaming Interface
+        STREAMING_INTERFACE_DESCRIPTOR_LENGTH,  // bLength
+        INTERFACE_DESCRIPTOR_TYPE,              // bDescriptorType
+        STREAMING_GENERAL,                      // bDescriptorSubtype
+        0x01,                                   // bTerminalLink
+        0x00,                                   // bDelay
+        LSB(FORMAT_PCM),                        // wFormatTag
+        MSB(FORMAT_PCM),                        // wFormatTag
+
+        // Audio Type I Format
+        FORMAT_TYPE_I_DESCRIPTOR_LENGTH,        // bLength
+        INTERFACE_DESCRIPTOR_TYPE,              // bDescriptorType
+        STREAMING_FORMAT_TYPE,                  // bDescriptorSubtype
+        FORMAT_TYPE_I,                          // bFormatType
+        channel_nb_in,                          // bNrChannels
+        0x02,                                   // bSubFrameSize
+        16,                                     // bBitResolution
+        0x01,                                   // bSamFreqType
+        (uint8_t)(LSB(FREQ_IN)),                           // tSamFreq
+        (uint8_t)((FREQ_IN >> 8) & 0xff),                  // tSamFreq
+        (uint8_t)((FREQ_IN >> 16) & 0xff),                 // tSamFreq
+
+        // Endpoint - Standard Descriptor
+        ENDPOINT_DESCRIPTOR_LENGTH + 2,         // bLength
+        ENDPOINT_DESCRIPTOR,                    // bDescriptorType
+        PHY_TO_DESC(EPISO_OUT),                 // bEndpointAddress
+        E_ISOCHRONOUS,                          // bmAttributes
+        (uint8_t)(LSB(PACKET_SIZE_ISO_IN)),                   // wMaxPacketSize
+        (uint8_t)(MSB(PACKET_SIZE_ISO_IN)),                   // wMaxPacketSize
+        0x01,                                   // bInterval
+        0x00,                                   // bRefresh
+        0x00,                                   // bSynchAddress
+
+        // Endpoint - Audio Streaming
+        STREAMING_ENDPOINT_DESCRIPTOR_LENGTH,   // bLength
+        ENDPOINT_DESCRIPTOR_TYPE,               // bDescriptorType
+        ENDPOINT_GENERAL,                       // bDescriptor
+        0x00,                                   // bmAttributes
+        0x00,                                   // bLockDelayUnits
+        LSB(0x0000),                            // wLockDelay
+        MSB(0x0000),                            // wLockDelay
+
+
+
+
+
+
+
+        // Interface 1, Alternate Setting 0, Audio Streaming - Zero Bandwith
+        INTERFACE_DESCRIPTOR_LENGTH,            // bLength
+        INTERFACE_DESCRIPTOR,                   // bDescriptorType
+        0x02,                                   // bInterfaceNumber
+        0x00,                                   // bAlternateSetting
+        0x00,                                   // bNumEndpoints
+        AUDIO_CLASS,                            // bInterfaceClass
+        SUBCLASS_AUDIOSTREAMING,                // bInterfaceSubClass
+        0x00,                                   // bInterfaceProtocol
+        0x00,                                   // iInterface
+
+        // Interface 1, Alternate Setting 1, Audio Streaming - Operational
+        INTERFACE_DESCRIPTOR_LENGTH,            // bLength
+        INTERFACE_DESCRIPTOR,                   // bDescriptorType
+        0x02,                                   // bInterfaceNumber
+        0x01,                                   // bAlternateSetting
+        0x01,                                   // bNumEndpoints
+        AUDIO_CLASS,                            // bInterfaceClass
+        SUBCLASS_AUDIOSTREAMING,                // bInterfaceSubClass
+        0x00,                                   // bInterfaceProtocol
+        0x00,                                   // iInterface
+
+        // Audio Streaming Interface
+        STREAMING_INTERFACE_DESCRIPTOR_LENGTH,  // bLength
+        INTERFACE_DESCRIPTOR_TYPE,              // bDescriptorType
+        SUBCLASS_AUDIOCONTROL,                  // bDescriptorSubtype
+        0x05,                                   // bTerminalLink (output terminal microphone)
+        0x01,                                   // bDelay
+        0x01,                                   // wFormatTag
+        0x00,                                   // wFormatTag
+
+        // Audio Type I Format
+        FORMAT_TYPE_I_DESCRIPTOR_LENGTH,        // bLength
+        INTERFACE_DESCRIPTOR_TYPE,              // bDescriptorType
+        SUBCLASS_AUDIOSTREAMING,                // bDescriptorSubtype
+        FORMAT_TYPE_I,                          // bFormatType
+        channel_nb_out,                         // bNrChannels
+        0x02,                                   // bSubFrameSize
+        0x10,                                   // bBitResolution
+        0x01,                                   // bSamFreqType
+        (uint8_t)(LSB(FREQ_OUT)),                          // tSamFreq
+        (uint8_t)((FREQ_OUT >> 8) & 0xff),                 // tSamFreq
+        (uint8_t)((FREQ_OUT >> 16) & 0xff),                // tSamFreq
+
+        // Endpoint - Standard Descriptor
+        ENDPOINT_DESCRIPTOR_LENGTH + 2,         // bLength
+        ENDPOINT_DESCRIPTOR,                    // bDescriptorType
+        PHY_TO_DESC(EPISO_IN),                  // bEndpointAddress
+        E_ISOCHRONOUS,                          // bmAttributes
+        (uint8_t)(LSB(PACKET_SIZE_ISO_OUT)),                   // wMaxPacketSize
+        (uint8_t)(MSB(PACKET_SIZE_ISO_OUT)),                   // wMaxPacketSize
+        0x01,                                   // bInterval
+        0x00,                                   // bRefresh
+        0x00,                                   // bSynchAddress
+
+        // Endpoint - Audio Streaming
+        STREAMING_ENDPOINT_DESCRIPTOR_LENGTH,   // bLength
+        ENDPOINT_DESCRIPTOR_TYPE,               // bDescriptorType
+        ENDPOINT_GENERAL,                       // bDescriptor
+        0x00,                                   // bmAttributes
+        0x00,                                   // bLockDelayUnits
+        LSB(0x0000),                            // wLockDelay
+        MSB(0x0000),                            // wLockDelay
+
+        // Terminator
+        0                                       // bLength
+    };
+    return configDescriptor;
+}
+
+uint8_t * USBAudio::stringIinterfaceDesc() {
+    static uint8_t stringIinterfaceDescriptor[] = {
+        0x0c,                           //bLength
+        STRING_DESCRIPTOR,              //bDescriptorType 0x03
+        'A',0,'u',0,'d',0,'i',0,'o',0   //bString iInterface - Audio
+    };
+    return stringIinterfaceDescriptor;
+}
+
+uint8_t * USBAudio::stringIproductDesc() {
+    static uint8_t stringIproductDescriptor[] = {
+        0x16,                                                       //bLength
+        STRING_DESCRIPTOR,                                          //bDescriptorType 0x03
+        'M',0,'b',0,'e',0,'d',0,' ',0,'A',0,'u',0,'d',0,'i',0,'o',0 //bString iProduct - Mbed Audio
+    };
+    return stringIproductDescriptor;
+}