diff --git a/src/midi_UsbDefs.h b/src/midi_UsbDefs.h
new file mode 100644
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+++ b/src/midi_UsbDefs.h
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+/*!
+ *  @file       midi_UsbDefs.h
+ *  Project     Arduino MIDI Library
+ *  @brief      MIDI Library for the Arduino - Definitions
+ *  @version    4.2
+ *  @author     Francois Best
+ *  @date       24/02/11
+ *  @license    MIT - Copyright (c) 2016 Francois Best
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include "midi_Namespace.h"
+
+BEGIN_MIDI_NAMESPACE
+
+struct CodeIndexNumbers
+{
+    enum
+    {
+        reserved                = 0x00,
+        misc                    = reserved,
+
+        cableEvent              = 0x01,
+        systemCommon2Bytes      = 0x02,
+        systemCommon3Bytes      = 0x03,
+
+        sysExStart              = 0x04,
+        sysExContinue           = sysExStart,
+
+        systemCommon1Byte       = 0x05,
+        sysExEnds1Byte          = systemCommon1Byte,
+
+        sysExEnds2Bytes         = 0x06,
+        sysExEnds3Bytes         = 0x07,
+        noteOff                 = 0x08,
+        noteOn                  = 0x09,
+        polyPressure            = 0x0A,
+        controlChange           = 0x0B,
+        programChange           = 0x0C,
+        channelPressure         = 0x0D,
+        pitchBend               = 0x0E,
+        singleByte              = 0x0F,
+    };
+
+    static inline byte getSize(byte inCodeIndexNumber)
+    {
+        switch (inCodeIndexNumber)
+        {
+            case noteOn:
+            case noteOff:
+            case controlChange:
+            case pitchBend:
+            case polyKeyPress:
+            case systemCommon3Bytes:
+            case sysExEnds3Bytes:
+                return 3;
+
+            case programChange:
+            case channelPressure:
+            case systemCommon2Bytes:
+            case sysExEnds2Bytes:
+                return 2;
+
+            case systemCommon1Byte:
+            case singleByte:
+                return 1;
+
+            default:
+                break;
+        }
+        return 0;
+    }
+};
+
+// -----------------------------------------------------------------------------
+
+struct UsbMidiEventPacket
+{
+    union
+    {
+        uint32_t    mRawData;
+        struct
+        {
+            byte mCableNumber:4;
+            byte mCodeIndexNumber:4;
+            byte mMidi[3];
+        };
+        byte     mDataArray[4];
+    };
+};
+
+END_MIDI_NAMESPACE