Extract interface numbers into enums.

77 files changed, 509 insertions, 212 deletions

diff --git a/Demos/Device/ClassDriver/AudioInput/AudioInput.c b/Demos/Device/ClassDriver/AudioInput/AudioInput.c
index 9eec39ca2..02bd1e45a 100644
--- a/Demos/Device/ClassDriver/AudioInput/AudioInput.c
+++ b/Demos/Device/ClassDriver/AudioInput/AudioInput.c
@@ -44,8 +44,8 @@ USB_ClassInfo_Audio_Device_t Microphone_Audio_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber   = 0,
-				.StreamingInterfaceNumber = 1,
+				.ControlInterfaceNumber   = INTERFACE_ID_AudioControl,
+				.StreamingInterfaceNumber = INTERFACE_ID_AudioStream,
 				.DataINEndpoint           =
 					{
 						.Address          = AUDIO_STREAM_EPADDR,
diff --git a/Demos/Device/ClassDriver/AudioInput/Descriptors.c b/Demos/Device/ClassDriver/AudioInput/Descriptors.c
index eb4c21c02..a48738735 100644
--- a/Demos/Device/ClassDriver/AudioInput/Descriptors.c
+++ b/Demos/Device/ClassDriver/AudioInput/Descriptors.c
@@ -90,7 +90,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 0,
+			.InterfaceNumber          = INTERFACE_ID_AudioControl,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 0,
@@ -150,7 +150,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 1,
+			.InterfaceNumber          = INTERFACE_ID_AudioStream,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 0,
@@ -166,7 +166,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 1,
+			.InterfaceNumber          = INTERFACE_ID_AudioStream,
 			.AlternateSetting         = 1,
 
 			.TotalEndpoints           = 1,
diff --git a/Demos/Device/ClassDriver/AudioInput/Descriptors.h b/Demos/Device/ClassDriver/AudioInput/Descriptors.h
index 1bb38ff65..fe099570f 100644
--- a/Demos/Device/ClassDriver/AudioInput/Descriptors.h
+++ b/Demos/Device/ClassDriver/AudioInput/Descriptors.h
@@ -75,15 +75,25 @@
 			USB_Audio_Descriptor_StreamEndpoint_Spc_t Audio_StreamEndpoint_SPC;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_AudioControl = 0, /**< Audio control interface descriptor ID */
+			INTERFACE_ID_AudioStream  = 1, /**< Audio stream interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/AudioOutput/AudioOutput.c b/Demos/Device/ClassDriver/AudioOutput/AudioOutput.c
index 81fd95b16..432f5e0fa 100644
--- a/Demos/Device/ClassDriver/AudioOutput/AudioOutput.c
+++ b/Demos/Device/ClassDriver/AudioOutput/AudioOutput.c
@@ -44,8 +44,8 @@ USB_ClassInfo_Audio_Device_t Speaker_Audio_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber   = 0,
-				.StreamingInterfaceNumber = 1,
+				.ControlInterfaceNumber   = INTERFACE_ID_AudioControl,
+				.StreamingInterfaceNumber = INTERFACE_ID_AudioStream,
 				.DataOUTEndpoint          =
 					{
 						.Address          = AUDIO_STREAM_EPADDR,
diff --git a/Demos/Device/ClassDriver/AudioOutput/Descriptors.c b/Demos/Device/ClassDriver/AudioOutput/Descriptors.c
index 4ced7a0eb..aec2c5f51 100644
--- a/Demos/Device/ClassDriver/AudioOutput/Descriptors.c
+++ b/Demos/Device/ClassDriver/AudioOutput/Descriptors.c
@@ -90,7 +90,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 0,
+			.InterfaceNumber          = INTERFACE_ID_AudioControl,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 0,
@@ -150,7 +150,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 1,
+			.InterfaceNumber          = INTERFACE_ID_AudioStream,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 0,
@@ -166,7 +166,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 1,
+			.InterfaceNumber          = INTERFACE_ID_AudioStream,
 			.AlternateSetting         = 1,
 
 			.TotalEndpoints           = 1,
diff --git a/Demos/Device/ClassDriver/AudioOutput/Descriptors.h b/Demos/Device/ClassDriver/AudioOutput/Descriptors.h
index 80f142683..cb67f02ec 100644
--- a/Demos/Device/ClassDriver/AudioOutput/Descriptors.h
+++ b/Demos/Device/ClassDriver/AudioOutput/Descriptors.h
@@ -75,15 +75,25 @@
 			USB_Audio_Descriptor_StreamEndpoint_Spc_t Audio_StreamEndpoint_SPC;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_AudioControl = 0, /**< Audio control interface descriptor ID */
+			INTERFACE_ID_AudioStream  = 1, /**< Audio stream interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/DualVirtualSerial/Descriptors.c b/Demos/Device/ClassDriver/DualVirtualSerial/Descriptors.c
index d0992de4b..245231852 100644
--- a/Demos/Device/ClassDriver/DualVirtualSerial/Descriptors.c
+++ b/Demos/Device/ClassDriver/DualVirtualSerial/Descriptors.c
@@ -105,7 +105,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_CDC1_CCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
@@ -156,7 +156,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 1,
+			.InterfaceNumber        = INTERFACE_ID_CDC1_DCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
@@ -206,7 +206,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 2,
+			.InterfaceNumber        = INTERFACE_ID_CDC2_CCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
@@ -257,7 +257,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 3,
+			.InterfaceNumber        = INTERFACE_ID_CDC2_DCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/ClassDriver/DualVirtualSerial/Descriptors.h b/Demos/Device/ClassDriver/DualVirtualSerial/Descriptors.h
index 1105ab7b3..98170269a 100644
--- a/Demos/Device/ClassDriver/DualVirtualSerial/Descriptors.h
+++ b/Demos/Device/ClassDriver/DualVirtualSerial/Descriptors.h
@@ -102,15 +102,27 @@
 			USB_Descriptor_Endpoint_t                CDC2_DataInEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_CDC1_CCI = 0, /**< CDC1 CCI interface descriptor ID */
+			INTERFACE_ID_CDC1_DCI = 1, /**< CDC1 DCI interface descriptor ID */
+			INTERFACE_ID_CDC2_CCI = 2, /**< CDC2 CCI interface descriptor ID */
+			INTERFACE_ID_CDC2_DCI = 3, /**< CDC2 DCI interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/DualVirtualSerial/DualVirtualSerial.c b/Demos/Device/ClassDriver/DualVirtualSerial/DualVirtualSerial.c
index eaba6185a..070ebc791 100644
--- a/Demos/Device/ClassDriver/DualVirtualSerial/DualVirtualSerial.c
+++ b/Demos/Device/ClassDriver/DualVirtualSerial/DualVirtualSerial.c
@@ -45,7 +45,7 @@ USB_ClassInfo_CDC_Device_t VirtualSerial1_CDC_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber   = 0,
+				.ControlInterfaceNumber   = INTERFACE_ID_CDC1_CCI,
 				.DataINEndpoint           =
 					{
 						.Address          = CDC1_TX_EPADDR,
@@ -76,7 +76,7 @@ USB_ClassInfo_CDC_Device_t VirtualSerial2_CDC_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber   = 2,
+				.ControlInterfaceNumber   = INTERFACE_ID_CDC2_CCI,
 				.DataINEndpoint           =
 					{
 						.Address          = CDC2_TX_EPADDR,
diff --git a/Demos/Device/ClassDriver/GenericHID/Descriptors.c b/Demos/Device/ClassDriver/GenericHID/Descriptors.c
index 57c3502b9..b070d8640 100644
--- a/Demos/Device/ClassDriver/GenericHID/Descriptors.c
+++ b/Demos/Device/ClassDriver/GenericHID/Descriptors.c
@@ -108,7 +108,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_GenericHID,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
diff --git a/Demos/Device/ClassDriver/GenericHID/Descriptors.h b/Demos/Device/ClassDriver/GenericHID/Descriptors.h
index b598e9889..4500f2c10 100644
--- a/Demos/Device/ClassDriver/GenericHID/Descriptors.h
+++ b/Demos/Device/ClassDriver/GenericHID/Descriptors.h
@@ -55,18 +55,27 @@
 			// Generic HID Interface
 			USB_Descriptor_Interface_t            HID_Interface;
 			USB_HID_Descriptor_HID_t              HID_GenericHID;
-	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
+			USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_GenericHID = 0, /**< GenericHID interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Macros: */
diff --git a/Demos/Device/ClassDriver/GenericHID/GenericHID.c b/Demos/Device/ClassDriver/GenericHID/GenericHID.c
index 182aa5a58..8f5b86131 100644
--- a/Demos/Device/ClassDriver/GenericHID/GenericHID.c
+++ b/Demos/Device/ClassDriver/GenericHID/GenericHID.c
@@ -47,7 +47,7 @@ USB_ClassInfo_HID_Device_t Generic_HID_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber              = 0,
+				.InterfaceNumber              = INTERFACE_ID_GenericHID,
 				.ReportINEndpoint             =
 					{
 						.Address              = GENERIC_IN_EPADDR,
diff --git a/Demos/Device/ClassDriver/Joystick/Descriptors.c b/Demos/Device/ClassDriver/Joystick/Descriptors.c
index 8a6ef2052..2d416528b 100644
--- a/Demos/Device/ClassDriver/Joystick/Descriptors.c
+++ b/Demos/Device/ClassDriver/Joystick/Descriptors.c
@@ -108,7 +108,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_Joystick,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
diff --git a/Demos/Device/ClassDriver/Joystick/Descriptors.h b/Demos/Device/ClassDriver/Joystick/Descriptors.h
index 89c0584d9..839cd28eb 100644
--- a/Demos/Device/ClassDriver/Joystick/Descriptors.h
+++ b/Demos/Device/ClassDriver/Joystick/Descriptors.h
@@ -56,15 +56,24 @@
 	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_Joystick = 0, /**< Joystick interface desciptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Macros: */
diff --git a/Demos/Device/ClassDriver/Joystick/Joystick.c b/Demos/Device/ClassDriver/Joystick/Joystick.c
index 809c41060..bbe85584a 100644
--- a/Demos/Device/ClassDriver/Joystick/Joystick.c
+++ b/Demos/Device/ClassDriver/Joystick/Joystick.c
@@ -47,7 +47,7 @@ USB_ClassInfo_HID_Device_t Joystick_HID_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber              = 0,
+				.InterfaceNumber              = INTERFACE_ID_Joystick,
 				.ReportINEndpoint             =
 					{
 						.Address              = JOYSTICK_EPADDR,
diff --git a/Demos/Device/ClassDriver/Keyboard/Descriptors.c b/Demos/Device/ClassDriver/Keyboard/Descriptors.c
index f40e3b932..4340ec657 100644
--- a/Demos/Device/ClassDriver/Keyboard/Descriptors.c
+++ b/Demos/Device/ClassDriver/Keyboard/Descriptors.c
@@ -104,7 +104,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_Keyboard,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
diff --git a/Demos/Device/ClassDriver/Keyboard/Descriptors.h b/Demos/Device/ClassDriver/Keyboard/Descriptors.h
index abaf9c62a..ce029bb75 100644
--- a/Demos/Device/ClassDriver/Keyboard/Descriptors.h
+++ b/Demos/Device/ClassDriver/Keyboard/Descriptors.h
@@ -56,15 +56,24 @@
 	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_Keyboard = 0, /**< Keyboard interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Macros: */
diff --git a/Demos/Device/ClassDriver/Keyboard/Keyboard.c b/Demos/Device/ClassDriver/Keyboard/Keyboard.c
index b3cc67e1e..68e3fbe1b 100644
--- a/Demos/Device/ClassDriver/Keyboard/Keyboard.c
+++ b/Demos/Device/ClassDriver/Keyboard/Keyboard.c
@@ -47,7 +47,7 @@ USB_ClassInfo_HID_Device_t Keyboard_HID_Interface =
  	{
 		.Config =
 			{
-				.InterfaceNumber              = 0,
+				.InterfaceNumber              = INTERFACE_ID_Keyboard,
 				.ReportINEndpoint             =
 					{
 						.Address              = KEYBOARD_EPADDR,
diff --git a/Demos/Device/ClassDriver/KeyboardMouse/Descriptors.c b/Demos/Device/ClassDriver/KeyboardMouse/Descriptors.c
index c3b2e2c7b..0d350c764 100644
--- a/Demos/Device/ClassDriver/KeyboardMouse/Descriptors.c
+++ b/Demos/Device/ClassDriver/KeyboardMouse/Descriptors.c
@@ -120,7 +120,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_Keyboard,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
@@ -157,7 +157,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x01,
+			.InterfaceNumber        = INTERFACE_ID_Mouse,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
@@ -269,28 +269,30 @@ uint16_t CALLBACK_USB_GetDescriptor(const uint16_t wValue,
 
 			break;
 		case HID_DTYPE_HID:
-			if (!(wIndex))
+			switch (wIndex)
 			{
-				Address = &ConfigurationDescriptor.HID1_KeyboardHID;
-				Size    = sizeof(USB_HID_Descriptor_HID_t);
-			}
-			else
-			{
-				Address = &ConfigurationDescriptor.HID2_MouseHID;
-				Size    = sizeof(USB_HID_Descriptor_HID_t);
+				case INTERFACE_ID_Keyboard:
+					Address = &ConfigurationDescriptor.HID1_KeyboardHID;
+					Size    = sizeof(USB_HID_Descriptor_HID_t);
+					break;
+				case INTERFACE_ID_Mouse:
+					Address = &ConfigurationDescriptor.HID2_MouseHID;
+					Size    = sizeof(USB_HID_Descriptor_HID_t);
+					break;
 			}
 
 			break;
 		case HID_DTYPE_Report:
-			if (!(wIndex))
+			switch (wIndex)
 			{
-				Address = &KeyboardReport;
-				Size    = sizeof(KeyboardReport);
-			}
-			else
-			{
-				Address = &MouseReport;
-				Size    = sizeof(MouseReport);
+				case INTERFACE_ID_Keyboard:
+					Address = &KeyboardReport;
+					Size    = sizeof(KeyboardReport);
+					break;
+				case INTERFACE_ID_Mouse:
+					Address = &MouseReport;
+					Size    = sizeof(MouseReport);
+					break;
 			}
 
 			break;
diff --git a/Demos/Device/ClassDriver/KeyboardMouse/Descriptors.h b/Demos/Device/ClassDriver/KeyboardMouse/Descriptors.h
index 27120eb34..1a45f74bd 100644
--- a/Demos/Device/ClassDriver/KeyboardMouse/Descriptors.h
+++ b/Demos/Device/ClassDriver/KeyboardMouse/Descriptors.h
@@ -61,15 +61,25 @@
 			USB_Descriptor_Endpoint_t             HID2_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_Keyboard = 0, /**< Keyboard interface descriptor ID */
+			INTERFACE_ID_Mouse    = 1, /**< Mouse interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Macros: */
diff --git a/Demos/Device/ClassDriver/KeyboardMouse/KeyboardMouse.c b/Demos/Device/ClassDriver/KeyboardMouse/KeyboardMouse.c
index f663f1683..789fc215d 100644
--- a/Demos/Device/ClassDriver/KeyboardMouse/KeyboardMouse.c
+++ b/Demos/Device/ClassDriver/KeyboardMouse/KeyboardMouse.c
@@ -51,7 +51,7 @@ USB_ClassInfo_HID_Device_t Keyboard_HID_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber              = 0,
+				.InterfaceNumber              = INTERFACE_ID_Keyboard,
 				.ReportINEndpoint             =
 					{
 						.Address              = KEYBOARD_IN_EPADDR,
@@ -72,7 +72,7 @@ USB_ClassInfo_HID_Device_t Mouse_HID_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber              = 1,
+				.InterfaceNumber              = INTERFACE_ID_Mouse,
 				.ReportINEndpoint             =
 					{
 						.Address              = MOUSE_IN_EPADDR,
diff --git a/Demos/Device/ClassDriver/KeyboardMouseMultiReport/Descriptors.c b/Demos/Device/ClassDriver/KeyboardMouseMultiReport/Descriptors.c
index a36147321..477cad0a4 100644
--- a/Demos/Device/ClassDriver/KeyboardMouseMultiReport/Descriptors.c
+++ b/Demos/Device/ClassDriver/KeyboardMouseMultiReport/Descriptors.c
@@ -167,7 +167,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_KeyboardAndMouse,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
diff --git a/Demos/Device/ClassDriver/KeyboardMouseMultiReport/Descriptors.h b/Demos/Device/ClassDriver/KeyboardMouseMultiReport/Descriptors.h
index a47d18577..f5d68be69 100644
--- a/Demos/Device/ClassDriver/KeyboardMouseMultiReport/Descriptors.h
+++ b/Demos/Device/ClassDriver/KeyboardMouseMultiReport/Descriptors.h
@@ -56,15 +56,24 @@
 			USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_KeyboardAndMouse = 0, /**< Combined keyboard and mouse interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Macros: */
diff --git a/Demos/Device/ClassDriver/KeyboardMouseMultiReport/KeyboardMouseMultiReport.c b/Demos/Device/ClassDriver/KeyboardMouseMultiReport/KeyboardMouseMultiReport.c
index f15d134ff..0ec878894 100644
--- a/Demos/Device/ClassDriver/KeyboardMouseMultiReport/KeyboardMouseMultiReport.c
+++ b/Demos/Device/ClassDriver/KeyboardMouseMultiReport/KeyboardMouseMultiReport.c
@@ -47,7 +47,7 @@ USB_ClassInfo_HID_Device_t Device_HID_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber              = 0,
+				.InterfaceNumber              = INTERFACE_ID_KeyboardAndMouse,
 				.ReportINEndpoint             =
 					{
 						.Address              = HID_IN_EPADDR,
diff --git a/Demos/Device/ClassDriver/MIDI/Descriptors.c b/Demos/Device/ClassDriver/MIDI/Descriptors.c
index 5413f27f5..746bcc484 100644
--- a/Demos/Device/ClassDriver/MIDI/Descriptors.c
+++ b/Demos/Device/ClassDriver/MIDI/Descriptors.c
@@ -90,7 +90,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 0,
+			.InterfaceNumber          = INTERFACE_ID_MidiAudioControl,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 0,
@@ -118,7 +118,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 1,
+			.InterfaceNumber          = INTERFACE_ID_MidiAudioStreaming,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 2,
diff --git a/Demos/Device/ClassDriver/MIDI/Descriptors.h b/Demos/Device/ClassDriver/MIDI/Descriptors.h
index 92c6c38d9..d6f230a8d 100644
--- a/Demos/Device/ClassDriver/MIDI/Descriptors.h
+++ b/Demos/Device/ClassDriver/MIDI/Descriptors.h
@@ -77,15 +77,25 @@
 			USB_MIDI_Descriptor_Jack_Endpoint_t       MIDI_Out_Jack_Endpoint_SPC;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_MidiAudioControl   = 0, /**< MIDI audio control interface descriptor ID */
+			INTERFACE_ID_MidiAudioStreaming = 1, /**< MIDI audio streaming interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/MIDI/MIDI.c b/Demos/Device/ClassDriver/MIDI/MIDI.c
index bec442883..79a831762 100644
--- a/Demos/Device/ClassDriver/MIDI/MIDI.c
+++ b/Demos/Device/ClassDriver/MIDI/MIDI.c
@@ -44,7 +44,7 @@ USB_ClassInfo_MIDI_Device_t Keyboard_MIDI_Interface =
 	{
 		.Config =
 			{
-				.StreamingInterfaceNumber = 1,
+				.StreamingInterfaceNumber = INTERFACE_ID_MidiAudioStreaming,
 				.DataINEndpoint           =
 					{
 						.Address          = MIDI_STREAM_IN_EPADDR,
diff --git a/Demos/Device/ClassDriver/MassStorage/Descriptors.c b/Demos/Device/ClassDriver/MassStorage/Descriptors.c
index d069bcece..2be052b07 100644
--- a/Demos/Device/ClassDriver/MassStorage/Descriptors.c
+++ b/Demos/Device/ClassDriver/MassStorage/Descriptors.c
@@ -91,7 +91,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_MassStorage,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/ClassDriver/MassStorage/Descriptors.h b/Demos/Device/ClassDriver/MassStorage/Descriptors.h
index 3b9a96c8a..674bd2960 100644
--- a/Demos/Device/ClassDriver/MassStorage/Descriptors.h
+++ b/Demos/Device/ClassDriver/MassStorage/Descriptors.h
@@ -68,15 +68,24 @@
 			USB_Descriptor_Endpoint_t             MS_DataOutEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_MassStorage = 0, /**< Mass storage interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/MassStorage/MassStorage.c b/Demos/Device/ClassDriver/MassStorage/MassStorage.c
index 82f02b918..32b4c2634 100644
--- a/Demos/Device/ClassDriver/MassStorage/MassStorage.c
+++ b/Demos/Device/ClassDriver/MassStorage/MassStorage.c
@@ -44,7 +44,7 @@ USB_ClassInfo_MS_Device_t Disk_MS_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber           = 0,
+				.InterfaceNumber           = INTERFACE_ID_MassStorage,
 				.DataINEndpoint            =
 					{
 						.Address           = MASS_STORAGE_IN_EPADDR,
diff --git a/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.c b/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.c
index 2209d5144..5749b365f 100644
--- a/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.c
+++ b/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.c
@@ -106,7 +106,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_MassStorage,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
@@ -142,7 +142,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 1,
+			.InterfaceNumber        = INTERFACE_ID_Keyboard,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
diff --git a/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.h b/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.h
index 2b70e11b4..606e47d91 100644
--- a/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.h
+++ b/Demos/Device/ClassDriver/MassStorageKeyboard/Descriptors.h
@@ -80,15 +80,25 @@
 	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_MassStorage = 0, /**< Mass storage interface descriptor ID */
+			INTERFACE_ID_Keyboard    = 1, /**< Keyboard interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/MassStorageKeyboard/MassStorageKeyboard.c b/Demos/Device/ClassDriver/MassStorageKeyboard/MassStorageKeyboard.c
index 2ed3f411b..8ed0d3b64 100644
--- a/Demos/Device/ClassDriver/MassStorageKeyboard/MassStorageKeyboard.c
+++ b/Demos/Device/ClassDriver/MassStorageKeyboard/MassStorageKeyboard.c
@@ -45,7 +45,7 @@ USB_ClassInfo_MS_Device_t Disk_MS_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber           = 0,
+				.InterfaceNumber           = INTERFACE_ID_MassStorage,
 				.DataINEndpoint            =
 					{
 						.Address           = MASS_STORAGE_IN_EPADDR,
@@ -73,7 +73,7 @@ USB_ClassInfo_HID_Device_t Keyboard_HID_Interface =
  	{
 		.Config =
 			{
-				.InterfaceNumber              = 1,
+				.InterfaceNumber              = INTERFACE_ID_Keyboard,
 				.ReportINEndpoint             =
 					{
 						.Address              = KEYBOARD_EPADDR,
diff --git a/Demos/Device/ClassDriver/Mouse/Descriptors.c b/Demos/Device/ClassDriver/Mouse/Descriptors.c
index c21a8cc65..09278a790 100644
--- a/Demos/Device/ClassDriver/Mouse/Descriptors.c
+++ b/Demos/Device/ClassDriver/Mouse/Descriptors.c
@@ -109,7 +109,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_Mouse,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
diff --git a/Demos/Device/ClassDriver/Mouse/Descriptors.h b/Demos/Device/ClassDriver/Mouse/Descriptors.h
index a5380a11a..3b637e21f 100644
--- a/Demos/Device/ClassDriver/Mouse/Descriptors.h
+++ b/Demos/Device/ClassDriver/Mouse/Descriptors.h
@@ -60,18 +60,27 @@
 			// Mouse HID Interface
 			USB_Descriptor_Interface_t            HID_Interface;
 			USB_HID_Descriptor_HID_t              HID_MouseHID;
-	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
+			USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_Mouse = 0, /**< Mouse interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/Mouse/Mouse.c b/Demos/Device/ClassDriver/Mouse/Mouse.c
index 8432b65a9..1e8f7ab93 100644
--- a/Demos/Device/ClassDriver/Mouse/Mouse.c
+++ b/Demos/Device/ClassDriver/Mouse/Mouse.c
@@ -47,7 +47,7 @@ USB_ClassInfo_HID_Device_t Mouse_HID_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber              = 0,
+				.InterfaceNumber              = INTERFACE_ID_Mouse,
 				.ReportINEndpoint             =
 					{
 						.Address              = MOUSE_EPADDR,
diff --git a/Demos/Device/ClassDriver/RNDISEthernet/Descriptors.c b/Demos/Device/ClassDriver/RNDISEthernet/Descriptors.c
index ca70633be..7474e5499 100644
--- a/Demos/Device/ClassDriver/RNDISEthernet/Descriptors.c
+++ b/Demos/Device/ClassDriver/RNDISEthernet/Descriptors.c
@@ -90,7 +90,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_CDC_CCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
@@ -141,7 +141,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 1,
+			.InterfaceNumber        = INTERFACE_ID_CDC_DCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/ClassDriver/RNDISEthernet/Descriptors.h b/Demos/Device/ClassDriver/RNDISEthernet/Descriptors.h
index be5015725..c782a5ea7 100644
--- a/Demos/Device/ClassDriver/RNDISEthernet/Descriptors.h
+++ b/Demos/Device/ClassDriver/RNDISEthernet/Descriptors.h
@@ -81,15 +81,25 @@
 			USB_Descriptor_Endpoint_t             RNDIS_DataInEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_CDC_CCI = 0, /**< CDC CCI interface descriptor ID */
+			INTERFACE_ID_CDC_DCI = 1, /**< CDC DCI interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/RNDISEthernet/RNDISEthernet.c b/Demos/Device/ClassDriver/RNDISEthernet/RNDISEthernet.c
index 54d551142..e38dfec26 100644
--- a/Demos/Device/ClassDriver/RNDISEthernet/RNDISEthernet.c
+++ b/Demos/Device/ClassDriver/RNDISEthernet/RNDISEthernet.c
@@ -44,7 +44,7 @@ USB_ClassInfo_RNDIS_Device_t Ethernet_RNDIS_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber         = 0,
+				.ControlInterfaceNumber         = INTERFACE_ID_CDC_CCI,
 				.DataINEndpoint                 =
 					{
 						.Address                = CDC_TX_EPADDR,
diff --git a/Demos/Device/ClassDriver/VirtualSerial/Descriptors.c b/Demos/Device/ClassDriver/VirtualSerial/Descriptors.c
index 9432562cc..33f63371d 100644
--- a/Demos/Device/ClassDriver/VirtualSerial/Descriptors.c
+++ b/Demos/Device/ClassDriver/VirtualSerial/Descriptors.c
@@ -91,7 +91,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_CDC_CCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
@@ -142,7 +142,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 1,
+			.InterfaceNumber        = INTERFACE_ID_CDC_DCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/ClassDriver/VirtualSerial/Descriptors.h b/Demos/Device/ClassDriver/VirtualSerial/Descriptors.h
index e2d09b218..20caec05c 100644
--- a/Demos/Device/ClassDriver/VirtualSerial/Descriptors.h
+++ b/Demos/Device/ClassDriver/VirtualSerial/Descriptors.h
@@ -79,15 +79,25 @@
 			USB_Descriptor_Endpoint_t                CDC_DataInEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_CDC_CCI = 0, /**< CDC CCI interface descriptor ID */
+			INTERFACE_ID_CDC_DCI = 1, /**< CDC DCI interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/VirtualSerial/VirtualSerial.c b/Demos/Device/ClassDriver/VirtualSerial/VirtualSerial.c
index 0079acbfa..56b248d3c 100644
--- a/Demos/Device/ClassDriver/VirtualSerial/VirtualSerial.c
+++ b/Demos/Device/ClassDriver/VirtualSerial/VirtualSerial.c
@@ -44,7 +44,7 @@ USB_ClassInfo_CDC_Device_t VirtualSerial_CDC_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber   = 0,
+				.ControlInterfaceNumber   = INTERFACE_ID_CDC_CCI,
 				.DataINEndpoint           =
 					{
 						.Address          = CDC_TX_EPADDR,
diff --git a/Demos/Device/ClassDriver/VirtualSerialMassStorage/Descriptors.c b/Demos/Device/ClassDriver/VirtualSerialMassStorage/Descriptors.c
index e41a91a18..b8a07f4c2 100644
--- a/Demos/Device/ClassDriver/VirtualSerialMassStorage/Descriptors.c
+++ b/Demos/Device/ClassDriver/VirtualSerialMassStorage/Descriptors.c
@@ -105,7 +105,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_CDC_CCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
@@ -156,7 +156,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 1,
+			.InterfaceNumber        = INTERFACE_ID_CDC_DCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
@@ -192,7 +192,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 2,
+			.InterfaceNumber        = INTERFACE_ID_MassStorage,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/ClassDriver/VirtualSerialMassStorage/Descriptors.h b/Demos/Device/ClassDriver/VirtualSerialMassStorage/Descriptors.h
index 25d31bff8..ac6e4fa8e 100644
--- a/Demos/Device/ClassDriver/VirtualSerialMassStorage/Descriptors.h
+++ b/Demos/Device/ClassDriver/VirtualSerialMassStorage/Descriptors.h
@@ -96,15 +96,26 @@
 			USB_Descriptor_Endpoint_t                MS_DataOutEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_CDC_CCI     = 0, /**< CDC CCI interface descriptor ID */
+			INTERFACE_ID_CDC_DCI     = 1, /**< CDC DCI interface descriptor ID */
+			INTERFACE_ID_MassStorage = 2, /**< Mass storage interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/VirtualSerialMassStorage/VirtualSerialMassStorage.c b/Demos/Device/ClassDriver/VirtualSerialMassStorage/VirtualSerialMassStorage.c
index 03f422b45..6dc1ab662 100644
--- a/Demos/Device/ClassDriver/VirtualSerialMassStorage/VirtualSerialMassStorage.c
+++ b/Demos/Device/ClassDriver/VirtualSerialMassStorage/VirtualSerialMassStorage.c
@@ -44,7 +44,7 @@ USB_ClassInfo_CDC_Device_t VirtualSerial_CDC_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber         = 0,
+				.ControlInterfaceNumber         = INTERFACE_ID_CDC_CCI,
 				.DataINEndpoint                 =
 					{
 						.Address                = CDC_TX_EPADDR,
@@ -74,7 +74,7 @@ USB_ClassInfo_MS_Device_t Disk_MS_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber                = 2,
+				.InterfaceNumber                = INTERFACE_ID_MassStorage,
 				.DataINEndpoint                 =
 					{
 						.Address                = MASS_STORAGE_IN_EPADDR,
diff --git a/Demos/Device/ClassDriver/VirtualSerialMouse/Descriptors.c b/Demos/Device/ClassDriver/VirtualSerialMouse/Descriptors.c
index 42c77dde8..43c849b79 100644
--- a/Demos/Device/ClassDriver/VirtualSerialMouse/Descriptors.c
+++ b/Demos/Device/ClassDriver/VirtualSerialMouse/Descriptors.c
@@ -124,7 +124,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_CDC_CCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
@@ -175,7 +175,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 1,
+			.InterfaceNumber        = INTERFACE_ID_CDC_DCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
@@ -211,7 +211,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 2,
+			.InterfaceNumber        = INTERFACE_ID_Mouse,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
diff --git a/Demos/Device/ClassDriver/VirtualSerialMouse/Descriptors.h b/Demos/Device/ClassDriver/VirtualSerialMouse/Descriptors.h
index 1bce49627..7ac638bd6 100644
--- a/Demos/Device/ClassDriver/VirtualSerialMouse/Descriptors.h
+++ b/Demos/Device/ClassDriver/VirtualSerialMouse/Descriptors.h
@@ -91,15 +91,26 @@
 	        USB_Descriptor_Endpoint_t                HID_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_CDC_CCI = 0, /**< CDC CCI interface descriptor ID */
+			INTERFACE_ID_CDC_DCI = 1, /**< CDC DCI interface descriptor ID */
+			INTERFACE_ID_Mouse   = 2, /**< Mouse interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/ClassDriver/VirtualSerialMouse/VirtualSerialMouse.c b/Demos/Device/ClassDriver/VirtualSerialMouse/VirtualSerialMouse.c
index 73f9e3875..d4aba4851 100644
--- a/Demos/Device/ClassDriver/VirtualSerialMouse/VirtualSerialMouse.c
+++ b/Demos/Device/ClassDriver/VirtualSerialMouse/VirtualSerialMouse.c
@@ -44,7 +44,7 @@ USB_ClassInfo_CDC_Device_t VirtualSerial_CDC_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber         = 0,
+				.ControlInterfaceNumber         = INTERFACE_ID_CDC_CCI,
 				.DataINEndpoint                 =
 					{
 						.Address                = CDC_TX_EPADDR,
@@ -77,7 +77,7 @@ USB_ClassInfo_HID_Device_t Mouse_HID_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber                = 2,
+				.InterfaceNumber                = INTERFACE_ID_Mouse,
 				.ReportINEndpoint               =
 					{
 						.Address                = MOUSE_EPADDR,
diff --git a/Demos/Device/Incomplete/TestAndMeasurement/Descriptors.c b/Demos/Device/Incomplete/TestAndMeasurement/Descriptors.c
index 8bf92371d..6b27db8b3 100644
--- a/Demos/Device/Incomplete/TestAndMeasurement/Descriptors.c
+++ b/Demos/Device/Incomplete/TestAndMeasurement/Descriptors.c
@@ -92,7 +92,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_TestAndMeasurement,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 3,
diff --git a/Demos/Device/Incomplete/TestAndMeasurement/Descriptors.h b/Demos/Device/Incomplete/TestAndMeasurement/Descriptors.h
index 9beb3d272..07464486d 100644
--- a/Demos/Device/Incomplete/TestAndMeasurement/Descriptors.h
+++ b/Demos/Device/Incomplete/TestAndMeasurement/Descriptors.h
@@ -74,15 +74,24 @@
 			USB_Descriptor_Endpoint_t             TM_NotificationEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_TestAndMeasurement = 0, /**< Test and measurement interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/LowLevel/AudioInput/Descriptors.c b/Demos/Device/LowLevel/AudioInput/Descriptors.c
index b3490d005..444f16046 100644
--- a/Demos/Device/LowLevel/AudioInput/Descriptors.c
+++ b/Demos/Device/LowLevel/AudioInput/Descriptors.c
@@ -90,7 +90,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 0,
+			.InterfaceNumber          = INTERFACE_ID_AudioControl,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 0,
@@ -150,7 +150,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 1,
+			.InterfaceNumber          = INTERFACE_ID_AudioStream,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 0,
@@ -166,7 +166,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 1,
+			.InterfaceNumber          = INTERFACE_ID_AudioStream,
 			.AlternateSetting         = 1,
 
 			.TotalEndpoints           = 1,
diff --git a/Demos/Device/LowLevel/AudioInput/Descriptors.h b/Demos/Device/LowLevel/AudioInput/Descriptors.h
index a3d3ec3ef..7dbb9aa22 100644
--- a/Demos/Device/LowLevel/AudioInput/Descriptors.h
+++ b/Demos/Device/LowLevel/AudioInput/Descriptors.h
@@ -75,15 +75,25 @@
 			USB_Audio_Descriptor_StreamEndpoint_Spc_t Audio_StreamEndpoint_SPC;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_AudioControl = 0, /**< Audio control interface descriptor ID */
+			INTERFACE_ID_AudioStream  = 1, /**< Audio stream interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/LowLevel/AudioOutput/Descriptors.c b/Demos/Device/LowLevel/AudioOutput/Descriptors.c
index 43f717549..7879c3463 100644
--- a/Demos/Device/LowLevel/AudioOutput/Descriptors.c
+++ b/Demos/Device/LowLevel/AudioOutput/Descriptors.c
@@ -90,7 +90,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 0,
+			.InterfaceNumber          = INTERFACE_ID_AudioControl,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 0,
@@ -150,7 +150,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 1,
+			.InterfaceNumber          = INTERFACE_ID_AudioStream,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 0,
@@ -166,7 +166,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 1,
+			.InterfaceNumber          = INTERFACE_ID_AudioStream,
 			.AlternateSetting         = 1,
 
 			.TotalEndpoints           = 1,
diff --git a/Demos/Device/LowLevel/AudioOutput/Descriptors.h b/Demos/Device/LowLevel/AudioOutput/Descriptors.h
index b8ae901d7..07d1becbd 100644
--- a/Demos/Device/LowLevel/AudioOutput/Descriptors.h
+++ b/Demos/Device/LowLevel/AudioOutput/Descriptors.h
@@ -75,15 +75,25 @@
 			USB_Audio_Descriptor_StreamEndpoint_Spc_t Audio_StreamEndpoint_SPC;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_AudioControl = 0, /**< Audio control interface descriptor ID */
+			INTERFACE_ID_AudioStream  = 1, /**< Audio stream interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/LowLevel/DualVirtualSerial/Descriptors.c b/Demos/Device/LowLevel/DualVirtualSerial/Descriptors.c
index d0992de4b..245231852 100644
--- a/Demos/Device/LowLevel/DualVirtualSerial/Descriptors.c
+++ b/Demos/Device/LowLevel/DualVirtualSerial/Descriptors.c
@@ -105,7 +105,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_CDC1_CCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
@@ -156,7 +156,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 1,
+			.InterfaceNumber        = INTERFACE_ID_CDC1_DCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
@@ -206,7 +206,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 2,
+			.InterfaceNumber        = INTERFACE_ID_CDC2_CCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
@@ -257,7 +257,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 3,
+			.InterfaceNumber        = INTERFACE_ID_CDC2_DCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/LowLevel/DualVirtualSerial/Descriptors.h b/Demos/Device/LowLevel/DualVirtualSerial/Descriptors.h
index a5a87dc3d..dc19cfe34 100644
--- a/Demos/Device/LowLevel/DualVirtualSerial/Descriptors.h
+++ b/Demos/Device/LowLevel/DualVirtualSerial/Descriptors.h
@@ -102,15 +102,27 @@
 			USB_Descriptor_Endpoint_t                CDC2_DataInEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_CDC1_CCI = 0, /**< CDC1 CCI interface descriptor ID */
+			INTERFACE_ID_CDC1_DCI = 1, /**< CDC1 DCI interface descriptor ID */
+			INTERFACE_ID_CDC2_CCI = 2, /**< CDC2 CCI interface descriptor ID */
+			INTERFACE_ID_CDC2_DCI = 3, /**< CDC2 DCI interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/LowLevel/GenericHID/Descriptors.c b/Demos/Device/LowLevel/GenericHID/Descriptors.c
index bcbb386ce..2e7536001 100644
--- a/Demos/Device/LowLevel/GenericHID/Descriptors.c
+++ b/Demos/Device/LowLevel/GenericHID/Descriptors.c
@@ -116,7 +116,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_GenericHID,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/LowLevel/GenericHID/Descriptors.h b/Demos/Device/LowLevel/GenericHID/Descriptors.h
index 884233445..c37c68b13 100644
--- a/Demos/Device/LowLevel/GenericHID/Descriptors.h
+++ b/Demos/Device/LowLevel/GenericHID/Descriptors.h
@@ -55,19 +55,28 @@
 			// Generic HID Interface
 			USB_Descriptor_Interface_t            HID_Interface;
 			USB_HID_Descriptor_HID_t              HID_GenericHID;
-	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
-	        USB_Descriptor_Endpoint_t             HID_ReportOUTEndpoint;
+			USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
+			USB_Descriptor_Endpoint_t             HID_ReportOUTEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_GenericHID = 0, /**< GenericHID interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Macros: */
diff --git a/Demos/Device/LowLevel/Joystick/Descriptors.c b/Demos/Device/LowLevel/Joystick/Descriptors.c
index 376238708..2f9eb0099 100644
--- a/Demos/Device/LowLevel/Joystick/Descriptors.c
+++ b/Demos/Device/LowLevel/Joystick/Descriptors.c
@@ -128,7 +128,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_Joystick,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
diff --git a/Demos/Device/LowLevel/Joystick/Descriptors.h b/Demos/Device/LowLevel/Joystick/Descriptors.h
index f06b3cae3..2600e0cac 100644
--- a/Demos/Device/LowLevel/Joystick/Descriptors.h
+++ b/Demos/Device/LowLevel/Joystick/Descriptors.h
@@ -53,18 +53,27 @@
 			// Joystick HID Interface
 			USB_Descriptor_Interface_t            HID_Interface;
 			USB_HID_Descriptor_HID_t              HID_JoystickHID;
-	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
+			USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_Joystick = 0, /**< Joystick interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Macros: */
diff --git a/Demos/Device/LowLevel/Keyboard/Descriptors.c b/Demos/Device/LowLevel/Keyboard/Descriptors.c
index e3da4b6a9..6a644d80c 100644
--- a/Demos/Device/LowLevel/Keyboard/Descriptors.c
+++ b/Demos/Device/LowLevel/Keyboard/Descriptors.c
@@ -133,7 +133,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_Keyboard,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/LowLevel/Keyboard/Descriptors.h b/Demos/Device/LowLevel/Keyboard/Descriptors.h
index f9d54243a..dcd757233 100644
--- a/Demos/Device/LowLevel/Keyboard/Descriptors.h
+++ b/Demos/Device/LowLevel/Keyboard/Descriptors.h
@@ -54,19 +54,28 @@
 			// Keyboard HID Interface
 			USB_Descriptor_Interface_t            HID_Interface;
 			USB_HID_Descriptor_HID_t              HID_KeyboardHID;
-	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
-	        USB_Descriptor_Endpoint_t             HID_ReportOUTEndpoint;
+			USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
+			USB_Descriptor_Endpoint_t             HID_ReportOUTEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_Keyboard = 0, /**< Keyboard interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Macros: */
diff --git a/Demos/Device/LowLevel/KeyboardMouse/Descriptors.c b/Demos/Device/LowLevel/KeyboardMouse/Descriptors.c
index d45cd593f..4a339f415 100644
--- a/Demos/Device/LowLevel/KeyboardMouse/Descriptors.c
+++ b/Demos/Device/LowLevel/KeyboardMouse/Descriptors.c
@@ -168,7 +168,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_Keyboard,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 2,
@@ -215,7 +215,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x01,
+			.InterfaceNumber        = INTERFACE_ID_Mouse,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
@@ -327,27 +327,29 @@ uint16_t CALLBACK_USB_GetDescriptor(const uint16_t wValue,
 
 			break;
 		case HID_DTYPE_HID:
-			if (!(wIndex))
+			switch (wIndex)
 			{
-				Address = &ConfigurationDescriptor.HID1_KeyboardHID;
-				Size    = sizeof(USB_HID_Descriptor_HID_t);
-			}
-			else
-			{
-				Address = &ConfigurationDescriptor.HID2_MouseHID;
-				Size    = sizeof(USB_HID_Descriptor_HID_t);
+				case (INTERFACE_ID_Keyboard):
+					Address = &ConfigurationDescriptor.HID1_KeyboardHID;
+					Size    = sizeof(USB_HID_Descriptor_HID_t);
+					break;
+				case (INTERFACE_ID_Mouse):
+					Address = &ConfigurationDescriptor.HID2_MouseHID;
+					Size    = sizeof(USB_HID_Descriptor_HID_t);
+					break;
 			}
 			break;
 		case HID_DTYPE_Report:
-			if (!(wIndex))
+			switch (wIndex)
 			{
-				Address = &KeyboardReport;
-				Size    = sizeof(KeyboardReport);
-			}
-			else
-			{
-				Address = &MouseReport;
-				Size    = sizeof(MouseReport);
+				case INTERFACE_ID_Keyboard:
+					Address = &KeyboardReport;
+					Size    = sizeof(KeyboardReport);
+					break;
+				case INTERFACE_ID_Mouse:
+					Address = &MouseReport;
+					Size    = sizeof(MouseReport);
+					break;
 			}
 
 			break;
diff --git a/Demos/Device/LowLevel/KeyboardMouse/Descriptors.h b/Demos/Device/LowLevel/KeyboardMouse/Descriptors.h
index 6d2543ac2..99f423e1b 100644
--- a/Demos/Device/LowLevel/KeyboardMouse/Descriptors.h
+++ b/Demos/Device/LowLevel/KeyboardMouse/Descriptors.h
@@ -63,15 +63,25 @@
 			USB_Descriptor_Endpoint_t             HID2_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_Keyboard = 0, /**< Keyboard interface descriptor ID */
+			INTERFACE_ID_Mouse    = 1, /**< Mouse interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Macros: */
diff --git a/Demos/Device/LowLevel/MIDI/Descriptors.c b/Demos/Device/LowLevel/MIDI/Descriptors.c
index 5413f27f5..220d37dff 100644
--- a/Demos/Device/LowLevel/MIDI/Descriptors.c
+++ b/Demos/Device/LowLevel/MIDI/Descriptors.c
@@ -90,7 +90,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 0,
+			.InterfaceNumber          = INTERFACE_ID_AudioControl,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 0,
@@ -118,7 +118,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                   = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber          = 1,
+			.InterfaceNumber          = INTERFACE_ID_AudioStream,
 			.AlternateSetting         = 0,
 
 			.TotalEndpoints           = 2,
diff --git a/Demos/Device/LowLevel/MIDI/Descriptors.h b/Demos/Device/LowLevel/MIDI/Descriptors.h
index 1572b1cbc..649b2acb6 100644
--- a/Demos/Device/LowLevel/MIDI/Descriptors.h
+++ b/Demos/Device/LowLevel/MIDI/Descriptors.h
@@ -77,15 +77,25 @@
 			USB_MIDI_Descriptor_Jack_Endpoint_t       MIDI_Out_Jack_Endpoint_SPC;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_AudioControl = 0, /**< Audio control interface descriptor ID */
+			INTERFACE_ID_AudioStream  = 1, /**< Audio stream interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/LowLevel/MassStorage/Descriptors.c b/Demos/Device/LowLevel/MassStorage/Descriptors.c
index d069bcece..2be052b07 100644
--- a/Demos/Device/LowLevel/MassStorage/Descriptors.c
+++ b/Demos/Device/LowLevel/MassStorage/Descriptors.c
@@ -91,7 +91,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_MassStorage,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/LowLevel/MassStorage/Descriptors.h b/Demos/Device/LowLevel/MassStorage/Descriptors.h
index dc6748f85..7c3196b93 100644
--- a/Demos/Device/LowLevel/MassStorage/Descriptors.h
+++ b/Demos/Device/LowLevel/MassStorage/Descriptors.h
@@ -68,15 +68,24 @@
 			USB_Descriptor_Endpoint_t             MS_DataOutEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_MassStorage = 0, /**< Mass storage interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/LowLevel/Mouse/Descriptors.c b/Demos/Device/LowLevel/Mouse/Descriptors.c
index 99780a44d..23e8d7f44 100644
--- a/Demos/Device/LowLevel/Mouse/Descriptors.c
+++ b/Demos/Device/LowLevel/Mouse/Descriptors.c
@@ -128,7 +128,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_Mouse,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
diff --git a/Demos/Device/LowLevel/Mouse/Descriptors.h b/Demos/Device/LowLevel/Mouse/Descriptors.h
index a5380a11a..3b637e21f 100644
--- a/Demos/Device/LowLevel/Mouse/Descriptors.h
+++ b/Demos/Device/LowLevel/Mouse/Descriptors.h
@@ -60,18 +60,27 @@
 			// Mouse HID Interface
 			USB_Descriptor_Interface_t            HID_Interface;
 			USB_HID_Descriptor_HID_t              HID_MouseHID;
-	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
+			USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_Mouse = 0, /**< Mouse interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/LowLevel/RNDISEthernet/Descriptors.c b/Demos/Device/LowLevel/RNDISEthernet/Descriptors.c
index ca70633be..7474e5499 100644
--- a/Demos/Device/LowLevel/RNDISEthernet/Descriptors.c
+++ b/Demos/Device/LowLevel/RNDISEthernet/Descriptors.c
@@ -90,7 +90,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_CDC_CCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
@@ -141,7 +141,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 1,
+			.InterfaceNumber        = INTERFACE_ID_CDC_DCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/LowLevel/RNDISEthernet/Descriptors.h b/Demos/Device/LowLevel/RNDISEthernet/Descriptors.h
index 763bc0c7c..9db67965f 100644
--- a/Demos/Device/LowLevel/RNDISEthernet/Descriptors.h
+++ b/Demos/Device/LowLevel/RNDISEthernet/Descriptors.h
@@ -81,15 +81,25 @@
 			USB_Descriptor_Endpoint_t             RNDIS_DataInEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_CDC_CCI = 0, /**< CDC CCI interface descriptor ID */
+			INTERFACE_ID_CDC_DCI = 1, /**< CDC DCI interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/Device/LowLevel/VirtualSerial/Descriptors.c b/Demos/Device/LowLevel/VirtualSerial/Descriptors.c
index 9432562cc..33f63371d 100644
--- a/Demos/Device/LowLevel/VirtualSerial/Descriptors.c
+++ b/Demos/Device/LowLevel/VirtualSerial/Descriptors.c
@@ -91,7 +91,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_CDC_CCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
@@ -142,7 +142,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 1,
+			.InterfaceNumber        = INTERFACE_ID_CDC_DCI,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Demos/Device/LowLevel/VirtualSerial/Descriptors.h b/Demos/Device/LowLevel/VirtualSerial/Descriptors.h
index a704614a6..8ece697fd 100644
--- a/Demos/Device/LowLevel/VirtualSerial/Descriptors.h
+++ b/Demos/Device/LowLevel/VirtualSerial/Descriptors.h
@@ -79,15 +79,25 @@
 			USB_Descriptor_Endpoint_t                CDC_DataInEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_CDC_CCI = 0, /**< CDC CCI interface descriptor ID */
+			INTERFACE_ID_CDC_DCI = 1, /**< CDC DCI interface descriptor ID */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Demos/DualRole/ClassDriver/MouseHostDevice/Descriptors.c b/Demos/DualRole/ClassDriver/MouseHostDevice/Descriptors.c
index 6b714eb7d..13c6cbcc7 100644
--- a/Demos/DualRole/ClassDriver/MouseHostDevice/Descriptors.c
+++ b/Demos/DualRole/ClassDriver/MouseHostDevice/Descriptors.c
@@ -109,7 +109,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_Mouse,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
diff --git a/Demos/DualRole/ClassDriver/MouseHostDevice/Descriptors.h b/Demos/DualRole/ClassDriver/MouseHostDevice/Descriptors.h
index eca1e7981..a19b61267 100644
--- a/Demos/DualRole/ClassDriver/MouseHostDevice/Descriptors.h
+++ b/Demos/DualRole/ClassDriver/MouseHostDevice/Descriptors.h
@@ -53,18 +53,27 @@
 			// Mouse HID Interface
 			USB_Descriptor_Interface_t            HID_Interface;
 			USB_HID_Descriptor_HID_t              HID_MouseHID;
-	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
+			USB_Descriptor_Endpoint_t             HID_ReportINEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface descriptor IDs within the device. Each interface descriptor
+		 *  should have a unique ID index associated with it, which can be used to refer to the
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_Mouse = 0, /**< Mouse interface descriptor ID (must be zero) */
+		};
+
 		/** Enum for the device string descriptor IDs within the device. Each string descriptor should
 		 *  have a unique ID index associated with it, which can be used to refer to the string from
 		 *  other descriptors.
 		 */
 		enum StringDescriptors_t
 		{
-		    STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    STRING_ID_Product       = 2, /**< Product string ID */
+			STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Macros: */
diff --git a/Demos/DualRole/ClassDriver/MouseHostDevice/DeviceFunctions.c b/Demos/DualRole/ClassDriver/MouseHostDevice/DeviceFunctions.c
index ef9280ce8..2bbeb2dee 100644
--- a/Demos/DualRole/ClassDriver/MouseHostDevice/DeviceFunctions.c
+++ b/Demos/DualRole/ClassDriver/MouseHostDevice/DeviceFunctions.c
@@ -47,7 +47,7 @@ USB_ClassInfo_HID_Device_t Mouse_HID_Device_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber            = 0,
+				.InterfaceNumber            = INTERFACE_ID_Mouse,
 				.ReportINEndpoint           =
 					{
 						.Address            = MOUSE_EPADDR,