diff --git a/Bootloaders/CDC/Descriptors.c b/Bootloaders/CDC/Descriptors.c
index bbf4e76210..2b85b01264 100644
--- a/Bootloaders/CDC/Descriptors.c
+++ b/Bootloaders/CDC/Descriptors.c
@@ -90,7 +90,7 @@ const USB_Descriptor_Configuration_t 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 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/Bootloaders/CDC/Descriptors.h b/Bootloaders/CDC/Descriptors.h
index 24d1a398ef..f35a4d1f8f 100644
--- a/Bootloaders/CDC/Descriptors.h
+++ b/Bootloaders/CDC/Descriptors.h
@@ -127,15 +127,25 @@
 			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/Bootloaders/DFU/BootloaderDFU.h b/Bootloaders/DFU/BootloaderDFU.h
index 3d6d906494..949f7e8a51 100644
--- a/Bootloaders/DFU/BootloaderDFU.h
+++ b/Bootloaders/DFU/BootloaderDFU.h
@@ -170,7 +170,7 @@
 			dfuMANIFEST                  = 7,
 			dfuMANIFEST_WAIT_RESET       = 8,
 			dfuUPLOAD_IDLE               = 9,
-			dfuERROR	                 = 10
+			dfuERROR                     = 10
 		};
 
 		/** DFU command status error codes. Refer to the DFU class specification for information on each error code. */
@@ -191,7 +191,7 @@
 			errUSBR                      = 12,
 			errPOR                       = 13,
 			errUNKNOWN                   = 14,
-			errSTALLEDPKT	             = 15
+			errSTALLEDPKT                = 15
 		};
 
 	/* Function Prototypes: */
diff --git a/Bootloaders/DFU/Descriptors.c b/Bootloaders/DFU/Descriptors.c
index 5901dad128..9cd74cfd20 100644
--- a/Bootloaders/DFU/Descriptors.c
+++ b/Bootloaders/DFU/Descriptors.c
@@ -90,7 +90,7 @@ const USB_Descriptor_Configuration_t ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_DFU,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 0,
diff --git a/Bootloaders/DFU/Descriptors.h b/Bootloaders/DFU/Descriptors.h
index c33e388c04..8bd46793ef 100644
--- a/Bootloaders/DFU/Descriptors.h
+++ b/Bootloaders/DFU/Descriptors.h
@@ -164,15 +164,24 @@
 			USB_Descriptor_DFU_Functional_t       DFU_Functional;
 		} 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_DFU = 0, /**< DFU 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/Bootloaders/HID/Descriptors.c b/Bootloaders/HID/Descriptors.c
index ac27b760b8..6754d81d4a 100644
--- a/Bootloaders/HID/Descriptors.c
+++ b/Bootloaders/HID/Descriptors.c
@@ -110,7 +110,7 @@ const USB_Descriptor_Configuration_t ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_Printer,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
diff --git a/Bootloaders/HID/Descriptors.h b/Bootloaders/HID/Descriptors.h
index 4ef30ed8f6..c10b51678e 100644
--- a/Bootloaders/HID/Descriptors.h
+++ b/Bootloaders/HID/Descriptors.h
@@ -51,9 +51,18 @@
 			// Generic HID Interface
 			USB_Descriptor_Interface_t            HID_Interface;
 			USB_HID_Descriptor_HID_t              HID_VendorHID;
-	        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_Printer = 0, /**< Printer interface descriptor ID */
+		};
+
 	/* Macros: */
 		/** Endpoint address of the HID data IN endpoint. */
 		#define HID_IN_EPADDR                (ENDPOINT_DIR_IN | 1)
diff --git a/Bootloaders/MassStorage/BootloaderMassStorage.c b/Bootloaders/MassStorage/BootloaderMassStorage.c
index 1b6eda4387..9d15a81aff 100644
--- a/Bootloaders/MassStorage/BootloaderMassStorage.c
+++ b/Bootloaders/MassStorage/BootloaderMassStorage.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/Bootloaders/MassStorage/Descriptors.c b/Bootloaders/MassStorage/Descriptors.c
index 7ae0a7da9e..1186ea0794 100644
--- a/Bootloaders/MassStorage/Descriptors.c
+++ b/Bootloaders/MassStorage/Descriptors.c
@@ -91,7 +91,7 @@ const USB_Descriptor_Configuration_t ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_MassStorage,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Bootloaders/MassStorage/Descriptors.h b/Bootloaders/MassStorage/Descriptors.h
index 2e97c6d8a2..ea89cb27b6 100644
--- a/Bootloaders/MassStorage/Descriptors.h
+++ b/Bootloaders/MassStorage/Descriptors.h
@@ -68,6 +68,16 @@
 			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 */
+		};
+
 	/* Function Prototypes: */
 		uint16_t CALLBACK_USB_GetDescriptor(const uint16_t wValue,
 		                                    const uint8_t wIndex,
diff --git a/Bootloaders/Printer/BootloaderPrinter.c b/Bootloaders/Printer/BootloaderPrinter.c
index 1e60cdd6d5..3fec7217d4 100644
--- a/Bootloaders/Printer/BootloaderPrinter.c
+++ b/Bootloaders/Printer/BootloaderPrinter.c
@@ -43,7 +43,7 @@ USB_ClassInfo_PRNT_Device_t TextOnly_Printer_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber          = 0,
+				.InterfaceNumber          = INTERFACE_ID_Printer,
 				.DataINEndpoint           =
 					{
 						.Address          = PRINTER_IN_EPADDR,
diff --git a/Bootloaders/Printer/Descriptors.c b/Bootloaders/Printer/Descriptors.c
index 0fbb3ae7e4..5329afc864 100644
--- a/Bootloaders/Printer/Descriptors.c
+++ b/Bootloaders/Printer/Descriptors.c
@@ -91,7 +91,7 @@ const USB_Descriptor_Configuration_t ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_Printer,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Bootloaders/Printer/Descriptors.h b/Bootloaders/Printer/Descriptors.h
index fba326a935..d5c9b71ee2 100644
--- a/Bootloaders/Printer/Descriptors.h
+++ b/Bootloaders/Printer/Descriptors.h
@@ -66,15 +66,24 @@
 			USB_Descriptor_Endpoint_t             Printer_DataOutEndpoint;
 		} USB_Descriptor_Configuration_t;
 
+		/** Enum for the device interface 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
+		 *  interface from other descriptors.
+		 */
+		enum InterfaceDescriptors_t
+		{
+			INTERFACE_ID_Printer      = 0, /**< Printer 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/AudioInput/AudioInput.c b/Demos/Device/ClassDriver/AudioInput/AudioInput.c
index 9eec39ca25..02bd1e45a7 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 eb4c21c020..a487387352 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 1bb38ff65e..fe099570fe 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 81fd95b169..432f5e0fa2 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 4ced7a0eb5..aec2c5f517 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 80f1426839..cb67f02ec1 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 d0992de4bc..2452318523 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 1105ab7b33..98170269af 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 eaba6185ab..070ebc7919 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 57c3502b9f..b070d86404 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 b598e9889c..4500f2c101 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 182aa5a586..8f5b861319 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 8a6ef2052a..2d416528bb 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 89c0584d9a..839cd28eb1 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 809c410608..bbe85584a5 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 f40e3b932c..4340ec657c 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 abaf9c62a3..ce029bb75c 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 b3cc67e1e6..68e3fbe1bf 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 c3b2e2c7b4..0d350c7641 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 27120eb34d..1a45f74bd7 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 f663f1683d..789fc215d6 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 a361473216..477cad0a41 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 a47d18577f..f5d68be69d 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 f15d134ffc..0ec8788941 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 5413f27f56..746bcc4845 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 92c6c38d96..d6f230a8de 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 bec442883f..79a8317627 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 d069bcece4..2be052b070 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 3b9a96c8aa..674bd29600 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 82f02b918e..32b4c2634c 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 2209d5144b..5749b365f5 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 2b70e11b42..606e47d916 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 2ed3f411b4..8ed0d3b647 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 c21a8cc654..09278a7907 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 a5380a11a6..3b637e21fc 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 8432b65a92..1e8f7ab93f 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 ca70633be3..7474e54993 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 be50157259..c782a5ea76 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 54d5511428..e38dfec267 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 9432562cc7..33f63371d9 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 e2d09b2181..20caec05c9 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 0079acbfaa..56b248d3c9 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 e41a91a189..b8a07f4c22 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 25d31bff85..ac6e4fa8e5 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 03f422b45c..6dc1ab6628 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 42c77dde82..43c849b79f 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 1bce496274..7ac638bd6e 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 73f9e38759..d4aba48512 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 8bf92371de..6b27db8b35 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 9beb3d272d..07464486d8 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 b3490d005b..444f16046a 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 a3d3ec3ef2..7dbb9aa220 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 43f717549e..7879c34637 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 b8ae901d76..07d1becbdc 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 d0992de4bc..2452318523 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 a5a87dc3df..dc19cfe346 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 bcbb386cef..2e75360013 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 884233445c..c37c68b135 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 3762387087..2f9eb00996 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 f06b3cae3d..2600e0cac1 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 e3da4b6a9d..6a644d80cd 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 f9d54243a2..dcd757233b 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 d45cd593f9..4a339f4155 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 6d2543ac23..99f423e1bf 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 5413f27f56..220d37dff7 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 1572b1cbcc..649b2acb6a 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 d069bcece4..2be052b070 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 dc6748f855..7c3196b933 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 99780a44d4..23e8d7f445 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 a5380a11a6..3b637e21fc 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 ca70633be3..7474e54993 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 763bc0c7cf..9db67965ff 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 9432562cc7..33f63371d9 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 a704614a6b..8ece697fde 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 6b714eb7d1..13c6cbcc73 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 eca1e7981a..a19b612671 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 ef9280ce8e..2bbeb2dee8 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,
diff --git a/Projects/AVRISP-MKII/AVRISPDescriptors.c b/Projects/AVRISP-MKII/AVRISPDescriptors.c
index cb19051f44..c185cb9f4c 100644
--- a/Projects/AVRISP-MKII/AVRISPDescriptors.c
+++ b/Projects/AVRISP-MKII/AVRISPDescriptors.c
@@ -101,7 +101,7 @@ AVRISP_USB_Descriptor_Configuration_t AVRISP_ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_AVRISP,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 2,
diff --git a/Projects/AVRISP-MKII/AVRISPDescriptors.h b/Projects/AVRISP-MKII/AVRISPDescriptors.h
index 2f1192384a..68bb103598 100644
--- a/Projects/AVRISP-MKII/AVRISPDescriptors.h
+++ b/Projects/AVRISP-MKII/AVRISPDescriptors.h
@@ -86,16 +86,25 @@
 			USB_Descriptor_Endpoint_t                AVRISP_DataOutEndpoint;
 		} AVRISP_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_AVRISP = 0, /**< AVRISP 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 AVRISP_StringDescriptors_t
 		{
-		    AVRISP_STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    AVRISP_STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    AVRISP_STRING_ID_Product       = 2, /**< Product string ID */
-		    AVRISP_STRING_ID_Serial        = 3, /**< Serial number string ID */
+			AVRISP_STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			AVRISP_STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			AVRISP_STRING_ID_Product      = 2, /**< Product string ID */
+			AVRISP_STRING_ID_Serial       = 3, /**< Serial number string ID */
 		};
 
 	/* External Variables: */
diff --git a/Projects/Benito/Benito.c b/Projects/Benito/Benito.c
index a89e6caf63..2ecee07119 100644
--- a/Projects/Benito/Benito.c
+++ b/Projects/Benito/Benito.c
@@ -62,7 +62,7 @@ USB_ClassInfo_CDC_Device_t VirtualSerial_CDC_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber   = 0,
+				.ControlInterfaceNumber   = INTERFACE_ID_CDC_CCI,
 				.DataINEndpoint           =
 					{
 						.Address          = CDC_TX_EPADDR,
diff --git a/Projects/Benito/Descriptors.c b/Projects/Benito/Descriptors.c
index ebb11cac5a..8bd0907d53 100644
--- a/Projects/Benito/Descriptors.c
+++ b/Projects/Benito/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/Projects/Benito/Descriptors.h b/Projects/Benito/Descriptors.h
index 12be7bf9c4..5c67e71742 100644
--- a/Projects/Benito/Descriptors.h
+++ b/Projects/Benito/Descriptors.h
@@ -81,15 +81,25 @@
 			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/Projects/LEDNotifier/Descriptors.c b/Projects/LEDNotifier/Descriptors.c
index 1875bba014..f228c69ef0 100644
--- a/Projects/LEDNotifier/Descriptors.c
+++ b/Projects/LEDNotifier/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/Projects/LEDNotifier/Descriptors.h b/Projects/LEDNotifier/Descriptors.h
index 363951c5b6..ed19d84f82 100644
--- a/Projects/LEDNotifier/Descriptors.h
+++ b/Projects/LEDNotifier/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/Projects/LEDNotifier/LEDNotifier.c b/Projects/LEDNotifier/LEDNotifier.c
index d6a8fdca30..e1d5dd97f7 100644
--- a/Projects/LEDNotifier/LEDNotifier.c
+++ b/Projects/LEDNotifier/LEDNotifier.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/Projects/MIDIToneGenerator/Descriptors.c b/Projects/MIDIToneGenerator/Descriptors.c
index 5413f27f56..220d37dff7 100644
--- a/Projects/MIDIToneGenerator/Descriptors.c
+++ b/Projects/MIDIToneGenerator/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/Projects/MIDIToneGenerator/Descriptors.h b/Projects/MIDIToneGenerator/Descriptors.h
index cb87891874..dab2fd5a68 100644
--- a/Projects/MIDIToneGenerator/Descriptors.h
+++ b/Projects/MIDIToneGenerator/Descriptors.h
@@ -79,15 +79,25 @@
 			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/Projects/MIDIToneGenerator/MIDIToneGenerator.c b/Projects/MIDIToneGenerator/MIDIToneGenerator.c
index 662c815bc7..ed2d334209 100644
--- a/Projects/MIDIToneGenerator/MIDIToneGenerator.c
+++ b/Projects/MIDIToneGenerator/MIDIToneGenerator.c
@@ -44,7 +44,7 @@ USB_ClassInfo_MIDI_Device_t Keyboard_MIDI_Interface =
 	{
 		.Config =
 			{
-				.StreamingInterfaceNumber = 1,
+				.StreamingInterfaceNumber = INTERFACE_ID_AudioStream,
 				.DataINEndpoint           =
 					{
 						.Address          = MIDI_STREAM_IN_EPADDR,
diff --git a/Projects/Magstripe/Descriptors.c b/Projects/Magstripe/Descriptors.c
index 680944092f..c707c1cf6f 100644
--- a/Projects/Magstripe/Descriptors.c
+++ b/Projects/Magstripe/Descriptors.c
@@ -105,7 +105,7 @@ 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/Projects/Magstripe/Descriptors.h b/Projects/Magstripe/Descriptors.h
index 0f4869fb79..46218fc2c5 100644
--- a/Projects/Magstripe/Descriptors.h
+++ b/Projects/Magstripe/Descriptors.h
@@ -56,18 +56,27 @@
 			// Keyboard HID Interface
 			USB_Descriptor_Interface_t            HID_Interface; /**< Keyboard interface descriptor */
 			USB_HID_Descriptor_HID_t              HID_KeyboardHID; /**< Keyboard HID descriptor */
-	        USB_Descriptor_Endpoint_t             HID_ReportINEndpoint; /**< Keyboard key report endpoint descriptor */
+			USB_Descriptor_Endpoint_t             HID_ReportINEndpoint; /**< Keyboard key report endpoint descriptor */
 		} 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/Projects/Magstripe/Magstripe.c b/Projects/Magstripe/Magstripe.c
index 8dba7370be..a0b6f1b01d 100644
--- a/Projects/Magstripe/Magstripe.c
+++ b/Projects/Magstripe/Magstripe.c
@@ -56,7 +56,7 @@ USB_ClassInfo_HID_Device_t Keyboard_HID_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber            = 0,
+				.InterfaceNumber            = INTERFACE_ID_Keyboard,
 				.ReportINEndpoint           =
 					{
 						.Address            = KEYBOARD_EPADDR,
diff --git a/Projects/MediaController/Descriptors.c b/Projects/MediaController/Descriptors.c
index 636bbb618c..353e5fe2f7 100644
--- a/Projects/MediaController/Descriptors.c
+++ b/Projects/MediaController/Descriptors.c
@@ -122,7 +122,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0x00,
+			.InterfaceNumber        = INTERFACE_ID_HID,
 			.AlternateSetting       = 0x00,
 
 			.TotalEndpoints         = 1,
diff --git a/Projects/MediaController/Descriptors.h b/Projects/MediaController/Descriptors.h
index 9f889641e6..827885de68 100644
--- a/Projects/MediaController/Descriptors.h
+++ b/Projects/MediaController/Descriptors.h
@@ -53,18 +53,27 @@
 			// Media Controller HID Interface
 			USB_Descriptor_Interface_t            HID_Interface;
 			USB_HID_Descriptor_HID_t              HID_MediaControlHID;
-	        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_HID = 0, /**< HID 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/Projects/MediaController/MediaController.c b/Projects/MediaController/MediaController.c
index d12a21aac2..bda252a55c 100644
--- a/Projects/MediaController/MediaController.c
+++ b/Projects/MediaController/MediaController.c
@@ -47,7 +47,7 @@ USB_ClassInfo_HID_Device_t MediaControl_HID_Interface =
  	{
 		.Config =
 			{
-				.InterfaceNumber              = 0,
+				.InterfaceNumber              = INTERFACE_ID_HID,
 				.ReportINEndpoint             =
 					{
 						.Address              = MEDIACONTROL_HID_EPADDR,
diff --git a/Projects/RelayBoard/Descriptors.c b/Projects/RelayBoard/Descriptors.c
index c6b2d8f563..646f7ca088 100644
--- a/Projects/RelayBoard/Descriptors.c
+++ b/Projects/RelayBoard/Descriptors.c
@@ -91,7 +91,7 @@ const USB_Descriptor_Configuration_t PROGMEM RelayBoard_ConfigurationDescriptor
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 0,
+			.InterfaceNumber        = INTERFACE_ID_RelayBoard,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 0,
diff --git a/Projects/RelayBoard/Descriptors.h b/Projects/RelayBoard/Descriptors.h
index 97ed225160..c2fc16efa3 100644
--- a/Projects/RelayBoard/Descriptors.h
+++ b/Projects/RelayBoard/Descriptors.h
@@ -54,16 +54,25 @@
 			USB_Descriptor_Interface_t            RelayBoardInterface;
 		} 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_RelayBoard = 0, /**< Relay board 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_Serial        = 3, /**< Serial number 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 */
+			STRING_ID_Serial       = 3, /**< Serial number string ID */
 		};
 
 	/* Function Prototypes: */
diff --git a/Projects/SerialToLCD/Descriptors.c b/Projects/SerialToLCD/Descriptors.c
index 8a55f82a44..baf33c0ce0 100644
--- a/Projects/SerialToLCD/Descriptors.c
+++ b/Projects/SerialToLCD/Descriptors.c
@@ -103,7 +103,7 @@ 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,
@@ -154,7 +154,7 @@ 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/Projects/SerialToLCD/Descriptors.h b/Projects/SerialToLCD/Descriptors.h
index 5776098e3a..f6619296de 100644
--- a/Projects/SerialToLCD/Descriptors.h
+++ b/Projects/SerialToLCD/Descriptors.h
@@ -80,15 +80,25 @@
 			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/Projects/SerialToLCD/SerialToLCD.c b/Projects/SerialToLCD/SerialToLCD.c
index aac4fadfb7..21a5d68cb4 100644
--- a/Projects/SerialToLCD/SerialToLCD.c
+++ b/Projects/SerialToLCD/SerialToLCD.c
@@ -51,7 +51,7 @@ USB_ClassInfo_CDC_Device_t VirtualSerial_CDC_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber   = 0,
+				.ControlInterfaceNumber   = INTERFACE_ID_CDC_CCI,
 				.DataINEndpoint           =
 					{
 						.Address          = CDC_TX_EPADDR,
diff --git a/Projects/SerialToLCD/SerialToLCD.h b/Projects/SerialToLCD/SerialToLCD.h
index 22537d6090..bafc03c271 100644
--- a/Projects/SerialToLCD/SerialToLCD.h
+++ b/Projects/SerialToLCD/SerialToLCD.h
@@ -37,28 +37,28 @@
 #ifndef _SERIALTOLCD_H_
 #define _SERIALTOLCD_H_
 
-    /* Includes: */
-        #include <avr/io.h>
-        #include <avr/wdt.h>
-        #include <avr/interrupt.h>
-        #include <avr/power.h>
+	/* Includes: */
+		#include <avr/io.h>
+		#include <avr/wdt.h>
+		#include <avr/interrupt.h>
+		#include <avr/power.h>
 
-        #include "Descriptors.h"
+		#include "Descriptors.h"
 		#include "Lib/HD44780.h"
 
-        #include <LUFA/Version.h>
-        #include <LUFA/Drivers/Misc/RingBuffer.h>
-        #include <LUFA/Drivers/USB/USB.h>
+		#include <LUFA/Version.h>
+		#include <LUFA/Drivers/Misc/RingBuffer.h>
+		#include <LUFA/Drivers/USB/USB.h>
 		#include <LUFA/Platform/Platform.h>
 
 	/* Macros: */
 		#define COMMAND_ESCAPE     0x1B
 
-    /* Function Prototypes: */
-        void SetupHardware(void);
+	/* Function Prototypes: */
+		void SetupHardware(void);
 
-        void EVENT_USB_Device_ConfigurationChanged(void);
-        void EVENT_USB_Device_ControlRequest(void);
+		void EVENT_USB_Device_ConfigurationChanged(void);
+		void EVENT_USB_Device_ControlRequest(void);
 
 #endif
 
diff --git a/Projects/TempDataLogger/Descriptors.c b/Projects/TempDataLogger/Descriptors.c
index 6ec6f64aac..452c4c6ec3 100644
--- a/Projects/TempDataLogger/Descriptors.c
+++ b/Projects/TempDataLogger/Descriptors.c
@@ -109,7 +109,7 @@ 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,
@@ -145,7 +145,7 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 		{
 			.Header                 = {.Size = sizeof(USB_Descriptor_Interface_t), .Type = DTYPE_Interface},
 
-			.InterfaceNumber        = 1,
+			.InterfaceNumber        = INTERFACE_ID_HID,
 			.AlternateSetting       = 0,
 
 			.TotalEndpoints         = 1,
diff --git a/Projects/TempDataLogger/Descriptors.h b/Projects/TempDataLogger/Descriptors.h
index 91e238fc1d..63c3fae02b 100644
--- a/Projects/TempDataLogger/Descriptors.h
+++ b/Projects/TempDataLogger/Descriptors.h
@@ -56,15 +56,25 @@
 			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_HID         = 1, /**< HID 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/Projects/TempDataLogger/TempDataLogger.c b/Projects/TempDataLogger/TempDataLogger.c
index bbbea47f20..66f933586d 100644
--- a/Projects/TempDataLogger/TempDataLogger.c
+++ b/Projects/TempDataLogger/TempDataLogger.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,
@@ -72,7 +72,7 @@ USB_ClassInfo_HID_Device_t Generic_HID_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber              = 1,
+				.InterfaceNumber              = INTERFACE_ID_HID,
 				.ReportINEndpoint             =
 					{
 						.Address              = GENERIC_IN_EPADDR,
diff --git a/Projects/USBtoSerial/Descriptors.c b/Projects/USBtoSerial/Descriptors.c
index b2d228588f..ea0a84a0c5 100644
--- a/Projects/USBtoSerial/Descriptors.c
+++ b/Projects/USBtoSerial/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/Projects/USBtoSerial/Descriptors.h b/Projects/USBtoSerial/Descriptors.h
index 363951c5b6..ed19d84f82 100644
--- a/Projects/USBtoSerial/Descriptors.h
+++ b/Projects/USBtoSerial/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/Projects/USBtoSerial/USBtoSerial.c b/Projects/USBtoSerial/USBtoSerial.c
index 6df9063403..84ec2befa6 100644
--- a/Projects/USBtoSerial/USBtoSerial.c
+++ b/Projects/USBtoSerial/USBtoSerial.c
@@ -56,7 +56,7 @@ USB_ClassInfo_CDC_Device_t VirtualSerial_CDC_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber         = 0,
+				.ControlInterfaceNumber         = INTERFACE_ID_CDC_CCI,
 				.DataINEndpoint                 =
 					{
 						.Address                = CDC_TX_EPADDR,
diff --git a/Projects/Webserver/Descriptors.c b/Projects/Webserver/Descriptors.c
index 8fcba5cc84..b8acf42a2a 100644
--- a/Projects/Webserver/Descriptors.c
+++ b/Projects/Webserver/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/Projects/Webserver/Descriptors.h b/Projects/Webserver/Descriptors.h
index 2c25512e40..c649cf56f7 100644
--- a/Projects/Webserver/Descriptors.h
+++ b/Projects/Webserver/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/Projects/Webserver/USBDeviceMode.c b/Projects/Webserver/USBDeviceMode.c
index 7d5beb93aa..f889b6be61 100644
--- a/Projects/Webserver/USBDeviceMode.c
+++ b/Projects/Webserver/USBDeviceMode.c
@@ -44,7 +44,7 @@ USB_ClassInfo_RNDIS_Device_t Ethernet_RNDIS_Interface_Device =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber         = 0,
+				.ControlInterfaceNumber         = INTERFACE_ID_CDC_CCI,
 				.DataINEndpoint                 =
 					{
 						.Address                = CDC_TX_EPADDR,
@@ -76,7 +76,7 @@ USB_ClassInfo_MS_Device_t Disk_MS_Interface =
 	{
 		.Config =
 			{
-				.InterfaceNumber                = 2,
+				.InterfaceNumber                = INTERFACE_ID_MassStorage,
 				.DataINEndpoint                 =
 					{
 						.Address                = MASS_STORAGE_IN_EPADDR,
diff --git a/Projects/XPLAINBridge/USARTDescriptors.c b/Projects/XPLAINBridge/USARTDescriptors.c
index 0e0ac8534d..b1bfd4e816 100644
--- a/Projects/XPLAINBridge/USARTDescriptors.c
+++ b/Projects/XPLAINBridge/USARTDescriptors.c
@@ -91,7 +91,7 @@ const USART_USB_Descriptor_Configuration_t PROGMEM USART_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 USART_USB_Descriptor_Configuration_t PROGMEM USART_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/Projects/XPLAINBridge/USARTDescriptors.h b/Projects/XPLAINBridge/USARTDescriptors.h
index 954867c187..130c695b9a 100644
--- a/Projects/XPLAINBridge/USARTDescriptors.h
+++ b/Projects/XPLAINBridge/USARTDescriptors.h
@@ -81,22 +81,32 @@
 			USB_Descriptor_Endpoint_t                CDC_DataInEndpoint;
 		} USART_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 USART_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 USART_StringDescriptors_t
 		{
-		    USART_STRING_ID_Language      = 0, /**< Supported Languages string descriptor ID (must be zero) */
-		    USART_STRING_ID_Manufacturer  = 1, /**< Manufacturer string ID */
-		    USART_STRING_ID_Product       = 2, /**< Product string ID */
+			USART_STRING_ID_Language     = 0, /**< Supported Languages string descriptor ID (must be zero) */
+			USART_STRING_ID_Manufacturer = 1, /**< Manufacturer string ID */
+			USART_STRING_ID_Product      = 2, /**< Product string ID */
 		};
 
 	/* Function Prototypes: */
 		uint16_t USART_GetDescriptor(const uint16_t wValue,
 		                             const uint8_t wIndex,
 		                             const void** const DescriptorAddress,
-									 uint8_t* const DescriptorMemorySpace);
+		                             uint8_t* const DescriptorMemorySpace);
 
 #endif
 
diff --git a/Projects/XPLAINBridge/XPLAINBridge.c b/Projects/XPLAINBridge/XPLAINBridge.c
index 2ef1d20ee2..1c63b71d8b 100644
--- a/Projects/XPLAINBridge/XPLAINBridge.c
+++ b/Projects/XPLAINBridge/XPLAINBridge.c
@@ -47,7 +47,7 @@ USB_ClassInfo_CDC_Device_t VirtualSerial_CDC_Interface =
 	{
 		.Config =
 			{
-				.ControlInterfaceNumber         = 0,
+				.ControlInterfaceNumber         = INTERFACE_ID_CDC_CCI,
 				.DataINEndpoint                 =
 					{
 						.Address                = CDC_TX_EPADDR,