Add Serial + MIDI option

teensy3/usb_desc.h

   #define ENDPOINT3_CONFIG	ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT4_CONFIG	ENDPOINT_RECEIVE_ONLY
 
+#elif defined(USB_MIDI_SERIAL)
+  #define VENDOR_ID		0x16C0
+  #define PRODUCT_ID		0x0485
+  #define MANUFACTURER_NAME	{'T','e','e','n','s','y','d','u','i','n','o'}
+  #define MANUFACTURER_NAME_LEN	11
+  #define PRODUCT_NAME		{'T','e','e','n','s','y',' ','M','I','D','I'}
+  #define PRODUCT_NAME_LEN	11
+  #define EP0_SIZE		64
+  #define NUM_ENDPOINTS         5
+  #define NUM_USB_BUFFERS	30
+  #define NUM_INTERFACE		3
+  #define CDC_IAD_DESCRIPTOR	1
+  #define CDC_STATUS_INTERFACE	0
+  #define CDC_DATA_INTERFACE	1	// Serial
+  #define CDC_ACM_ENDPOINT	1
+  #define CDC_RX_ENDPOINT       2
+  #define CDC_TX_ENDPOINT       3
+  #define CDC_ACM_SIZE          16
+  #define CDC_RX_SIZE           64
+  #define CDC_TX_SIZE           64
+  #define MIDI_INTERFACE        2	// MIDI
+  #define MIDI_TX_ENDPOINT      4
+  #define MIDI_TX_SIZE          64
+  #define MIDI_RX_ENDPOINT      5
+  #define MIDI_RX_SIZE          64
+  #define ENDPOINT1_CONFIG	ENDPOINT_TRANSIMIT_ONLY
+  #define ENDPOINT2_CONFIG	ENDPOINT_RECEIVE_ONLY
+  #define ENDPOINT3_CONFIG	ENDPOINT_TRANSIMIT_ONLY
+  #define ENDPOINT4_CONFIG	ENDPOINT_TRANSIMIT_ONLY
+  #define ENDPOINT5_CONFIG	ENDPOINT_RECEIVE_ONLY
+
 #elif defined(USB_RAWHID)
   #define VENDOR_ID		0x16C0
   #define PRODUCT_ID		0x0486