diff --git a/USBHost.h b/USBHost_t36.h
similarity index 94%
rename from USBHost.h
rename to USBHost_t36.h
index 3d68fbc..43e7310 100644
--- a/USBHost.h
+++ b/USBHost_t36.h
@@ -29,16 +29,39 @@
 #define USBHOST_PRINT_DEBUG
 
 /************************************************/
-/*  Data Structure Definitions                  */
+/*  Data Types                                  */
 /************************************************/
 
+These 6 types are the key to understanding how this USB Host
+library really works.
+
+// USBHost is a static class controlling the hardware.
+// All common USB functionality is implemented here.
 class USBHost;
-class USBDriver;
-class USBDriverTimer;
+
+// These 3 structures represent the actual USB entities
+// USBHost manipulates.  One Device_t is created for
+// each active USB device.  One Pipe_t is create for
+// each endpoint.  Transfer_t structures are created
+// when any data transfer is added to the EHCI work
+// queues, and then returned to the free pool after the
+// data transfer completes and the driver has processed
+// the results.
 typedef struct Device_struct       Device_t;
 typedef struct Pipe_struct         Pipe_t;
 typedef struct Transfer_struct     Transfer_t;
-//typedef struct DriverTimer_struct  DriverTimer_t;
+
+// All USB device drivers inherit use these classes.
+// Drivers build user-visible functionality on top
+// of these classes, which receive USB events from
+// USBHost.
+class USBDriver;
+class USBDriverTimer;
+
+
+/************************************************/
+/*  Data Structure Definitions                  */
+/************************************************/
 
 // setup_t holds the 8 byte USB SETUP packet data.
 // These unions & structs allow convenient access to
@@ -99,12 +122,12 @@ struct Pipe_struct {
 	Device_t *device;
 	uint8_t  type; // 0=control, 1=isochronous, 2=bulk, 3=interrupt
 	uint8_t  direction; // 0=out, 1=in (changes for control, others fixed)
-	uint8_t  start_mask;       // TODO: is this redundant?
-	uint8_t  complete_mask;    // TODO: is this redundant?
+	uint8_t  start_mask;
+	uint8_t  complete_mask;
 	Pipe_t   *next;
 	void     (*callback_function)(const Transfer_t *);
 	uint16_t periodic_interval;
-	uint16_t periodic_offset;  // TODO: is this redundant?
+	uint16_t periodic_offset;
 	uint32_t unused1;
 	uint32_t unused2;
 	uint32_t unused3;
@@ -251,7 +274,6 @@ protected:
 	static void println(const char *s, long n, uint8_t b) {}
 	static void println(const char *s, unsigned long n, uint8_t b) {}
 #endif
-
 	static void mk_setup(setup_t &s, uint32_t bmRequestType, uint32_t bRequest,
 			uint32_t wValue, uint32_t wIndex, uint32_t wLength) {
 		s.word1 = bmRequestType | (bRequest << 8) | (wValue << 16);
@@ -381,7 +403,6 @@ protected:
 	void start_debounce_timer(uint32_t port);
 	void stop_debounce_timer(uint32_t port);
 	static volatile bool reset_busy;
-
 	USBDriverTimer debouncetimer;
 	USBDriverTimer resettimer;
 	setup_t setup;
diff --git a/ehci.cpp b/ehci.cpp
index 975cac3..6ea9260 100644
--- a/ehci.cpp
+++ b/ehci.cpp
@@ -22,7 +22,7 @@
  */
 
 #include <Arduino.h>
-#include "USBHost.h"
+#include "USBHost_t36.h" // Read this header first for key info
 
 // Size of the periodic list, in milliseconds.  This determines the
 // slowest rate we can poll interrupt endpoints.  Each entry uses
diff --git a/enumeration.cpp b/enumeration.cpp
index 028c2a6..cbd5fce 100644
--- a/enumeration.cpp
+++ b/enumeration.cpp
@@ -22,7 +22,7 @@
  */
 
 #include <Arduino.h>
-#include "USBHost.h"
+#include "USBHost_t36.h"  // Read this header first for key info
 
 
 static USBDriver *available_drivers = NULL;
diff --git a/hub.cpp b/hub.cpp
index 7fd6aff..9c2149d 100644
--- a/hub.cpp
+++ b/hub.cpp
@@ -22,7 +22,7 @@
  */
 
 #include <Arduino.h>
-#include "USBHost.h"
+#include "USBHost_t36.h"  // Read this header first for key info
 
 // True when any hub port is in the reset or reset recovery phase.
 // Only one USB device may be reset at a time, because it will
diff --git a/keyboard.cpp b/keyboard.cpp
index debf998..e5dba5e 100644
--- a/keyboard.cpp
+++ b/keyboard.cpp
@@ -22,7 +22,7 @@
  */
 
 #include <Arduino.h>
-#include "USBHost.h"
+#include "USBHost_t36.h"  // Read this header first for key info
 
 
 KeyboardController::KeyboardController()
diff --git a/memory.cpp b/memory.cpp
index ec6a704..221558b 100644
--- a/memory.cpp
+++ b/memory.cpp
@@ -22,7 +22,7 @@
  */
 
 #include <Arduino.h>
-#include "USBHost.h"
+#include "USBHost_t36.h"  // Read this header first for key info
 
 
 // Memory allocation
diff --git a/midi.cpp b/midi.cpp
index 0ca648b..a88fdf4 100644
--- a/midi.cpp
+++ b/midi.cpp
@@ -22,7 +22,7 @@
  */
 
 #include <Arduino.h>
-#include "USBHost.h"
+#include "USBHost_t36.h"  // Read this header first for key info
 
 
 MIDIDevice::MIDIDevice()
diff --git a/print.cpp b/print.cpp
index 3b54fe2..aac2abf 100644
--- a/print.cpp
+++ b/print.cpp
@@ -22,7 +22,7 @@
  */
 
 #include <Arduino.h>
-#include "USBHost.h"
+#include "USBHost_t36.h"  // Read this header first for key info
 
 #ifdef USBHOST_PRINT_DEBUG