Index: firmware/App/Services/SystemComm.h
===================================================================
diff -u -rde5a0d43bdef611d963d11855bc958a8d8899a09 -r101bf85b0b425e919b01b4b7fabcbd15fd5bbde5
--- firmware/App/Services/SystemComm.h	(.../SystemComm.h)	(revision de5a0d43bdef611d963d11855bc958a8d8899a09)
+++ firmware/App/Services/SystemComm.h	(.../SystemComm.h)	(revision 101bf85b0b425e919b01b4b7fabcbd15fd5bbde5)
@@ -22,22 +22,30 @@
 #include "CommBuffers.h"
 #include "MsgQueues.h"
 
+/**
+ *  @defgroup SystemComm SystemComm
+ *  @brief System communication module.  Manages incoming and outgoing CAN frames.
+ *
+ *  @addtogroup SystemComm
+ *  @{
+ */
+
 // ********** public definitions **********
 
-#define MESSAGE_SYNC_BYTE           0xA5
+#define MESSAGE_SYNC_BYTE           0xA5                                                            ///< Denali message syncronization byte.
 
-#define CAN_MESSAGE_PAYLOAD_SIZE    8
+#define CAN_MESSAGE_PAYLOAD_SIZE    8                                                               ///< CAN frame payload size (in bytes).
 #ifdef DEBUG_ENABLED
     #define PC_MESSAGE_PACKET_SIZE  8
 #endif
 
-#define MSG_ID_ACK                  0xFFFF
-#define MSG_ACK_BIT                 0x8000
-#define MAX_MSG_SEQ_NO              0x7FFF
-#define MIN_MSG_SEQ_NO              0x0001
-#define MAX_ACK_MSG_SIZE            ( sizeof( MESSAGE_WRAPPER_T ) + 1 + CAN_MESSAGE_PAYLOAD_SIZE )  // must hold full (wrapped) message + sync + any CAN padding
+#define MSG_ID_ACK                  0xFFFF                                                          ///< Denali message ID for acknowledging received messages (when required).
+#define MSG_ACK_BIT                 0x8000                                                          ///< ACK bit in sequence number that indicates an ACK is required.
+#define MAX_MSG_SEQ_NO              0x7FFF                                                          ///< Maximum sequence number for Denali message (then wraps to 1).
+#define MIN_MSG_SEQ_NO              0x0001                                                          ///< Minimum sequence number for Denali message.
+#define MAX_ACK_MSG_SIZE            ( sizeof( MESSAGE_WRAPPER_T ) + 1 + CAN_MESSAGE_PAYLOAD_SIZE )  ///< Maximum size (in bytes) of Denali message including full (wrapped) message + sync + any CAN padding)
 
-typedef COMM_BUFFER_T   CAN_MESSAGE_BOX_T;       // the CAN comm buffers align with the active CAN message boxes
+typedef COMM_BUFFER_T   CAN_MESSAGE_BOX_T;                                                          ///< the CAN comm buffers align with the active CAN message boxes
 
 // ********** public function prototypes **********
 
@@ -49,11 +57,16 @@
 void handleUARTMsgRecvPacketInterrupt( void );
 void handleUARTMsgXmitPacketInterrupt( void );
 #endif
+BOOL isCANBoxForXmit( CAN_MESSAGE_BOX_T srcCANBox );
+BOOL isCANBoxForRecv( CAN_MESSAGE_BOX_T srcCANBox );
 void checkInFromDG( void );
 void checkInFromUI( void );
 BOOL isDGCommunicating( void );
 BOOL isUICommunicating( void );
-BOOL uiCommunicated( void );
+BOOL uiCommunicated( void );
+BOOL isHDOnlyCANNode( void );
 BOOL addMsgToPendingACKList( MESSAGE_T *msg, COMM_BUFFER_T channel, U08 *msgData, U32 len );
+
+/**@}*/
 
 #endif