Index: firmware/App/Services/SystemComm.h
===================================================================
diff -u -ra303cd4258157a8fbcbd8af4dd2bbaadec1a736c -rf068446fdb7889d320ddb6ffbd58f347ce0501e7
--- firmware/App/Services/SystemComm.h	(.../SystemComm.h)	(revision a303cd4258157a8fbcbd8af4dd2bbaadec1a736c)
+++ firmware/App/Services/SystemComm.h	(.../SystemComm.h)	(revision f068446fdb7889d320ddb6ffbd58f347ce0501e7)
@@ -19,6 +19,7 @@
 
 #include "Common.h"
 #include "CommBuffers.h"
+#include "MsgQueues.h"
 
 // ********** public definitions **********
 
@@ -27,8 +28,14 @@
 #define CAN_MESSAGE_PAYLOAD_SIZE    8
 #define PC_MESSAGE_PACKET_SIZE      8
 
-typedef COMM_BUFFER_T   CAN_MESSAGE_BOX_T;       // the first 10 comm buffers align with the 10 active CAN message boxes
+#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
 
+typedef COMM_BUFFER_T   CAN_MESSAGE_BOX_T;       // the first 12 comm buffers align with the 12 active CAN message boxes
+
 // ********** public function prototypes **********
 
 void initSystemComm( void );
@@ -37,5 +44,9 @@
 void handleCANMsgInterrupt( CAN_MESSAGE_BOX_T srcCANBox );
 void handleUARTMsgRecvPacketInterrupt( void );
 void handleUARTMsgXmitPacketInterrupt( void );
+BOOL isHDCommunicating( void );
+#ifndef ACK_NOT_IMPLEMENTED
+BOOL addMsgToPendingACKList( MESSAGE_T *msg, COMM_BUFFER_T channel, U08 *msgData, U32 len );
+#endif
 
 #endif