Index: firmware/App/Services/SystemComm.c
===================================================================
diff -u -r36a2fa774e2f5721c30261a40360d706bb4ea4bb -r4d27576bdd7843178d9b69ffff3584ee01ec24fe
--- firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 36a2fa774e2f5721c30261a40360d706bb4ea4bb)
+++ firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 4d27576bdd7843178d9b69ffff3584ee01ec24fe)
@@ -42,6 +42,8 @@
 #define SCI1_RECEIVE_DMA_REQUEST        30
 #define SCI1_TRANSMIT_DMA_REQUEST       31
 
+#define CAN_XMIT_PACKET_TIMEOUT_MS      200     ///< if transmitted CAN frame does not cause a transmit complete interrupt within this time, re-send or move on
+
 #define HD_COMM_TIMEOUT_IN_MS           2000
 
 #define MAX_COMM_CRC_FAILURES           5
@@ -87,6 +89,10 @@
     COMM_BUFFER_IN_UART_PC
 };
 
+static U08 lastCANPacketSent[ CAN_MESSAGE_PAYLOAD_SIZE ];
+static CAN_MESSAGE_BOX_T lastCANPacketSentChannel = 0;
+static U32 lastCANPacketSentTimeStamp = 0;
+
 static U08 pcXmitPacket[ PC_MESSAGE_PACKET_SIZE ] = { 0, 0, 0, 0, 0, 0, 0, 0 };
 static U08 pcRecvPacket[ PC_MESSAGE_PACKET_SIZE ] = { 0, 0, 0, 0, 0, 0, 0, 0 };
 
@@ -105,6 +111,15 @@
 static U32 badCRCListIdx = 0;                           // where next bad message CRC time stamp will go in list
 static U32 badCRCListCount = 0;                         // # of bad CRCs in the list
 
+#ifdef CAN_TEST
+U08 dbgRcvdCANFrames[1024][8];
+U32 dbgRcvdCANFrameTS[1024];
+U32 dbgRcvdCANFrameIdx = 0;
+U08 dbgXmitCANFrames[1024][8];
+U32 dbgXmitCANFrameTS[1024];
+U32 dbgXmitCANFrameIdx = 0;
+#endif
+
 // ********** private function prototypes **********
 
 static void initUARTAndDMA( void );
@@ -222,6 +237,15 @@
     {
         transmitNextCANPacket();
     }
+    else
+    {   // generally, transmitter should not be busy at time of this function call - check timeout just in case so we don't get stuck waiting forever
+        if ( TRUE == didTimeout( lastCANPacketSentTimeStamp, CAN_XMIT_PACKET_TIMEOUT_MS ) )
+        {
+            // TODO - depending on why we timed out, we may need to reset CAN controller???
+            // assume last packet was not successfully transmitted.  TODO - Re-send last packet?  Or should we move on?
+            canTransmit( canREG1, lastCANPacketSentChannel, lastCANPacketSent );
+        }
+    }
 
     // if UART transmitter is idle, start transmitting any pending packets
     if ( FALSE == isSCI1DMATransmitInProgress() )
@@ -266,6 +290,18 @@
             // if packet retrieved, add to buffer
             if ( result != 0 )
             {
+#ifdef CAN_TEST
+                if ( dbgRcvdCANFrameIdx >= 1000 )
+                {
+                    result = 99;  // Break point here
+                }
+                else
+                {
+                    dbgRcvdCANFrameTS[dbgRcvdCANFrameIdx] = getMSTimerCount();
+                    memcpy( &dbgRcvdCANFrames[dbgRcvdCANFrameIdx][0], data, 8);
+                    dbgRcvdCANFrameIdx++;
+                }
+#endif
 //#ifdef DEBUG_ENABLED
 //                if ( srcCANBox == COMM_BUFFER_IN_CAN_PC )
 //                {
@@ -503,7 +539,24 @@
         // if there's another CAN packet to send, send it
         if ( dataSize == CAN_MESSAGE_PAYLOAD_SIZE )
         {
+            // we're transmitting another packet - signal transmitter is busy
             signalCANXmitsInitiated();
+            // remember packet data being transmitted here in case transmission fails and we need to re-send
+            memcpy( lastCANPacketSent, data, CAN_MESSAGE_PAYLOAD_SIZE );
+            lastCANPacketSentChannel = mBox;
+            lastCANPacketSentTimeStamp = getMSTimerCount();
+#ifdef CAN_TEST
+            if ( dbgXmitCANFrameIdx > 1000 )
+            {
+                dataSize = 99; // Break point here
+            }
+            else
+            {
+                dbgXmitCANFrameTS[dbgXmitCANFrameIdx] = getMSTimerCount();
+                memcpy( &dbgXmitCANFrames[dbgXmitCANFrameIdx][0], data, 8);
+                dbgXmitCANFrameIdx++;
+            }
+#endif
             if ( 0 != canTransmit( canREG1, mBox, data ) )
             {
                 result = CAN_MESSAGE_PAYLOAD_SIZE;