Index: firmware/App/Services/SystemComm.c
===================================================================
diff -u -r48278ac6fa3738a97349ed7f3278773daf1d8004 -r8dfdaca983c36456b0e067a20ef6c003da3758ac
--- firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 48278ac6fa3738a97349ed7f3278773daf1d8004)
+++ firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 8dfdaca983c36456b0e067a20ef6c003da3758ac)
@@ -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 UI_COMM_TIMEOUT_IN_MS           5000
 #define DG_COMM_TIMEOUT_IN_MS           2000
 
@@ -90,6 +92,10 @@
     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 };
 
@@ -311,6 +317,15 @@
     {
         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() )
@@ -320,18 +335,18 @@
 #ifdef CAN_TEST
     if ( dbgRcvdCANFrameIdx >= 2000 )
     {
-        U32 i = dbgCANOutIdx;
-        char debugStr[ 150 ];
-
-        dbgCANOutIdx++;
-        if ( dbgCANOutIdx < 2000 )
-        {
-        sprintf( debugStr, "%8d %4d %02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X     %8d %4d %02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X\n",
-                 dbgRcvdCANFrameTS[i], dbgRcvdCANFrameCh[i], dbgRcvdCANFrames[i][0], dbgRcvdCANFrames[i][1], dbgRcvdCANFrames[i][2], dbgRcvdCANFrames[i][3], dbgRcvdCANFrames[i][4], dbgRcvdCANFrames[i][5], dbgRcvdCANFrames[i][6], dbgRcvdCANFrames[i][7],
-                 dbgXmitCANFrameTS[i], dbgXmitCANFrameCh[i], dbgXmitCANFrames[i][0], dbgXmitCANFrames[i][1], dbgXmitCANFrames[i][2], dbgXmitCANFrames[i][3], dbgXmitCANFrames[i][4], dbgXmitCANFrames[i][5], dbgXmitCANFrames[i][6], dbgXmitCANFrames[i][7]);
-        sendDebugData( (U08*)debugStr, strlen(debugStr) );
+//        U32 i = dbgCANOutIdx;
+//        char debugStr[ 150 ];
+//
+//        dbgCANOutIdx++;
+//        if ( dbgCANOutIdx < 2000 )
+//        {
+//        sprintf( debugStr, "%8d %4d %02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X     %8d %4d %02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X\n",
+//                 dbgRcvdCANFrameTS[i], dbgRcvdCANFrameCh[i], dbgRcvdCANFrames[i][0], dbgRcvdCANFrames[i][1], dbgRcvdCANFrames[i][2], dbgRcvdCANFrames[i][3], dbgRcvdCANFrames[i][4], dbgRcvdCANFrames[i][5], dbgRcvdCANFrames[i][6], dbgRcvdCANFrames[i][7],
+//                 dbgXmitCANFrameTS[i], dbgXmitCANFrameCh[i], dbgXmitCANFrames[i][0], dbgXmitCANFrames[i][1], dbgXmitCANFrames[i][2], dbgXmitCANFrames[i][3], dbgXmitCANFrames[i][4], dbgXmitCANFrames[i][5], dbgXmitCANFrames[i][6], dbgXmitCANFrames[i][7]);
+//        sendDebugData( (U08*)debugStr, strlen(debugStr) );
 //        printf(debugStr);
-        }
+//        }
     }
 #endif
 }
@@ -355,6 +370,7 @@
     {
         U32 bytesXmitted = transmitNextCANPacket();
 
+        // if nothing more to send, signal that transmitter is available
         if ( 0 == bytesXmitted )
         {
             signalCANXmitsCompleted();
@@ -622,19 +638,24 @@
         // 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 > 2000 )
-            {
-                dataSize = 99; // Break point here
-            }
-            else
-            {
-                dbgXmitCANFrameTS[dbgXmitCANFrameIdx] = getMSTimerCount();
-                dbgXmitCANFrameCh[dbgXmitCANFrameIdx] = mBox;
-                memcpy( &dbgXmitCANFrames[dbgXmitCANFrameIdx][0], data, 8);
-                dbgXmitCANFrameIdx++;
-            }
+//            if ( dbgXmitCANFrameIdx > 2000 )
+//            {
+//                dataSize = 99; // Break point here
+//            }
+//            else
+//            {
+//                dbgXmitCANFrameTS[dbgXmitCANFrameIdx] = getMSTimerCount();
+//                dbgXmitCANFrameCh[dbgXmitCANFrameIdx] = mBox;
+//                memcpy( &dbgXmitCANFrames[dbgXmitCANFrameIdx][0], data, 8);
+//                dbgXmitCANFrameIdx++;
+//            }
 #endif
             if ( 0 != canTransmit( canREG1, mBox, data ) )
             {