Index: firmware/App/Services/SystemComm.c
===================================================================
diff -u -r8f8776e48894e31cba816ebef2edf96d14306ba8 -r4a41a54d255afc5cef0599e2a832927ed2b0ee5d
--- firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 8f8776e48894e31cba816ebef2edf96d14306ba8)
+++ firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 4a41a54d255afc5cef0599e2a832927ed2b0ee5d)
@@ -72,10 +72,12 @@
 static g_dmaCTRL pcDMAXmitControlRecord;            // DMA transmit control record (UART-debug)
 static g_dmaCTRL pcDMARecvControlRecord;            // DMA receive control record (UART-debug)
 
-static BOOL dgIsCommunicating = FALSE;              // has DG sent a message since last check
-static BOOL uiIsCommunicating = FALSE;              // has UI sent a message since last check
-static BOOL uiDidCommunicate = FALSE;               // has UI every sent a message
+static volatile BOOL canXmitSucceeded = FALSE;      // indicates that the last CAN packet transmitted was successful
 
+static volatile BOOL dgIsCommunicating = FALSE;     // has DG sent a message since last check
+static volatile BOOL uiIsCommunicating = FALSE;     // has UI sent a message since last check
+static volatile BOOL uiDidCommunicate = FALSE;      // has UI every sent a message
+
 // ********** private function prototypes **********
 
 static void initUARTAndDMA( void );
@@ -250,14 +252,12 @@
     // message interrupt is for a transmit message box?
     if ( TRUE == isCANBoxForXmit( srcCANBox ) )
     {
-        if ( FALSE == canIsTxMessagePending( canREG1, srcCANBox ) )
-        {
-            U32 bytesXmitted = transmitNextCANPacket();
+        //U32 bytesXmitted = transmitNextCANPacket();
 
-            if ( 0 == bytesXmitted )
-            {
-                signalCANXmitsCompleted();
-            }
+        //if ( 0 == bytesXmitted )
+        {
+            canXmitSucceeded = TRUE;
+            signalCANXmitsCompleted();
         }
     }
     else if ( TRUE == isCANBoxForRecv( srcCANBox ) )
@@ -485,33 +485,43 @@
 static U32 transmitNextCANPacket( void )
 {
     U32 result = 0;
-    COMM_BUFFER_T buffer = findNextHighestPriorityCANPacketToTransmit();
-
-    // if a buffer is found with a packet to transmit, get packet from buffer and transmit it
-    if ( buffer != COMM_BUFFER_NOT_USED )
+    while ( 1 ) // TODO - add timeout and/or max packets per call
     {
-        U08 data[ CAN_MESSAGE_PAYLOAD_SIZE ];
-        U32 dataSize = getFromCommBuffer( buffer, data, CAN_MESSAGE_PAYLOAD_SIZE );
-        CAN_MESSAGE_BOX_T mBox = buffer;  // CAN message boxes and comm buffers are aligned
+        COMM_BUFFER_T buffer = findNextHighestPriorityCANPacketToTransmit();
 
-        // if there's another CAN packet to send, send it
-        if ( dataSize == CAN_MESSAGE_PAYLOAD_SIZE )
+        // if a buffer is found with a packet to transmit, get packet from buffer and transmit it
+        if ( buffer != COMM_BUFFER_NOT_USED )
         {
-            signalCANXmitsInitiated();
-            if ( 0 != canTransmit( canREG1, mBox, data ) )
+            U08 data[ CAN_MESSAGE_PAYLOAD_SIZE ];
+            U32 dataSize = getFromCommBuffer( buffer, data, CAN_MESSAGE_PAYLOAD_SIZE );
+            CAN_MESSAGE_BOX_T mBox = buffer;  // CAN message boxes and comm buffers are aligned
+
+            // if there's another CAN packet to send, send it
+            if ( dataSize == CAN_MESSAGE_PAYLOAD_SIZE )
             {
-                result = CAN_MESSAGE_PAYLOAD_SIZE;
+                signalCANXmitsInitiated();
+                if ( 0 != canTransmit( canREG1, mBox, data ) )
+                {
+                    result = CAN_MESSAGE_PAYLOAD_SIZE;
+
+                    canXmitSucceeded = FALSE;
+                    while ( FALSE == canXmitSucceeded );  // TODO - add timeout (2ms)
+                }
+                else
+                {
+                    signalCANXmitsCompleted();
+                    // TODO - shouldn't get here, but let's see if we do
+                    SET_ALARM_WITH_1_U32_DATA( ALARM_ID_SOFTWARE_FAULT, (U32)mBox )
+                }
             }
             else
-            {
-                signalCANXmitsCompleted();
-                // TODO - shouldn't get here, but let's see if we do
-                SET_ALARM_WITH_1_U32_DATA( ALARM_ID_SOFTWARE_FAULT, (U32)mBox )
+            {   // TODO - shouldn't get here - just testing - set first data to new s/w fault enum later
+                SET_ALARM_WITH_2_U32_DATA( ALARM_ID_SOFTWARE_FAULT, (U32)buffer, (U32)dataSize )
             }
         }
         else
-        {   // TODO - shouldn't get here - just testing - set first data to new s/w fault enum later
-            SET_ALARM_WITH_2_U32_DATA( ALARM_ID_SOFTWARE_FAULT, (U32)buffer, (U32)dataSize )
+        {
+            break;
         }
     }