Index: firmware/App/Services/SystemComm.c
===================================================================
diff -u -r699c4f96ab672fb9db9ac218a5a00358dc68c2c6 -r2db16f950f61815bd8be6d7d300a82eb1f6ee6da
--- firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 699c4f96ab672fb9db9ac218a5a00358dc68c2c6)
+++ firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 2db16f950f61815bd8be6d7d300a82eb1f6ee6da)
@@ -231,45 +231,57 @@
  * @return none
  *************************************************************************/
 void execSystemCommTx( void )
-{
-    // if CAN transmitter is idle, start transmitting any pending packets
-    if ( ( FALSE == dgIsOnlyCANNode ) && ( FALSE == isCAN1TransmitInProgress() ) )
-    {
-        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 ) )
+{
+    // don't bother with transmitting if no other nodes on CAN bus
+    if ( FALSE == dgIsOnlyCANNode )
+    {
+        // if CAN transmitter is idle, start transmitting any pending packets
+        if ( FALSE == isCAN1TransmitInProgress() )
         {
-            // assume last packet was not successfully transmitted.  Re-send last packet.
-            if ( ++canXmitRetryCtr <= MAX_XMIT_RETRIES )
+            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 ) )
             {
-                canTransmit( canREG1, lastCANPacketSentChannel, lastCANPacketSent );
-#ifdef DEBUG_ENABLED
+                // assume last packet was not successfully transmitted.  Re-send last packet.
+                if ( ++canXmitRetryCtr <= MAX_XMIT_RETRIES )
                 {
-                    char debugStr[100];
-                    sprintf( debugStr, "SystemComm-DG resend Last Frame.\n" );
-                    sendDebugDataToUI( (U08*)debugStr );
-                }
-#endif
-            }
-            // we must be only node on CAN bus - nobody is ACKing our transmitted frames
-            else
-            {
-                dgIsOnlyCANNode = TRUE;     // set only CAN node flag
-                canXmitRetryCtr = MAX_XMIT_RETRIES;
-                signalCANXmitsCompleted();  // clear pending xmit flag
-                clearCANXmitBuffers();      // clear xmit buffers - nothing is going out right now
+                    // ensure we have a previous CAN packet/channel to resend - canTransmit() channel param MUST be valid
+                    if ( ( lastCANPacketSentChannel > COMM_BUFFER_NOT_USED ) && ( lastCANPacketSentChannel <= COMM_BUFFER_LAST_CAN_BUFFER ) )
+                    {
+                        canTransmit( canREG1, lastCANPacketSentChannel, lastCANPacketSent );
+                    }
 #ifdef DEBUG_ENABLED
-                {
-                    char debugStr[100];
-                    sprintf( debugStr, "SystemComm-DG is only node.\n" );
-                    sendDebugDataToUI( (U08*)debugStr );
+                    {
+                        char debugStr[100];
+                        strcpy( debugStr, "SystemComm-DG resend Last Frame.\n" );
+                        sendDebugData( (U08*)debugStr, strlen(debugStr) );
+                        sendDebugDataToUI( (U08*)debugStr );
+                    }
+#endif
                 }
+                // we must be only node on CAN bus - nobody is ACKing our transmitted frames
+                else
+                {
+                    if ( FALSE == dgIsOnlyCANNode )
+                    {
+#ifdef DEBUG_ENABLED
+                        char debugStr[100];
+                        strcpy( debugStr, "SystemComm-DG is only node.\n" );
+                        sendDebugData( (U08*)debugStr, strlen(debugStr) );
+                        sendDebugDataToUI( (U08*)debugStr );
 #endif
-            }
-        }
-    }
+                        dgIsOnlyCANNode = TRUE;     // set only CAN node flag
+                        canXmitRetryCtr = MAX_XMIT_RETRIES;
+                        signalCANXmitsCompleted();  // clear pending xmit flag
+                        clearCANXmitBuffers();      // clear xmit buffers - nothing is going out right now
+                    }
+                } // end - are we retrying xmit or are we alone on CAN bus
+            } // end - pending xmit timeout?
+        } // end - transmit in progress or not
+    } // end - DG not alone on CAN bus
 
 #ifdef DEBUG_ENABLED
     // if UART transmitter is idle, start transmitting any pending packets
@@ -883,7 +895,8 @@
 #ifdef DEBUG_ENABLED
     {
         char debugStr[100];
-        sprintf( debugStr, "SystemComm-DG-Bad Msg CRC.\n" );
+
+        strcpy( debugStr, "SystemComm-DG-Bad Msg CRC.\n" );
         sendDebugDataToUI( (U08*)debugStr );
     }
 #endif