Index: firmware/App/Services/SystemCommMessages.c
===================================================================
diff -u -r9d7ad180a18e29ba08bf65228d61b6179ddbfcca -rd3ae2d91603ae6d2d25b9abdb220cc144cf90692
--- firmware/App/Services/SystemCommMessages.c	(.../SystemCommMessages.c)	(revision 9d7ad180a18e29ba08bf65228d61b6179ddbfcca)
+++ firmware/App/Services/SystemCommMessages.c	(.../SystemCommMessages.c)	(revision d3ae2d91603ae6d2d25b9abdb220cc144cf90692)
@@ -120,6 +120,7 @@
 
 static U32 serializeMessage( MESSAGE_T msg, COMM_BUFFER_T buffer, BOOL ackReq );
 static BOOL sendTestAckResponseMsg( MSG_ID_T msgID, BOOL ack );
+static BOOL sendAckResponseMsg( MSG_ID_T msgID, COMM_BUFFER_T buffer, BOOL ack );
 
 /*************************************************************************
  * @brief serializeMessage
@@ -234,6 +235,36 @@
     return result;
 }
 
+/*************************************************************************
+ * @brief sendTestAckResponseMsg
+ * The sendTestAckResponseMsg function constructs a simple response \n
+ * message for a handled test message and queues it for transmit on the \n
+ * appropriate UART channel.
+ * @details
+ * Inputs : none
+ * Outputs : response message constructed and queued for transmit.
+ * @param msgID : ID of handled message that we are responding to
+ * @param buffer : outgoing buffer that message should be queued in
+ * @param ack : TRUE if test message was handled successfully, FALSE if not
+ * @return TRUE if response message successfully queued for transmit, FALSE if not
+ *************************************************************************/
+static BOOL sendAckResponseMsg( MSG_ID_T msgID, COMM_BUFFER_T buffer, BOOL ack )
+{
+    BOOL result;
+    MESSAGE_T msg;
+
+    // create a message record
+    blankMessage( &msg );
+    msg.hdr.msgID = msgID;
+    msg.hdr.payloadLen = sizeof( U08 );
+    msg.payload[ 0 ] = (U08)ack;
+
+    // serialize the message (w/ sync, CRC, and appropriate CAN padding) and add serialized message data to appropriate comm buffer
+    result = serializeMessage( msg, buffer, ACK_NOT_REQUIRED );
+
+    return result;
+}
+
 // ***********************************************************************
 // ********************* MSG_ID_OFF_BUTTON_PRESS *************************
 // ***********************************************************************
@@ -336,7 +367,7 @@
         memcpy( &payload, message->payload, sizeof(LOAD_CELL_READINGS_PAYLOAD_T) );
         result = setNewLoadCellReadings( payload.res1PrimaryLoadCell, payload.res1BackupLoadCell, payload.res2PrimaryLoadCell, payload.res2BackupLoadCell );
     }
-    sendTestAckResponseMsg( (MSG_ID_T)message->hdr.msgID, result );
+    // TODO - what to do if invalid payload length?
 }
 
 /*************************************************************************
@@ -367,7 +398,7 @@
             result = resumeUF();
         }
     }
-    sendTestAckResponseMsg( (MSG_ID_T)message->hdr.msgID, result );
+    sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, result );
 }
 
 /*************************************************************************
@@ -392,7 +423,7 @@
 
         result = verifyUFSettingsChange( payload.volume_mL, payload.adjustType );
     }
-    sendTestAckResponseMsg( (MSG_ID_T)message->hdr.msgID, result );
+    sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, result );
 }
 
 /*************************************************************************
@@ -411,7 +442,7 @@
  * @param rateDiff : alarm status record
  * @return TRUE if msg successfully queued for transmit, FALSE if not
  *************************************************************************/
-BOOL sendChangeUFSettingsResponse( BOOL accepted, F32 volume_mL, U32 time_min, F32 ufRate_mL_min, U32 timeDiff, F32 rateDiff )
+BOOL sendChangeUFSettingsResponse( BOOL accepted, F32 volume_mL, U32 time_min, F32 ufRate_mL_min, S32 timeDiff, F32 rateDiff )
 {
     BOOL result;
     F32 volume_L = volume_mL / (F32)ML_PER_LITER;
@@ -463,7 +494,7 @@
 
         result = verifyUFSettingsConfirmation( payload.confirmed, payload.volume_mL, payload.treatTime_min, payload.uFRate_mL_min );
     }
-    sendTestAckResponseMsg( (MSG_ID_T)message->hdr.msgID, result );
+    sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, result );
 }
 
 /*************************************************************************
@@ -488,7 +519,7 @@
 
         result = verifyTreatmentDurationSettingChange( timeInMin );
     }
-    sendTestAckResponseMsg( (MSG_ID_T)message->hdr.msgID, result );
+    sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, result );
 }
 
 /*************************************************************************
@@ -1349,13 +1380,10 @@
     U08 days    = message->payload[3];
     U08 months  = message->payload[4];
     U32 years;
+
     memcpy(&years, &message->payload[5], sizeof(U32));
+    result = setRTCTimestamp( seconds, minutes, hours, days, months, years );
 
-    // TODO: Change setRTCTimestamp to return a boolean for this
-    result = TRUE;
-
-    setRTCTimestamp( seconds, minutes, hours, days, months, years );
-
     // respond to request
     sendTestAckResponseMsg( (MSG_ID_T)message->hdr.msgID, result );
 }