Index: firmware/App/Modes/ModeStandby.c
===================================================================
diff -u -r484b185f0cf4b2ea0ba9de331573952b1b5124b4 -rb631516f8159c25ba2ffd215afa696795d97a28c
--- firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision 484b185f0cf4b2ea0ba9de331573952b1b5124b4)
+++ firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision b631516f8159c25ba2ffd215afa696795d97a28c)
@@ -19,13 +19,14 @@
 #include "CPLD.h"
 #include "DrainPump.h"
 #include "Heaters.h"
+#include "ModeStandby.h"
 #include "OperationModes.h"
 #include "Reservoirs.h"
 #include "ROPump.h"
 #include "SystemComm.h"
+#include "SystemCommMessages.h"
 #include "Timers.h"
 #include "Valves.h"
-#include "ModeStandby.h"
 
 /**
  *  @addtogroup DGStandbyMode
@@ -34,18 +35,27 @@
 
 // ********** private definitions **********
 
-#define WATER_SAMPLE_TIME_MS              ( 10 * MS_PER_SECOND )            ///< Duration of water sample state (in ms).
+#define FILTER_FLUSH_TIME_MS            ( 120 * MS_PER_SECOND )                 ///< Duration of filter flush state (in ms).
+#define WATER_SAMPLE_TIME_MS            ( 10 * MS_PER_SECOND )                  ///< Duration of water sample state (in ms).
+#define FLUSH_EXPIRATION_TIME_MS        ( 10 * SEC_PER_MIN * MS_PER_SECOND )    ///< Duration in which a filter flush is valid (in ms).
 
 // ********** private data **********
 
 static DG_STANDBY_MODE_STATE_T standbyState = DG_STANDBY_MODE_STATE_START;  ///< Currently active standby state.
-static BOOL pendingSampleWaterRequest = FALSE;                              ///< Flag indicating HD has requested a water sample.
+static BOOL stopSampleWaterRequest = FALSE;                                 ///< Flag indicating HD has requested to stop sample water
+static BOOL startSampleWaterRequest = FALSE;                                ///< Flag indicating HD has requested to start sample water
+static BOOL flushFilterRequest = FALSE;                                     ///< Flag indicating HD has requested to flush filters
+static BOOL endSampleWaterRequest = FALSE;                                  ///< Flag indicating HD has requested to end sample water
+
 static BOOL pendingStartDGRequest = FALSE;                                  ///< Flag indicating HD has requested DG start (go to re-circulate mode).
 static U32 waterSampleStartTime = 0;                                        ///< Time stamp for start of water sample state.
+static U32 filterFlushStartTime = 0;                                        ///< Time stamp for start of filter flush state.
 
 // ********** private function prototypes **********
 
 static DG_STANDBY_MODE_STATE_T handleStandbyIdleState( void );
+static DG_STANDBY_MODE_STATE_T handleStandbyFlushFilterState( void );
+static DG_STANDBY_MODE_STATE_T handleStandbyFlushFilterIdleState( void );
 static DG_STANDBY_MODE_STATE_T handleStandbySampleWaterState( void );
 
 /*********************************************************************//**
@@ -58,9 +68,14 @@
 void initStandbyMode( void )
 {
     standbyState = DG_STANDBY_MODE_STATE_START;
-    pendingSampleWaterRequest = FALSE;
-    pendingStartDGRequest = FALSE;
+    stopSampleWaterRequest = FALSE;
+    startSampleWaterRequest = FALSE;
+    flushFilterRequest = FALSE;
+    endSampleWaterRequest = FALSE;
+
     waterSampleStartTime = 0;
+    filterFlushStartTime = 0;
+    pendingStartDGRequest = FALSE;
 }
 
 /*********************************************************************//**
@@ -113,6 +128,14 @@
             standbyState = handleStandbyIdleState();
             break;
 
+        case DG_STANDBY_MODE_STATE_FLUSH_FILTER:
+            standbyState = handleStandbyFlushFilterState();
+            break;
+
+        case DG_STANDBY_MODE_STATE_FLUSH_FILTER_IDLE:
+            standbyState = handleStandbyFlushFilterIdleState();
+            break;
+
         case DG_STANDBY_MODE_STATE_SAMPLE_WATER:
             standbyState = handleStandbySampleWaterState();
             break;
@@ -136,52 +159,103 @@
  *************************************************************************/
 static DG_STANDBY_MODE_STATE_T handleStandbyIdleState( void )
 {
-    DG_STANDBY_MODE_STATE_T result = DG_STANDBY_MODE_STATE_IDLE;
+    DG_STANDBY_MODE_STATE_T state = DG_STANDBY_MODE_STATE_IDLE;
 
     // go to standby solo mode if HD is turned off or stops communicating.
     if ( FALSE == isHDCommunicating() )
     {   // TODO if HD comm loss, should we wait an hour or so before going to solo standby?
         requestNewOperationMode( DG_MODE_SOLO );
     }
     // if HD requests water sample, go to water sample state
-    else if ( TRUE == pendingSampleWaterRequest )
+    else if ( TRUE == flushFilterRequest )
     {
-        pendingSampleWaterRequest = FALSE;
-        waterSampleStartTime = getMSTimerCount();
+        flushFilterRequest = FALSE;
+        filterFlushStartTime = getMSTimerCount();
         setValveState( VPI, VALVE_STATE_OPEN );
-        setValveState( VSP, VALVE_STATE_OPEN );
-        result = DG_STANDBY_MODE_STATE_SAMPLE_WATER;
+        setValveState( VPD, VALVE_STATE_OPEN );
+        state = DG_STANDBY_MODE_STATE_FLUSH_FILTER;
     }
     else if ( TRUE == pendingStartDGRequest )
     {
         pendingStartDGRequest = FALSE;
         requestNewOperationMode( DG_MODE_CIRC );
     }
 
-    return result;
+    return state;
 }
 
 /*********************************************************************//**
  * @brief
+ * The handleStandbyFilterFlushState function executes the flush filter state
+ * of the standby mode state machine.
+ * @details Inputs: filterFLushStartTime
+ * @details Outputs: Flushed the filters
+ * @return the next state
+ *************************************************************************/
+static DG_STANDBY_MODE_STATE_T handleStandbyFlushFilterState( void )
+{
+    DG_STANDBY_MODE_STATE_T state = DG_STANDBY_MODE_STATE_FLUSH_FILTER;
+
+    if ( TRUE == didTimeout( filterFlushStartTime, FILTER_FLUSH_TIME_MS ) )
+    {
+        state = DG_STANDBY_MODE_STATE_FLUSH_FILTER_IDLE;
+    }
+
+    return state;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The handleStandbyFlushFilterIdleState function executes the flush filter state
+ * of the standby mode state machine.
+ * @details Inputs: filterFLushStartTime
+ * @details Outputs: Flushed the filters
+ * @return the next state
+ *************************************************************************/
+static DG_STANDBY_MODE_STATE_T handleStandbyFlushFilterIdleState( void )
+{
+    DG_STANDBY_MODE_STATE_T state = DG_STANDBY_MODE_STATE_FLUSH_FILTER_IDLE;
+
+    if ( TRUE == startSampleWaterRequest )
+    {
+        startSampleWaterRequest = FALSE;
+        waterSampleStartTime = getMSTimerCount();
+        setValveState( VPI, VALVE_STATE_OPEN );
+        setValveState( VSP, VALVE_STATE_OPEN );
+        state = DG_STANDBY_MODE_STATE_SAMPLE_WATER;
+    }
+
+    if ( TRUE == endSampleWaterRequest )
+    {
+        setValveState( VPI, VALVE_STATE_CLOSED );
+        setValveState( VPD, VALVE_STATE_CLOSED );
+        state = DG_STANDBY_MODE_STATE_IDLE;
+    }
+
+    return state;
+}
+
+/*********************************************************************//**
+ * @brief
  * The handleStandbySampleWaterState function executes the sample water state
  * of the standby mode state machine.
- * @details Inputs: none
- * @details Outputs: Sample water state of the standby mode executed
+ * @details Inputs: stopSampleWaterRequest, waterSampleStartTime
+ * @details Outputs: Finished sample water and closed valve
  * @return the next state
  *************************************************************************/
 static DG_STANDBY_MODE_STATE_T handleStandbySampleWaterState( void )
 {
-    DG_STANDBY_MODE_STATE_T result = DG_STANDBY_MODE_STATE_SAMPLE_WATER;
+    DG_STANDBY_MODE_STATE_T state = DG_STANDBY_MODE_STATE_SAMPLE_WATER;
 
-    // VPi and VSP valves open for 10 seconds, then close and return to idle state
-    if ( TRUE == didTimeout( waterSampleStartTime, WATER_SAMPLE_TIME_MS ) )
+    // After HD requests to stop or 10 seconds has elapsed, close and return to idle state
+    if ( ( TRUE == stopSampleWaterRequest ) || ( TRUE == didTimeout( waterSampleStartTime, WATER_SAMPLE_TIME_MS ) ) )
     {
-        setValveState( VPI, VALVE_STATE_CLOSED );
         setValveState( VSP, VALVE_STATE_CLOSED );
-        result = DG_STANDBY_MODE_STATE_IDLE;
+        setValveState( VPD, VALVE_STATE_OPEN );
+        state = DG_STANDBY_MODE_STATE_FLUSH_FILTER_IDLE;
     }
 
-    return result;
+    return state;
 }
 
 /*********************************************************************//**
@@ -191,17 +265,58 @@
  * @details Outputs: pendingSampleWaterRequest
  * @return TRUE if request accepted, FALSE if not.
  *************************************************************************/
-BOOL requestWaterSample( void )
+void waterSampleCommandHandler( SAMPLE_WATER_CMD_T sampleWaterCmd )
 {
-    BOOL result = FALSE;
+    DG_CMD_RESPONSE_T cmdResponse;
 
-    if ( DG_STANDBY_MODE_STATE_IDLE == standbyState )
+    cmdResponse.commandID = DG_CMD_SAMPLE_WATER;
+    cmdResponse.rejected = TRUE;
+    cmdResponse.rejectCode = DG_CMD_REQUEST_REJECT_REASON_INVALID_MODE;
+
+    switch ( sampleWaterCmd )
     {
-        result = TRUE;
-        pendingSampleWaterRequest = TRUE;
+        case SAMPLE_WATER_CMD_STOP:
+            if ( ( DG_MODE_STAN == getCurrentOperationMode() ) && ( DG_STANDBY_MODE_STATE_SAMPLE_WATER == standbyState ) )
+            {
+                stopSampleWaterRequest = TRUE;
+                cmdResponse.rejected = FALSE;
+                cmdResponse.rejectCode = DG_CMD_REQUEST_REJECT_REASON_NONE;
+            }
+            break;
+
+        case SAMPLE_WATER_CMD_START:
+            if ( ( DG_MODE_STAN == getCurrentOperationMode() ) && ( DG_STANDBY_MODE_STATE_FLUSH_FILTER_IDLE == standbyState ) )
+            {
+                startSampleWaterRequest = TRUE;
+                cmdResponse.rejected = FALSE;
+                cmdResponse.rejectCode = DG_CMD_REQUEST_REJECT_REASON_NONE;
+            }
+            break;
+
+        case SAMPLE_WATER_CMD_FLUSH:
+            if ( ( DG_MODE_STAN == getCurrentOperationMode() ) && ( DG_STANDBY_MODE_STATE_IDLE == standbyState ) )
+            {
+                flushFilterRequest = TRUE;
+                cmdResponse.rejected = FALSE;
+                cmdResponse.rejectCode = DG_CMD_REQUEST_REJECT_REASON_NONE;
+            }
+            break;
+
+        case SAMPLE_WATER_CMD_END:
+            if ( ( DG_MODE_STAN == getCurrentOperationMode() ) && ( DG_STANDBY_MODE_STATE_FLUSH_FILTER_IDLE == standbyState ) )
+            {
+                endSampleWaterRequest = TRUE;
+                cmdResponse.rejected = FALSE;
+                cmdResponse.rejectCode = DG_CMD_REQUEST_REJECT_REASON_NONE;
+            }
+            break;
+
+        default:
+            cmdResponse.rejectCode = DG_CMD_REQUEST_REJECT_REASON_INVALID_PARAMETER;
+            break;
     }
 
-    return result;
+    sendCommandResponseMsg( &cmdResponse );
 }
 
 /*********************************************************************//**