Index: firmware/App/Modes/ModeStandby.c
===================================================================
diff -u -r499e5de29e706d09f79ba22511068990c4044e84 -r0dec8744af40d0c87a6d7cd1923920c1c2bd1d2f
--- firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision 499e5de29e706d09f79ba22511068990c4044e84)
+++ firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision 0dec8744af40d0c87a6d7cd1923920c1c2bd1d2f)
@@ -1,64 +1,240 @@
 /**************************************************************************
- *
- *  Copyright (c) 2019-2020 Diality Inc. - All Rights Reserved.
- *
- *  THIS CODE MAY NOT BE COPIED OR REPRODUCED IN ANY FORM, IN PART OR IN
- *  WHOLE, WITHOUT THE EXPLICIT PERMISSION OF THE COPYRIGHT OWNER.
- *
- *  @file ModeStandby.c
- *
- *  @date 11-Dec-2019
- *  @author L. Baloa
- *
- *  @brief Top-level state machine for the standby mode.
- *
- **************************************************************************/
+*
+* Copyright (c) 2019-2020 Diality Inc. - All Rights Reserved.
+*
+* THIS CODE MAY NOT BE COPIED OR REPRODUCED IN ANY FORM, IN PART OR IN
+* WHOLE, WITHOUT THE EXPLICIT PERMISSION OF THE COPYRIGHT OWNER.
+*
+* @file ModeStandby.c
+*
+* @author (last) Quang Nguyen
+* @date (last) 21-Jul-2020
+*
+* @author (original) Dara Navaei
+* @date (original) 05-Nov-2019
+*
+***************************************************************************/
 
+#include "CPLD.h"
+#include "DrainPump.h"
+#include "Heaters.h"
 #include "OperationModes.h"
+#include "ROPump.h"
+#include "SystemComm.h"
+#include "Timers.h"
+#include "Valves.h"
 #include "ModeStandby.h"
-#include "CPLD.h"
 
+/**
+ *  @addtogroup DGStandbyMode
+ *  @{
+ */
+
+// ********** private definitions **********
+
+#define WATER_SAMPLE_TIME_MS              ( 10 * MS_PER_SECOND )        ///< Duration of water sample state (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 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.
+
 // ********** private function prototypes **********
 
-/*************************************************************************
- * @brief initStandbyMode
+static DG_STANDBY_MODE_STATE_T handleStandbyIdleState( void );
+static DG_STANDBY_MODE_STATE_T handleStandbySampleWaterState( void );
+
+/*********************************************************************//**
+ * @brief
  * The initStandbyMode function initializes the Standby Mode module.
  * @details
  * Inputs : none
  * Outputs : Standby Mode module initialized.
- * @param none
  * @return none
  *************************************************************************/
 void initStandbyMode( void )
 {
+    standbyState = DG_STANDBY_MODE_STATE_START;
+    pendingSampleWaterRequest = FALSE;
+    pendingStartDGRequest = FALSE;
+    waterSampleStartTime = 0;
 }
 
-/*************************************************************************
- * @brief transitionToStandbyMode
+/*********************************************************************//**
+ * @brief
  * The transitionToStandbyMode function prepares for transition to standby mode.
  * @details
  * Inputs : none
  * Outputs :
- * @param none
  * @return none
  *************************************************************************/
 void transitionToStandbyMode( void )
 {
+    // re-initialize standby mode each time we transition to standby mode
+    initStandbyMode();
+
+    // set initial actuator states
+    setValveState( VPI, VALVE_STATE_CLOSED );
+    setValveState( VSP, VALVE_STATE_CLOSED );
+    setValveState( VRC, VALVE_STATE_DRAIN_C_TO_NO );
+    setValveState( VDR, VALVE_STATE_DRAIN_C_TO_NO );
+    setValveState( VPO, VALVE_STATE_NOFILL_C_TO_NO );
+    signalROPumpHardStop();
+    signalDrainPumpHardStop();
+    stopPrimaryHeater();
+    stopTrimmerHeater();
+    // conc. pumps off
+    // UV off
 }
 
-/*************************************************************************
- * @brief execStandbyMode
+/*********************************************************************//**
+ * @brief
  * The execStandbyMode function executes the Standby Mode state machine.
  * @details
  * Inputs : none
  * Outputs :
- * @param none
- * @return none
+ * @return current state.
  *************************************************************************/
-void execStandbyMode( void )
+U32 execStandbyMode( void )
 {
+    // execute current Standby state
+    switch ( standbyState )
+    {
+        case DG_STANDBY_MODE_STATE_START:
+            standbyState = DG_STANDBY_MODE_STATE_IDLE;
+            break;
 
+        case DG_STANDBY_MODE_STATE_IDLE:
+            standbyState = handleStandbyIdleState();
+            break;
+
+        case DG_STANDBY_MODE_STATE_SAMPLE_WATER:
+            standbyState = handleStandbySampleWaterState();
+            break;
+
+        default:
+            SET_ALARM_WITH_2_U32_DATA( ALARM_ID_DG_SOFTWARE_FAULT, 0, standbyState )     // TODO - add s/w fault enum to 1st data param
+            standbyState = DG_STANDBY_MODE_STATE_START;
+            break;
+    }
+
+    return standbyState;
 }
 
+/*********************************************************************//**
+ * @brief
+ * The handleStandbyIdleState function executes the Idle state of the \n
+ * Standby Mode state machine.
+ * @details
+ * Inputs : pendingSampleWaterRequest, pendingStartDGRequest
+ * Outputs : possibly op mode
+ * @return the next state
+ *************************************************************************/
+static DG_STANDBY_MODE_STATE_T handleStandbyIdleState( void )
+{
+    DG_STANDBY_MODE_STATE_T result = 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 );  // TODO - uncomment when solo mode is implemented.
+    }
+    // if HD requests water sample, go to water sample state
+    else if ( TRUE == pendingSampleWaterRequest )
+    {
+        pendingSampleWaterRequest = FALSE;
+        waterSampleStartTime = getMSTimerCount();
+        // TODO - open VPi and VSP valves
+        result = DG_STANDBY_MODE_STATE_SAMPLE_WATER;
+    }
+    else if ( TRUE == pendingStartDGRequest )
+    {
+        pendingStartDGRequest = FALSE;
+        requestNewOperationMode( DG_MODE_CIRC );
+    }
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The handleStandbySampleWaterState function executes the sample water state \n
+ * of the Standby Mode state machine.
+ * @details
+ * Inputs : none
+ * Outputs :
+ * @return the next state
+ *************************************************************************/
+static DG_STANDBY_MODE_STATE_T handleStandbySampleWaterState( void )
+{
+    DG_STANDBY_MODE_STATE_T result = 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 ) )
+    {
+        // TODO - close VPi and VSP valves.
+        result = DG_STANDBY_MODE_STATE_IDLE;
+    }
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The requestWaterSample function handles an HD request to sample water.
+ * @details
+ * Inputs : standbyState
+ * Outputs : pendingSampleWaterRequest
+ * @return TRUE if request accepted, FALSE if not.
+ *************************************************************************/
+BOOL requestWaterSample( void )
+{
+    BOOL result = FALSE;
+
+    if ( DG_STANDBY_MODE_STATE_IDLE == standbyState )
+    {
+        result = TRUE;
+        pendingSampleWaterRequest = TRUE;
+    }
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The requestDGStart function handles an HD request to start (go to re-circulate mode).
+ * @details
+ * Inputs : standbyState
+ * Outputs : pendingSampleWaterRequest
+ * @return TRUE if request accepted, FALSE if not.
+ *************************************************************************/
+BOOL requestDGStart( void )
+{
+    BOOL result = FALSE;
+
+    if ( DG_STANDBY_MODE_STATE_IDLE == standbyState )
+    {
+        result = TRUE;
+        pendingStartDGRequest = TRUE;
+    }
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The getCurrentStandbyState function returns the current state of the \n
+ * standby mode.
+ * @details
+ * Inputs : standbyState
+ * Outputs : none
+ * @return the current state of standby mode.
+ *************************************************************************/
+DG_STANDBY_MODE_STATE_T getCurrentStandbyState( void )
+{
+    return standbyState;
+}
+
+/**@}*/