Index: firmware/App/Modes/ModeStandby.c
===================================================================
diff -u -rf43eb1e9e0803776ec7420b16e1db8760b020bd9 -rc48a99d2d1c852adcc986253b6c420a90dab7bfe
--- firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision f43eb1e9e0803776ec7420b16e1db8760b020bd9)
+++ firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision c48a99d2d1c852adcc986253b6c420a90dab7bfe)
@@ -14,9 +14,11 @@
  *
  **************************************************************************/
 
+#include "CPLD.h"
 #include "OperationModes.h"
+#include "SystemComm.h"
+#include "Timers.h"
 #include "ModeStandby.h"
-#include "CPLD.h"
 
 /**
  *  @addtogroup StandbyMode
@@ -25,57 +27,67 @@
 
 // ********** private definitions **********
 
+#define WATER_SAMPLE_TIME_MS              ( 10 * MS_PER_SECOND )        ///< Duration of water sample state (in ms).
+
 /// Enumeration of standby mode states.
 typedef enum Standby_Mode_States
 {
     STANDBY_MODE_STATE_START = 0,                                       ///< Start standby mode state.
     STANDBY_MODE_STATE_IDLE,                                            ///< Idle standby mode state.
+    STANDBY_MODE_STATE_SAMPLE_WATER,                                    ///< Sample water standby mode state.
     NUM_OF_STANDBY_MODE_STATES                                          ///< Number of standby mode states.
 } STANDBY_MODE_STATE_T;
 
 // ********** private data **********
 
 static STANDBY_MODE_STATE_T standbyState = 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 **********
 
-STANDBY_MODE_STATE_T handleStandbyIdleState( void );
+static STANDBY_MODE_STATE_T handleStandbyIdleState( void );
+static STANDBY_MODE_STATE_T handleStandbySampleWaterState( void );
 
 /*********************************************************************//**
- * @brief initStandbyMode
+ * @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 = 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 )
 {
     // reset to start state each time we transition to standby mode
     standbyState = STANDBY_MODE_STATE_START;
+
+    // TODO - set initial actuator states
 }
 
 /*********************************************************************//**
- * @brief execStandbyMode
+ * @brief
  * The execStandbyMode function executes the Standby Mode state machine.
  * @details
  * Inputs : none
  * Outputs :
- * @param none
  * @return none
  *************************************************************************/
 void execStandbyMode( void )
@@ -91,6 +103,10 @@
             standbyState = handleStandbyIdleState();
             break;
 
+        case STANDBY_MODE_STATE_SAMPLE_WATER:
+            standbyState = handleStandbySampleWaterState();
+            break;
+
         default:
             SET_ALARM_WITH_2_U32_DATA( ALARM_ID_SOFTWARE_FAULT, 0, standbyState )     // TODO - add s/w fault enum to 1st data param
             standbyState = STANDBY_MODE_STATE_START;
@@ -103,24 +119,99 @@
  * 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 STANDBY_MODE_STATE_T handleStandbyIdleState( void )
+{
+    STANDBY_MODE_STATE_T result = 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( MODE_SOLO );
+    }
+    // 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 = STANDBY_MODE_STATE_SAMPLE_WATER;
+    }
+    else if ( TRUE == pendingStartDGRequest )
+    {
+        pendingStartDGRequest = FALSE;
+        requestNewOperationMode( MODE_CIRC );
+    }
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The handleStandbySampleWaterState function executes the sample water state \n
+ * of the Standby Mode state machine.
+ * @details
  * Inputs : none
  * Outputs :
- * @param none
  * @return the next state
  *************************************************************************/
-STANDBY_MODE_STATE_T handleStandbyIdleState( void )
+static STANDBY_MODE_STATE_T handleStandbySampleWaterState( void )
 {
-    STANDBY_MODE_STATE_T result = STANDBY_MODE_STATE_IDLE;
+    STANDBY_MODE_STATE_T result = STANDBY_MODE_STATE_SAMPLE_WATER;
 
-    // go to standby or standby solo mode depending on whether HD is connected
-//    if ( FALSE == isHDCommunicating() )  // TODO - handle switching between standby and standby-solo modes
-//    {
-//        requestNewOperationMode( MODE_SOLO );
-//    }
+    // 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 = STANDBY_MODE_STATE_IDLE;
+    }
 
-    // TODO - what is DG supposed to be doing while in standby mode?
+    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 ( 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 ( STANDBY_MODE_STATE_IDLE == standbyState )
+    {
+        result = TRUE;
+        pendingStartDGRequest = TRUE;
+    }
+
+    return result;
+}
+
 /**@}*/