Index: firmware/App/Modes/ModeDrain.c
===================================================================
diff -u -r499e5de29e706d09f79ba22511068990c4044e84 -ra1b8dbb69c4bd2f0cc22e62bede7015c9307d378
--- firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision 499e5de29e706d09f79ba22511068990c4044e84)
+++ firmware/App/Modes/ModeDrain.c	(.../ModeDrain.c)	(revision a1b8dbb69c4bd2f0cc22e62bede7015c9307d378)
@@ -1,64 +1,149 @@
 /**************************************************************************
- *
- *  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 ModeDrain.c
- *
- *  @date 20-Dec-2019
- *  @author L. Baloa
- *
- *  @brief Top-level state machine for the drain 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 ModeDrain.c
+*
+* @author (last) Quang Nguyen
+* @date (last) 24-Aug-2020
+*
+* @author (original) Leonardo Baloa
+* @date (original) 20-Dec-2019
+*
+***************************************************************************/
 
+#include "ConductivitySensors.h"
+#include "DrainPump.h"
 #include "ModeDrain.h"
 #include "OperationModes.h"
+#include "Pressures.h"
+#include "Reservoirs.h"
+#include "ROPump.h"
+#include "TaskGeneral.h"
+#include "TemperatureSensors.h"
+#include "Valves.h"
 
+/**
+ *  @addtogroup DGDrainMode
+ *  @{
+ */
+
+// ********** private definitions **********
+
+#define TARGET_DRAIN_PUMP_RPM           1800                                ///< Target drain pump speed (in RPM).
+#define DRAIN_WEIGH_UNCHANGE_TIMEOUT    ( 2 * MS_PER_SECOND )               ///< Time period of unchanged weight during draining before timeout.
+
+#define TARGET_RO_PRESSURE_PSI          130                                 ///< Target pressure for RO pump.
+#define TARGET_RO_FLOW_RATE_L           0.3                                 ///< Target flow rate for RO pump.
+
 // ********** private data **********
 
+static DG_DRAIN_STATE_T drainState = DG_DRAIN_STATE_START;                  ///< Currently active drain state.
+
 // ********** private function prototypes **********
 
-/*************************************************************************
- * @brief initDrainMode
- * The initOpParamsMode function initializes the Drain Mode module.
- * @details
- * Inputs : none
- * Outputs : Operating Parameters Mode module initialized.
- * @param none
+static DG_DRAIN_STATE_T handleDrainState( void );
+
+/*********************************************************************//**
+ * @brief
+ * The initDrainMode function initializes the drain mode module.
+ * @details Inputs: none
+ * @details Outputs: drainState
  * @return none
  *************************************************************************/
 void initDrainMode( void )
 {
+    drainState = DG_DRAIN_STATE_START;
 }
 
-/*************************************************************************
- * @brief transitionToDrainMode
- * The transitionToDrainMode function prepares for transition to drain \n
- * mode.
- * @details
- * Inputs : none
- * Outputs :
- * @param none
+/*********************************************************************//**
+ * @brief
+ * The transitionToDrainMode function prepares for transition to drain mode.
+ * @details Inputs: none
+ * @details Outputs: Drain mode initialized
  * @return none
  *************************************************************************/
 void transitionToDrainMode( void )
 {
+    // re-initialize each time we transition to drain mode
+    initDrainMode();
+
+    // set initial actuator states
+    setValveState( VDR, VALVE_STATE_DRAIN_C_TO_NO );
+    setDrainPumpTargetRPM( TARGET_DRAIN_PUMP_RPM );
+    setROPumpTargetFlowRate( TARGET_RO_FLOW_RATE_L, TARGET_RO_PRESSURE_PSI );
 }
 
-/*************************************************************************
- * @brief execDrainMode
- * The execDrainMode function executes the Drain Mode state machine.
- * @details
- * Inputs : none
- * Outputs :
- * @param none
- * @return none
+/*********************************************************************//**
+ * @brief
+ * The execDrainMode function executes the drain mode state machine.
+ * @details Inputs: drainState
+ * @details Outputs: Check water quality, drain mode state machine executed
+ * @return current state.
  *************************************************************************/
-void execDrainMode( void )
+U32 execDrainMode( void )
 {
+    // check inlet water conductivity, temperature, pressure, and RO rejection ratio
+    checkInletWaterConductivity();
+    checkInletWaterTemperature();
+    checkInletPressure();
+    checkRORejectionRatio();
 
+    // execute current drain state
+    switch ( drainState )
+    {
+        case DG_DRAIN_STATE_START:
+            drainState = DG_DRAIN_STATE_DRAIN;
+            break;
+
+        case DG_DRAIN_STATE_DRAIN:
+            drainState = handleDrainState();
+            break;
+
+        default:
+            SET_ALARM_WITH_2_U32_DATA( ALARM_ID_DG_SOFTWARE_FAULT, SW_FAULT_ID_DRAIN_MODE_INVALID_EXEC_STATE, drainState )
+            drainState = DG_DRAIN_STATE_START;
+            break;
+    }
+
+    return drainState;
 }
 
+/*********************************************************************//**
+ * @brief
+ * The handleDrainState function handles the drain state  of the drain mode state machine.
+ * @details Inputs: none
+ * @details Outputs: Drain out from reservoir
+ * @return the next state
+ *************************************************************************/
+static DG_DRAIN_STATE_T handleDrainState( void )
+{
+    DG_DRAIN_STATE_T result = DG_DRAIN_STATE_DRAIN;
+    DG_RESERVOIR_ID_T inactiveReservoir = getInactiveReservoir();
+
+    // if we have reached our target drain to volume (by weight) or cannot drain anymore, we are done draining - go back to re-circ mode
+    if ( hasTargetDrainVolumeBeenReached( inactiveReservoir, DRAIN_WEIGH_UNCHANGE_TIMEOUT ) )
+    {
+        setDrainPumpTargetRPM( 0 );
+        requestNewOperationMode( DG_MODE_CIRC );
+    }
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The getCurrentDrainState function returns the current state of the drain mode.
+ * @details Inputs: drainState
+ * @details Outputs: none
+ * @return the current state of drain mode.
+ *************************************************************************/
+DG_DRAIN_STATE_T getCurrentDrainState( void )
+{
+    return drainState;
+}
+
+/**@}*/