Index: firmware/App/Services/Reservoirs.c
===================================================================
diff -u -rdd7fad816b77aee7febdc79785eb74102b844370 -rf401094683b7f3b082c41493f1a217c28a331e5c
--- firmware/App/Services/Reservoirs.c	(.../Reservoirs.c)	(revision dd7fad816b77aee7febdc79785eb74102b844370)
+++ firmware/App/Services/Reservoirs.c	(.../Reservoirs.c)	(revision f401094683b7f3b082c41493f1a217c28a331e5c)
@@ -41,7 +41,7 @@
 #define MAX_FILL_VOLUME_ML              MAX_RESERVOIR_VOLUME_ML                         ///> Maximum fill volume in mL.
 #define DEFAULT_DRAIN_VOLUME_ML         100                                             ///> Default drain volume in mL.
 #define MAX_DRAIN_VOLUME_ML             MAX_RESERVOIR_VOLUME_ML                         ///> Maximum drain volume in mL.
-#define MIN_DRAIN_VOLUME_ML             100                                             ///> Minimum drain volume in mL.
+#define MIN_DRAIN_VOLUME_ML             0                                               ///> Minimum drain volume in mL.
 
 #define MAX_RESERVOIR_WEIGHT            10000                                           ///> Maximum reservoir weight in grams.
 
@@ -111,60 +111,67 @@
 
 /*********************************************************************//**
  * @brief
- * The setActiveReservoir function sets the given reservoir as active
+ * The setActiveReservoirCmd function sets the given reservoir as active
  * (meaning HD will be drawing from this reservoir).
  * @details Inputs: none
  * @details Outputs: Specified reservoir is set as active.
  * @param resID ID of reservoir to set as active
- * @return TRUE if set active reservoir command successful, FALSE if not.
+ * @return none
  *************************************************************************/
-BOOL setActiveReservoirCmd( RESERVOIR_ID_T resID )
-{
-    BOOL result = FALSE;
+void setActiveReservoirCmd( RESERVOIR_ID_T resID )
+{
+    BOOL rejected = TRUE;
+    CMD_REQUEST_REJECT_REASON_CODE_T rejectCode = CMD_REQUEST_REJECT_REASON_NONE;
 
     // switch reservoir command only valid in re-circulate mode
     if ( DG_MODE_CIRC == getCurrentOperationMode() )
     {
         switch ( resID )
         {
             case RESERVOIR_1:
-                activeReservoir.data = (U32)resID;
-                result = TRUE;
+                activeReservoir.data = (U32)resID;
+                rejected = FALSE;
                 setValveState( VRF, VALVE_STATE_R2_C_TO_NO );
                 setValveState( VRD, VALVE_STATE_R2_C_TO_NO );
                 setValveState( VRO, VALVE_STATE_R1_C_TO_NO );
                 setValveState( VRI, VALVE_STATE_R1_C_TO_NO );
                 break;
 
             case RESERVOIR_2:
-                activeReservoir.data = (U32)resID;
-                result = TRUE;
+                activeReservoir.data = (U32)resID;
+                rejected = FALSE;
                 setValveState( VRF, VALVE_STATE_R1_C_TO_NC );       // TODO - valve states are reversed for the two reservoirs for now - revert back when load cells are fixed.
                 setValveState( VRD, VALVE_STATE_R1_C_TO_NC );
                 setValveState( VRO, VALVE_STATE_R2_C_TO_NC );
                 setValveState( VRI, VALVE_STATE_R2_C_TO_NC );
                 break;
 
             default:
-                // invalid reservoir given - cmd will be NAK'd w/ false result.
+                // invalid reservoir given - cmd will be NAK'd w/ false result.
+                rejectCode = CMD_REQUEST_REJECT_REASON_INVALID_PARAMETER;
                 break;
         }
+    }
+    else
+    {
+        rejectCode = CMD_REQUEST_REJECT_REASON_INVALID_MODE;
     }
-
-    return result;
+
+    sendCommandResponseMsg( rejected, rejectCode );
 }
 
 /*********************************************************************//**
  * @brief
- * The startFill function handles a fill command from the HD.
+ * The startFillCmd function handles a fill command from the HD.
  * @details Inputs: none
  * @details Outputs: move to fill mode
  * @param fillToVolMl Target volume (in mL) to fill reservoir to
- * @return TRUE if fill command successful, FALSE if not.
+ * @return none
  *************************************************************************/
-BOOL startFillCmd( U32 fillToVolMl )
+void startFillCmd( U32 fillToVolMl )
 {
-    BOOL result = FALSE;
+    BOOL rejected = TRUE;
+    CMD_REQUEST_REJECT_REASON_CODE_T rejectCode = CMD_REQUEST_REJECT_REASON_NONE;
 
     // fill command only valid in re-circulate mode
     if ( ( DG_MODE_CIRC == getCurrentOperationMode() ) &&
@@ -175,46 +182,60 @@
         {
             fillVolumeTargetMl.data = fillToVolMl;
             requestNewOperationMode( DG_MODE_FILL );
-            result = TRUE;
+            rejected = FALSE;
+        }
+        else
+        {
+            rejectCode = CMD_REQUEST_REJECT_REASON_INVALID_PARAMETER;
         }
+    }
+    else
+    {
+        rejectCode = CMD_REQUEST_REJECT_REASON_INVALID_MODE;
     }
-
-    return result;
+
+    sendCommandResponseMsg( rejected, rejectCode );
 }
 
 /*********************************************************************//**
  * @brief
- * The stopFill function handles a stop fill command from the HD.
+ * The stopFillCmd function handles a stop fill command from the HD.
  * @details Inputs: none
- * @details Outputs: move to standby mode
- * @return TRUE if stop fill command successful, FALSE if not.
+ * @details Outputs: move to re-circulate mode
+ * @return none
  *************************************************************************/
-BOOL stopFillCmd( void )
+void stopFillCmd( void )
 {
-    BOOL result = FALSE;
+    BOOL rejected = TRUE;
+    CMD_REQUEST_REJECT_REASON_CODE_T rejectCode = CMD_REQUEST_REJECT_REASON_NONE;
 
     // stop fill command only valid in fill mode
     if ( DG_MODE_FILL == getCurrentOperationMode() )
     {
         fillVolumeTargetMl.data = 0;
         requestNewOperationMode( DG_MODE_CIRC );
-        result = TRUE;
+        rejected = FALSE;
+    }
+    else
+    {
+        rejectCode = CMD_REQUEST_REJECT_REASON_INVALID_MODE;
     }
 
-    return result;
+    sendCommandResponseMsg( rejected, rejectCode );
 }
 
 /*********************************************************************//**
  * @brief
- * The startDrain function handles a drain command from the HD.
+ * The startDrainCmd function handles a drain command from the HD.
  * @details Inputs: none
  * @details Outputs: Start draining in re-circulate mode
- * @param drainToVolMl Target volume (in mL) to drain reservoir to
- * @return TRUE if drain command successful, FALSE if not.
+ * @param drainCmd drain command data record
+ * @return none
  *************************************************************************/
-BOOL startDrainCmd( DRAIN_CMD_T drainCmd )
+void startDrainCmd( DRAIN_CMD_T drainCmd )
 {
-    BOOL result = FALSE;
+    BOOL rejected = TRUE;
+    CMD_REQUEST_REJECT_REASON_CODE_T rejectCode = CMD_REQUEST_REJECT_REASON_NONE;
 
     // drain command only valid in re-circulate mode
     if ( DG_MODE_CIRC == getCurrentOperationMode() )
@@ -225,67 +246,89 @@
             drainVolumeTargetMl.data = drainCmd.targetVolume;
             tareLoadCellRequest = drainCmd.tareLoadCell;
             requestNewOperationMode( DG_MODE_DRAI );
-            result = TRUE;
+            rejected = FALSE;
+        }
+        else
+        {
+            rejectCode = CMD_REQUEST_REJECT_REASON_INVALID_PARAMETER;
         }
+    }
+    else
+    {
+        rejectCode = CMD_REQUEST_REJECT_REASON_INVALID_MODE;
     }
 
-    return result;
+    sendCommandResponseMsg( rejected, rejectCode );
 }
 
 /*********************************************************************//**
  * @brief
- * The stopDrain function handles a stop drain command from the HD.
+ * The stopDrainCmd function handles a stop drain command from the HD.
  * @details Inputs: none
- * @details Outputs: move to standby mode
- * @return TRUE if stop drain command successful, FALSE if not.
+ * @details Outputs: move to re-circulate mode
+ * @return none
  *************************************************************************/
-BOOL stopDrainCmd( void )
+void stopDrainCmd( void )
 {
-    BOOL result = FALSE;
+    BOOL rejected = TRUE;
+    CMD_REQUEST_REJECT_REASON_CODE_T rejectCode = CMD_REQUEST_REJECT_REASON_NONE;
 
     // stop drain command only valid in drain mode
     if ( DG_MODE_DRAI == getCurrentOperationMode() )
     {
         drainVolumeTargetMl.data = 0;
         requestNewOperationMode( DG_MODE_CIRC );
-        result = TRUE;
+        rejected = FALSE;
     }
+    else
+    {
+        rejectCode = CMD_REQUEST_REJECT_REASON_INVALID_MODE;
+    }
 
-    return result;
+    sendCommandResponseMsg( rejected, rejectCode );
 }
 
 /*********************************************************************//**
  * @brief
- * The startTrimmerHeater function handles a start trimmer heater command
+ * The startTrimmerHeaterCmd function handles a start trimmer heater command
  * from the HD.
  * @details Inputs: none
  * @details Outputs: start trimmer heater
- * @return TRUE if stop drain command successful, FALSE if not.
+ * @return none
  *************************************************************************/
-BOOL startTrimmerHeaterCmd( void )
+void startTrimmerHeaterCmd( void )
 {
-    BOOL result = FALSE;
+    BOOL rejected = TRUE;
+    CMD_REQUEST_REJECT_REASON_CODE_T rejectCode = CMD_REQUEST_REJECT_REASON_NONE;
+
+    if ( TRUE == startTrimmerHeater() )
+    {
+        rejected == FALSE;
+    }
+    else
+    {
+        rejectCode = CMD_REQUEST_REJECT_REASON_INVALID_PARAMETER;
+    }
 
-    result = startTrimmerHeater();
-
-    return result;
+    sendCommandResponseMsg( rejected, rejectCode );
 }
 
 /*********************************************************************//**
  * @brief
- * The stopTrimmerHeater function handles a stop trimmer heater command
+ * The stopTrimmerHeaterCmd function handles a stop trimmer heater command
  * from the HD.
  * @details Inputs: none
  * @details Outputs: stop trimmer heater
- * @return TRUE if stop drain command successful, FALSE if not.
+ * @return none
  *************************************************************************/
-BOOL stopTrimmerHeaterCmd( void )
+void stopTrimmerHeaterCmd( void )
 {
-    BOOL result = TRUE;
+    BOOL rejected = FALSE;
+    CMD_REQUEST_REJECT_REASON_CODE_T rejectCode = CMD_REQUEST_REJECT_REASON_NONE;
 
     stopTrimmerHeater();
 
-    return result;
+    sendCommandResponseMsg( rejected, rejectCode );
 }
 
 /*********************************************************************//**