Index: firmware/App/Services/DDInterface.c
===================================================================
diff -u -rf6aa1ffddb85a233371e3e7e4d7c0c0eb3e61493 -r036a75d76ab01912646a480b935d97187a231a19
--- firmware/App/Services/DDInterface.c	(.../DDInterface.c)	(revision f6aa1ffddb85a233371e3e7e4d7c0c0eb3e61493)
+++ firmware/App/Services/DDInterface.c	(.../DDInterface.c)	(revision 036a75d76ab01912646a480b935d97187a231a19)
@@ -43,9 +43,11 @@
 static BOOL ddStartCommandSent;                                             ///< Flag indicates command to start DD has been sent.
 static BOOL ddStarted;                                                      ///< Flag indicates whether we have commanded the DD to start or stop.
 
-static BOOL ddOpModeDataFreshFlag;                                          ///< Flag to signal the handleDDOpMode() to process fresh dd op mode data
+static BOOL ddOpModeDataFreshFlag;                                          ///< Flag to signal the handleDDOpMode() to process fresh dd op mode data.
 static BOOL ddDialysatePressureFreshFlag;                                   ///< Flag to signal
 
+static DIALYSATE_DELIVERY_REQ_PAYLOAD_T dialysateDeliveryCmdSet;            ///< Set of dialysate delivery parameters to send to the DD during treatment.
+
 // DG command response
 static DD_CMD_RESPONSE_T ddCmdResp[ NUM_OF_DD_COMMANDS ];                   ///< Keep the latest DD command response for each command.
 
@@ -66,15 +68,23 @@
     U32 i;
 
     // NOTE: the active reservoir is set to reservoir 1 since DG will send active reservoir 1 as active on power up
-    ddStarted                       = FALSE;
-    ddCurrentOpMode                 = DD_MODE_INIT;
-    ddSubMode                       = 0;
-    dialysatePressure               = 0.0F;
-    ddStartCommandSent              = FALSE;
+    ddStarted                               = FALSE;
+    ddCurrentOpMode                         = DD_MODE_INIT;
+    ddSubMode                               = 0;
+    dialysatePressure                       = 0.0F;
+    ddStartCommandSent                      = FALSE;
 
-    ddOpModeDataFreshFlag           = FALSE;
-    ddDialysatePressureFreshFlag    = FALSE;
+    ddOpModeDataFreshFlag                   = FALSE;
+    ddDialysatePressureFreshFlag            = FALSE;
 
+    dialysateDeliveryCmdSet.start           = FALSE;
+    dialysateDeliveryCmdSet.dialRate        = 0.0F;
+    dialysateDeliveryCmdSet.ufRate          = 0.0F;
+    dialysateDeliveryCmdSet.dialTemp        = 0.0F;
+    dialysateDeliveryCmdSet.bypassDialyzer  = TRUE;
+    dialysateDeliveryCmdSet.acidType        = 0;
+    dialysateDeliveryCmdSet.bicarbType      = 0;
+
     // initialize DD command response
     for ( i = 0; i < NUM_OF_DD_COMMANDS; i++ )
     {
@@ -262,7 +272,7 @@
  * to the DD with a given set of details.  DD will transition to dialysate
  * delivery mode if it hasn't already.
  * @details \b Inputs: none
- * @details \b Outputs: none
+ * @details \b Outputs: dialysateDeliveryCmdSet
  * @details \b Message \b Sent: Start/continue generate dialysate command.
  * @param qd Target dialysate flow rate (Qd).
  * @param quf Target ultrafiltration rate (Quf).
@@ -274,36 +284,102 @@
  *************************************************************************/
 void cmdStartGenerateDialysate( F32 qd, F32 quf, F32 dialTemp, BOOL bypass, ACID_CONCENTRATE_TYPE_T acid, BICARB_CONCENTRATE_TYPE_T bicarb )
 {
-    DIALYSATE_DELIVERY_REQ_PAYLOAD_T payload;
+    dialysateDeliveryCmdSet.start          = TRUE;
+    dialysateDeliveryCmdSet.dialRate       = qd;
+    dialysateDeliveryCmdSet.ufRate         = quf;
+    dialysateDeliveryCmdSet.dialTemp       = dialTemp;
+    dialysateDeliveryCmdSet.bypassDialyzer = bypass;
+    dialysateDeliveryCmdSet.acidType       = (U32)acid;
+    dialysateDeliveryCmdSet.bicarbType     = (U32)bicarb;
 
-    payload.start          = TRUE;
-    payload.dialRate       = qd;
-    payload.ufRate         = quf;
-    payload.dialTemp       = dialTemp;
-    payload.bypassDialyzer = bypass;
-    payload.acidType       = (U32)acid;
-    payload.bicarbType     = (U32)bicarb;
+    sendMessage( MSG_ID_DD_GEN_DIALYSATE_REQUEST_DATA, COMM_BUFFER_OUT_CAN_TD_2_DD, (U08*)(&dialysateDeliveryCmdSet), sizeof( DIALYSATE_DELIVERY_REQ_PAYLOAD_T ) );
+}
 
-    sendMessage( MSG_ID_DD_GEN_DIALYSATE_REQUEST_DATA, COMM_BUFFER_OUT_CAN_TD_2_DD, (U08*)(&payload), sizeof( DIALYSATE_DELIVERY_REQ_PAYLOAD_T ) );
+/*********************************************************************//**
+ * @brief
+ * The cmdChangeQd function sends a generate dialysate command to the DD
+ * with a given new dialysate rate.
+ * @details \b Inputs: none
+ * @details \b Outputs: dialysateDeliveryCmdSet
+ * @details \b Message \b Sent: Continue generate dialysate command w/ new Qd.
+ * @param qd Target dialysate flow rate (Qd).
+ * @return none
+ *************************************************************************/
+void cmdChangeQd( F32 qd )
+{
+    if ( TRUE == dialysateDeliveryCmdSet.start )
+    {
+        dialysateDeliveryCmdSet.dialRate = qd;
+        sendMessage( MSG_ID_DD_GEN_DIALYSATE_REQUEST_DATA, COMM_BUFFER_OUT_CAN_TD_2_DD, (U08*)(&dialysateDeliveryCmdSet), sizeof( DIALYSATE_DELIVERY_REQ_PAYLOAD_T ) );
+    }
+    else
+    {
+        // TODO - s/w fault?
+    }
 }
 
 /*********************************************************************//**
  * @brief
+ * The cmdChangeQuf function sends a generate dialysate command to the DD
+ * with a given new ultrafiltration rate.
+ * @details \b Inputs: none
+ * @details \b Outputs: dialysateDeliveryCmdSet
+ * @details \b Message \b Sent: Continue generate dialysate command w/ new Quf.
+ * @param quf Target ultrafiltration flow rate (in L/hr).
+ * @return none
+ *************************************************************************/
+void cmdChangeQuf( F32 quf )
+{
+    if ( TRUE == dialysateDeliveryCmdSet.start )
+    {
+        dialysateDeliveryCmdSet.ufRate = quf;
+        sendMessage( MSG_ID_DD_GEN_DIALYSATE_REQUEST_DATA, COMM_BUFFER_OUT_CAN_TD_2_DD, (U08*)(&dialysateDeliveryCmdSet), sizeof( DIALYSATE_DELIVERY_REQ_PAYLOAD_T ) );
+    }
+    else
+    {
+        // TODO - s/w fault?
+    }
+}
+
+/*********************************************************************//**
+ * @brief
+ * The cmdBypassDialyzer function sends a generate dialysate command to the DD
+ * with a given flag indicating whether dialyzer should be bypassed.
+ * @details \b Inputs: none
+ * @details \b Outputs: dialysateDeliveryCmdSet
+ * @details \b Message \b Sent: Continue generate dialysate command w/ new
+ * dialyzer bypass flag.
+ * @param bypass Flag indicating whether dialyzer should be bypassed.
+ * @return none
+ *************************************************************************/
+void cmdBypassDialyzer( BOOL bypass )
+{
+    if ( TRUE == dialysateDeliveryCmdSet.start )
+    {
+        dialysateDeliveryCmdSet.bypassDialyzer = bypass;
+        sendMessage( MSG_ID_DD_GEN_DIALYSATE_REQUEST_DATA, COMM_BUFFER_OUT_CAN_TD_2_DD, (U08*)(&dialysateDeliveryCmdSet), sizeof( DIALYSATE_DELIVERY_REQ_PAYLOAD_T ) );
+    }
+    else
+    {
+        // TODO - s/w fault?
+    }
+}
+
+/*********************************************************************//**
+ * @brief
  * The cmdStopGenerateDialysate function sends a stop generate dialysate command
  * to the DD.  DD will transition back to standby mode.
  * @details \b Inputs: none
- * @details \b Outputs: none
+ * @details \b Outputs: dialysateDeliveryCmdSet
  * @details \b Message \b Sent: Stop generate dialysate command.
  * @return none
  *************************************************************************/
 void cmdStopGenerateDialysate( void )
 {
-    DIALYSATE_DELIVERY_REQ_PAYLOAD_T payload;
+    memset( &dialysateDeliveryCmdSet, 0, sizeof( DIALYSATE_DELIVERY_REQ_PAYLOAD_T ) );
+    dialysateDeliveryCmdSet.start = FALSE;
 
-    memset( &payload, 0, sizeof( DIALYSATE_DELIVERY_REQ_PAYLOAD_T ) );
-    payload.start = FALSE;
-
-    sendMessage( MSG_ID_DD_GEN_DIALYSATE_REQUEST_DATA, COMM_BUFFER_OUT_CAN_TD_2_DD, (U08*)(&payload), sizeof( DIALYSATE_DELIVERY_REQ_PAYLOAD_T ) );
+    sendMessage( MSG_ID_DD_GEN_DIALYSATE_REQUEST_DATA, COMM_BUFFER_OUT_CAN_TD_2_DD, (U08*)(&dialysateDeliveryCmdSet), sizeof( DIALYSATE_DELIVERY_REQ_PAYLOAD_T ) );
 }
 
 /**********************************************************************//**