Index: firmware/App/Services/TDInterface.c
===================================================================
diff -u -r2ae6daaf7d4cf33e3e9b1ade40750f3eae04c128 -r145fd716a856f864f39fb0f9884865f6e45b9256
--- firmware/App/Services/TDInterface.c	(.../TDInterface.c)	(revision 2ae6daaf7d4cf33e3e9b1ade40750f3eae04c128)
+++ firmware/App/Services/TDInterface.c	(.../TDInterface.c)	(revision 145fd716a856f864f39fb0f9884865f6e45b9256)
@@ -7,8 +7,8 @@
 *
 * @file    TDInterface.c
 *
-* @author  (last)      Vinayakam Mani
-* @date    (last)      26-Feb-2026
+* @author  (last)      Sameer Kalliadan Poyil
+* @date    (last)      16-Jun-2026
 *
 * @author  (original)  Vinayakam Mani
 * @date    (original)  06-Nov-2024
@@ -20,13 +20,15 @@
 #include "FPOperationModes.h"
 #include "Messaging.h"
 #include "MessagePayloads.h"
+#include "MixingControl.h"
 #include "ModeGenDialysate.h"
 #include "ModeInitPOST.h"
 #include "ModePreGenDialysate.h"
 #include "ModeStandby.h"
 #include "OperationModes.h"
 #include "PersistentAlarm.h"
 #include "SystemCommDD.h"
+#include "SubstitutionPump.h"
 #include "TaskGeneral.h"
 #include "TDInterface.h"
 #include "Timers.h"
@@ -55,6 +57,8 @@
 #define TD_SODIUM_MIN                       ( 130U )                       ///< TD Min acid type index
 #define TD_SODIUM_MAX                       ( 155U )                       ///< TD Max acid type index
 
+
+
 #define TD_BICARBONATE_MIN                  ( 20U )                        ///< TD Min acid type index
 #define TD_BICARBONATE_MAX                  ( 40U )                        ///< TD Max acid type index
 
@@ -82,6 +86,7 @@
    TD_TREATMENT_OVERRIDE_DIALYSATE_TEMP,                                   ///< TD Target Dialysate Temperature
    TD_TREATMENT_OVERRIDE_ACID_TYPE,                                        ///< TD Acid type
    TD_TREATMENT_OVERRIDE_BICARB_TYPE,                                      ///< TD Bicarb type
+   TD_TREATMENT_OVERRIDE_SUB_FLOWRATE,                                     ///< TD Substitution flow rate
    NUM_OF_TD_TREATMENT_OVERRIDES,                                          ///< Number of TD override treatment parameters
 } TD_TREATMENT_OVERRIDE_INDEX_T;
 
@@ -100,6 +105,7 @@
 static OVERRIDE_F32_T tdBicarbConvFactor;                                  ///< TD Bicarb conversion factor
 static OVERRIDE_U32_T tdSodium;                                            ///< TD Sodium concentrate
 static OVERRIDE_U32_T tdBicarbonate;                                       ///< TD Bicarbonate concentrate
+static OVERRIDE_F32_T tdSubstitutionFlowRate;                              ///< TD Subsitution flow rate
 
 // ********** private function prototypes **********
 
@@ -115,46 +121,51 @@
 void initTDInterface( void )
 {
     // Initialize unit state variables
-    tdCurrentOpMode                = MODE_INIT;
-    tdSubMode                      = 0U;
-    tdDialyzerBypass               = FALSE;
-    tdOpModeDataFreshFlag          = FALSE;
+    tdCurrentOpMode                     = MODE_INIT;
+    tdSubMode                           = 0U;
+    tdDialyzerBypass                    = FALSE;
+    tdOpModeDataFreshFlag               = FALSE;
 
     // Initialize treatment parameters from TD
-    tdDialysateFlowrate.data       = 0.0F;
-    tdDialysateFlowrate.ovData     = 0.0F;
-    tdDialysateFlowrate.ovInitData = TD_DIALYSATE_FLOWRATE_MIN_ML_MIN;
-    tdDialysateFlowrate.override   = OVERRIDE_RESET;
+    tdDialysateFlowrate.data            = 0.0F;
+    tdDialysateFlowrate.ovData          = 0.0F;
+    tdDialysateFlowrate.ovInitData      = TD_DIALYSATE_FLOWRATE_MIN_ML_MIN;
+    tdDialysateFlowrate.override        = OVERRIDE_RESET;
 
-    tdUFRate.data                  = 0.0F;
-    tdUFRate.ovData                = 0.0F;
-    tdUFRate.ovInitData            = TD_UF_RATE_MIN_ML_MIN;
-    tdUFRate.override              = OVERRIDE_RESET;
+    tdUFRate.data                       = 0.0F;
+    tdUFRate.ovData                     = 0.0F;
+    tdUFRate.ovInitData                 = TD_UF_RATE_MIN_ML_MIN;
+    tdUFRate.override                   = OVERRIDE_RESET;
 
-    tdDialysateTemp.data           = 0.0F;
-    tdDialysateTemp.ovData         = 0.0F;
-    tdDialysateTemp.ovInitData     = TD_DIALYSATE_TEMP_MIN_DEGC;
-    tdDialysateTemp.override       = OVERRIDE_RESET;
+    tdDialysateTemp.data                = 0.0F;
+    tdDialysateTemp.ovData              = 0.0F;
+    tdDialysateTemp.ovInitData          = TD_DIALYSATE_TEMP_MIN_DEGC;
+    tdDialysateTemp.override            = OVERRIDE_RESET;
 
-    tdAcidConvFactor.data          = 0.0F;
-    tdAcidConvFactor.ovData        = 0.0F;
-    tdAcidConvFactor.ovInitData    = ACID_CONVERSION_FACTOR[ TD_ACID_TYPE_MIN ];
-    tdAcidConvFactor.override      = OVERRIDE_RESET;
+    tdAcidConvFactor.data               = 0.0F;
+    tdAcidConvFactor.ovData             = 0.0F;
+    tdAcidConvFactor.ovInitData         = ACID_CONVERSION_FACTOR[ TD_ACID_TYPE_MIN ];
+    tdAcidConvFactor.override           = OVERRIDE_RESET;
 
-    tdBicarbConvFactor.data        = 0.0F;
-    tdBicarbConvFactor.ovData      = 0.0F;
-    tdBicarbConvFactor.ovInitData  = BICARBONATE_CONVERSION_FACTOR;
-    tdBicarbConvFactor.override    = OVERRIDE_RESET;
+    tdBicarbConvFactor.data             = 0.0F;
+    tdBicarbConvFactor.ovData           = 0.0F;
+    tdBicarbConvFactor.ovInitData       = BICARBONATE_CONVERSION_FACTOR;
+    tdBicarbConvFactor.override         = OVERRIDE_RESET;
 
-    tdSodium.data                  = 0.0F;
-    tdSodium.ovData                = 0.0F;
-    tdSodium.ovInitData            = TD_SODIUM_MIN;
-    tdSodium.override              = OVERRIDE_RESET;
+    tdSodium.data                       = DIALYSATE_TARGET_STD_NA_SETTINGS;
+    tdSodium.ovData                     = 0.0F;
+    tdSodium.ovInitData                 = TD_SODIUM_MIN;
+    tdSodium.override                   = OVERRIDE_RESET;
 
-    tdBicarbonate.data             = 0.0F;
-    tdBicarbonate.ovData           = 0.0F;
-    tdBicarbonate.ovInitData       = TD_BICARBONATE_MIN;
-    tdBicarbonate.override         = OVERRIDE_RESET;
+    tdBicarbonate.data                  = DIALYSATE_TARGET_STD_BICARB_SETTING;
+    tdBicarbonate.ovData                = 0.0F;
+    tdBicarbonate.ovInitData            = TD_BICARBONATE_MIN;
+    tdBicarbonate.override              = OVERRIDE_RESET;
+
+    tdSubstitutionFlowRate.data         = 0.0F;
+    tdSubstitutionFlowRate.ovData       = 0.0F;
+    tdSubstitutionFlowRate.ovInitData   = TD_BICARBONATE_MIN;
+    tdSubstitutionFlowRate.override     = OVERRIDE_RESET;
 }
 
 /**********************************************************************//**
@@ -368,6 +379,18 @@
 
 /*********************************************************************//**
  * @brief
+ * The getTDSubstitutionFlowRate function gets the latest TD
+ * substitution flow rate.
+ * @details \b Inputs: tdSubstitutionFlowRate
+ * @details \b Outputs: none
+ * @return Latest target substitution flow rate
+ *************************************************************************/
+F32 getTDSubstitutionFlowRate( void )
+{
+    return getF32OverrideValue( &tdSubstitutionFlowRate );
+}
+/*********************************************************************//**
+ * @brief
  * The getTDDialyzerBypass function gets the latest TD dailyzer bypass valve
  * enable flag.
  * @details \b Inputs: tdDialyzerBypass
@@ -538,10 +561,12 @@
             setTDUFRate( startTxRequest.ufRate );
             setTDTargetDialysateTemperature( startTxRequest.dialTemp );
 
-            // Set concentrate types, Bypass dialyzer
+            // Set concentrate types, Bypass dialyzer and substitution rate
             setTDAcidAndBicarbType( startTxRequest.acidConvFactor, startTxRequest.bicarbConvFactor,
                                     startTxRequest.sodium, startTxRequest.bicarbonate );
             setTDDialyzerBypass( startTxRequest.bypassDialyzer );
+            tdSubstitutionFlowRate.data = startTxRequest.substitutionRate;
+            setSubstitutionPumpTargetRate( D92_PUMP,  getTDSubstitutionFlowRate() );
 
             // start dialysate generation
             result = requestDDGenDialStart();
@@ -567,10 +592,12 @@
                 setTDUFRate( startTxRequest.ufRate );
                 setTDTargetDialysateTemperature( startTxRequest.dialTemp );
 
-                // Set concentrate types, Bypass dialyzer
+                // Set concentrate types, Bypass dialyzer and substitution rate
                 setTDAcidAndBicarbType( startTxRequest.acidConvFactor, startTxRequest.bicarbConvFactor,
                                         startTxRequest.sodium, startTxRequest.bicarbonate );
                 setTDDialyzerBypass( startTxRequest.bypassDialyzer );
+                tdSubstitutionFlowRate.data = startTxRequest.substitutionRate;
+                setSubstitutionPumpTargetRate( D92_PUMP,  getTDSubstitutionFlowRate() );
 
                 // Signal to update treatement parameters
                 setTreatmentParamUpdate();
@@ -632,6 +659,11 @@
                 result = f32Override( message, &tdBicarbConvFactor);
                 break;
 
+            case TD_TREATMENT_OVERRIDE_SUB_FLOWRATE:
+                result = f32Override( message, &tdSubstitutionFlowRate);
+                setSubstitutionPumpTargetRate( D92_PUMP, getTDSubstitutionFlowRate() );
+                break;
+
             default:
                 result = FALSE;
                 break;