Index: firmware/App/Modes/ModePreTreat.c
===================================================================
diff -u -r83310420ae862de4724f8cfbbaeda9936c47801b -r5366722d2325ea93db0ad1f696db78597af3b7c6
--- firmware/App/Modes/ModePreTreat.c	(.../ModePreTreat.c)	(revision 83310420ae862de4724f8cfbbaeda9936c47801b)
+++ firmware/App/Modes/ModePreTreat.c	(.../ModePreTreat.c)	(revision 5366722d2325ea93db0ad1f696db78597af3b7c6)
@@ -20,6 +20,7 @@
 #include "BloodFlow.h"
 #include "Buttons.h"
 #include "DDInterface.h"
+#include "Messaging.h"
 #include "ModePreTreat.h"
 #include "OperationModes.h"
 #include "StatePreTxRecirculate.h"
@@ -40,7 +41,9 @@
 static TD_PRE_TREATMENT_MODE_STATE_T currentPreTreatmentState;              ///< Current Pre-Treatment sub-state
 static BOOL goToInstallStateRequested;                                      ///< Flag indicating a request to transition to Install state.
 static BOOL continueFromRecirculateRequested;                               ///< Flag indicating a request to transition to Patient Connection state.
+static BOOL treatmentStartRequested;                                        ///< Flag indicating the UI requested treatment start.
 
+
 // ********** private function prototypes **********
 
 static void setPreTreatStateTransition( void );                                 ///< Configure actuators and variables for Pre-Treatment state transitions.
@@ -66,6 +69,7 @@
     currentPreTreatmentState  = TD_PRE_TREATMENT_TUBING_SET_INSTALL_STATE;
     goToInstallStateRequested = FALSE;
     continueFromRecirculateRequested = FALSE;
+    treatmentStartRequested = FALSE;
 }
 
 /*********************************************************************//**
@@ -136,7 +140,7 @@
             break;
 
         case TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE:
-            // currentPreTreatmentState = handlePatientConnectionState();
+            currentPreTreatmentState = handlePatientConnectionState();
             break;
 
         default:
@@ -191,7 +195,17 @@
             break;
 
         case TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE:
-            // TODO: actuator configuration
+            signalBloodPumpHardStop();
+            setValvePosition( H1_VALV, VALVE_POSITION_B_OPEN );
+            setValvePosition( H19_VALV, VALVE_POSITION_C_CLOSE );
+            setAirPumpState( AIR_PUMP_STATE_OFF, AIR_PUMP_MOTOR_OFF );
+            set3WayValveState( H13_VALV, VALVE_3WAY_COMMON_TO_CLOSED_STATE );
+            set3WayValveState( H20_VALV, VALVE_3WAY_COMMON_TO_CLOSED_STATE );
+            stopSyringePump();
+
+            // TODO: Set H5 ejector Off.
+            // TODO: Command DD to bypass dialyzer, set QDt to prescribed rate,
+            //       Quf to 0, and Qs to 0.
             break;
 
         default:
@@ -284,12 +298,7 @@
     if ( TRUE == continueFromRecirculateRequested )
     {
         continueFromRecirculateRequested = FALSE;
-
-        // TODO: Change to TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE
-        // when Patient Connection state is implemented.
-        // state = TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE;
-
-        requestNewOperationMode( MODE_TREA );
+        state = TD_PRE_TREATMENT_CONFIRM_RX_STATE;
     }
 
     return state;
@@ -332,7 +341,7 @@
                                        getTreatmentParameterU32( TREATMENT_PARAM_BICARBONATE ) );
         }
 
-        state = TD_PRE_TREATMENT_RECIRCULATE_STATE;
+        state = TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE;
    }
 
    return state;
@@ -341,19 +350,23 @@
 /*********************************************************************//**
  * @brief
  * The handlePatientConnectionState function executes the Patient
- * Connection state of pre-treatment mode.
- * @details \b Inputs: TODO fill up if any
- * @details \b Outputs: TODO fill up if any
- * @return next Pre-Treatment mode state.
+ * Connection pre-treatment step.
+ * @details \b Inputs: treatmentStartRequested.
+ * @details \b Outputs: Requests transition to Treatment Mode when the
+ * UI Start Treatment request is received.
+ * @return current Pre-Treatment mode state.
  *************************************************************************/
 static TD_PRE_TREATMENT_MODE_STATE_T handlePatientConnectionState( void )
 {
-    TD_PRE_TREATMENT_MODE_STATE_T state = TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE;
+    TD_PRE_TREATMENT_MODE_STATE_T state =
+        TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE;
 
-    // TODO : after implementing this state, place the transition in the right place
+    if ( TRUE == treatmentStartRequested )
+    {
+        treatmentStartRequested = FALSE;
+        requestNewOperationMode( MODE_TREA );
+    }
 
-    //requestNewOperationMode( MODE_TREA );
-
     return state;
 }
 
@@ -385,6 +398,63 @@
 
 /*********************************************************************//**
  * @brief
+ * The handleStartTreatmentRequest function handles the UI request to
+ * start treatment.
+ * @details \b Inputs: current operation mode and Pre-Treatment state.
+ * @details \b Outputs: treatmentStartRequested.
+ * @param message Pointer to the received Start Treatment request message.
+ * @return TRUE if the request was accepted, otherwise FALSE.
+ *************************************************************************/
+BOOL handleStartTreatmentRequest( MESSAGE_T *message )
+{
+    TD_OP_MODE_T mode = getCurrentOperationMode();
+    TD_PRE_TREATMENT_MODE_STATE_T preTxState = currentPreTreatmentState;
+    U32 payloadLen = message->hdr.payloadLen;
+    BOOL accepted = FALSE;
+    UI_RESPONSE_PAYLOAD_T response;
+
+    response.accepted = FALSE;
+    response.rejectionReason = REQUEST_REJECT_REASON_ACTION_DISABLED_IN_CURRENT_STATE;
+
+    if ( ( 0U == payloadLen ) && ( MODE_PRET == mode ) && ( TD_PRE_TREATMENT_PATIENT_CONNECTION_STATE == preTxState ) )
+    {
+        treatmentStartRequested = TRUE;
+        accepted = TRUE;
+        response.accepted = TRUE;
+        response.rejectionReason = REQUEST_REJECT_REASON_NONE;
+    }
+
+    sendMessage( MSG_ID_TD_START_TREATMENT_RESPONSE, COMM_BUFFER_OUT_CAN_TD_2_UI, (U08 *)&response, sizeof( UI_RESPONSE_PAYLOAD_T ) );
+
+    return accepted;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The signalPreTreatmentBackoutToStandby function handles a request to
+ * back out of Pre-Treatment to Standby.
+ * @details \b Inputs: current operation mode, current Pre-Treatment state,
+ * and Tube Set Install state.
+ * @details \b Outputs: Requests Standby Mode when backout is allowed.
+ * @return TRUE if the request is accepted, otherwise FALSE.
+ *************************************************************************/
+BOOL signalPreTreatmentBackoutToStandby( void )
+{
+    BOOL accepted = FALSE;
+
+    if ( ( MODE_PRET == getCurrentOperationMode() ) &&
+         ( TD_PRE_TREATMENT_TUBING_SET_INSTALL_STATE == currentPreTreatmentState ) &&
+         ( TRUE == isTubeSetInstallAwaitingConfirmation() ) )
+    {
+        requestNewOperationMode( MODE_STAN );
+        accepted = TRUE;
+    }
+
+    return accepted;
+}
+
+/*********************************************************************//**
+ * @brief
  * The signalAlarmActionToPreTreatmentMode function executes the given alarm action
  * as appropriate while in Pre-Treatment Mode.
  * @details \b Inputs: currentPreTreatmentState