Index: firmware/App/Controllers/DialOutFlow.c
===================================================================
diff -u -r7a754fc23436a42e61e60f66adf1cd0cc8b32ad6 -rc48ea51c06c9d002f1b9b6a1d7b72d69756f183d
--- firmware/App/Controllers/DialOutFlow.c	(.../DialOutFlow.c)	(revision 7a754fc23436a42e61e60f66adf1cd0cc8b32ad6)
+++ firmware/App/Controllers/DialOutFlow.c	(.../DialOutFlow.c)	(revision c48ea51c06c9d002f1b9b6a1d7b72d69756f183d)
@@ -44,16 +44,18 @@
 
 #define MAX_DIAL_OUT_FLOW_RATE                  650             ///< Maximum dialysate outlet pump flow rate in mL/min.
 #define MIN_DIAL_OUT_FLOW_RATE                  100             ///< Minimum dialysate outlet pump flow rate in mL/min.
-#define DPO_FLOW_ADJ_DUE_TO_HIGHER_INLET_PRES   1.200           ///< Adjustment factor to account for higher pump inlet pressure (than DPi pump inlet).
 
 #define MAX_DIAL_OUT_PUMP_PWM_STEP_UP_CHANGE    0.0133          ///< Maximum duty cycle change when ramping up ~ 200 mL/min/s.
 #define MAX_DIAL_OUT_PUMP_PWM_STEP_DN_CHANGE    0.02            ///< Maximum duty cycle change when ramping down ~ 300 mL/min/s.
 #define MAX_DIAL_OUT_PUMP_PWM_DUTY_CYCLE        0.89            ///< Controller will error if PWM duty cycle > 90%, so set max to 89%.
 #define MIN_DIAL_OUT_PUMP_PWM_DUTY_CYCLE        0.10            ///< Controller will error if PWM duty cycle < 10%, so set min to 10%.
+#define MAX_DIAL_OUT_PUMP_PWM_OFFSET_CONTROL    0.4             ///< Maximum PWM offset (added to DPi PWM duty cycle).
+#define MIN_DIAL_OUT_PUMP_PWM_OFFSET_CONTROL   -0.4             ///< Minimum PWM offset (added to DPi PWM duty cycle).
 
+#define DOP_CONTROL_INTERVAL_SEC                5               ///< Dialysate outlet pump control interval (in seconds).
 /// Interval (ms/task time) at which the dialysate outlet pump is controlled.
-static const U32 DOP_CONTROL_INTERVAL         = ( 2000 / TASK_GENERAL_INTERVAL );
-#define DOP_P_COEFFICIENT                       0.0050          ///< P term for dialysate outlet pump control.
+static const U32 DOP_CONTROL_INTERVAL         = ( DOP_CONTROL_INTERVAL_SEC * MS_PER_SECOND / TASK_GENERAL_INTERVAL );
+#define DOP_P_COEFFICIENT                       0.0010          ///< P term for dialysate outlet pump control.
 #define DOP_I_COEFFICIENT                       0.0001          ///< I term for dialysate outlet pump control.
 
 #define DOP_HOME_RATE                           100             ///< Target pump speed (in estimate mL/min) for homing.
@@ -217,9 +219,8 @@
     }
 
     // Initialize dialysate outlet flow PI controller
-    initializePIController( PI_CONTROLLER_ID_ULTRAFILTRATION, MIN_DIAL_OUT_PUMP_PWM_DUTY_CYCLE,
-                            DOP_P_COEFFICIENT, DOP_I_COEFFICIENT,
-                            MIN_DIAL_OUT_PUMP_PWM_DUTY_CYCLE, MAX_DIAL_OUT_PUMP_PWM_DUTY_CYCLE );
+    initializePIController( PI_CONTROLLER_ID_ULTRAFILTRATION, 0, DOP_P_COEFFICIENT, DOP_I_COEFFICIENT,
+                            MIN_DIAL_OUT_PUMP_PWM_OFFSET_CONTROL, MAX_DIAL_OUT_PUMP_PWM_OFFSET_CONTROL );
 }
 
 /*********************************************************************//**
@@ -247,10 +248,6 @@
         {
             F32 adjFlow = (F32)flowRate;
 
-            if ( PUMP_CONTROL_MODE_CLOSED_LOOP == mode )
-            {
-                adjFlow *= DPO_FLOW_ADJ_DUE_TO_HIGHER_INLET_PRES;
-            }
             lastGivenRate = flowRate;
             dialOutPumpDirection = dir;
             dialOutPumpControlMode = mode;
@@ -518,14 +515,18 @@
     // Have we reached end of ramp up?
     else if ( dialOutPumpPWMDutyCyclePctSet >= dialOutPumpPWMDutyCyclePct )
     {
-        resetPIController( PI_CONTROLLER_ID_ULTRAFILTRATION, dialOutPumpPWMDutyCyclePctSet );
-        dialOutPumpControlModeSet = dialOutPumpControlMode;
-        // If open loop mode, set PWM to requested duty cycle where it will stay during control state
+        dialOutPumpPWMDutyCyclePctSet = dialOutPumpPWMDutyCyclePct;
         if ( dialOutPumpControlModeSet == PUMP_CONTROL_MODE_OPEN_LOOP )
         {
-            dialOutPumpPWMDutyCyclePctSet = dialOutPumpPWMDutyCyclePct;
-            setDialOutPumpControlSignalPWM( dialOutPumpPWMDutyCyclePct );
+            resetPIController( PI_CONTROLLER_ID_ULTRAFILTRATION, dialOutPumpPWMDutyCyclePctSet );
         }
+        else
+        {   // Closed loop UF control is only controlling offset from DPi PWM
+            resetPIController( PI_CONTROLLER_ID_ULTRAFILTRATION, dialOutPumpPWMDutyCyclePctSet - getDialInPumpPWMDutyCyclePct() );
+        }
+        dialOutPumpControlModeSet = dialOutPumpControlMode;
+        setDialOutPumpControlSignalPWM( dialOutPumpPWMDutyCyclePct );
+        dopControlTimerCounter = 0;
         result = DIAL_OUT_PUMP_CONTROL_TO_TARGET_STATE;
     }
     // Continue ramp up
@@ -559,14 +560,18 @@
     // Have we reached end of ramp down?
     else if ( dialOutPumpPWMDutyCyclePctSet <= dialOutPumpPWMDutyCyclePct )
     {
-        resetPIController( PI_CONTROLLER_ID_ULTRAFILTRATION, dialOutPumpPWMDutyCyclePctSet );
-        dialOutPumpControlModeSet = dialOutPumpControlMode;
-        // If open loop mode, set PWM to requested duty cycle where it will stay during control state
-        if ( dialOutPumpControlModeSet == PUMP_CONTROL_MODE_OPEN_LOOP )
+        dialOutPumpPWMDutyCyclePctSet = dialOutPumpPWMDutyCyclePct;
+        if ( ( dialOutPumpControlModeSet == PUMP_CONTROL_MODE_OPEN_LOOP ) || ( 0 == lastGivenRate ) )
         {
-            dialOutPumpPWMDutyCyclePctSet = dialOutPumpPWMDutyCyclePct;
-            setDialOutPumpControlSignalPWM( dialOutPumpPWMDutyCyclePct );
+            resetPIController( PI_CONTROLLER_ID_ULTRAFILTRATION, dialOutPumpPWMDutyCyclePctSet );
         }
+        else
+        {   // Closed loop UF control is only controlling offset from DPi PWM
+            resetPIController( PI_CONTROLLER_ID_ULTRAFILTRATION, dialOutPumpPWMDutyCyclePctSet - getDialInPumpPWMDutyCyclePct() );
+        }
+        dialOutPumpControlModeSet = dialOutPumpControlMode;
+        setDialOutPumpControlSignalPWM( dialOutPumpPWMDutyCyclePct );
+        dopControlTimerCounter = 0;
         result = DIAL_OUT_PUMP_CONTROL_TO_TARGET_STATE;
     }
     // Continue ramp down
@@ -598,22 +603,17 @@
         {
             F32 refVol = getTotalTargetDialOutUFVolumeInMl();
             F32 totVol = getTotalMeasuredUFVolumeInMl();
-            F32 newPWMDutyCyclePct;
-            F32 deltaPWMDutyCyclePct;
+            F32 offsetPWMDutyCyclePct;
 
-            // Get new PWM from PI controller
-            newPWMDutyCyclePct = runPIController( PI_CONTROLLER_ID_ULTRAFILTRATION, refVol, totVol );
-            // Limit PWM change to max
-            deltaPWMDutyCyclePct = newPWMDutyCyclePct - dialOutPumpPWMDutyCyclePctSet;
-            if ( fabs( deltaPWMDutyCyclePct ) > MAX_DIAL_OUT_PUMP_PWM_STEP_UP_CHANGE )
-            {
-                newPWMDutyCyclePct = ( deltaPWMDutyCyclePct < 0.0 ? \
-                                       dialOutPumpPWMDutyCyclePctSet - MAX_DIAL_OUT_PUMP_PWM_STEP_UP_CHANGE : \
-                                       dialOutPumpPWMDutyCyclePctSet + MAX_DIAL_OUT_PUMP_PWM_STEP_UP_CHANGE );
-            }
-            // Set new PWM
-            dialOutPumpPWMDutyCyclePctSet = newPWMDutyCyclePct;
-            setDialOutPumpControlSignalPWM( newPWMDutyCyclePct );
+            // Get new PWM offset from PI controller
+            offsetPWMDutyCyclePct = runPIController( PI_CONTROLLER_ID_ULTRAFILTRATION, refVol, totVol );
+            // Add PWM offset to DPi PWM mirror for our new DPo PWM
+            dialOutPumpPWMDutyCyclePctSet = getDialInPumpPWMDutyCyclePct() + offsetPWMDutyCyclePct;
+            // Limit PWM range
+            dialOutPumpPWMDutyCyclePctSet = MIN( dialOutPumpPWMDutyCyclePctSet, MAX_DIAL_OUT_PUMP_PWM_DUTY_CYCLE );
+            dialOutPumpPWMDutyCyclePctSet = MAX( dialOutPumpPWMDutyCyclePctSet, MIN_DIAL_OUT_PUMP_PWM_DUTY_CYCLE );
+            // Apply new PWM to DPo pump
+            setDialOutPumpControlSignalPWM( dialOutPumpPWMDutyCyclePctSet );
         }
         dopControlTimerCounter = 0;
     }