Index: firmware/App/Controllers/BloodFlow.c
===================================================================
diff -u -r70d33c50c8c3fd987f39eaa1f3b294860d569830 -r2bdd010a62ea113058640fc1e9c763dcf885c93c
--- firmware/App/Controllers/BloodFlow.c	(.../BloodFlow.c)	(revision 70d33c50c8c3fd987f39eaa1f3b294860d569830)
+++ firmware/App/Controllers/BloodFlow.c	(.../BloodFlow.c)	(revision 2bdd010a62ea113058640fc1e9c763dcf885c93c)
@@ -937,25 +937,33 @@
     if ( ++bpMotorSpeedCalcTimerCtr >= BP_SPEED_CALC_INTERVAL )
     {
         U16 bpMotorHallSensorCount = getFPGABloodPumpHallSensorCount();
+        U16 last = bpLastMotorHallSensorCounts[ bpMotorSpeedCalcIdx ];
         U32 nextIdx = INC_WRAP( bpMotorSpeedCalcIdx, 0, BP_SPEED_CALC_BUFFER_LEN - 1 );
         U16 incDelta = ( bpMotorHallSensorCount >= bpLastMotorHallSensorCounts[ nextIdx ] ? \
                          bpMotorHallSensorCount - bpLastMotorHallSensorCounts[ nextIdx ] : \
                          ( HEX_64_K - bpLastMotorHallSensorCounts[ nextIdx ] ) + bpMotorHallSensorCount );
         U16 decDelta = HEX_64_K - incDelta;
-        U16 delta;
-
+        U16 spdDelta;
+        U16 delta;
+
+        // Keep a running 32-bit edge count used for safety check on volume in some functions
+        bloodPumpMotorEdgeCount += delta;
+
         // Determine blood pump speed/direction from delta hall sensor count since last interval
         if ( incDelta < decDelta )
         {
-            delta = incDelta;
-            bloodPumpSpeedRPM.data = ( (F32)delta / (F32)BP_HALL_EDGE_COUNTS_PER_REV ) * (F32)SEC_PER_MIN;
+            spdDelta = incDelta;
+            bloodPumpSpeedRPM.data = ( (F32)spdDelta / (F32)BP_HALL_EDGE_COUNTS_PER_REV ) * (F32)SEC_PER_MIN;
+            delta = ( bpMotorHallSensorCount >= last ? bpMotorHallSensorCount - last : ( HEX_64_K - last ) + bpMotorHallSensorCount );
+            bloodPumpMotorEdgeCount += delta;
         }
         else
         {
-            delta = decDelta;
-            bloodPumpSpeedRPM.data = ( (F32)delta / (F32)BP_HALL_EDGE_COUNTS_PER_REV ) * (F32)SEC_PER_MIN * -1.0;
+            spdDelta = decDelta;
+            bloodPumpSpeedRPM.data = ( (F32)spdDelta / (F32)BP_HALL_EDGE_COUNTS_PER_REV ) * (F32)SEC_PER_MIN * -1.0;
+            delta = ( bpMotorHallSensorCount <= last ? last - bpMotorHallSensorCount : ( HEX_64_K - bpMotorHallSensorCount ) + last );
+            bloodPumpMotorEdgeCount -= (S32)delta;
         }
-        bloodPumpMotorEdgeCount += delta;
 
         // Update last count for next time
         bpLastMotorHallSensorCounts[ nextIdx ] = bpMotorHallSensorCount;