Index: firmware/App/Drivers/PeristalticPump.c
===================================================================
diff -u -rfc985a2080a265d14be32959fa41fb43318e4ff4 -r09352c35f1c46a7df3b86fb693fceeb834761148
--- firmware/App/Drivers/PeristalticPump.c	(.../PeristalticPump.c)	(revision fc985a2080a265d14be32959fa41fb43318e4ff4)
+++ firmware/App/Drivers/PeristalticPump.c	(.../PeristalticPump.c)	(revision 09352c35f1c46a7df3b86fb693fceeb834761148)
@@ -30,13 +30,13 @@
 
 #define H4_PUMP_CMD_GAIN        0.9F                                            ///< Gain for blood pump commanded RPM that must be applied before sending to FPGA.
 #define H4_PUMP_CMD_OFFSET      80.0F                                           ///< Offset for blood pump commanded RPM that must be applied before sending to FPGA.
-#define H4_PUMP_CMD_CAL(r)      ((r) * H4_PUMP_CMD_GAIN + H4_PUMP_CMD_OFFSET )  ///< Macro to calibrate a commanded blood pump RPM before sending to FPGA.
 
 #define H4_PERIOD_SEC           0.00001F                                        ///< Blood pump feedback period in seconds.
 #define H4_HZ_TO_RPM_SCALAR     10.0F                                           ///< Blood pump Hz to RPM scalar.
 #define H4_PERIOD_TO_HZ(p)      ( 1.0F / (F32)((S32)(p) * H4_PERIOD_SEC) )      ///< Blood pump period to Hz conversion macro.
 #define H4_HZ_TO_RPM(h)         ((h) * H4_HZ_TO_RPM_SCALAR)                     ///< Blood pump Hz to RPM conversion macro.
 #define H4_ZERO_SPEED_PERIOD    0xFFFF                                          ///< Blood pump period reported when pump is stopped.
+#define H4_INVALID_SPEED_PERIOD   0x0001                                        ///< Blood pump invalid speed period
 
 #define H4_ROT_GEAR_RATIO       64.0F                                           ///< Blood pump rotor to motor gear ratio.
 #define H4_ROT_PERIOD_SEC       0.001F                                          ///< Blood pump rotor feedback period in seconds.
@@ -98,13 +98,17 @@
     S16 rotPer       = getH4RotorCount();
     U16 rotorRevsNow = getH4RotorRevsCounter();
 
-    // update measured pump motor speed
-    if ( period != H4_ZERO_SPEED_PERIOD )
+    // Update measured pump motor speed.
+    if ( ( H4_ZERO_SPEED_PERIOD == period ) || ( H4_INVALID_SPEED_PERIOD == period ) )
     {
+        pumpMeasSpeedRPM = 0.0F;
+    }
+    else
+    {
         F32 Hz  = H4_PERIOD_TO_HZ( period );
         F32 rpm = H4_HZ_TO_RPM( Hz );
 
-        if ( pumpSetSpeedRPM < 0 )  // TODO - can we get a real measured direction to base measured speed sign on?
+        if ( pumpSetSpeedRPM < 0 )
         {
             pumpMeasSpeedRPM = rpm * -1.0F;
         }
@@ -113,12 +117,8 @@
             pumpMeasSpeedRPM = rpm;
         }
     }
-    else
-    {
-        pumpMeasSpeedRPM = 0.0F;
-    }
 
-    // update measured pump rotor speed
+    // This updates measured pump rotor speed.
     if ( rotPer != 0 )
     {
         pumpMeasRotSpeedRPM = H4_ROT_PERIOD_TO_RPM( rotPer );
@@ -128,18 +128,18 @@
         pumpMeasRotSpeedRPM = 0.0F;
     }
 
-    // monitor home command status if in progress, stop pump if rotor is in home position
+    // Monitor home command status and stop when the rotor reaches home.
     if ( ( TRUE == pumpHomeInProgress ) && ( TRUE == isPeristalticPumpHome() ) && ( TRUE == pumpHomeLowSignalSeen ) )
     {
         setPeristalticPumpSetSpeed( 0 );
         pumpHomeInProgress = FALSE;
     }
-    else if ( isPeristalticPumpHome() != TRUE )
+    else if ( TRUE != isPeristalticPumpHome() )
     {
         pumpHomeLowSignalSeen = TRUE;
     }
 
-    // update accumulated rotor revolutions count (extend 16-bit FPGA counter to 32-bit)
+    // Extend the 16 bit FPGA rotor revolution counter to 32 bits.
     delta = u16DiffWithWrap( rotorRevsPrev, rotorRevsNow );
     rotorRevsAccum += (U32)delta;
     rotorRevsPrev = rotorRevsNow;