Version 1.19 releasev1.19

Fixed some filament sensor issues

43 files changed, 457 insertions, 287 deletions

diff --git a/Release/Duet-0.6-0.8.5/Edge/RepRapFirmware-1.19RC5.bin b/Release/Duet-0.6-0.8.5/Edge/RepRapFirmware-1.19RC5.bin
deleted file mode 100644
index e2d0fa87..00000000
--- a/Release/Duet-0.6-0.8.5/Edge/RepRapFirmware-1.19RC5.bin
+++ /dev/null
diff --git a/Release/Duet-0.6-0.8.5/Edge/RepRapFirmware-1.19RC6.bin b/Release/Duet-0.6-0.8.5/Edge/RepRapFirmware-1.19RC6.bin
deleted file mode 100644
index c5887fd6..00000000
--- a/Release/Duet-0.6-0.8.5/Edge/RepRapFirmware-1.19RC6.bin
+++ /dev/null
diff --git a/Release/Duet-0.6-0.8.5/Edge/RepRapFirmware-1.19beta11.bin b/Release/Duet-0.6-0.8.5/Edge/RepRapFirmware-1.19beta11.bin
deleted file mode 100644
index 1960fe9e..00000000
--- a/Release/Duet-0.6-0.8.5/Edge/RepRapFirmware-1.19beta11.bin
+++ /dev/null
diff --git a/Release/Duet-0.6-0.8.5/Stable/DuetWebControl-1.15a.zip b/Release/Duet-0.6-0.8.5/Stable/DuetWebControl-1.15a.zip
deleted file mode 100644
index ae0e45b0..00000000
--- a/Release/Duet-0.6-0.8.5/Stable/DuetWebControl-1.15a.zip
+++ /dev/null
diff --git a/Release/Duet-0.6-0.8.5/Edge/DuetWebControl-1.19-RC1.zip b/Release/Duet-0.6-0.8.5/Stable/DuetWebControl-1.19.zip
index 06ffd580..c229a53d 100644
--- a/Release/Duet-0.6-0.8.5/Edge/DuetWebControl-1.19-RC1.zip
+++ b/Release/Duet-0.6-0.8.5/Stable/DuetWebControl-1.19.zip
diff --git a/Release/Duet-0.6-0.8.5/Stable/RepRapFirmware-1.18.1.bin b/Release/Duet-0.6-0.8.5/Stable/RepRapFirmware-1.18.1.bin
deleted file mode 100644
index 380e50a4..00000000
--- a/Release/Duet-0.6-0.8.5/Stable/RepRapFirmware-1.18.1.bin
+++ /dev/null
diff --git a/Release/Duet-0.6-0.8.5/Stable/RepRapFirmware-1.19.bin b/Release/Duet-0.6-0.8.5/Stable/RepRapFirmware-1.19.bin
new file mode 100644
index 00000000..26c9f89d
--- /dev/null
+++ b/Release/Duet-0.6-0.8.5/Stable/RepRapFirmware-1.19.bin
diff --git a/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19RC5.bin b/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19RC5.bin
deleted file mode 100644
index 67201339..00000000
--- a/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19RC5.bin
+++ /dev/null
diff --git a/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19RC6.bin b/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19RC6.bin
deleted file mode 100644
index adef2b0b..00000000
--- a/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19RC6.bin
+++ /dev/null
diff --git a/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19beta11.bin b/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19beta11.bin
deleted file mode 100644
index 3a3ac15c..00000000
--- a/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19beta11.bin
+++ /dev/null
diff --git a/Release/Duet-Ethernet/Stable/DuetEthernetFirmware-1.18.1.bin b/Release/Duet-Ethernet/Stable/DuetEthernetFirmware-1.18.1.bin
deleted file mode 100644
index 8bc491cd..00000000
--- a/Release/Duet-Ethernet/Stable/DuetEthernetFirmware-1.18.1.bin
+++ /dev/null
diff --git a/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19RC7.bin b/Release/Duet-Ethernet/Stable/DuetEthernetFirmware-1.19.bin
index bdf220f2..65a4cf94 100644
--- a/Release/Duet-Ethernet/Edge/DuetEthernetFirmware-1.19RC7.bin
+++ b/Release/Duet-Ethernet/Stable/DuetEthernetFirmware-1.19.bin
diff --git a/Release/Duet-Ethernet/Stable/DuetWebControl-1.15a.zip b/Release/Duet-Ethernet/Stable/DuetWebControl-1.15a.zip
deleted file mode 100644
index ae0e45b0..00000000
--- a/Release/Duet-Ethernet/Stable/DuetWebControl-1.15a.zip
+++ /dev/null
diff --git a/Release/Duet-Ethernet/Edge/DuetWebControl-1.19-RC1.zip b/Release/Duet-Ethernet/Stable/DuetWebControl-1.19.zip
index 06ffd580..c229a53d 100644
--- a/Release/Duet-Ethernet/Edge/DuetWebControl-1.19-RC1.zip
+++ b/Release/Duet-Ethernet/Stable/DuetWebControl-1.19.zip
diff --git a/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19RC5.bin b/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19RC5.bin
deleted file mode 100644
index 4bb34293..00000000
--- a/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19RC5.bin
+++ /dev/null
diff --git a/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19RC6.bin b/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19RC6.bin
deleted file mode 100644
index 0cb0566e..00000000
--- a/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19RC6.bin
+++ /dev/null
diff --git a/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19beta11.bin b/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19beta11.bin
deleted file mode 100644
index a0e9ea01..00000000
--- a/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19beta11.bin
+++ /dev/null
diff --git a/Release/Duet-WiFi/Stable/DuetWebControl-1.15a.bin b/Release/Duet-WiFi/Stable/DuetWebControl-1.15a.bin
deleted file mode 100644
index 80327997..00000000
--- a/Release/Duet-WiFi/Stable/DuetWebControl-1.15a.bin
+++ /dev/null
diff --git a/Release/Duet-WiFi/Edge/DuetWebControl-1.19-RC1.zip b/Release/Duet-WiFi/Stable/DuetWebControl-1.19.zip
index 06ffd580..c229a53d 100644
--- a/Release/Duet-WiFi/Edge/DuetWebControl-1.19-RC1.zip
+++ b/Release/Duet-WiFi/Stable/DuetWebControl-1.19.zip
diff --git a/Release/Duet-WiFi/Stable/DuetWiFiFirmware-1.18.1.bin b/Release/Duet-WiFi/Stable/DuetWiFiFirmware-1.18.1.bin
deleted file mode 100644
index b8c37593..00000000
--- a/Release/Duet-WiFi/Stable/DuetWiFiFirmware-1.18.1.bin
+++ /dev/null
diff --git a/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19RC7.bin b/Release/Duet-WiFi/Stable/DuetWiFiFirmware-1.19.bin
index 85c76f85..236b696f 100644
--- a/Release/Duet-WiFi/Edge/DuetWiFiFirmware-1.19RC7.bin
+++ b/Release/Duet-WiFi/Stable/DuetWiFiFirmware-1.19.bin
diff --git a/Release/Duet-WiFi/Stable/DuetWiFiServer-1.03-ch.bin b/Release/Duet-WiFi/Stable/DuetWiFiServer-1.03-ch.bin
deleted file mode 100644
index 5c8270b9..00000000
--- a/Release/Duet-WiFi/Stable/DuetWiFiServer-1.03-ch.bin
+++ /dev/null
diff --git a/Release/Duet-WiFi/Edge/DuetWiFiServer-1.19beta10.bin b/Release/Duet-WiFi/Stable/DuetWiFiServer-1.19.bin
index fe287ffa..ce9dccc7 100644
--- a/Release/Duet-WiFi/Edge/DuetWiFiServer-1.19beta10.bin
+++ b/Release/Duet-WiFi/Stable/DuetWiFiServer-1.19.bin
diff --git a/Release/RADDS/Edge/RepRapFirmware-RADDS-1.17d.bin b/Release/RADDS/Edge/RepRapFirmware-RADDS-1.17d.bin
deleted file mode 100644
index ac2a728c..00000000
--- a/Release/RADDS/Edge/RepRapFirmware-RADDS-1.17d.bin
+++ /dev/null
diff --git a/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19.bin b/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19.bin
new file mode 100644
index 00000000..c089d2c0
--- /dev/null
+++ b/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19.bin
diff --git a/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19RC5.bin b/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19RC5.bin
deleted file mode 100644
index c6bdda81..00000000
--- a/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19RC5.bin
+++ /dev/null
diff --git a/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19RC6.bin b/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19RC6.bin
deleted file mode 100644
index 4106443e..00000000
--- a/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19RC6.bin
+++ /dev/null
diff --git a/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19beta11.bin b/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19beta11.bin
deleted file mode 100644
index 32b69381..00000000
--- a/Release/RADDS/Edge/RepRapFirmware-RADDS-1.19beta11.bin
+++ /dev/null
diff --git a/src/FilamentSensors/Duet3DFilamentSensor.cpp b/src/FilamentSensors/Duet3DFilamentSensor.cpp
index 29e65c65..e5874bd0 100644
--- a/src/FilamentSensors/Duet3DFilamentSensor.cpp
+++ b/src/FilamentSensors/Duet3DFilamentSensor.cpp
@@ -13,10 +13,21 @@
 // Constructors
 Duet3DFilamentSensor::Duet3DFilamentSensor(int type)
 	: FilamentSensor(type), mmPerRev(DefaultMmPerRev),
-	  tolerance(DefaultTolerance), absTolerance(DefaultAbsTolerance), minimumExtrusionCheckLength(DefaultMinimumExtrusionCheckLength), withSwitch(type == 4),
-	  sensorValue(0), accumulatedExtrusionCommanded(0.0), accumulatedExtrusionMeasured(0.0), extrusionCommandedAtLastMeasurement(0.0),tentativeExtrusionCommanded(0.0),
-	  numberOfEdgesCaptured(0), lastMeasurementTime(0), state(RxdState::waitingForStartBit), samplesReceived(0)
+	  tolerance(DefaultTolerance), minimumExtrusionCheckLength(DefaultMinimumExtrusionCheckLength), withSwitch(type == 4)
 {
+	Init();
+}
+
+void Duet3DFilamentSensor::Init()
+{
+	samplesReceived = 0;
+	sensorValue = 0;
+	calibrationStarted = comparisonStarted = dataReceived = false;
+	edgeCaptureReadPointer = edgeCaptureWritePointer = 1;
+	edgeCaptures[0] = Platform::GetInterruptClocks();					// assume we just had a high-to-low transition
+	lastMeasurementTime = 0;
+	accumulatedExtrusionCommanded = accumulatedRevsMeasured = extrusionCommandedAtLastMeasurement = tentativeExtrusionCommanded = 0.0;
+	state = RxdState::waitingForStartBit;
 }
 
 // Configure this sensor, returning true if error and setting 'seen' if we processed any configuration parameters
@@ -28,32 +39,22 @@ bool Duet3DFilamentSensor::Configure(GCodeBuffer& gb, StringRef& reply, bool& se
 	}
 
 	gb.TryGetFValue('S', mmPerRev, seen);
-	gb.TryGetFValue('T', absTolerance, seen);
 	gb.TryGetFValue('E', minimumExtrusionCheckLength, seen);
 
 	if (gb.Seen('R'))
 	{
 		seen = true;
-		const float tol = gb.GetFValue();
-		if (tolerance < 0.0 || tolerance >= 100.0)
-		{
-			reply.copy("Relative tolerance must be between 0 and 100%");
-			return true;
-		}
-		tolerance = tol * 0.01;
+		tolerance = gb.GetFValue() * 0.01;
 	}
 
 	if (seen)
 	{
-		samplesReceived = 0;
-		numberOfEdgesCaptured = 0;
-		lastMeasurementTime = 0;
-		accumulatedExtrusionCommanded = accumulatedExtrusionMeasured = extrusionCommandedAtLastMeasurement = tentativeExtrusionCommanded = 0.0;
+		Init();
 	}
 	else
 	{
-		reply.printf("Duet3D filament sensor on endstop %u, %s microswitch, %.1fmm per rev, check every %.1fmm, tolerance %.1f%% + %.1fmm, current angle %.1f",
-						GetEndstopNumber(), (withSwitch) ? "with" : "no", mmPerRev, minimumExtrusionCheckLength, tolerance * 100.0, absTolerance, GetCurrentAngle());
+		reply.printf("Duet3D filament sensor on endstop %u, %s microswitch, %.1fmm per rev, check every %.1fmm, tolerance %.1f%%, current angle %.1f",
+						GetEndstopNumber(), (withSwitch) ? "with" : "no", mmPerRev, minimumExtrusionCheckLength, tolerance * 100.0, GetCurrentAngle());
 	}
 
 	return false;
@@ -62,12 +63,29 @@ bool Duet3DFilamentSensor::Configure(GCodeBuffer& gb, StringRef& reply, bool& se
 // ISR for when the pin state changes
 void Duet3DFilamentSensor::Interrupt()
 {
-	const size_t numEdgesCaptured = numberOfEdgesCaptured;							// capture volatile variable
-	if (numEdgesCaptured < MaxEdgeCaptures && (numEdgesCaptured % 2u) != (unsigned int)Platform::ReadPin(GetPin()))	// low-to-high transitions must be stored at even indices
+	uint32_t now = Platform::GetInterruptClocks();
+	const size_t writePointer = edgeCaptureWritePointer;			// capture volatile variable
+	if ((writePointer + 1) % EdgeCaptureBufferSize != edgeCaptureReadPointer)
 	{
-		edgeCaptures[numEdgesCaptured] = Platform::GetInterruptClocks();			// record the time at which this edge was detected
-		numberOfEdgesCaptured = numEdgesCaptured + 1;
+		if (Platform::ReadPin(GetPin()))
+		{
+			if ((writePointer & 1) == 0)							// low-to-high transitions should occur on odd indices
+			{
+				return;
+			}
+		}
+		else
+		{
+			if ((writePointer & 1) != 0)							// high-to-low transitions should occur on even indices
+			{
+				return;
+			}
+			now -= 40;												// partial correction for skew caused by debounce filter on Duet endstop inputs (measured skew = 74)
+		}
 	}
+
+	edgeCaptures[writePointer] = now;								// record the time at which this edge was detected
+	edgeCaptureWritePointer = (writePointer + 1) % EdgeCaptureBufferSize;
 }
 
 // Call the following regularly to keep the status up to date
@@ -77,105 +95,161 @@ void Duet3DFilamentSensor::Poll()
 	static const uint32_t NominalBitLength = DDA::stepClockRate/BitsPerSecond;
 	static const uint32_t MinBitLength = (NominalBitLength * 10)/13;	// allow 30% clock speed tolerance
 	static const uint32_t MaxBitLength = (NominalBitLength * 13)/10;	// allow 30% clock speed tolerance
-	static const uint32_t ErrorRecoveryDelayBits = 12;					// after an error we wait for the line to be low for this long
+	static const uint32_t ErrorRecoveryDelayBits = 8;					// before a start bit we want the line to be low for this long
 	static const uint32_t ErrorRecoveryTime = NominalBitLength * ErrorRecoveryDelayBits;
 
-	const size_t numEdgesCaptured = numberOfEdgesCaptured;				// capture volatile variable
-	const uint32_t now = Platform::GetInterruptClocks();
-	switch (state)
+	bool again;
+	do
 	{
-	case RxdState::waitingForStartBit:
-		if (numEdgesCaptured >= 2)
+		again = false;
+		const size_t writePointer = edgeCaptureWritePointer;			// capture volatile variable
+		const uint32_t now = Platform::GetInterruptClocks();
+		switch (state)
 		{
-			// Check for a valid start bit
-			startBitLength = edgeCaptures[1] - edgeCaptures[0];
-			if (startBitLength >= MinBitLength && startBitLength <= MaxBitLength)
+		case RxdState::waitingForStartBit:
+			if ((edgeCaptureReadPointer & 1u) == 0)						// if we are out of sync (this is normal when the last stuffing bit was a 1)
 			{
-				bitChangeIndex = 2;
-				valueBeingAssembled = 0;
-				nibblesAssembled = 0;
-				tentativeExtrusionCommanded = accumulatedExtrusionCommanded;
-				state = RxdState::waitingForNibble;
+				if (edgeCaptureReadPointer != edgeCaptureWritePointer)
+				{
+					edgeCaptureReadPointer = (edgeCaptureReadPointer + 1) % EdgeCaptureBufferSize;
+					again = true;
+				}
 			}
-			else
+			else if (writePointer != edgeCaptureReadPointer)
 			{
-				state = RxdState::errorRecovery;
+				if (edgeCaptures[edgeCaptureReadPointer] - edgeCaptures[(edgeCaptureReadPointer - 1) % EdgeCaptureBufferSize] < ErrorRecoveryTime)
+				{
+					// The input line has not been low for long enough before the start bit
+					edgeCaptureReadPointer = (edgeCaptureReadPointer + 1) % EdgeCaptureBufferSize;
+					state = RxdState::errorRecovery1;
+					again = true;
+				}
+				else
+				{
+					tentativeExtrusionCommanded = accumulatedExtrusionCommanded;	// we have received what could be the beginning of a start bit
+					state = RxdState::waitingForEndOfStartBit;
+					again = true;
+				}
 			}
-		}
-		break;
+			break;
 
-	case RxdState::waitingForNibble:
-		{
-			const uint32_t nibbleStartTime = edgeCaptures[bitChangeIndex - 1];
-			if (now - nibbleStartTime > (13 * startBitLength)/2)
+		case RxdState::waitingForEndOfStartBit:
+			// This state must time out because while we are in it, comparison of filament extruded is suspended
+			if ((writePointer - edgeCaptureReadPointer) % EdgeCaptureBufferSize >= 2)
 			{
-				// 6.5 bit times have passed since the start of the bit that preceded the current nibble, so we should have a complete nibble and the following stuffing bit
-				uint32_t samplePoint = (startBitLength * 3)/2;		// sampling time after the end of the start bit for bit 7 (MSB)
-				uint8_t currentNibble = 0;
-				for (uint8_t numBits = 0; numBits < 5; ++numBits)
+				// Check for a valid start bit
+				lastBitChangeIndex = (edgeCaptureReadPointer + 1u) % EdgeCaptureBufferSize;
+				startBitLength = edgeCaptures[lastBitChangeIndex] - edgeCaptures[edgeCaptureReadPointer];
+				if (startBitLength >= MinBitLength && startBitLength <= MaxBitLength)
 				{
-					if (bitChangeIndex < numEdgesCaptured && edgeCaptures[bitChangeIndex] - nibbleStartTime < samplePoint)
+					valueBeingAssembled = 0;
+					nibblesAssembled = 0;
+					edgeCaptureReadPointer = lastBitChangeIndex;
+					state = RxdState::waitingForNibble;
+					again = true;
+					//debugPrintf("sb %u\n", startBitLength);
+				}
+				else
+				{
+					edgeCaptureReadPointer = (edgeCaptureReadPointer + 2) % EdgeCaptureBufferSize;
+					state = RxdState::errorRecovery2;
+					again = true;
+				}
+			}
+			else if (now - edgeCaptures[edgeCaptureReadPointer] > MaxBitLength)
+			{
+				state = RxdState::errorRecovery2;
+				again = true;
+			}
+			break;
+
+		case RxdState::waitingForNibble:
+			// This state must time out because while we are in it, comparison of filament extruded is suspended
+			{
+				const uint32_t nibbleStartTime = edgeCaptures[lastBitChangeIndex];
+				if (now - nibbleStartTime > (13 * startBitLength)/2)
+				{
+					// 6.5 bit times have passed since the start of the bit that preceded the current nibble, so we should have a complete nibble and the following stuffing bit
+					uint32_t samplePoint = (startBitLength * 3)/2;		// sampling time after the end of the start bit for bit 7 (MSB)
+					uint8_t currentNibble = 0;
+					size_t nextBitChangeIndex = (lastBitChangeIndex + 1) % EdgeCaptureBufferSize;
+					for (uint8_t numBits = 0; numBits < 5; ++numBits)
 					{
-						++bitChangeIndex;
-						if (bitChangeIndex < numEdgesCaptured && edgeCaptures[bitChangeIndex] - nibbleStartTime < samplePoint)
+						if (nextBitChangeIndex != edgeCaptureWritePointer && edgeCaptures[nextBitChangeIndex] - nibbleStartTime < samplePoint)
 						{
-							state = RxdState::errorRecovery;		// there should be at most 1 transition per bit
-							return;
+							lastBitChangeIndex = nextBitChangeIndex;
+							nextBitChangeIndex = (lastBitChangeIndex + 1) % EdgeCaptureBufferSize;
+							if (nextBitChangeIndex != writePointer && edgeCaptures[nextBitChangeIndex] - nibbleStartTime < samplePoint)
+							{
+								edgeCaptureReadPointer = nextBitChangeIndex;
+								state = RxdState::errorRecovery3;
+								again = true;
+								break;
+							}
 						}
+						currentNibble <<= 1;
+						currentNibble |= (uint8_t)(lastBitChangeIndex & 1u);
+						samplePoint += startBitLength;
 					}
-					currentNibble <<= 1;
-					if ((bitChangeIndex & 1u) != 0)
+
+					if (state != RxdState::waitingForNibble)
 					{
-						currentNibble |= 1u;
+						break;
 					}
-					samplePoint += startBitLength;
-				}
 
-				// The 5th bit we received should be the inverse of the 4th bit
-				if ((((currentNibble >> 1u) ^ currentNibble) & 0x01u) == 0)
-				{
-					state = RxdState::errorRecovery;
-					return;
-				}
-
-				currentNibble >>= 1;
-				valueBeingAssembled = (valueBeingAssembled << 4) | currentNibble;
-				++nibblesAssembled;
-				if (nibblesAssembled == 4)
-				{
-					numberOfEdgesCaptured = 0;				// ready for a new byte
-					if (samplesReceived != 0)
+					// The 5th bit we received should be the inverse of the 4th bit
+					if ((((currentNibble >> 1u) ^ currentNibble) & 0x01u) == 0)
 					{
-						const uint16_t angleChange = (valueBeingAssembled - sensorValue) & AngleMask;		// angle change in range 0..1023
-						const int32_t movement = (angleChange <= 512) ? (int32_t)angleChange : (int32_t)angleChange - 1024;
-						accumulatedExtrusionMeasured += (float)movement * mmPerRev * (1.0/1024.0);
+						edgeCaptureReadPointer = nextBitChangeIndex;
+						state = RxdState::errorRecovery4;
+						again = true;
+						break;
 					}
 
-					lastMeasurementTime = millis();
-					extrusionCommandedAtLastMeasurement = tentativeExtrusionCommanded;
-					sensorValue = valueBeingAssembled;
-					if (samplesReceived < 100)
+					currentNibble >>= 1;
+					valueBeingAssembled = (valueBeingAssembled << 4) | currentNibble;
+					++nibblesAssembled;
+					if (nibblesAssembled == 4)
 					{
-						++samplesReceived;
+						edgeCaptureReadPointer = nextBitChangeIndex;	// ready for a new word
+						if (samplesReceived == 0)
+						{
+							dataReceived = true;
+							accumulatedExtrusionCommanded -= tentativeExtrusionCommanded;
+							accumulatedRevsMeasured = 0.0;				// use the first measurement sample as a baseline
+						}
+						else
+						{
+							const uint16_t angleChange = (valueBeingAssembled - sensorValue) & AngleMask;		// angle change in range 0..1023
+							const int32_t movement = (angleChange <= 512) ? (int32_t)angleChange : (int32_t)angleChange - 1024;
+							accumulatedRevsMeasured += (float)movement/1024;
+						}
+
+						lastMeasurementTime = millis();
+						extrusionCommandedAtLastMeasurement = tentativeExtrusionCommanded;
+						sensorValue = valueBeingAssembled;
+						if (samplesReceived < 100)
+						{
+							++samplesReceived;
+						}
+						edgeCaptureReadPointer = nextBitChangeIndex;
+						state = RxdState::waitingForStartBit;
 					}
-					state = RxdState::waitingForStartBit;
+					again = true;
 				}
 			}
-		}
-		break;
+			break;
 
-	case RxdState::errorRecovery:
-		if (Platform::ReadPin(GetPin()) || numEdgesCaptured != 0)	// when we first enter this state, numEdgesCaptured is always nonzero
-		{
-			errorRecoveryStartTime = now;
-			numberOfEdgesCaptured = 0;
-		}
-		else if (now - errorRecoveryStartTime >= ErrorRecoveryTime)
-		{
+		default:	// error recovery states
+			if (reprap.Debug(moduleFilamentSensors))
+			{
+				debugPrintf("Fil err %u\n", (unsigned int)state);
+			}
 			state = RxdState::waitingForStartBit;
+			again = true;
+			break;
 		}
-		break;
-	}
+	} while (again);
 }
 
 // Return the current wheel angle
@@ -186,29 +260,32 @@ float Duet3DFilamentSensor::GetCurrentAngle() const
 
 // Call the following at intervals to check the status. This is only called when extrusion is in progress or imminent.
 // 'filamentConsumed' is the net amount of extrusion since the last call to this function.
-FilamentSensorStatus Duet3DFilamentSensor::Check(float filamentConsumed)
+FilamentSensorStatus Duet3DFilamentSensor::Check(bool full, float filamentConsumed)
 {
 	accumulatedExtrusionCommanded += filamentConsumed;
 	Poll();
 
 	FilamentSensorStatus ret = FilamentSensorStatus::ok;
-	if ((sensorValue & ErrorBit) != 0)
-	{
-		ret = FilamentSensorStatus::sensorError;
-	}
-	else if (withSwitch && (sensorValue & SwitchOpenBit) != 0)
+	if (full)
 	{
-		ret = FilamentSensorStatus::noFilament;
-	}
-	else if (samplesReceived >= 10)
-	{
-		if (extrusionCommandedAtLastMeasurement >= minimumExtrusionCheckLength)
+		if ((sensorValue & ErrorBit) != 0)
 		{
-			ret = CheckFilament(extrusionCommandedAtLastMeasurement);
+			ret = FilamentSensorStatus::sensorError;
 		}
-		else if (accumulatedExtrusionCommanded >= minimumExtrusionCheckLength && millis() - lastMeasurementTime > 110)
+		else if (withSwitch && (sensorValue & SwitchOpenBit) != 0)
 		{
-			ret = CheckFilament(accumulatedExtrusionCommanded);
+			ret = FilamentSensorStatus::noFilament;
+		}
+		else if (samplesReceived >= 10 && state != RxdState::waitingForEndOfStartBit && state != RxdState::waitingForNibble)
+		{
+			if (extrusionCommandedAtLastMeasurement >= minimumExtrusionCheckLength)
+			{
+				ret = CheckFilament(extrusionCommandedAtLastMeasurement, false);
+			}
+			else if (accumulatedExtrusionCommanded >= minimumExtrusionCheckLength * 1.1 && millis() - lastMeasurementTime > 110)
+			{
+				ret = CheckFilament(accumulatedExtrusionCommanded, true);
+			}
 		}
 	}
 
@@ -216,55 +293,91 @@ FilamentSensorStatus Duet3DFilamentSensor::Check(float filamentConsumed)
 }
 
 // Compare the amount commanded with the amount of extrusion measured, and set up for the next comparison
-FilamentSensorStatus Duet3DFilamentSensor::CheckFilament(float amountCommanded)
+FilamentSensorStatus Duet3DFilamentSensor::CheckFilament(float amountCommanded, bool overdue)
 {
+	const float extrusionMeasured = accumulatedRevsMeasured * mmPerRev;
 	if (reprap.Debug(moduleFilamentSensors))
 	{
-		debugPrintf("Extr req %.3f meas %.3f\n", amountCommanded, accumulatedExtrusionMeasured);
+		debugPrintf("Extr req %.3f meas %.3f rem %.3f %s\n", amountCommanded, extrusionMeasured, accumulatedExtrusionCommanded - amountCommanded, (overdue) ? " overdue" : "");
 	}
 
 	FilamentSensorStatus ret = FilamentSensorStatus::ok;
-	const float minExtrusionExpected = ( (amountCommanded >= 0.0)
-										 ? amountCommanded * (1.0 - tolerance)
-											: amountCommanded * (1.0 + tolerance)
-									   )
-									   - absTolerance;
-	if (accumulatedExtrusionMeasured < minExtrusionExpected)
+	if (!comparisonStarted)
 	{
-		ret = FilamentSensorStatus::tooLittleMovement;
+		// The first measurement after we start extruding is often a long way out, so discard it
+		comparisonStarted = true;
+		calibrationStarted = false;
+	}
+	else if (tolerance >= 0.0)
+	{
+		const float minExtrusionExpected = (amountCommanded >= 0.0)
+											 ? amountCommanded * (1.0 - tolerance)
+												: amountCommanded * (1.0 + tolerance);
+		if (extrusionMeasured < minExtrusionExpected)
+		{
+			ret = FilamentSensorStatus::tooLittleMovement;
+		}
+		else
+		{
+			const float maxExtrusionExpected = (amountCommanded >= 0.0)
+												 ? amountCommanded * (1.0 + tolerance)
+													: amountCommanded * (1.0 - tolerance);
+			if (extrusionMeasured > maxExtrusionExpected)
+			{
+				ret = FilamentSensorStatus::tooMuchMovement;
+			}
+		}
 	}
 	else
 	{
-		const float maxExtrusionExpected = ( (amountCommanded >= 0.0)
-											 ? amountCommanded * (1.0 + tolerance)
-												: amountCommanded * (1.0 - tolerance)
-										   )
-										   + absTolerance;
-		if (accumulatedExtrusionMeasured > maxExtrusionExpected)
+		// Tolerance < 0.0 means do calibration
+		const float ratio = accumulatedRevsMeasured/amountCommanded;
+		if (calibrationStarted)
 		{
-			ret = FilamentSensorStatus::tooMuchMovement;
+			if (ratio < minMovementRatio)
+			{
+				minMovementRatio = ratio;
+			}
+			if (ratio > maxMovementRatio)
+			{
+				maxMovementRatio = ratio;
+			}
+			totalExtrusionCommanded += amountCommanded;
+			totalRevsMeasured += accumulatedRevsMeasured;
+		}
+		else
+		{
+			minMovementRatio = maxMovementRatio = ratio;
+			totalExtrusionCommanded = amountCommanded;
+			totalRevsMeasured = accumulatedRevsMeasured;
+			calibrationStarted = true;
 		}
 	}
-
 	accumulatedExtrusionCommanded -= amountCommanded;
-	extrusionCommandedAtLastMeasurement = accumulatedExtrusionMeasured = 0.0;
+	extrusionCommandedAtLastMeasurement = accumulatedRevsMeasured = 0.0;
+
 	return ret;
 }
 
 // Clear the measurement state - called when we are not printing a file. Return the present/not present status if available.
-FilamentSensorStatus Duet3DFilamentSensor::Clear()
+FilamentSensorStatus Duet3DFilamentSensor::Clear(bool full)
 {
 	Poll();								// to keep the diagnostics up to date
-	accumulatedExtrusionCommanded = accumulatedExtrusionMeasured = extrusionCommandedAtLastMeasurement = tentativeExtrusionCommanded = 0.0;
+	accumulatedExtrusionCommanded = accumulatedRevsMeasured = extrusionCommandedAtLastMeasurement = tentativeExtrusionCommanded = 0.0;
 	samplesReceived = 0;
+	comparisonStarted = false;
+
 	FilamentSensorStatus ret = FilamentSensorStatus::ok;
-	if ((sensorValue & ErrorBit) != 0)
+	if (full)
 	{
-		ret = FilamentSensorStatus::sensorError;
-	}
-	else if (withSwitch && (sensorValue & SwitchOpenBit) != 0)
-	{
-		ret = FilamentSensorStatus::noFilament;
+		if ((sensorValue & ErrorBit) != 0)
+		{
+			ret = FilamentSensorStatus::sensorError;
+		}
+		else if (withSwitch && (sensorValue & SwitchOpenBit) != 0)
+		{
+			ret = FilamentSensorStatus::noFilament;
+		}
 	}
 	return ret;
 }
@@ -273,11 +386,23 @@ FilamentSensorStatus Duet3DFilamentSensor::Clear()
 void Duet3DFilamentSensor::Diagnostics(MessageType mtype, unsigned int extruder)
 {
 	Poll();
-	const char* const statusText = (samplesReceived == 0) ? "no data received"
+	const char* const statusText = (!dataReceived) ? "no data received"
 									: ((sensorValue & ErrorBit) != 0) ? "error"
 										: (withSwitch && (sensorValue & SwitchOpenBit) != 0) ? "no filament"
 											: "ok";
-	reprap.GetPlatform().MessageF(mtype, "Extruder %u sensor: angle %.1f, %s\n", extruder, GetCurrentAngle(), statusText);
+	reprap.GetPlatform().MessageF(mtype, "Extruder %u sensor: angle %.1f, %s, ", extruder, GetCurrentAngle(), statusText);
+	if (calibrationStarted && fabs(totalRevsMeasured) > 1.0 && totalExtrusionCommanded > 20.0)
+	{
+		const float measuredMmPerRev = totalExtrusionCommanded/totalRevsMeasured;
+		const float normalRatio = 1.0/measuredMmPerRev;
+		const int measuredPosTolerance = lrintf(100.0 * (((normalRatio > 0.0) ? maxMovementRatio : minMovementRatio) - normalRatio)/normalRatio);
+		const int measuredNegTolerance = lrintf(100.0 * (normalRatio - ((normalRatio > 0.0) ? minMovementRatio : maxMovementRatio))/normalRatio);
+		reprap.GetPlatform().MessageF(mtype,"%.2fmm/rev, tolerance +%d%% -%d%%\n", measuredMmPerRev, measuredPosTolerance, measuredNegTolerance);
+	}
+	else
+	{
+		reprap.GetPlatform().Message(mtype, "no calibration data\n");
+	}
 }
 
 // End
diff --git a/src/FilamentSensors/Duet3DFilamentSensor.h b/src/FilamentSensors/Duet3DFilamentSensor.h
index 679058cd..94e0204d 100644
--- a/src/FilamentSensors/Duet3DFilamentSensor.h
+++ b/src/FilamentSensors/Duet3DFilamentSensor.h
@@ -16,59 +16,68 @@ public:
 	Duet3DFilamentSensor(int type);
 
 	bool Configure(GCodeBuffer& gb, StringRef& reply, bool& seen) override;
-	FilamentSensorStatus Check(float filamentConsumed) override;
-	FilamentSensorStatus Clear() override;
+	FilamentSensorStatus Check(bool full, float filamentConsumed) override;
+	FilamentSensorStatus Clear(bool full) override;
 	void Diagnostics(MessageType mtype, unsigned int extruder) override;
 	void Interrupt() override;
 
 private:
-	static constexpr float DefaultMmPerRev = 15.0;
+	static constexpr float DefaultMmPerRev = 28.8;
 	static constexpr float DefaultTolerance = 0.2;
-	static constexpr float DefaultAbsTolerance = 1.0;
 	static constexpr float DefaultMinimumExtrusionCheckLength = 3.0;
 
 	static constexpr uint16_t SwitchOpenBit = 0x4000u;
 	static constexpr uint16_t ErrorBit = 0x8000u;
-	static constexpr uint16_t AngleMask = 0x03FF;		// 10-bit sensor angle
+	static constexpr uint16_t AngleMask = 0x03FF;			// 10-bit sensor angle
 
-	static constexpr size_t MaxEdgeCaptures = 30;
+	static constexpr size_t EdgeCaptureBufferSize = 64;		// must be a power of 2
 
+	void Init();
 	void Poll();
 	float GetCurrentAngle() const;
-	FilamentSensorStatus CheckFilament(float amountCommanded);
+	FilamentSensorStatus CheckFilament(float amountCommanded, bool overdue);
 
 	// Configuration parameters
 	float mmPerRev;
 	float tolerance;
-	float absTolerance;
 	float minimumExtrusionCheckLength;
 	bool withSwitch;
 
 	// Other data
 	uint16_t sensorValue;
 	float accumulatedExtrusionCommanded;
-	float accumulatedExtrusionMeasured;
+	float accumulatedRevsMeasured;
 	float extrusionCommandedAtLastMeasurement;
 	float tentativeExtrusionCommanded;
 
-	volatile size_t numberOfEdgesCaptured;
 	uint32_t lastMeasurementTime;
-	uint32_t edgeCaptures[MaxEdgeCaptures];
+	uint32_t edgeCaptures[EdgeCaptureBufferSize];
+	size_t edgeCaptureReadPointer;
+	volatile size_t edgeCaptureWritePointer;
+	float minMovementRatio, maxMovementRatio;
+	float totalExtrusionCommanded, totalRevsMeasured;
 
 	enum class RxdState : uint8_t
 	{
 		waitingForStartBit,
+		waitingForEndOfStartBit,
 		waitingForNibble,
-		errorRecovery
+		errorRecovery1,
+		errorRecovery2,
+		errorRecovery3,
+		errorRecovery4
 	};
 
 	RxdState state;
 	uint32_t startBitLength;
 	uint32_t errorRecoveryStartTime;
-	size_t bitChangeIndex;
+	size_t lastBitChangeIndex;
 	uint16_t valueBeingAssembled;
 	uint8_t nibblesAssembled;
 	uint8_t samplesReceived;
+	bool dataReceived;
+	bool comparisonStarted;
+	bool calibrationStarted;
 };
 
 #endif /* SRC_FILAMENTSENSORS_DUET3DFILAMENTSENSOR_H_ */
diff --git a/src/FilamentSensors/FilamentSensor.cpp b/src/FilamentSensors/FilamentSensor.cpp
index 77e9cf4d..02035f1d 100644
--- a/src/FilamentSensors/FilamentSensor.cpp
+++ b/src/FilamentSensors/FilamentSensor.cpp
@@ -11,7 +11,13 @@
 #include "RepRap.h"
 #include "Platform.h"
 #include "GCodes/GCodeBuffer.h"
+#include "Movement/Move.h"
+#include "PrintMonitor.h"
 
+// Static data
+FilamentSensor *FilamentSensor::filamentSensors[MaxExtruders] = { 0 };
+
+// Default destructor
 FilamentSensor::~FilamentSensor()
 {
 	if (pin != NoPin)
@@ -88,4 +94,79 @@ bool FilamentSensor::ConfigurePin(GCodeBuffer& gb, StringRef& reply, bool& seen)
 	static_cast<FilamentSensor*>(param)->Interrupt();
 }
 
+/*static*/ void FilamentSensor::Spin(bool full)
+{
+	// Filament sensors
+	for (size_t extruder = 0; extruder < MaxExtruders; ++extruder)
+	{
+		if (filamentSensors[extruder] != nullptr)
+		{
+			GCodes& gCodes = reprap.GetGCodes();
+			const float extrusionCommanded = (float)reprap.GetMove().GetAccumulatedExtrusion(extruder)/reprap.GetPlatform().DriveStepsPerUnit(extruder + gCodes.GetTotalAxes());
+																													// get and clear the Move extrusion commanded
+			if (reprap.GetPrintMonitor().IsPrinting() && !gCodes.IsPausing() && !gCodes.IsResuming() && !gCodes.IsPaused())
+			{
+				const FilamentSensorStatus fstat = filamentSensors[extruder]->Check(full, extrusionCommanded);
+				if (full && fstat != FilamentSensorStatus::ok && extrusionCommanded > 0.0)
+				{
+					if (reprap.Debug(moduleFilamentSensors))
+					{
+						debugPrintf("Filament error: extruder %u reports %s\n", extruder, FilamentSensor::GetErrorMessage(fstat));
+					}
+					else
+					{
+						gCodes.FilamentError(extruder, fstat);
+					}
+				}
+			}
+			else
+			{
+				filamentSensors[extruder]->Clear(full);
+			}
+		}
+	}
+}
+
+// Return the filament sensor associated with a particular extruder
+/*static*/ FilamentSensor *FilamentSensor::GetFilamentSensor(int extruder)
+{
+	return (extruder >= 0 && extruder < (int)MaxExtruders) ? filamentSensors[extruder] : nullptr;
+}
+
+// Set the filament sensor associated with a particular extruder
+/*static*/ bool FilamentSensor::SetFilamentSensorType(int extruder, int newSensorType)
+{
+	if (extruder >= 0 && extruder < (int)MaxExtruders)
+	{
+		FilamentSensor*& sensor = filamentSensors[extruder];
+		const int oldSensorType = (sensor == nullptr) ? 0 : sensor->GetType();
+		if (newSensorType != oldSensorType)
+		{
+			delete sensor;
+			sensor = Create(newSensorType);
+			return true;
+		}
+	}
+
+	return false;
+}
+
+// Send diagnostics info
+/*static*/ void FilamentSensor::Diagnostics(MessageType mtype)
+{
+	bool first = true;
+	for (size_t i = 0; i < MaxExtruders; ++i)
+	{
+		if (filamentSensors[i] != nullptr)
+		{
+			if (first)
+			{
+				reprap.GetPlatform().Message(mtype, "=== Filament sensors ===\n");
+				first = false;
+			}
+			filamentSensors[i]->Diagnostics(mtype, i);
+		}
+	}
+}
+
 // End
diff --git a/src/FilamentSensors/FilamentSensor.h b/src/FilamentSensors/FilamentSensor.h
index 4461a8bf..1931a03a 100644
--- a/src/FilamentSensors/FilamentSensor.h
+++ b/src/FilamentSensors/FilamentSensor.h
@@ -28,10 +28,10 @@ public:
 
 	// Call the following at intervals to check the status. This is only called when extrusion is in progress or imminent.
 	// 'filamentConsumed' is the net amount of extrusion since the last call to this function.
-	virtual FilamentSensorStatus Check(float filamentConsumed) = 0;
+	virtual FilamentSensorStatus Check(bool full, float filamentConsumed) = 0;
 
 	// Clear the measurement state - called when we are not printing a file. Return the present/not present status if available.
-	virtual FilamentSensorStatus Clear() = 0;
+	virtual FilamentSensorStatus Clear(bool full) = 0;
 
 	// Print diagnostic info for this sensor
 	virtual void Diagnostics(MessageType mtype, unsigned int extruder) = 0;
@@ -45,12 +45,21 @@ public:
 	// Return the type of this sensor
 	int GetType() const { return type; }
 
-	// Create a filament sensor returning null if not a valid sensor type
-	static FilamentSensor *Create(int type);
-
 	// Return an error message corresponding to a status code
 	static const char *GetErrorMessage(FilamentSensorStatus f);
 
+	// Poll the filament sensors
+	static void Spin(bool full);
+
+	// Return the filament sensor associated with a particular extruder
+	static FilamentSensor *GetFilamentSensor(int extruder);
+
+	// Set the filament sensor associated with a particular extruder
+	static bool SetFilamentSensorType(int extruder, int newSensorType);
+
+	// Send diagnostics info
+	static void Diagnostics(MessageType mtype);
+
 protected:
 	FilamentSensor(int t) : type(t), pin(NoPin) { }
 
@@ -61,8 +70,13 @@ protected:
 	Pin GetPin() const { return pin; }
 
 private:
+	// Create a filament sensor returning null if not a valid sensor type
+	static FilamentSensor *Create(int type);
+
 	static void InterruptEntry(void *param);
 
+	static FilamentSensor *filamentSensors[MaxExtruders];
+
 	int type;
 	int endstopNumber;
 	Pin pin;
diff --git a/src/FilamentSensors/SimpleFilamentSensor.cpp b/src/FilamentSensors/SimpleFilamentSensor.cpp
index a5c0549f..87ee7b33 100644
--- a/src/FilamentSensors/SimpleFilamentSensor.cpp
+++ b/src/FilamentSensors/SimpleFilamentSensor.cpp
@@ -23,7 +23,7 @@ bool SimpleFilamentSensor::Configure(GCodeBuffer& gb, StringRef& reply, bool& se
 
 	if (seen)
 	{
-		Check(0.0);
+		Check(true, 0.0);
 	}
 	else
 	{
@@ -49,14 +49,14 @@ void SimpleFilamentSensor::Poll()
 
 // Call the following at intervals to check the status. This is only called when extrusion is in progress or imminent.
 // 'filamentConsumed' is the net amount of extrusion since the last call to this function.
-FilamentSensorStatus SimpleFilamentSensor::Check(float filamentConsumed)
+FilamentSensorStatus SimpleFilamentSensor::Check(bool full, float filamentConsumed)
 {
 	Poll();
 	return (filamentPresent) ? FilamentSensorStatus::ok : FilamentSensorStatus::noFilament;
 }
 
 // Clear the measurement state - called when we are not printing a file. Return the present/not present status if available.
-FilamentSensorStatus SimpleFilamentSensor::Clear()
+FilamentSensorStatus SimpleFilamentSensor::Clear(bool full)
 {
 	Poll();
 	return (filamentPresent) ? FilamentSensorStatus::ok : FilamentSensorStatus::noFilament;
diff --git a/src/FilamentSensors/SimpleFilamentSensor.h b/src/FilamentSensors/SimpleFilamentSensor.h
index 73a5f96d..05122005 100644
--- a/src/FilamentSensors/SimpleFilamentSensor.h
+++ b/src/FilamentSensors/SimpleFilamentSensor.h
@@ -16,8 +16,8 @@ public:
 	SimpleFilamentSensor(int type);
 
 	bool Configure(GCodeBuffer& gb, StringRef& reply, bool& seen) override;
-	FilamentSensorStatus Check(float filamentConsumed) override;
-	FilamentSensorStatus Clear() override;
+	FilamentSensorStatus Check(bool full, float filamentConsumed) override;
+	FilamentSensorStatus Clear(bool full) override;
 	void Diagnostics(MessageType mtype, unsigned int extruder) override;
 	void Interrupt() override;
 
diff --git a/src/GCodes/GCodes2.cpp b/src/GCodes/GCodes2.cpp
index 592eb19b..73b871db 100644
--- a/src/GCodes/GCodes2.cpp
+++ b/src/GCodes/GCodes2.cpp
@@ -3320,17 +3320,17 @@ bool GCodes::HandleMcode(GCodeBuffer& gb, StringRef& reply)
 				gb.TryGetIValue('P', sensorType, seen);
 				if (seen)
 				{
-					platform.SetFilamentSensorType(extruder, sensorType);
+					FilamentSensor::SetFilamentSensorType(extruder, sensorType);
 				}
 
-				FilamentSensor *sensor = platform.GetFilamentSensor(extruder);
+				FilamentSensor *sensor = FilamentSensor::GetFilamentSensor(extruder);
 				if (sensor != nullptr)
 				{
 					// Configure the sensor
 					error = sensor->Configure(gb, reply, seen);
 					if (error)
 					{
-						platform.SetFilamentSensorType(extruder, 0);		// delete the sensor
+						FilamentSensor::SetFilamentSensorType(extruder, 0);		// delete the sensor
 					}
 				}
 				else if (!seen)
diff --git a/src/Movement/DDA.cpp b/src/Movement/DDA.cpp
index 7387694d..394c348b 100644
--- a/src/Movement/DDA.cpp
+++ b/src/Movement/DDA.cpp
@@ -1530,7 +1530,7 @@ bool DDA::Step()
 	if (state == completed)
 	{
 		// The following finish time is wrong if we aborted the move because of endstop or Z probe checks.
-		// However, following a move that checks endstops or the Z probe, we always wait fot the move to complete before we schedule another, so this doesn't matter.
+		// However, following a move that checks endstops or the Z probe, we always wait for the move to complete before we schedule another, so this doesn't matter.
 		const uint32_t finishTime = moveStartTime + clocksNeeded;	// calculate how long this move should take
 		Move& move = reprap.GetMove();
 		move.CurrentMoveCompleted();							// tell Move that the current move is complete
@@ -1629,40 +1629,7 @@ bool DDA::Free()
 int32_t DDA::GetStepsTaken(size_t drive) const
 {
 	const DriveMovement * const dmp = pddm[drive];
-	int32_t ret;
-	if (dmp == nullptr)
-	{
-		ret = 0;
-	}
-	else
-	{
-		const uint32_t ns = dmp->nextStep;
-		if (ns == 0)
-		{
-			ret = 0;						// not taken any steps yet
-		}
-		else
-		{
-			const uint32_t rss = dmp->reverseStartStep;
-			if (ns <= rss)
-			{
-				ret = (int32_t)ns;				// get number of steps already taken
-				if (!dmp->direction)			// if backwards movement
-				{
-					ret = -ret;					// invert sign
-				}
-			}
-			else
-			{
-				ret = (int)(2 * rss) - (int)ns;
-				if (dmp->direction)
-				{
-					ret = -ret;
-				}
-			}
-		}
-	}
-	return ret;
+	return (dmp != nullptr) ? dmp->GetNetStepsTaken() : 0;
 }
 
 // End
diff --git a/src/Movement/DriveMovement.cpp b/src/Movement/DriveMovement.cpp
index db191b6d..831d575b 100644
--- a/src/Movement/DriveMovement.cpp
+++ b/src/Movement/DriveMovement.cpp
@@ -251,6 +251,7 @@ bool DriveMovement::CalcNextStepTimeCartesianFull(const DDA &dda, bool live)
 pre(nextStep < totalSteps; stepsTillRecalc == 0)
 {
 	// Work out how many steps to calculate at a time.
+	// The last step before reverseStartStep must be single stepped to make sure that we don't reverse the direction too soon.
 	uint32_t shiftFactor = 0;		// assume single stepping
 	if (stepInterval < DDA::MinCalcIntervalCartesian)
 	{
@@ -339,6 +340,7 @@ bool DriveMovement::CalcNextStepTimeDeltaFull(const DDA &dda, bool live)
 pre(nextStep < totalSteps; stepsTillRecalc == 0)
 {
 	// Work out how many steps to calculate at a time.
+	// The last step before reverseStartStep must be single stepped to make sure that we don't reverse the direction too soon.
 	// The simulator suggests that at 200steps/mm, the minimum step pulse interval for 400mm/sec movement is 4.5us
 	uint32_t shiftFactor = 0;		// assume single stepping
 	if (stepInterval < DDA::MinCalcIntervalDelta)
diff --git a/src/Movement/DriveMovement.h b/src/Movement/DriveMovement.h
index 4c8e017c..36b44f95 100644
--- a/src/Movement/DriveMovement.h
+++ b/src/Movement/DriveMovement.h
@@ -43,6 +43,7 @@ public:
 	void ReduceSpeed(const DDA& dda, float inverseSpeedFactor);
 	void DebugPrint(char c, bool withDelta) const;
 	int32_t GetNetStepsLeft() const;
+	int32_t GetNetStepsTaken() const;
 
 	static void InitialAllocate(unsigned int num);
 	static int NumFree() { return numFree; }
@@ -121,14 +122,14 @@ public:
 };
 
 // Calculate and store the time since the start of the move when the next step for the specified DriveMovement is due.
-// Return true if there are more steps to do.
+// Return true if there are more steps to do. When finished, leave nextStep == totalSteps + 1.
 // This is also used for extruders on delta machines.
 // We inline this part to speed things up when we are doing double/quad/octal stepping.
 inline bool DriveMovement::CalcNextStepTimeCartesian(const DDA &dda, bool live)
 {
-	if (nextStep < totalSteps)
+	++nextStep;
+	if (nextStep <= totalSteps)
 	{
-		++nextStep;
 		if (stepsTillRecalc != 0)
 		{
 			--stepsTillRecalc;			// we are doing double/quad/octal stepping
@@ -142,12 +143,12 @@ inline bool DriveMovement::CalcNextStepTimeCartesian(const DDA &dda, bool live)
 }
 
 // Calculate the time since the start of the move when the next step for the specified DriveMovement is due
-// Return true if there are more steps to do
+// Return true if there are more steps to do. When finished, leave nextStep == totalSteps + 1.
 inline bool DriveMovement::CalcNextStepTimeDelta(const DDA &dda, bool live)
 {
-	if (nextStep < totalSteps)
+	++nextStep;
+	if (nextStep <= totalSteps)
 	{
-		++nextStep;
 		if (stepsTillRecalc != 0)
 		{
 			--stepsTillRecalc;			// we are doing double or quad stepping
@@ -164,15 +165,40 @@ inline bool DriveMovement::CalcNextStepTimeDelta(const DDA &dda, bool live)
 }
 
 // Return the number of net steps left for the move in the forwards direction.
+// We have already taken nextSteps - 1 steps, unless nextStep is zero.
 inline int32_t DriveMovement::GetNetStepsLeft() const
 {
-	const int32_t netStepsLeft =
-			(  (nextStep >= reverseStartStep || reverseStartStep >= totalSteps)
-			 ? totalSteps									// no reverse due, or we have already reversed
-			 : 2 * reverseStartStep - totalSteps			// we have yet to reverse
-			)
-			- nextStep + 1;
+	int32_t netStepsLeft;
+	if (reverseStartStep > totalSteps)		// if no reverse phase
+	{
+		netStepsLeft = (nextStep == 0) ? (int32_t)totalSteps : (int32_t)totalSteps - (int32_t)nextStep + 1;
+	}
+	else if (nextStep >= reverseStartStep)
+	{
+		netStepsLeft = (int32_t)totalSteps - (int32_t)nextStep + 1;
+	}
+	else
+	{
+		const int32_t totalNetSteps = (int32_t)(2 * reverseStartStep) - (int32_t)totalSteps - 2;
+		netStepsLeft = (nextStep == 0) ? totalNetSteps : totalNetSteps - (int32_t)nextStep + 1;
+	}
 	return (direction) ? netStepsLeft : -netStepsLeft;
 }
 
+// Return the number of net steps already taken for the move in the forwards direction.
+// We have already taken nextSteps - 1 steps, unless nextStep is zero.
+inline int32_t DriveMovement::GetNetStepsTaken() const
+{
+	int32_t netStepsTaken;
+	if (nextStep < reverseStartStep || reverseStartStep > totalSteps)				// if no reverse phase, or not started it yet
+	{
+		netStepsTaken = (nextStep == 0) ? 0 : (int32_t)nextStep - 1;
+	}
+	else
+	{
+		netStepsTaken = (int32_t)nextStep - (int32_t)(2 * reverseStartStep) + 2;	// allowing for direction having changed
+	}
+	return (direction) ? netStepsTaken : -netStepsTaken;
+}
+
 #endif /* DRIVEMOVEMENT_H_ */
diff --git a/src/Platform.cpp b/src/Platform.cpp
index 5d037a84..d62169aa 100644
--- a/src/Platform.cpp
+++ b/src/Platform.cpp
@@ -478,7 +478,6 @@ void Platform::Init()
 	{
 		extruderDrivers[extr] = (uint8_t)(extr + MinAxes);		// set up default extruder drive mapping
 		SetPressureAdvance(extr, 0.0);							// no pressure advance
-		filamentSensors[extr] = nullptr;						// no filament sensor
 	}
 
 #ifdef DUET_NG
@@ -1531,36 +1530,6 @@ void Platform::Spin()
 	}
 #endif
 
-	// Filament sensors
-	for (size_t extruder = 0; extruder < MaxExtruders; ++extruder)
-	{
-		if (filamentSensors[extruder] != nullptr)
-		{
-			GCodes& gCodes = reprap.GetGCodes();
-			const float extrusionCommanded = (float)reprap.GetMove().GetAccumulatedExtrusion(extruder)/driveStepsPerUnit[extruder + gCodes.GetTotalAxes()];
-																													// get and clear the Move extrusion commanded
-			if (reprap.GetPrintMonitor().IsPrinting() && !gCodes.IsPausing() && !gCodes.IsResuming() && !gCodes.IsPaused())
-			{
-				const FilamentSensorStatus fstat = filamentSensors[extruder]->Check(extrusionCommanded);
-				if (fstat != FilamentSensorStatus::ok && extrusionCommanded > 0.0)
-				{
-					if (reprap.Debug(moduleFilamentSensors))
-					{
-						debugPrintf("Filament error: extruder %u reports %s\n", extruder, FilamentSensor::GetErrorMessage(fstat));
-					}
-					else
-					{
-						gCodes.FilamentError(extruder, fstat);
-					}
-				}
-			}
-			else
-			{
-				filamentSensors[extruder]->Clear();
-			}
-		}
-	}
-
 	ClassReport(longWait);
 }
 
@@ -1799,6 +1768,12 @@ void Platform::InitialiseInterrupts()
 	NVIC_SetPriority(PIOE_IRQn, NvicPriorityPins);
 #endif
 
+#if SAM3XA
+	NVIC_SetPriority(UOTGHS_IRQn, NvicPriorityUSB);
+#endif
+#if SAM4E
+	NVIC_SetPriority(UDP_IRQn, NvicPriorityUSB);
+#endif
 	NVIC_SetPriority(TWI1_IRQn, NvicPriorityTwi);
 
 	// Interrupt for 4-pin PWM fan sense line
@@ -1814,7 +1789,7 @@ void Platform::InitialiseInterrupts()
 	// Set up the timeout of the regulator watchdog, and set up the backup watchdog if there is one
 	// The clock frequency for both watchdogs is 32768/128 = 256Hz
 	const uint16_t timeout = 32768/128;												// set watchdog timeout to 1 second (max allowed value is 4095 = 16 seconds)
-	wdt_init(WDT, WDT_MR_WDRSTEN, timeout,timeout);									// reset the processor on a watchdog fault
+	wdt_init(WDT, WDT_MR_WDRSTEN, timeout, timeout);								// reset the processor on a watchdog fault
 
 	active = true;							// this enables the tick interrupt, which keeps the watchdog happy
 }
@@ -2060,15 +2035,6 @@ void Platform::Diagnostics(MessageType mtype)
 	}
 #endif
 
-	// Filament sensors
-	for (size_t i = 0; i < MaxExtruders; ++i)
-	{
-		if (filamentSensors[i] != nullptr)
-		{
-			filamentSensors[i]->Diagnostics(mtype, i);
-		}
-	}
-
 	// Show current RTC time
 	Message(mtype, "Date/time: ");
 	struct tm timeInfo;
@@ -3370,39 +3336,12 @@ bool Platform::SetExtrusionAncilliaryPwmPin(int logicalPin)
 	return GetFirmwarePin(logicalPin, PinAccess::pwm, extrusionAncilliaryPwmFirmwarePin, extrusionAncilliaryPwmInvert);
 }
 
-// Filament sensor support
-// Get the filament sensor object for an extruder, or nullptr if there isn't one
-FilamentSensor *Platform::GetFilamentSensor(int extruder) const
-{
-	return (extruder >= 0 && extruder < (int)MaxExtruders) ? filamentSensors[extruder] : nullptr;
-}
-
-// Set the filament sensor type for an extruder, returning true if it has changed.
-// Passing newSensorType as 0 sets no sensor.
-bool Platform::SetFilamentSensorType(int extruder, int newSensorType)
-{
-	if (extruder >= 0 && extruder < (int)MaxExtruders)
-	{
-		FilamentSensor*& sensor = filamentSensors[extruder];
-		const int oldSensorType = (sensor == nullptr) ? 0 : sensor->GetType();
-		if (newSensorType != oldSensorType)
-		{
-			delete sensor;
-			sensor = FilamentSensor::Create(newSensorType);
-			return true;
-		}
-	}
-
-	return false;
-}
-
 // Get the firmware pin number for an endstop, or NoPin if it is out of range
 Pin Platform::GetEndstopPin(int endstop) const
 {
 	return (endstop >= 0 && endstop < (int)ARRAY_SIZE(endStopPins)) ? endStopPins[endstop] : NoPin;
 }
 
-
 #if SUPPORT_INKJET
 
 // Fire the inkjet (if any) in the given pattern
diff --git a/src/Platform.h b/src/Platform.h
index 66f68954..b3d10a53 100644
--- a/src/Platform.h
+++ b/src/Platform.h
@@ -575,9 +575,7 @@ public:
 	// User I/O and servo support
 	bool GetFirmwarePin(int logicalPin, PinAccess access, Pin& firmwarePin, bool& invert);
 
-	// Filament sensor support
-	FilamentSensor *GetFilamentSensor(int extruder) const;
-	bool SetFilamentSensorType(int extruder, int newSensorType);
+	// For filament sensor support
 	Pin GetEndstopPin(int endstop) const;			// Get the firmware pin number for an endstop
 
 //-------------------------------------------------------------------------------------------------------
@@ -689,7 +687,6 @@ private:
 	float driveStepsPerUnit[DRIVES];
 	float instantDvs[DRIVES];
 	float pressureAdvance[MaxExtruders];
-	FilamentSensor *filamentSensors[MaxExtruders];
 	float motorCurrents[DRIVES];					// the normal motor current for each stepper driver
 	float motorCurrentFraction[DRIVES];				// the percentages of normal motor current that each driver is set to
 	AxisDriversConfig axisDrivers[MaxAxes];			// the driver numbers assigned to each axis
diff --git a/src/RepRap.cpp b/src/RepRap.cpp
index d8de26a8..294a4555 100644
--- a/src/RepRap.cpp
+++ b/src/RepRap.cpp
@@ -45,6 +45,10 @@ extern "C" void hsmciIdle()
 	}
 #endif
 
+	if (reprap.GetSpinningModule() != moduleFilamentSensors)
+	{
+		FilamentSensor::Spin(false);
+	}
 }
 
 // RepRap member functions.
@@ -217,6 +221,10 @@ void RepRap::Spin()
 	DuetExpansion::Spin(true);
 #endif
 
+	spinningModule = moduleFilamentSensors;
+	ticksInSpinState = 0;
+	FilamentSensor::Spin(true);
+
 	spinningModule = noModule;
 	ticksInSpinState = 0;
 
@@ -264,6 +272,7 @@ void RepRap::Diagnostics(MessageType mtype)
 	heat->Diagnostics(mtype);
 	gCodes->Diagnostics(mtype);
 	network->Diagnostics(mtype);
+	FilamentSensor::Diagnostics(mtype);
 }
 
 // Turn off the heaters, disable the motors, and deactivate the Heat and Move classes. Leave everything else working.
@@ -288,7 +297,7 @@ void RepRap::EmergencyStop()
 	}
 
 	// We do this twice, to avoid an interrupt switching a drive back on. move->Exit() should prevent interrupts doing this.
-	for(int i = 0; i < 2; i++)
+	for (int i = 0; i < 2; i++)
 	{
 		move->Exit();
 		for (size_t drive = 0; drive < DRIVES; drive++)
diff --git a/src/RepRapFirmware.h b/src/RepRapFirmware.h
index 327714ae..f4ba010f 100644
--- a/src/RepRapFirmware.h
+++ b/src/RepRapFirmware.h
@@ -211,15 +211,16 @@ const uint32_t NvicPriorityWatchdog = 0;		// watchdog has highest priority (SAM4
 
 const uint32_t NvicPriorityUart = 1;			// UART is next to avoid character loss
 const uint32_t NvicPrioritySystick = 2;			// systick kicks the watchdog and starts the ADC conversions, so must be quite high
-const uint32_t NvicPriorityStep = 3;			// step interrupt is next highest, it can preempt most other interrupts
+const uint32_t NvicPriorityPins = 3;			// priority for GPIO pin interrupts - filament sensors must be higher than step
+const uint32_t NvicPriorityStep = 4;			// step interrupt is next highest, it can preempt most other interrupts
+const uint32_t NvicPriorityUSB = 5;				// USB interrupt
 
 #if !defined(DUET_NG) && !defined(__RADDS__)
-const uint32_t NvicPriorityNetworkTick = 4;		// priority for network tick interrupt
-const uint32_t NvicPriorityEthernet = 4;		// priority for Ethernet interface
+const uint32_t NvicPriorityNetworkTick = 5;		// priority for network tick interrupt
+const uint32_t NvicPriorityEthernet = 5;		// priority for Ethernet interface
 #endif
 
-const uint32_t NvicPrioritySpi = 5;				// SPI used for network transfers on Duet WiFi/Duet vEthernet
-const uint32_t NvicPriorityPins = 6;			// priority for GPIO pin interrupts
+const uint32_t NvicPrioritySpi = 6;				// SPI used for network transfers on Duet WiFi/Duet vEthernet
 const uint32_t NvicPriorityTwi = 7;				// TWI used to read endstop and other inputs on the DueXn
 
 #endif
diff --git a/src/Version.h b/src/Version.h
index e58614e1..dd647ab4 100644
--- a/src/Version.h
+++ b/src/Version.h
@@ -9,11 +9,11 @@
 #define SRC_VERSION_H_
 
 #ifndef VERSION
-# define VERSION "1.19RC7"
+# define VERSION "1.19"
 #endif
 
 #ifndef DATE
-# define DATE "2017-08-11"
+# define DATE "2017-08-14"
 #endif
 
 #define AUTHORS "reprappro, dc42, chrishamm, t3p3, dnewman"