Version 2.01beta1

Bug fixes:
- When using a mixing extruder, the feed rate for extruder-only moves was incorrect
- If additional axes were not created in the order UVWABC then incorrect homing files might be run (thanks chrishamm)
- On the Duet Maestro, the 7th stepper step/dir pin numbers were swapped
- If you paused a print during a G2/G3 arc move, on resuming it the arc centre was at the wrong place. This release defers the pause until the arc move is completed.
- If a command that interrogated the network (e.g. M122 on the Duet WiFi) was sent from USB, PanelDue or another non-network channel, the network subsystem could be accessed by multiple tasks concurrently, causing network disconnections or other errors
- When using a bltouch, between probe points the pin retracted, deployed and retracted again
- M206 with no parameters didn't report the current axis offsets
- During heating, the firmware returned M408 S0 responses to the PanelDue port even if the last request was M408 S2
- Fixed VBUS detection (thanks chrishamm)
- If the resume threshold in the M911 command was set higher than the supply voltage then the save-on-power-off mechanism never got primed. It will now prime at thwe auto-save threshold plus 0.5V or the resume threshold, whichever is lower.
- Fixed "2dtstc2diva=u" in debug printout
- Where a G- or M-code command parameter was supposed to accept unsigned values only, if a negative value was supplied then it was accepted and converted to a large unsigned value

New features and changed behaviour:
- If the firmware gets stuck in a spin loop, the RTOS builds now discard LR and 16 stack dwords in order to get more useful information from the stack trace
- Increased M999 delay to 1 second
- The report generated by M122 now includes a list of mutexes and their owners
- Added SW_ENC pin on CONN_SD to available GPIO ports (thanks chrishamm)

37 files changed, 429 insertions, 159 deletions

diff --git a/src/BugList.txt b/src/BugList.txt
index 619a7bcd..e920e51f 100644
--- a/src/BugList.txt
+++ b/src/BugList.txt
@@ -189,17 +189,58 @@ Fixes in release 2.0:
 - [done] can't load filaments because DWC doesn't give the option unless a filament is already loaded
 - look at wifi disconnect issue, https://forum.duet3d.com/topic/4341/wifi-module-keeps-disconnecting/64
 
-Planned for 2.01:
+Planned for 2.01/1.21.2:
+
+WiFi:
+- [resolve library incompatibility] New ESP8266 SDK
+- [done] check what's new in Arduino ESP 2.4.1
+
+Bug fixes/investigations:
+- [done, test] sqrt(2) error factor in extrusion-only moves, see Michael's email
+- [done] Homing wrong if axes not labeled sequentially, see Christian's email of 18/6/18
+- [done, test] Fix "2dtstc2diva=u" in debug printout, https://forum.duet3d.com/topic/3139/high-level-of-steperrors-what-can-cause-them/5
+- [done, test] when stuck in spin loop, in RTOS build discard LR and 16 stack dwords, they are within FreeRTOS
+- [done, test] Rotating magnet monitor reports "allowed movement 2147483647% to 160%" in M591 response, see Tony's email (caused by R-1 in M591 command)
+- [done, test] Duet Maestro 7th stepper step/dir pin numbers swapped
+- [done, test] Pausing during an arc move, on resume the arc centre is at the wrong place. Temporarily don't allow pause during an arc move?
+- [done] WiFi needs a mutex on SendCommand because WiFiInterface::Diagnostics and SetHostName can be called from outside the Network task. Similarly for W5500 Ethernet interface.
+- [done, test] bltouch retracts, deploys, retracts between probes. Is the M280 retract command being queued until the end of the movement command?
+- [checked, ok] Check that in M569, T3 is equivalent to T3:3:3:3, see https://forum.duet3d.com/topic/5579/expansion-stepper-breakout-tb6600
+- [done, test] M206 with no parameters to report axis offsets
+- [done] During heating, returns M408 S0 responses to PanelDue port even if the last request was M408 S2, see https://forum.duet3d.com/topic/5761/printer-is-sending-m408-s0-when-heating.
+- [done in CoreNG] Fix VBUS detection in CoreNG, see chrishamm's branch
+- [done] Add SW_ENC pin on CONN_SD to available GPIO ports
+- [done] Increased M999 delay to 1 second
+- [done] If M911 resume threshold is set too high, save-on-power-off never primes itself
+
+- Test gcode file that pauses between parts, https://forum.duet3d.com/topic/5702/printer-keeps-pausing-during-print/15
+- Doesn't find DueX5 after M999 reset? https://forum.duet3d.com/topic/5713/duet2-with-2-0-rtos-looses-duex5-on-reset
+- stuck in spin loop, https://forum.duet3d.com/topic/5674/damned-crash-stuck-in-spin-loop
+- step errors, see https://forum.duet3d.com/topic/3139/high-level-of-steperrors-what-can-cause-them/5
+- Investigate failed .BMP conversion, https://forum.duet3d.com/topic/5623/boot-logo-corruption-in-1-21/2
+- Duet Maestro default to TMC2224 drivers on expansion? How to detect them?
+- M28 and M29 in a macro, https://forum.duet3d.com/topic/5642/filament-load-macro-writing-to-file-in-sys. Move fileBeingWritten to GCodeBuffer, get rid of writingFileDirectory.
+- Is there a kink during auto tuning? https://forum.duet3d.com/topic/5582/hot-end-auto-tuning-failed-due. Could explain oddly low dead times from auto tuning.
+- Does bltouch need a default recovery time to allow it to deploy? (probably not)
+- Should bltouch use digital probe mode? Some users having problems with P25 in G31 command.
+- Test Duet 06/085 DHCP problem again, see https://forum.duet3d.com/topic/5572/it-s-out-reprapfirmware-2-0-and-1-21-1-released/16 for config.g files
+- Retry after SD card error?
+
+Other:
+- @wilriker PR for M106 PWM limit
+- [done, test] display mutex owners in task diagnostics
+
+Planned for 2.02:
+- WiFi continuous auto reconnect, or extra M552 parameter? See https://forum.duet3d.com/topic/5765/wifi-module-auto-reconnect
+- Better dead time measurement during auto tuning. Measure both turn-on and turn-off?
 - Bezier speed curves or other S-curve acceleration, e.g. look at https://github.com/MarlinFirmware/Marlin/pull/10373/files
-- Option to send M280 servo commands just a few times instead of continuously, for E3D and BLTouch
+- Option to send M280 servo commands just a few times instead of continuously, for E3D
 - Recovery from SD card errors during a print (Dan)
 - Danny's modified SCARA kinematics (workpiece is on a plate, extruder is fixed)
 - Laser support via G1 S parameter, see https://forum.duet3d.com/topic/4702/laser-cnc-support-in-rrf-gcode-semantics/4
 - Look at pushover notification support, https://forum.duet3d.com/topic/169/notification-via-pushover-or-other-service/45
 - M3 R parameter so it can restore the spinder/laser after a pause (https://forum.duet3d.com/topic/5418/cnc-laser-m3-unpause-r-parameter)
 - M81: don't give low voltage warnings when main power has just been turned off
-- Does bltouch need a default recovery time?
-- Should bltouch use digital probe mode? Some users having problems with P25 in G31 command.
 - M584 when assigning a drive, unmap any existing assignment. Also allow an axis to be mapped to driver -1.
 - Add S4 option to G1 command, like S1 but no endstop checks (needed for CoreXY, CoreXZ)
 - CNC: look at G17/18/19, see https://forum.duet3d.com/topic/4669/ooznest-workbee-screw-driven
@@ -208,8 +249,9 @@ Planned for 2.01:
 - Apostrophe in quoted filename: can we make apostrophe special in SSIDs/passwords but not filenames?
 - If wifi module gets stuck in starting or changing mode state, reset it again
 - If wifi disconnects when in client mode, keep retrying the connection
+- M140 command to set default bed heaters for M140 S commands (e.g. M140 P0:1:2)
 
-Other (some of these may be in 2.01):
+Other (some of these may be in 2.02):
 - Update PanelDue firmware via Duet
 - Use Heat task to read DHT sensors?
 - Add option R4 to M915 command, to do an emergency stop (useful for Z motor)
@@ -282,16 +324,11 @@ p->ref == 1 in WiFi
 
 Later versions:
 
-- Multiple bed heaters, https://www.duet3d.com/forum/thread.php?pid=33903#p33903
-- Use M140H1:2:3 to set multiple bed heater numbers
 - Check https://www.duet3d.com/forum/thread.php?pid=33951#p33951
 
 - Option to not broadcast SSID?
-- On file read error during SD card print, treat like a temperature fault
 - Support faster homing by using interrupts to check homing switch states
 - Allow manual bed probing to be aborted
-- Implement G1 S4? (like S2 but always relative)
-- Add work coordinates? https://www.duet3d.com/forum/thread.php?pid=27128#p27128
 - Don't do pressure advance during accel/decel of sequences of short segments
 - Arc move with same finish and start coordinates to do complete circle
 - Add T parameter to M207
diff --git a/src/DuetM/Pins_DuetM.h b/src/DuetM/Pins_DuetM.h
index 50cf453a..3825e32b 100644
--- a/src/DuetM/Pins_DuetM.h
+++ b/src/DuetM/Pins_DuetM.h
@@ -67,8 +67,8 @@ constexpr size_t NUM_SERIAL_CHANNELS = 2;			// The number of serial IO channels
 // Drivers
 constexpr Pin GlobalTmcEnablePin = 1;				// The pin that drives ENN of all drivers
 constexpr Pin ENABLE_PINS[DRIVES] = { NoPin, NoPin, NoPin, NoPin, NoPin, 63, 61 };
-constexpr Pin STEP_PINS[DRIVES] = { 56, 38, 64, 40, 41, 67, 60 };
-constexpr Pin DIRECTION_PINS[DRIVES] = { 54, 8, 30, 33, 42, 18, 57 };
+constexpr Pin STEP_PINS[DRIVES] = { 56, 38, 64, 40, 41, 67, 57 };
+constexpr Pin DIRECTION_PINS[DRIVES] = { 54, 8, 30, 33, 42, 18, 60 };
 constexpr Pin DriverMuxPins[3] = { 50, 52, 53 };	// Pins that control the UART multiplexer, LSB first
 
 // Endstops
diff --git a/src/DuetM/TMC22xx.cpp b/src/DuetM/TMC22xx.cpp
index a02c4ff0..5f373c26 100644
--- a/src/DuetM/TMC22xx.cpp
+++ b/src/DuetM/TMC22xx.cpp
@@ -44,7 +44,7 @@ constexpr uint32_t GCONF_INT_RSENSE = 1 << 1;				// use internal sense resistors
 constexpr uint32_t GCONF_SPREAD_CYCLE = 1 << 2;				// use spread cycle mode (else stealthchop mode)
 constexpr uint32_t GCONF_REV_DIR = 1 << 3;					// reverse motor direction
 constexpr uint32_t GCONF_INDEX_OTPW = 1 << 4;				// INDEX output shows over temperature warning (else it shows first microstep position)
-constexpr uint32_t GCONF_INDEX_PULSE = 1 << 5;				// INDEX output shows pulses form internal pulse generator, else as set by GCONF_INDEX_OTPW
+constexpr uint32_t GCONF_INDEX_PULSE = 1 << 5;				// INDEX output shows pulses from internal pulse generator, else as set by GCONF_INDEX_OTPW
 constexpr uint32_t GCONF_UART = 1 << 6;						// PDN_UART used for UART interface (else used for power down)
 constexpr uint32_t GCONF_MSTEP_REG = 1 << 7;				// microstep resolution set by MSTEP register (else by MS1 and MS2 pins)
 constexpr uint32_t GCONF_MULTISTEP_FILT = 1 << 8;			// pulse generation optimised for >750Hz full stepping frequency
diff --git a/src/DuetNG/Pins_DuetNG.h b/src/DuetNG/Pins_DuetNG.h
index 53624560..3aa83879 100644
--- a/src/DuetNG/Pins_DuetNG.h
+++ b/src/DuetNG/Pins_DuetNG.h
@@ -162,7 +162,8 @@ constexpr Pin ROLAND_RTS_PIN = xx;											// Expansion pin 12, PA13_RXD1
 // This is the mapping from logical pins 60+ to firmware pin numbers
 constexpr Pin SpecialPinMap[] =
 {
-	24, 97, 98, 99															// We allow CS5-CS8 to be used because few users need >4 thermocouples or RTDs
+	24, 97, 98, 99,															// We allow CS5-CS8 to be used because few users need >4 thermocouples or RTDs
+	7																		// SW_ENC on CONN_SD
 };
 constexpr Pin DueX5GpioPinMap[] = { 211, 210, 209, 208 };					// Pins 100-103 map to GPIO 1-4 on DueX5
 // We also allow pins 120-135 to be used if there is an additional SX1509B expander
diff --git a/src/FilamentMonitors/FilamentMonitor.cpp b/src/FilamentMonitors/FilamentMonitor.cpp
index 4c5254c2..a9482654 100644
--- a/src/FilamentMonitors/FilamentMonitor.cpp
+++ b/src/FilamentMonitors/FilamentMonitor.cpp
@@ -71,7 +71,7 @@ bool FilamentMonitor::ConfigurePin(GCodeBuffer& gb, const StringRef& reply, Inte
 // Static initialisation
 /*static*/ void FilamentMonitor::InitStatic()
 {
-	filamentSensorsMutex.Create();
+	filamentSensorsMutex.Create("FilamentSensors");
 }
 
 // Handle M591
diff --git a/src/GCodes/GCodeInput.cpp b/src/GCodes/GCodeInput.cpp
index 35371c26..2e7383db 100644
--- a/src/GCodes/GCodeInput.cpp
+++ b/src/GCodes/GCodeInput.cpp
@@ -201,7 +201,7 @@ void NetworkGCodeInput::Put(MessageType mtype, const char *buf)
 
 NetworkGCodeInput::NetworkGCodeInput() : RegularGCodeInput()
 {
-	bufMutex.Create();
+	bufMutex.Create("NetworkGCodeInput");
 }
 
 // Fill a GCodeBuffer with the last available G-code
diff --git a/src/GCodes/GCodeMachineState.h b/src/GCodes/GCodeMachineState.h
index 88404df0..323ba860 100644
--- a/src/GCodes/GCodeMachineState.h
+++ b/src/GCodes/GCodeMachineState.h
@@ -50,23 +50,25 @@ enum class GCodeState : uint8_t
 	stopping,
 	sleeping,
 
-	// These next 7 must be contiguous
+	// These next 9 must be contiguous
 	gridProbing1,
 	gridProbing2a,
 	gridProbing2b,
 	gridProbing3,
 	gridProbing4,
+	gridProbing4a,
 	gridProbing5,
 	gridProbing6,
 	gridProbing7,
 
-	// These next 9 must be contiguous
+	// These next 10 must be contiguous
 	probingAtPoint0,
 	probingAtPoint1,
 	probingAtPoint2a,
 	probingAtPoint2b,
 	probingAtPoint3,
 	probingAtPoint4,
+	probingAtPoint4a,
 	probingAtPoint5,
 	probingAtPoint6,
 	probingAtPoint7,
diff --git a/src/GCodes/GCodes.cpp b/src/GCodes/GCodes.cpp
index 47f7947e..0fd79e68 100644
--- a/src/GCodes/GCodes.cpp
+++ b/src/GCodes/GCodes.cpp
@@ -269,6 +269,19 @@ float GCodes::FractionOfFilePrinted() const
 	return (float)(fileBeingPrinted.GetPosition() - bytesCached) / (float)len;
 }
 
+// Return the current position of the file being printed in bytes
+FilePosition GCodes::GetFilePosition() const
+{
+	const FileData& fileBeingPrinted = fileGCode->OriginalMachineState().fileState;
+	if (!fileBeingPrinted.IsLive())
+	{
+		return 0;
+	}
+
+    const FilePosition bytesCached = fileGCode->IsDoingFileMacro() ? 0: fileInput->BytesCached();
+    return fileBeingPrinted.GetPosition() - bytesCached;
+}
+
 // Start running the config file
 // We use triggerCGode as the source to prevent any triggers being executed until we have finished
 bool GCodes::RunConfigFile(const char* fileName)
@@ -859,13 +872,7 @@ void GCodes::RunStateMachine(GCodeBuffer& gb, const StringRef& reply)
 				g30zHeightErrorSum += g30zHeightError;
 			}
 
-			// Move back up to the dive height
-			moveBuffer.SetDefaults();
-			moveBuffer.coords[Z_AXIS] = platform.GetZProbeStartingHeight();
-			moveBuffer.feedRate = platform.GetZProbeTravelSpeed();
-			NewMoveAvailable(1);
 			gb.AdvanceState();
-
 			if (platform.GetZProbeType() == ZProbeType::blTouch)
 			{
 				DoFileMacro(gb, RETRACTPROBE_G, false);			// bltouch needs to be retracted when it triggers
@@ -873,6 +880,15 @@ void GCodes::RunStateMachine(GCodeBuffer& gb, const StringRef& reply)
 		}
 		break;
 
+	case GCodeState::gridProbing4a:	// ready to lift the probe after probing the current grid probe point
+		// Move back up to the dive height
+		moveBuffer.SetDefaults();
+		moveBuffer.coords[Z_AXIS] = platform.GetZProbeStartingHeight();
+		moveBuffer.feedRate = platform.GetZProbeTravelSpeed();
+		NewMoveAvailable(1);
+		gb.AdvanceState();
+		break;
+
 	case GCodeState::gridProbing5:	// finished probing a point and moved back to the dive height
 		if (LockMovementAndWaitForStandstill(gb))
 		{
@@ -1131,20 +1147,23 @@ void GCodes::RunStateMachine(GCodeBuffer& gb, const StringRef& reply)
 				}
 			}
 
-			// Move back up to the dive height before we change anything, in particular before we adjust leadscrews
-			moveBuffer.SetDefaults();
-			moveBuffer.coords[Z_AXIS] = platform.GetZProbeStartingHeight();
-			moveBuffer.feedRate = platform.GetZProbeTravelSpeed();
-			NewMoveAvailable(1);
 			gb.AdvanceState();
-
 			if (platform.GetZProbeType() == ZProbeType::blTouch)
 			{
-				DoFileMacro(gb, RETRACTPROBE_G, false);						// bltouch needs to be retracted when it triggers
+				DoFileMacro(gb, RETRACTPROBE_G, false);							// bltouch needs to be retracted when it triggers
 			}
 		}
 		break;
 
+	case GCodeState::probingAtPoint4a:
+		// Move back up to the dive height before we change anything, in particular before we adjust leadscrews
+		moveBuffer.SetDefaults();
+		moveBuffer.coords[Z_AXIS] = platform.GetZProbeStartingHeight();
+		moveBuffer.feedRate = platform.GetZProbeTravelSpeed();
+		NewMoveAvailable(1);
+		gb.AdvanceState();
+		break;
+
 	case GCodeState::probingAtPoint5:
 		// Here when we have moved the head back up to the dive height
 		if (LockMovementAndWaitForStandstill(gb))
@@ -2608,7 +2627,7 @@ const char* GCodes::DoArcMove(GCodeBuffer& gb, bool clockwise)
 // Adjust the move parameters to account for segmentation and/or part of the move having been done already
 void GCodes::FinaliseMove(GCodeBuffer& gb)
 {
-	moveBuffer.canPauseAfter = (moveBuffer.endStopsToCheck == 0);
+	moveBuffer.canPauseAfter = (moveBuffer.endStopsToCheck == 0) && !doingArcMove;		// pausing during an arc move isn't save because the arc centre get recomputed incorrectly when we resume
 	moveBuffer.filePos = (&gb == fileGCode) ? gb.GetFilePosition(fileInput->BytesCached()) : noFilePosition;
 
 	if (totalSegments > 1)
@@ -2663,6 +2682,10 @@ bool GCodes::ReadMove(RawMove& m)
 			}
 		}
 		m.proportionLeft = 0.0;
+		if (doingArcMove)
+		{
+			m.canPauseAfter = true;			// we can pause after the final segment of an arc move
+		}
 		ClearMove();
 	}
 	else
@@ -4721,7 +4744,7 @@ void GCodes::CheckReportDue(GCodeBuffer& gb, const StringRef& reply) const
 			if (lastAuxStatusReportType >= 0)
 			{
 				// Send a standard status response for PanelDue
-				OutputBuffer * const statusBuf = GenerateJsonStatusResponse(0, -1, ResponseSource::AUX);
+				OutputBuffer * const statusBuf = GenerateJsonStatusResponse(lastAuxStatusReportType, -1, ResponseSource::AUX);
 				if (statusBuf != nullptr)
 				{
 					platform.AppendAuxReply(statusBuf, true);
diff --git a/src/GCodes/GCodes.h b/src/GCodes/GCodes.h
index 29190528..0c0de8ce 100644
--- a/src/GCodes/GCodes.h
+++ b/src/GCodes/GCodes.h
@@ -145,6 +145,7 @@ public:
 	void GetCurrentCoordinates(const StringRef& s) const;				// Write where we are into a string
 	bool DoingFileMacro() const;										// Or still busy processing a macro file?
 	float FractionOfFilePrinted() const;								// Get fraction of file printed
+	FilePosition GetFilePosition() const;								// Return the current position of the file being printed in bytes
 	void Diagnostics(MessageType mtype);								// Send helpful information out
 
 	bool RunConfigFile(const char* fileName);							// Start running the config file
@@ -294,7 +295,7 @@ private:
 	void FinishWrite(GCodeBuffer& gb);											// Finish writing to the file and respond
 	bool SendConfigToLine();													// Deal with M503
 
-	GCodeResult OffsetAxes(GCodeBuffer& gb);									// Set offsets
+	GCodeResult OffsetAxes(GCodeBuffer& gb, const StringRef& reply);			// Set/report offsets
 
 #if SUPPORT_WORKPLACE_COORDINATES
 	GCodeResult GetSetWorkplaceCoordinates(GCodeBuffer& gb, const StringRef& reply, bool compute);	// Set workspace coordinates
diff --git a/src/GCodes/GCodes2.cpp b/src/GCodes/GCodes2.cpp
index af298d35..a87c8d7a 100644
--- a/src/GCodes/GCodes2.cpp
+++ b/src/GCodes/GCodes2.cpp
@@ -1928,7 +1928,7 @@ bool GCodes::HandleMcode(GCodeBuffer& gb, const StringRef& reply)
 		break;
 
 	case 206: // Offset axes
-		result = OffsetAxes(gb);
+		result = OffsetAxes(gb, reply);
 		break;
 
 	case 207: // Set firmware retraction details
@@ -2511,7 +2511,7 @@ bool GCodes::HandleMcode(GCodeBuffer& gb, const StringRef& reply)
 		{
 			const int type = gb.Seen('S') ? gb.GetIValue() : 0;
 			const int seq = gb.Seen('R') ? gb.GetIValue() : -1;
-			if (&gb == auxGCode)
+			if (&gb == auxGCode && (type == 0 || type == 2))
 			{
 				lastAuxStatusReportType = type;
 			}
@@ -3800,7 +3800,10 @@ bool GCodes::HandleMcode(GCodeBuffer& gb, const StringRef& reply)
 		{
 			if (reprap.GetScanner().IsEnabled())
 			{
-				result = GetGCodeResultFromFinished(reprap.GetScanner().Register());
+				reprap.GetScanner().Register();
+
+				// The Scanner module will attempt to run a macro via this G-code source so we're not done yet
+				result = GCodeResult::notFinished;
 			}
 			else
 			{
@@ -4163,7 +4166,7 @@ bool GCodes::HandleMcode(GCodeBuffer& gb, const StringRef& reply)
 		break;
 
 	case 999:
-		result = DoDwellTime(gb, 500);		// wait half a second to allow the response to be sent back to the web server, otherwise it may retry
+		result = DoDwellTime(gb, 1000);		// wait a second to allow the response to be sent back to the web server, otherwise it may retry
 		if (result != GCodeResult::notFinished)
 		{
 			reprap.EmergencyStop();			// this disables heaters and drives - Duet WiFi pre-production boards need drives disabled here
diff --git a/src/GCodes/GCodes3.cpp b/src/GCodes/GCodes3.cpp
index 05cd8948..fc33b569 100644
--- a/src/GCodes/GCodes3.cpp
+++ b/src/GCodes/GCodes3.cpp
@@ -173,8 +173,9 @@ GCodeResult GCodes::SetPositions(GCodeBuffer& gb)
 // Offset the axes by the X, Y, and Z amounts in the M226 code in gb. The actual movement occurs on the next move command.
 // It's not clear from the description in the reprap.org wiki whether offsets are cumulative or not. We now assume they are not.
 // Note that M206 offsets are actually negative offsets.
-GCodeResult GCodes::OffsetAxes(GCodeBuffer& gb)
+GCodeResult GCodes::OffsetAxes(GCodeBuffer& gb, const StringRef& reply)
 {
+	bool seen = false;
 	for (size_t axis = 0; axis < numVisibleAxes; axis++)
 	{
 		if (gb.Seen(axisLetters[axis]))
@@ -185,6 +186,22 @@ GCodeResult GCodes::OffsetAxes(GCodeBuffer& gb)
 			axisOffsets[axis]
 #endif
 						 = -(gb.GetFValue() * distanceScale);
+			seen = true;
+		}
+	}
+
+	if (!seen)
+	{
+		reply.printf("Axis offsets:");
+		for (size_t axis = 0; axis < numVisibleAxes; axis++)
+		{
+			reply.catf(" %c%.2f", axisLetters[axis],
+#if SUPPORT_WORKPLACE_COORDINATES
+				-(double)(workplaceCoordinates[0][axis]/distanceScale)
+#else
+				-(double)(axisOffsets[axis]/distanceScale)
+#endif
+													 );
 		}
 	}
 
@@ -230,7 +247,7 @@ GCodeResult GCodes::GetSetWorkplaceCoordinates(GCodeBuffer& gb, const StringRef&
 				reply.printf("Origin of workplace %" PRIu32 ":", cs);
 				for (size_t axis = 0; axis < numVisibleAxes; axis++)
 				{
-					reply.catf(" %c%.2f", axisLetters[axis], (double)workplaceCoordinates[cs - 1][axis]);
+					reply.catf(" %c%.2f", axisLetters[axis], (double)(workplaceCoordinates[cs - 1][axis]/distanceScale));
 				}
 			}
 			return GCodeResult::ok;
diff --git a/src/Heating/Sensors/DhtSensor.cpp b/src/Heating/Sensors/DhtSensor.cpp
index 15da14bb..7340b951 100644
--- a/src/Heating/Sensors/DhtSensor.cpp
+++ b/src/Heating/Sensors/DhtSensor.cpp
@@ -144,7 +144,7 @@ DhtSensorHardwareInterface *DhtSensorHardwareInterface::Create(unsigned int rela
 
 /*static*/ void DhtSensorHardwareInterface::InitStatic()
 {
-	dhtMutex.Create();
+	dhtMutex.Create("DHT");
 }
 
 /*static*/ TemperatureError DhtSensorHardwareInterface::GetTemperatureOrHumidity(unsigned int relativeChannel, float& t, bool wantHumidity)
diff --git a/src/Libraries/General/SafeStrtod.cpp b/src/Libraries/General/SafeStrtod.cpp
index 0701bc72..1c27a01f 100644
--- a/src/Libraries/General/SafeStrtod.cpp
+++ b/src/Libraries/General/SafeStrtod.cpp
@@ -4,18 +4,22 @@
  *  Created on: 4 Apr 2018
  *      Author: David
  *
- * This is a replacement for strtof() in the C standard library. That version has two problems:
+ * This is a replacement for strtod() and strtof() in the C standard library. Those versions have two problems:
  * 1. It is not reentrant. We can make it so by defining configUSE_NEWLIB_REENTRANT in FreeRTOS, but that makes the tasks much bigger.
  * 2. It allocates and releases heap memory, which is not nice.
  *
  * Limitations of this version
  * 1. Rounding to nearest double may not always be correct.
- * 2. May not handle overflow for stupidly large numbers correctly.
+ * 2. Does not handle overflow for stupidly large numbers correctly.
  */
 
 #include <cctype>
 #include <cmath>
 #include <climits>
+#include <cstdlib>
+
+#include "SafeStrtod.h"
+#undef strtoul		// Undo the macro definition of strtoul in SafeStrtod.h so that we can call it in this file
 
 double SafeStrtod(const char *s, const char **p)
 {
@@ -131,4 +135,40 @@ float SafeStrtof(const char *s, const char **p)
 	return (float)SafeStrtod(s, p);
 }
 
+unsigned long SafeStrtoul(const char *s, const char **endptr, int base)
+{
+	// strtoul() accepts a leading minus-sign, which we don't want to allow
+	while (*s == ' ' || *s == '\t')
+	{
+		++s;
+	}
+	if (*s == '-')
+	{
+		if (endptr != nullptr)
+		{
+			*endptr = s;
+		}
+		return 0;
+	}
+	return strtoul(s, const_cast<char**>(endptr), base);
+}
+
+unsigned long SafeStrtoul(char *s, char **endptr, int base)
+{
+	// strtoul() accepts a leading minus-sign, which we don't want to allow
+	while (*s == ' ' || *s == '\t')
+	{
+		++s;
+	}
+	if (*s == '-')
+	{
+		if (endptr != nullptr)
+		{
+			*endptr = s;
+		}
+		return 0;
+	}
+	return strtoul(s, endptr, base);
+}
+
 // End
diff --git a/src/Libraries/General/SafeStrtod.h b/src/Libraries/General/SafeStrtod.h
index ae83228c..d1dc1d5c 100644
--- a/src/Libraries/General/SafeStrtod.h
+++ b/src/Libraries/General/SafeStrtod.h
@@ -16,15 +16,8 @@ inline long SafeStrtol(const char *s, const char **endptr = nullptr, int base =
 	return strtol(s, const_cast<char**>(endptr), base);
 }
 
-inline unsigned long SafeStrtoul(const char *s, const char **endptr = nullptr, int base = 10)
-{
-	return strtoul(s, const_cast<char**>(endptr), base);
-}
-
-inline unsigned long SafeStrtoul(char *s, char **endptr = nullptr, int base = 10)
-{
-	return strtoul(s, endptr, base);
-}
+unsigned long SafeStrtoul(const char *s, const char **endptr = nullptr, int base = 10);
+unsigned long SafeStrtoul(char *s, char **endptr = nullptr, int base = 10);
 
 #define strtod(s, p) Do_not_use_strtod_use_SafeStrtod_instead
 #define strtof(s, p) Do_not_use_strtof_use_SafeStrtof_instead
diff --git a/src/Libraries/General/SafeVsnprintf.cpp b/src/Libraries/General/SafeVsnprintf.cpp
index 0952c243..9b171ce0 100644
--- a/src/Libraries/General/SafeVsnprintf.cpp
+++ b/src/Libraries/General/SafeVsnprintf.cpp
@@ -15,7 +15,7 @@
 	Changes for the FreeRTOS ports:
 
 	- The dot in "%-8.8s"
-	- The specifiers 'l' (long) and 'L' (long long)
+	- The specifiers 'l' (long) and 'll' (long long)
 	- The specifier 'u' for unsigned
 	- Dot notation for IP addresses:
 	  sprintf("IP = %xip\n", 0xC0A80164);
@@ -546,14 +546,15 @@ static void tiny_print(SStringBuf& apBuf, const char *format, va_list args)
 		if (ch == 'l')
 		{
 			ch = *format++;
-			apBuf.flags.long32 = 1;
-			// Makes no difference as u32 == long
-		}
-		if (ch == 'L')
-		{
-			ch = *format++;
-			apBuf.flags.long64 = 1;
-			// Does make a difference
+			if (ch == 'l')
+			{
+				ch = *format++;
+				apBuf.flags.long64 = 1;
+			}
+			else
+			{
+				apBuf.flags.long32 = 1;
+			}
 		}
 
 		if (ch == 'f' || ch == 'e' || ch == 'F' || ch == 'E')
diff --git a/src/Libraries/General/StringRef.h b/src/Libraries/General/StringRef.h
index d6d84a31..74a52ddd 100644
--- a/src/Libraries/General/StringRef.h
+++ b/src/Libraries/General/StringRef.h
@@ -54,7 +54,7 @@ public:
 	const char *c_str() const { return storage; }
 	size_t strlen() const { return Strnlen(storage, Len); }
 	bool IsEmpty() const { return storage[0] == 0; }
-//	char *Pointer() { return storage; }
+	bool IsFull() const { return strlen() == Len; }
 	char& operator[](size_t index) { return storage[index]; }
 	char operator[](size_t index) const { return storage[index]; }
 	constexpr size_t Capacity() const { return Len; }
@@ -74,6 +74,7 @@ public:
 	bool ConstantTimeEquals(String<Len> other) const;
 
 	void Truncate(size_t len);
+	void Erase(size_t pos, size_t count = 1);
 
 private:
 	char storage[Len + 1];
@@ -133,6 +134,20 @@ template<size_t Len> void String<Len>::Truncate(size_t len)
 	}
 }
 
+template<size_t Len> void String<Len>::Erase(size_t pos, size_t count)
+{
+	const size_t len = strlen();
+	if (pos < len)
+	{
+		while (pos + count < len)
+		{
+			storage[pos] = storage[pos + count];
+			++pos;
+		}
+		storage[pos] = 0;
+	}
+}
+
 template<size_t Len> bool String<Len>::EndsWith(char c) const
 {
 	const size_t len = strlen();
diff --git a/src/Movement/DDA.cpp b/src/Movement/DDA.cpp
index a969c6dc..dfa7ae75 100644
--- a/src/Movement/DDA.cpp
+++ b/src/Movement/DDA.cpp
@@ -266,6 +266,7 @@ bool DDA::Init(GCodes::RawMove &nextMove, bool doMotorMapping)
 	}
 
 	xyMoving = false;
+	bool axesMoving = false;
 	bool extruding = false;												// we set this true if extrusion was commanded, even if it is too small to do
 	bool realMove = false;
 	float accelerations[DRIVES];
@@ -345,6 +346,10 @@ bool DDA::Init(GCodes::RawMove &nextMove, bool doMotorMapping)
 					}
 				}
 			}
+			else
+			{
+				axesMoving = true;
+			}
 		}
 	}
 
@@ -413,18 +418,25 @@ bool DDA::Init(GCodes::RawMove &nextMove, bool doMotorMapping)
 		// This means that the user gets the feed rate that he asked for. It also makes the delta calculations simpler.
 		// First do the bed tilt compensation for deltas.
 		directionVector[Z_AXIS] += (directionVector[X_AXIS] * k.GetTiltCorrection(X_AXIS)) + (directionVector[Y_AXIS] * k.GetTiltCorrection(Y_AXIS));
-
 		totalDistance = NormaliseXYZ();
 	}
+	else if (axesMoving)
+	{
+		// Some axes are moving, but not axes that X or Y are mapped to. Normalise the movement to the vector sum of the axes that are moving.
+		totalDistance = Normalise(directionVector, DRIVES, numAxes);
+	}
 	else
 	{
-		// Extruder-only movement, or movement of additional axes, or a combination.
-		// Currently we normalise vector sum of all drive movement to unit length.
-		// Alternatives would be:
-		// 1. Normalise the largest one to unit length. This means that when retracting multiple filaments, they all get the requested retract speed.
-		// 2. Normalise the sum to unit length. This means that when we use mixing, we get the requested extrusion rate at the nozzle.
-		// 3. Normalise the sum to the sum of the mixing coefficients (which we would have to include in the move details).
-		totalDistance = Normalise(directionVector, DRIVES, DRIVES);
+		// Extruder-only movement. Normalise so that the magnitude is the total absolute movement. This gives the correct feed rate for mixing extruders.
+		totalDistance = 0.0;
+		for (size_t d = 0; d < DRIVES; d++)
+		{
+			totalDistance += fabs(directionVector[d]);
+		}
+		if (totalDistance > 0.0)		// should always be true
+		{
+			Scale(directionVector, 1.0/totalDistance, DRIVES);
+		}
 	}
 
 	// 5. Compute the maximum acceleration available
diff --git a/src/Movement/Kinematics/Kinematics.cpp b/src/Movement/Kinematics/Kinematics.cpp
index 50c1409e..51c4d1fe 100644
--- a/src/Movement/Kinematics/Kinematics.cpp
+++ b/src/Movement/Kinematics/Kinematics.cpp
@@ -18,6 +18,7 @@
 #include "RepRap.h"
 #include "Platform.h"
 #include "GCodes/GCodeBuffer.h"
+#include "GCodes/GCodes.h"
 
 const char * const Kinematics::HomeAllFileName = "homeall.g";
 const char * const Kinematics::StandardHomingFileNames[] = AXES_("homex.g", "homey.g", "homez.g", "homeu.g", "homev.g", "homew.g", "homea.g", "homeb.g", "homec.g");
@@ -115,11 +116,20 @@ const char* Kinematics::GetHomingFileName(AxesBitmap toBeHomed, AxesBitmap alrea
 	const AxesBitmap homeFirst = AxesToHomeBeforeProbing();
 
 	// Return the homing file for the lowest axis that we have been asked to home
+	const char * const axisNames = reprap.GetGCodes().GetAxisLetters();
+	const char lettersToTry[] = "XYZUVWABC";
+	static_assert(ARRAY_SIZE(lettersToTry) >= MaxAxes, "lettersToTry too short");
 	for (size_t axis = 0; axis < numVisibleAxes; ++axis)
 	{
 		if (IsBitSet(toBeHomed, axis) && (axis != Z_AXIS || !homeZLast || (alreadyHomed & homeFirst) == homeFirst))
 		{
-			return StandardHomingFileNames[axis];
+            for (size_t actualAxis = 0; actualAxis < MaxAxes; actualAxis++)
+            {
+                if (axisNames[axis] == lettersToTry[actualAxis])
+                {
+                    return StandardHomingFileNames[actualAxis];
+                }
+            }
 		}
 	}
 
diff --git a/src/Movement/Kinematics/Kinematics.h b/src/Movement/Kinematics/Kinematics.h
index 5c386f68..531d0a45 100644
--- a/src/Movement/Kinematics/Kinematics.h
+++ b/src/Movement/Kinematics/Kinematics.h
@@ -17,7 +17,7 @@ inline floatc_t fcsquare(floatc_t a)
 }
 
 // Different types of kinematics we support. Each of these has a class to represent it.
-// These must have the same numeric assignments as the K parameter of the M669 command, as documented in ???
+// These must have the same numeric assignments as the K parameter of the M669 command, as documented in the GCodes wiki page
 enum class KinematicsType : uint8_t
 {
 	cartesian = 0,
@@ -29,6 +29,7 @@ enum class KinematicsType : uint8_t
 	hangprinter,
 	polar,
 	coreXYUV,
+//	linearDeltaPlusZ,	// reserved for @sga, see https://forum.duet3d.com/topic/5775/aditional-carterian-z-axis-on-delta-printer
 
 	unknown				// this one must be last!
 };
diff --git a/src/Networking/ESP8266WiFi/WiFiInterface.cpp b/src/Networking/ESP8266WiFi/WiFiInterface.cpp
index 2f4e8b18..394db873 100644
--- a/src/Networking/ESP8266WiFi/WiFiInterface.cpp
+++ b/src/Networking/ESP8266WiFi/WiFiInterface.cpp
@@ -158,6 +158,8 @@ WiFiInterface::WiFiInterface(Platform& p) : platform(p), uploader(nullptr), ftpD
 
 void WiFiInterface::Init()
 {
+	interfaceMutex.Create("WiFi");
+
 	// Make sure the ESP8266 is held in the reset state
 	ResetWiFi();
 	lastTickMillis = millis();
@@ -182,6 +184,8 @@ GCodeResult WiFiInterface::EnableProtocol(NetworkProtocol protocol, int port, in
 	else if (protocol < NumProtocols)
 	{
 		const Port portToUse = (port < 0) ? DefaultPortNumbers[protocol] : port;
+		MutexLocker lock(interfaceMutex);
+
 		if (portToUse != portNumbers[protocol] && state == NetworkState::active)
 		{
 			// We need to shut down and restart the protocol if it is active because the port number has changed
@@ -210,6 +214,8 @@ GCodeResult WiFiInterface::DisableProtocol(NetworkProtocol protocol, const Strin
 {
 	if (protocol < NumProtocols)
 	{
+		MutexLocker lock(interfaceMutex);
+
 		if (state == NetworkState::active)
 		{
 			ShutdownProtocol(protocol);
@@ -225,6 +231,8 @@ GCodeResult WiFiInterface::DisableProtocol(NetworkProtocol protocol, const Strin
 
 void WiFiInterface::StartProtocol(NetworkProtocol protocol)
 {
+	MutexLocker lock(interfaceMutex);
+
 	switch(protocol)
 	{
 	case HttpProtocol:
@@ -246,6 +254,8 @@ void WiFiInterface::StartProtocol(NetworkProtocol protocol)
 
 void WiFiInterface::ShutdownProtocol(NetworkProtocol protocol)
 {
+	MutexLocker lock(interfaceMutex);
+
 	switch(protocol)
 	{
 	case HttpProtocol:
@@ -432,6 +442,8 @@ void WiFiInterface::Stop()
 {
 	if (state != NetworkState::disabled)
 	{
+		MutexLocker lock(interfaceMutex);
+
 		digitalWrite(SamTfrReadyPin, LOW);			// tell the ESP we can't receive
 		digitalWrite(EspResetPin, LOW);				// put the ESP back into reset
 		DisableEspInterrupt();						// ignore IRQs from the transfer request pin
@@ -1535,6 +1547,8 @@ int32_t WiFiInterface::SendCommand(NetworkCommand cmd, SocketNumber socketNum, u
 		return ResponseNetworkDisabled;
 	}
 
+	MutexLocker lock(interfaceMutex);
+
 	if (transferPending)
 	{
 		if (reprap.Debug(moduleNetwork))
diff --git a/src/Networking/HttpResponder.cpp b/src/Networking/HttpResponder.cpp
index b96fcac2..edad5413 100644
--- a/src/Networking/HttpResponder.cpp
+++ b/src/Networking/HttpResponder.cpp
@@ -1296,7 +1296,7 @@ void HttpResponder::Diagnostics(MessageType mt) const
 
 /*static*/ void HttpResponder::InitStatic()
 {
-	gcodeReplyMutex.Create();
+	gcodeReplyMutex.Create("HttpGCodeReply");
 }
 
 // This is called from the GCodes task to store a response, which is picked up by the Network task
diff --git a/src/Networking/LwipEthernet/LwipEthernetInterface.cpp b/src/Networking/LwipEthernet/LwipEthernetInterface.cpp
index c203cf28..27e44fe7 100644
--- a/src/Networking/LwipEthernet/LwipEthernetInterface.cpp
+++ b/src/Networking/LwipEthernet/LwipEthernetInterface.cpp
@@ -140,6 +140,9 @@ LwipEthernetInterface::LwipEthernetInterface(Platform& p) : platform(p), closeDa
 
 void LwipEthernetInterface::Init()
 {
+	interfaceMutex.Create("Lwip");
+	//TODO we don't yet use this mutex anywhere!
+
 	// Clear the PCBs
 	for (size_t i = 0; i < NumTcpPorts; ++i)
 	{
diff --git a/src/Networking/Network.cpp b/src/Networking/Network.cpp
index ddfc9099..40a9d742 100644
--- a/src/Networking/Network.cpp
+++ b/src/Networking/Network.cpp
@@ -59,8 +59,8 @@ Network::Network(Platform& p) : platform(p), responders(nullptr), nextResponderT
 // Note that Platform::Init() must be called before this to that Platform::IsDuetWiFi() returns the correct value
 void Network::Init()
 {
-	httpMutex.Create();
-	telnetMutex.Create();
+	httpMutex.Create("HTTP");
+	telnetMutex.Create("Telnet");
 
 #if defined(DUET_NG)
 	interfaces[0] = (platform.IsDuetWiFi()) ? static_cast<NetworkInterface*>(new WiFiInterface(platform)) : static_cast<NetworkInterface*>(new W5500Interface(platform));
diff --git a/src/Networking/NetworkInterface.h b/src/Networking/NetworkInterface.h
index 6e10ea4f..4c807971 100644
--- a/src/Networking/NetworkInterface.h
+++ b/src/Networking/NetworkInterface.h
@@ -41,6 +41,8 @@ public:
 	virtual void OpenDataPort(Port port) = 0;
 	virtual void TerminateDataPort() = 0;
 
+	Mutex interfaceMutex;							// mutex to protect against multiple tasks using the same interface concurrently. Public so that sockets can lock it.
+
 protected:
 	Port portNumbers[NumProtocols];					// port number used for each protocol
 	bool protocolEnabled[NumProtocols];				// whether each protocol is enabled
diff --git a/src/Networking/TelnetResponder.cpp b/src/Networking/TelnetResponder.cpp
index 41cbe749..f2caf8a5 100644
--- a/src/Networking/TelnetResponder.cpp
+++ b/src/Networking/TelnetResponder.cpp
@@ -291,7 +291,7 @@ void TelnetResponder::ProcessLine()
 
 /*static*/ void TelnetResponder::InitStatic()
 {
-	gcodeReplyMutex.Create();
+	gcodeReplyMutex.Create("TelnetGCodeReply");
 }
 
 /*static*/ void TelnetResponder::HandleGCodeReply(const char *reply)
diff --git a/src/Networking/W5500Ethernet/W5500Interface.cpp b/src/Networking/W5500Ethernet/W5500Interface.cpp
index 60a254f0..8d5a885a 100644
--- a/src/Networking/W5500Ethernet/W5500Interface.cpp
+++ b/src/Networking/W5500Ethernet/W5500Interface.cpp
@@ -35,6 +35,8 @@ W5500Interface::W5500Interface(Platform& p)
 
 void W5500Interface::Init()
 {
+	interfaceMutex.Create("W5500");
+
 	// Ensure that the W5500 chip is in the reset state
 	pinMode(W5500ResetPin, OUTPUT_LOW);
 	lastTickMillis = millis();
@@ -53,6 +55,8 @@ GCodeResult W5500Interface::EnableProtocol(NetworkProtocol protocol, int port, i
 
 	if (protocol < NumProtocols)
 	{
+		MutexLocker lock(interfaceMutex);
+
 		const Port portToUse = (port < 0) ? DefaultPortNumbers[protocol] : port;
 		if (portToUse != portNumbers[protocol] && state == NetworkState::active)
 		{
@@ -87,6 +91,8 @@ GCodeResult W5500Interface::DisableProtocol(NetworkProtocol protocol, const Stri
 {
 	if (protocol < NumProtocols)
 	{
+		MutexLocker lock(interfaceMutex);
+
 		if (state == NetworkState::active)
 		{
 			ShutdownProtocol(protocol);
@@ -102,6 +108,8 @@ GCodeResult W5500Interface::DisableProtocol(NetworkProtocol protocol, const Stri
 
 void W5500Interface::StartProtocol(NetworkProtocol protocol)
 {
+	MutexLocker lock(interfaceMutex);
+
 	switch(protocol)
 	{
 	case HttpProtocol:
@@ -126,6 +134,8 @@ void W5500Interface::StartProtocol(NetworkProtocol protocol)
 
 void W5500Interface::ShutdownProtocol(NetworkProtocol protocol)
 {
+	MutexLocker lock(interfaceMutex);
+
 	switch(protocol)
 	{
 	case HttpProtocol:
@@ -222,6 +232,8 @@ void W5500Interface::SetMacAddress(const uint8_t mac[])
 // Start up the network
 void W5500Interface::Start()
 {
+	MutexLocker lock(interfaceMutex);
+
 	SetIPAddress(platform.GetIPAddress(), platform.NetMask(), platform.GateWay());
 	pinMode(W5500ResetPin, OUTPUT_LOW);
 	delayMicroseconds(550);						// W550 reset pulse must be at least 500us long
@@ -252,6 +264,8 @@ void W5500Interface::Stop()
 {
 	if (state != NetworkState::disabled)
 	{
+		MutexLocker lock(interfaceMutex);
+
 		if (usingDhcp)
 		{
 			DHCP_stop();
@@ -273,21 +287,25 @@ void W5500Interface::Spin(bool full)
 		break;
 
 	case NetworkState::establishingLink:
-		if (full && wizphy_getphylink() == PHY_LINK_ON)
 		{
-			usingDhcp = (ipAddress[0] == 0 && ipAddress[1] == 0 && ipAddress[2] == 0 && ipAddress[3] == 0);
-			if (usingDhcp)
-			{
-				// IP address is all zeros, so use DHCP
-//				debugPrintf("Link established, getting IP address\n");
-				DHCP_init(DhcpSocketNumber, platform.Random(), reprap.GetNetwork().GetHostname());
-				lastTickMillis = millis();
-				state = NetworkState::obtainingIP;
-			}
-			else
+			MutexLocker lock(interfaceMutex);
+
+			if (full && wizphy_getphylink() == PHY_LINK_ON)
 			{
-//				debugPrintf("Link established, network running\n");
-				state = NetworkState::connected;
+				usingDhcp = (ipAddress[0] == 0 && ipAddress[1] == 0 && ipAddress[2] == 0 && ipAddress[3] == 0);
+				if (usingDhcp)
+				{
+					// IP address is all zeros, so use DHCP
+//					debugPrintf("Link established, getting IP address\n");
+					DHCP_init(DhcpSocketNumber, platform.Random(), reprap.GetNetwork().GetHostname());
+					lastTickMillis = millis();
+					state = NetworkState::obtainingIP;
+				}
+				else
+				{
+//					debugPrintf("Link established, network running\n");
+					state = NetworkState::connected;
+				}
 			}
 		}
 		break;
@@ -295,6 +313,8 @@ void W5500Interface::Spin(bool full)
 	case NetworkState::obtainingIP:
 		if (full)
 		{
+			MutexLocker lock(interfaceMutex);
+
 			if (wizphy_getphylink() == PHY_LINK_ON)
 			{
 				const uint32_t now = millis();
@@ -334,45 +354,49 @@ void W5500Interface::Spin(bool full)
 		break;
 
 	case NetworkState::active:
-		// Check that the link is still up
-		if (wizphy_getphylink() == PHY_LINK_ON)
 		{
-			// Maintain DHCP
-			if (full && usingDhcp)
+			MutexLocker lock(interfaceMutex);
+
+			// Check that the link is still up
+			if (wizphy_getphylink() == PHY_LINK_ON)
 			{
-				const uint32_t now = millis();
-				if (now - lastTickMillis >= 1000)
-				{
-					lastTickMillis += 1000;
-					DHCP_time_handler();
-				}
-				const DhcpRunResult ret = DHCP_run();
-				if (ret == DhcpRunResult::DHCP_IP_CHANGED || ret == DhcpRunResult::DHCP_IP_ASSIGN)
+				// Maintain DHCP
+				if (full && usingDhcp)
 				{
-//					debugPrintf("IP address changed\n");
-					getSIPR(ipAddress);
+					const uint32_t now = millis();
+					if (now - lastTickMillis >= 1000)
+					{
+						lastTickMillis += 1000;
+						DHCP_time_handler();
+					}
+					const DhcpRunResult ret = DHCP_run();
+					if (ret == DhcpRunResult::DHCP_IP_CHANGED || ret == DhcpRunResult::DHCP_IP_ASSIGN)
+					{
+//						debugPrintf("IP address changed\n");
+						getSIPR(ipAddress);
+					}
 				}
-			}
 
-			// Poll the next TCP socket
-			sockets[nextSocketToPoll]->Poll(full);
+				// Poll the next TCP socket
+				sockets[nextSocketToPoll]->Poll(full);
 
-			// Move on to the next TCP socket for next time
-			++nextSocketToPoll;
-			if (nextSocketToPoll == NumW5500TcpSockets)
-			{
-				nextSocketToPoll = 0;
+				// Move on to the next TCP socket for next time
+				++nextSocketToPoll;
+				if (nextSocketToPoll == NumW5500TcpSockets)
+				{
+					nextSocketToPoll = 0;
+				}
 			}
-		}
-		else if (full)
-		{
-//			debugPrintf("Lost phy link\n");
-			if (usingDhcp)
+			else if (full)
 			{
-				DHCP_stop();
+//				debugPrintf("Lost phy link\n");
+				if (usingDhcp)
+				{
+					DHCP_stop();
+				}
+				TerminateSockets();
+				state = NetworkState::establishingLink;
 			}
-			TerminateSockets();
-			state = NetworkState::establishingLink;
 		}
 		break;
 	}
diff --git a/src/Networking/W5500Ethernet/W5500Socket.cpp b/src/Networking/W5500Ethernet/W5500Socket.cpp
index 8e200352..f6bacc2b 100644
--- a/src/Networking/W5500Ethernet/W5500Socket.cpp
+++ b/src/Networking/W5500Ethernet/W5500Socket.cpp
@@ -7,6 +7,7 @@
 
 #include "W5500Socket.h"
 #include "Network.h"
+#include "NetworkInterface.h"
 #include "Wiznet/Ethernet/socketlib.h"
 #include "NetworkBuffer.h"
 #include "RepRap.h"
@@ -32,12 +33,16 @@ void W5500Socket::Init(SocketNumber skt, Port serverPort, NetworkProtocol p)
 
 void W5500Socket::TerminateAndDisable()
 {
+	MutexLocker lock(interface->interfaceMutex);
+
 	Terminate();
 	state = SocketState::disabled;
 }
 
 void W5500Socket::ReInit()
 {
+	MutexLocker lock(interface->interfaceMutex);
+
 	// Discard any received data
 	while (receivedData != nullptr)
 	{
@@ -56,6 +61,8 @@ void W5500Socket::ReInit()
 // Close a connection when the last packet has been sent
 void W5500Socket::Close()
 {
+	MutexLocker lock(interface->interfaceMutex);
+
 	if (state != SocketState::disabled && state != SocketState::inactive)
 	{
 		ExecCommand(socketNum, Sn_CR_DISCON);
@@ -71,6 +78,8 @@ void W5500Socket::Close()
 // Terminate a connection immediately
 void W5500Socket::Terminate()
 {
+	MutexLocker lock(interface->interfaceMutex);
+
 	if (state != SocketState::disabled)
 	{
 		disconnectNoWait(socketNum);
@@ -97,6 +106,8 @@ bool W5500Socket::ReadChar(char& c)
 {
 	if (receivedData != nullptr)
 	{
+		MutexLocker lock(interface->interfaceMutex);
+
 		const bool ret = receivedData->ReadChar(c);
 		if (receivedData->IsEmpty())
 		{
@@ -140,6 +151,8 @@ void W5500Socket::Poll(bool full)
 {
 	if (state != SocketState::disabled)
 	{
+		MutexLocker lock(interface->interfaceMutex);
+
 		switch(getSn_SR(socketNum))
 		{
 		case SOCK_INIT:
@@ -206,7 +219,7 @@ void W5500Socket::Poll(bool full)
 	}
 }
 
-// Try to receive more incoming data from the socket
+// Try to receive more incoming data from the socket. The mutex is alrady owned.
 void W5500Socket::ReceiveData()
 {
 	const uint16_t len = getSn_RX_RSR(socketNum);
@@ -245,7 +258,7 @@ void W5500Socket::ReceiveData()
 	}
 }
 
-// Discard any received data for this transaction
+// Discard any received data for this transaction. The mutex is already owned.
 void W5500Socket::DiscardReceivedData()
 {
 	while (receivedData != nullptr)
@@ -257,6 +270,8 @@ void W5500Socket::DiscardReceivedData()
 // Send the data, returning the length buffered
 size_t W5500Socket::Send(const uint8_t *data, size_t length)
 {
+	MutexLocker lock(interface->interfaceMutex);
+
 	if (CanSend() && length != 0 && getSn_SR(socketNum) == SOCK_ESTABLISHED)
 	{
 		// Check for previous send complete
@@ -311,6 +326,8 @@ size_t W5500Socket::Send(const uint8_t *data, size_t length)
 // Tell the interface to send the outstanding data
 void W5500Socket::Send()
 {
+	MutexLocker lock(interface->interfaceMutex);
+
 	if (CanSend() && sendOutstanding)
 	{
 		setSn_TX_WR(socketNum, wizTxBufferPtr);
diff --git a/src/Platform.cpp b/src/Platform.cpp
index 64000fe1..2e74416e 100644
--- a/src/Platform.cpp
+++ b/src/Platform.cpp
@@ -57,6 +57,8 @@
 
 #include <climits>
 
+extern uint32_t _estack;			// defined in the linker script
+
 #if !defined(HAS_LWIP_NETWORKING) || !defined(HAS_WIFI_NETWORKING) || !defined(HAS_CPU_TEMP_SENSOR) || !defined(HAS_HIGH_SPEED_SD) \
  || !defined(HAS_SMART_DRIVERS) || !defined(HAS_STALL_DETECT) || !defined(HAS_VOLTAGE_MONITOR) || !defined(HAS_VREF_MONITOR) || !defined(ACTIVE_LOW_HEAT_ON) \
  || !defined(SUPPORT_NONLINEAR_EXTRUSION)
@@ -215,8 +217,8 @@ void Platform::Init()
 	commsParams[2] = 0;
 #endif
 
-	usbMutex.Create();
-	auxMutex.Create();
+	usbMutex.Create("USB");
+	auxMutex.Create("Aux");
 	auxDetected = false;
 	auxSeq = 0;
 
@@ -224,7 +226,7 @@ void Platform::Init()
 	SERIAL_AUX_DEVICE.begin(baudRates[1]);		// this can't be done in the constructor because the Arduino port initialisation isn't complete at that point
 #ifdef SERIAL_AUX2_DEVICE
 	SERIAL_AUX2_DEVICE.begin(baudRates[2]);
-	aux2Mutex.Create();
+	aux2Mutex.Create("Aux2");
 #endif
 
 	compatibility = Compatibility::marlin;		// default to Marlin because the common host programs expect the "OK" response to commands
@@ -1074,7 +1076,7 @@ void Platform::UpdateFirmware()
 	}
 
 #if defined(DUET_NG) || defined(DUET_M)
-	IoPort::WriteDigital(Z_PROBE_MOD_PIN, false);	// turn the DIAG LED off
+	IoPort::WriteDigital(DiagPin, false);			// turn the DIAG LED off
 #endif
 
 	wdt_restart(WDT);								// kick the watchdog one last time
@@ -1381,7 +1383,7 @@ void Platform::Spin()
 				{
 					if ((stalledDrivers & mask) == 0)
 					{
-						// This stall is new and we are printing, so check whether we need to perform some action in response to the stall
+						// This stall is new so check whether we need to perform some action in response to the stall
 						if ((rehomeOnStallDrivers & mask) != 0)
 						{
 							stalledDriversToRehome |= mask;
@@ -1551,7 +1553,8 @@ void Platform::Spin()
 		switch (autoSaveState)
 		{
 		case AutoSaveState::starting:
-			if (currentVin >= autoResumeReading)
+			// Some users set the auto resume threshold high to disable auto resume, so prime auto save at the auto save threshold plus half a volt
+			if (currentVin >= autoResumeReading || currentVin > autoPauseReading + PowerVoltageToAdcReading(0.5))
 			{
 				autoSaveState = AutoSaveState::normal;
 			}
@@ -1794,7 +1797,8 @@ void Platform::SoftwareReset(uint16_t reason, const uint32_t *stk)
 			srdBuf[slot].sp = reinterpret_cast<uint32_t>(stk);
 			for (size_t i = 0; i < ARRAY_SIZE(srdBuf[slot].stack); ++i)
 			{
-				srdBuf[slot].stack[i] = stk[i];
+				srdBuf[slot].stack[i] = (stk < &_estack) ? *stk : 0xFFFFFFFF;
+				++stk;
 			}
 		}
 
diff --git a/src/RTOSIface.cpp b/src/RTOSIface.cpp
index ee9650bc..c185a454 100644
--- a/src/RTOSIface.cpp
+++ b/src/RTOSIface.cpp
@@ -15,11 +15,14 @@
 
 static_assert(Mutex::TimeoutUnlimited == portMAX_DELAY, "Bad value for TimeoutUnlimited");
 
-void Mutex::Create()
+void Mutex::Create(const char *pName)
 {
 	if (handle == nullptr)
 	{
 		handle = xSemaphoreCreateRecursiveMutexStatic(&storage);
+		name = pName;
+		next = mutexList;
+		mutexList = this;
 	}
 }
 
@@ -39,10 +42,11 @@ TaskHandle Mutex::GetHolder() const
 }
 
 TaskBase *TaskBase::taskList = nullptr;
+Mutex *Mutex::mutexList = nullptr;
 
 #else
 
-void Mutex::Create()
+void Mutex::Create(const char *pName)
 {
 }
 
diff --git a/src/RTOSIface.h b/src/RTOSIface.h
index a1964b66..151f3204 100644
--- a/src/RTOSIface.h
+++ b/src/RTOSIface.h
@@ -28,21 +28,34 @@ class Mutex
 public:
 	Mutex() { handle = nullptr; }
 
-	void Create();
+	void Create(const char *pName);
 	bool Take(uint32_t timeout = TimeoutUnlimited) const;
 	bool Release() const;
 	TaskHandle GetHolder() const;
 
-	static constexpr uint32_t TimeoutUnlimited = 0xFFFFFFFF;
+#ifdef RTOS
+	const Mutex *GetNext() const { return next; }
+	const char *GetName() const { return name; }
+#endif
 
 	Mutex(const Mutex&) = delete;
 	Mutex& operator=(const Mutex&) = delete;
 
+	static constexpr uint32_t TimeoutUnlimited = 0xFFFFFFFF;
+
+#ifdef RTOS
+	static const Mutex *GetMutexList() { return mutexList; }
+#endif
+
 private:
 
 #ifdef RTOS
 	SemaphoreHandle_t handle;
+	Mutex *next;
+	const char *name;
 	StaticSemaphore_t storage;
+
+	static Mutex *mutexList;
 #else
 	void *handle;
 #endif
@@ -60,7 +73,7 @@ public:
 	void Suspend() const { vTaskSuspend(handle); }
 	const TaskBase *GetNext() const { return next; }
 
-	TaskBase(const TaskBase&) = delete;				// it's not save to copy these
+	TaskBase(const TaskBase&) = delete;				// it's not safe to copy these
 	TaskBase& operator=(const TaskBase&) = delete;	// it's not safe to assign these
 	// Ideally we would declare the destructor as deleted too, because it's unsafe to delete these because they are linked together via the 'next' field.
 	// But that prevents us from declaring static instances of tasks.
diff --git a/src/RepRap.cpp b/src/RepRap.cpp
index 914b860a..e83bd6e7 100644
--- a/src/RepRap.cpp
+++ b/src/RepRap.cpp
@@ -154,8 +154,8 @@ RepRap::RepRap() : toolList(nullptr), currentTool(nullptr), lastWarningMillis(0)
 
 void RepRap::Init()
 {
-	toolListMutex.Create();
-	messageBoxMutex.Create();
+	toolListMutex.Create("ToolList");
+	messageBoxMutex.Create("MessageBox");
 
 	platform->Init();
 	network->Init();
@@ -687,7 +687,14 @@ void RepRap::Tick()
 
 			// We now save the stack when we get stuck in a spin loop
 			register const uint32_t * stackPtr asm ("sp");
-			platform->SoftwareReset((uint16_t)SoftwareResetReason::stuckInSpin, stackPtr + 5);
+
+			platform->SoftwareReset((uint16_t)SoftwareResetReason::stuckInSpin,
+#ifdef RTOS
+				stackPtr + 5 + 15			// discard the stack used by the FreeRTOS stack handler and our tick handler
+#else
+				stackPtr + 5				// discard the stack used by our tick handler
+#endif
+				);
 		}
 	}
 }
@@ -1320,6 +1327,9 @@ OutputBuffer *RepRap::GetStatusResponse(uint8_t type, ResponseSource source)
 		// Fraction of file printed
 		response->catf("],\"fractionPrinted\":%.1f", (double)((printMonitor->IsPrinting()) ? (gCodes->FractionOfFilePrinted() * 100.0) : 0.0));
 
+		// Byte position of the file being printed
+		response->catf(",\"filePosition\":%lu", gCodes->GetFilePosition());
+
 		// First Layer Duration
 		response->catf(",\"firstLayerDuration\":%.1f", (double)(printMonitor->GetFirstLayerDuration()));
 
diff --git a/src/Scanner.cpp b/src/Scanner.cpp
index 64ab3a62..6e762bd7 100644
--- a/src/Scanner.cpp
+++ b/src/Scanner.cpp
@@ -13,6 +13,8 @@
 #include "Platform.h"
 
 
+const char* const SCANNER_ON_G = "scanner_on.g";
+const char* const SCANNER_OFF_G = "scanner_off.g";
 const char* const ALIGN_ON_G = "align_on.g";
 const char* const ALIGN_OFF_G = "align_off.g";
 const char* const SCAN_PRE_G = "scan_pre.g";
@@ -104,7 +106,8 @@ void Scanner::Spin()
 		}
 		SetState(ScannerState::Disconnected);
 
-		// Cannot do anything else...
+		// Run a macro to perform custom actions when the scanner is removed
+		DoFileMacro(SCANNER_OFF_G);
 		return;
 	}
 
@@ -389,18 +392,15 @@ bool Scanner::Enable()
 }
 
 // Register a scanner device
-bool Scanner::Register()
+void Scanner::Register()
 {
-	if (IsRegistered())
+	if (!IsRegistered())
 	{
-		// Don't do anything if a device is already registered
-		return true;
-	}
-
-	platform.Message(MessageType::BlockingUsbMessage, "OK\n");
-	SetState(ScannerState::Idle);
+		platform.Message(MessageType::BlockingUsbMessage, "OK\n");
+		SetState(ScannerState::Idle);
 
-	return true;
+		DoFileMacro(SCANNER_ON_G);
+	}
 }
 
 // Initiate a new scan
diff --git a/src/Scanner.h b/src/Scanner.h
index db50c5d1..0c5c279d 100644
--- a/src/Scanner.h
+++ b/src/Scanner.h
@@ -53,7 +53,7 @@ public:
 	bool Enable();										// Enable 3D scanner extension. Returns true when done
 
 	bool IsRegistered() const;							// Is the 3D scanner registered and ready to use?
-	bool Register();									// Register a 3D scanner. Returns true when done
+	void Register();									// Register a 3D scanner instance
 	// External scanners are automatically unregistered when the main port (USB) is closed
 
 	// Start a new 3D scan. Returns true when the scan has been initiated
diff --git a/src/Storage/FileInfoParser.cpp b/src/Storage/FileInfoParser.cpp
index 4dfc90cf..0e2d4173 100644
--- a/src/Storage/FileInfoParser.cpp
+++ b/src/Storage/FileInfoParser.cpp
@@ -32,7 +32,7 @@ FileInfoParser::FileInfoParser()
 	: parseState(notParsing), fileBeingParsed(nullptr), accumulatedParseTime(0), accumulatedReadTime(0), accumulatedSeekTime(0), fileOverlapLength(0)
 {
 	parsedFileInfo.Init();
-	parserMutex.Create();
+	parserMutex.Create("FileInfoParser");
 }
 
 bool FileInfoParser::GetFileInfo(const char *directory, const char *fileName, GCodeFileInfo& info, bool quitEarly)
diff --git a/src/Storage/MassStorage.cpp b/src/Storage/MassStorage.cpp
index e06946a1..c13bb8ef 100644
--- a/src/Storage/MassStorage.cpp
+++ b/src/Storage/MassStorage.cpp
@@ -63,9 +63,12 @@ MassStorage::MassStorage(Platform* p) : freeWriteBuffers(nullptr)
 
 void MassStorage::Init()
 {
+	static const char * const VolMutexNames[] = { "SD0", "SD1" };
+	static_assert(ARRAY_SIZE(VolMutexNames) >= NumSdCards, "Incorrect VolMutexNames array");
+
 	// Create the mutexes
-	fsMutex.Create();
-	dirMutex.Create();
+	fsMutex.Create("FileSystem");
+	dirMutex.Create("DirSearch");
 
 	for (size_t i = 0; i < NumFileWriteBuffers; ++i)
 	{
@@ -79,7 +82,7 @@ void MassStorage::Init()
 		inf.mounting = inf.isMounted = false;
 		inf.cdPin = SdCardDetectPins[card];
 		inf.cardState = (inf.cdPin == NoPin) ? CardDetectState::present : CardDetectState::notPresent;
-		inf.volMutex.Create();
+		inf.volMutex.Create(VolMutexNames[card]);
 	}
 
 	sd_mmc_init(SdWriteProtectPins, SdSpiCSPins);		// initialize SD MMC stack
diff --git a/src/Tasks.cpp b/src/Tasks.cpp
index dc9169d6..a3a4c782 100644
--- a/src/Tasks.cpp
+++ b/src/Tasks.cpp
@@ -91,8 +91,8 @@ extern "C" void AppMain()
 
 extern "C" void MainTask(void *pvParameters)
 {
-	mallocMutex.Create();
-	spiMutex.Create();
+	mallocMutex.Create("Malloc");
+	spiMutex.Create("SPI");
 #endif
 	reprap.Init();
 	for (;;)
@@ -188,6 +188,7 @@ namespace Tasks
 		}
 
 #ifdef RTOS
+		p.Message(mtype, "Tasks:");
 		for (const TaskBase *t = TaskBase::GetTaskList(); t != nullptr; t = t->GetNext())
 		{
 			TaskStatus_t taskDetails;
@@ -197,9 +198,28 @@ namespace Tasks
 												: (taskDetails.eCurrentState == eBlocked) ? "blocked"
 													: (taskDetails.eCurrentState == eSuspended) ? "suspended"
 														: "invalid";
-			p.MessageF(mtype, "Task %s %s, free stack %u\n",
+			p.MessageF(mtype, " %s(%s,%u)",
 				taskDetails.pcTaskName, stateText, (unsigned int)(taskDetails.usStackHighWaterMark * sizeof(StackType_t)));
 		}
+		p.Message(mtype, "\nMutexes:");
+
+		for (const Mutex *m = Mutex::GetMutexList(); m != nullptr; m = m->GetNext())
+		{
+			const TaskHandle holder = m->GetHolder();
+			TaskStatus_t taskDetails;
+			const char *holderText;
+			if (holder == nullptr)
+			{
+				holderText = "null";
+			}
+			else
+			{
+				vTaskGetInfo(holder, &taskDetails, pdTRUE, eInvalid);
+				holderText = taskDetails.pcTaskName;
+			}
+			p.MessageF(mtype, " %s(%s)", m->GetName(), holderText);
+		}
+		p.MessageF(mtype, "\n");
 #endif
 	}
 
@@ -216,7 +236,7 @@ namespace Tasks
 #ifdef RTOS
 
 static StaticTask_t xIdleTaskTCB;
-static StackType_t uxIdleTaskStack[ configMINIMAL_STACK_SIZE ];
+static StackType_t uxIdleTaskStack[configMINIMAL_STACK_SIZE];
 
 extern "C" void vApplicationGetIdleTaskMemory( StaticTask_t **ppxIdleTaskTCBBuffer,
                                     StackType_t **ppxIdleTaskStackBuffer,
@@ -233,7 +253,7 @@ extern "C" void vApplicationGetIdleTaskMemory( StaticTask_t **ppxIdleTaskTCBBuff
 }
 
 static StaticTask_t xTimerTaskTCB;
-static StackType_t uxTimerTaskStack[ configTIMER_TASK_STACK_DEPTH ];
+static StackType_t uxTimerTaskStack[configTIMER_TASK_STACK_DEPTH];
 
 extern "C" void vApplicationGetTimerTaskMemory( StaticTask_t **ppxTimerTaskTCBBuffer,
                                      StackType_t **ppxTimerTaskStackBuffer,
diff --git a/src/Version.h b/src/Version.h
index 6c5ebe24..b2e0b33c 100644
--- a/src/Version.h
+++ b/src/Version.h
@@ -12,9 +12,9 @@
 #ifndef VERSION
 #ifdef RTOS
 # define RTOSVER		"(RTOS)"
-# define MAIN_VERSION	"2.0"
+# define MAIN_VERSION	"2.01beta1"
 #else
-# define MAIN_VERSION	"1.21.1"
+# define MAIN_VERSION	"1.21.2beta1"
 # define RTOSVER
 #endif
 
@@ -22,7 +22,7 @@
 #endif
 
 #ifndef DATE
-# define DATE "2018-06-05b3"
+# define DATE "2018-06-23b1"
 #endif
 
 #define AUTHORS "reprappro, dc42, chrishamm, t3p3, dnewman"