Fixed issue with small extruder moves and filament monitors

3 files changed, 33 insertions, 24 deletions

diff --git a/src/Movement/DDA.cpp b/src/Movement/DDA.cpp
index 6c08ce0f..315a3eec 100644
--- a/src/Movement/DDA.cpp
+++ b/src/Movement/DDA.cpp
@@ -2336,28 +2336,32 @@ void DDA::UpdateMovementAccumulators(volatile int32_t *accumulators) const noexc
 #if 1
 	// Loop through DMs, checking whether each associated drive is an extruder and updating the movement accumulator if so.
 	// We could omit the check that the drive is an accumulator so that we update all accumulators, but we would still need to check for leadscrew adjustment moves.
-	const unsigned int firstExtruderDrive = ExtruderToLogicalDrive(reprap.GetGCodes().GetNumExtruders() - 1);
-	for (const DriveMovement* dm = activeDMs; dm != nullptr; )
+	const size_t numExtruders = reprap.GetGCodes().GetNumExtruders();
+	if (numExtruders != 0)
 	{
-		const uint8_t drv = dm->drive;
-		if (   drv >= firstExtruderDrive						// check that it's an extruder (to save the call to GetStepsTaken)
-			&& drv < MaxAxesPlusExtruders						// check that it's not a direct leadscrew move
-		   )
+		const unsigned int firstExtruderDrive = ExtruderToLogicalDrive(numExtruders - 1);
+		for (const DriveMovement* dm = activeDMs; dm != nullptr; )
 		{
-			accumulators[drv] += dm->GetNetStepsTaken();
+			const uint8_t drv = dm->drive;
+			if (   drv >= firstExtruderDrive						// check that it's an extruder (to save the call to GetStepsTaken)
+				&& drv < MaxAxesPlusExtruders						// check that it's not a direct leadscrew move
+			   )
+			{
+				accumulators[drv] += dm->GetNetStepsTaken();
+			}
+			dm = dm->nextDM;
 		}
-		dm = dm->nextDM;
-	}
-	for (const DriveMovement* dm = completedDMs; dm != nullptr; )
-	{
-		const uint8_t drv = dm->drive;
-		if (   drv >= firstExtruderDrive						// check that it's an extruder (to save the call to GetStepsTaken)
-			&& drv < MaxAxesPlusExtruders						// check that it's not a direct leadscrew move
-		   )
+		for (const DriveMovement* dm = completedDMs; dm != nullptr; )
 		{
-			accumulators[drv] += dm->GetNetStepsTaken();
+			const uint8_t drv = dm->drive;
+			if (   drv >= firstExtruderDrive						// check that it's an extruder (to save the call to GetStepsTaken)
+				&& drv < MaxAxesPlusExtruders						// check that it's not a direct leadscrew move
+			   )
+			{
+				accumulators[drv] += dm->GetNetStepsTaken();
+			}
+			dm = dm->nextDM;
 		}
-		dm = dm->nextDM;
 	}
 #else
 	// Loop through extruders
diff --git a/src/Movement/DDARing.cpp b/src/Movement/DDARing.cpp
index 4aeb39a7..27cd1aa7 100644
--- a/src/Movement/DDARing.cpp
+++ b/src/Movement/DDARing.cpp
@@ -171,7 +171,7 @@ GCodeResult DDARing::ConfigureMovementQueue(GCodeBuffer& gb, const StringRef& re
 void DDARing::RecycleDDAs() noexcept
 {
 	// Recycle the DDAs for completed moves, checking for DDA errors to print if Move debug is enabled
-	while (checkPointer->GetState() == DDA::completed)
+	while (checkPointer->GetState() == DDA::completed && checkPointer != currentDda)	// we haven't finished with a completed DDA until it is no longer the current DDA!
 	{
 		// Check for step errors and record/print them if we have any, before we lose the DMs
 		if (checkPointer->HasStepError())
@@ -576,11 +576,11 @@ void DDARing::CurrentMoveCompleted() noexcept
 	{
 		AtomicCriticalSectionLocker lock;
 		cdda->UpdateMovementAccumulators(movementAccumulators);
-		currentDda = nullptr;
-	}
-	if (cdda->IsCheckingEndstops())
-	{
-		Move::WakeMoveTaskFromISR();				// wake the Move task if we were checking endstops
+		if (cdda->IsCheckingEndstops())
+		{
+			Move::WakeMoveTaskFromISR();			// wake the Move task if we were checking endstops
+		}
+		currentDda = nullptr;						// once we have done this, the DDA can be recycled by the Move task
 	}
 
 	getPointer = getPointer->GetNext();
@@ -599,6 +599,7 @@ bool DDARing::SetWaitingToEmpty() noexcept
 	return ret;
 }
 
+// Get the number of steps taken by an extruder drive since the last time we called this function for that drive
 int32_t DDARing::GetAccumulatedMovement(size_t drive, bool& isPrinting) noexcept
 {
 	AtomicCriticalSectionLocker lock;
diff --git a/src/Movement/DriveMovement.cpp b/src/Movement/DriveMovement.cpp
index 3ae424b2..e110adb1 100644
--- a/src/Movement/DriveMovement.cpp
+++ b/src/Movement/DriveMovement.cpp
@@ -611,6 +611,7 @@ bool DriveMovement::PrepareDeltaAxis(const DDA& dda, const PrepParams& params) n
 }
 
 // Prepare this DM for an extruder move, returning true if there are steps to do
+// If there are no steps to do, set nextStep = 0 so that DDARing::CurrentMoveCompleted doesn't add any steps to the movement accumulator
 // We have already generated the extruder segments and we know that there are some
 bool DriveMovement::PrepareExtruder(const DDA& dda, const PrepParams& params) noexcept
 {
@@ -802,6 +803,8 @@ bool DriveMovement::PrepareExtruder(const DDA& dda, const PrepParams& params) no
 		if (netSteps == 0 && iFwdSteps == 0)
 		{
 			// No movement at all
+			nextStep = totalSteps = 0;
+			reverseStartStep = 1;
 			shaper.SetExtrusionPending(netDistance * dda.directionVector[drive]);
 			return false;
 		}
@@ -837,7 +840,8 @@ bool DriveMovement::PrepareExtruder(const DDA& dda, const PrepParams& params) no
 		else
 		{
 			// No steps at all, or negative forward steps which I think should be impossible unless the steps/mm is changed
-			totalSteps = 0;
+			nextStep = totalSteps = 0;
+			reverseStartStep = 1;
 			shaper.SetExtrusionPending(forwardDistance * dda.directionVector[drive]);
 			return false;
 		}