Fixed issue with extruder stopping after a tiny move

Also refactored nonlinear extrusion coce to make it more efficient

4 files changed, 32 insertions, 35 deletions

diff --git a/src/GCodes/GCodes2.cpp b/src/GCodes/GCodes2.cpp
index 4755bc61..a04a106b 100644
--- a/src/GCodes/GCodes2.cpp
+++ b/src/GCodes/GCodes2.cpp
@@ -3729,8 +3729,8 @@ bool GCodes::HandleMcode(GCodeBuffer& gb, const StringRef& reply) THROWS(GCodeEx
 					}
 					else
 					{
-						platform.GetExtrusionCoefficients(extruder, a, b, limit);
-						reply.printf("Drive %u nonlinear extrusion coefficients: A=%.3f, B=%.4f, limit=%.2f", extruder, (double)a, (double)b, (double)limit);
+						const NonlinearExtrusion& nl = platform.GetExtrusionCoefficients(extruder);
+						reply.printf("Drive %u nonlinear extrusion coefficients: A=%.3f, B=%.4f, limit=%.2f", extruder, (double)nl.A, (double)nl.B, (double)nl.limit);
 					}
 				}
 				break;
diff --git a/src/Movement/DDA.cpp b/src/Movement/DDA.cpp
index 7958a71b..26358f6d 100644
--- a/src/Movement/DDA.cpp
+++ b/src/Movement/DDA.cpp
@@ -1527,17 +1527,15 @@ void DDA::Prepare(SimulationMode simMode) noexcept
 					platform.EnableDrivers(drive, false);
 					const size_t extruder = LogicalDriveToExtruder(drive);
 #if SUPPORT_NONLINEAR_EXTRUSION
-					// Add the nonlinear extrusion correction to totalExtrusion
-					if (flags.isPrintingMove)
+					// Add the nonlinear extrusion correction to totalExtrusion.
+					// If we are given a stupidly short move to execute then clocksNeeded can be zero, which leads to NaNs in this code; so we need to guard against that.
+					if (flags.isPrintingMove && clocksNeeded != 0)
 					{
-						float a, b, limit;
-						if (platform.GetExtrusionCoefficients(extruder, a, b, limit))
-						{
-							float& dv = directionVector[drive];
-							const float averageExtrusionSpeed = (totalDistance * dv)/clocksNeeded;
-							const float factor = 1.0 + min<float>((averageExtrusionSpeed * a) + (averageExtrusionSpeed * averageExtrusionSpeed * b), limit);
-							dv *= factor;
-						}
+						const NonlinearExtrusion& nl = platform.GetExtrusionCoefficients(extruder);
+						float& dv = directionVector[drive];
+						const float averageExtrusionSpeed = (totalDistance * dv)/clocksNeeded;
+						const float factor = 1.0 + min<float>((averageExtrusionSpeed * nl.A) + (averageExtrusionSpeed * averageExtrusionSpeed * nl.B), nl.limit);
+						dv *= factor;
 					}
 #endif
 
diff --git a/src/Platform/Platform.cpp b/src/Platform/Platform.cpp
index 259eae32..8aafab9a 100644
--- a/src/Platform/Platform.cpp
+++ b/src/Platform/Platform.cpp
@@ -313,9 +313,9 @@ constexpr ObjectModelTableEntry Platform::objectModelTable[] =
 	{ "stepsPerMm",			OBJECT_MODEL_FUNC(self->driveStepsPerUnit[ExtruderToLogicalDrive(context.GetLastIndex())], 2),											ObjectModelEntryFlags::none },
 
 	// 5. move.extruders[].nonlinear members
-	{ "a",					OBJECT_MODEL_FUNC(self->nonlinearExtrusionA[context.GetLastIndex()], 3),									ObjectModelEntryFlags::none },
-	{ "b",					OBJECT_MODEL_FUNC(self->nonlinearExtrusionB[context.GetLastIndex()], 3),									ObjectModelEntryFlags::none },
-	{ "upperLimit",			OBJECT_MODEL_FUNC(self->nonlinearExtrusionLimit[context.GetLastIndex()], 2),								ObjectModelEntryFlags::none },
+	{ "a",					OBJECT_MODEL_FUNC(self->nonlinearExtrusion[context.GetLastIndex()].A, 3),									ObjectModelEntryFlags::none },
+	{ "b",					OBJECT_MODEL_FUNC(self->nonlinearExtrusion[context.GetLastIndex()].B, 3),									ObjectModelEntryFlags::none },
+	{ "upperLimit",			OBJECT_MODEL_FUNC(self->nonlinearExtrusion[context.GetLastIndex()].limit, 2),								ObjectModelEntryFlags::none },
 
 #if HAS_12V_MONITOR
 	// 6. v12 members
@@ -694,8 +694,8 @@ void Platform::Init() noexcept
 		extruderDrivers[extr].SetLocal(extr + MinAxes);			// set up default extruder drive mapping
 		driveDriverBits[ExtruderToLogicalDrive(extr)] = StepPins::CalcDriverBitmap(extr + MinAxes);
 #if SUPPORT_NONLINEAR_EXTRUSION
-		nonlinearExtrusionA[extr] = nonlinearExtrusionB[extr] = 0.0;
-		nonlinearExtrusionLimit[extr] = DefaultNonlinearExtrusionLimit;
+		nonlinearExtrusion[extr].A = nonlinearExtrusion[extr].B = 0.0;
+		nonlinearExtrusion[extr].limit = DefaultNonlinearExtrusionLimit;
 #endif
 	}
 
@@ -3709,25 +3709,13 @@ void Platform::AtxPowerOff() noexcept
 
 #if SUPPORT_NONLINEAR_EXTRUSION
 
-bool Platform::GetExtrusionCoefficients(size_t extruder, float& a, float& b, float& limit) const noexcept
-{
-	if (extruder < MaxExtruders)
-	{
-		a = nonlinearExtrusionA[extruder];
-		b = nonlinearExtrusionB[extruder];
-		limit = nonlinearExtrusionLimit[extruder];
-		return true;
-	}
-	return false;
-}
-
 void Platform::SetNonlinearExtrusion(size_t extruder, float a, float b, float limit) noexcept
 {
-	if (extruder < MaxExtruders && nonlinearExtrusionLimit[extruder] > 0.0)
+	if (extruder < MaxExtruders && limit > 0.0)
 	{
-		nonlinearExtrusionLimit[extruder] = limit;
-		nonlinearExtrusionA[extruder] = a;
-		nonlinearExtrusionB[extruder] = b;
+		nonlinearExtrusion[extruder].limit = limit;
+		nonlinearExtrusion[extruder].A = a;
+		nonlinearExtrusion[extruder].B = b;
 	}
 }
 
diff --git a/src/Platform/Platform.h b/src/Platform/Platform.h
index a1f816da..201e10f2 100644
--- a/src/Platform/Platform.h
+++ b/src/Platform/Platform.h
@@ -303,6 +303,17 @@ struct AxisDriversConfig
 	DriverId driverNumbers[MaxDriversPerAxis];		// The driver numbers assigned - only the first numDrivers are meaningful
 };
 
+#if SUPPORT_NONLINEAR_EXTRUSION
+
+struct NonlinearExtrusion
+{
+	float A;
+	float B;
+	float limit;
+};
+
+#endif
+
 // The main class that defines the RepRap machine for the benefit of the other classes
 class Platform INHERIT_OBJECT_MODEL
 {
@@ -511,7 +522,7 @@ public:
 	void EnableAllSteppingDrivers() noexcept { steppingEnabledDriversBitmap = 0xFFFFFFFFu; }
 
 #if SUPPORT_NONLINEAR_EXTRUSION
-	bool GetExtrusionCoefficients(size_t extruder, float& a, float& b, float& limit) const noexcept;
+	const NonlinearExtrusion& GetExtrusionCoefficients(size_t extruder) const noexcept pre(extruder < MaxExtruders) { return nonlinearExtrusion[extruder]; }
 	void SetNonlinearExtrusion(size_t extruder, float a, float b, float limit) noexcept;
 #endif
 
@@ -737,7 +748,7 @@ private:
 #endif
 
 #if SUPPORT_NONLINEAR_EXTRUSION
-	float nonlinearExtrusionA[MaxExtruders], nonlinearExtrusionB[MaxExtruders], nonlinearExtrusionLimit[MaxExtruders];
+	NonlinearExtrusion nonlinearExtrusion[MaxExtruders];	// nonlinear extrusion coefficients
 #endif
 
 	DriverId extruderDrivers[MaxExtruders];					// the driver number assigned to each extruder