path: root/src/Movement/DriveMovement.cpp

/*
 * DriveMovement.cpp
 *
 *  Created on: 17 Jan 2015
 *      Author: David
 */

#include "DriveMovement.h"
#include "DDA.h"
#include "Move.h"
#include "StepTimer.h"
#include <Platform/RepRap.h>
#include <Math/Isqrt.h>
#include "Kinematics/LinearDeltaKinematics.h"

#if !MS_USE_FPU

// The code in this file relies on right shift of a signed operand being arithmetic shift
// Shifting generates fewer instructions than dividing by a constant power of 2 in ARM gcc even though gcc converts the division to other instructions.
// Arithmetic shift rounds towards minus infinity, so it doesn't give quite the same result as dividing when there is a remainder.
static_assert(((int32_t)-21 >> 1) == (int32_t)-11);
static_assert(((int64_t)-10000000001 >> 1) == (int64_t)-5000000001);

#endif

// Static members

DriveMovement *DriveMovement::freeList = nullptr;
unsigned int DriveMovement::numCreated = 0;

void DriveMovement::InitialAllocate(unsigned int num) noexcept
{
	while (num > numCreated)
	{
		freeList = new DriveMovement(freeList);
		++numCreated;
	}
}

// Allocate a DM, from the freelist if possible, else create a new one
DriveMovement *DriveMovement::Allocate(size_t p_drive, DMState st) noexcept
{
	DriveMovement * dm = freeList;
	if (dm != nullptr)
	{
		freeList = dm->nextDM;
		dm->nextDM = nullptr;
	}
	else
	{
		dm = new DriveMovement(nullptr);
		++numCreated;
	}
	dm->drive = (uint8_t)p_drive;
	dm->state = st;
	return dm;
}

// Constructors
DriveMovement::DriveMovement(DriveMovement *next) noexcept : nextDM(next)
{
}

// Non static members

void DriveMovement::DebugPrint() const noexcept
{
	const char c = (drive < reprap.GetGCodes().GetTotalAxes()) ? reprap.GetGCodes().GetAxisLetters()[drive] : (char)('0' + LogicalDriveToExtruder(drive));
	if (state != DMState::idle)
	{
#if MS_USE_FPU
		debugPrintf("DM%c%s dir=%c steps=%" PRIu32 " next=%" PRIu32 " rev=%" PRIu32 " interval=%" PRIu32 " ssl=%" PRIu32 " A=%.4e B=%.4e C=%.4e dsf=%.4e tsf=%.1f",
						c, (state == DMState::stepError) ? " ERR:" : ":", (direction) ? 'F' : 'B', totalSteps, nextStep, reverseStartStep, stepInterval, segmentStepLimit,
							(double)pA, (double)pB, (double)pC, (double)distanceSoFar, (double)timeSoFar);
		if (isDelta)
		{
			debugPrintf(" hmz0s=%.4e minusAaPlusBbTimesS=%.4e dSquaredMinusAsquaredMinusBsquared=%.4e drev=%.4e\n",
							(double)mp.delta.fHmz0s, (double)mp.delta.fMinusAaPlusBbTimesS, (double)mp.delta.fDSquaredMinusAsquaredMinusBsquaredTimesSsquared, (double)mp.delta.reverseStartDistance);
		}
		else if (isExtruder)
		{
			debugPrintf(" pa=%" PRIu32 " eed=%.4e ebf=%.4e\n", (uint32_t)mp.cart.pressureAdvanceK, (double)mp.cart.extraExtrusionDistance, (double)mp.cart.extrusionBroughtForwards);
		}
		else
		{
			debugPrintf("\n");
		}
#else
		debugPrintf("DM%c%s dir=%c steps=%" PRIu32 " next=%" PRIu32 " rev=%" PRIu32 " interval=%" PRIu32 " ssl=%" PRIu32 " A=%" PRIi64 " B=%" PRIi32 " C=%" PRIi32 " dsf=%" PRIu32 " tsf=%" PRIu32,
						c, (state == DMState::stepError) ? " ERR:" : ":", (direction) ? 'F' : 'B', totalSteps, nextStep, reverseStartStep, stepInterval, segmentStepLimit,
							iA, iB, iC, iDistanceSoFar, iTimeSoFar);
		if (isDelta)
		{
			debugPrintf(" hmz0sk=%" PRIi32 " minusAaPlusBbTimesS=%" PRIi32 " dSquaredMinusAsquaredMinusBsquared=%" PRIi64 " drev=%" PRIu32 "\n",
							mp.delta.hmz0sK, mp.delta.minusAaPlusBbTimesKs, mp.delta.dSquaredMinusAsquaredMinusBsquaredTimesKsquaredSsquared, mp.delta.iReverseStartDistance);
		}
		else if (isExtruder)
		{
			debugPrintf(" pa=%" PRIu32 " eed=%" PRIu32 " ebf=%.4e\n", mp.cart.iPressureAdvanceK, mp.cart.iExtraExtrusionDistance, (double)mp.cart.extrusionBroughtForwards);
		}
		else
		{
			debugPrintf("\n");
		}
#endif
	}
	else
	{
		debugPrintf("DM%c: not moving\n", c);
	}
}

// This is called when currentSegment has just been changed to a new segment. Return true if there is a new segment to execute.
bool DriveMovement::NewCartesianSegment() noexcept
{
	while (true)
	{
		if (currentSegment == nullptr)
		{
			return false;
		}

		// Work out the movement limit in steps
#if MS_USE_FPU
		pC = currentSegment->CalcC(mp.cart.effectiveMmPerStep);
		if (currentSegment->IsLinear())
		{
			// Set up pB, pC such that for forward motion, time = pB + pC * stepNumber
			pB = currentSegment->CalcLinearB(distanceSoFar, timeSoFar);
			state = DMState::cartLinear;
		}
		else
		{
			// Set up pA, pB, pC such that for forward motion, time = pB + sqrt(pA + pC * stepNumber)
			pA = currentSegment->CalcNonlinearA(distanceSoFar);
			pB = currentSegment->CalcNonlinearB(timeSoFar);
			state = (currentSegment->IsAccelerating()) ? DMState::cartAccel : DMState::cartDecelNoReverse;
		}

		distanceSoFar += currentSegment->GetSegmentLength();
		timeSoFar += currentSegment->GetSegmentTime();

		segmentStepLimit = (currentSegment->GetNext() == nullptr) ? totalSteps + 1 : (uint32_t)(distanceSoFar * mp.cart.effectiveStepsPerMm) + 1;
#else
		iC = currentSegment->CalcC(mp.cart.iEffectiveMmPerStepTimesK);
		if (currentSegment->IsLinear())
		{
			// Set up pB, pC such that for forward motion, time = pB + pC * stepNumber
			iB = currentSegment->CalcLinearB(iDistanceSoFar, iTimeSoFar);
			state = DMState::cartLinear;
		}
		else
		{
			// Set up pA, pB, pC such that for forward motion, time = pB + sqrt(pA + pC * stepNumber)
			iA = currentSegment->CalcNonlinearA(iDistanceSoFar);
			iB = currentSegment->CalcNonlinearB(iTimeSoFar);
			state = (currentSegment->IsAccelerating()) ? DMState::cartAccel : DMState::cartDecelNoReverse;
		}

		iDistanceSoFar += currentSegment->GetSegmentLength();
		iTimeSoFar += currentSegment->GetSegmentTime();

		segmentStepLimit = (currentSegment->GetNext() == nullptr) ? totalSteps + 1 : (uint32_t)(((iDistanceSoFar * (uint64_t)mp.cart.iEffectiveStepsPerMmTimesK)) >> MoveSegment::SFstepsPerMm) + 1;
#endif

		if (nextStep < segmentStepLimit)
		{
			return true;
		}

		currentSegment = currentSegment->GetNext();						// skip this segment
	}
}

#if SUPPORT_LINEAR_DELTA

// This is called when currentSegment has just been changed to a new segment. Return true if there is a new segment to execute.
bool DriveMovement::NewDeltaSegment(const DDA& dda) noexcept
{
	while (true)
	{
		if (currentSegment == nullptr)
		{
			return false;
		}

		const float stepsPerMm = reprap.GetPlatform().DriveStepsPerUnit(drive);
#if MS_USE_FPU
		pC = currentSegment->GetC()/stepsPerMm;		//TODO store the reciprocal to avoid the division
		if (currentSegment->IsLinear())
		{
			// Set up pB, pC such that for forward motion, time = pB + pC * (distanceMoved * steps/mm)
			pB = currentSegment->CalcLinearB(distanceSoFar, timeSoFar);
		}
		else
		{
			// Set up pA, pB, pC such that for forward motion, time = pB + sqrt(pA + pC * (distanceMoved * steps/mm))
			pA = currentSegment->CalcNonlinearA(distanceSoFar);
			pB = currentSegment->CalcNonlinearB(timeSoFar);
		}

		distanceSoFar += currentSegment->GetSegmentLength();
		timeSoFar += currentSegment->GetSegmentTime();

		// Work out whether we reverse in this segment and the movement limit in steps.
		// First check whether the first step in this segment is the previously-calculated reverse start step, and if so then do the reversal.
		if (nextStep == reverseStartStep)
		{
			direction = false;					// we must have been going up, so now we are going down
			directionChanged = true;
		}

		if (currentSegment->GetNext() == nullptr)
		{
			// This is the last segment, so the phase step limit is the number of total steps, and we can avoid some calculation
			segmentStepLimit = totalSteps + 1;
			state = (reverseStartStep <= totalSteps && nextStep < reverseStartStep) ? DMState::deltaForwardsReversing : DMState::deltaNormal;
		}
		else
		{
			// Work out how many whole steps we have moved up or down at the end of this segment
			const float sDx = distanceSoFar * dda.directionVector[0];
			const float sDy = distanceSoFar * dda.directionVector[1];
			int32_t netStepsAtEnd = (int32_t)floorf(fastSqrtf(mp.delta.fDSquaredMinusAsquaredMinusBsquaredTimesSsquared - fsquare(stepsPerMm) * (sDx * (sDx + mp.delta.fTwoA) + sDy * (sDy + mp.delta.fTwoB)))
												+ (distanceSoFar * dda.directionVector[2] - mp.delta.h0MinusZ0) * stepsPerMm);

			// If there is a reversal then we only ever move up by (reverseStartStep - 1) steps, so netStepsAtEnd should be less than reverseStartStep.
			// However, because of rounding error, it might possibly be equal.
			// If there is no reversal then reverseStartStep is set to totalSteps + 1, so netStepsAtEnd must again be less than reverseStartStep.
			if (netStepsAtEnd >= (int32_t)reverseStartStep)
			{
				netStepsAtEnd = (int32_t)(reverseStartStep - 1);			// correct the rounding error - we know that reverseStartStep cannot be 0 so subtracting 1 is safe
			}

			if (!direction)
			{
				// We are going down so any reversal has already happened
				state = DMState::deltaNormal;
				segmentStepLimit = (nextStep >= reverseStartStep)
									? (uint32_t)((int32_t)(2 * reverseStartStep) - netStepsAtEnd)		// we went up (reverseStartStep-1) steps, now we are going down to netStepsAtEnd
										: (uint32_t)(-netStepsAtEnd);									// we are just going down to netStepsAtEnd
			}
			else if (distanceSoFar <= mp.delta.reverseStartDistance)
			{
				// This segment is purely upwards motion of the tower
				state = DMState::deltaNormal;
				segmentStepLimit = (uint32_t)(netStepsAtEnd + 1);
			}
			else
			{
				// This segment ends with reverse motion
				segmentStepLimit = (uint32_t)((int32_t)(2 * reverseStartStep) - netStepsAtEnd);
				state = DMState::deltaForwardsReversing;
			}
		}
#else
		iC = currentSegment->GetC()/stepsPerMm;		//TODO store the reciprocal to avoid the division? Use a scaling factor for C
		if (currentSegment->IsLinear())
		{
			// Set up pB, pC such that for forward motion, time = pB + pC * (distanceMoved * steps/mm)
			iB = currentSegment->CalcLinearB(iDistanceSoFar, iTimeSoFar);
		}
		else
		{
			// Set up pA, pB, pC such that for forward motion, time = pB + sqrt(pA + pC * (distanceMoved * steps/mm))
			iA = currentSegment->CalcNonlinearA(iDistanceSoFar);
			iB = currentSegment->CalcNonlinearB(iTimeSoFar);
		}

		const uint32_t startDistance = iDistanceSoFar;
		iDistanceSoFar += currentSegment->GetSegmentLength();
		iTimeSoFar += currentSegment->GetSegmentTime();

		// Work out whether we reverse in this segment and the movement limit in steps
		const float sDx = iDistanceSoFar * dda.directionVector[0];	//TODO avoid float maths
		const float sDy = iDistanceSoFar * dda.directionVector[1];	//TODO avoid float maths
		const int32_t netStepsAtEnd = (int32_t)(isqrt64(mp.delta.dSquaredMinusAsquaredMinusBsquaredTimesKsquaredSsquared - fsquare(stepsPerMm) * (sDx * (sDx + mp.delta.fTwoA) + sDy * (sDy + mp.delta.fTwoB)))
								 	 	 	 	 + (iDistanceSoFar * dda.directionVector[2] - mp.delta.h0MinusZ0) * stepsPerMm);	//TODO avoid float maths

		if (mp.delta.iReverseStartDistance <= (int32_t)startDistance)
		{
			// This segment is purely downwards motion and we want the greater of the two quadratic solutions. There may have been upwards motion earlier in the move.
			if (direction)
			{
				direction = false;
				directionChanged = true;
			}
			state = DMState::deltaReverse;
			segmentStepLimit = (currentSegment->GetNext() == nullptr) ? totalSteps + 1
								: (reverseStartStep <= totalSteps) ? (uint32_t)((int32_t)(2 * reverseStartStep) - netStepsAtEnd)
									: 1 - netStepsAtEnd;
		}
		else if ((int32_t)iDistanceSoFar <= mp.delta.iReverseStartDistance)
		{
			// This segment is purely upwards motion of the tower and we want the lower quadratic solution
			state = DMState::deltaForwardsNoReverse;
			segmentStepLimit = (currentSegment->GetNext() == nullptr) ? totalSteps + 1 : (uint32_t)(netStepsAtEnd + 1);
		}
		else
		{
			// This segment ends with reverse motion. We want the lower quadratic solution initially.
			segmentStepLimit = (currentSegment->GetNext() == nullptr) ? totalSteps + 1 : (uint32_t)((int32_t)(2 * reverseStartStep) - netStepsAtEnd);
			state = DMState::deltaForwardsReversing;
		}
#endif

		if (segmentStepLimit > nextStep)
		{
			return true;
		}

		currentSegment = currentSegment->GetNext();
	}
}

#endif // SUPPORT_LINEAR_DELTA

// This is called when currentSegment has just been changed to a new segment. Return true if there is a new segment to execute.
bool DriveMovement::NewExtruderSegment() noexcept
{
	while (true)
	{
		if (currentSegment == nullptr)
		{
			return false;
		}

#if MS_USE_FPU
		const float startDistance = distanceSoFar;
		const float startTime = timeSoFar;

		distanceSoFar += currentSegment->GetSegmentLength();
		timeSoFar += currentSegment->GetSegmentTime();

		pC = currentSegment->CalcC(mp.cart.effectiveMmPerStep);
		if (currentSegment->IsLinear())
		{
			// Set up pB, pC such that for forward motion, time = pB + pC * stepNumber
			pB = currentSegment->CalcLinearB(startDistance, startTime);
			state = DMState::cartLinear;
		}
		else
		{
			// Set up pA, pB, pC such that for forward motion, time = pB + sqrt(pA + pC * stepNumber)
			pA = currentSegment->CalcNonlinearA(startDistance, mp.cart.pressureAdvanceK);
			pB = currentSegment->CalcNonlinearB(startTime, mp.cart.pressureAdvanceK);
			if (currentSegment->IsAccelerating())
			{
				// Extruders have a single acceleration segment. We need to add the extra extrusion distance due to pressure advance to the extrusion distance.
				distanceSoFar += mp.cart.extraExtrusionDistance;
				state = DMState::cartAccel;
			}
			else
			{
				// This is the single decelerating segment. If it includes pressure advance then it may include reversal.
				state = (reverseStartStep <= totalSteps) ? DMState::cartDecelForwardsReversing : DMState::cartDecelNoReverse;
			}
		}

		// Work out the movement limit in steps
		segmentStepLimit = ((currentSegment->GetNext() == nullptr) ? totalSteps : (uint32_t)(distanceSoFar * mp.cart.effectiveStepsPerMm)) + 1;
#else
		const uint32_t startDistance = iDistanceSoFar;
		const uint32_t startTime = iTimeSoFar;

		// Work out the movement limit in steps
		iDistanceSoFar += currentSegment->GetSegmentLength();
		iTimeSoFar += currentSegment->GetSegmentTime();

		iC = currentSegment->CalcC(mp.cart.iEffectiveMmPerStepTimesK);
		if (currentSegment->IsLinear())
		{
			// Set up pB, pC such that for forward motion, time = pB + pC * stepNumber
			iB = currentSegment->CalcLinearB(startDistance, startTime);
			state = DMState::cartLinear;
		}
		else
		{
			// Set up pA, pB, pC such that for forward motion, time = pB + sqrt(pA + pC * stepNumber)
			iA = currentSegment->CalcNonlinearA(startDistance, mp.cart.iPressureAdvanceK);
			iB = currentSegment->CalcNonlinearB(startTime, mp.cart.iPressureAdvanceK);
			if (currentSegment->IsAccelerating())
			{
				// Extruders have a single acceleration segment. We need to add the extra extrusion distance due to pressure advance to the extrusion distance.
				iDistanceSoFar += mp.cart.iExtraExtrusionDistance;
				state = DMState::cartAccel;
			}
			else
			{
				// This is the single decelerating segment. If it includes pressure advance then it may include reversal.
				state = DMState::cartDecelForwardsReversing;			// assume that it may reverse
			}
		}

		segmentStepLimit = ((currentSegment->GetNext() == nullptr) ? totalSteps : (uint32_t)((iDistanceSoFar * (uint64_t)mp.cart.iEffectiveStepsPerMmTimesK)) >> MoveSegment::SFstepsPerMm) + 1;
#endif

		if (nextStep < segmentStepLimit)
		{
			return true;
		}

		currentSegment = currentSegment->GetNext();						// skip this segment
	}
}

// Prepare this DM for a Cartesian axis move, returning true if there are steps to do
bool DriveMovement::PrepareCartesianAxis(const DDA& dda, const PrepParams& params) noexcept
{
#if MS_USE_FPU
	distanceSoFar = 0.0;
	timeSoFar = 0.0;
	mp.cart.pressureAdvanceK = 0.0;
	// We can't use directionVector here because those values relate to Cartesian space, whereas we may be CoreXY etc.
	mp.cart.effectiveStepsPerMm = (float)totalSteps/dda.totalDistance;
	mp.cart.effectiveMmPerStep = 1.0/mp.cart.effectiveStepsPerMm;
#else
	iDistanceSoFar = 0;
	iTimeSoFar = 0;
	mp.cart.iPressureAdvanceK = 0;
	// We can't use directionVector here because those values relate to Cartesian space, whereas we may be CoreXY etc.
	const float stepsTimesK = (float)((uint64_t)totalSteps << MoveSegment::SFstepsPerMm);
	mp.cart.iEffectiveStepsPerMmTimesK = stepsTimesK/dda.totalDistance;
	mp.cart.iEffectiveMmPerStepTimesK = dda.totalDistance/stepsTimesK;
#endif
	isDelta = false;
	isExtruder = false;
	currentSegment = (dda.shapedSegments != nullptr) ? dda.shapedSegments : dda.unshapedSegments;
	nextStep = 0;									// must do this before calling NewCartesianSegment

	if (!NewCartesianSegment())
	{
		return false;
	}

	// Prepare for the first step
	nextStepTime = 0;
	stepsTakenThisSegment = 0;						// no steps taken yet since the start of the segment
	stepsTillRecalc = 0;							// so that we don't skip the calculation
	reverseStartStep = totalSteps + 1;				// no reverse phase
	return CalcNextStepTime(dda);
}

#if SUPPORT_LINEAR_DELTA

// Prepare this DM for a Delta axis move, returning true if there are steps to do
bool DriveMovement::PrepareDeltaAxis(const DDA& dda, const PrepParams& params) noexcept
{
	const float stepsPerMm = reprap.GetPlatform().DriveStepsPerUnit(drive);
	const float A = params.initialX - params.dparams->GetTowerX(drive);
	const float B = params.initialY - params.dparams->GetTowerY(drive);
	const float aAplusbB = A * dda.directionVector[X_AXIS] + B * dda.directionVector[Y_AXIS];
	const float dSquaredMinusAsquaredMinusBsquared = params.dparams->GetDiagonalSquared(drive) - fsquare(A) - fsquare(B);
	const float h0MinusZ0 = fastSqrtf(dSquaredMinusAsquaredMinusBsquared);

#if MS_USE_FPU
	mp.delta.h0MinusZ0 = h0MinusZ0;
	mp.delta.fTwoA = 2.0 * A;
	mp.delta.fTwoB = 2.0 * B;
	mp.delta.fHmz0s = h0MinusZ0 * stepsPerMm;
	mp.delta.fMinusAaPlusBbTimesS = -(aAplusbB * stepsPerMm);
	mp.delta.fDSquaredMinusAsquaredMinusBsquaredTimesSsquared = dSquaredMinusAsquaredMinusBsquared * fsquare(stepsPerMm);

	// Calculate the distance at which we need to reverse direction.
	if (params.a2plusb2 <= 0.0)
	{
		// Pure Z movement. We can't use the main calculation because it divides by params.a2plusb2.
		direction = (dda.directionVector[Z_AXIS] >= 0.0);
		mp.delta.reverseStartDistance = (direction) ? dda.totalDistance + 1.0 : -1.0;	// so that we never reverse and NewDeltaSegment knows which way we are going
		reverseStartStep = totalSteps + 1;
	}
	else
	{
		// The distance to reversal is the solution to a quadratic equation. One root corresponds to the carriages being below the bed,
		// the other root corresponds to the carriages being above the bed.
		const float drev = ((dda.directionVector[Z_AXIS] * fastSqrtf(params.a2plusb2 * params.dparams->GetDiagonalSquared(drive) - fsquare(A * dda.directionVector[Y_AXIS] - B * dda.directionVector[X_AXIS])))
							- aAplusbB)/params.a2plusb2;
		mp.delta.reverseStartDistance = drev;
		if (drev <= 0.0)
		{
			// No reversal, going down
			reverseStartStep = totalSteps + 1;
			direction = false;
		}
		else if (drev >= dda.totalDistance)
		{
			// No reversal, going up
			reverseStartStep = totalSteps + 1;
			direction = true;
		}
		else																	// the reversal point is within range
		{
			// Calculate how many steps we need to move up before reversing
			const float hrev = dda.directionVector[Z_AXIS] * drev + fastSqrtf(dSquaredMinusAsquaredMinusBsquared - 2 * drev * aAplusbB - params.a2plusb2 * fsquare(drev));
			const int32_t numStepsUp = (int32_t)((hrev - mp.delta.h0MinusZ0) * stepsPerMm);

			// We may be going down but almost at the peak height already, in which case we don't really have a reversal.
			// However, we could be going up by a whole step due to rounding, so we need to check the direction
			if (numStepsUp < 1)
			{
				if (direction)
				{
					mp.delta.reverseStartDistance = dda.totalDistance + 1.0;	// indicate that there is no reversal
				}
				else
				{
					mp.delta.reverseStartDistance = -1.0;						// so that we know we have reversed already
					reverseStartStep = totalSteps + 1;
				}
			}
			else if (direction && (uint32_t)numStepsUp <= totalSteps)
			{
				// If numStepsUp == totalSteps then the reverse segment is too small to do.
				// If numStepsUp < totalSteps then there has been a rounding error, because we are supposed to move up more than the calculated number of steps we move up.
				// This can happen if the calculated reversal is very close to the end of the move, because we round the final step positions to the nearest step, which may be up.
				// Either way, don't do a reverse segment.
				reverseStartStep = totalSteps + 1;
				mp.delta.reverseStartDistance = dda.totalDistance + 1.0;
			}
			else
			{
				reverseStartStep = (uint32_t)numStepsUp + 1;

				// Correct the initial direction and the total number of steps
				if (direction)
				{
					// Net movement is up, so we will go up first and then down by a lesser amount
					totalSteps = (2 * (uint32_t)numStepsUp) - totalSteps;
				}
				else
				{
					// Net movement is down, so we will go up first and then down by a greater amount
					direction = true;
					totalSteps = (2 * (uint32_t)numStepsUp) + totalSteps;
				}
			}
		}
	}

	distanceSoFar = 0.0;
	timeSoFar = 0.0;
#else
	mp.delta.h0MinusZ0 = h0MinusZ0;		//TODO change to integer
	mp.delta.fTwoA = 2.0 * A;			//TODO change to integer
	mp.delta.fTwoB = 2.0 * B;			//TODO change to integer
	mp.delta.hmz0sK = lrintf(h0MinusZ0 * stepsPerMm * MoveSegment::Kdelta);
	mp.delta.minusAaPlusBbTimesKs = -lrintf(aAplusbB * stepsPerMm * MoveSegment::Kdelta);
	mp.delta.dSquaredMinusAsquaredMinusBsquaredTimesKsquaredSsquared = llrintf(dSquaredMinusAsquaredMinusBsquared * fsquare(stepsPerMm * MoveSegment::Kdelta));

	// Calculate the distance at which we need to reverse direction.
	if (params.a2plusb2 <= 0.0)
	{
		// Pure Z movement. We can't use the main calculation because it divides by a2plusb2.
		direction = (dda.directionVector[Z_AXIS] >= 0.0);
		const float reverseStartDistance = (direction) ? dda.totalDistance + 1.0 : -1.0;	// so that we never reverse and NewDeltaSegment knows which way we are going
		mp.delta.iReverseStartDistance = (int32_t)(reverseStartDistance * MoveSegment::Kdistance);
		reverseStartStep = totalSteps + 1;
	}
	else
	{
		// The distance to reversal is the solution to a quadratic equation. One root corresponds to the carriages being below the bed,
		// the other root corresponds to the carriages being above the bed.
		const float drev = ((dda.directionVector[Z_AXIS] * fastSqrtf(params.a2plusb2 * params.dparams->GetDiagonalSquared(drive) - fsquare(A * dda.directionVector[Y_AXIS] - B * dda.directionVector[X_AXIS])))
							- aAplusbB)/params.a2plusb2;
		mp.delta.iReverseStartDistance = (int32_t)(drev * MoveSegment::Kdistance);
		if (drev > 0.0 && drev < dda.totalDistance)						// if the reversal point is within range
		{
			// Calculate how many steps we need to move up before reversing
			const float hrev = dda.directionVector[Z_AXIS] * drev + fastSqrtf(dSquaredMinusAsquaredMinusBsquared - 2 * drev * aAplusbB - params.a2plusb2 * fsquare(drev));
			const int32_t numStepsUp = (int32_t)((hrev - mp.delta.h0MinusZ0) * stepsPerMm);

			// We may be almost at the peak height already, in which case we don't really have a reversal.
			if (numStepsUp < 1)
			{
				mp.delta.iReverseStartDistance = -1;					// so that we know we have reversed already
				reverseStartStep = totalSteps + 1;
				direction = false;
			}
			else
			{
				reverseStartStep = (uint32_t)numStepsUp + 1;

				// Correct the initial direction and the total number of steps
				if (direction)
				{
					// Net movement is up, so we will go up first and then down by a lesser amount
					totalSteps = (2 * numStepsUp) - totalSteps;
				}
				else
				{
					// Net movement is down, so we will go up first and then down by a greater amount
					direction = true;
					totalSteps = (2 * numStepsUp) + totalSteps;
				}
			}
		}
		else
		{
			// No reversal
			reverseStartStep = totalSteps + 1;
			direction = (drev >= 0.0);
		}
	}

	iDistanceSoFar = 0;
	iTimeSoFar = 0;
#endif

	isDelta = true;
	currentSegment = (dda.shapedSegments != nullptr) ? dda.shapedSegments : dda.unshapedSegments;

	nextStep = 0;									// must do this before calling NewDeltaSegment
	if (!NewDeltaSegment(dda))
	{
		return false;
	}

	// Prepare for the first step
	nextStepTime = 0;
	stepsTakenThisSegment = 0;						// no steps taken yet since the start of the segment
	stepsTillRecalc = 0;							// so that we don't skip the calculation
	return CalcNextStepTime(dda);
}

#endif	// SUPPORT_LINEAR_DELTA

// 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
{
	const float stepsPerMm = reprap.GetPlatform().DriveStepsPerUnit(drive);
	const float effStepsPerMm = stepsPerMm * fabsf(dda.directionVector[drive]);
	const float effMmPerStep = 1.0/effStepsPerMm;

	ExtruderShaper& shaper = reprap.GetMove().GetExtruderShaper(LogicalDriveToExtruder(drive));
	float forwardDistance =	mp.cart.extrusionBroughtForwards = shaper.GetExtrusionPending()/dda.directionVector[drive];
	float reverseDistance;

#if MS_USE_FPU
	mp.cart.effectiveStepsPerMm = effStepsPerMm;
	mp.cart.effectiveMmPerStep = effMmPerStep;
	distanceSoFar = forwardDistance;
	timeSoFar = 0.0;

	// Calculate the total forward and reverse movement distances
	if (dda.flags.usePressureAdvance && shaper.GetKclocks() > 0.0)
	{
		// We are using nonzero pressure advance. Movement must be forwards.
		mp.cart.pressureAdvanceK = shaper.GetKclocks();
		mp.cart.extraExtrusionDistance = mp.cart.pressureAdvanceK * (dda.topSpeed - dda.startSpeed);
		forwardDistance += mp.cart.extraExtrusionDistance;

# if 0 //SHAPE_EXTRUSION
		forwardDistance += params.shaped.decelStartDistance;
		reverseDistance = 0.0;

		// Find the deceleration segments
		const MoveSegment *decelSeg = dda.unshapedSegments;
		while (decelSeg != nullptr && (decelSeg->IsLinear() || decelSeg->IsAccelerating()))
		{
			decelSeg = decelSeg->GetNext();
		}

		float lastUncorrectedSpeed = dda.topSpeed;
		float lastDistance = forwardDistance;
		while (decelSeg != nullptr)
		{
			const float initialDecelSpeed = lastUncorrectedSpeed - mp.cart.pressureAdvanceK * decelSeg->deceleration;
			if (initialDecelSpeed <= 0.0)
			{
				// This entire deceleration segment is in reverse
				reverseDistance += ((0.5 * params.unshaped.deceleration * params.unshaped.decelClocks) - initialDecelSpeed) * params.unshaped.decelClocks;
			}
			else
			{
				const float timeToReverse = initialDecelSpeed * ((-0.5) * decelSeg->GetC());	// 'c' is -2/deceleration, so -0.5*c is 1/deceleration
				if (timeToReverse < params.unshaped.decelClocks)
				{
					// There is a reversal, although it could be tiny
					const float distanceToReverse = fsquare(initialDecelSpeed) * decelSeg->GetC() * (-0.25);	// because (v^2-u^2) = 2as, so if v=0 then s=-u^2/2a = u^2/2d = -0.25*u^2*c
					forwardDistance += params.unshaped.decelStartDistance + distanceToReverse;
					reverseDistance = 0.5 * params.unshaped.deceleration * fsquare(params.unshaped.decelClocks - timeToReverse);	// because s = 0.5*a*t^2
				}
				else
				{
					// No reversal
					forwardDistance += dda.totalDistance - (mp.cart.pressureAdvanceK * params.unshaped.deceleration * params.unshaped.decelClocks);
					reverseDistance = 0.0;
				}
			}

		}
# else
		// Check if there is a reversal in the deceleration segment
		// There is at most one deceleration segment in the unshaped segments
		const MoveSegment *decelSeg = dda.unshapedSegments;
		while (decelSeg != nullptr && (decelSeg->IsLinear() || decelSeg->IsAccelerating()))
		{
			decelSeg = decelSeg->GetNext();
		}

		if (decelSeg == nullptr)
		{
			forwardDistance += dda.totalDistance;			// no deceleration segment
			reverseDistance = 0.0;
		}
		else
		{
			const float initialDecelSpeed = dda.topSpeed - mp.cart.pressureAdvanceK * params.unshaped.deceleration;
			if (initialDecelSpeed <= 0.0)
			{
				// The entire deceleration segment is in reverse
				forwardDistance += params.unshaped.decelStartDistance;
				reverseDistance = ((0.5 * params.unshaped.deceleration * params.unshaped.decelClocks) - initialDecelSpeed) * params.unshaped.decelClocks;
			}
			else
			{
				const float timeToReverse = initialDecelSpeed * ((-0.5) * decelSeg->GetC());	// 'c' is -2/deceleration, so -0.5*c is 1/deceleration
				if (timeToReverse < params.unshaped.decelClocks)
				{
					// There is a reversal, although it could be tiny
					const float distanceToReverse = fsquare(initialDecelSpeed) * decelSeg->GetC() * (-0.25);	// because (v^2-u^2) = 2as, so if v=0 then s=-u^2/2a = u^2/2d = -0.25*u^2*c
					forwardDistance += params.unshaped.decelStartDistance + distanceToReverse;
					reverseDistance = 0.5 * params.unshaped.deceleration * fsquare(params.unshaped.decelClocks - timeToReverse);	// because s = 0.5*a*t^2
				}
				else
				{
					// No reversal
					forwardDistance += dda.totalDistance - (mp.cart.pressureAdvanceK * params.unshaped.deceleration * params.unshaped.decelClocks);
					reverseDistance = 0.0;
				}
			}
		}
# endif
	}
	else
	{
		// No pressure advance. Movement may be backwards but this still counts as forward distance in the calculations.
		mp.cart.pressureAdvanceK = mp.cart.extraExtrusionDistance = 0.0;
		forwardDistance += dda.totalDistance;
		reverseDistance = 0.0;
	}
#else
	mp.cart.iEffectiveStepsPerMmTimesK = lrintf(effStepsPerMm * (float)(1u << MoveSegment::SFstepsPerMm));
	mp.cart.iEffectiveMmPerStepTimesK = lrintf(effMmPerStep * (float)(1u << MoveSegment::SFstepsPerMm));
	iTimeSoFar = 0;

	// Calculate the total forward and reverse movement distances
	//TODO distances as integer?

	if (dda.flags.usePressureAdvance && shaper.GetKclocks() > 0.0)
	{
		// We are using nonzero pressure advance. Movement must be forwards.
		mp.cart.iPressureAdvanceK = shaper.GetKclocks();
		const float extraExtrusionDistance = (float)mp.cart.iPressureAdvanceK * (dda.topSpeed - dda.startSpeed);
		mp.cart.iExtraExtrusionDistance = lrintf(extraExtrusionDistance * (float)(1u << MoveSegment::SFdistance));
		forwardDistance += extraExtrusionDistance;

		// Check if there is a reversal in the deceleration segment
		// There is at most one deceleration segment in the unshaped segments
		const MoveSegment *decelSeg = dda.unshapedSegments;
		while (decelSeg != nullptr && (decelSeg->IsLinear() || decelSeg->IsAccelerating()))
		{
			decelSeg = decelSeg->GetNext();
		}

		if (decelSeg == nullptr)
		{
			forwardDistance += dda.totalDistance;			// no deceleration segment
			reverseDistance = 0.0;
		}
		else
		{
			const float initialDecelSpeed = dda.topSpeed - (float)mp.cart.iPressureAdvanceK * params.unshaped.deceleration;
			if (initialDecelSpeed <= 0.0)
			{
				// The entire deceleration segment is in reverse
				forwardDistance += params.unshaped.decelStartDistance;
				reverseDistance = ((0.5 * params.unshaped.deceleration * params.unshaped.decelClocks) - initialDecelSpeed) * params.unshaped.decelClocks;
			}
			else
			{
				const float timeToReverse = initialDecelSpeed * ((-0.5) * decelSeg->GetC());	// 'c' is -2/deceleration, so -0.5*c is 1/deceleration
				if (timeToReverse < params.unshaped.decelClocks)
				{
					// There is a reversal, although it could be tiny
					const float distanceToReverse = fsquare(initialDecelSpeed) * decelSeg->GetC() * (-0.25);	// because (v^2-u^2) = 2as, so if v=0 then s=-u^2/2a = u^2/2d = -0.25*u^2*c
					forwardDistance += params.unshaped.decelStartDistance + distanceToReverse;
					reverseDistance = 0.5 * params.unshaped.deceleration * fsquare(params.unshaped.decelClocks - timeToReverse);	// because s = 0.5*a*t^2
				}
				else
				{
					// No reversal
					forwardDistance += dda.totalDistance - ((float)mp.cart.iPressureAdvanceK * params.unshaped.deceleration * params.unshaped.decelClocks);
					reverseDistance = 0.0;
				}
			}
		}
	}
	else
	{
		// No pressure advance. Movement may be backwards but this still counts as forward distance in the calculations.
		mp.cart.iPressureAdvanceK = mp.cart.iExtraExtrusionDistance = 0;
		forwardDistance += dda.totalDistance;
		reverseDistance = 0.0;
	}
#endif

	// Check whether there are any steps at all
	const float forwardSteps = forwardDistance * effStepsPerMm;
	if (reverseDistance > 0.0)
	{
		const float netDistance = forwardDistance - reverseDistance;
		const int32_t iFwdSteps = (int32_t)forwardSteps;
		int32_t netSteps = (int32_t)(netDistance * effStepsPerMm);
		if (netSteps == 0 && iFwdSteps == 0)
		{
			// No movement at all
			nextStep = totalSteps = 0;
			reverseStartStep = 1;
			shaper.SetExtrusionPending(netDistance * dda.directionVector[drive]);
			return false;
		}

		// Note, netSteps may be negative for e.g. a deceleration-only move
		if (netSteps == iFwdSteps)
		{
			// The reverse segment is very small, so ignore it
			totalSteps = (uint32_t)iFwdSteps;
			reverseStartStep = totalSteps + 1;
		}
		else
		{
			// We know that netSteps <= iFwdSteps
			reverseStartStep = iFwdSteps + 1;
			// Round up netSteps because we don't want to overshoot the reverse movement.
			const float extrusionPending = netDistance - (float)netSteps * effMmPerStep;
			if (extrusionPending > 0.05 * effMmPerStep)
			{
				++netSteps;
			}
			totalSteps = (uint32_t)((int32_t)(2 * reverseStartStep) - netSteps - 2);
		}
		shaper.SetExtrusionPending((netDistance - (float)netSteps * effMmPerStep) * dda.directionVector[drive]);
	}
	else
	{
		if (forwardSteps >= 1.0)
		{
			totalSteps = (uint32_t)forwardSteps;
			shaper.SetExtrusionPending((forwardDistance - (float)totalSteps * effMmPerStep) * dda.directionVector[drive]);
		}
		else
		{
			// No steps at all, or negative forward steps which I think should be impossible unless the steps/mm is changed
			nextStep = totalSteps = 0;
			reverseStartStep = 1;
			shaper.SetExtrusionPending(forwardDistance * dda.directionVector[drive]);
			return false;
		}
		reverseStartStep = totalSteps + 1;			// no reverse phase
	}

	currentSegment = dda.unshapedSegments;
	isDelta = false;
	isExtruder = true;

	nextStep = 0;									// must do this before calling NewExtruderSegment
	if (!NewExtruderSegment())
	{
		return false;								// this should not happen because we have already determined that there are steps to do
	}

	// Prepare for the first step
	nextStepTime = 0;
	stepsTakenThisSegment = 0;						// no steps taken yet since the start of the segment
	stepsTillRecalc = 0;							// so that we don't skip the calculation
	return CalcNextStepTime(dda);
}

#if MS_USE_FPU

// Version of fastSqrtf that allows for slightly negative operands caused by rounding error
static inline float fastLimSqrtf(float f) noexcept
{
	return (f > 0.0) ? fastSqrtf(f) : 0.0;
}

#else

static inline uint32_t LimISqrt64(int64_t num) noexcept
{
	return (num <= 0) ? 0 : isqrt64((uint64_t)num);
}

#endif

// Calculate and store the time since the start of the move when the next step for the specified DriveMovement is due.
// We have already incremented nextStep and checked that it does not exceed totalSteps, so at least one more step is due
// Return true if all OK, false to abort this move because the calculation has gone wrong
bool DriveMovement::CalcNextStepTimeFull(const DDA &dda) noexcept
pre(nextStep <= totalSteps; stepsTillRecalc == 0)
{
	uint32_t shiftFactor = 0;									// assume single stepping

	{
		uint32_t stepsToLimit = segmentStepLimit - nextStep;
		// If there are no more steps left in this segment, skip to the next segment and use single stepping
		if (stepsToLimit == 0)
		{
			currentSegment = currentSegment->GetNext();
			const bool more =
#if SUPPORT_LINEAR_DELTA
								(isDelta) ? NewDeltaSegment(dda) :
#endif
									(isExtruder) ? NewExtruderSegment()
										: NewCartesianSegment();
			if (!more)
			{
				state = DMState::stepError;
				nextStep += 100000000;							// so we can tell what happened in the debug print
				return false;
			}
			// Leave shiftFactor set to 0 so that we compute a single step time, because the interval will have changed
			stepsTakenThisSegment = 1;							// this will be the first step in this segment
		}
		else if (stepsTakenThisSegment < 2)
		{
			// Reasons why we always use single stepping until we are on the third step in a segment:
			// 1. On the very first step of a move we don't know what the step interval is, so we must use single stepping for the first step.
			// 2. For extruders the step interval calculated for the very first step may be very small because of overdue extrusion,
			//    so we don't have a reliable step interval until we have calculated 2 steps.
			// 3. When starting a subsequent segment there may be a discontinuity due to rounding error,
			//    so the step interval calculated after the first step in a subsequent phase is not reliable.
			++stepsTakenThisSegment;
		}
		else
		{
			if (reverseStartStep < segmentStepLimit && nextStep < reverseStartStep)
			{
				stepsToLimit = reverseStartStep - nextStep;
			}

			if (stepsToLimit > 1 && stepInterval < DDA::MinCalcInterval)
			{
				if (stepInterval < DDA::MinCalcInterval/4 && stepsToLimit > 8)
				{
					shiftFactor = 3;							// octal stepping
				}
				else if (stepInterval < DDA::MinCalcInterval/2 && stepsToLimit > 4)
				{
					shiftFactor = 2;							// quad stepping
				}
				else if (stepsToLimit > 2)
				{
					shiftFactor = 1;							// double stepping
				}
			}
		}
	}

	stepsTillRecalc = (1u << shiftFactor) - 1u;					// store number of additional steps to generate

#if MS_USE_FPU
	float nextCalcStepTime;
#else
	uint32_t iNextCalcStepTime;
#endif

	// Work out the time of the step
	switch (state)
	{
	case DMState::cartLinear:									// linear steady speed
#if MS_USE_FPU
		nextCalcStepTime = pB + (float)(nextStep + stepsTillRecalc) * pC;
#else
		iNextCalcStepTime = iB + (nextStep + stepsTillRecalc) * iC;	//TODO ??scaling factor for iC ?
#endif
		break;

	case DMState::cartAccel:									// Cartesian accelerating
#if MS_USE_FPU
		nextCalcStepTime = pB + fastLimSqrtf(pA + pC * (float)(nextStep + stepsTillRecalc));
#else
		iNextCalcStepTime = iB + LimISqrt64(iA + iC * (nextStep + stepsTillRecalc));	//TODO ??scaling factor for iC ?
#endif
		break;

	case DMState::cartDecelForwardsReversing:
		if (nextStep + stepsTillRecalc < reverseStartStep)
		{
#if MS_USE_FPU
			nextCalcStepTime = pB - fastLimSqrtf(pA + pC * (float)(nextStep + stepsTillRecalc));
#else
			iNextCalcStepTime = iB - LimISqrt64(iA + iC * (nextStep + stepsTillRecalc));	//TODO ??scaling factor for iC ?
#endif
			break;
		}

		direction = false;
		directionChanged = true;
		state = DMState::cartDecelReverse;
		// no break
	case DMState::cartDecelReverse:								// Cartesian decelerating, reverse motion. Convert the steps to int32_t because the net steps may be negative.
#if MS_USE_FPU
		nextCalcStepTime = pB + fastLimSqrtf(pA + pC * (float)((2 * (int32_t)(reverseStartStep - 1)) - (int32_t)(nextStep + stepsTillRecalc)));
#else
		iNextCalcStepTime = iB + LimISqrt64(iA + iC * ((2 * (int32_t)(reverseStartStep - 1)) - (int32_t)(nextStep + stepsTillRecalc)));	//TODO ??scaling factor for iC ?
#endif
		break;

	case DMState::cartDecelNoReverse:							// Cartesian accelerating with no reversal
#if MS_USE_FPU
		nextCalcStepTime = pB - fastLimSqrtf(pA + pC * (float)(nextStep + stepsTillRecalc));
#else
		iNextCalcStepTime = iB - LimISqrt64(iA + iC * (nextStep + stepsTillRecalc));	//TODO ??scaling factor for iC ?
#endif
		break;

	case DMState::deltaForwardsReversing:						// moving forwards
		if (nextStep == reverseStartStep)
		{
			direction = false;
			directionChanged = true;
			state = DMState::deltaNormal;
		}
		// no break
	case DMState::deltaNormal:
		// Calculate d*s where d = distance the head has travelled, s = steps/mm for this drive
		{
#if MS_USE_FPU
			const float steps = (float)(1u << shiftFactor);
			if (direction)
			{
				mp.delta.fHmz0s += steps;						// get new carriage height above Z in steps
			}
			else
			{
				mp.delta.fHmz0s -= steps;						// get new carriage height above Z in steps
			}

			const float hmz0sc = mp.delta.fHmz0s * dda.directionVector[Z_AXIS];
			const float t1 = mp.delta.fMinusAaPlusBbTimesS + hmz0sc;
			const float t2a = mp.delta.fDSquaredMinusAsquaredMinusBsquaredTimesSsquared - fsquare(mp.delta.fHmz0s) + fsquare(t1);
			// Due to rounding error we can end up trying to take the square root of a negative number if we do not take precautions here
			const float t2 = fastLimSqrtf(t2a);
			const float ds = (direction) ? t1 - t2 : t1 + t2;

			// Now feed ds into the step algorithm for Cartesian motion
			if (ds < 0.0)
			{
				state = DMState::stepError;
				nextStep += 110000000;							// so that we can tell what happened in the debug print
				return false;
			}

			const float pCds = pC * ds;
			nextCalcStepTime = (currentSegment->IsLinear()) ? pB + pCds
								: (currentSegment->IsAccelerating()) ? pB + fastLimSqrtf(pA + pCds)
									 : pB - fastLimSqrtf(pA + pCds);
			//if (currentSegment->IsLinear()) { pA = ds; }	//DEBUG
#else
			int32_t shiftedK2 = (int32_t)(MoveSegment::Kdelta << shiftFactor);
			if (!direction)
			{
				shiftedK2 = -shiftedK2;
			}
			mp.delta.hmz0sK += shiftedK2;							// get K2 * (new carriage height above Z in steps)

			const int32_t hmz0scK = (int32_t)(((int64_t)mp.delta.hmz0sK * dda.afterPrepare.cKc) >> MoveSegment::SFdelta);
			const int32_t t1 = mp.delta.minusAaPlusBbTimesKs + hmz0scK;
			const int32_t t2a = (int32_t)(mp.delta.dSquaredMinusAsquaredMinusBsquaredTimesKsquaredSsquared - (int64_t)isquare64(mp.delta.hmz0sK) + (int64_t)isquare64(t1));
			// Due to rounding error we can end up trying to take the square root of a negative number if we do not take precautions here
			const uint32_t t2 = LimISqrt64(t2a);
			const int32_t dsK = (direction) ? t1 - t2 : t1 + t2;

			// Now feed dsK into the step algorithm for Cartesian motion
			if (dsK < 0)
			{
				state = DMState::stepError;
				nextStep += 110000000;							// so that we can tell what happened in the debug print
				return false;
			}

			const int32_t iCds = ((int64_t)iC * dsK) >> (MoveSegment::SFdelta + MoveSegment::SFdistance);
			iNextCalcStepTime = (currentSegment->IsLinear()) ? iB + iCds
								: (currentSegment->IsAccelerating()) ? iB + LimISqrt64(iA + iCds)
									 : iB - LimISqrt64(iA + iCds);
			//if (currentSegment->IsLinear()) { iA = dsK; }	//DEBUG
#endif
		}
		break;

	default:
		return false;
	}

#if 0	//DEBUG
	if (std::isnan(nextCalcStepTime) || nextCalcStepTime < 0.0)
	{
		state = DMState::stepError;
		nextStep += 140000000 + stepsTillRecalc;			// so we can tell what happened in the debug print
		distanceSoFar = nextCalcStepTime;					//DEBUG
		return false;
	}
#endif

#if MS_USE_FPU
	uint32_t iNextCalcStepTime = (uint32_t)nextCalcStepTime;
#endif

	if (iNextCalcStepTime > dda.clocksNeeded)
	{
		// The calculation makes this step late.
		// When the end speed is very low, calculating the time of the last step is very sensitive to rounding error.
		// So if this is the last step and it is late, bring it forward to the expected finish time.
		// Very rarely on a delta, the penultimate step may also be calculated late. Allow for that here in case it affects Cartesian axes too.
		if (nextStep + stepsTillRecalc + 1 >= totalSteps)
		{
			iNextCalcStepTime = dda.clocksNeeded;
		}
		else
		{
			// We don't expect any step except the last to be late
			state = DMState::stepError;
			nextStep += 120000000 + stepsTillRecalc;		// so we can tell what happened in the debug print
			stepInterval = iNextCalcStepTime;				//DEBUG
			return false;
		}
	}

	// When crossing between movement phases with high microstepping, due to rounding errors the next step may appear to be due before the last one
	stepInterval = (iNextCalcStepTime > nextStepTime)
					? (iNextCalcStepTime - nextStepTime) >> shiftFactor	// calculate the time per step, ready for next time
					: 0;

#if 0	//DEBUG
	if (isExtruder && stepInterval < 20 /*&& nextStep + stepsTillRecalc + 1 < totalSteps*/)
	{
		state = DMState::stepError;
		nextStep += 130000000 + stepsTillRecalc;			// so we can tell what happened in the debug print
		return false;
	}
#endif

#if EVEN_STEPS
	nextStepTime = iNextCalcStepTime - (stepsTillRecalc * stepInterval);
#else
	nextStepTime = iNextCalcStepTime;
#endif

	return true;
}

// End