reprapfirmware-dc42/Move.cpp

/****************************************************************************************************

RepRapFirmware - Move

This is all the code to deal with movement and kinematics.

-----------------------------------------------------------------------------------------------------

Version 0.1

18 November 2012

Adrian Bowyer
RepRap Professional Ltd
http://reprappro.com

Licence: GPL

****************************************************************************************************/

#include "RepRapFirmware.h"

Move::Move(Platform* p, GCodes* g)
{
  active = false;
  platform = p;
  gCodes = g;
  
  // Build the DDA ring
  
  ddaRingAddPointer = new DDA(this, platform, NULL);
  dda = ddaRingAddPointer;
  for(unsigned int i = 1; i < DDA_RING_LENGTH; i++)
  {
    dda = new DDA(this, platform, dda);
  }
  ddaRingAddPointer->next = dda;
  
  dda = NULL;
  
  // Build the lookahead ring
  
  lookAheadRingAddPointer = new LookAhead(this, platform, NULL);
  lookAheadRingGetPointer = lookAheadRingAddPointer;
  for(unsigned int i = 1; i < LOOK_AHEAD_RING_LENGTH; i++)
  {
    lookAheadRingGetPointer = new LookAhead(this, platform, lookAheadRingGetPointer);
  }
  lookAheadRingAddPointer->next = lookAheadRingGetPointer;
  
  // Set the lookahead backwards pointers (some oxymoron, surely?)
  
  lookAheadRingGetPointer = lookAheadRingAddPointer; 
  for(unsigned int i = 0; i <= LOOK_AHEAD_RING_LENGTH; i++)
  {
    lookAheadRingAddPointer = lookAheadRingAddPointer->Next();
    lookAheadRingAddPointer->previous = lookAheadRingGetPointer;
    lookAheadRingGetPointer = lookAheadRingAddPointer;
  }    
  
  lookAheadDDA = new DDA(this, platform, NULL);
  
}

void Move::Init()
{
  long ep[DRIVES];
  
  for(int8_t i = 0; i < DRIVES; i++)
  {
    platform->SetDirection(i, FORWARDS);
  }
  
  // Empty the rings
  
  ddaRingGetPointer = ddaRingAddPointer; 
  ddaRingLocked = false;
  
  for(unsigned int i = 0; i <= LOOK_AHEAD_RING_LENGTH; i++)
  {
    lookAheadRingAddPointer->Release();
    lookAheadRingAddPointer = lookAheadRingAddPointer->Next();
  }
  
  lookAheadRingGetPointer = lookAheadRingAddPointer;
  lookAheadRingCount = 0;
  
  addNoMoreMoves = false;

  // Put the origin on the lookahead ring with default velocity in the previous
  // position to the first one that will be used.
  
  lastMove = lookAheadRingAddPointer->Previous();
  
  for(unsigned int i = 0; i < DRIVES; i++)
  {
	  ep[i] = 0;
	  liveCoordinates[i] = 0.0;
  }

  int8_t slow = platform->SlowestDrive();
  lastMove->Init(ep, platform->HomeFeedRate(slow), platform->InstantDv(slow), platform->MaxFeedrate(slow), platform->Acceleration(slow), false);
  lastMove->Release();
  liveCoordinates[DRIVES] = platform->HomeFeedRate(slow);

  SetStepHypotenuse();

  currentFeedrate = -1.0;

  SetIdentityTransform();
  tanXY = 0.0;
  tanYZ = 0.0;
  tanXZ = 0.0;

  lastZHit = 0.0;
  zProbing = false;

  for(uint8_t point = 0; point < NUMBER_OF_PROBE_POINTS; point++)
  {
	  xBedProbePoints[point] = (0.3 + 0.6*(float)(point%2))*platform->AxisMaximum(X_AXIS);
	  yBedProbePoints[point] = (0.0 + 0.9*(float)(point/2))*platform->AxisMaximum(Y_AXIS);
	  zBedProbePoints[point] = 0.0;
	  probePointSet[point] = unset;
  }

  xRectangle = 1.0/(0.8*platform->AxisMaximum(X_AXIS));
  yRectangle = xRectangle;

  secondDegreeCompensation = false;

  lastTime = platform->Time();
  longWait = lastTime;
  active = true;  
}

void Move::Exit()
{
  platform->Message(HOST_MESSAGE, "Move class exited.\n");
  active = false;
}

void Move::Spin()
{
  if(!active)
    return;
    
  // Do some look-ahead work, if there's any to do
    
  DoLookAhead();
  
  // If there's space in the DDA ring, and there are completed
  // moves in the look-ahead ring, transfer them.
 
  if(!DDARingFull())
  {
     LookAhead* nextFromLookAhead = LookAheadRingGet();
     if(nextFromLookAhead != NULL)
     {
       if(!DDARingAdd(nextFromLookAhead))
         platform->Message(HOST_MESSAGE, "Can't add to non-full DDA ring!\n"); // Should never happen...
     }
  }
  
  // If we either don't want to, or can't, add to the look-ahead ring, go home.
  
  if(addNoMoreMoves || LookAheadRingFull())
  {
	  platform->ClassReport("Move", longWait);
	  return;
  }
 
  // If there's a G Code move available, add it to the look-ahead
  // ring for processing.

  uint8_t endStopsToCheckOnNextMove;
  if(gCodes->ReadMove(nextMove, endStopsToCheckOnNextMove))
  {
	Transform(nextMove);

    currentFeedrate = nextMove[DRIVES]; // Might be G1 with just an F field

    bool noMove = true;
    for(int8_t drive = 0; drive < DRIVES; drive++)
    {
    	nextMachineEndPoints[drive] = LookAhead::EndPointToMachine(drive, nextMove[drive]);
    	if(drive < AXES)
    	{
    		if(nextMachineEndPoints[drive] - lastMove->MachineCoordinates()[drive] != 0)
    		{
    		    noMove = false;
    		}
    		normalisedDirectionVector[drive] = nextMove[drive] - lastMove->MachineToEndPoint(drive);
    	} else
    	{
    		if(nextMachineEndPoints[drive] != 0)
    		{
    		    noMove = false;
    		}
    		normalisedDirectionVector[drive] = nextMove[drive];
    	}
    }

    // Throw it away if there's no real movement.
    
    if(noMove)
    {
       platform->ClassReport("Move", longWait);
       return;
    }
    
    // Compute the direction of motion, moved to the positive hyperquadrant

    Absolute(normalisedDirectionVector, DRIVES);
    if(Normalise(normalisedDirectionVector, DRIVES) <= 0.0)
    {
    	platform->Message(HOST_MESSAGE, "\nAttempt to normailse zero-length move.\n");  // Should never get here - noMove above
        platform->ClassReport("Move", longWait);
        return;
    }
    
    // Real move - record its feedrate with it, not here.

     currentFeedrate = -1.0;

     // Set the feedrate maximum and minimum, and the acceleration

     float minSpeed = VectorBoxIntersection(normalisedDirectionVector, platform->InstantDvs(), DRIVES);
     float acceleration = VectorBoxIntersection(normalisedDirectionVector, platform->Accelerations(), DRIVES);
     float maxSpeed = VectorBoxIntersection(normalisedDirectionVector, platform->MaxFeedrates(), DRIVES);

     if(!LookAheadRingAdd(nextMachineEndPoints, nextMove[DRIVES],minSpeed, maxSpeed, acceleration, endStopsToCheckOnNextMove))
     {
    	platform->Message(HOST_MESSAGE, "Can't add to non-full look ahead ring!\n"); // Should never happen...
     }
  }
  platform->ClassReport("Move", longWait);
}



/*
 * Take a unit positive-hyperquadrant vector, and return the factor needed to obtain
 * length of the vector as projected to touch box[].
 */

float Move::VectorBoxIntersection(const float v[], const float box[], int8_t dimensions)
{
	// Generate a vector length that is guaranteed to exceed the size of the box

	float biggerThanBoxDiagonal = 2.0*Magnitude(box, dimensions);
	float magnitude = biggerThanBoxDiagonal;
	for(int8_t d = 0; d < dimensions; d++)
	{
		if(biggerThanBoxDiagonal*v[d] > box[d])
		{
			float a = box[d]/v[d];
			if(a < magnitude)
			{
				magnitude = a;
			}
		}
	}
	return magnitude;
}

// Normalise a vector, and also return its previous magnitude
// If the vector is of 0 length, return a negative magnitude

float Move::Normalise(float v[], int8_t dimensions)
{
	float magnitude = Magnitude(v, dimensions);
	if(magnitude <= 0.0)
		return -1.0;
	Scale(v, 1.0/magnitude, dimensions);
	return magnitude;
}

// Return the magnitude of a vector

float Move::Magnitude(const float v[], int8_t dimensions)
{
	float magnitude = 0.0;
	for(int8_t d = 0; d < dimensions; d++)
	{
		magnitude += v[d]*v[d];
	}
	magnitude = sqrt(magnitude);
	return magnitude;
}

// Multiply a vector by a scalar

void Move::Scale(float v[], float scale, int8_t dimensions)
{
	for(int8_t d = 0; d < dimensions; d++)
	{
		v[d] = scale*v[d];
	}
}

// Move a vector into the positive hyperquadrant

void Move::Absolute(float v[], int8_t dimensions)
{
	for(int8_t d = 0; d < dimensions; d++)
	{
		v[d] = fabs(v[d]);
	}
}

// These are the actual numbers we want in the positions, so don't transform them.

void Move::SetPositions(float move[])
{
	for(uint8_t drive = 0; drive < DRIVES; drive++)
	{
		lastMove->SetDriveCoordinateAndZeroEndSpeed(move[drive], drive);
	}
	lastMove->SetFeedRate(move[DRIVES]);
}

void Move::SetFeedrate(float feedRate)
{
	lastMove->SetFeedRate(feedRate);
}


void Move::Diagnostics() 
{
  platform->AppendMessage(BOTH_MESSAGE, "Move Diagnostics:\n");

/*  if(active)
    platform->Message(HOST_MESSAGE, " active\n");
  else
    platform->Message(HOST_MESSAGE, " not active\n");
  
  platform->Message(HOST_MESSAGE, " look ahead ring count: ");
  snprintf(scratchString, STRING_LENGTH, "%d\n", lookAheadRingCount);
  platform->Message(HOST_MESSAGE, scratchString);
  if(dda == NULL)
    platform->Message(HOST_MESSAGE, " dda: NULL\n");
  else
  {
    if(dda->Active())
      platform->Message(HOST_MESSAGE, " dda: active\n");
    else
      platform->Message(HOST_MESSAGE, " dda: not active\n");
    
  }
  if(ddaRingLocked)
    platform->Message(HOST_MESSAGE, " dda ring is locked\n");
  else
    platform->Message(HOST_MESSAGE, " dda ring is not locked\n");
  if(addNoMoreMoves)
    platform->Message(HOST_MESSAGE, " addNoMoreMoves is true\n\n");
  else
    platform->Message(HOST_MESSAGE, " addNoMoreMoves is false\n\n"); 
    */
}

// Return the untransformed machine coordinates
// This returns false if it is not possible
// to use the result as the basis for the
// next move because the look ahead ring
// is full.  True otherwise.

bool Move::GetCurrentMachinePosition(float m[])
{
  if(LookAheadRingFull())
    return false;
    
  for(int8_t i = 0; i < DRIVES; i++)
  {
    if(i < AXES)
    {
      m[i] = lastMove->MachineToEndPoint(i);
    }
    else
    {
      m[i] = 0.0; //FIXME This resets extruders to 0.0, even the inactive ones (is this behaviour desired?)
      //m[i] = lastMove->MachineToEndPoint(i); //FIXME TEST alternative that does not reset extruders to 0
    }
  }
  if(currentFeedrate >= 0.0)
  {
    m[DRIVES] = currentFeedrate;
  }
  else
  {
    m[DRIVES] = lastMove->FeedRate();
  }
  currentFeedrate = -1.0;
  return true;
}

// Return the transformed machine coordinates

bool Move::GetCurrentUserPosition(float m[])
{
	if(!GetCurrentMachinePosition(m))
		return false;
	InverseTransform(m);
	return true;
}


void Move::SetStepHypotenuse()
{
	  // The stepDistances array is a look-up table of the Euclidean distance
	  // between the start and end of a step.  If the step is just along one axis,
	  // it's just that axis's step length.  If it's more, it is a Pythagoran
	  // sum of all the axis steps that take part.

	  for(unsigned int i = 0; i < (1<<DRIVES); i++)
	  {
	    float d = 0.0;
	    for(unsigned int j = 0; j < DRIVES; j++)
	    {
	       if(i & (1<<j))
	       {
	          float e = 1.0/platform->DriveStepsPerUnit(j);
	          d += e*e;
	       }
	    }
	    stepDistances[i] = sqrt(d);
	  }

	  // We don't want 0.  If no axes/extruders are moving these should never be used.
	  // But try to be safe.

	  stepDistances[0] = 1.0/platform->DriveStepsPerUnit(AXES); //FIXME this is not multi extruder safe (but we should never get here)
}

/*
 * For diagnostics
 */

void Move::PrintMove(LookAhead* lookAhead)
{
	snprintf(scratchString, STRING_LENGTH, "X,Y,Z: %.1f %.1f %.1f, min v: %.2f, max v: %.1f, acc: %.1f, feed: %.1f, v: %.3f\n",
			lookAhead->MachineToEndPoint(X_AXIS), lookAhead->MachineToEndPoint(Y_AXIS), lookAhead->MachineToEndPoint(Z_AXIS),
			lookAhead->MinSpeed(), lookAhead->MaxSpeed(), lookAhead->Acceleration(), lookAhead->FeedRate(), lookAhead->V()
	);
	platform->Message(HOST_MESSAGE, scratchString);
}

// Take an item from the look-ahead ring and add it to the DDA ring, if
// possible.

bool Move::DDARingAdd(LookAhead* lookAhead)
{
  if(GetDDARingLock())
  {
    if(DDARingFull())
    {
      ReleaseDDARingLock();
      return false;
    }
    if(ddaRingAddPointer->Active())  // Should never happen...
    {
      platform->Message(HOST_MESSAGE, "Attempt to alter an active ring buffer entry!\n");
      ReleaseDDARingLock();
      return false;
    }

    // We don't care about Init()'s return value - that should all have been sorted out by LookAhead.
    
    float u, v;
    ddaRingAddPointer->Init(lookAhead, u, v);
    //PrintMove(lookAhead);
    ddaRingAddPointer = ddaRingAddPointer->Next();
    ReleaseDDARingLock();
    return true;
  }
  return false;
}

// Get a movement from the DDA ring, if we can.

DDA* Move::DDARingGet()
{
  DDA* result = NULL;
  if(GetDDARingLock())
  {
    if(DDARingEmpty())
    {
      ReleaseDDARingLock();
      return NULL;
    }
    result = ddaRingGetPointer;
    ddaRingGetPointer = ddaRingGetPointer->Next();
    ReleaseDDARingLock();
    return result;
  }
  return NULL;
}

// Do the look-ahead calculations

void Move::DoLookAhead()
{
  if(LookAheadRingEmpty())
    return;
  
  LookAhead* n0;
  LookAhead* n1;
  LookAhead* n2;
  
  // If there are a reasonable number of moves in there (LOOK_AHEAD), or if we are
  // doing single moves with no other move immediately following on, run up and down
  // the moves using the DDA Init() function to reduce the start or the end speed
  // or both to the maximum that can be achieved because of the requirements of
  // the adjacent moves. 
    
  if(addNoMoreMoves || !gCodes->HaveIncomingData() || lookAheadRingCount > LOOK_AHEAD)
  { 
    
    // Run up the moves
    
    n1 = lookAheadRingGetPointer;
    n0 = n1->Previous();
    n2 = n1->Next();
    while(n2 != lookAheadRingAddPointer)
    {
      if(!(n1->Processed() & complete))
      {
        if(n1->Processed() & vCosineSet)
        {
          float u = n0->V();
          float v = n1->V();
          if(lookAheadDDA->Init(n1, u, v) & change)
          {
            n0->SetV(u);
            n1->SetV(v); 
          }
        }
      }
      n0 = n1;
      n1 = n2;
      n2 = n2->Next();
    }
    
    // Now run down
    
    do
    { 
      if(!(n1->Processed() & complete))
      {
        if(n1->Processed() & vCosineSet)
        {
          float u = n0->V();
          float v = n1->V();
          if(lookAheadDDA->Init(n1, u, v) & change)
          {
            n0->SetV(u);
            n1->SetV(v); 
          }
          n1->SetProcessed(complete);
        }
      }
      n2 = n1;
      n1 = n0;
      n0 = n0->Previous();      
    } while(n0 != lookAheadRingGetPointer);
    n0->SetProcessed(complete);
  }

  // If there are any new unprocessed moves in there, set their end speeds
  // according to the cosine of the angle between them.
  
  if(addNoMoreMoves || !gCodes->HaveIncomingData() || lookAheadRingCount > 1)
  {
    n1 = lookAheadRingGetPointer;
    n0 = n1->Previous();
    n2 = n1->Next();
    while(n2 != lookAheadRingAddPointer)
    {
      if(n1->Processed() == unprocessed)
      {
        //float c = fmin(n1->FeedRate(), n2->FeedRate());
    	float c = n1->V();
        float m = fmin(n1->MinSpeed(), n2->MinSpeed());  // FIXME we use min as one move's max may not be able to cope with the min for the other.  But should this be max?
        c = c*n1->Cosine();
        if(c < m)
        {
        	c = m;
        }
        n1->SetV(c);
        n1->SetProcessed(vCosineSet);
      } 
      n0 = n1;
      n1 = n2;
      n2 = n2->Next();
    }

    // If we are just doing one isolated move, set its end velocity to an appropriate minimum speed.

    if(addNoMoreMoves || !gCodes->HaveIncomingData())
    {
    	n1->SetV(platform->InstantDv(platform->SlowestDrive())); // The next thing may be the slowest; be prepared.
    	n1->SetProcessed(complete);
    }
  }
}

// This is the function that's called by the timer interrupt to step the motors.

void Move::Interrupt()
{
  // Have we got a live DDA?
  
  if(dda == NULL)
  {
    // No - see if a new one is available.
    
    dda = DDARingGet();    
    if(dda != NULL)
    {
      dda->Start();  // Yes - got it.  So fire it up.
    }
    return;   
  }
  
  // We have a DDA.  Has it finished?
  
  if(dda->Active())
  {
    // No - it's still live.  Step it and return.
    
    dda->Step();
    return;
  }
  
  // Yes - it's finished.  Throw it away so the code above will then find a new one.
  
  dda = NULL;
}

// Records a new lookahead object and adds it to the lookahead ring, returns false if it's full

bool Move::LookAheadRingAdd(long ep[], float requestedFeedRate, float minSpeed, float maxSpeed, float acceleration, uint8_t ce)
{
    if(LookAheadRingFull())
      return false;
    if(!(lookAheadRingAddPointer->Processed() & released)) // Should never happen...
    {
      platform->Message(HOST_MESSAGE, "Attempt to alter a non-released lookahead ring entry!\n");
      return false;
    }
    lookAheadRingAddPointer->Init(ep, requestedFeedRate, minSpeed, maxSpeed, acceleration, ce);
    lastMove = lookAheadRingAddPointer;
    lookAheadRingAddPointer = lookAheadRingAddPointer->Next();
    lookAheadRingCount++;
    return true;
}


LookAhead* Move::LookAheadRingGet()
{
  LookAhead* result;
  if(LookAheadRingEmpty())
    return NULL;
  result = lookAheadRingGetPointer;
  if(!(result->Processed() & complete))
    return NULL;
  lookAheadRingGetPointer = lookAheadRingGetPointer->Next();
  lookAheadRingCount--;
  return result;
}

// Note that we don't set the tan values to 0 here.  This means that the bed probe
// values will be a fraction of a millimetre out in X and Y, which, as the bed should
// be nearly flat (and the probe doesn't coincide with the nozzle anyway), won't matter.
// But it means that the tan values can be set for the machine
// at the start in the configuration file and be retained, without having to know and reset
// them after every Z probe of the bed.

void Move::SetIdentityTransform()
{
	aX = 0.0;
	aY = 0.0;
	aC = 0.0;
	secondDegreeCompensation = false;
}

// Do the bed transform AFTER the axis transform

void Move::BedTransform(float xyzPoint[]) const
{
	if(secondDegreeCompensation)
	{
		xyzPoint[Z_AXIS] = xyzPoint[Z_AXIS] + SecondDegreeTransformZ(xyzPoint[X_AXIS], xyzPoint[Y_AXIS]);
	}
	else
	{
		xyzPoint[Z_AXIS] = xyzPoint[Z_AXIS] + aX*xyzPoint[X_AXIS] + aY*xyzPoint[Y_AXIS] + aC;
	}
}

// Invert the bed transform BEFORE the axis transform

void Move::InverseBedTransform(float xyzPoint[]) const
{
	if(secondDegreeCompensation)
	{
		xyzPoint[Z_AXIS] = xyzPoint[Z_AXIS] - SecondDegreeTransformZ(xyzPoint[X_AXIS], xyzPoint[Y_AXIS]);
	}
	else
	{
		xyzPoint[Z_AXIS] = xyzPoint[Z_AXIS] - (aX*xyzPoint[X_AXIS] + aY*xyzPoint[Y_AXIS] + aC);
	}
}

// Do the Axis transform BEFORE the bed transform

void Move::AxisTransform(float xyzPoint[]) const
{
	xyzPoint[X_AXIS] = xyzPoint[X_AXIS] + tanXY*xyzPoint[Y_AXIS] + tanXZ*xyzPoint[Z_AXIS];
	xyzPoint[Y_AXIS] = xyzPoint[Y_AXIS] + tanYZ*xyzPoint[Z_AXIS];
}

// Invert the Axis transform AFTER the bed transform

void Move::InverseAxisTransform(float xyzPoint[]) const
{
	xyzPoint[Y_AXIS] = xyzPoint[Y_AXIS] - tanYZ*xyzPoint[Z_AXIS];
	xyzPoint[X_AXIS] = xyzPoint[X_AXIS] - (tanXY*xyzPoint[Y_AXIS] + tanXZ*xyzPoint[Z_AXIS]);
}


void Move::Transform(float xyzPoint[]) const
{
	AxisTransform(xyzPoint);
	BedTransform(xyzPoint);
}

void Move::InverseTransform(float xyzPoint[]) const
{
	InverseBedTransform(xyzPoint);
	InverseAxisTransform(xyzPoint);
}


void Move::SetAxisCompensation(int8_t axis, float tangent)
{
	switch(axis)
	{
	case X_AXIS:
		tanXY = tangent;
		break;
	case Y_AXIS:
		tanYZ = tangent;
		break;
	case Z_AXIS:
		tanXZ = tangent;
		break;
	default:
		platform->Message(HOST_MESSAGE, "SetAxisCompensation: dud axis.\n");
	}
}

void Move::SetProbedBedEquation()
{
	switch(NumberOfProbePoints())
	{
	case 3:
		/*
		 * Transform to a plane
		 */
		secondDegreeCompensation = false;
		float xkj, ykj, zkj;
		float xlj, ylj, zlj;
		float a, b, c, d;   // Implicit plane equation - what we need to do a proper job

		xkj = xBedProbePoints[1] - xBedProbePoints[0];
		ykj = yBedProbePoints[1] - yBedProbePoints[0];
		zkj = zBedProbePoints[1] - zBedProbePoints[0];
		xlj = xBedProbePoints[2] - xBedProbePoints[0];
		ylj = yBedProbePoints[2] - yBedProbePoints[0];
		zlj = zBedProbePoints[2] - zBedProbePoints[0];
		a = ykj*zlj - zkj*ylj;
		b = zkj*xlj - xkj*zlj;
		c = xkj*ylj - ykj*xlj;
		d = -(xBedProbePoints[1]*a + yBedProbePoints[1]*b + zBedProbePoints[1]*c);
		aX = -a/c;
		aY = -b/c;
		aC = -d/c;
		break;

	case 4:
		/*
		 * Transform to a ruled-surface quadratic.  The corner points for interpolation are indexed:
		 *
		 *   ^  [1]      [2]
		 *   |
		 *   Y
		 *   |
		 *   |  [0]      [3]
		 *      -----X---->
		 *
		 *   These are the scaling factors to apply to x and y coordinates to get them into the
		 *   unit interval [0, 1].
		 */
		secondDegreeCompensation = true;
		xRectangle = 1.0/(xBedProbePoints[3] - xBedProbePoints[0]);
		yRectangle = 1.0/(yBedProbePoints[1] - yBedProbePoints[0]);
		break;

	default:
		platform->Message(HOST_MESSAGE, "Attempt to set bed compensation before all probe points have been recorded.");
	}
}

// FIXME
// This function is never normally called.  It is a test to time
// the interrupt function.  To activate it, uncomment the line that calls
// this in Platform.ino.

void Move::InterruptTime()
{
/*  char buffer[50];
  float a[] = {1.0, 2.0, 3.0, 4.0, 5.0};
  float b[] = {2.0, 3.0, 4.0, 5.0, 6.0};
  float u = 50;
  float v = 50;
  lookAheadDDA->Init(a, b, u, v);
  lookAheadDDA->Start(false);
  float t = platform->Time();
  for(long i = 0; i < 100000; i++) 
    lookAheadDDA->Step(false);
  t = platform->Time() - t;
  platform->Message(HOST_MESSAGE, "Time for 100000 calls of the interrupt function: ");
  snprintf(buffer, 50, "%ld", t);
  platform->Message(HOST_MESSAGE, buffer);
  platform->Message(HOST_MESSAGE, " microseconds.\n");*/
}

//****************************************************************************************************

DDA::DDA(Move* m, Platform* p, DDA* n)
{
  active = false;
  move = m;
  platform = p;
  next = n;
}

/*

DDA::Init(...) 

Sets up the DDA to take us between two positions and extrude states.
The start velocity is u, and the end one is v.  The requested maximum feedrate
is in myLookAheadEntry->FeedRate().

Almost everything that needs to be done to set this up is also useful
for GCode look-ahead, so this one function is used for both.  It flags when
u and v cannot be satisfied with the distance available and reduces them 
proportionately to give values that can just be achieved, which is why they
are passed by reference.

The return value is indicates if the move is a trapezium or triangle, and if
the u and u values need to be changed.

In the case of only extruders moving, the distance moved is taken to be the Pythagoran distance in
the configuration space of the extruders.

TODO: Worry about having more than eight extruders

*/

MovementProfile DDA::AccelerationCalculation(float& u, float& v, MovementProfile result)
{
	// At which DDA step should we stop accelerating?  myLookAheadEntry->FeedRate() gives
	// the desired feedrate.

	feedRate = myLookAheadEntry->FeedRate();

	float d = 0.5*(feedRate*feedRate - u*u)/acceleration; // d = (v1^2 - v0^2)/2a
	stopAStep = (long)roundf((d*totalSteps)/distance);

	// At which DDA step should we start decelerating?

	d = 0.5*(v*v - feedRate*feedRate)/acceleration;  // This should be 0 or negative...
	startDStep = totalSteps + (long)roundf((d*totalSteps)/distance);

	// If acceleration stop is at or after deceleration start, then the distance moved
	// is not enough to get to full speed.

	if(stopAStep >= startDStep)
	{
		result = noFlat;

		// Work out the point at which to stop accelerating and then
		// immediately start decelerating.

		float dCross = 0.5*(0.5*(v*v - u*u)/acceleration + distance);

		// dc42's better version

		if(dCross < 0.0 || dCross > distance)
		{
			// With the acceleration available, it is not possible
			// to satisfy u and v within the distance; reduce the greater of u and v
			// to get ones that work and flag the fact.
			// The result is two velocities that can just be accelerated
			// or decelerated between over the distance to get
			// from one to the other.

			result = change;
			float temp = 2.0 * acceleration * distance;
			if (v > u)
			{
				// Accelerating, reduce v
				v = sqrt((u * u) + temp);
				dCross = distance;
			}
			else
			{
				// Decelerating, reduce u
				u = sqrt((v * v) + temp);
				dCross = 0.0;
			}
		}

		// The DDA steps at which acceleration stops and deceleration starts

		stopAStep = (long)((dCross*totalSteps)/distance);
		startDStep = stopAStep + 1;
	}

	return result;
}


MovementProfile DDA::Init(LookAhead* lookAhead, float& u, float& v)
{
  active = false;
  myLookAheadEntry = lookAhead;
  MovementProfile result = moving;
  totalSteps = -1;
  distance = 0.0;
  const long* targetPosition = myLookAheadEntry->MachineCoordinates();
  v = myLookAheadEntry->V();
  const long* positionNow = myLookAheadEntry->Previous()->MachineCoordinates();
  u = myLookAheadEntry->Previous()->V();
  endStopsToCheck = myLookAheadEntry->EndStopsToCheck();
  int8_t bigDirection = 0;

  // How far are we going, both in steps and in mm?
  
  for(unsigned int drive = 0; drive < DRIVES; drive++)
  {
    if(drive < AXES) // X, Y, & Z
    {
      delta[drive] = targetPosition[drive] - positionNow[drive];  // XYZ Absolute
    }
    else
    {
      delta[drive] = targetPosition[drive];  // Es Relative
    }

    float d = myLookAheadEntry->MachineToEndPoint(drive, delta[drive]);
    distance += d*d;
    
    if(delta[drive] >= 0)
    {
      directions[drive] = FORWARDS;
    }
    else
    {
      directions[drive] = BACKWARDS;
      delta[drive] = -delta[drive];
    }
    
    // Keep track of the biggest drive move in totalSteps
    
    if(delta[drive] > totalSteps)
    {
      totalSteps = delta[drive];
      bigDirection = drive;
    }
  }
  
  // Not going anywhere?  Should have been chucked away before we got here.
  
  if(totalSteps <= 0)
  {
	if(reprap.Debug())
	{
		platform->Message(HOST_MESSAGE, "DDA.Init(): Null movement.\n");
	}
    myLookAheadEntry->Release();
    return result;
  }
  
  // Set up the DDA
  
  counter[0] = -totalSteps/2;
  for(unsigned int drive = 1; drive < DRIVES; drive++)
  {
    counter[drive] = counter[0];
  }
  
  // Acceleration and velocity calculations
  
  distance = sqrt(distance);
  
  // Decide the appropriate acceleration and instantDv values
  // timeStep is set here to the distance of the
  // biggest-move axis step.  It will be divided
  // by a velocity later.

  acceleration = lookAhead->Acceleration();
  instantDv = lookAhead->MinSpeed();
  timeStep = 1.0/platform->DriveStepsPerUnit(bigDirection);

  result = AccelerationCalculation(u, v, result);
  
  // The initial velocity
  
  velocity = u;
  
// Sanity check
  
  if(velocity <= 0.0)
  {
    velocity = instantDv;
    if(reprap.Debug())
    {
    	platform->Message(HOST_MESSAGE, "DDA.Init(): Zero or negative initial velocity!\n");
    }
  }
  
  // How far have we gone?
  
  stepCount = 0;
  
  // timeStep is an axis step distance at this point; divide it by the
  // velocity to get time.
  
  timeStep = timeStep/velocity;
  
  return result;
}

void DDA::Start()
{
  for(int8_t drive = 0; drive < DRIVES; drive++)
    platform->SetDirection(drive, directions[drive]);

  platform->SetInterrupt(timeStep); // seconds
  active = true;  
}

void DDA::Step()
{
  if(!active)
    return;
  
  if(!move->active)
	  return;

  int drivesMoving = 0;
//  uint8_t extrudersMoving = 0;
  
  for(size_t drive = 0; drive < DRIVES; drive++)
  {
    counter[drive] += delta[drive];
    if(counter[drive] > 0)
    {
      platform->Step(drive);

      counter[drive] -= totalSteps;
      
//      if(drive < AXES)
        drivesMoving |= 1<<drive;
//      else
//        extrudersMoving |= 1<<(drive - AXES);
        
      // Hit anything?
  
      if((endStopsToCheck & (1 << drive)) != 0)
      {
        switch(platform->Stopped(drive))
        {
        case lowHit:
          move->HitLowStop(drive, myLookAheadEntry, this);
          active = false;
          break;
        case highHit:
          move->HitHighStop(drive, myLookAheadEntry, this);
          active = false;
          break;
        case lowNear:
          velocity = instantDv;		// slow down because we are getting close
          break;
        default:
          break;
        }
      }        
    }
  }
  
  // May have hit a stop, so test active here
  
  if(active)
  {
 //   if(drivesMoving)
      timeStep = move->stepDistances[drivesMoving]/velocity;
 //   else
 //     timeStep = move->extruderStepDistances[extrudersMoving]/velocity;
      
    // Simple Euler integration to get velocities.
    // Maybe one day do a Runge-Kutta?
  
    if(stepCount < stopAStep)
    {
      velocity += acceleration*timeStep;
      if (velocity > feedRate)
      {
    	  velocity = feedRate;
      }
    }
    else if(stepCount >= startDStep)
    {
      velocity -= acceleration*timeStep;
      if(velocity < instantDv)
      {
    	  velocity = instantDv;
      }
    }
      
    stepCount++;
    active = stepCount < totalSteps;
    
    platform->SetInterrupt(timeStep);
  }
  
  if(!active)
  {
	for(int8_t drive = 0; drive < DRIVES; drive++)
	{
		move->liveCoordinates[drive] = myLookAheadEntry->MachineToEndPoint(drive); // Don't use SetLiveCoordinates because that applies the transform
	}
	move->liveCoordinates[DRIVES] = myLookAheadEntry->FeedRate();
    myLookAheadEntry->Release();
    platform->SetInterrupt(STANDBY_INTERRUPT_RATE);
  }
}

//***************************************************************************************************

LookAhead::LookAhead(Move* m, Platform* p, LookAhead* n)
{
  move = m;
  platform = p;
  next = n;
}

void LookAhead::Init(long ep[], float fRate, float minS, float maxS, float acc, uint8_t ce)
{
  v = fRate;
  requestedFeedrate = fRate;
  minSpeed = minS;
  maxSpeed = maxS;
  acceleration = acc;

  if(v < minSpeed)
  {
	  requestedFeedrate = minSpeed;
	  v = minSpeed;
  }
  if(v > maxSpeed)
  {
	  requestedFeedrate = maxSpeed;
	  v = maxSpeed;
  }

  for(int8_t i = 0; i < DRIVES; i++)
  {
    endPoint[i] = ep[i];
  }
  
  endStopsToCheck = ce;
  
  // Cosines are lazily evaluated; flag this as unevaluated
  
  cosine = 2.0;
    
  // Only bother with lookahead when we are printing a file, so set processed complete when we aren't.
  
  processed = (reprap.GetGCodes()->HaveIncomingData())
    			? unprocessed
  	  	  	  	  : complete|vCosineSet|upPass;
}


// This returns the cosine of the angle between
// the movement up to this, and the movement
// away from this.  Note that it
// includes Z movements, though Z values will almost always 
// not change.  Uses lazy evaluation.

float LookAhead::Cosine()
{
  if(cosine < 1.5)
    return cosine;
    
  cosine = 0.0;
  float a2 = 0.0;
  float b2 = 0.0;
  float m1;
  float m2;
  for(int8_t i = 0; i < AXES; i++)
  {
	m1 = MachineToEndPoint(i);
    m2 = Next()->MachineToEndPoint(i) - m1;
    m1 = m1 - Previous()->MachineToEndPoint(i);
    a2 += m1*m1;
    b2 += m2*m2;
    cosine += m1*m2;
  }
  
  if(a2 <= 0.0 || b2 <= 0.0)
  {
	cosine = 0.0;		// one of the moves is just an extruder move (probably a retraction), so orthogonal (in 4D space!) to XYZ moves
    return cosine;
  }
 
  cosine = cosine/( (float)sqrt(a2) * (float)sqrt(b2) );
  return cosine;
}

//Returns units (mm) from steps for a particular drive
float LookAhead::MachineToEndPoint(int8_t drive, long coord)
{
	return ((float)coord)/reprap.GetPlatform()->DriveStepsPerUnit(drive);
}

//Returns steps from units (mm) for a particular drive
long LookAhead::EndPointToMachine(int8_t drive, float coord)
{
	return  (long)roundf(coord*reprap.GetPlatform()->DriveStepsPerUnit(drive));
}