marlin-lulzbot-laser/Marlin/planner.cpp

/**
 * Marlin 3D Printer Firmware
 * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
 *
 * Based on Sprinter and grbl.
 * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

/**
 * planner.cpp
 *
 * Buffer movement commands and manage the acceleration profile plan
 *
 * Derived from Grbl
 * Copyright (c) 2009-2011 Simen Svale Skogsrud
 *
 * The ring buffer implementation gleaned from the wiring_serial library by David A. Mellis.
 *
 *
 * Reasoning behind the mathematics in this module (in the key of 'Mathematica'):
 *
 * s == speed, a == acceleration, t == time, d == distance
 *
 * Basic definitions:
 *   Speed[s_, a_, t_] := s + (a*t)
 *   Travel[s_, a_, t_] := Integrate[Speed[s, a, t], t]
 *
 * Distance to reach a specific speed with a constant acceleration:
 *   Solve[{Speed[s, a, t] == m, Travel[s, a, t] == d}, d, t]
 *   d -> (m^2 - s^2)/(2 a) --> estimate_acceleration_distance()
 *
 * Speed after a given distance of travel with constant acceleration:
 *   Solve[{Speed[s, a, t] == m, Travel[s, a, t] == d}, m, t]
 *   m -> Sqrt[2 a d + s^2]
 *
 * DestinationSpeed[s_, a_, d_] := Sqrt[2 a d + s^2]
 *
 * When to start braking (di) to reach a specified destination speed (s2) after accelerating
 * from initial speed s1 without ever stopping at a plateau:
 *   Solve[{DestinationSpeed[s1, a, di] == DestinationSpeed[s2, a, d - di]}, di]
 *   di -> (2 a d - s1^2 + s2^2)/(4 a) --> intersection_distance()
 *
 * IntersectionDistance[s1_, s2_, a_, d_] := (2 a d - s1^2 + s2^2)/(4 a)
 *
 */

#include "planner.h"
#include "stepper.h"
#include "temperature.h"
#include "ultralcd.h"
#include "language.h"

#include "Marlin.h"

#if ENABLED(MESH_BED_LEVELING)
  #include "mesh_bed_leveling.h"
#endif

Planner planner;

  // public:

/**
 * A ring buffer of moves described in steps
 */
block_t Planner::block_buffer[BLOCK_BUFFER_SIZE];
volatile uint8_t Planner::block_buffer_head = 0;           // Index of the next block to be pushed
volatile uint8_t Planner::block_buffer_tail = 0;

float Planner::max_feedrate_mm_s[NUM_AXIS], // Max speeds in mm per second
      Planner::axis_steps_per_mm[NUM_AXIS],
      Planner::steps_to_mm[NUM_AXIS];

unsigned long Planner::max_acceleration_steps_per_s2[NUM_AXIS],
              Planner::max_acceleration_mm_per_s2[NUM_AXIS]; // Use M201 to override by software

millis_t Planner::min_segment_time;
float Planner::min_feedrate_mm_s,
      Planner::acceleration,         // Normal acceleration mm/s^2  DEFAULT ACCELERATION for all printing moves. M204 SXXXX
      Planner::retract_acceleration, // Retract acceleration mm/s^2 filament pull-back and push-forward while standing still in the other axes M204 TXXXX
      Planner::travel_acceleration,  // Travel acceleration mm/s^2  DEFAULT ACCELERATION for all NON printing moves. M204 MXXXX
      Planner::max_jerk[XYZE],       // The largest speed change requiring no acceleration
      Planner::min_travel_feedrate_mm_s;

#if HAS_ABL
  bool Planner::abl_enabled = false; // Flag that auto bed leveling is enabled
#endif

#if ABL_PLANAR
  matrix_3x3 Planner::bed_level_matrix; // Transform to compensate for bed level
#endif

#if ENABLED(AUTOTEMP)
  float Planner::autotemp_max = 250,
        Planner::autotemp_min = 210,
        Planner::autotemp_factor = 0.1;
  bool Planner::autotemp_enabled = false;
#endif

// private:

long Planner::position[NUM_AXIS] = { 0 };

float Planner::previous_speed[NUM_AXIS],
      Planner::previous_nominal_speed;

#if ENABLED(DISABLE_INACTIVE_EXTRUDER)
  uint8_t Planner::g_uc_extruder_last_move[EXTRUDERS] = { 0 };
#endif // DISABLE_INACTIVE_EXTRUDER

#ifdef XY_FREQUENCY_LIMIT
  // Old direction bits. Used for speed calculations
  unsigned char Planner::old_direction_bits = 0;
  // Segment times (in µs). Used for speed calculations
  long Planner::axis_segment_time[2][3] = { {MAX_FREQ_TIME + 1, 0, 0}, {MAX_FREQ_TIME + 1, 0, 0} };
#endif

/**
 * Class and Instance Methods
 */

Planner::Planner() { init(); }

void Planner::init() {
  block_buffer_head = block_buffer_tail = 0;
  memset(position, 0, sizeof(position));
  memset(previous_speed, 0, sizeof(previous_speed));
  previous_nominal_speed = 0.0;
  #if ABL_PLANAR
    bed_level_matrix.set_to_identity();
  #endif
}

/**
 * Calculate trapezoid parameters, multiplying the entry- and exit-speeds
 * by the provided factors.
 */
void Planner::calculate_trapezoid_for_block(block_t* const block, const float &entry_factor, const float &exit_factor) {
  uint32_t initial_rate = ceil(block->nominal_rate * entry_factor),
           final_rate = ceil(block->nominal_rate * exit_factor); // (steps per second)

  // Limit minimal step rate (Otherwise the timer will overflow.)
  NOLESS(initial_rate, 120);
  NOLESS(final_rate, 120);

  int32_t accel = block->acceleration_steps_per_s2,
          accelerate_steps = ceil(estimate_acceleration_distance(initial_rate, block->nominal_rate, accel)),
          decelerate_steps = floor(estimate_acceleration_distance(block->nominal_rate, final_rate, -accel)),
          plateau_steps = block->step_event_count - accelerate_steps - decelerate_steps;

  // Is the Plateau of Nominal Rate smaller than nothing? That means no cruising, and we will
  // have to use intersection_distance() to calculate when to abort accel and start braking
  // in order to reach the final_rate exactly at the end of this block.
  if (plateau_steps < 0) {
    accelerate_steps = ceil(intersection_distance(initial_rate, final_rate, accel, block->step_event_count));
    NOLESS(accelerate_steps, 0); // Check limits due to numerical round-off
    accelerate_steps = min((uint32_t)accelerate_steps, block->step_event_count);//(We can cast here to unsigned, because the above line ensures that we are above zero)
    plateau_steps = 0;
  }

  #if ENABLED(ADVANCE)
    volatile int32_t initial_advance = block->advance * sq(entry_factor),
                       final_advance = block->advance * sq(exit_factor);
  #endif // ADVANCE

  // block->accelerate_until = accelerate_steps;
  // block->decelerate_after = accelerate_steps+plateau_steps;
  CRITICAL_SECTION_START;  // Fill variables used by the stepper in a critical section
  if (!block->busy) { // Don't update variables if block is busy.
    block->accelerate_until = accelerate_steps;
    block->decelerate_after = accelerate_steps + plateau_steps;
    block->initial_rate = initial_rate;
    block->final_rate = final_rate;
    #if ENABLED(ADVANCE)
      block->initial_advance = initial_advance;
      block->final_advance = final_advance;
    #endif
  }
  CRITICAL_SECTION_END;
}

// "Junction jerk" in this context is the immediate change in speed at the junction of two blocks.
// This method will calculate the junction jerk as the euclidean distance between the nominal
// velocities of the respective blocks.
//inline float junction_jerk(block_t *before, block_t *after) {
//  return sqrt(
//    pow((before->speed_x-after->speed_x), 2)+pow((before->speed_y-after->speed_y), 2));
//}


// The kernel called by recalculate() when scanning the plan from last to first entry.
void Planner::reverse_pass_kernel(block_t* const current, const block_t *next) {
  if (!current || !next) return;
  // If entry speed is already at the maximum entry speed, no need to recheck. Block is cruising.
  // If not, block in state of acceleration or deceleration. Reset entry speed to maximum and
  // check for maximum allowable speed reductions to ensure maximum possible planned speed.
  float max_entry_speed = current->max_entry_speed;
  if (current->entry_speed != max_entry_speed) {
    // If nominal length true, max junction speed is guaranteed to be reached. Only compute
    // for max allowable speed if block is decelerating and nominal length is false.
    current->entry_speed = ((current->flag & BLOCK_FLAG_NOMINAL_LENGTH) || max_entry_speed <= next->entry_speed)
      ? max_entry_speed
      : min(max_entry_speed, max_allowable_speed(-current->acceleration, next->entry_speed, current->millimeters));
    current->flag |= BLOCK_FLAG_RECALCULATE;
  }
}

/**
 * recalculate() needs to go over the current plan twice.
 * Once in reverse and once forward. This implements the reverse pass.
 */
void Planner::reverse_pass() {

  if (movesplanned() > 3) {

    block_t* block[3] = { NULL, NULL, NULL };

    // Make a local copy of block_buffer_tail, because the interrupt can alter it
    CRITICAL_SECTION_START;
      uint8_t tail = block_buffer_tail;
    CRITICAL_SECTION_END

    uint8_t b = BLOCK_MOD(block_buffer_head - 3);
    while (b != tail) {
      b = prev_block_index(b);
      block[2] = block[1];
      block[1] = block[0];
      block[0] = &block_buffer[b];
      reverse_pass_kernel(block[1], block[2]);
    }
  }
}

// The kernel called by recalculate() when scanning the plan from first to last entry.
void Planner::forward_pass_kernel(const block_t* previous, block_t* const current) {
  if (!previous) return;

  // If the previous block is an acceleration block, but it is not long enough to complete the
  // full speed change within the block, we need to adjust the entry speed accordingly. Entry
  // speeds have already been reset, maximized, and reverse planned by reverse planner.
  // If nominal length is true, max junction speed is guaranteed to be reached. No need to recheck.
  if (!(previous->flag & BLOCK_FLAG_NOMINAL_LENGTH)) {
    if (previous->entry_speed < current->entry_speed) {
      float entry_speed = min(current->entry_speed,
                               max_allowable_speed(-previous->acceleration, previous->entry_speed, previous->millimeters));
      // Check for junction speed change
      if (current->entry_speed != entry_speed) {
        current->entry_speed = entry_speed;
        current->flag |= BLOCK_FLAG_RECALCULATE;
      }
    }
  }
}

/**
 * recalculate() needs to go over the current plan twice.
 * Once in reverse and once forward. This implements the forward pass.
 */
void Planner::forward_pass() {
  block_t* block[3] = { NULL, NULL, NULL };

  for (uint8_t b = block_buffer_tail; b != block_buffer_head; b = next_block_index(b)) {
    block[0] = block[1];
    block[1] = block[2];
    block[2] = &block_buffer[b];
    forward_pass_kernel(block[0], block[1]);
  }
  forward_pass_kernel(block[1], block[2]);
}

/**
 * Recalculate the trapezoid speed profiles for all blocks in the plan
 * according to the entry_factor for each junction. Must be called by
 * recalculate() after updating the blocks.
 */
void Planner::recalculate_trapezoids() {
  int8_t block_index = block_buffer_tail;
  block_t *current, *next = NULL;

  while (block_index != block_buffer_head) {
    current = next;
    next = &block_buffer[block_index];
    if (current) {
      // Recalculate if current block entry or exit junction speed has changed.
      if ((current->flag & BLOCK_FLAG_RECALCULATE) || (next->flag & BLOCK_FLAG_RECALCULATE)) {
        // NOTE: Entry and exit factors always > 0 by all previous logic operations.
        float nom = current->nominal_speed;
        calculate_trapezoid_for_block(current, current->entry_speed / nom, next->entry_speed / nom);
        current->flag &= ~BLOCK_FLAG_RECALCULATE; // Reset current only to ensure next trapezoid is computed
      }
    }
    block_index = next_block_index(block_index);
  }
  // Last/newest block in buffer. Exit speed is set with MINIMUM_PLANNER_SPEED. Always recalculated.
  if (next) {
    float nom = next->nominal_speed;
    calculate_trapezoid_for_block(next, next->entry_speed / nom, (MINIMUM_PLANNER_SPEED) / nom);
    next->flag &= ~BLOCK_FLAG_RECALCULATE;
  }
}

/*
 * Recalculate the motion plan according to the following algorithm:
 *
 *   1. Go over every block in reverse order...
 *
 *      Calculate a junction speed reduction (block_t.entry_factor) so:
 *
 *      a. The junction jerk is within the set limit, and
 *
 *      b. No speed reduction within one block requires faster
 *         deceleration than the one, true constant acceleration.
 *
 *   2. Go over every block in chronological order...
 *
 *      Dial down junction speed reduction values if:
 *      a. The speed increase within one block would require faster
 *         acceleration than the one, true constant acceleration.
 *
 * After that, all blocks will have an entry_factor allowing all speed changes to
 * be performed using only the one, true constant acceleration, and where no junction
 * jerk is jerkier than the set limit, Jerky. Finally it will:
 *
 *   3. Recalculate "trapezoids" for all blocks.
 */
void Planner::recalculate() {
  reverse_pass();
  forward_pass();
  recalculate_trapezoids();
}


#if ENABLED(AUTOTEMP)

  void Planner::getHighESpeed() {
    static float oldt = 0;

    if (!autotemp_enabled) return;
    if (thermalManager.degTargetHotend(0) + 2 < autotemp_min) return; // probably temperature set to zero.

    float high = 0.0;
    for (uint8_t b = block_buffer_tail; b != block_buffer_head; b = next_block_index(b)) {
      block_t* block = &block_buffer[b];
      if (block->steps[X_AXIS] || block->steps[Y_AXIS] || block->steps[Z_AXIS]) {
        float se = (float)block->steps[E_AXIS] / block->step_event_count * block->nominal_speed; // mm/sec;
        NOLESS(high, se);
      }
    }

    float t = autotemp_min + high * autotemp_factor;
    t = constrain(t, autotemp_min, autotemp_max);
    if (oldt > t) {
      t *= (1 - (AUTOTEMP_OLDWEIGHT));
      t += (AUTOTEMP_OLDWEIGHT) * oldt;
    }
    oldt = t;
    thermalManager.setTargetHotend(t, 0);
  }

#endif //AUTOTEMP

/**
 * Maintain fans, paste extruder pressure,
 */
void Planner::check_axes_activity() {
  unsigned char axis_active[NUM_AXIS] = { 0 },
                tail_fan_speed[FAN_COUNT];

  #if FAN_COUNT > 0
    for (uint8_t i = 0; i < FAN_COUNT; i++) tail_fan_speed[i] = fanSpeeds[i];
  #endif

  #if ENABLED(BARICUDA)
    #if HAS_HEATER_1
      unsigned char tail_valve_pressure = baricuda_valve_pressure;
    #endif
    #if HAS_HEATER_2
      unsigned char tail_e_to_p_pressure = baricuda_e_to_p_pressure;
    #endif
  #endif

  if (blocks_queued()) {

    #if FAN_COUNT > 0
      for (uint8_t i = 0; i < FAN_COUNT; i++) tail_fan_speed[i] = block_buffer[block_buffer_tail].fan_speed[i];
    #endif

    block_t* block;

    #if ENABLED(BARICUDA)
      block = &block_buffer[block_buffer_tail];
      #if HAS_HEATER_1
        tail_valve_pressure = block->valve_pressure;
      #endif
      #if HAS_HEATER_2
        tail_e_to_p_pressure = block->e_to_p_pressure;
      #endif
    #endif

    for (uint8_t b = block_buffer_tail; b != block_buffer_head; b = next_block_index(b)) {
      block = &block_buffer[b];
      LOOP_XYZE(i) if (block->steps[i]) axis_active[i]++;
    }
  }
  #if ENABLED(DISABLE_X)
    if (!axis_active[X_AXIS]) disable_x();
  #endif
  #if ENABLED(DISABLE_Y)
    if (!axis_active[Y_AXIS]) disable_y();
  #endif
  #if ENABLED(DISABLE_Z)
    if (!axis_active[Z_AXIS]) disable_z();
  #endif
  #if ENABLED(DISABLE_E)
    if (!axis_active[E_AXIS]) {
      disable_e0();
      disable_e1();
      disable_e2();
      disable_e3();
    }
  #endif

  #if FAN_COUNT > 0

    #if defined(FAN_MIN_PWM)
      #define CALC_FAN_SPEED(f) (tail_fan_speed[f] ? ( FAN_MIN_PWM + (tail_fan_speed[f] * (255 - FAN_MIN_PWM)) / 255 ) : 0)
    #else
      #define CALC_FAN_SPEED(f) tail_fan_speed[f]
    #endif

    #ifdef FAN_KICKSTART_TIME

      static millis_t fan_kick_end[FAN_COUNT] = { 0 };

      #define KICKSTART_FAN(f) \
        if (tail_fan_speed[f]) { \
          millis_t ms = millis(); \
          if (fan_kick_end[f] == 0) { \
            fan_kick_end[f] = ms + FAN_KICKSTART_TIME; \
            tail_fan_speed[f] = 255; \
          } else { \
            if (PENDING(ms, fan_kick_end[f])) { \
              tail_fan_speed[f] = 255; \
            } \
          } \
        } else { \
          fan_kick_end[f] = 0; \
        }

      #if HAS_FAN0
        KICKSTART_FAN(0);
      #endif
      #if HAS_FAN1
        KICKSTART_FAN(1);
      #endif
      #if HAS_FAN2
        KICKSTART_FAN(2);
      #endif

    #endif //FAN_KICKSTART_TIME

    #if ENABLED(FAN_SOFT_PWM)
      #if HAS_FAN0
        thermalManager.fanSpeedSoftPwm[0] = CALC_FAN_SPEED(0);
      #endif
      #if HAS_FAN1
        thermalManager.fanSpeedSoftPwm[1] = CALC_FAN_SPEED(1);
      #endif
      #if HAS_FAN2
        thermalManager.fanSpeedSoftPwm[2] = CALC_FAN_SPEED(2);
      #endif
    #else
      #if HAS_FAN0
        analogWrite(FAN_PIN, CALC_FAN_SPEED(0));
      #endif
      #if HAS_FAN1
        analogWrite(FAN1_PIN, CALC_FAN_SPEED(1));
      #endif
      #if HAS_FAN2
        analogWrite(FAN2_PIN, CALC_FAN_SPEED(2));
      #endif
    #endif

  #endif // FAN_COUNT > 0

  #if ENABLED(AUTOTEMP)
    getHighESpeed();
  #endif

  #if ENABLED(BARICUDA)
    #if HAS_HEATER_1
      analogWrite(HEATER_1_PIN, tail_valve_pressure);
    #endif
    #if HAS_HEATER_2
      analogWrite(HEATER_2_PIN, tail_e_to_p_pressure);
    #endif
  #endif
}

#if PLANNER_LEVELING
  /**
   * lx, ly, lz - logical (cartesian, not delta) positions in mm
   */
  void Planner::apply_leveling(float &lx, float &ly, float &lz) {

    #if HAS_ABL
      if (!abl_enabled) return;
    #endif

    #if ENABLED(MESH_BED_LEVELING)

      if (mbl.active())
        lz += mbl.get_z(RAW_X_POSITION(lx), RAW_Y_POSITION(ly));

    #elif ABL_PLANAR

      float dx = RAW_X_POSITION(lx) - (X_TILT_FULCRUM),
            dy = RAW_Y_POSITION(ly) - (Y_TILT_FULCRUM),
            dz = RAW_Z_POSITION(lz);

      apply_rotation_xyz(bed_level_matrix, dx, dy, dz);

      lx = LOGICAL_X_POSITION(dx + X_TILT_FULCRUM);
      ly = LOGICAL_Y_POSITION(dy + Y_TILT_FULCRUM);
      lz = LOGICAL_Z_POSITION(dz);

    #elif ENABLED(AUTO_BED_LEVELING_BILINEAR)

      float tmp[XYZ] = { lx, ly, 0 };
      lz += bilinear_z_offset(tmp);

    #endif
  }

  void Planner::unapply_leveling(float logical[XYZ]) {

    #if HAS_ABL
      if (!abl_enabled) return;
    #endif

    #if ENABLED(MESH_BED_LEVELING)

      if (mbl.active())
        logical[Z_AXIS] -= mbl.get_z(RAW_X_POSITION(logical[X_AXIS]), RAW_Y_POSITION(logical[Y_AXIS]));

    #elif ABL_PLANAR

      matrix_3x3 inverse = matrix_3x3::transpose(bed_level_matrix);

      float dx = RAW_X_POSITION(logical[X_AXIS]) - (X_TILT_FULCRUM),
            dy = RAW_Y_POSITION(logical[Y_AXIS]) - (Y_TILT_FULCRUM),
            dz = RAW_Z_POSITION(logical[Z_AXIS]);

      apply_rotation_xyz(inverse, dx, dy, dz);

      logical[X_AXIS] = LOGICAL_X_POSITION(dx + X_TILT_FULCRUM);
      logical[Y_AXIS] = LOGICAL_Y_POSITION(dy + Y_TILT_FULCRUM);
      logical[Z_AXIS] = LOGICAL_Z_POSITION(dz);

    #elif ENABLED(AUTO_BED_LEVELING_BILINEAR)

      logical[Z_AXIS] -= bilinear_z_offset(logical);

    #endif
  }

#endif // PLANNER_LEVELING

/**
 * Planner::_buffer_line
 *
 * Add a new linear movement to the buffer.
 *
 * Leveling and kinematics should be applied ahead of calling this.
 *
 *  a,b,c,e     - target positions in mm or degrees
 *  fr_mm_s     - (target) speed of the move
 *  extruder    - target extruder
 */
void Planner::_buffer_line(const float &a, const float &b, const float &c, const float &e, float fr_mm_s, const uint8_t extruder) {
  // Calculate the buffer head after we push this byte
  int next_buffer_head = next_block_index(block_buffer_head);

  // If the buffer is full: good! That means we are well ahead of the robot.
  // Rest here until there is room in the buffer.
  while (block_buffer_tail == next_buffer_head) idle();

  // The target position of the tool in absolute steps
  // Calculate target position in absolute steps
  //this should be done after the wait, because otherwise a M92 code within the gcode disrupts this calculation somehow
  long target[XYZE] = {
    lround(a * axis_steps_per_mm[X_AXIS]),
    lround(b * axis_steps_per_mm[Y_AXIS]),
    lround(c * axis_steps_per_mm[Z_AXIS]),
    lround(e * axis_steps_per_mm[E_AXIS])
  };

  long da = target[X_AXIS] - position[X_AXIS],
       db = target[Y_AXIS] - position[Y_AXIS],
       dc = target[Z_AXIS] - position[Z_AXIS];

  /*
  SERIAL_ECHOPAIR("  Planner FR:", fr_mm_s);
  SERIAL_CHAR(' ');
  #if IS_KINEMATIC
    SERIAL_ECHOPAIR("A:", a);
    SERIAL_ECHOPAIR(" (", da);
    SERIAL_ECHOPAIR(") B:", b);
  #else
    SERIAL_ECHOPAIR("X:", a);
    SERIAL_ECHOPAIR(" (", da);
    SERIAL_ECHOPAIR(") Y:", b);
  #endif
  SERIAL_ECHOPAIR(" (", db);
  #if ENABLED(DELTA)
    SERIAL_ECHOPAIR(") C:", c);
  #else
    SERIAL_ECHOPAIR(") Z:", c);
  #endif
  SERIAL_ECHOPAIR(" (", dc);
  SERIAL_CHAR(')');
  SERIAL_EOL;
  //*/

  // DRYRUN ignores all temperature constraints and assures that the extruder is instantly satisfied
  if (DEBUGGING(DRYRUN)) position[E_AXIS] = target[E_AXIS];

  long de = target[E_AXIS] - position[E_AXIS];

  #if ENABLED(PREVENT_COLD_EXTRUSION)
    if (de) {
      if (thermalManager.tooColdToExtrude(extruder)) {
        position[E_AXIS] = target[E_AXIS]; // Behave as if the move really took place, but ignore E part
        de = 0; // no difference
        SERIAL_ECHO_START;
        SERIAL_ECHOLNPGM(MSG_ERR_COLD_EXTRUDE_STOP);
      }
      #if ENABLED(PREVENT_LENGTHY_EXTRUDE)
        if (labs(de) > axis_steps_per_mm[E_AXIS] * (EXTRUDE_MAXLENGTH)) {
          position[E_AXIS] = target[E_AXIS]; // Behave as if the move really took place, but ignore E part
          de = 0; // no difference
          SERIAL_ECHO_START;
          SERIAL_ECHOLNPGM(MSG_ERR_LONG_EXTRUDE_STOP);
        }
      #endif
    }
  #endif

  // Prepare to set up new block
  block_t* block = &block_buffer[block_buffer_head];

  // Mark block as not busy (Not executed by the stepper interrupt)
  block->busy = false;

  // Number of steps for each axis
  #if ENABLED(COREXY)
    // corexy planning
    // these equations follow the form of the dA and dB equations on http://www.corexy.com/theory.html
    block->steps[A_AXIS] = labs(da + db);
    block->steps[B_AXIS] = labs(da - db);
    block->steps[Z_AXIS] = labs(dc);
  #elif ENABLED(COREXZ)
    // corexz planning
    block->steps[A_AXIS] = labs(da + dc);
    block->steps[Y_AXIS] = labs(db);
    block->steps[C_AXIS] = labs(da - dc);
  #elif ENABLED(COREYZ)
    // coreyz planning
    block->steps[X_AXIS] = labs(da);
    block->steps[B_AXIS] = labs(db + dc);
    block->steps[C_AXIS] = labs(db - dc);
  #else
    // default non-h-bot planning
    block->steps[X_AXIS] = labs(da);
    block->steps[Y_AXIS] = labs(db);
    block->steps[Z_AXIS] = labs(dc);
  #endif

  block->steps[E_AXIS] = labs(de) * volumetric_multiplier[extruder] * flow_percentage[extruder] * 0.01 + 0.5;
  block->step_event_count = MAX4(block->steps[X_AXIS], block->steps[Y_AXIS], block->steps[Z_AXIS], block->steps[E_AXIS]);

  // Bail if this is a zero-length block
  if (block->step_event_count < MIN_STEPS_PER_SEGMENT) return;

  // For a mixing extruder, get a magnified step_event_count for each
  #if ENABLED(MIXING_EXTRUDER)
    for (uint8_t i = 0; i < MIXING_STEPPERS; i++)
      block->mix_event_count[i] = UNEAR_ZERO(mixing_factor[i]) ? 0 : block->step_event_count / mixing_factor[i];
  #endif

  #if FAN_COUNT > 0
    for (uint8_t i = 0; i < FAN_COUNT; i++) block->fan_speed[i] = fanSpeeds[i];
  #endif

  #if ENABLED(BARICUDA)
    block->valve_pressure = baricuda_valve_pressure;
    block->e_to_p_pressure = baricuda_e_to_p_pressure;
  #endif

  // Compute direction bit-mask for this block
  uint8_t dm = 0;
  #if ENABLED(COREXY)
    if (da < 0) SBI(dm, X_HEAD); // Save the real Extruder (head) direction in X Axis
    if (db < 0) SBI(dm, Y_HEAD); // ...and Y
    if (dc < 0) SBI(dm, Z_AXIS);
    if (da + db < 0) SBI(dm, A_AXIS); // Motor A direction
    if (da - db < 0) SBI(dm, B_AXIS); // Motor B direction
  #elif ENABLED(COREXZ)
    if (da < 0) SBI(dm, X_HEAD); // Save the real Extruder (head) direction in X Axis
    if (db < 0) SBI(dm, Y_AXIS);
    if (dc < 0) SBI(dm, Z_HEAD); // ...and Z
    if (da + dc < 0) SBI(dm, A_AXIS); // Motor A direction
    if (da - dc < 0) SBI(dm, C_AXIS); // Motor C direction
  #elif ENABLED(COREYZ)
    if (da < 0) SBI(dm, X_AXIS);
    if (db < 0) SBI(dm, Y_HEAD); // Save the real Extruder (head) direction in Y Axis
    if (dc < 0) SBI(dm, Z_HEAD); // ...and Z
    if (db + dc < 0) SBI(dm, B_AXIS); // Motor B direction
    if (db - dc < 0) SBI(dm, C_AXIS); // Motor C direction
  #else
    if (da < 0) SBI(dm, X_AXIS);
    if (db < 0) SBI(dm, Y_AXIS);
    if (dc < 0) SBI(dm, Z_AXIS);
  #endif
  if (de < 0) SBI(dm, E_AXIS);
  block->direction_bits = dm;

  block->active_extruder = extruder;

  //enable active axes
  #if ENABLED(COREXY)
    if (block->steps[A_AXIS] || block->steps[B_AXIS]) {
      enable_x();
      enable_y();
    }
    #if DISABLED(Z_LATE_ENABLE)
      if (block->steps[Z_AXIS]) enable_z();
    #endif
  #elif ENABLED(COREXZ)
    if (block->steps[A_AXIS] || block->steps[C_AXIS]) {
      enable_x();
      enable_z();
    }
    if (block->steps[Y_AXIS]) enable_y();
  #else
    if (block->steps[X_AXIS]) enable_x();
    if (block->steps[Y_AXIS]) enable_y();
    #if DISABLED(Z_LATE_ENABLE)
      if (block->steps[Z_AXIS]) enable_z();
    #endif
  #endif

  // Enable extruder(s)
  if (block->steps[E_AXIS]) {

    #if ENABLED(DISABLE_INACTIVE_EXTRUDER) // Enable only the selected extruder

      for (int i = 0; i < EXTRUDERS; i++)
        if (g_uc_extruder_last_move[i] > 0) g_uc_extruder_last_move[i]--;

      switch(extruder) {
        case 0:
          enable_e0();
          #if ENABLED(DUAL_X_CARRIAGE)
            if (extruder_duplication_enabled) {
              enable_e1();
              g_uc_extruder_last_move[1] = (BLOCK_BUFFER_SIZE) * 2;
            }
          #endif
          g_uc_extruder_last_move[0] = (BLOCK_BUFFER_SIZE) * 2;
          #if EXTRUDERS > 1
            if (g_uc_extruder_last_move[1] == 0) disable_e1();
            #if EXTRUDERS > 2
              if (g_uc_extruder_last_move[2] == 0) disable_e2();
              #if EXTRUDERS > 3
                if (g_uc_extruder_last_move[3] == 0) disable_e3();
              #endif
            #endif
          #endif
        break;
        #if EXTRUDERS > 1
          case 1:
            enable_e1();
            g_uc_extruder_last_move[1] = (BLOCK_BUFFER_SIZE) * 2;
            if (g_uc_extruder_last_move[0] == 0) disable_e0();
            #if EXTRUDERS > 2
              if (g_uc_extruder_last_move[2] == 0) disable_e2();
              #if EXTRUDERS > 3
                if (g_uc_extruder_last_move[3] == 0) disable_e3();
              #endif
            #endif
          break;
          #if EXTRUDERS > 2
            case 2:
              enable_e2();
              g_uc_extruder_last_move[2] = (BLOCK_BUFFER_SIZE) * 2;
              if (g_uc_extruder_last_move[0] == 0) disable_e0();
              if (g_uc_extruder_last_move[1] == 0) disable_e1();
              #if EXTRUDERS > 3
                if (g_uc_extruder_last_move[3] == 0) disable_e3();
              #endif
            break;
            #if EXTRUDERS > 3
              case 3:
                enable_e3();
                g_uc_extruder_last_move[3] = (BLOCK_BUFFER_SIZE) * 2;
                if (g_uc_extruder_last_move[0] == 0) disable_e0();
                if (g_uc_extruder_last_move[1] == 0) disable_e1();
                if (g_uc_extruder_last_move[2] == 0) disable_e2();
              break;
            #endif // EXTRUDERS > 3
          #endif // EXTRUDERS > 2
        #endif // EXTRUDERS > 1
      }
    #else
      enable_e0();
      enable_e1();
      enable_e2();
      enable_e3();
    #endif
  }

  if (block->steps[E_AXIS])
    NOLESS(fr_mm_s, min_feedrate_mm_s);
  else
    NOLESS(fr_mm_s, min_travel_feedrate_mm_s);

  /**
   * This part of the code calculates the total length of the movement.
   * For cartesian bots, the X_AXIS is the real X movement and same for Y_AXIS.
   * But for corexy bots, that is not true. The "X_AXIS" and "Y_AXIS" motors (that should be named to A_AXIS
   * and B_AXIS) cannot be used for X and Y length, because A=X+Y and B=X-Y.
   * So we need to create other 2 "AXIS", named X_HEAD and Y_HEAD, meaning the real displacement of the Head.
   * Having the real displacement of the head, we can calculate the total movement length and apply the desired speed.
   */
  #if ENABLED(COREXY) || ENABLED(COREXZ) || ENABLED(COREYZ)
    float delta_mm[7];
    #if ENABLED(COREXY)
      delta_mm[X_HEAD] = da * steps_to_mm[A_AXIS];
      delta_mm[Y_HEAD] = db * steps_to_mm[B_AXIS];
      delta_mm[Z_AXIS] = dc * steps_to_mm[Z_AXIS];
      delta_mm[A_AXIS] = (da + db) * steps_to_mm[A_AXIS];
      delta_mm[B_AXIS] = (da - db) * steps_to_mm[B_AXIS];
    #elif ENABLED(COREXZ)
      delta_mm[X_HEAD] = da * steps_to_mm[A_AXIS];
      delta_mm[Y_AXIS] = db * steps_to_mm[Y_AXIS];
      delta_mm[Z_HEAD] = dc * steps_to_mm[C_AXIS];
      delta_mm[A_AXIS] = (da + dc) * steps_to_mm[A_AXIS];
      delta_mm[C_AXIS] = (da - dc) * steps_to_mm[C_AXIS];
    #elif ENABLED(COREYZ)
      delta_mm[X_AXIS] = da * steps_to_mm[X_AXIS];
      delta_mm[Y_HEAD] = db * steps_to_mm[B_AXIS];
      delta_mm[Z_HEAD] = dc * steps_to_mm[C_AXIS];
      delta_mm[B_AXIS] = (db + dc) * steps_to_mm[B_AXIS];
      delta_mm[C_AXIS] = (db - dc) * steps_to_mm[C_AXIS];
    #endif
  #else
    float delta_mm[4];
    delta_mm[X_AXIS] = da * steps_to_mm[X_AXIS];
    delta_mm[Y_AXIS] = db * steps_to_mm[Y_AXIS];
    delta_mm[Z_AXIS] = dc * steps_to_mm[Z_AXIS];
  #endif
  delta_mm[E_AXIS] = 0.01 * (de * steps_to_mm[E_AXIS]) * volumetric_multiplier[extruder] * flow_percentage[extruder];

  if (block->steps[X_AXIS] < MIN_STEPS_PER_SEGMENT && block->steps[Y_AXIS] < MIN_STEPS_PER_SEGMENT && block->steps[Z_AXIS] < MIN_STEPS_PER_SEGMENT) {
    block->millimeters = fabs(delta_mm[E_AXIS]);
  }
  else {
    block->millimeters = sqrt(
      #if ENABLED(COREXY)
        sq(delta_mm[X_HEAD]) + sq(delta_mm[Y_HEAD]) + sq(delta_mm[Z_AXIS])
      #elif ENABLED(COREXZ)
        sq(delta_mm[X_HEAD]) + sq(delta_mm[Y_AXIS]) + sq(delta_mm[Z_HEAD])
      #elif ENABLED(COREYZ)
        sq(delta_mm[X_AXIS]) + sq(delta_mm[Y_HEAD]) + sq(delta_mm[Z_HEAD])
      #else
        sq(delta_mm[X_AXIS]) + sq(delta_mm[Y_AXIS]) + sq(delta_mm[Z_AXIS])
      #endif
    );
  }
  float inverse_millimeters = 1.0 / block->millimeters;  // Inverse millimeters to remove multiple divides

  // Calculate moves/second for this move. No divide by zero due to previous checks.
  float inverse_mm_s = fr_mm_s * inverse_millimeters;

  int moves_queued = movesplanned();

  // Slow down when the buffer starts to empty, rather than wait at the corner for a buffer refill
  #if ENABLED(OLD_SLOWDOWN) || ENABLED(SLOWDOWN)
    bool mq = moves_queued > 1 && moves_queued < (BLOCK_BUFFER_SIZE) / 2;
    #if ENABLED(OLD_SLOWDOWN)
      if (mq) fr_mm_s *= 2.0 * moves_queued / (BLOCK_BUFFER_SIZE);
    #endif
    #if ENABLED(SLOWDOWN)
      //  segment time im micro seconds
      unsigned long segment_time = lround(1000000.0/inverse_mm_s);
      if (mq) {
        if (segment_time < min_segment_time) {
          // buffer is draining, add extra time.  The amount of time added increases if the buffer is still emptied more.
          inverse_mm_s = 1000000.0 / (segment_time + lround(2 * (min_segment_time - segment_time) / moves_queued));
          #ifdef XY_FREQUENCY_LIMIT
            segment_time = lround(1000000.0 / inverse_mm_s);
          #endif
        }
      }
    #endif
  #endif

  block->nominal_speed = block->millimeters * inverse_mm_s; // (mm/sec) Always > 0
  block->nominal_rate = ceil(block->step_event_count * inverse_mm_s); // (step/sec) Always > 0

  #if ENABLED(FILAMENT_WIDTH_SENSOR)
    static float filwidth_e_count = 0, filwidth_delay_dist = 0;

    //FMM update ring buffer used for delay with filament measurements
    if (extruder == FILAMENT_SENSOR_EXTRUDER_NUM && filwidth_delay_index[1] >= 0) {  //only for extruder with filament sensor and if ring buffer is initialized

      const int MMD_CM = MAX_MEASUREMENT_DELAY + 1, MMD_MM = MMD_CM * 10;

      // increment counters with next move in e axis
      filwidth_e_count += delta_mm[E_AXIS];
      filwidth_delay_dist += delta_mm[E_AXIS];

      // Only get new measurements on forward E movement
      if (filwidth_e_count > 0.0001) {

        // Loop the delay distance counter (modulus by the mm length)
        while (filwidth_delay_dist >= MMD_MM) filwidth_delay_dist -= MMD_MM;

        // Convert into an index into the measurement array
        filwidth_delay_index[0] = (int)(filwidth_delay_dist * 0.1 + 0.0001);

        // If the index has changed (must have gone forward)...
        if (filwidth_delay_index[0] != filwidth_delay_index[1]) {
          filwidth_e_count = 0; // Reset the E movement counter
          int8_t meas_sample = thermalManager.widthFil_to_size_ratio() - 100; // Subtract 100 to reduce magnitude - to store in a signed char
          do {
            filwidth_delay_index[1] = (filwidth_delay_index[1] + 1) % MMD_CM; // The next unused slot
            measurement_delay[filwidth_delay_index[1]] = meas_sample;         // Store the measurement
          } while (filwidth_delay_index[0] != filwidth_delay_index[1]);       // More slots to fill?
        }
      }
    }
  #endif

  // Calculate and limit speed in mm/sec for each axis
  float current_speed[NUM_AXIS], speed_factor = 1.0; // factor <1 decreases speed
  LOOP_XYZE(i) {
    float cs = fabs(current_speed[i] = delta_mm[i] * inverse_mm_s);
    if (cs > max_feedrate_mm_s[i]) NOMORE(speed_factor, max_feedrate_mm_s[i] / cs);
  }

  // Max segment time in µs.
  #ifdef XY_FREQUENCY_LIMIT

    // Check and limit the xy direction change frequency
    unsigned char direction_change = block->direction_bits ^ old_direction_bits;
    old_direction_bits = block->direction_bits;
    segment_time = lround((float)segment_time / speed_factor);

    long xs0 = axis_segment_time[X_AXIS][0],
         xs1 = axis_segment_time[X_AXIS][1],
         xs2 = axis_segment_time[X_AXIS][2],
         ys0 = axis_segment_time[Y_AXIS][0],
         ys1 = axis_segment_time[Y_AXIS][1],
         ys2 = axis_segment_time[Y_AXIS][2];

    if (TEST(direction_change, X_AXIS)) {
      xs2 = axis_segment_time[X_AXIS][2] = xs1;
      xs1 = axis_segment_time[X_AXIS][1] = xs0;
      xs0 = 0;
    }
    xs0 = axis_segment_time[X_AXIS][0] = xs0 + segment_time;

    if (TEST(direction_change, Y_AXIS)) {
      ys2 = axis_segment_time[Y_AXIS][2] = axis_segment_time[Y_AXIS][1];
      ys1 = axis_segment_time[Y_AXIS][1] = axis_segment_time[Y_AXIS][0];
      ys0 = 0;
    }
    ys0 = axis_segment_time[Y_AXIS][0] = ys0 + segment_time;

    long max_x_segment_time = MAX3(xs0, xs1, xs2),
         max_y_segment_time = MAX3(ys0, ys1, ys2),
         min_xy_segment_time = min(max_x_segment_time, max_y_segment_time);
    if (min_xy_segment_time < MAX_FREQ_TIME) {
      float low_sf = speed_factor * min_xy_segment_time / (MAX_FREQ_TIME);
      NOMORE(speed_factor, low_sf);
    }
  #endif // XY_FREQUENCY_LIMIT

  // Correct the speed
  if (speed_factor < 1.0) {
    LOOP_XYZE(i) current_speed[i] *= speed_factor;
    block->nominal_speed *= speed_factor;
    block->nominal_rate *= speed_factor;
  }

  // Compute and limit the acceleration rate for the trapezoid generator.
  float steps_per_mm = block->step_event_count / block->millimeters;
  if (!block->steps[X_AXIS] && !block->steps[Y_AXIS] && !block->steps[Z_AXIS]) {
    block->acceleration_steps_per_s2 = ceil(retract_acceleration * steps_per_mm); // convert to: acceleration steps/sec^2
  }
  else {
    // Limit acceleration per axis
    block->acceleration_steps_per_s2 = ceil((block->steps[E_AXIS] ? acceleration : travel_acceleration) * steps_per_mm);
    if (max_acceleration_steps_per_s2[X_AXIS] < (block->acceleration_steps_per_s2 * block->steps[X_AXIS]) / block->step_event_count)
      block->acceleration_steps_per_s2 = (max_acceleration_steps_per_s2[X_AXIS] * block->step_event_count) / block->steps[X_AXIS];
    if (max_acceleration_steps_per_s2[Y_AXIS] < (block->acceleration_steps_per_s2 * block->steps[Y_AXIS]) / block->step_event_count)
      block->acceleration_steps_per_s2 = (max_acceleration_steps_per_s2[Y_AXIS] * block->step_event_count) / block->steps[Y_AXIS];
    if (max_acceleration_steps_per_s2[Z_AXIS] < (block->acceleration_steps_per_s2 * block->steps[Z_AXIS]) / block->step_event_count)
      block->acceleration_steps_per_s2 = (max_acceleration_steps_per_s2[Z_AXIS] * block->step_event_count) / block->steps[Z_AXIS];
    if (max_acceleration_steps_per_s2[E_AXIS] < (block->acceleration_steps_per_s2 * block->steps[E_AXIS]) / block->step_event_count)
      block->acceleration_steps_per_s2 = (max_acceleration_steps_per_s2[E_AXIS] * block->step_event_count) / block->steps[E_AXIS];
  }
  block->acceleration = block->acceleration_steps_per_s2 / steps_per_mm;
  block->acceleration_rate = (long)(block->acceleration_steps_per_s2 * 16777216.0 / ((F_CPU) * 0.125));

  #if 0  // Use old jerk for now

    float junction_deviation = 0.1;

    // Compute path unit vector
    double unit_vec[XYZ];

    unit_vec[X_AXIS] = delta_mm[X_AXIS] * inverse_millimeters;
    unit_vec[Y_AXIS] = delta_mm[Y_AXIS] * inverse_millimeters;
    unit_vec[Z_AXIS] = delta_mm[Z_AXIS] * inverse_millimeters;

    // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
    // Let a circle be tangent to both previous and current path line segments, where the junction
    // deviation is defined as the distance from the junction to the closest edge of the circle,
    // collinear with the circle center. The circular segment joining the two paths represents the
    // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
    // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
    // path width or max_jerk in the previous grbl version. This approach does not actually deviate
    // from path, but used as a robust way to compute cornering speeds, as it takes into account the
    // nonlinearities of both the junction angle and junction velocity.
    double vmax_junction = MINIMUM_PLANNER_SPEED; // Set default max junction speed

    // Skip first block or when previous_nominal_speed is used as a flag for homing and offset cycles.
    if ((block_buffer_head != block_buffer_tail) && (previous_nominal_speed > 0.0)) {
      // Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
      // NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
      double cos_theta = - previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
                         - previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
                         - previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS] ;
      // Skip and use default max junction speed for 0 degree acute junction.
      if (cos_theta < 0.95) {
        vmax_junction = min(previous_nominal_speed, block->nominal_speed);
        // Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
        if (cos_theta > -0.95) {
          // Compute maximum junction velocity based on maximum acceleration and junction deviation
          double sin_theta_d2 = sqrt(0.5 * (1.0 - cos_theta)); // Trig half angle identity. Always positive.
          NOMORE(vmax_junction, sqrt(block->acceleration * junction_deviation * sin_theta_d2 / (1.0 - sin_theta_d2)));
        }
      }
    }
  #endif

  // Start with a safe speed
  float vmax_junction = max_jerk[X_AXIS] * 0.5, vmax_junction_factor = 1.0;
  if (max_jerk[Y_AXIS] * 0.5 < fabs(current_speed[Y_AXIS])) NOMORE(vmax_junction, max_jerk[Y_AXIS] * 0.5);
  if (max_jerk[Z_AXIS] * 0.5 < fabs(current_speed[Z_AXIS])) NOMORE(vmax_junction, max_jerk[Z_AXIS] * 0.5);
  if (max_jerk[E_AXIS] * 0.5 < fabs(current_speed[E_AXIS])) NOMORE(vmax_junction, max_jerk[E_AXIS] * 0.5);
  NOMORE(vmax_junction, block->nominal_speed);
  float safe_speed = vmax_junction;

  if (moves_queued > 1 && previous_nominal_speed > 0.0001) {
    //if ((fabs(previous_speed[X_AXIS]) > 0.0001) || (fabs(previous_speed[Y_AXIS]) > 0.0001)) {
        vmax_junction = block->nominal_speed;
    //}

    float dsx = fabs(current_speed[X_AXIS] - previous_speed[X_AXIS]),
          dsy = fabs(current_speed[Y_AXIS] - previous_speed[Y_AXIS]),
          dsz = fabs(current_speed[Z_AXIS] - previous_speed[Z_AXIS]),
          dse = fabs(current_speed[E_AXIS] - previous_speed[E_AXIS]);
    if (dsx > max_jerk[X_AXIS]) NOMORE(vmax_junction_factor, max_jerk[X_AXIS] / dsx);
    if (dsy > max_jerk[Y_AXIS]) NOMORE(vmax_junction_factor, max_jerk[Y_AXIS] / dsy);
    if (dsz > max_jerk[Z_AXIS]) NOMORE(vmax_junction_factor, max_jerk[Z_AXIS] / dsz);
    if (dse > max_jerk[E_AXIS]) NOMORE(vmax_junction_factor, max_jerk[E_AXIS] / dse);

    vmax_junction = min(previous_nominal_speed, vmax_junction * vmax_junction_factor); // Limit speed to max previous speed
  }
  block->max_entry_speed = vmax_junction;

  // Initialize block entry speed. Compute based on deceleration to user-defined MINIMUM_PLANNER_SPEED.
  float v_allowable = max_allowable_speed(-block->acceleration, MINIMUM_PLANNER_SPEED, block->millimeters);
  block->entry_speed = min(vmax_junction, v_allowable);

  // Initialize planner efficiency flags
  // Set flag if block will always reach maximum junction speed regardless of entry/exit speeds.
  // If a block can de/ac-celerate from nominal speed to zero within the length of the block, then
  // the current block and next block junction speeds are guaranteed to always be at their maximum
  // junction speeds in deceleration and acceleration, respectively. This is due to how the current
  // block nominal speed limits both the current and next maximum junction speeds. Hence, in both
  // the reverse and forward planners, the corresponding block junction speed will always be at the
  // the maximum junction speed and may always be ignored for any speed reduction checks.
  block->flag &= ~BLOCK_FLAG_NOMINAL_LENGTH;
  if (block->nominal_speed <= v_allowable) block->flag |= BLOCK_FLAG_NOMINAL_LENGTH;
  block->flag |= BLOCK_FLAG_RECALCULATE; // Always calculate trapezoid for new block

  // Update previous path unit_vector and nominal speed
  memcpy(previous_speed, current_speed, sizeof(previous_speed));
  previous_nominal_speed = block->nominal_speed;

  #if ENABLED(LIN_ADVANCE)

    // block->steps[E_AXIS] == block->step_event_count: A problem occurs when there's a very tiny move before a retract.
    // In this case, the retract and the move will be executed together.
    // This leads to an enormous number of advance steps due to a huge e_acceleration.
    // The math is correct, but you don't want a retract move done with advance!
    // So this situation is filtered out here.
    if (!block->steps[E_AXIS] || (!block->steps[X_AXIS] && !block->steps[Y_AXIS] && !block->steps[Z_AXIS]) || stepper.get_advance_k() == 0 || (uint32_t) block->steps[E_AXIS] == block->step_event_count) {
      block->use_advance_lead = false;
    }
    else {
      block->use_advance_lead = true;
      block->e_speed_multiplier8 = (block->steps[E_AXIS] << 8) / block->step_event_count;
    }

  #elif ENABLED(ADVANCE)

    // Calculate advance rate
    if (!block->steps[E_AXIS] || (!block->steps[X_AXIS] && !block->steps[Y_AXIS] && !block->steps[Z_AXIS])) {
      block->advance_rate = 0;
      block->advance = 0;
    }
    else {
      long acc_dist = estimate_acceleration_distance(0, block->nominal_rate, block->acceleration_steps_per_s2);
      float advance = ((STEPS_PER_CUBIC_MM_E) * (EXTRUDER_ADVANCE_K)) * HYPOT(current_speed[E_AXIS], EXTRUSION_AREA) * 256;
      block->advance = advance;
      block->advance_rate = acc_dist ? advance / (float)acc_dist : 0;
    }
    /**
     SERIAL_ECHO_START;
     SERIAL_ECHOPGM("advance :");
     SERIAL_ECHO(block->advance/256.0);
     SERIAL_ECHOPGM("advance rate :");
     SERIAL_ECHOLN(block->advance_rate/256.0);
     */

  #endif // ADVANCE or LIN_ADVANCE

  calculate_trapezoid_for_block(block, block->entry_speed / block->nominal_speed, safe_speed / block->nominal_speed);

  // Move buffer head
  block_buffer_head = next_buffer_head;

  // Update the position (only when a move was queued)
  memcpy(position, target, sizeof(position));

  recalculate();

  stepper.wake_up();

} // buffer_line()

/**
 * Directly set the planner XYZ position (and stepper positions)
 * converting mm (or angles for SCARA) into steps.
 *
 * On CORE machines stepper ABC will be translated from the given XYZ.
 */

void Planner::_set_position_mm(const float &a, const float &b, const float &c, const float &e) {
  long na = position[X_AXIS] = lround(a * axis_steps_per_mm[X_AXIS]),
       nb = position[Y_AXIS] = lround(b * axis_steps_per_mm[Y_AXIS]),
       nc = position[Z_AXIS] = lround(c * axis_steps_per_mm[Z_AXIS]),
       ne = position[E_AXIS] = lround(e * axis_steps_per_mm[E_AXIS]);
  stepper.set_position(na, nb, nc, ne);
  previous_nominal_speed = 0.0; // Resets planner junction speeds. Assumes start from rest.

  memset(previous_speed, 0, sizeof(previous_speed));
}

void Planner::set_position_mm_kinematic(const float position[NUM_AXIS]) {
  #if PLANNER_LEVELING
    float pos[XYZ] = { position[X_AXIS], position[Y_AXIS], position[Z_AXIS] };
    apply_leveling(pos);
  #else
    const float * const pos = position;
  #endif
  #if IS_KINEMATIC
    inverse_kinematics(pos);
    _set_position_mm(delta[A_AXIS], delta[B_AXIS], delta[C_AXIS], position[E_AXIS]);
  #else
    _set_position_mm(pos[X_AXIS], pos[Y_AXIS], pos[Z_AXIS], position[E_AXIS]);
  #endif
}


/**
 * Sync from the stepper positions. (e.g., after an interrupted move)
 */
void Planner::sync_from_steppers() {
  LOOP_XYZE(i) position[i] = stepper.position((AxisEnum)i);
}

/**
 * Setters for planner position (also setting stepper position).
 */
void Planner::set_position_mm(const AxisEnum axis, const float& v) {
  position[axis] = lround(v * axis_steps_per_mm[axis]);
  stepper.set_position(axis, v);
  previous_speed[axis] = 0.0;
}

// Recalculate the steps/s^2 acceleration rates, based on the mm/s^2
void Planner::reset_acceleration_rates() {
  LOOP_XYZE(i)
    max_acceleration_steps_per_s2[i] = max_acceleration_mm_per_s2[i] * axis_steps_per_mm[i];
}

// Recalculate position, steps_to_mm if axis_steps_per_mm changes!
void Planner::refresh_positioning() {
  LOOP_XYZE(i) steps_to_mm[i] = 1.0 / axis_steps_per_mm[i];
  set_position_mm_kinematic(current_position);
  reset_acceleration_rates();
}

#if ENABLED(AUTOTEMP)

  void Planner::autotemp_M109() {
    autotemp_enabled = code_seen('F');
    if (autotemp_enabled) autotemp_factor = code_value_temp_diff();
    if (code_seen('S')) autotemp_min = code_value_temp_abs();
    if (code_seen('B')) autotemp_max = code_value_temp_abs();
  }

#endif