marlin/Marlin/stepper.cpp

/*
  stepper.c - stepper motor driver: executes motion plans using stepper motors
  Part of Grbl

  Copyright (c) 2009-2011 Simen Svale Skogsrud

  Grbl 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.

  Grbl 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 Grbl.  If not, see <http://www.gnu.org/licenses/>.
*/

/* The timer calculations of this module informed by the 'RepRap cartesian firmware' by Zack Smith
   and Philipp Tiefenbacher. */

#include "Marlin.h"
#include "stepper.h"
#include "planner.h"
#include "temperature.h"
#include "ultralcd.h"
#include "language.h"
#include "cardreader.h"
#include "speed_lookuptable.h"
#if HAS_DIGIPOTSS
  #include <SPI.h>
#endif

//===========================================================================
//============================= public variables ============================
//===========================================================================
block_t *current_block;  // A pointer to the block currently being traced


//===========================================================================
//============================= private variables ===========================
//===========================================================================
//static makes it impossible to be called from outside of this file by extern.!

// Variables used by The Stepper Driver Interrupt
static unsigned char out_bits;        // The next stepping-bits to be output
static unsigned int cleaning_buffer_counter;  

// Counter variables for the bresenham line tracer
static long counter_x, counter_y, counter_z, counter_e;
volatile static unsigned long step_events_completed; // The number of step events executed in the current block

#ifdef ADVANCE
  static long advance_rate, advance, final_advance = 0;
  static long old_advance = 0;
  static long e_steps[4];
#endif

static long acceleration_time, deceleration_time;
//static unsigned long accelerate_until, decelerate_after, acceleration_rate, initial_rate, final_rate, nominal_rate;
static unsigned short acc_step_rate; // needed for deccelaration start point
static char step_loops;
static unsigned short OCR1A_nominal;
static unsigned short step_loops_nominal;

volatile long endstops_trigsteps[3] = { 0 };
volatile long endstops_stepsTotal, endstops_stepsDone;
static volatile bool endstop_x_hit = false;
static volatile bool endstop_y_hit = false;
static volatile bool endstop_z_hit = false;

#ifdef ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED
  bool abort_on_endstop_hit = false;
#endif

#ifdef MOTOR_CURRENT_PWM_XY_PIN
  int motor_current_setting[3] = DEFAULT_PWM_MOTOR_CURRENT;
#endif

static bool old_x_min_endstop = false,
            old_x_max_endstop = false,
            old_y_min_endstop = false,
            old_y_max_endstop = false,
            old_z_min_endstop = false,
            old_z_max_endstop = false;

static bool check_endstops = true;

volatile long count_position[NUM_AXIS] = { 0 };
volatile signed char count_direction[NUM_AXIS] = { 1, 1, 1, 1 };


//===========================================================================
//================================ functions ================================
//===========================================================================

#ifdef DUAL_X_CARRIAGE
  #define X_APPLY_DIR(v,ALWAYS) \
    if (extruder_duplication_enabled || ALWAYS) { \
      X_DIR_WRITE(v); \
      X2_DIR_WRITE(v); \
    } \
    else{ \
      if (current_block->active_extruder) \
        X2_DIR_WRITE(v); \
      else \
        X_DIR_WRITE(v); \
    }
  #define X_APPLY_STEP(v,ALWAYS) \
    if (extruder_duplication_enabled || ALWAYS) { \
      X_STEP_WRITE(v); \
      X2_STEP_WRITE(v); \
    } \
    else { \
      if (current_block->active_extruder != 0) \
        X2_STEP_WRITE(v); \
      else \
        X_STEP_WRITE(v); \
    }
#else
  #define X_APPLY_DIR(v,Q) X_DIR_WRITE(v)
  #define X_APPLY_STEP(v,Q) X_STEP_WRITE(v)
#endif

#ifdef Y_DUAL_STEPPER_DRIVERS
  #define Y_APPLY_DIR(v,Q) Y_DIR_WRITE(v), Y2_DIR_WRITE((v) != INVERT_Y2_VS_Y_DIR)
  #define Y_APPLY_STEP(v,Q) Y_STEP_WRITE(v), Y2_STEP_WRITE(v)
#else
  #define Y_APPLY_DIR(v,Q) Y_DIR_WRITE(v)
  #define Y_APPLY_STEP(v,Q) Y_STEP_WRITE(v)
#endif

#ifdef Z_DUAL_STEPPER_DRIVERS
  #define Z_APPLY_DIR(v,Q) Z_DIR_WRITE(v), Z2_DIR_WRITE(v)
  #define Z_APPLY_STEP(v,Q) Z_STEP_WRITE(v), Z2_STEP_WRITE(v)
#else
  #define Z_APPLY_DIR(v,Q) Z_DIR_WRITE(v)
  #define Z_APPLY_STEP(v,Q) Z_STEP_WRITE(v)
#endif

#define E_APPLY_STEP(v,Q) E_STEP_WRITE(v)

// intRes = intIn1 * intIn2 >> 16
// uses:
// r26 to store 0
// r27 to store the byte 1 of the 24 bit result
#define MultiU16X8toH16(intRes, charIn1, intIn2) \
  asm volatile ( \
    "clr r26 \n\t" \
    "mul %A1, %B2 \n\t" \
    "movw %A0, r0 \n\t" \
    "mul %A1, %A2 \n\t" \
    "add %A0, r1 \n\t" \
    "adc %B0, r26 \n\t" \
    "lsr r0 \n\t" \
    "adc %A0, r26 \n\t" \
    "adc %B0, r26 \n\t" \
    "clr r1 \n\t" \
    : \
    "=&r" (intRes) \
    : \
    "d" (charIn1), \
    "d" (intIn2) \
    : \
    "r26" \
  )

// intRes = longIn1 * longIn2 >> 24
// uses:
// r26 to store 0
// r27 to store the byte 1 of the 48bit result
#define MultiU24X24toH16(intRes, longIn1, longIn2) \
  asm volatile ( \
    "clr r26 \n\t" \
    "mul %A1, %B2 \n\t" \
    "mov r27, r1 \n\t" \
    "mul %B1, %C2 \n\t" \
    "movw %A0, r0 \n\t" \
    "mul %C1, %C2 \n\t" \
    "add %B0, r0 \n\t" \
    "mul %C1, %B2 \n\t" \
    "add %A0, r0 \n\t" \
    "adc %B0, r1 \n\t" \
    "mul %A1, %C2 \n\t" \
    "add r27, r0 \n\t" \
    "adc %A0, r1 \n\t" \
    "adc %B0, r26 \n\t" \
    "mul %B1, %B2 \n\t" \
    "add r27, r0 \n\t" \
    "adc %A0, r1 \n\t" \
    "adc %B0, r26 \n\t" \
    "mul %C1, %A2 \n\t" \
    "add r27, r0 \n\t" \
    "adc %A0, r1 \n\t" \
    "adc %B0, r26 \n\t" \
    "mul %B1, %A2 \n\t" \
    "add r27, r1 \n\t" \
    "adc %A0, r26 \n\t" \
    "adc %B0, r26 \n\t" \
    "lsr r27 \n\t" \
    "adc %A0, r26 \n\t" \
    "adc %B0, r26 \n\t" \
    "clr r1 \n\t" \
    : \
    "=&r" (intRes) \
    : \
    "d" (longIn1), \
    "d" (longIn2) \
    : \
    "r26" , "r27" \
  )

// Some useful constants

#define ENABLE_STEPPER_DRIVER_INTERRUPT()  TIMSK1 |= BIT(OCIE1A)
#define DISABLE_STEPPER_DRIVER_INTERRUPT() TIMSK1 &= ~BIT(OCIE1A)

void endstops_hit_on_purpose() {
  endstop_x_hit = endstop_y_hit = endstop_z_hit = false;
}

void checkHitEndstops() {
  if (endstop_x_hit || endstop_y_hit || endstop_z_hit) {
    SERIAL_ECHO_START;
    SERIAL_ECHOPGM(MSG_ENDSTOPS_HIT);
    if (endstop_x_hit) {
      SERIAL_ECHOPAIR(" X:", (float)endstops_trigsteps[X_AXIS] / axis_steps_per_unit[X_AXIS]);
      LCD_MESSAGEPGM(MSG_ENDSTOPS_HIT "X");
    }
    if (endstop_y_hit) {
      SERIAL_ECHOPAIR(" Y:", (float)endstops_trigsteps[Y_AXIS] / axis_steps_per_unit[Y_AXIS]);
      LCD_MESSAGEPGM(MSG_ENDSTOPS_HIT "Y");
    }
    if (endstop_z_hit) {
      SERIAL_ECHOPAIR(" Z:", (float)endstops_trigsteps[Z_AXIS] / axis_steps_per_unit[Z_AXIS]);
      LCD_MESSAGEPGM(MSG_ENDSTOPS_HIT "Z");
    }
    SERIAL_EOL;

    endstops_hit_on_purpose();

    #if defined(ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED) && defined(SDSUPPORT)
      if (abort_on_endstop_hit) {
        card.sdprinting = false;
        card.closefile();
        quickStop();
        setTargetHotend0(0);
        setTargetHotend1(0);
        setTargetHotend2(0);
        setTargetHotend3(0);
        setTargetBed(0);
      }
    #endif
  }
}

void enable_endstops(bool check) { check_endstops = check; }

//         __________________________
//        /|                        |\     _________________         ^
//       / |                        | \   /|               |\        |
//      /  |                        |  \ / |               | \       s
//     /   |                        |   |  |               |  \      p
//    /    |                        |   |  |               |   \     e
//   +-----+------------------------+---+--+---------------+----+    e
//   |               BLOCK 1            |      BLOCK 2          |    d
//
//                           time ----->
//
//  The trapezoid is the shape the speed curve over time. It starts at block->initial_rate, accelerates
//  first block->accelerate_until step_events_completed, then keeps going at constant speed until
//  step_events_completed reaches block->decelerate_after after which it decelerates until the trapezoid generator is reset.
//  The slope of acceleration is calculated with the leib ramp alghorithm.

void st_wake_up() {
  //  TCNT1 = 0;
  ENABLE_STEPPER_DRIVER_INTERRUPT();
}

FORCE_INLINE unsigned short calc_timer(unsigned short step_rate) {
  unsigned short timer;
  if (step_rate > MAX_STEP_FREQUENCY) step_rate = MAX_STEP_FREQUENCY;

  if (step_rate > 20000) { // If steprate > 20kHz >> step 4 times
    step_rate = (step_rate >> 2) & 0x3fff;
    step_loops = 4;
  }
  else if (step_rate > 10000) { // If steprate > 10kHz >> step 2 times
    step_rate = (step_rate >> 1) & 0x7fff;
    step_loops = 2;
  }
  else {
    step_loops = 1;
  }

  if (step_rate < (F_CPU / 500000)) step_rate = (F_CPU / 500000);
  step_rate -= (F_CPU / 500000); // Correct for minimal speed
  if (step_rate >= (8 * 256)) { // higher step rate
    unsigned short table_address = (unsigned short)&speed_lookuptable_fast[(unsigned char)(step_rate>>8)][0];
    unsigned char tmp_step_rate = (step_rate & 0x00ff);
    unsigned short gain = (unsigned short)pgm_read_word_near(table_address+2);
    MultiU16X8toH16(timer, tmp_step_rate, gain);
    timer = (unsigned short)pgm_read_word_near(table_address) - timer;
  }
  else { // lower step rates
    unsigned short table_address = (unsigned short)&speed_lookuptable_slow[0][0];
    table_address += ((step_rate)>>1) & 0xfffc;
    timer = (unsigned short)pgm_read_word_near(table_address);
    timer -= (((unsigned short)pgm_read_word_near(table_address+2) * (unsigned char)(step_rate & 0x0007))>>3);
  }
  if (timer < 100) { timer = 100; MYSERIAL.print(MSG_STEPPER_TOO_HIGH); MYSERIAL.println(step_rate); }//(20kHz this should never happen)
  return timer;
}

// Initializes the trapezoid generator from the current block. Called whenever a new
// block begins.
FORCE_INLINE void trapezoid_generator_reset() {
  #ifdef ADVANCE
    advance = current_block->initial_advance;
    final_advance = current_block->final_advance;
    // Do E steps + advance steps
    e_steps[current_block->active_extruder] += ((advance >>8) - old_advance);
    old_advance = advance >>8;
  #endif
  deceleration_time = 0;
  // step_rate to timer interval
  OCR1A_nominal = calc_timer(current_block->nominal_rate);
  // make a note of the number of step loops required at nominal speed
  step_loops_nominal = step_loops;
  acc_step_rate = current_block->initial_rate;
  acceleration_time = calc_timer(acc_step_rate);
  OCR1A = acceleration_time;

  // SERIAL_ECHO_START;
  // SERIAL_ECHOPGM("advance :");
  // SERIAL_ECHO(current_block->advance/256.0);
  // SERIAL_ECHOPGM("advance rate :");
  // SERIAL_ECHO(current_block->advance_rate/256.0);
  // SERIAL_ECHOPGM("initial advance :");
  // SERIAL_ECHO(current_block->initial_advance/256.0);
  // SERIAL_ECHOPGM("final advance :");
  // SERIAL_ECHOLN(current_block->final_advance/256.0);
}

// "The Stepper Driver Interrupt" - This timer interrupt is the workhorse.
// It pops blocks from the block_buffer and executes them by pulsing the stepper pins appropriately.
ISR(TIMER1_COMPA_vect) {

  if(cleaning_buffer_counter)
  {
    current_block = NULL;
    plan_discard_current_block();
    if ((cleaning_buffer_counter == 1) && (SD_FINISHED_STEPPERRELEASE)) enquecommands_P(PSTR(SD_FINISHED_RELEASECOMMAND));
    cleaning_buffer_counter--;
    OCR1A = 200;
    return;
  }
  
  // If there is no current block, attempt to pop one from the buffer
  if (!current_block) {
    // Anything in the buffer?
    current_block = plan_get_current_block();
    if (current_block) {
      current_block->busy = true;
      trapezoid_generator_reset();
      counter_x = -(current_block->step_event_count >> 1);
      counter_y = counter_z = counter_e = counter_x;
      step_events_completed = 0;

      #ifdef Z_LATE_ENABLE
        if (current_block->steps[Z_AXIS] > 0) {
          enable_z();
          OCR1A = 2000; //1ms wait
          return;
        }
      #endif

      // #ifdef ADVANCE
      //   e_steps[current_block->active_extruder] = 0;
      // #endif
    }
    else {
      OCR1A = 2000; // 1kHz.
    }
  }

  if (current_block != NULL) {
    // Set directions TO DO This should be done once during init of trapezoid. Endstops -> interrupt
    out_bits = current_block->direction_bits;

    // Set the direction bits (X_AXIS=A_AXIS and Y_AXIS=B_AXIS for COREXY)
    if (TEST(out_bits, X_AXIS)) {
      X_APPLY_DIR(INVERT_X_DIR,0);
      count_direction[X_AXIS] = -1;
    }
    else {
      X_APPLY_DIR(!INVERT_X_DIR,0);
      count_direction[X_AXIS] = 1;
    }

    if (TEST(out_bits, Y_AXIS)) {
      Y_APPLY_DIR(INVERT_Y_DIR,0);
      count_direction[Y_AXIS] = -1;
    }
    else {
      Y_APPLY_DIR(!INVERT_Y_DIR,0);
      count_direction[Y_AXIS] = 1;
    }

    #define UPDATE_ENDSTOP(axis,AXIS,minmax,MINMAX) \
      bool axis ##_## minmax ##_endstop = (READ(AXIS ##_## MINMAX ##_PIN) != AXIS ##_## MINMAX ##_ENDSTOP_INVERTING); \
      if (axis ##_## minmax ##_endstop && old_## axis ##_## minmax ##_endstop && (current_block->steps[AXIS ##_AXIS] > 0)) { \
        endstops_trigsteps[AXIS ##_AXIS] = count_position[AXIS ##_AXIS]; \
        endstop_## axis ##_hit = true; \
        step_events_completed = current_block->step_event_count; \
      } \
      old_## axis ##_## minmax ##_endstop = axis ##_## minmax ##_endstop;

    // Check X and Y endstops
    if (check_endstops) {
      #ifdef COREXY
        // Head direction in -X axis for CoreXY bots.
        // If DeltaX == -DeltaY, the movement is only in Y axis
        if (current_block->steps[A_AXIS] != current_block->steps[B_AXIS] || (TEST(out_bits, A_AXIS) == TEST(out_bits, B_AXIS)))
          if (TEST(out_bits, X_HEAD))
      #else
          if (TEST(out_bits, X_AXIS))   // stepping along -X axis (regular cartesians bot)
      #endif
          { // -direction
            #ifdef DUAL_X_CARRIAGE
              // with 2 x-carriages, endstops are only checked in the homing direction for the active extruder
              if ((current_block->active_extruder == 0 && X_HOME_DIR == -1) || (current_block->active_extruder != 0 && X2_HOME_DIR == -1))
            #endif          
              {
                #if defined(X_MIN_PIN) && X_MIN_PIN >= 0
                  UPDATE_ENDSTOP(x, X, min, MIN);
                #endif
              }
          }
          else { // +direction
            #ifdef DUAL_X_CARRIAGE
              // with 2 x-carriages, endstops are only checked in the homing direction for the active extruder
              if ((current_block->active_extruder == 0 && X_HOME_DIR == 1) || (current_block->active_extruder != 0 && X2_HOME_DIR == 1))
            #endif
              {
                #if defined(X_MAX_PIN) && X_MAX_PIN >= 0
                  UPDATE_ENDSTOP(x, X, max, MAX);
                #endif
              }
          }
      #ifdef COREXY
        // Head direction in -Y axis for CoreXY bots.
        // If DeltaX == DeltaY, the movement is only in X axis
        if (current_block->steps[A_AXIS] != current_block->steps[B_AXIS] || (TEST(out_bits, A_AXIS) != TEST(out_bits, B_AXIS)))
          if (TEST(out_bits, Y_HEAD))
      #else
          if (TEST(out_bits, Y_AXIS))   // -direction
      #endif
          { // -direction
            #if defined(Y_MIN_PIN) && Y_MIN_PIN >= 0
              UPDATE_ENDSTOP(y, Y, min, MIN);
            #endif
          }
          else { // +direction
            #if defined(Y_MAX_PIN) && Y_MAX_PIN >= 0
              UPDATE_ENDSTOP(y, Y, max, MAX);
            #endif
          }
    }

    if (TEST(out_bits, Z_AXIS)) {   // -direction
      Z_DIR_WRITE(INVERT_Z_DIR);
      #ifdef Z_DUAL_STEPPER_DRIVERS
        Z2_DIR_WRITE(INVERT_Z_DIR);
      #endif

      count_direction[Z_AXIS] = -1;
      if (check_endstops) {
        #if defined(Z_MIN_PIN) && Z_MIN_PIN >= 0
          UPDATE_ENDSTOP(z, Z, min, MIN);
        #endif
      }
    }
    else { // +direction
      Z_DIR_WRITE(!INVERT_Z_DIR);
      #ifdef Z_DUAL_STEPPER_DRIVERS
        Z2_DIR_WRITE(!INVERT_Z_DIR);
      #endif

      count_direction[Z_AXIS] = 1;
      if (check_endstops) {
        #if defined(Z_MAX_PIN) && Z_MAX_PIN >= 0
          UPDATE_ENDSTOP(z, Z, max, MAX);
        #endif
      }
    }

    #ifndef ADVANCE
      if (TEST(out_bits, E_AXIS)) {  // -direction
        REV_E_DIR();
        count_direction[E_AXIS]=-1;
      }
      else { // +direction
        NORM_E_DIR();
        count_direction[E_AXIS]=1;
      }
    #endif //!ADVANCE

    // Take multiple steps per interrupt (For high speed moves)
    for (int8_t i=0; i < step_loops; i++) {
      #ifndef AT90USB
        MSerial.checkRx(); // Check for serial chars.
      #endif

      #ifdef ADVANCE
        counter_e += current_block->steps[E_AXIS];
        if (counter_e > 0) {
          counter_e -= current_block->step_event_count;
          e_steps[current_block->active_extruder] += TEST(out_bits, E_AXIS) ? -1 : 1;
        }
      #endif //ADVANCE

      #ifdef CONFIG_STEPPERS_TOSHIBA
        /**
         * The Toshiba stepper controller require much longer pulses.
         * So we 'stage' decompose the pulses between high and low
         * instead of doing each in turn. The extra tests add enough
         * lag to allow it work with without needing NOPs
         */
        #define STEP_ADD(axis, AXIS) \
         counter_## axis += current_block->steps[AXIS ##_AXIS]; \
         if (counter_## axis > 0) { AXIS ##_STEP_WRITE(HIGH); }
        STEP_ADD(x,X);
        STEP_ADD(y,Y);
        STEP_ADD(z,Z);
        #ifndef ADVANCE
          STEP_ADD(e,E);
        #endif

        #define STEP_IF_COUNTER(axis, AXIS) \
          if (counter_## axis > 0) { \
            counter_## axis -= current_block->step_event_count; \
            count_position[AXIS ##_AXIS] += count_direction[AXIS ##_AXIS]; \
            AXIS ##_STEP_WRITE(LOW); \
          }

        STEP_IF_COUNTER(x, X);
        STEP_IF_COUNTER(y, Y);
        STEP_IF_COUNTER(z, Z);
        #ifndef ADVANCE
          STEP_IF_COUNTER(e, E);
        #endif

      #else // !CONFIG_STEPPERS_TOSHIBA

        #define APPLY_MOVEMENT(axis, AXIS) \
          counter_## axis += current_block->steps[AXIS ##_AXIS]; \
          if (counter_## axis > 0) { \
            AXIS ##_APPLY_STEP(!INVERT_## AXIS ##_STEP_PIN,0); \
            counter_## axis -= current_block->step_event_count; \
            count_position[AXIS ##_AXIS] += count_direction[AXIS ##_AXIS]; \
            AXIS ##_APPLY_STEP(INVERT_## AXIS ##_STEP_PIN,0); \
          }

        APPLY_MOVEMENT(x, X);
        APPLY_MOVEMENT(y, Y);
        APPLY_MOVEMENT(z, Z);
        #ifndef ADVANCE
          APPLY_MOVEMENT(e, E);
        #endif

      #endif // CONFIG_STEPPERS_TOSHIBA
      step_events_completed++;
      if (step_events_completed >= current_block->step_event_count) break;
    }
    // Calculare new timer value
    unsigned short timer;
    unsigned short step_rate;
    if (step_events_completed <= (unsigned long int)current_block->accelerate_until) {

      MultiU24X24toH16(acc_step_rate, acceleration_time, current_block->acceleration_rate);
      acc_step_rate += current_block->initial_rate;

      // upper limit
      if (acc_step_rate > current_block->nominal_rate)
        acc_step_rate = current_block->nominal_rate;

      // step_rate to timer interval
      timer = calc_timer(acc_step_rate);
      OCR1A = timer;
      acceleration_time += timer;
      #ifdef ADVANCE
        for(int8_t i=0; i < step_loops; i++) {
          advance += advance_rate;
        }
        //if (advance > current_block->advance) advance = current_block->advance;
        // Do E steps + advance steps
        e_steps[current_block->active_extruder] += ((advance >>8) - old_advance);
        old_advance = advance >>8;

      #endif
    }
    else if (step_events_completed > (unsigned long int)current_block->decelerate_after) {
      MultiU24X24toH16(step_rate, deceleration_time, current_block->acceleration_rate);

      if (step_rate > acc_step_rate) { // Check step_rate stays positive
        step_rate = current_block->final_rate;
      }
      else {
        step_rate = acc_step_rate - step_rate; // Decelerate from aceleration end point.
      }

      // lower limit
      if (step_rate < current_block->final_rate)
        step_rate = current_block->final_rate;

      // step_rate to timer interval
      timer = calc_timer(step_rate);
      OCR1A = timer;
      deceleration_time += timer;
      #ifdef ADVANCE
        for(int8_t i=0; i < step_loops; i++) {
          advance -= advance_rate;
        }
        if (advance < final_advance) advance = final_advance;
        // Do E steps + advance steps
        e_steps[current_block->active_extruder] += ((advance >>8) - old_advance);
        old_advance = advance >>8;
      #endif //ADVANCE
    }
    else {
      OCR1A = OCR1A_nominal;
      // ensure we're running at the correct step rate, even if we just came off an acceleration
      step_loops = step_loops_nominal;
    }

    // If current block is finished, reset pointer
    if (step_events_completed >= current_block->step_event_count) {
      current_block = NULL;
      plan_discard_current_block();
    }
  }
}

#ifdef ADVANCE
  unsigned char old_OCR0A;
  // Timer interrupt for E. e_steps is set in the main routine;
  // Timer 0 is shared with millies
  ISR(TIMER0_COMPA_vect)
  {
    old_OCR0A += 52; // ~10kHz interrupt (250000 / 26 = 9615kHz)
    OCR0A = old_OCR0A;
    // Set E direction (Depends on E direction + advance)
    for(unsigned char i=0; i<4;i++) {
      if (e_steps[0] != 0) {
        E0_STEP_WRITE(INVERT_E_STEP_PIN);
        if (e_steps[0] < 0) {
          E0_DIR_WRITE(INVERT_E0_DIR);
          e_steps[0]++;
          E0_STEP_WRITE(!INVERT_E_STEP_PIN);
        }
        else if (e_steps[0] > 0) {
          E0_DIR_WRITE(!INVERT_E0_DIR);
          e_steps[0]--;
          E0_STEP_WRITE(!INVERT_E_STEP_PIN);
        }
      }
 #if EXTRUDERS > 1
      if (e_steps[1] != 0) {
        E1_STEP_WRITE(INVERT_E_STEP_PIN);
        if (e_steps[1] < 0) {
          E1_DIR_WRITE(INVERT_E1_DIR);
          e_steps[1]++;
          E1_STEP_WRITE(!INVERT_E_STEP_PIN);
        }
        else if (e_steps[1] > 0) {
          E1_DIR_WRITE(!INVERT_E1_DIR);
          e_steps[1]--;
          E1_STEP_WRITE(!INVERT_E_STEP_PIN);
        }
      }
 #endif
 #if EXTRUDERS > 2
      if (e_steps[2] != 0) {
        E2_STEP_WRITE(INVERT_E_STEP_PIN);
        if (e_steps[2] < 0) {
          E2_DIR_WRITE(INVERT_E2_DIR);
          e_steps[2]++;
          E2_STEP_WRITE(!INVERT_E_STEP_PIN);
        }
        else if (e_steps[2] > 0) {
          E2_DIR_WRITE(!INVERT_E2_DIR);
          e_steps[2]--;
          E2_STEP_WRITE(!INVERT_E_STEP_PIN);
        }
      }
 #endif
 #if EXTRUDERS > 3
      if (e_steps[3] != 0) {
        E3_STEP_WRITE(INVERT_E_STEP_PIN);
        if (e_steps[3] < 0) {
          E3_DIR_WRITE(INVERT_E3_DIR);
          e_steps[3]++;
          E3_STEP_WRITE(!INVERT_E_STEP_PIN);
        }
        else if (e_steps[3] > 0) {
          E3_DIR_WRITE(!INVERT_E3_DIR);
          e_steps[3]--;
          E3_STEP_WRITE(!INVERT_E_STEP_PIN);
        }
      }
 #endif

    }
  }
#endif // ADVANCE

void st_init() {
  digipot_init(); //Initialize Digipot Motor Current
  microstep_init(); //Initialize Microstepping Pins

  // initialise TMC Steppers
  #ifdef HAVE_TMCDRIVER
    tmc_init();
  #endif
    // initialise L6470 Steppers
  #ifdef HAVE_L6470DRIVER
    L6470_init();
  #endif
  
  // Initialize Dir Pins
  #if defined(X_DIR_PIN) && X_DIR_PIN >= 0
    X_DIR_INIT;
  #endif
  #if defined(X2_DIR_PIN) && X2_DIR_PIN >= 0
    X2_DIR_INIT;
  #endif
  #if defined(Y_DIR_PIN) && Y_DIR_PIN >= 0
    Y_DIR_INIT;
    #if defined(Y_DUAL_STEPPER_DRIVERS) && defined(Y2_DIR_PIN) && Y2_DIR_PIN >= 0
      Y2_DIR_INIT;
    #endif
  #endif
  #if defined(Z_DIR_PIN) && Z_DIR_PIN >= 0
    Z_DIR_INIT;
    #if defined(Z_DUAL_STEPPER_DRIVERS) && defined(Z2_DIR_PIN) && Z2_DIR_PIN >= 0
      Z2_DIR_INIT;
    #endif
  #endif
  #if defined(E0_DIR_PIN) && E0_DIR_PIN >= 0
    E0_DIR_INIT;
  #endif
  #if defined(E1_DIR_PIN) && E1_DIR_PIN >= 0
    E1_DIR_INIT;
  #endif
  #if defined(E2_DIR_PIN) && E2_DIR_PIN >= 0
    E2_DIR_INIT;
  #endif
  #if defined(E3_DIR_PIN) && E3_DIR_PIN >= 0
    E3_DIR_INIT;
  #endif

  //Initialize Enable Pins - steppers default to disabled.

  #if defined(X_ENABLE_PIN) && X_ENABLE_PIN >= 0
    X_ENABLE_INIT;
    if (!X_ENABLE_ON) X_ENABLE_WRITE(HIGH);
  #endif
  #if defined(X2_ENABLE_PIN) && X2_ENABLE_PIN >= 0
    X2_ENABLE_INIT;
    if (!X_ENABLE_ON) X2_ENABLE_WRITE(HIGH);
  #endif
  #if defined(Y_ENABLE_PIN) && Y_ENABLE_PIN >= 0
    Y_ENABLE_INIT;
    if (!Y_ENABLE_ON) Y_ENABLE_WRITE(HIGH);
	
	#if defined(Y_DUAL_STEPPER_DRIVERS) && defined(Y2_ENABLE_PIN) && Y2_ENABLE_PIN >= 0
	  Y2_ENABLE_INIT;
	  if (!Y_ENABLE_ON) Y2_ENABLE_WRITE(HIGH);
	#endif
  #endif
  #if defined(Z_ENABLE_PIN) && Z_ENABLE_PIN >= 0
    Z_ENABLE_INIT;
    if (!Z_ENABLE_ON) Z_ENABLE_WRITE(HIGH);

    #if defined(Z_DUAL_STEPPER_DRIVERS) && defined(Z2_ENABLE_PIN) && Z2_ENABLE_PIN >= 0
      Z2_ENABLE_INIT;
      if (!Z_ENABLE_ON) Z2_ENABLE_WRITE(HIGH);
    #endif
  #endif
  #if defined(E0_ENABLE_PIN) && E0_ENABLE_PIN >= 0
    E0_ENABLE_INIT;
    if (!E_ENABLE_ON) E0_ENABLE_WRITE(HIGH);
  #endif
  #if defined(E1_ENABLE_PIN) && E1_ENABLE_PIN >= 0
    E1_ENABLE_INIT;
    if (!E_ENABLE_ON) E1_ENABLE_WRITE(HIGH);
  #endif
  #if defined(E2_ENABLE_PIN) && E2_ENABLE_PIN >= 0
    E2_ENABLE_INIT;
    if (!E_ENABLE_ON) E2_ENABLE_WRITE(HIGH);
  #endif
  #if defined(E3_ENABLE_PIN) && E3_ENABLE_PIN >= 0
    E3_ENABLE_INIT;
    if (!E_ENABLE_ON) E3_ENABLE_WRITE(HIGH);
  #endif

  //endstops and pullups

  #if defined(X_MIN_PIN) && X_MIN_PIN >= 0
    SET_INPUT(X_MIN_PIN);
    #ifdef ENDSTOPPULLUP_XMIN
      WRITE(X_MIN_PIN,HIGH);
    #endif
  #endif

  #if defined(Y_MIN_PIN) && Y_MIN_PIN >= 0
    SET_INPUT(Y_MIN_PIN);
    #ifdef ENDSTOPPULLUP_YMIN
      WRITE(Y_MIN_PIN,HIGH);
    #endif
  #endif

  #if defined(Z_MIN_PIN) && Z_MIN_PIN >= 0
    SET_INPUT(Z_MIN_PIN);
    #ifdef ENDSTOPPULLUP_ZMIN
      WRITE(Z_MIN_PIN,HIGH);
    #endif
  #endif

  #if defined(X_MAX_PIN) && X_MAX_PIN >= 0
    SET_INPUT(X_MAX_PIN);
    #ifdef ENDSTOPPULLUP_XMAX
      WRITE(X_MAX_PIN,HIGH);
    #endif
  #endif

  #if defined(Y_MAX_PIN) && Y_MAX_PIN >= 0
    SET_INPUT(Y_MAX_PIN);
    #ifdef ENDSTOPPULLUP_YMAX
      WRITE(Y_MAX_PIN,HIGH);
    #endif
  #endif

  #if defined(Z_MAX_PIN) && Z_MAX_PIN >= 0
    SET_INPUT(Z_MAX_PIN);
    #ifdef ENDSTOPPULLUP_ZMAX
      WRITE(Z_MAX_PIN,HIGH);
    #endif
  #endif

  #define AXIS_INIT(axis, AXIS, PIN) \
    AXIS ##_STEP_INIT; \
    AXIS ##_STEP_WRITE(INVERT_## PIN ##_STEP_PIN); \
    disable_## axis()

  #define E_AXIS_INIT(NUM) AXIS_INIT(e## NUM, E## NUM, E)

  // Initialize Step Pins
  #if defined(X_STEP_PIN) && X_STEP_PIN >= 0
    AXIS_INIT(x, X, X);
  #endif
  #if defined(X2_STEP_PIN) && X2_STEP_PIN >= 0
    AXIS_INIT(x, X2, X);
  #endif
  #if defined(Y_STEP_PIN) && Y_STEP_PIN >= 0
    #if defined(Y_DUAL_STEPPER_DRIVERS) && defined(Y2_STEP_PIN) && Y2_STEP_PIN >= 0
      Y2_STEP_INIT;
      Y2_STEP_WRITE(INVERT_Y_STEP_PIN);
    #endif
    AXIS_INIT(y, Y, Y);
  #endif
  #if defined(Z_STEP_PIN) && Z_STEP_PIN >= 0
    #if defined(Z_DUAL_STEPPER_DRIVERS) && defined(Z2_STEP_PIN) && Z2_STEP_PIN >= 0
      Z2_STEP_INIT;
      Z2_STEP_WRITE(INVERT_Z_STEP_PIN);
    #endif
    AXIS_INIT(z, Z, Z);
  #endif
  #if defined(E0_STEP_PIN) && E0_STEP_PIN >= 0
    E_AXIS_INIT(0);
  #endif
  #if defined(E1_STEP_PIN) && E1_STEP_PIN >= 0
    E_AXIS_INIT(1);
  #endif
  #if defined(E2_STEP_PIN) && E2_STEP_PIN >= 0
    E_AXIS_INIT(2);
  #endif
  #if defined(E3_STEP_PIN) && E3_STEP_PIN >= 0
    E_AXIS_INIT(3);
  #endif

  // waveform generation = 0100 = CTC
  TCCR1B &= ~BIT(WGM13);
  TCCR1B |=  BIT(WGM12);
  TCCR1A &= ~BIT(WGM11);
  TCCR1A &= ~BIT(WGM10);

  // output mode = 00 (disconnected)
  TCCR1A &= ~(3<<COM1A0);
  TCCR1A &= ~(3<<COM1B0);

  // Set the timer pre-scaler
  // Generally we use a divider of 8, resulting in a 2MHz timer
  // frequency on a 16MHz MCU. If you are going to change this, be
  // sure to regenerate speed_lookuptable.h with
  // create_speed_lookuptable.py
  TCCR1B = (TCCR1B & ~(0x07<<CS10)) | (2<<CS10);

  OCR1A = 0x4000;
  TCNT1 = 0;
  ENABLE_STEPPER_DRIVER_INTERRUPT();

  #ifdef ADVANCE
    #if defined(TCCR0A) && defined(WGM01)
      TCCR0A &= ~BIT(WGM01);
      TCCR0A &= ~BIT(WGM00);
    #endif
    e_steps[0] = 0;
    e_steps[1] = 0;
    e_steps[2] = 0;
    e_steps[3] = 0;
    TIMSK0 |= BIT(OCIE0A);
  #endif //ADVANCE

  enable_endstops(true); // Start with endstops active. After homing they can be disabled
  sei();
}


// Block until all buffered steps are executed
void st_synchronize() {
  while (blocks_queued()) {
    manage_heater();
    manage_inactivity();
    lcd_update();
  }
}

void st_set_position(const long &x, const long &y, const long &z, const long &e) {
  CRITICAL_SECTION_START;
  count_position[X_AXIS] = x;
  count_position[Y_AXIS] = y;
  count_position[Z_AXIS] = z;
  count_position[E_AXIS] = e;
  CRITICAL_SECTION_END;
}

void st_set_e_position(const long &e) {
  CRITICAL_SECTION_START;
  count_position[E_AXIS] = e;
  CRITICAL_SECTION_END;
}

long st_get_position(uint8_t axis) {
  long count_pos;
  CRITICAL_SECTION_START;
  count_pos = count_position[axis];
  CRITICAL_SECTION_END;
  return count_pos;
}

#ifdef ENABLE_AUTO_BED_LEVELING

  float st_get_position_mm(uint8_t axis) {
    float steper_position_in_steps = st_get_position(axis);
    return steper_position_in_steps / axis_steps_per_unit[axis];
  }

#endif  // ENABLE_AUTO_BED_LEVELING

void finishAndDisableSteppers() {
  st_synchronize();
  disable_x();
  disable_y();
  disable_z();
  disable_e0();
  disable_e1();
  disable_e2();
  disable_e3();
}

void quickStop() {
  cleaning_buffer_counter = 5000;
  DISABLE_STEPPER_DRIVER_INTERRUPT();
  while (blocks_queued()) plan_discard_current_block();
  current_block = NULL;
  ENABLE_STEPPER_DRIVER_INTERRUPT();
}

#ifdef BABYSTEPPING

  // MUST ONLY BE CALLED BY AN ISR,
  // No other ISR should ever interrupt this!
  void babystep(const uint8_t axis, const bool direction) {

    #define BABYSTEP_AXIS(axis, AXIS, INVERT) { \
        enable_## axis(); \
        uint8_t old_pin = AXIS ##_DIR_READ; \
        AXIS ##_APPLY_DIR(INVERT_## AXIS ##_DIR^direction^INVERT, true); \
        AXIS ##_APPLY_STEP(!INVERT_## AXIS ##_STEP_PIN, true); \
        _delay_us(1U); \
        AXIS ##_APPLY_STEP(INVERT_## AXIS ##_STEP_PIN, true); \
        AXIS ##_APPLY_DIR(old_pin, true); \
      }

    switch(axis) {

      case X_AXIS:
        BABYSTEP_AXIS(x, X, false);
        break;

      case Y_AXIS:
        BABYSTEP_AXIS(y, Y, false);
        break;
     
      case Z_AXIS: {

        #ifndef DELTA

          BABYSTEP_AXIS(z, Z, BABYSTEP_INVERT_Z);

        #else // DELTA

          bool z_direction = direction ^ BABYSTEP_INVERT_Z;

          enable_x();
          enable_y();
          enable_z();
          uint8_t old_x_dir_pin = X_DIR_READ,
                  old_y_dir_pin = Y_DIR_READ,
                  old_z_dir_pin = Z_DIR_READ;
          //setup new step
          X_DIR_WRITE(INVERT_X_DIR^z_direction);
          Y_DIR_WRITE(INVERT_Y_DIR^z_direction);
          Z_DIR_WRITE(INVERT_Z_DIR^z_direction);
          //perform step 
          X_STEP_WRITE(!INVERT_X_STEP_PIN);
          Y_STEP_WRITE(!INVERT_Y_STEP_PIN);
          Z_STEP_WRITE(!INVERT_Z_STEP_PIN);
          _delay_us(1U);
          X_STEP_WRITE(INVERT_X_STEP_PIN); 
          Y_STEP_WRITE(INVERT_Y_STEP_PIN); 
          Z_STEP_WRITE(INVERT_Z_STEP_PIN);
          //get old pin state back.
          X_DIR_WRITE(old_x_dir_pin);
          Y_DIR_WRITE(old_y_dir_pin);
          Z_DIR_WRITE(old_z_dir_pin);

        #endif

      } break;
     
      default: break;
    }
  }

#endif //BABYSTEPPING

// From Arduino DigitalPotControl example
void digitalPotWrite(int address, int value) {
  #if HAS_DIGIPOTSS
    digitalWrite(DIGIPOTSS_PIN,LOW); // take the SS pin low to select the chip
    SPI.transfer(address); //  send in the address and value via SPI:
    SPI.transfer(value);
    digitalWrite(DIGIPOTSS_PIN,HIGH); // take the SS pin high to de-select the chip:
    //delay(10);
  #endif
}

// Initialize Digipot Motor Current
void digipot_init() {
  #if HAS_DIGIPOTSS
    const uint8_t digipot_motor_current[] = DIGIPOT_MOTOR_CURRENT;

    SPI.begin();
    pinMode(DIGIPOTSS_PIN, OUTPUT);
    for (int i = 0; i <= 4; i++) {
      //digitalPotWrite(digipot_ch[i], digipot_motor_current[i]);
      digipot_current(i,digipot_motor_current[i]);
    }
  #endif
  #ifdef MOTOR_CURRENT_PWM_XY_PIN
    pinMode(MOTOR_CURRENT_PWM_XY_PIN, OUTPUT);
    pinMode(MOTOR_CURRENT_PWM_Z_PIN, OUTPUT);
    pinMode(MOTOR_CURRENT_PWM_E_PIN, OUTPUT);
    digipot_current(0, motor_current_setting[0]);
    digipot_current(1, motor_current_setting[1]);
    digipot_current(2, motor_current_setting[2]);
    //Set timer5 to 31khz so the PWM of the motor power is as constant as possible. (removes a buzzing noise)
    TCCR5B = (TCCR5B & ~(_BV(CS50) | _BV(CS51) | _BV(CS52))) | _BV(CS50);
  #endif
}

void digipot_current(uint8_t driver, int current) {
  #if HAS_DIGIPOTSS
    const uint8_t digipot_ch[] = DIGIPOT_CHANNELS;
    digitalPotWrite(digipot_ch[driver], current);
  #endif
  #ifdef MOTOR_CURRENT_PWM_XY_PIN
    switch(driver) {
      case 0: analogWrite(MOTOR_CURRENT_PWM_XY_PIN, 255L * current / MOTOR_CURRENT_PWM_RANGE); break;
      case 1: analogWrite(MOTOR_CURRENT_PWM_Z_PIN, 255L * current / MOTOR_CURRENT_PWM_RANGE); break;
      case 2: analogWrite(MOTOR_CURRENT_PWM_E_PIN, 255L * current / MOTOR_CURRENT_PWM_RANGE); break;
    }
  #endif
}

void microstep_init() {
  const uint8_t microstep_modes[] = MICROSTEP_MODES;

  #if defined(E1_MS1_PIN) && E1_MS1_PIN >= 0
    pinMode(E1_MS1_PIN,OUTPUT);
    pinMode(E1_MS2_PIN,OUTPUT); 
  #endif

  #if defined(X_MS1_PIN) && X_MS1_PIN >= 0
    pinMode(X_MS1_PIN,OUTPUT);
    pinMode(X_MS2_PIN,OUTPUT);  
    pinMode(Y_MS1_PIN,OUTPUT);
    pinMode(Y_MS2_PIN,OUTPUT);
    pinMode(Z_MS1_PIN,OUTPUT);
    pinMode(Z_MS2_PIN,OUTPUT);
    pinMode(E0_MS1_PIN,OUTPUT);
    pinMode(E0_MS2_PIN,OUTPUT);
    for (int i = 0; i <= 4; i++) microstep_mode(i, microstep_modes[i]);
  #endif
}

void microstep_ms(uint8_t driver, int8_t ms1, int8_t ms2) {
  if (ms1 >= 0) switch(driver) {
    case 0: digitalWrite(X_MS1_PIN, ms1); break;
    case 1: digitalWrite(Y_MS1_PIN, ms1); break;
    case 2: digitalWrite(Z_MS1_PIN, ms1); break;
    case 3: digitalWrite(E0_MS1_PIN, ms1); break;
    #if defined(E1_MS1_PIN) && E1_MS1_PIN >= 0
      case 4: digitalWrite(E1_MS1_PIN, ms1); break;
    #endif
  }
  if (ms2 >= 0) switch(driver) {
    case 0: digitalWrite(X_MS2_PIN, ms2); break;
    case 1: digitalWrite(Y_MS2_PIN, ms2); break;
    case 2: digitalWrite(Z_MS2_PIN, ms2); break;
    case 3: digitalWrite(E0_MS2_PIN, ms2); break;
    #if defined(E1_MS2_PIN) && E1_MS2_PIN >= 0
      case 4: digitalWrite(E1_MS2_PIN, ms2); break;
    #endif
  }
}

void microstep_mode(uint8_t driver, uint8_t stepping_mode) {
  switch(stepping_mode) {
    case 1: microstep_ms(driver,MICROSTEP1); break;
    case 2: microstep_ms(driver,MICROSTEP2); break;
    case 4: microstep_ms(driver,MICROSTEP4); break;
    case 8: microstep_ms(driver,MICROSTEP8); break;
    case 16: microstep_ms(driver,MICROSTEP16); break;
  }
}

void microstep_readings() {
  SERIAL_PROTOCOLPGM("MS1,MS2 Pins\n");
  SERIAL_PROTOCOLPGM("X: ");
  SERIAL_PROTOCOL(digitalRead(X_MS1_PIN));
  SERIAL_PROTOCOLLN(digitalRead(X_MS2_PIN));
  SERIAL_PROTOCOLPGM("Y: ");
  SERIAL_PROTOCOL(digitalRead(Y_MS1_PIN));
  SERIAL_PROTOCOLLN(digitalRead(Y_MS2_PIN));
  SERIAL_PROTOCOLPGM("Z: ");
  SERIAL_PROTOCOL(digitalRead(Z_MS1_PIN));
  SERIAL_PROTOCOLLN(digitalRead(Z_MS2_PIN));
  SERIAL_PROTOCOLPGM("E0: ");
  SERIAL_PROTOCOL(digitalRead(E0_MS1_PIN));
  SERIAL_PROTOCOLLN(digitalRead(E0_MS2_PIN));
  #if defined(E1_MS1_PIN) && E1_MS1_PIN >= 0
    SERIAL_PROTOCOLPGM("E1: ");
    SERIAL_PROTOCOL(digitalRead(E1_MS1_PIN));
    SERIAL_PROTOCOLLN(digitalRead(E1_MS2_PIN));
  #endif
}