/*
 Reprap firmware based on Sprinter
 Optimize for Sanguinololu 1.2 and above, RAMPS 
 
 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/>. */

/*
  This firmware is a mashup between Sprinter,grbl and parts from marlin.
  (https://github.com/kliment/Sprinter)
  
  Changes by Doppler Michael (midopple)
  
  Planner is from Simen Svale Skogsrud
  https://github.com/simen/grbl

  Parts of Marlin Firmware from ErikZalm
  https://github.com/ErikZalm/Marlin-non-gen6
  
  Sprinter Changelog
  -  Look forward function --> calculate 16 Steps forward, get from Firmaware Marlin and Grbl
  -  Stepper control with Timer 1 (Interrupt)
  -  Extruder heating with PID use a Softpwm (Timer 2) with 500 hz to free Timer1 für Steppercontrol
  -  command M220 Sxxx --> tune Printing speed online (+/- 50 %)
  -  G2 / G3 command --> circle funktion
  -  Baudrate set to 250 kbaud
  -  Testet on Sanguinololu Board
  -  M30 Command can delete files on SD Card
  -  move string to flash to free RAM vor forward planner
  -  M203 Temperature monitor for Repetier

 Version 1.3.04T
  - Implement Plannercode from Marlin V1 big thanks to Erik
  - Stepper interrupt with Step loops
  - Stepperfrequenz 30 Khz
  - New Command
    * M202 - Set maximum feedrate that your machine can sustain (M203 X200 Y200 Z300 E10000) in mm/sec
    * M204 - Set default acceleration: S normal moves T filament only moves (M204 S3000 T7000) im mm/sec^2 
    * M205 - advanced settings:  minimum travel speed S=while printing T=travel only,  X= maximum xy jerk, Z=maximum Z jerk
  - Remove unused Variables
  - Check Uart Puffer while circle processing (CMD: G2 / G3)
  - Fast Xfer Function --> move Text to Flash
  - Option to deaktivate ARC (G2/G3) function (save flash)
  - Removed modulo (%) operator, which uses an expensive divide

 Version 1.3.05T
  - changed homing function to not conflict with min_software_endstops/max_software_endstops (thanks rGlory)
  - Changed check in arc_func
  - Corrected distance calculation. (thanks jv4779)
  - MAX Feed Rate for Z-Axis reduced to 2 mm/s some Printers had problems with 4 mm/s
  
 Version 1.3.06T
 - the microcontroller can store settings in the EEPROM
 - M500 - stores paramters in EEPROM
 - M501 - reads parameters from EEPROM (if you need reset them after you changed them temporarily).
 - M502 - reverts to the default "factory settings". You still need to store them in EEPROM afterwards if you want to.
 - M503 - Print settings
  

*/

#include <avr/pgmspace.h>
#include <math.h>

#include "fastio.h"
#include "Configuration.h"
#include "pins.h"
#include "Sprinter.h"
#include "speed_lookuptable.h"
#include "heater.h"

#ifdef USE_ARC_FUNCTION
  #include "arc_func.h"
#endif

#ifdef SDSUPPORT
  #include "SdFat.h"
#endif

#ifdef USE_EEPROM_SETTINGS
  #include "store_eeprom.h"
#endif

#ifndef CRITICAL_SECTION_START
#define CRITICAL_SECTION_START  unsigned char _sreg = SREG; cli()
#define CRITICAL_SECTION_END    SREG = _sreg
#endif //CRITICAL_SECTION_START

void __cxa_pure_virtual(){};

// look here for descriptions of gcodes: http://linuxcnc.org/handbook/gcode/g-code.html
// http://objects.reprap.org/wiki/Mendel_User_Manual:_RepRapGCodes

//Implemented Codes
//-------------------
// G0  -> G1
// G1  - Coordinated Movement X Y Z E
// G2  - CW ARC
// G3  - CCW ARC
// G4  - Dwell S<seconds> or P<milliseconds>
// G28 - Home all Axis
// G90 - Use Absolute Coordinates
// G91 - Use Relative Coordinates
// G92 - Set current position to cordinates given

//RepRap M Codes
// M104 - Set extruder target temp
// M105 - Read current temp
// M106 - Fan on
// M107 - Fan off
// M109 - Wait for extruder current temp to reach target temp.
// M114 - Display current position

//Custom M Codes
// M20  - List SD card
// M21  - Init SD card
// M22  - Release SD card
// M23  - Select SD file (M23 filename.g)
// M24  - Start/resume SD print
// M25  - Pause SD print
// M26  - Set SD position in bytes (M26 S12345)
// M27  - Report SD print status
// M28  - Start SD write (M28 filename.g)
// M29  - Stop SD write
//   -  <filename> - Delete file on sd card
// M42  - Set output on free pins, on a non pwm pin (over pin 13 on an arduino mega) use S255 to turn it on and S0 to turn it off. Use P to decide the pin (M42 P23 S255) would turn pin 23 on
// M80  - Turn on Power Supply
// M81  - Turn off Power Supply
// M82  - Set E codes absolute (default)
// M83  - Set E codes relative while in Absolute Coordinates (G90) mode
// M84  - Disable steppers until next move, 
//        or use S<seconds> to specify an inactivity timeout, after which the steppers will be disabled.  S0 to disable the timeout.
// M85  - Set inactivity shutdown timer with parameter S<seconds>. To disable set zero (default)
// M92  - Set axis_steps_per_unit - same syntax as G92
// M115	- Capabilities string
// M119 - Show Endstopper State 
// M140 - Set bed target temp
// M190 - Wait for bed current temp to reach target temp.
// M201 - Set maximum acceleration in units/s^2 for print moves (M201 X1000 Y1000)
// M202 - Set maximum feedrate that your machine can sustain (M203 X200 Y200 Z300 E10000) in mm/sec
// M203 - Set temperture monitor to Sx
// M204 - Set default acceleration: S normal moves T filament only moves (M204 S3000 T7000) im mm/sec^2 
// M205 - advanced settings:  minimum travel speed S=while printing T=travel only,  X= maximum xy jerk, Z=maximum Z jerk

// M220 - set speed factor override percentage S:factor in percent 

// M500 - stores paramters in EEPROM
// M501 - reads parameters from EEPROM (if you need reset them after you changed them temporarily).
// M502 - reverts to the default "factory settings". You still need to store them in EEPROM afterwards if you want to.
// M503 - Print settings

// Debug feature / Testing the PID for Hotend
// M601 - Show Temp jitter from Extruder (min / max value from Hotend Temperatur while printing)
// M602 - Reset Temp jitter from Extruder (min / max val) --> Dont use it while Printing
// M603 - Show Free Ram


#define _VERSION_TEXT "1.3.06T / 17.02.2012"

//Stepper Movement Variables
char axis_codes[NUM_AXIS] = {'X', 'Y', 'Z', 'E'};
float axis_steps_per_unit[4] = _AXIS_STEP_PER_UNIT; 

float max_feedrate[4] = _MAX_FEEDRATE;
float homing_feedrate[] = _HOMING_FEEDRATE;
bool axis_relative_modes[] = _AXIS_RELATIVE_MODES;

float move_acceleration = _ACCELERATION;         // Normal acceleration mm/s^2
float retract_acceleration = _RETRACT_ACCELERATION; // Normal acceleration mm/s^2
float max_xy_jerk = _MAX_XY_JERK;
float max_z_jerk = _MAX_Z_JERK;

long  max_acceleration_units_per_sq_second[4] = _MAX_ACCELERATION_UNITS_PER_SQ_SECOND; // X, Y, Z and E max acceleration in mm/s^2 for printing moves or retracts

//float max_start_speed_units_per_second[] = _MAX_START_SPEED_UNITS_PER_SECOND;
//long  max_travel_acceleration_units_per_sq_second[] = _MAX_TRAVEL_ACCELERATION_UNITS_PER_SQ_SECOND; // X, Y, Z max acceleration in mm/s^2 for travel moves

float mintravelfeedrate = DEFAULT_MINTRAVELFEEDRATE;
float minimumfeedrate = DEFAULT_MINIMUMFEEDRATE;

unsigned long axis_steps_per_sqr_second[NUM_AXIS];
unsigned long plateau_steps;  

//unsigned long axis_max_interval[NUM_AXIS];
//unsigned long axis_travel_steps_per_sqr_second[NUM_AXIS];
//unsigned long max_interval;
//unsigned long steps_per_sqr_second;


//adjustable feed faktor for online tuning printerspeed
volatile int feedmultiply=100; //100->original / 200-> Faktor 2 / 50 -> Faktor 0.5
int saved_feedmultiply;
volatile bool feedmultiplychanged=false;

//boolean acceleration_enabled = false, accelerating = false;
//unsigned long interval;
float destination[NUM_AXIS] = {0.0, 0.0, 0.0, 0.0};
float current_position[NUM_AXIS] = {0.0, 0.0, 0.0, 0.0};


bool home_all_axis = true;
//unsigned ?? ToDo: Check
int feedrate = 1500, next_feedrate, saved_feedrate;

long gcode_N, gcode_LastN;
bool relative_mode = false;  //Determines Absolute or Relative Coordinates

//unsigned long steps_taken[NUM_AXIS];
//long axis_interval[NUM_AXIS]; // for speed delay
//float time_for_move;
//bool relative_mode_e = false;  //Determines Absolute or Relative E Codes while in Absolute Coordinates mode. E is always relative in Relative Coordinates mode.
//long timediff = 0;

//experimental feedrate calc
//float d = 0;
//float axis_diff[NUM_AXIS] = {0, 0, 0, 0};


#ifdef USE_ARC_FUNCTION
//For arc centerpont, send bei Command G2/G3
float offset[3] = {0.0, 0.0, 0.0};
#endif

#ifdef STEP_DELAY_RATIO
  long long_step_delay_ratio = STEP_DELAY_RATIO * 100;
#endif

///oscillation reduction
#ifdef RAPID_OSCILLATION_REDUCTION
  float cumm_wait_time_in_dir[NUM_AXIS]={0.0,0.0,0.0,0.0};
  bool prev_move_direction[NUM_AXIS]={1,1,1,1};
  float osc_wait_remainder = 0.0;
#endif

// comm variables and Commandbuffer
// BUFSIZE is reduced from 8 to 6 to free more RAM for the PLANNER
#define MAX_CMD_SIZE 96
#define BUFSIZE 6 //8
char cmdbuffer[BUFSIZE][MAX_CMD_SIZE];
bool fromsd[BUFSIZE];

//Need 1kb Ram --> only work with Atmega1284
#ifdef SD_FAST_XFER_AKTIV
  char fastxferbuffer[SD_FAST_XFER_CHUNK_SIZE + 1];
  int lastxferchar;
  long xferbytes;
#endif

unsigned char bufindr = 0;
unsigned char bufindw = 0;
unsigned char buflen = 0;
char serial_char;
int serial_count = 0;
boolean comment_mode = false;
char *strchr_pointer; // just a pointer to find chars in the cmd string like X, Y, Z, E, etc

//Send Temperature in °C to Host
int hotendtC = 0, bedtempC = 0;
       
//Inactivity shutdown variables
unsigned long previous_millis_cmd = 0;
unsigned long max_inactive_time = 0;
unsigned long stepper_inactive_time = 0;

//Temp Montor for repetier
unsigned char manage_monitor = 255;


//------------------------------------------------
//Init the SD card 
//------------------------------------------------
#ifdef SDSUPPORT
  Sd2Card card;
  SdVolume volume;
  SdFile root;
  SdFile file;
  uint32_t filesize = 0;
  uint32_t sdpos = 0;
  bool sdmode = false;
  bool sdactive = false;
  bool savetosd = false;
  int16_t read_char_n;
  
  void initsd()
  {
  sdactive = false;
  #if SDSS >- 1
    if(root.isOpen())
        root.close();

    if (!card.init(SPI_FULL_SPEED,SDSS)){
        //if (!card.init(SPI_HALF_SPEED,SDSS))
          showString(PSTR("SD init fail\r\n"));
    }
    else if (!volume.init(&card))
          showString(PSTR("volume.init failed\r\n"));
    else if (!root.openRoot(&volume)) 
          showString(PSTR("openRoot failed\r\n"));
    else{
          sdactive = true;
          print_disk_info();

          #ifdef SDINITFILE
            file.close();
            if(file.open(&root, "init.g", O_READ)){
                sdpos = 0;
                filesize = file.fileSize();
                sdmode = true;
            }
          #endif
    }
    
  #endif
  }
  
  #ifdef SD_FAST_XFER_AKTIV
  
  #ifdef PIDTEMP
    extern int g_heater_pwm_val;
  #endif
  
  void fast_xfer()
  {
    char *pstr;
    boolean done = false;
    
    //force heater pins low
    if(HEATER_0_PIN > -1) WRITE(HEATER_0_PIN,LOW);
    if(HEATER_1_PIN > -1) WRITE(HEATER_1_PIN,LOW);
    
    g_heater_pwm_val = 0;
    
    lastxferchar = 1;
    xferbytes = 0;
    
    pstr = strstr(strchr_pointer+4, " ");
    
    if(pstr == NULL)
    {
      showString(PSTR("invalid command\r\n"));
      return;
    }
    
    *pstr = '\0';
    
    //check mode (currently only RAW is supported
    if(strcmp(strchr_pointer+4, "RAW") != 0)
    {
      showString(PSTR("Invalid transfer codec\r\n"));
      return;
    }else{
      showString(PSTR("Selected codec: "));
      Serial.println(strchr_pointer+4);
    }
    
    if (!file.open(&root, pstr+1, O_CREAT | O_APPEND | O_WRITE | O_TRUNC))
    {
      showString(PSTR("open failed, File: "));
      Serial.print(pstr+1);
      showString(PSTR("."));
    }else{
      showString(PSTR("Writing to file: "));
      Serial.println(pstr+1);
    }
        
    showString(PSTR("ok\r\n"));
    
    //RAW transfer codec
    //Host sends \0 then up to SD_FAST_XFER_CHUNK_SIZE then \0
    //when host is done, it sends \0\0.
    //if a non \0 character is recieved at the beginning, host has failed somehow, kill the transfer.
    
    //read SD_FAST_XFER_CHUNK_SIZE bytes (or until \0 is recieved)
    while(!done)
    {
      while(!Serial.available())
      {
      }
      if(Serial.read() != 0)
      {
        //host has failed, this isn't a RAW chunk, it's an actual command
        file.sync();
        file.close();
        return;
      }

      for(int i=0;i<SD_FAST_XFER_CHUNK_SIZE+1;i++)
      {
        while(!Serial.available())
        {
        }
        lastxferchar = Serial.read();
        //buffer the data...
        fastxferbuffer[i] = lastxferchar;
        
        xferbytes++;
        
        if(lastxferchar == 0)
          break;
      }
      
      if(fastxferbuffer[0] != 0)
      {
        fastxferbuffer[SD_FAST_XFER_CHUNK_SIZE] = 0;
        file.write(fastxferbuffer);
        showString(PSTR("ok\r\n"));
      }else{
        showString(PSTR("Wrote "));
        Serial.print(xferbytes);
        showString(PSTR(" bytes.\r\n"));
        done = true;
      }
    }

    file.sync();
    file.close();
  }
  #endif
    

 void print_disk_info(void)
 {

   // print the type of card
    showString(PSTR("\nCard type: "));
    switch(card.type()) 
    {
      case SD_CARD_TYPE_SD1:
        showString(PSTR("SD1\r\n"));
        break;
      case SD_CARD_TYPE_SD2:
        showString(PSTR("SD2\r\n"));
        break;
      case SD_CARD_TYPE_SDHC:
        showString(PSTR("SDHC\r\n"));
        break;
      default:
        showString(PSTR("Unknown\r\n"));
    }
  
    //uint64_t freeSpace = volume.clusterCount()*volume.blocksPerCluster()*512;
    //uint64_t occupiedSpace = (card.cardSize()*512) - freeSpace;
    // print the type and size of the first FAT-type volume
    uint32_t volumesize;
    showString(PSTR("\nVolume type is FAT"));
    Serial.println(volume.fatType(), DEC);
    
    volumesize = volume.blocksPerCluster(); // clusters are collections of blocks
    volumesize *= volume.clusterCount(); // we'll have a lot of clusters
    volumesize *= 512; // SD card blocks are always 512 bytes
    volumesize /= 1024; //kbytes
    volumesize /= 1024; //Mbytes
    showString(PSTR("Volume size (Mbytes): "));
    Serial.println(volumesize);
   
    // list all files in the card with date and size
    //root.ls(LS_R | LS_DATE | LS_SIZE);
 }

    
    
 
  
  FORCE_INLINE void write_command(char *buf)
  {
      char* begin = buf;
      char* npos = 0;
      char* end = buf + strlen(buf) - 1;
      
      file.writeError = false;
      
      if((npos = strchr(buf, 'N')) != NULL)
      {
          begin = strchr(npos, ' ') + 1;
          end = strchr(npos, '*') - 1;
      }
      
      end[1] = '\r';
      end[2] = '\n';
      end[3] = '\0';
      
      //Serial.println(begin);
      file.write(begin);
      
      if (file.writeError)
      {
          showString(PSTR("error writing to file\r\n"));
      }
  }

#endif


int FreeRam1(void)
{
  extern int  __bss_end;
  extern int* __brkval;
  int free_memory;

  if (reinterpret_cast<int>(__brkval) == 0)
  {
    // if no heap use from end of bss section
    free_memory = reinterpret_cast<int>(&free_memory) - reinterpret_cast<int>(&__bss_end);
  }
  else
  {
    // use from top of stack to heap
    free_memory = reinterpret_cast<int>(&free_memory) - reinterpret_cast<int>(__brkval);
  }
  
  return free_memory;
}

//------------------------------------------------
//Print a String from Flash to Serial (save RAM)
//------------------------------------------------
void showString (PGM_P s) 
{
  char c;
  
  while ((c = pgm_read_byte(s++)) != 0)
    Serial.print(c);
}


//------------------------------------------------
// Init 
//------------------------------------------------
void setup()
{ 
  
  Serial.begin(BAUDRATE);
  showString(PSTR("Sprinter\r\n"));
  showString(PSTR(_VERSION_TEXT));
  showString(PSTR("\r\n"));
  showString(PSTR("start\r\n"));

  for(int i = 0; i < BUFSIZE; i++)
  {
      fromsd[i] = false;
  }
  

  
  //Initialize Dir Pins
  #if X_DIR_PIN > -1
    SET_OUTPUT(X_DIR_PIN);
  #endif
  #if Y_DIR_PIN > -1 
    SET_OUTPUT(Y_DIR_PIN);
  #endif
  #if Z_DIR_PIN > -1 
    SET_OUTPUT(Z_DIR_PIN);
  #endif
  #if E_DIR_PIN > -1 
    SET_OUTPUT(E_DIR_PIN);
  #endif
  
  //Initialize Enable Pins - steppers default to disabled.
  
  #if (X_ENABLE_PIN > -1)
    SET_OUTPUT(X_ENABLE_PIN);
  if(!X_ENABLE_ON) WRITE(X_ENABLE_PIN,HIGH);
  #endif
  #if (Y_ENABLE_PIN > -1)
    SET_OUTPUT(Y_ENABLE_PIN);
  if(!Y_ENABLE_ON) WRITE(Y_ENABLE_PIN,HIGH);
  #endif
  #if (Z_ENABLE_PIN > -1)
    SET_OUTPUT(Z_ENABLE_PIN);
  if(!Z_ENABLE_ON) WRITE(Z_ENABLE_PIN,HIGH);
  #endif
  #if (E_ENABLE_PIN > -1)
    SET_OUTPUT(E_ENABLE_PIN);
  if(!E_ENABLE_ON) WRITE(E_ENABLE_PIN,HIGH);
  #endif

  #ifdef CONTROLLERFAN_PIN
    SET_OUTPUT(CONTROLLERFAN_PIN); //Set pin used for driver cooling fan
  #endif
  
  //endstops and pullups
  #ifdef ENDSTOPPULLUPS
  #if X_MIN_PIN > -1
    SET_INPUT(X_MIN_PIN); 
    WRITE(X_MIN_PIN,HIGH);
  #endif
  #if X_MAX_PIN > -1
    SET_INPUT(X_MAX_PIN); 
    WRITE(X_MAX_PIN,HIGH);
  #endif
  #if Y_MIN_PIN > -1
    SET_INPUT(Y_MIN_PIN); 
    WRITE(Y_MIN_PIN,HIGH);
  #endif
  #if Y_MAX_PIN > -1
    SET_INPUT(Y_MAX_PIN); 
    WRITE(Y_MAX_PIN,HIGH);
  #endif
  #if Z_MIN_PIN > -1
    SET_INPUT(Z_MIN_PIN); 
    WRITE(Z_MIN_PIN,HIGH);
  #endif
  #if Z_MAX_PIN > -1
    SET_INPUT(Z_MAX_PIN); 
    WRITE(Z_MAX_PIN,HIGH);
  #endif
  #else
  #if X_MIN_PIN > -1
    SET_INPUT(X_MIN_PIN); 
  #endif
  #if X_MAX_PIN > -1
    SET_INPUT(X_MAX_PIN); 
  #endif
  #if Y_MIN_PIN > -1
    SET_INPUT(Y_MIN_PIN); 
  #endif
  #if Y_MAX_PIN > -1
    SET_INPUT(Y_MAX_PIN); 
  #endif
  #if Z_MIN_PIN > -1
    SET_INPUT(Z_MIN_PIN); 
  #endif
  #if Z_MAX_PIN > -1
    SET_INPUT(Z_MAX_PIN); 
  #endif
  #endif
  
  #if (HEATER_0_PIN > -1) 
    SET_OUTPUT(HEATER_0_PIN);
    WRITE(HEATER_0_PIN,LOW);
  #endif  
  #if (HEATER_1_PIN > -1) 
    SET_OUTPUT(HEATER_1_PIN);
    WRITE(HEATER_1_PIN,LOW);
  #endif  
  
  //Initialize Fan Pin
  #if (FAN_PIN > -1) 
    SET_OUTPUT(FAN_PIN);
  #endif
  
  //Initialize Alarm Pin
  #if (ALARM_PIN > -1) 
    SET_OUTPUT(ALARM_PIN);
    WRITE(ALARM_PIN,LOW);
  #endif

  //Initialize LED Pin
  #if (LED_PIN > -1) 
    SET_OUTPUT(LED_PIN);
    WRITE(LED_PIN,LOW);
  #endif 
  
//Initialize Step Pins
  #if (X_STEP_PIN > -1) 
    SET_OUTPUT(X_STEP_PIN);
  #endif  
  #if (Y_STEP_PIN > -1) 
    SET_OUTPUT(Y_STEP_PIN);
  #endif  
  #if (Z_STEP_PIN > -1) 
    SET_OUTPUT(Z_STEP_PIN);
  #endif  
  #if (E_STEP_PIN > -1) 
    SET_OUTPUT(E_STEP_PIN);
  #endif  

  for(int8_t i=0; i < NUM_AXIS; i++)
  {
    axis_steps_per_sqr_second[i] = max_acceleration_units_per_sq_second[i] * axis_steps_per_unit[i];
  }

//  for(int i=0; i < NUM_AXIS; i++){
//      axis_max_interval[i] = 100000000.0 / (max_start_speed_units_per_second[i] * axis_steps_per_unit[i]);
//      axis_steps_per_sqr_second[i] = max_acceleration_units_per_sq_second[i] * axis_steps_per_unit[i];
//      axis_travel_steps_per_sqr_second[i] = max_travel_acceleration_units_per_sq_second[i] * axis_steps_per_unit[i];
//  }
    
#ifdef HEATER_USES_MAX6675
  SET_OUTPUT(SCK_PIN);
  WRITE(SCK_PIN,0);
  
  SET_OUTPUT(MOSI_PIN);
  WRITE(MOSI_PIN,1);
  
  SET_INPUT(MISO_PIN);
  WRITE(MISO_PIN,1);
  
  SET_OUTPUT(MAX6675_SS);
  WRITE(MAX6675_SS,1);
#endif  
 
#ifdef SDSUPPORT

  //power to SD reader
  #if SDPOWER > -1
    SET_OUTPUT(SDPOWER); 
    WRITE(SDPOWER,HIGH);
  #endif
  
  showString(PSTR("SD Start\r\n"));
  initsd();

#endif

  #ifdef PID_SOFT_PWM
  showString(PSTR("Soft PWM Init\r\n"));
  init_Timer2_softpwm();
  #endif
  
  showString(PSTR("Planner Init\r\n"));
  plan_init();  // Initialize planner;

  showString(PSTR("Stepper Timer init\r\n"));
  st_init();    // Initialize stepper

  #ifdef USE_EEPROM_SETTINGS
  //first Value --> Init with default
  //second value --> Print settings to UART
  EEPROM_RetrieveSettings(false,false);
  #endif

  //Free Ram
  showString(PSTR("Free Ram: "));
  Serial.println(FreeRam1());
  
  //Planner Buffer Size
  showString(PSTR("Plan Buffer Size:"));
  Serial.print((int)sizeof(block_t)*BLOCK_BUFFER_SIZE);
  showString(PSTR(" / "));
  Serial.println(BLOCK_BUFFER_SIZE);
}



//------------------------------------------------
//MAIN LOOP
//------------------------------------------------
void loop()
{
  if(buflen < (BUFSIZE-1))
    get_command();
  
  if(buflen)
  {
#ifdef SDSUPPORT
    if(savetosd)
    {
        if(strstr(cmdbuffer[bufindr],"M29") == NULL)
        {
            write_command(cmdbuffer[bufindr]);
            showString(PSTR("ok\r\n"));
        }
        else
        {
            file.sync();
            file.close();
            savetosd = false;
            showString(PSTR("Done saving file.\r\n"));
        }
    }
    else
    {
        process_commands();
    }
#else
    process_commands();
#endif

    buflen = (buflen-1);
    //bufindr = (bufindr + 1)%BUFSIZE;
    //Removed modulo (%) operator, which uses an expensive divide and multiplication
    bufindr++;
    if(bufindr == BUFSIZE) bufindr = 0;
  }
  
  //check heater every n milliseconds
  manage_heater();
  manage_inactivity(1);
}

//------------------------------------------------
//Check Uart buffer while arc function ist calc a circle
//------------------------------------------------

void check_buffer_while_arc()
{
  if(buflen < (BUFSIZE-1))
  {
    get_command();
  }
}

//------------------------------------------------
//READ COMMAND FROM UART
//------------------------------------------------
void get_command() 
{ 
  while( Serial.available() > 0  && buflen < BUFSIZE)
  {
    serial_char = Serial.read();
    if(serial_char == '\n' || serial_char == '\r' || serial_char == ':' || serial_count >= (MAX_CMD_SIZE - 1) ) 
    {
      if(!serial_count) return; //if empty line
      cmdbuffer[bufindw][serial_count] = 0; //terminate string
      if(!comment_mode)
      {
        fromsd[bufindw] = false;
        if(strstr(cmdbuffer[bufindw], "N") != NULL)
        {
          strchr_pointer = strchr(cmdbuffer[bufindw], 'N');
          gcode_N = (strtol(&cmdbuffer[bufindw][strchr_pointer - cmdbuffer[bufindw] + 1], NULL, 10));
          if(gcode_N != gcode_LastN+1 && (strstr(cmdbuffer[bufindw], "M110") == NULL) )
          {
            showString(PSTR("Serial Error: Line Number is not Last Line Number+1, Last Line:"));
            Serial.println(gcode_LastN);
            //Serial.println(gcode_N);
            FlushSerialRequestResend();
            serial_count = 0;
            return;
          }
    
          if(strstr(cmdbuffer[bufindw], "*") != NULL)
          {
            byte checksum = 0;
            byte count = 0;
            while(cmdbuffer[bufindw][count] != '*') checksum = checksum^cmdbuffer[bufindw][count++];
            strchr_pointer = strchr(cmdbuffer[bufindw], '*');
  
            if( (int)(strtod(&cmdbuffer[bufindw][strchr_pointer - cmdbuffer[bufindw] + 1], NULL)) != checksum)
            {
              showString(PSTR("Error: checksum mismatch, Last Line:"));
              Serial.println(gcode_LastN);
              FlushSerialRequestResend();
              serial_count = 0;
              return;
            }
            //if no errors, continue parsing
          }
          else 
          {
            showString(PSTR("Error: No Checksum with line number, Last Line:"));
            Serial.println(gcode_LastN);
            FlushSerialRequestResend();
            serial_count = 0;
            return;
          }
    
          gcode_LastN = gcode_N;
          //if no errors, continue parsing
        }
        else  // if we don't receive 'N' but still see '*'
        {
          if((strstr(cmdbuffer[bufindw], "*") != NULL))
          {
            showString(PSTR("Error: No Line Number with checksum, Last Line:"));
            Serial.println(gcode_LastN);
            serial_count = 0;
            return;
          }
        }
        
	if((strstr(cmdbuffer[bufindw], "G") != NULL))
        {
          strchr_pointer = strchr(cmdbuffer[bufindw], 'G');
          switch((int)((strtod(&cmdbuffer[bufindw][strchr_pointer - cmdbuffer[bufindw] + 1], NULL))))
          {
            case 0:
            case 1:
            #ifdef USE_ARC_FUNCTION
            case 2:  //G2
            case 3:  //G3 arc func
            #endif
              #ifdef SDSUPPORT
              if(savetosd)
                break;
              #endif
              showString(PSTR("ok\r\n"));
              //Serial.println("ok"); 
            break;
            
            default:
            break;
          }
        }
		//Removed modulo (%) operator, which uses an expensive divide and multiplication
        //bufindw = (bufindw + 1)%BUFSIZE;
        bufindw++;
        if(bufindw == BUFSIZE) bufindw = 0;
        buflen += 1;
      }
      comment_mode = false; //for new command
      serial_count = 0; //clear buffer
    }
    else
    {
      if(serial_char == ';') comment_mode = true;
      if(!comment_mode) cmdbuffer[bufindw][serial_count++] = serial_char;
    }
  }
#ifdef SDSUPPORT
  if(!sdmode || serial_count!=0)
  {
    return;
  }
  while( filesize > sdpos  && buflen < BUFSIZE)
  {
    read_char_n = file.read();
    serial_char = (char)read_char_n;
    if(serial_char == '\n' || serial_char == '\r' || serial_char == ':' || serial_count >= (MAX_CMD_SIZE - 1) || read_char_n == -1) 
    {
        sdpos = file.curPosition();
        if(sdpos >= filesize)
        {
            sdmode = false;
            showString(PSTR("Done printing file\r\n"));
        }
        if(!serial_count) return; //if empty line
        cmdbuffer[bufindw][serial_count] = 0; //terminate string
        if(!comment_mode)
        {
          fromsd[bufindw] = true;
          buflen += 1;
		  //Removed modulo (%) operator, which uses an expensive divide and multiplication	
          //bufindw = (bufindw + 1)%BUFSIZE;
          bufindw++;
          if(bufindw == BUFSIZE) bufindw = 0;
          
        }
        comment_mode = false; //for new command
        serial_count = 0; //clear buffer
    }
    else
    {
      if(serial_char == ';') comment_mode = true;
      if(!comment_mode) cmdbuffer[bufindw][serial_count++] = serial_char;
    }
  }
#endif

}


FORCE_INLINE float code_value() { return (strtod(&cmdbuffer[bufindr][strchr_pointer - cmdbuffer[bufindr] + 1], NULL)); }
FORCE_INLINE long code_value_long() { return (strtol(&cmdbuffer[bufindr][strchr_pointer - cmdbuffer[bufindr] + 1], NULL, 10)); }
FORCE_INLINE bool code_seen(char code_string[]) { return (strstr(cmdbuffer[bufindr], code_string) != NULL); }  //Return True if the string was found

FORCE_INLINE bool code_seen(char code)
{
  strchr_pointer = strchr(cmdbuffer[bufindr], code);
  return (strchr_pointer != NULL);  //Return True if a character was found
}

//------------------------------------------------
// CHECK COMMAND AND CONVERT VALUES
//------------------------------------------------
FORCE_INLINE void process_commands()
{
  unsigned long codenum; //throw away variable
  char *starpos = NULL;

  if(code_seen('G'))
  {
    switch((int)code_value())
    {
      case 0: // G0 -> G1
      case 1: // G1
        #if (defined DISABLE_CHECK_DURING_ACC) || (defined DISABLE_CHECK_DURING_MOVE) || (defined DISABLE_CHECK_DURING_TRAVEL)
          manage_heater();
        #endif
        get_coordinates(); // For X Y Z E F
        prepare_move();
        previous_millis_cmd = millis();
        //ClearToSend();
        return;
        //break;
      #ifdef USE_ARC_FUNCTION
      case 2: // G2  - CW ARC
        get_arc_coordinates();
        prepare_arc_move(true);
        previous_millis_cmd = millis();
        //break;
        return;
      case 3: // G3  - CCW ARC
        get_arc_coordinates();
        prepare_arc_move(false);
        previous_millis_cmd = millis();
        //break;
        return;  
      #endif  
      case 4: // G4 dwell
        codenum = 0;
        if(code_seen('P')) codenum = code_value(); // milliseconds to wait
        if(code_seen('S')) codenum = code_value() * 1000; // seconds to wait
        codenum += millis();  // keep track of when we started waiting
        while(millis()  < codenum ){
          manage_heater();
        }
        break;
      case 28: //G28 Home all Axis one at a time
        saved_feedrate = feedrate;
        saved_feedmultiply = feedmultiply;
        feedmultiply = 100;      
      
        for(int i=0; i < NUM_AXIS; i++) 
        {
          destination[i] = current_position[i];
        }
        feedrate = 0;

        home_all_axis = !((code_seen(axis_codes[0])) || (code_seen(axis_codes[1])) || (code_seen(axis_codes[2])));

        if((home_all_axis) || (code_seen(axis_codes[X_AXIS]))) 
        {
          if ((X_MIN_PIN > -1 && X_HOME_DIR==-1) || (X_MAX_PIN > -1 && X_HOME_DIR==1))
          {
            st_synchronize();
            current_position[X_AXIS] = -1.5 * X_MAX_LENGTH * X_HOME_DIR;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[X_AXIS] = 0;
            feedrate = homing_feedrate[X_AXIS];
            prepare_move();
  
            st_synchronize();        
            current_position[X_AXIS] = 5 * X_HOME_DIR;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[X_AXIS] = 0;
            prepare_move();
  
            st_synchronize();       
            current_position[X_AXIS] = -10 * X_HOME_DIR;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);  
            destination[X_AXIS] = 0;
            feedrate = homing_feedrate[X_AXIS]/2 ;
            prepare_move();
            st_synchronize();
  
            current_position[X_AXIS] = (X_HOME_DIR == -1) ? 0 : X_MAX_LENGTH;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[X_AXIS] = current_position[X_AXIS];
            feedrate = 0;
          }
        }
        //showString(PSTR("HOME X AXIS\r\n"));

        if((home_all_axis) || (code_seen(axis_codes[Y_AXIS]))) 
        {
          if ((Y_MIN_PIN > -1 && Y_HOME_DIR==-1) || (Y_MAX_PIN > -1 && Y_HOME_DIR==1))
          {
            current_position[Y_AXIS] = -1.5 * Y_MAX_LENGTH * Y_HOME_DIR;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[Y_AXIS] = 0;
            feedrate = homing_feedrate[Y_AXIS];
            prepare_move();
            st_synchronize();
  
            current_position[Y_AXIS] = 5 * Y_HOME_DIR;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[Y_AXIS] = 0;
            prepare_move();
            st_synchronize();
  
            current_position[Y_AXIS] = -10 * Y_HOME_DIR;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[Y_AXIS] = 0;
            feedrate = homing_feedrate[Y_AXIS]/2;
            prepare_move();
            st_synchronize();
  
            current_position[Y_AXIS] = (Y_HOME_DIR == -1) ? 0 : Y_MAX_LENGTH;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[Y_AXIS] = current_position[Y_AXIS];
            feedrate = 0;
          }
        }
        //showString(PSTR("HOME Y AXIS\r\n"));

        if((home_all_axis) || (code_seen(axis_codes[Z_AXIS]))) 
        {
          if ((Z_MIN_PIN > -1 && Z_HOME_DIR==-1) || (Z_MAX_PIN > -1 && Z_HOME_DIR==1))
          {
            current_position[Z_AXIS] = -1.5 * Z_MAX_LENGTH * Z_HOME_DIR;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[Z_AXIS] = 0;
            feedrate = homing_feedrate[Z_AXIS];
            prepare_move();
            st_synchronize();
  
            current_position[Z_AXIS] = 2 * Z_HOME_DIR;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[Z_AXIS] = 0;
            prepare_move();
            st_synchronize();
  
            current_position[Z_AXIS] = -3 * Z_HOME_DIR;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[Z_AXIS] = 0;
            feedrate = homing_feedrate[Z_AXIS]/2;
            prepare_move();
            st_synchronize();
  
            current_position[Z_AXIS] = (Z_HOME_DIR == -1) ? 0 : Z_MAX_LENGTH;
            plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
            destination[Z_AXIS] = current_position[Z_AXIS];
            feedrate = 0;         
          }
        }    
   
        //showString(PSTR("HOME Z AXIS\r\n"));   
      
        feedrate = saved_feedrate;
        feedmultiply = saved_feedmultiply;
      
        previous_millis_cmd = millis();
        break;
      case 90: // G90
        relative_mode = false;
        break;
      case 91: // G91
        relative_mode = true;
        break;
      case 92: // G92
        if(!code_seen(axis_codes[E_AXIS])) 
          st_synchronize();
          
        for(int i=0; i < NUM_AXIS; i++)
        {
          if(code_seen(axis_codes[i])) current_position[i] = code_value();  
        }
        plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
        break;
      default:
            #ifdef SEND_WRONG_CMD_INFO
              showString(PSTR("Unknown G-COM:"));
              Serial.println(cmdbuffer[bufindr]);
            #endif
      break;
    }
  }

  else if(code_seen('M'))
  {
    
    switch( (int)code_value() ) 
    {
#ifdef SDSUPPORT
        
      case 20: // M20 - list SD card
        showString(PSTR("Begin file list\r\n"));
        root.ls();
        showString(PSTR("End file list\r\n"));
        break;
      case 21: // M21 - init SD card
        sdmode = false;
        initsd();
        break;
      case 22: //M22 - release SD card
        sdmode = false;
        sdactive = false;
        break;
      case 23: //M23 - Select file
        if(sdactive)
        {
            sdmode = false;
            file.close();
            starpos = (strchr(strchr_pointer + 4,'*'));
            
            if(starpos!=NULL)
                *(starpos-1)='\0';
            
            if (file.open(&root, strchr_pointer + 4, O_READ)) 
            {
                showString(PSTR("File opened:"));
                Serial.print(strchr_pointer + 4);
                showString(PSTR(" Size:"));
                Serial.println(file.fileSize());
                sdpos = 0;
                filesize = file.fileSize();
                showString(PSTR("File selected\r\n"));
            }
            else
            {
                showString(PSTR("file.open failed\r\n"));
            }
        }
        break;
      case 24: //M24 - Start SD print
        if(sdactive)
        {
            sdmode = true;
        }
        break;
      case 25: //M25 - Pause SD print
        if(sdmode)
        {
            sdmode = false;
        }
        break;
      case 26: //M26 - Set SD index
        if(sdactive && code_seen('S'))
        {
            sdpos = code_value_long();
            file.seekSet(sdpos);
        }
        break;
      case 27: //M27 - Get SD status
        if(sdactive)
        {
            showString(PSTR("SD printing byte "));
            Serial.print(sdpos);
            showString(PSTR("/"));
            Serial.println(filesize);
        }
        else
        {
            showString(PSTR("Not SD printing\r\n"));
        }
        break;
      case 28: //M28 - Start SD write
        if(sdactive)
        {
          char* npos = 0;
            file.close();
            sdmode = false;
            starpos = (strchr(strchr_pointer + 4,'*'));
            if(starpos != NULL)
            {
              npos = strchr(cmdbuffer[bufindr], 'N');
              strchr_pointer = strchr(npos,' ') + 1;
              *(starpos-1) = '\0';
            }
            
            if (!file.open(&root, strchr_pointer+4, O_CREAT | O_APPEND | O_WRITE | O_TRUNC))
            {
              showString(PSTR("open failed, File: "));
              Serial.print(strchr_pointer + 4);
              showString(PSTR("."));
            }
            else
            {
              savetosd = true;
              showString(PSTR("Writing to file: "));
              Serial.println(strchr_pointer + 4);
            }
        }
        break;
      case 29: //M29 - Stop SD write
        //processed in write to file routine above
        //savetosd = false;
        break;
  #ifndef SD_FAST_XFER_AKTIV
      case 30: // M30 filename - Delete file
        if(sdactive)
        {
            sdmode = false;
            file.close();
            
            starpos = (strchr(strchr_pointer + 4,'*'));
            
            if(starpos!=NULL)
                *(starpos-1)='\0';
            
            if(file.remove(&root, strchr_pointer + 4))
            {
              showString(PSTR("File deleted\r\n"));
            }
            else
            {
              showString(PSTR("Deletion failed\r\n"));
            }
        }
        break;  
   #else     
      case 30: //M30 - fast SD transfer
        fast_xfer();
        break;
      case 31: //M31 - high speed xfer capabilities
        showString(PSTR("RAW:"));
        Serial.println(SD_FAST_XFER_CHUNK_SIZE);
        break;
   #endif
        
#endif
      case 42: //M42 -Change pin status via gcode
        if (code_seen('S'))
        {
          int pin_status = code_value();
          if (code_seen('P') && pin_status >= 0 && pin_status <= 255)
          {
            int pin_number = code_value();
            for(int i = 0; i < sizeof(sensitive_pins); i++)
            {
              if (sensitive_pins[i] == pin_number)
              {
                pin_number = -1;
                break;
              }
            }
            
            if (pin_number > -1)
            {              
              pinMode(pin_number, OUTPUT);
              digitalWrite(pin_number, pin_status);
              //analogWrite(pin_number, pin_status);
            }
          }
        }
        break;
      case 104: // M104
        if (code_seen('S')) target_raw = temp2analogh(target_temp = code_value());
        #ifdef WATCHPERIOD
            if(target_raw > current_raw)
            {
                watchmillis = max(1,millis());
                watch_raw = current_raw;
            }
            else
            {
                watchmillis = 0;
            }
        #endif
        break;
      case 140: // M140 set bed temp
        #if TEMP_1_PIN > -1 || defined BED_USES_AD595
            if (code_seen('S')) target_bed_raw = temp2analogBed(code_value());
        #endif
        break;
      case 105: // M105
        #if (TEMP_0_PIN > -1) || defined (HEATER_USES_MAX6675)|| defined HEATER_USES_AD595
          hotendtC = analog2temp(current_raw);
        #endif
        #if TEMP_1_PIN > -1 || defined BED_USES_AD595
          bedtempC = analog2tempBed(current_bed_raw);
        #endif
        #if (TEMP_0_PIN > -1) || defined (HEATER_USES_MAX6675) || defined HEATER_USES_AD595
            showString(PSTR("ok T:"));
            Serial.print(hotendtC); 
          #ifdef PIDTEMP
            showString(PSTR(" @:"));
            Serial.print(heater_duty); 
            /*
            showString(PSTR(",P:"));
            Serial.print(pTerm);
            showString(PSTR(",I:"));
            Serial.print(iTerm);
            showString(PSTR(",D:"));
            Serial.print(dTerm);
            */
            #ifdef AUTOTEMP
              showString(PSTR(",AU:"));
              Serial.print(autotemp_setpoint);
            #endif
          #endif
          #if TEMP_1_PIN > -1 || defined BED_USES_AD595
            showString(PSTR(" B:"));
            Serial.println(bedtempC); 
          #else
            Serial.println();
          #endif
        #else
          #error No temperature source available
        #endif
        return;
        //break;
      case 109: { // M109 - Wait for extruder heater to reach target.
        if (code_seen('S')) target_raw = temp2analogh(target_temp = code_value());
        #ifdef WATCHPERIOD
            if(target_raw>current_raw)
            {
                watchmillis = max(1,millis());
                watch_raw = current_raw;
            }
            else
            {
                watchmillis = 0;
            }
        #endif
        codenum = millis(); 
        
        /* See if we are heating up or cooling down */
        bool target_direction = (current_raw < target_raw);  // true if heating, false if cooling
        
      #ifdef TEMP_RESIDENCY_TIME
        long residencyStart;
        residencyStart = -1;
        /* continue to loop until we have reached the target temp   
           _and_ until TEMP_RESIDENCY_TIME hasn't passed since we reached it */
        while( (target_direction ? (current_raw < target_raw) : (current_raw > target_raw))
            || (residencyStart > -1 && (millis() - residencyStart) < TEMP_RESIDENCY_TIME*1000) ) {
      #else
        while ( target_direction ? (current_raw < target_raw) : (current_raw > target_raw) ) {
      #endif
          if( (millis() - codenum) > 1000 ) //Print Temp Reading every 1 second while heating up/cooling down
          {
            showString(PSTR("T:"));
            Serial.println( analog2temp(current_raw) );
            codenum = millis();
          }
          manage_heater();
          #ifdef TEMP_RESIDENCY_TIME
            /* start/restart the TEMP_RESIDENCY_TIME timer whenever we reach target temp for the first time
               or when current temp falls outside the hysteresis after target temp was reached */
            if (   (residencyStart == -1 &&  target_direction && current_raw >= target_raw)
                || (residencyStart == -1 && !target_direction && current_raw <= target_raw)
                || (residencyStart > -1 && labs(analog2temp(current_raw) - analog2temp(target_raw)) > TEMP_HYSTERESIS) ) {
              residencyStart = millis();
            }
          #endif
	    }
      }
      break;
      case 190: // M190 - Wait bed for heater to reach target.
      #if TEMP_1_PIN > -1
        if (code_seen('S')) target_bed_raw = temp2analogBed(code_value());
        codenum = millis(); 
        while(current_bed_raw < target_bed_raw) 
        {
          if( (millis()-codenum) > 1000 ) //Print Temp Reading every 1 second while heating up.
          {
            hotendtC=analog2temp(current_raw);
            showString(PSTR("T:"));
            Serial.print( hotendtC );
            showString(PSTR(" B:"));
            Serial.println( analog2tempBed(current_bed_raw) ); 
            codenum = millis(); 
          }
          manage_heater();
        }
      #endif
      break;
      #if FAN_PIN > -1
      case 106: //M106 Fan On
        if (code_seen('S'))
        {
            WRITE(FAN_PIN, HIGH);
            //analogWrite(FAN_PIN, constrain(code_value(),0,255) );
        }
        else 
        {
            WRITE(FAN_PIN, HIGH);
            //analogWrite(FAN_PIN, 255 );
        }
        break;
      case 107: //M107 Fan Off
          //analogWrite(FAN_PIN, 0);
          WRITE(FAN_PIN, LOW);
        break;
      #endif
      #if (PS_ON_PIN > -1)
      case 80: // M81 - ATX Power On
        SET_OUTPUT(PS_ON_PIN); //GND
        break;
      case 81: // M81 - ATX Power Off
        SET_INPUT(PS_ON_PIN); //Floating
        break;
      #endif
      case 82:
        axis_relative_modes[3] = false;
        break;
      case 83:
        axis_relative_modes[3] = true;
        break;
      case 84:
        st_synchronize(); // wait for all movements to finish
        if(code_seen('S'))
        {
          stepper_inactive_time = code_value() * 1000; 
        }
        else
        { 
          disable_x(); 
          disable_y(); 
          disable_z(); 
          disable_e(); 
        }
        break;
      case 85: // M85
        code_seen('S');
        max_inactive_time = code_value() * 1000; 
        break;
      case 92: // M92
        for(int i=0; i < NUM_AXIS; i++) 
        {
          if(code_seen(axis_codes[i])) axis_steps_per_unit[i] = code_value();
        }
        
          // Update start speed intervals and axis order. TODO: refactor axis_max_interval[] calculation into a function, as it
          // should also be used in setup() as well
//        long temp_max_intervals[NUM_AXIS];
//        for(int i=0; i < NUM_AXIS; i++) 
//        {
//          axis_max_interval[i] = 100000000.0 / (max_start_speed_units_per_second[i] * axis_steps_per_unit[i]);//TODO: do this for
//          all steps_per_unit related variables
//        }
        break;
      case 115: // M115
        showString(PSTR("FIRMWARE_NAME: Sprinter Experimental PROTOCOL_VERSION:1.0 MACHINE_TYPE:Mendel EXTRUDER_COUNT:1\r\n"));
        //Serial.println(uuid);
        showString(PSTR(_DEF_CHAR_UUID));
        showString(PSTR("\r\n"));
        break;
      case 114: // M114
	showString(PSTR("X:"));
        Serial.print(current_position[0]);
	showString(PSTR("Y:"));
        Serial.print(current_position[1]);
	showString(PSTR("Z:"));
        Serial.print(current_position[2]);
	showString(PSTR("E:"));
        Serial.println(current_position[3]);
        break;
      case 119: // M119
      
      	#if (X_MIN_PIN > -1)
          showString(PSTR("x_min:"));
          Serial.print((READ(X_MIN_PIN)^X_ENDSTOP_INVERT)?"H ":"L ");
      	#endif
      	#if (X_MAX_PIN > -1)
          showString(PSTR("x_max:"));
          Serial.print((READ(X_MAX_PIN)^X_ENDSTOP_INVERT)?"H ":"L ");
      	#endif
      	#if (Y_MIN_PIN > -1)
      	  showString(PSTR("y_min:"));
          Serial.print((READ(Y_MIN_PIN)^Y_ENDSTOP_INVERT)?"H ":"L ");
      	#endif
      	#if (Y_MAX_PIN > -1)
      	  showString(PSTR("y_max:"));
          Serial.print((READ(Y_MAX_PIN)^Y_ENDSTOP_INVERT)?"H ":"L ");
      	#endif
      	#if (Z_MIN_PIN > -1)
      	  showString(PSTR("z_min:"));
          Serial.print((READ(Z_MIN_PIN)^Z_ENDSTOP_INVERT)?"H ":"L ");
      	#endif
      	#if (Z_MAX_PIN > -1)
      	  showString(PSTR("z_max:"));
          Serial.print((READ(Z_MAX_PIN)^Z_ENDSTOP_INVERT)?"H ":"L ");
      	#endif
      
        showString(PSTR("\r\n"));
      	break;
      case 201: // M201

        for(int8_t i=0; i < NUM_AXIS; i++) 
        {
          if(code_seen(axis_codes[i]))
          {
            max_acceleration_units_per_sq_second[i] = code_value();
            axis_steps_per_sqr_second[i] = code_value() * axis_steps_per_unit[i];
          }
        }

      #if 0 // Not used for Sprinter/grbl gen6
      case 202: // M202
        for(int i=0; i < NUM_AXIS; i++) 
        {
          if(code_seen(axis_codes[i])) axis_travel_steps_per_sqr_second[i] = code_value() * axis_steps_per_unit[i];
        }
        break;
      #else  
      case 202: // M202 max feedrate mm/sec
        for(int8_t i=0; i < NUM_AXIS; i++) 
        {
          if(code_seen(axis_codes[i])) max_feedrate[i] = code_value();
        }
      break;
      #endif
      case 203: // M203 Temperature monitor
          if(code_seen('S')) manage_monitor = code_value();
          if(manage_monitor==100) manage_monitor=1; // Set 100 to heated bed
      break;
      case 204: // M204 acclereration S normal moves T filmanent only moves
          if(code_seen('S')) move_acceleration = code_value() ;
          if(code_seen('T')) retract_acceleration = code_value() ;
      break;
      case 205: //M205 advanced settings:  minimum travel speed S=while printing T=travel only,  B=minimum segment time X= maximum xy jerk, Z=maximum Z jerk
        if(code_seen('S')) minimumfeedrate = code_value();
        if(code_seen('T')) mintravelfeedrate = code_value();
      //if(code_seen('B')) minsegmenttime = code_value() ;
        if(code_seen('X')) max_xy_jerk = code_value() ;
        if(code_seen('Z')) max_z_jerk = code_value() ;
      break;  
      case 220: // M220 S<factor in percent>- set speed factor override percentage
      {
        if(code_seen('S')) 
        {
          feedmultiply = code_value() ;
          if(feedmultiply < 20) feedmultiply = 20;
          if(feedmultiply > 200) feedmultiply = 200;
          feedmultiplychanged=true;
        }
      }
      break;
#ifdef USE_EEPROM_SETTINGS
      case 500: // Store settings in EEPROM
      {
        EEPROM_StoreSettings();
      }
      break;
      case 501: // Read settings from EEPROM
      {
        EEPROM_RetrieveSettings(false,true);
      }
      break;
      case 502: // Revert to default settings
      {
        EEPROM_RetrieveSettings(true,true);
      }
      break;
      case 503: // print settings currently in memory
      {
        EEPROM_printSettings();
      }
      break;  
#endif      
#ifdef DEBUG_HEATER_TEMP
      case 601: // M601  show Extruder Temp jitter
        #if (TEMP_0_PIN > -1) || defined (HEATER_USES_MAX6675)|| defined HEATER_USES_AD595
          if(current_raw_maxval > 0)
            tt_maxval = analog2temp(current_raw_maxval);
          if(current_raw_minval < 10000)  
            tt_minval = analog2temp(current_raw_minval);
        #endif
        
            showString(PSTR("Tmin:"));
            Serial.print(tt_minval); 
            showString(PSTR(" / Tmax:"));
            Serial.print(tt_maxval); 
            showString(PSTR(" "));
      break;
      case 602: // M602  reset Extruder Temp jitter
            current_raw_minval = 32000;
            current_raw_maxval = -32000;
        
            showString(PSTR("T Minmax Reset "));
      break;
#endif
      case 603: // M603  Free RAM
            showString(PSTR("Free Ram: "));
            Serial.println(FreeRam1()); 
      break;
      default:
            #ifdef SEND_WRONG_CMD_INFO
              showString(PSTR("Unknown M-COM:"));
              Serial.println(cmdbuffer[bufindr]);
            #endif
      break;

    }
    
  }
  else{
      showString(PSTR("Unknown command:\r\n"));
      Serial.println(cmdbuffer[bufindr]);
  }
  
  ClearToSend();
      
}



void FlushSerialRequestResend()
{
  //char cmdbuffer[bufindr][100]="Resend:";
  Serial.flush();
  showString(PSTR("Resend:"));
  Serial.println(gcode_LastN + 1);
  ClearToSend();
}

void ClearToSend()
{
  previous_millis_cmd = millis();
  #ifdef SDSUPPORT
  if(fromsd[bufindr])
    return;
  #endif
  showString(PSTR("ok\r\n"));
  //Serial.println("ok");
}

FORCE_INLINE void get_coordinates()
{
  for(int i=0; i < NUM_AXIS; i++)
  {
    if(code_seen(axis_codes[i])) destination[i] = (float)code_value() + (axis_relative_modes[i] || relative_mode)*current_position[i];
    else destination[i] = current_position[i];                                                       //Are these else lines really needed?
  }
  
  if(code_seen('F'))
  {
    next_feedrate = code_value();
    if(next_feedrate > 0.0) feedrate = next_feedrate;
  }
}

#ifdef USE_ARC_FUNCTION
FORCE_INLINE void get_arc_coordinates()
{
   get_coordinates();
   if(code_seen('I')) offset[0] = code_value();
   if(code_seen('J')) offset[1] = code_value();
}
#endif


void prepare_move()
{
  long help_feedrate = 0;

  if (min_software_endstops) 
  {
    if (destination[X_AXIS] < 0) destination[X_AXIS] = 0.0;
    if (destination[Y_AXIS] < 0) destination[Y_AXIS] = 0.0;
    if (destination[Z_AXIS] < 0) destination[Z_AXIS] = 0.0;
  }

  if (max_software_endstops) 
  {
    if (destination[X_AXIS] > X_MAX_LENGTH) destination[X_AXIS] = X_MAX_LENGTH;
    if (destination[Y_AXIS] > Y_MAX_LENGTH) destination[Y_AXIS] = Y_MAX_LENGTH;
    if (destination[Z_AXIS] > Z_MAX_LENGTH) destination[Z_AXIS] = Z_MAX_LENGTH;
  }

  help_feedrate = ((long)feedrate*(long)feedmultiply);
  plan_buffer_line(destination[X_AXIS], destination[Y_AXIS], destination[Z_AXIS], destination[E_AXIS], help_feedrate/6000.0);
  
  for(int i=0; i < NUM_AXIS; i++)
  {
    current_position[i] = destination[i];
  } 
}


#ifdef USE_ARC_FUNCTION
void prepare_arc_move(char isclockwise) 
{

  float r = hypot(offset[X_AXIS], offset[Y_AXIS]); // Compute arc radius for mc_arc
  long help_feedrate = 0;

  
  help_feedrate = ((long)feedrate*(long)feedmultiply);
  // Trace the arc
  mc_arc(current_position, destination, offset, X_AXIS, Y_AXIS, Z_AXIS, help_feedrate/6000.0, r, isclockwise);
  
  // As far as the parser is concerned, the position is now == target. In reality the
  // motion control system might still be processing the action and the real tool position
  // in any intermediate location.
  for(int8_t i=0; i < NUM_AXIS; i++) 
  {
    current_position[i] = destination[i];
  }
}
#endif

FORCE_INLINE void kill()
{
  #if TEMP_0_PIN > -1
    target_raw=0;
    WRITE(HEATER_0_PIN,LOW);
  #endif
  
  #if TEMP_1_PIN > -1
    target_bed_raw=0;
    if(HEATER_1_PIN > -1) WRITE(HEATER_1_PIN,LOW);
  #endif

  disable_x();
  disable_y();
  disable_z();
  disable_e();
  
  if(PS_ON_PIN > -1) pinMode(PS_ON_PIN,INPUT);
  
}

FORCE_INLINE void manage_inactivity(byte debug) 
{ 
  if( (millis()-previous_millis_cmd) >  max_inactive_time ) if(max_inactive_time) kill(); 
  
  if( (millis()-previous_millis_cmd) >  stepper_inactive_time ) if(stepper_inactive_time) 
  { 
    disable_x(); 
    disable_y(); 
    disable_z(); 
    disable_e(); 
  }
  check_axes_activity();
}




// Planner with Interrupt for Stepper

/*  
 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 destionation 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)
 */


static block_t block_buffer[BLOCK_BUFFER_SIZE];            // A ring buffer for motion instructions
static volatile unsigned char block_buffer_head;           // Index of the next block to be pushed
static volatile unsigned char block_buffer_tail;           // Index of the block to process now

//===========================================================================
//=============================private variables ============================
//===========================================================================

// Returns the index of the next block in the ring buffer
// NOTE: Removed modulo (%) operator, which uses an expensive divide and multiplication.
static int8_t next_block_index(int8_t block_index) {
  block_index++;
  if (block_index == BLOCK_BUFFER_SIZE) { block_index = 0; }
  return(block_index);
}


// Returns the index of the previous block in the ring buffer
static int8_t prev_block_index(int8_t block_index) {
  if (block_index == 0) { block_index = BLOCK_BUFFER_SIZE; }
  block_index--;
  return(block_index);
}

// The current position of the tool in absolute steps
static long position[4];   
static float previous_speed[4]; // Speed of previous path line segment
static float previous_nominal_speed; // Nominal speed of previous path line segment


// Calculates the distance (not time) it takes to accelerate from initial_rate to target_rate using the 
// given acceleration:
FORCE_INLINE float estimate_acceleration_distance(float initial_rate, float target_rate, float acceleration)
{
  if (acceleration!=0) {
  return((target_rate*target_rate-initial_rate*initial_rate)/
         (2.0*acceleration));
  }
  else {
    return 0.0;  // acceleration was 0, set acceleration distance to 0
  }
}

// This function gives you the point at which you must start braking (at the rate of -acceleration) if 
// you started at speed initial_rate and accelerated until this point and want to end at the final_rate after
// a total travel of distance. This can be used to compute the intersection point between acceleration and
// deceleration in the cases where the trapezoid has no plateau (i.e. never reaches maximum speed)

FORCE_INLINE float intersection_distance(float initial_rate, float final_rate, float acceleration, float distance) 
{
 if (acceleration!=0) {
  return((2.0*acceleration*distance-initial_rate*initial_rate+final_rate*final_rate)/
         (4.0*acceleration) );
  }
  else {
    return 0.0;  // acceleration was 0, set intersection distance to 0
  }
}

// Calculates trapezoid parameters so that the entry- and exit-speed is compensated by the provided factors.

void calculate_trapezoid_for_block(block_t *block, float entry_factor, float exit_factor) {
  unsigned long initial_rate = ceil(block->nominal_rate*entry_factor); // (step/min)
  unsigned long final_rate = ceil(block->nominal_rate*exit_factor); // (step/min)

  // Limit minimal step rate (Otherwise the timer will overflow.)
  if(initial_rate <120) {initial_rate=120; }
  if(final_rate < 120) {final_rate=120;  }
  
  long acceleration = block->acceleration_st;
  int32_t accelerate_steps =
    ceil(estimate_acceleration_distance(block->initial_rate, block->nominal_rate, acceleration));
  int32_t decelerate_steps =
    floor(estimate_acceleration_distance(block->nominal_rate, block->final_rate, -acceleration));
    
  // Calculate the size of Plateau of Nominal Rate.
  int32_t 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 acceleration 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(block->initial_rate, block->final_rate, acceleration, block->step_event_count));
    accelerate_steps = max(accelerate_steps,0); // Check limits due to numerical round-off
    accelerate_steps = min(accelerate_steps,block->step_event_count);
    plateau_steps = 0;
  }

  #ifdef ADVANCE
    volatile long initial_advance = block->advance*entry_factor*entry_factor; 
    volatile long final_advance = block->advance*exit_factor*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 == false) { // 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;
  #ifdef ADVANCE
      block->initial_advance = initial_advance;
      block->final_advance = final_advance;
  #endif //ADVANCE
  }
  CRITICAL_SECTION_END;
}                    

// Calculates the maximum allowable speed at this point when you must be able to reach target_velocity using the 
// acceleration within the allotted distance.
FORCE_INLINE float max_allowable_speed(float acceleration, float target_velocity, float distance) {
  return  sqrt(target_velocity*target_velocity-2*acceleration*distance);
}

// "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 planner_recalculate() when scanning the plan from last to first entry.
void planner_reverse_pass_kernel(block_t *previous, block_t *current, block_t *next) {
  if(!current) { return; }
  
    if (next) {
    // 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.
    if (current->entry_speed != current->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.
      if ((!current->nominal_length_flag) && (current->max_entry_speed > next->entry_speed)) {
        current->entry_speed = min( current->max_entry_speed,
          max_allowable_speed(-current->acceleration,next->entry_speed,current->millimeters));
      } else {
        current->entry_speed = current->max_entry_speed;
      }
      current->recalculate_flag = true;
    
    }
  } // Skip last block. Already initialized and set for recalculation.
}

// planner_recalculate() needs to go over the current plan twice. Once in reverse and once forward. This 
// implements the reverse pass.
void planner_reverse_pass() {
  uint8_t block_index = block_buffer_head;
  if(((block_buffer_head-block_buffer_tail + BLOCK_BUFFER_SIZE) & (BLOCK_BUFFER_SIZE - 1)) > 3) {
    block_index = (block_buffer_head - 3) & (BLOCK_BUFFER_SIZE - 1);
    block_t *block[3] = { NULL, NULL, NULL };
    while(block_index != block_buffer_tail) { 
      block_index = prev_block_index(block_index); 
      block[2]= block[1];
      block[1]= block[0];
      block[0] = &block_buffer[block_index];
      planner_reverse_pass_kernel(block[0], block[1], block[2]);
    }
  }
}


// The kernel called by planner_recalculate() when scanning the plan from first to last entry.
void planner_forward_pass_kernel(block_t *previous, block_t *current, block_t *next) {
  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->nominal_length_flag) {
    if (previous->entry_speed < current->entry_speed) {
      double 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->recalculate_flag = true;
      }
    }
  }
}

// planner_recalculate() needs to go over the current plan twice. Once in reverse and once forward. This 
// implements the forward pass.
void planner_forward_pass() {
  uint8_t block_index = block_buffer_tail;
  block_t *block[3] = { NULL, NULL, NULL };

  while(block_index != block_buffer_head) {
    block[0] = block[1];
    block[1] = block[2];
    block[2] = &block_buffer[block_index];
    planner_forward_pass_kernel(block[0],block[1],block[2]);
    block_index = next_block_index(block_index);
  }
  planner_forward_pass_kernel(block[1], block[2], NULL);
}

// Recalculates the trapezoid speed profiles for all blocks in the plan according to the 
// entry_factor for each junction. Must be called by planner_recalculate() after 
// updating the blocks.
void planner_recalculate_trapezoids() {
  int8_t block_index = block_buffer_tail;
  block_t *current;
  block_t *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->recalculate_flag || next->recalculate_flag) {
        // NOTE: Entry and exit factors always > 0 by all previous logic operations.
        calculate_trapezoid_for_block(current, current->entry_speed/current->nominal_speed,
          next->entry_speed/current->nominal_speed);
        current->recalculate_flag = false; // 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 != NULL) {
    calculate_trapezoid_for_block(next, next->entry_speed/next->nominal_speed,
      MINIMUM_PLANNER_SPEED/next->nominal_speed);
    next->recalculate_flag = false;
  }
}

// Recalculates the motion plan according to the following algorithm:
//
//   1. Go over every block in reverse order and calculate a junction speed reduction (i.e. block_t.entry_factor) 
//      so that:
//     a. The junction jerk is within the set limit
//     b. No speed reduction within one block requires faster deceleration than the one, true constant 
//        acceleration.
//   2. Go over every block in chronological order and dial down junction speed reduction values if 
//     a. The speed increase within one block would require faster accelleration than the one, true 
//        constant acceleration.
//
// When these stages are complete all blocks have an entry_factor that will allow all speed changes to 
// be performed using only the one, true constant acceleration, and where no junction jerk is jerkier than 
// the set limit. Finally it will:
//
//   3. Recalculate trapezoids for all blocks.

void planner_recalculate() {   
  planner_reverse_pass();
  planner_forward_pass();
  planner_recalculate_trapezoids();
}

void plan_init() {
  block_buffer_head = 0;
  block_buffer_tail = 0;
  memset(position, 0, sizeof(position)); // clear position
  previous_speed[0] = 0.0;
  previous_speed[1] = 0.0;
  previous_speed[2] = 0.0;
  previous_speed[3] = 0.0;
  previous_nominal_speed = 0.0;
}



FORCE_INLINE void plan_discard_current_block() {
  if (block_buffer_head != block_buffer_tail) {
    block_buffer_tail = (block_buffer_tail + 1) & BLOCK_BUFFER_MASK;  
  }
}

FORCE_INLINE block_t *plan_get_current_block() {
  if (block_buffer_head == block_buffer_tail) { 
    return(NULL); 
  }
  block_t *block = &block_buffer[block_buffer_tail];
  block->busy = true;
  return(block);
}

// Gets the current block. Returns NULL if buffer empty
FORCE_INLINE bool blocks_queued() 
{
  if (block_buffer_head == block_buffer_tail) { 
    return false; 
  }
  else
    return true;
}

void check_axes_activity() {
  unsigned char x_active = 0;
  unsigned char y_active = 0;  
  unsigned char z_active = 0;
  unsigned char e_active = 0;
  block_t *block;

  if(block_buffer_tail != block_buffer_head) {
    uint8_t block_index = block_buffer_tail;
    while(block_index != block_buffer_head) {
      block = &block_buffer[block_index];
      if(block->steps_x != 0) x_active++;
      if(block->steps_y != 0) y_active++;
      if(block->steps_z != 0) z_active++;
      if(block->steps_e != 0) e_active++;
      block_index = (block_index+1) & (BLOCK_BUFFER_SIZE - 1);
    }
  }
  if((DISABLE_X) && (x_active == 0)) disable_x();
  if((DISABLE_Y) && (y_active == 0)) disable_y();
  if((DISABLE_Z) && (z_active == 0)) disable_z();
  if((DISABLE_E) && (e_active == 0)) disable_e();
}


float junction_deviation = 0.1;
// Add a new linear movement to the buffer. steps_x, _y and _z is the absolute position in 
// mm. Microseconds specify how many microseconds the move should take to perform. To aid acceleration
// calculation the caller must also provide the physical length of the line in millimeters.
void plan_buffer_line(float x, float y, float z, float e, float feed_rate)
{
  // 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) { 
    manage_heater(); 
    manage_inactivity(1); 
  }

  // 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[4];
  target[X_AXIS] = lround(x*axis_steps_per_unit[X_AXIS]);
  target[Y_AXIS] = lround(y*axis_steps_per_unit[Y_AXIS]);
  target[Z_AXIS] = lround(z*axis_steps_per_unit[Z_AXIS]);     
  target[E_AXIS] = lround(e*axis_steps_per_unit[E_AXIS]);
  
  // 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
  block->steps_x = labs(target[X_AXIS]-position[X_AXIS]);
  block->steps_y = labs(target[Y_AXIS]-position[Y_AXIS]);
  block->steps_z = labs(target[Z_AXIS]-position[Z_AXIS]);
  block->steps_e = labs(target[E_AXIS]-position[E_AXIS]);
  block->step_event_count = max(block->steps_x, max(block->steps_y, max(block->steps_z, block->steps_e)));

  // Bail if this is a zero-length block
  if (block->step_event_count <=dropsegments) { return; };

  // Compute direction bits for this block 
  block->direction_bits = 0;
  if (target[X_AXIS] < position[X_AXIS]) { block->direction_bits |= (1<<X_AXIS); }
  if (target[Y_AXIS] < position[Y_AXIS]) { block->direction_bits |= (1<<Y_AXIS); }
  if (target[Z_AXIS] < position[Z_AXIS]) { block->direction_bits |= (1<<Z_AXIS); }
  if (target[E_AXIS] < position[E_AXIS]) { block->direction_bits |= (1<<E_AXIS); }
  

 #ifdef DELAY_ENABLE
  if(block->steps_x != 0)
  {
    enable_x();
    delayMicroseconds(DELAY_ENABLE);
  }
  if(block->steps_y != 0)
  {
    enable_y();
    delayMicroseconds(DELAY_ENABLE);
  }
  if(if(block->steps_z != 0))
  {
    enable_z();
    delayMicroseconds(DELAY_ENABLE);
  }
  if(if(block->steps_e != 0))
  {
    enable_e();
    delayMicroseconds(DELAY_ENABLE);
  }
 #else
  //enable active axes
  if(block->steps_x != 0) enable_x();
  if(block->steps_y != 0) enable_y();
  if(block->steps_z != 0) enable_z();
  if(block->steps_e != 0) enable_e();
 #endif 

  float delta_mm[4];
  delta_mm[X_AXIS] = (target[X_AXIS]-position[X_AXIS])/axis_steps_per_unit[X_AXIS];
  delta_mm[Y_AXIS] = (target[Y_AXIS]-position[Y_AXIS])/axis_steps_per_unit[Y_AXIS];
  delta_mm[Z_AXIS] = (target[Z_AXIS]-position[Z_AXIS])/axis_steps_per_unit[Z_AXIS];
  delta_mm[E_AXIS] = (target[E_AXIS]-position[E_AXIS])/axis_steps_per_unit[E_AXIS];
  
  if ( block->steps_x == 0 && block->steps_y == 0 && block->steps_z == 0 ) {
    block->millimeters = fabs(delta_mm[E_AXIS]);
  } else {
    block->millimeters = sqrt(square(delta_mm[X_AXIS]) + square(delta_mm[Y_AXIS]) + square(delta_mm[Z_AXIS]));
  }
  
  float inverse_millimeters = 1.0/block->millimeters;  // Inverse millimeters to remove multiple divides 
  
  // Calculate speed in mm/second for each axis. No divide by zero due to previous checks.
  float inverse_second = feed_rate * inverse_millimeters;
  
  block->nominal_speed = block->millimeters * inverse_second; // (mm/sec) Always > 0
  block->nominal_rate = ceil(block->step_event_count * inverse_second); // (step/sec) Always > 0

  
 

  if (block->steps_e == 0) {
        if(feed_rate<mintravelfeedrate) feed_rate=mintravelfeedrate;
  }
  else {
    	if(feed_rate<minimumfeedrate) feed_rate=minimumfeedrate;
  } 


  // slow down when de buffer starts to empty, rather than wait at the corner for a buffer refill
  int moves_queued=(block_buffer_head-block_buffer_tail + BLOCK_BUFFER_SIZE) & (BLOCK_BUFFER_SIZE - 1);
#ifdef SLOWDOWN  
  if(moves_queued < (BLOCK_BUFFER_SIZE * 0.5) && moves_queued > 1) feed_rate = feed_rate*moves_queued / (BLOCK_BUFFER_SIZE * 0.5); 
#endif

/*
  //  segment time im micro seconds
  long segment_time = lround(1000000.0/inverse_second);
  if ((blockcount>0) && (blockcount < (BLOCK_BUFFER_SIZE - 4))) {
    if (segment_time<minsegmenttime)  { // buffer is draining, add extra time.  The amount of time added increases if the buffer is still emptied more.
        segment_time=segment_time+lround(2*(minsegmenttime-segment_time)/blockcount);
    }
  }
  else {
    if (segment_time<minsegmenttime) segment_time=minsegmenttime;
  }
  //  END OF SLOW DOWN SECTION    
*/


 // Calculate speed in mm/sec for each axis
  float current_speed[4];
  for(int i=0; i < 4; i++) {
    current_speed[i] = delta_mm[i] * inverse_second;
  }

  // Limit speed per axis
  float speed_factor = 1.0; //factor <=1 do decrease speed
  for(int i=0; i < 4; i++) {
    if(abs(current_speed[i]) > max_feedrate[i])
      speed_factor = min(speed_factor, max_feedrate[i] / abs(current_speed[i]));
  }

  // Correct the speed  
  if( speed_factor < 1.0) {
//    Serial.print("speed factor : "); Serial.println(speed_factor);
    for(int i=0; i < 4; i++) {
    if(abs(current_speed[i]) > max_feedrate[i])
      speed_factor = min(speed_factor, max_feedrate[i] / abs(current_speed[i]));
 /*     
      if(speed_factor < 0.1) {
        Serial.print("speed factor : "); Serial.println(speed_factor);
        Serial.print("current_speed"); Serial.print(i); Serial.print(" : "); Serial.println(current_speed[i]);
      }
 */
  }
    for(unsigned char i=0; i < 4; 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 == 0 && block->steps_y == 0 && block->steps_z == 0) {
    block->acceleration_st = ceil(retract_acceleration * steps_per_mm); // convert to: acceleration steps/sec^2
  }
  else {
    block->acceleration_st = ceil(move_acceleration * steps_per_mm); // convert to: acceleration steps/sec^2
    // Limit acceleration per axis
    if(((float)block->acceleration_st * (float)block->steps_x / (float)block->step_event_count) > axis_steps_per_sqr_second[X_AXIS])
      block->acceleration_st = axis_steps_per_sqr_second[X_AXIS];
    if(((float)block->acceleration_st * (float)block->steps_y / (float)block->step_event_count) > axis_steps_per_sqr_second[Y_AXIS])
      block->acceleration_st = axis_steps_per_sqr_second[Y_AXIS];
    if(((float)block->acceleration_st * (float)block->steps_e / (float)block->step_event_count) > axis_steps_per_sqr_second[E_AXIS])
      block->acceleration_st = axis_steps_per_sqr_second[E_AXIS];
    if(((float)block->acceleration_st * (float)block->steps_z / (float)block->step_event_count ) > axis_steps_per_sqr_second[Z_AXIS])
      block->acceleration_st = axis_steps_per_sqr_second[Z_AXIS];
  }
  block->acceleration = block->acceleration_st / steps_per_mm;
  block->acceleration_rate = (long)((float)block->acceleration_st * 8.388608);
  
#if 0  // Use old jerk for now
  // Compute path unit vector
  double unit_vec[3];

  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,
  // colinear 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.
        vmax_junction = min(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_xy_jerk/2;  
  if(abs(current_speed[Z_AXIS]) > max_z_jerk/2) 
    vmax_junction = max_z_jerk/2;
  vmax_junction = min(vmax_junction, block->nominal_speed);

  if ((moves_queued > 1) && (previous_nominal_speed > 0.0)) {
    float jerk = sqrt(pow((current_speed[X_AXIS]-previous_speed[X_AXIS]), 2)+pow((current_speed[Y_AXIS]-previous_speed[Y_AXIS]), 2));
    if((previous_speed[X_AXIS] != 0.0) || (previous_speed[Y_AXIS] != 0.0)) {
      vmax_junction = block->nominal_speed;
    }
    if (jerk > max_xy_jerk) {
      vmax_junction *= (max_xy_jerk/jerk);
    } 
    if(abs(current_speed[Z_AXIS] - previous_speed[Z_AXIS]) > max_z_jerk) {
      vmax_junction *= (max_z_jerk/abs(current_speed[Z_AXIS] - previous_speed[Z_AXIS]));
    } 
  }
  block->max_entry_speed = vmax_junction;
    
  // Initialize block entry speed. Compute based on deceleration to user-defined MINIMUM_PLANNER_SPEED.
  double 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.
  if (block->nominal_speed <= v_allowable) { block->nominal_length_flag = true; }
  else { block->nominal_length_flag = false; }
  block->recalculate_flag = true; // Always calculate trapezoid for new block
  
  // Update previous path unit_vector and nominal speed
  memcpy(previous_speed, current_speed, sizeof(previous_speed)); // previous_speed[] = current_speed[]
  previous_nominal_speed = block->nominal_speed;
  
  #ifdef ADVANCE
    // Calculate advance rate
    if((block->steps_e == 0) || (block->steps_x == 0 && block->steps_y == 0 && block->steps_z == 0)) {
      block->advance_rate = 0;
      block->advance = 0;
    }
    else {
      long acc_dist = estimate_acceleration_distance(0, block->nominal_rate, block->acceleration_st);
      float advance = (STEPS_PER_CUBIC_MM_E * EXTRUDER_ADVANCE_K) * 
        (current_speed[E_AXIS] * current_speed[E_AXIS] * EXTRUTION_AREA * EXTRUTION_AREA)*256;
      block->advance = advance;
      if(acc_dist == 0) {
        block->advance_rate = 0;
      } 
      else {
        block->advance_rate = advance / (float)acc_dist;
      }
    }

  #endif // ADVANCE




  calculate_trapezoid_for_block(block, block->entry_speed/block->nominal_speed,
    MINIMUM_PLANNER_SPEED/block->nominal_speed);
    
  // Move buffer head
  block_buffer_head = next_buffer_head;
  
  // Update position
  memcpy(position, target, sizeof(target)); // position[] = target[]

  planner_recalculate();
  #ifdef AUTOTEMP
    getHighESpeed();
  #endif
  st_wake_up();
}

void plan_set_position(float x, float y, float z, float e)
{
  position[X_AXIS] = lround(x*axis_steps_per_unit[X_AXIS]);
  position[Y_AXIS] = lround(y*axis_steps_per_unit[Y_AXIS]);
  position[Z_AXIS] = lround(z*axis_steps_per_unit[Z_AXIS]);     
  position[E_AXIS] = lround(e*axis_steps_per_unit[E_AXIS]);  
  st_set_position(position[X_AXIS], position[Y_AXIS], position[Z_AXIS], position[E_AXIS]);
  previous_nominal_speed = 0.0; // Resets planner junction speeds. Assumes start from rest.
  previous_speed[0] = 0.0;
  previous_speed[1] = 0.0;
  previous_speed[2] = 0.0;
  previous_speed[3] = 0.0;
}

#ifdef AUTOTEMP
void getHighESpeed()
{
  static float oldt=0;
  if(!autotemp_enabled)
    return;
  if((target_temp+2) < autotemp_min)  //probably temperature set to zero.
    return; //do nothing
  
  float high=0;
  uint8_t block_index = block_buffer_tail;
  
  while(block_index != block_buffer_head)
  {
    float se=block_buffer[block_index].steps_e/float(block_buffer[block_index].step_event_count)*block_buffer[block_index].nominal_rate;
    //se; units steps/sec;
    if(se>high)
    {
      high=se;
    }
    block_index = (block_index+1) & (BLOCK_BUFFER_SIZE - 1);
  }
   
  float t=autotemp_min+high*autotemp_factor;
  
  if(t<autotemp_min)
    t=autotemp_min;
  
  if(t>autotemp_max)
    t=autotemp_max;
  
  if(oldt>t)
  {
    t=AUTOTEMP_OLDWEIGHT*oldt+(1-AUTOTEMP_OLDWEIGHT)*t;
  }
  oldt=t;
  autotemp_setpoint = (int)t;

}
#endif




// Stepper

// 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 |= (1<<OCIE1A)
#define DISABLE_STEPPER_DRIVER_INTERRUPT() TIMSK1 &= ~(1<<OCIE1A)

#ifdef ENDSTOPS_ONLY_FOR_HOMING
  #define CHECK_ENDSTOPS  if(check_endstops)
#else
  #define CHECK_ENDSTOPS
#endif

static block_t *current_block;  // A pointer to the block currently being traced

// Variables used by The Stepper Driver Interrupt
static unsigned char out_bits;        // The next stepping-bits to be output
static long counter_x,       // Counter variables for the bresenham line tracer
            counter_y, 
            counter_z,       
            counter_e;
static unsigned long step_events_completed; // The number of step events executed in the current block
static long advance_rate, advance, final_advance = 0;
static short old_advance = 0;
static short e_steps;
static unsigned char busy = false; // TRUE when SIG_OUTPUT_COMPARE1A is being serviced. Used to avoid retriggering that handler.
static long acceleration_time, deceleration_time;
//static 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;

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

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

static bool check_endstops = true;

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


//         __________________________
//        /|                        |\     _________________         ^
//       / |                        | \   /|               |\        |
//      /  |                        |  \ / |               | \       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;
  if(busy == false) 
  ENABLE_STEPPER_DRIVER_INTERRUPT();  
}

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

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 < 32) step_rate = 32;
  step_rate -= 32; // Correct for minimal speed
  
  if(step_rate >= (8*256)) // higher step rate 
  { // 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; }//(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 += ((advance >>8) - old_advance);
    old_advance = advance >>8;  
  #endif
  deceleration_time = 0;
  
  
  // step_rate to timer interval
  acc_step_rate = current_block->initial_rate;
  acceleration_time = calc_timer(acc_step_rate);
  OCR1A = acceleration_time;
  OCR1A_nominal = calc_timer(current_block->nominal_rate);
    
}

// "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 there is no current block, attempt to pop one from the buffer
  if (current_block == NULL) {
    // Anything in the buffer?
    current_block = plan_get_current_block();
    if (current_block != NULL) {
      trapezoid_generator_reset();
      counter_x = -(current_block->step_event_count >> 1);
      counter_y = counter_x;
      counter_z = counter_x;
      counter_e = counter_x;
      step_events_completed = 0;
//      #ifdef ADVANCE
//      e_steps = 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 direction en check limit switches
    if ((out_bits & (1<<X_AXIS)) != 0) {   // -direction
      WRITE(X_DIR_PIN, INVERT_X_DIR);
      count_direction[X_AXIS]=-1;
      CHECK_ENDSTOPS
      {
        #if X_MIN_PIN > -1
          bool x_min_endstop=(READ(X_MIN_PIN) != X_ENDSTOP_INVERT);
          if(x_min_endstop && old_x_min_endstop && (current_block->steps_x > 0)) {
            endstops_trigsteps[X_AXIS] = count_position[X_AXIS];
            endstop_x_hit=true;
            step_events_completed = current_block->step_event_count;
          }
          old_x_min_endstop = x_min_endstop;
        #endif
      }
    }
    else { // +direction 
      WRITE(X_DIR_PIN,!INVERT_X_DIR);
      count_direction[X_AXIS]=1;
      CHECK_ENDSTOPS 
      {
        #if X_MAX_PIN > -1
          bool x_max_endstop=(READ(X_MAX_PIN) != X_ENDSTOP_INVERT);
          if(x_max_endstop && old_x_max_endstop && (current_block->steps_x > 0)){
            endstops_trigsteps[X_AXIS] = count_position[X_AXIS];
            endstop_x_hit=true;
            step_events_completed = current_block->step_event_count;
          }
          old_x_max_endstop = x_max_endstop;
        #endif
      }
    }

    if ((out_bits & (1<<Y_AXIS)) != 0) {   // -direction
      WRITE(Y_DIR_PIN,INVERT_Y_DIR);
      count_direction[Y_AXIS]=-1;
      CHECK_ENDSTOPS
      {
        #if Y_MIN_PIN > -1
          bool y_min_endstop=(READ(Y_MIN_PIN) != Y_ENDSTOP_INVERT);
          if(y_min_endstop && old_y_min_endstop && (current_block->steps_y > 0)) {
            endstops_trigsteps[Y_AXIS] = count_position[Y_AXIS];
            endstop_y_hit=true;
            step_events_completed = current_block->step_event_count;
          }
          old_y_min_endstop = y_min_endstop;
        #endif
      }
    }
    else { // +direction
    WRITE(Y_DIR_PIN,!INVERT_Y_DIR);
      count_direction[Y_AXIS]=1;
      CHECK_ENDSTOPS
      {
        #if Y_MAX_PIN > -1
          bool y_max_endstop=(READ(Y_MAX_PIN) != Y_ENDSTOP_INVERT);
          if(y_max_endstop && old_y_max_endstop && (current_block->steps_y > 0)){
            endstops_trigsteps[Y_AXIS] = count_position[Y_AXIS];
            endstop_y_hit=true;
            step_events_completed = current_block->step_event_count;
          }
          old_y_max_endstop = y_max_endstop;
        #endif
      }
    }

    if ((out_bits & (1<<Z_AXIS)) != 0) {   // -direction
      WRITE(Z_DIR_PIN,INVERT_Z_DIR);
      count_direction[Z_AXIS]=-1;
      CHECK_ENDSTOPS
      {
        #if Z_MIN_PIN > -1
          bool z_min_endstop=(READ(Z_MIN_PIN) != Z_ENDSTOP_INVERT);
          if(z_min_endstop && old_z_min_endstop && (current_block->steps_z > 0)) {
            endstops_trigsteps[Z_AXIS] = count_position[Z_AXIS];
            endstop_z_hit=true;
            step_events_completed = current_block->step_event_count;
          }
          old_z_min_endstop = z_min_endstop;
        #endif
      }
    }
    else { // +direction
      WRITE(Z_DIR_PIN,!INVERT_Z_DIR);
      count_direction[Z_AXIS]=1;
      CHECK_ENDSTOPS
      {
        #if Z_MAX_PIN > -1
          bool z_max_endstop=(READ(Z_MAX_PIN) != Z_ENDSTOP_INVERT);
          if(z_max_endstop && old_z_max_endstop && (current_block->steps_z > 0)) {
            endstops_trigsteps[Z_AXIS] = count_position[Z_AXIS];
            endstop_z_hit=true;
            step_events_completed = current_block->step_event_count;
          }
          old_z_max_endstop = z_max_endstop;
        #endif
      }
    }

    #ifndef ADVANCE
      if ((out_bits & (1<<E_AXIS)) != 0) {  // -direction
        WRITE(E_DIR_PIN,INVERT_E_DIR);
        count_direction[E_AXIS]=-1;
      }
      else { // +direction
        WRITE(E_DIR_PIN,!INVERT_E_DIR);
        count_direction[E_AXIS]=-1;
      }
    #endif //!ADVANCE
    

    
    for(int8_t i=0; i < step_loops; i++) { // Take multiple steps per interrupt (For high speed moves) 
      //MSerial.checkRx(); // Check for serial chars. 
      
      #ifdef ADVANCE
      counter_e += current_block->steps_e;
      if (counter_e > 0) {
        counter_e -= current_block->step_event_count;
        if ((out_bits & (1<<E_AXIS)) != 0) { // - direction
          e_steps--;
        }
        else {
          e_steps++;
        }
      }    
      #endif //ADVANCE
      
      counter_x += current_block->steps_x;
      if (counter_x > 0) {
        WRITE(X_STEP_PIN, HIGH);
        counter_x -= current_block->step_event_count;
        WRITE(X_STEP_PIN, LOW);
        count_position[X_AXIS]+=count_direction[X_AXIS];   
      }

      counter_y += current_block->steps_y;
      if (counter_y > 0) {
        WRITE(Y_STEP_PIN, HIGH);
        counter_y -= current_block->step_event_count;
        WRITE(Y_STEP_PIN, LOW);
        count_position[Y_AXIS]+=count_direction[Y_AXIS];
      }

      counter_z += current_block->steps_z;
      if (counter_z > 0) {
        WRITE(Z_STEP_PIN, HIGH);
        counter_z -= current_block->step_event_count;
        WRITE(Z_STEP_PIN, LOW);
        count_position[Z_AXIS]+=count_direction[Z_AXIS];
      }

      #ifndef ADVANCE
        counter_e += current_block->steps_e;
        if (counter_e > 0) {
          WRITE(E_STEP_PIN, HIGH);
          counter_e -= current_block->step_event_count;
           WRITE(E_STEP_PIN, LOW);
          count_position[E_AXIS]+=count_direction[E_AXIS];
        }
      #endif //!ADVANCE
      step_events_completed += 1;  
      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 += ((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 += ((advance >>8) - old_advance);
        old_advance = advance >>8;  
      #endif //ADVANCE
    }
    else {
      OCR1A = OCR1A_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)
      {
        WRITE(E0_STEP_PIN, LOW);
        if (e_steps < 0) {
          WRITE(E0_DIR_PIN, INVERT_E0_DIR);
          e_steps++;
          WRITE(E0_STEP_PIN, HIGH);
        } 
        else if (e_steps > 0) {
          WRITE(E0_DIR_PIN, !INVERT_E0_DIR);
       	  e_steps--;
    	  WRITE(E0_STEP_PIN, HIGH);
  	    }
      }
    }
  }
#endif // ADVANCE

void st_init()
{
  // waveform generation = 0100 = CTC
  TCCR1B &= ~(1<<WGM13);
  TCCR1B |=  (1<<WGM12);
  TCCR1A &= ~(1<<WGM11); 
  TCCR1A &= ~(1<<WGM10);

  // output mode = 00 (disconnected)
  TCCR1A &= ~(3<<COM1A0); 
  TCCR1A &= ~(3<<COM1B0); 
  TCCR1B = (TCCR1B & ~(0x07<<CS10)) | (2<<CS10); // 2MHz timer

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

#ifdef ADVANCE
  #if defined(TCCR0A) && defined(WGM01)
    TCCR0A &= ~(1<<WGM01);
    TCCR0A &= ~(1<<WGM00);
  #endif  
  e_steps = 0;
  TIMSK0 |= (1<<OCIE0A);
#endif //ADVANCE

  #ifdef ENDSTOPS_ONLY_FOR_HOMING
    enable_endstops(false);
  #else
    enable_endstops(true);
  #endif
  
  sei();
}

// Block until all buffered steps are executed
void st_synchronize()
{
  while(blocks_queued()) {
    manage_heater();
    manage_inactivity(1);
  }   
}

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;
}


#ifdef DEBUG
void log_message(char*   message) {
  Serial.print("DEBUG"); Serial.println(message);
}

void log_bool(char* message, bool value) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": "); Serial.println(value);
}

void log_int(char* message, int value) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": "); Serial.println(value);
}

void log_long(char* message, long value) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": "); Serial.println(value);
}

void log_float(char* message, float value) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": "); Serial.println(value);
}

void log_uint(char* message, unsigned int value) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": "); Serial.println(value);
}

void log_ulong(char* message, unsigned long value) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": "); Serial.println(value);
}

void log_int_array(char* message, int value[], int array_lenght) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": {");
  for(int i=0; i < array_lenght; i++){
    Serial.print(value[i]);
    if(i != array_lenght-1) Serial.print(", ");
  }
  Serial.println("}");
}

void log_long_array(char* message, long value[], int array_lenght) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": {");
  for(int i=0; i < array_lenght; i++){
    Serial.print(value[i]);
    if(i != array_lenght-1) Serial.print(", ");
  }
  Serial.println("}");
}

void log_float_array(char* message, float value[], int array_lenght) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": {");
  for(int i=0; i < array_lenght; i++){
    Serial.print(value[i]);
    if(i != array_lenght-1) Serial.print(", ");
  }
  Serial.println("}");
}

void log_uint_array(char* message, unsigned int value[], int array_lenght) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": {");
  for(int i=0; i < array_lenght; i++){
    Serial.print(value[i]);
    if(i != array_lenght-1) Serial.print(", ");
  }
  Serial.println("}");
}

void log_ulong_array(char* message, unsigned long value[], int array_lenght) {
  Serial.print("DEBUG"); Serial.print(message); Serial.print(": {");
  for(int i=0; i < array_lenght; i++){
    Serial.print(value[i]);
    if(i != array_lenght-1) Serial.print(", ");
  }
  Serial.println("}");
}
#endif