marlin/Marlin/temperature.cpp

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

/*
 This firmware is a mashup between Sprinter and grbl.
  (https://github.com/kliment/Sprinter)
  (https://github.com/simen/grbl/tree)
 
 It has preliminary support for Matthew Roberts advance algorithm 
    http://reprap.org/pipermail/reprap-dev/2011-May/003323.html

 */


#include "Marlin.h"
#include "ultralcd.h"
#include "temperature.h"
#include "watchdog.h"

//===========================================================================
//=============================public variables============================
//===========================================================================
int target_raw[EXTRUDERS] = { 0 };
int target_raw_bed = 0;
#ifdef BED_LIMIT_SWITCHING
int target_bed_low_temp =0;  
int target_bed_high_temp =0;
#endif
int current_raw[EXTRUDERS] = { 0 };
int current_raw_bed = 0;

#ifdef PIDTEMP
  // used external
  float pid_setpoint[EXTRUDERS] = { 0.0 };
  
  float Kp=DEFAULT_Kp;
  float Ki=(DEFAULT_Ki*PID_dT);
  float Kd=(DEFAULT_Kd/PID_dT);
  #ifdef PID_ADD_EXTRUSION_RATE
    float Kc=DEFAULT_Kc;
  #endif
#endif //PIDTEMP

#ifdef PIDTEMPBED
  // used external
  float pid_setpoint_bed = { 0.0 };
  
  float bedKp=DEFAULT_bedKp;
  float bedKi=(DEFAULT_bedKi*PID_dT);
  float bedKd=(DEFAULT_bedKd/PID_dT);
#endif //PIDTEMPBED
  
  
//===========================================================================
//=============================private variables============================
//===========================================================================
static volatile bool temp_meas_ready = false;

#ifdef PIDTEMP
  //static cannot be external:
  static float temp_iState[EXTRUDERS] = { 0 };
  static float temp_dState[EXTRUDERS] = { 0 };
  static float pTerm[EXTRUDERS];
  static float iTerm[EXTRUDERS];
  static float dTerm[EXTRUDERS];
  //int output;
  static float pid_error[EXTRUDERS];
  static float temp_iState_min[EXTRUDERS];
  static float temp_iState_max[EXTRUDERS];
  // static float pid_input[EXTRUDERS];
  // static float pid_output[EXTRUDERS];
  static bool pid_reset[EXTRUDERS];
#endif //PIDTEMP
#ifdef PIDTEMPBED
  //static cannot be external:
  static float temp_iState_bed = { 0 };
  static float temp_dState_bed = { 0 };
  static float pTerm_bed;
  static float iTerm_bed;
  static float dTerm_bed;
  //int output;
  static float pid_error_bed;
  static float temp_iState_min_bed;
  static float temp_iState_max_bed;
#else //PIDTEMPBED
	static unsigned long  previous_millis_bed_heater;
#endif //PIDTEMPBED
  static unsigned char soft_pwm[EXTRUDERS];
  static unsigned char soft_pwm_bed;
  
#ifdef WATCHPERIOD
  int watch_raw[EXTRUDERS] = { -1000 }; // the first value used for all
  int watch_oldtemp[3] = {0,0,0};
  unsigned long watchmillis = 0;
#endif //WATCHPERIOD

// Init min and max temp with extreme values to prevent false errors during startup
  static int minttemp[EXTRUDERS] = { 0 };
  static int maxttemp[EXTRUDERS] = { 16383 }; // the first value used for all
  static int bed_minttemp = 0;
  static int bed_maxttemp = 16383;
  static void *heater_ttbl_map[EXTRUDERS] = { (void *)heater_0_temptable
#if EXTRUDERS > 1
                                            , (void *)heater_1_temptable
#endif
#if EXTRUDERS > 2
                                            , (void *)heater_2_temptable
#endif
#if EXTRUDERS > 3
  #error Unsupported number of extruders
#endif
  };
  static int heater_ttbllen_map[EXTRUDERS] = { heater_0_temptable_len
#if EXTRUDERS > 1
                                             , heater_1_temptable_len
#endif
#if EXTRUDERS > 2
                                             , heater_2_temptable_len
#endif
#if EXTRUDERS > 3
  #error Unsupported number of extruders
#endif
  };

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

void PID_autotune(float temp, int extruder, int ncycles)
{
  float input = 0.0;
  int cycles=0;
  bool heating = true;

  unsigned long temp_millis = millis();
  unsigned long t1=temp_millis;
  unsigned long t2=temp_millis;
  long t_high = 0;
  long t_low = 0;

  long bias, d;
  float Ku, Tu;
  float Kp, Ki, Kd;
  float max = 0, min = 10000;

	if ((extruder > EXTRUDERS)
  #if (TEMP_BED_PIN <= -1)
		||(extruder < 0)
	#endif
	){
  	SERIAL_ECHOLN("PID Autotune failed. Bad extruder number.");
  	return;
	}
	
  SERIAL_ECHOLN("PID Autotune start");
  
  disable_heater(); // switch off all heaters.

	if (extruder<0)
	{
	 	soft_pwm_bed = (MAX_BED_POWER)/2;
		bias = d = (MAX_BED_POWER)/2;
  }
	else
	{
	  soft_pwm[extruder] = (PID_MAX)/2;
		bias = d = (PID_MAX)/2;
  }




 for(;;) {

    if(temp_meas_ready == true) { // temp sample ready
      CRITICAL_SECTION_START;
      temp_meas_ready = false;
      CRITICAL_SECTION_END;
      input = (extruder<0)?analog2tempBed(current_raw_bed):analog2temp(current_raw[extruder], extruder);

      max=max(max,input);
      min=min(min,input);
      if(heating == true && input > temp) {
        if(millis() - t2 > 5000) { 
          heating=false;
					if (extruder<0)
						soft_pwm_bed = (bias - d) >> 1;
					else
						soft_pwm[extruder] = (bias - d) >> 1;
          t1=millis();
          t_high=t1 - t2;
          max=temp;
        }
      }
      if(heating == false && input < temp) {
        if(millis() - t1 > 5000) {
          heating=true;
          t2=millis();
          t_low=t2 - t1;
          if(cycles > 0) {
            bias += (d*(t_high - t_low))/(t_low + t_high);
            bias = constrain(bias, 20 ,(extruder<0?(MAX_BED_POWER):(PID_MAX))-20);
            if(bias > (extruder<0?(MAX_BED_POWER):(PID_MAX))/2) d = (extruder<0?(MAX_BED_POWER):(PID_MAX)) - 1 - bias;
            else d = bias;

            SERIAL_PROTOCOLPGM(" bias: "); SERIAL_PROTOCOL(bias);
            SERIAL_PROTOCOLPGM(" d: "); SERIAL_PROTOCOL(d);
            SERIAL_PROTOCOLPGM(" min: "); SERIAL_PROTOCOL(min);
            SERIAL_PROTOCOLPGM(" max: "); SERIAL_PROTOCOLLN(max);
            if(cycles > 2) {
              Ku = (4.0*d)/(3.14159*(max-min)/2.0);
              Tu = ((float)(t_low + t_high)/1000.0);
              SERIAL_PROTOCOLPGM(" Ku: "); SERIAL_PROTOCOL(Ku);
              SERIAL_PROTOCOLPGM(" Tu: "); SERIAL_PROTOCOLLN(Tu);
              Kp = 0.6*Ku;
              Ki = 2*Kp/Tu;
              Kd = Kp*Tu/8;
              SERIAL_PROTOCOLLNPGM(" Clasic PID ")
              SERIAL_PROTOCOLPGM(" Kp: "); SERIAL_PROTOCOLLN(Kp);
              SERIAL_PROTOCOLPGM(" Ki: "); SERIAL_PROTOCOLLN(Ki);
              SERIAL_PROTOCOLPGM(" Kd: "); SERIAL_PROTOCOLLN(Kd);
              /*
              Kp = 0.33*Ku;
              Ki = Kp/Tu;
              Kd = Kp*Tu/3;
              SERIAL_PROTOCOLLNPGM(" Some overshoot ")
              SERIAL_PROTOCOLPGM(" Kp: "); SERIAL_PROTOCOLLN(Kp);
              SERIAL_PROTOCOLPGM(" Ki: "); SERIAL_PROTOCOLLN(Ki);
              SERIAL_PROTOCOLPGM(" Kd: "); SERIAL_PROTOCOLLN(Kd);
              Kp = 0.2*Ku;
              Ki = 2*Kp/Tu;
              Kd = Kp*Tu/3;
              SERIAL_PROTOCOLLNPGM(" No overshoot ")
              SERIAL_PROTOCOLPGM(" Kp: "); SERIAL_PROTOCOLLN(Kp);
              SERIAL_PROTOCOLPGM(" Ki: "); SERIAL_PROTOCOLLN(Ki);
              SERIAL_PROTOCOLPGM(" Kd: "); SERIAL_PROTOCOLLN(Kd);
              */
            }
          }
					if (extruder<0)
						soft_pwm_bed = (bias + d) >> 1;
					else
						soft_pwm[extruder] = (bias + d) >> 1;
          cycles++;
          min=temp;
        }
      } 
    }
    if(input > (temp + 20)) {
      SERIAL_PROTOCOLLNPGM("PID Autotune failed! Temperature to high");
      return;
    }
    if(millis() - temp_millis > 2000) {
			int p;
			if (extruder<0){
	      p=soft_pwm_bed;       
	      SERIAL_PROTOCOLPGM("ok B:");
			}else{
	      p=soft_pwm[extruder];       
	      SERIAL_PROTOCOLPGM("ok T:");
			}
			
      SERIAL_PROTOCOL(input);   
      SERIAL_PROTOCOLPGM(" @:");
      SERIAL_PROTOCOLLN(p);       

      temp_millis = millis();
    }
    if(((millis() - t1) + (millis() - t2)) > (10L*60L*1000L*2L)) {
      SERIAL_PROTOCOLLNPGM("PID Autotune failed! timeout");
      return;
    }
    if(cycles > ncycles) {
      SERIAL_PROTOCOLLNPGM("PID Autotune finished ! Place the Kp, Ki and Kd constants in the configuration.h");
      return;
    }
    LCD_STATUS;
  }
}

void updatePID()
{
#ifdef PIDTEMP
  for(int e = 0; e < EXTRUDERS; e++) { 
     temp_iState_max[e] = PID_INTEGRAL_DRIVE_MAX / Ki;  
  }
#endif
#ifdef PIDTEMPBED
  temp_iState_max_bed = PID_INTEGRAL_DRIVE_MAX / bedKi;  
#endif
}
  
int getHeaterPower(int heater) {
	if (heater<0)
		return soft_pwm_bed;
  return soft_pwm[heater];
}

void manage_heater()
{
  float pid_input;
  float pid_output;

  if(temp_meas_ready != true)   //better readability
    return; 

  //Reset the watchdog after we know we have a temperature measurement.
  watchdog_reset();

  CRITICAL_SECTION_START;
  temp_meas_ready = false;
  CRITICAL_SECTION_END;

  for(int e = 0; e < EXTRUDERS; e++) 
  {

  #ifdef PIDTEMP
    pid_input = analog2temp(current_raw[e], e);

    #ifndef PID_OPENLOOP
        pid_error[e] = pid_setpoint[e] - pid_input;
        if(pid_error[e] > 10) {
          pid_output = PID_MAX;
          pid_reset[e] = true;
        }
        else if(pid_error[e] < -10) {
          pid_output = 0;
          pid_reset[e] = true;
        }
        else {
          if(pid_reset[e] == true) {
            temp_iState[e] = 0.0;
            pid_reset[e] = false;
          }
          pTerm[e] = Kp * pid_error[e];
          temp_iState[e] += pid_error[e];
          temp_iState[e] = constrain(temp_iState[e], temp_iState_min[e], temp_iState_max[e]);
          iTerm[e] = Ki * temp_iState[e];

          //K1 defined in Configuration.h in the PID settings
          #define K2 (1.0-K1)
          dTerm[e] = (Kd * (pid_input - temp_dState[e]))*K2 + (K1 * dTerm[e]);
          temp_dState[e] = pid_input;

          pid_output = constrain(pTerm[e] + iTerm[e] - dTerm[e], 0, PID_MAX);
        }
    #else 
          pid_output = constrain(pid_setpoint[e], 0, PID_MAX);
    #endif //PID_OPENLOOP
    #ifdef PID_DEBUG
    SERIAL_ECHOLN(" PIDDEBUG "<<e<<": Input "<<pid_input<<" Output "<<pid_output" pTerm "<<pTerm[e]<<" iTerm "<<iTerm[e]<<" dTerm "<<dTerm[e]);  
    #endif //PID_DEBUG
  #else /* PID off */
    pid_output = 0;
    if(current_raw[e] < target_raw[e]) {
      pid_output = PID_MAX;
    }
  #endif

    // Check if temperature is within the correct range
    if((current_raw[e] > minttemp[e]) && (current_raw[e] < maxttemp[e])) 
    {
      soft_pwm[e] = (int)pid_output >> 1;
    }
    else {
      soft_pwm[e] = 0;
    }
  } // End extruder for loop
  
  #ifdef WATCHPERIOD
    if(watchmillis && millis() - watchmillis > WATCHPERIOD){
        if(watch_oldtemp[0] >= degHotend(active_extruder)){
            setTargetHotend(0,active_extruder);
            LCD_MESSAGEPGM("Heating failed");
            SERIAL_ECHO_START;
            SERIAL_ECHOLN("Heating failed");
        }else{
            watchmillis = 0;
        }
    }
  #endif
  

		#ifndef PIDTEMPBED
  if(millis() - previous_millis_bed_heater < BED_CHECK_INTERVAL)
    return;
  previous_millis_bed_heater = millis();
    #endif

  #if TEMP_BED_PIN > -1
  
		#ifdef PIDTEMPBED
    pid_input = analog2tempBed(current_raw_bed);

    #ifndef PID_OPENLOOP
		  pid_error_bed = pid_setpoint_bed - pid_input;
		  pTerm_bed = bedKp * pid_error_bed;
		  temp_iState_bed += pid_error_bed;
		  temp_iState_bed = constrain(temp_iState_bed, temp_iState_min_bed, temp_iState_max_bed);
		  iTerm_bed = bedKi * temp_iState_bed;

		  //K1 defined in Configuration.h in the PID settings
		  #define K2 (1.0-K1)
		  dTerm_bed= (bedKd * (pid_input - temp_dState_bed))*K2 + (K1 * dTerm_bed);
		  temp_dState_bed = pid_input;

		  pid_output = constrain(pTerm_bed + iTerm_bed - dTerm_bed, 0, MAX_BED_POWER);

    #else 
      pid_output = constrain(pid_setpoint_bed, 0, MAX_BED_POWER);
    #endif //PID_OPENLOOP

	  if((current_raw_bed > bed_minttemp) && (current_raw_bed < bed_maxttemp)) 
	  {
	    soft_pwm_bed = (int)pid_output >> 1;
	  }
	  else {
	    soft_pwm_bed = 0;
	  }

    #elif not defined BED_LIMIT_SWITCHING
      // Check if temperature is within the correct range
      if((current_raw_bed > bed_minttemp) && (current_raw_bed < bed_maxttemp)) {
        if(current_raw_bed >= target_raw_bed)
        {
					soft_pwm_bed = 0;
        }
        else 
        {
					soft_pwm_bed = MAX_BED_POWER>>1;
        }
      }
      else {
					soft_pwm_bed = 0;
        WRITE(HEATER_BED_PIN,LOW);
      }
    #else //#ifdef BED_LIMIT_SWITCHING
      // Check if temperature is within the correct band
      if((current_raw_bed > bed_minttemp) && (current_raw_bed < bed_maxttemp)) {
        if(current_raw_bed > target_bed_high_temp)
        {
					soft_pwm_bed = 0;
        }
        else 
          if(current_raw_bed <= target_bed_low_temp)
        {
					soft_pwm_bed = MAX_BED_POWER>>1;
        }
      }
      else {
					soft_pwm_bed = 0;
        WRITE(HEATER_BED_PIN,LOW);
      }
    #endif
  #endif
}

#define PGM_RD_W(x)   (short)pgm_read_word(&x)
// Takes hot end temperature value as input and returns corresponding raw value. 
// For a thermistor, it uses the RepRap thermistor temp table.
// This is needed because PID in hydra firmware hovers around a given analog value, not a temp value.
// This function is derived from inversing the logic from a portion of getTemperature() in FiveD RepRap firmware.
int temp2analog(int celsius, uint8_t e) {
  if(e >= EXTRUDERS)
  {
      SERIAL_ERROR_START;
      SERIAL_ERROR((int)e);
      SERIAL_ERRORLNPGM(" - Invalid extruder number!");
      kill();
  }
  #ifdef HEATER_0_USES_MAX6675
    if (e == 0)
    {
      return celsius * 4;
    }
  #endif
  if(heater_ttbl_map[e] != 0)
  {
    int raw = 0;
    byte i;
    short (*tt)[][2] = (short (*)[][2])(heater_ttbl_map[e]);

    for (i=1; i<heater_ttbllen_map[e]; i++)
    {
      if (PGM_RD_W((*tt)[i][1]) < celsius)
      {
        raw = PGM_RD_W((*tt)[i-1][0]) + 
          (celsius - PGM_RD_W((*tt)[i-1][1])) * 
          (PGM_RD_W((*tt)[i][0]) - PGM_RD_W((*tt)[i-1][0])) /
          (PGM_RD_W((*tt)[i][1]) - PGM_RD_W((*tt)[i-1][1]));  
        break;
      }
    }

    // Overflow: Set to last value in the table
    if (i == heater_ttbllen_map[e]) raw = PGM_RD_W((*tt)[i-1][0]);

    return (1023 * OVERSAMPLENR) - raw;
  }
  return ((celsius-TEMP_SENSOR_AD595_OFFSET)/TEMP_SENSOR_AD595_GAIN) * (1024.0 / (5.0 * 100.0) ) * OVERSAMPLENR;
}

// Takes bed temperature value as input and returns corresponding raw value. 
// For a thermistor, it uses the RepRap thermistor temp table.
// This is needed because PID in hydra firmware hovers around a given analog value, not a temp value.
// This function is derived from inversing the logic from a portion of getTemperature() in FiveD RepRap firmware.
int temp2analogBed(int celsius) {
#ifdef BED_USES_THERMISTOR
    int raw = 0;
    byte i;
    
    for (i=1; i<bedtemptable_len; i++)
    {
      if (PGM_RD_W(bedtemptable[i][1]) < celsius)
      {
        raw = PGM_RD_W(bedtemptable[i-1][0]) + 
          (celsius - PGM_RD_W(bedtemptable[i-1][1])) * 
          (PGM_RD_W(bedtemptable[i][0]) - PGM_RD_W(bedtemptable[i-1][0])) /
          (PGM_RD_W(bedtemptable[i][1]) - PGM_RD_W(bedtemptable[i-1][1]));
      
        break;
      }
    }

    // Overflow: Set to last value in the table
    if (i == bedtemptable_len) raw = PGM_RD_W(bedtemptable[i-1][0]);

    return (1023 * OVERSAMPLENR) - raw;
#elif defined BED_USES_AD595
    return lround(((celsius-TEMP_SENSOR_AD595_OFFSET)/TEMP_SENSOR_AD595_GAIN) * (1024.0 * OVERSAMPLENR/ (5.0 * 100.0) ) );
#else
    return 0;
#endif
}

// Derived from RepRap FiveD extruder::getTemperature()
// For hot end temperature measurement.
float analog2temp(int raw, uint8_t e) {
  if(e >= EXTRUDERS)
  {
      SERIAL_ERROR_START;
      SERIAL_ERROR((int)e);
      SERIAL_ERRORLNPGM(" - Invalid extruder number !");
      kill();
  } 
  #ifdef HEATER_0_USES_MAX6675
    if (e == 0)
    {
      return 0.25 * raw;
    }
  #endif

  if(heater_ttbl_map[e] != 0)
  {
    float celsius = 0;
    byte i;  
    short (*tt)[][2] = (short (*)[][2])(heater_ttbl_map[e]);

    raw = (1023 * OVERSAMPLENR) - raw;
    for (i=1; i<heater_ttbllen_map[e]; i++)
    {
      if (PGM_RD_W((*tt)[i][0]) > raw)
      {
        celsius = PGM_RD_W((*tt)[i-1][1]) + 
          (raw - PGM_RD_W((*tt)[i-1][0])) * 
          (float)(PGM_RD_W((*tt)[i][1]) - PGM_RD_W((*tt)[i-1][1])) /
          (float)(PGM_RD_W((*tt)[i][0]) - PGM_RD_W((*tt)[i-1][0]));
        break;
      }
    }

    // Overflow: Set to last value in the table
    if (i == heater_ttbllen_map[e]) celsius = PGM_RD_W((*tt)[i-1][1]);

    return celsius;
  }
  return ((raw * ((5.0 * 100.0) / 1024.0) / OVERSAMPLENR) * TEMP_SENSOR_AD595_GAIN) + TEMP_SENSOR_AD595_OFFSET;
}

// Derived from RepRap FiveD extruder::getTemperature()
// For bed temperature measurement.
float analog2tempBed(int raw) {
  #ifdef BED_USES_THERMISTOR
    float celsius = 0;
    byte i;

    raw = (1023 * OVERSAMPLENR) - raw;

    for (i=1; i<bedtemptable_len; i++)
    {
      if (PGM_RD_W(bedtemptable[i][0]) > raw)
      {
        celsius  = PGM_RD_W(bedtemptable[i-1][1]) + 
          (raw - PGM_RD_W(bedtemptable[i-1][0])) * 
          (float)(PGM_RD_W(bedtemptable[i][1]) - PGM_RD_W(bedtemptable[i-1][1])) /
          (float)(PGM_RD_W(bedtemptable[i][0]) - PGM_RD_W(bedtemptable[i-1][0]));
        break;
      }
    }

    // Overflow: Set to last value in the table
    if (i == bedtemptable_len) celsius = PGM_RD_W(bedtemptable[i-1][1]);

    return celsius;
  #elif defined BED_USES_AD595
    return ((raw * ((5.0 * 100.0) / 1024.0) / OVERSAMPLENR) * TEMP_SENSOR_AD595_GAIN) + TEMP_SENSOR_AD595_OFFSET;
  #else
    return 0;
  #endif
}

void tp_init()
{
  // Finish init of mult extruder arrays 
  for(int e = 0; e < EXTRUDERS; e++) {
    // populate with the first value 
#ifdef WATCHPERIOD
    watch_raw[e] = watch_raw[0];
#endif
    maxttemp[e] = maxttemp[0];
#ifdef PIDTEMP
    temp_iState_min[e] = 0.0;
    temp_iState_max[e] = PID_INTEGRAL_DRIVE_MAX / Ki;
#endif //PIDTEMP
#ifdef PIDTEMPBED
    temp_iState_min_bed = 0.0;
    temp_iState_max_bed = PID_INTEGRAL_DRIVE_MAX / bedKi;
#endif //PIDTEMPBED
  }

  #if (HEATER_0_PIN > -1) 
    SET_OUTPUT(HEATER_0_PIN);
  #endif  
  #if (HEATER_1_PIN > -1) 
    SET_OUTPUT(HEATER_1_PIN);
  #endif  
  #if (HEATER_2_PIN > -1) 
    SET_OUTPUT(HEATER_2_PIN);
  #endif  
  #if (HEATER_BED_PIN > -1) 
    SET_OUTPUT(HEATER_BED_PIN);
  #endif  
  #if (FAN_PIN > -1) 
    SET_OUTPUT(FAN_PIN);
    #ifdef FAST_PWM_FAN
    setPwmFrequency(FAN_PIN, 1); // No prescaling. Pwm frequency = F_CPU/256/8
    #endif
  #endif  

  #ifdef HEATER_0_USES_MAX6675
    #ifndef SDSUPPORT
      SET_OUTPUT(MAX_SCK_PIN);
      WRITE(MAX_SCK_PIN,0);
    
      SET_OUTPUT(MAX_MOSI_PIN);
      WRITE(MAX_MOSI_PIN,1);
    
      SET_INPUT(MAX_MISO_PIN);
      WRITE(MAX_MISO_PIN,1);
    #endif
    
    SET_OUTPUT(MAX6675_SS);
    WRITE(MAX6675_SS,1);
  #endif

  // Set analog inputs
  ADCSRA = 1<<ADEN | 1<<ADSC | 1<<ADIF | 0x07;
  DIDR0 = 0;
  #ifdef DIDR2
    DIDR2 = 0;
  #endif
  #if (TEMP_0_PIN > -1)
    #if TEMP_0_PIN < 8
       DIDR0 |= 1 << TEMP_0_PIN; 
    #else
       DIDR2 |= 1<<(TEMP_0_PIN - 8); 
    #endif
  #endif
  #if (TEMP_1_PIN > -1)
    #if TEMP_1_PIN < 8
       DIDR0 |= 1<<TEMP_1_PIN; 
    #else
       DIDR2 |= 1<<(TEMP_1_PIN - 8); 
    #endif
  #endif
  #if (TEMP_2_PIN > -1)
    #if TEMP_2_PIN < 8
       DIDR0 |= 1 << TEMP_2_PIN; 
    #else
       DIDR2 = 1<<(TEMP_2_PIN - 8); 
    #endif
  #endif
  #if (TEMP_BED_PIN > -1)
    #if TEMP_BED_PIN < 8
       DIDR0 |= 1<<TEMP_BED_PIN; 
    #else
       DIDR2 |= 1<<(TEMP_BED_PIN - 8); 
    #endif
  #endif
  
  // Use timer0 for temperature measurement
  // Interleave temperature interrupt with millies interrupt
  OCR0B = 128;
  TIMSK0 |= (1<<OCIE0B);  
  
  // Wait for temperature measurement to settle
  delay(250);

#ifdef HEATER_0_MINTEMP
  minttemp[0] = temp2analog(HEATER_0_MINTEMP, 0);
#endif //MINTEMP
#ifdef HEATER_0_MAXTEMP
  maxttemp[0] = temp2analog(HEATER_0_MAXTEMP, 0);
#endif //MAXTEMP

#if (EXTRUDERS > 1) && defined(HEATER_1_MINTEMP)
  minttemp[1] = temp2analog(HEATER_1_MINTEMP, 1);
#endif // MINTEMP 1
#if (EXTRUDERS > 1) && defined(HEATER_1_MAXTEMP)
  maxttemp[1] = temp2analog(HEATER_1_MAXTEMP, 1);
#endif //MAXTEMP 1

#if (EXTRUDERS > 2) && defined(HEATER_2_MINTEMP)
  minttemp[2] = temp2analog(HEATER_2_MINTEMP, 2);
#endif //MINTEMP 2
#if (EXTRUDERS > 2) && defined(HEATER_2_MAXTEMP)
  maxttemp[2] = temp2analog(HEATER_2_MAXTEMP, 2);
#endif //MAXTEMP 2

#ifdef BED_MINTEMP
  bed_minttemp = temp2analogBed(BED_MINTEMP);
#endif //BED_MINTEMP
#ifdef BED_MAXTEMP
  bed_maxttemp = temp2analogBed(BED_MAXTEMP);
#endif //BED_MAXTEMP
}



void setWatch() 
{  
#ifdef WATCHPERIOD
  int t = 0;
  for (int e = 0; e < EXTRUDERS; e++)
  {
    if(isHeatingHotend(e))
    watch_oldtemp[0] = degHotend(0);
    {
      t = max(t,millis());
      watch_raw[e] = current_raw[e];
    } 
  }
  watchmillis = t;
#endif 
}


void disable_heater()
{
  for(int i=0;i<EXTRUDERS;i++)
    setTargetHotend(0,i);
  setTargetBed(0);
  #if TEMP_0_PIN > -1
  target_raw[0]=0;
  soft_pwm[0]=0;
   #if HEATER_0_PIN > -1  
     WRITE(HEATER_0_PIN,LOW);
   #endif
  #endif
     
  #if TEMP_1_PIN > -1
    target_raw[1]=0;
    soft_pwm[1]=0;
    #if HEATER_1_PIN > -1 
      WRITE(HEATER_1_PIN,LOW);
    #endif
  #endif
      
  #if TEMP_2_PIN > -1
    target_raw[2]=0;
    soft_pwm[2]=0;
    #if HEATER_2_PIN > -1  
      WRITE(HEATER_2_PIN,LOW);
    #endif
  #endif 

  #if TEMP_BED_PIN > -1
    target_raw_bed=0;
    soft_pwm_bed=0;
    #if HEATER_BED_PIN > -1  
      WRITE(HEATER_BED_PIN,LOW);
    #endif
  #endif 
}

void max_temp_error(uint8_t e) {
  disable_heater();
  if(IsStopped() == false) {
    SERIAL_ERROR_START;
    SERIAL_ERRORLN((int)e);
    SERIAL_ERRORLNPGM(": Extruder switched off. MAXTEMP triggered !");
  }
}

void min_temp_error(uint8_t e) {
  disable_heater();
  if(IsStopped() == false) {
    SERIAL_ERROR_START;
    SERIAL_ERRORLN((int)e);
    SERIAL_ERRORLNPGM(": Extruder switched off. MINTEMP triggered !");
  }
}

void bed_max_temp_error(void) {
#if HEATER_BED_PIN > -1
  WRITE(HEATER_BED_PIN, 0);
#endif
  if(IsStopped() == false) {
    SERIAL_ERROR_START;
    SERIAL_ERRORLNPGM("Temperature heated bed switched off. MAXTEMP triggered !!");
  }
}

#define HEAT_INTERVAL 250
#ifdef HEATER_0_USES_MAX6675
long max6675_previous_millis = -HEAT_INTERVAL;
int max6675_temp = 2000;

int read_max6675()
{
  if (millis() - max6675_previous_millis < HEAT_INTERVAL) 
    return max6675_temp;
  
  max6675_previous_millis = millis();
  max6675_temp = 0;
    
  #ifdef	PRR
    PRR &= ~(1<<PRSPI);
  #elif defined PRR0
    PRR0 &= ~(1<<PRSPI);
  #endif
  
  SPCR = (1<<MSTR) | (1<<SPE) | (1<<SPR0);
  
  // enable TT_MAX6675
  WRITE(MAX6675_SS, 0);
  
  // ensure 100ns delay - a bit extra is fine
  delay(1);
  
  // read MSB
  SPDR = 0;
  for (;(SPSR & (1<<SPIF)) == 0;);
  max6675_temp = SPDR;
  max6675_temp <<= 8;
  
  // read LSB
  SPDR = 0;
  for (;(SPSR & (1<<SPIF)) == 0;);
  max6675_temp |= SPDR;
  
  // disable TT_MAX6675
  WRITE(MAX6675_SS, 1);

  if (max6675_temp & 4) 
  {
    // thermocouple open
    max6675_temp = 2000;
  }
  else 
  {
    max6675_temp = max6675_temp >> 3;
  }

  return max6675_temp;
}
#endif


// Timer 0 is shared with millies
ISR(TIMER0_COMPB_vect)
{
  //these variables are only accesible from the ISR, but static, so they don't loose their value
  static unsigned char temp_count = 0;
  static unsigned long raw_temp_0_value = 0;
  static unsigned long raw_temp_1_value = 0;
  static unsigned long raw_temp_2_value = 0;
  static unsigned long raw_temp_bed_value = 0;
  static unsigned char temp_state = 0;
  static unsigned char pwm_count = 1;
  static unsigned char soft_pwm_0;
  static unsigned char soft_pwm_1;
  static unsigned char soft_pwm_2;
  static unsigned char soft_pwm_b;
  
  if(pwm_count == 0){
    soft_pwm_0 = soft_pwm[0];
    if(soft_pwm_0 > 0) WRITE(HEATER_0_PIN,1);
    #if EXTRUDERS > 1
    soft_pwm_1 = soft_pwm[1];
    if(soft_pwm_1 > 0) WRITE(HEATER_1_PIN,1);
    #endif
    #if EXTRUDERS > 2
    soft_pwm_2 = soft_pwm[2];
    if(soft_pwm_2 > 0) WRITE(HEATER_2_PIN,1);
    #endif
    #if HEATER_BED_PIN > -1
    soft_pwm_b = soft_pwm_bed;
    if(soft_pwm_b > 0) WRITE(HEATER_BED_PIN,1);
    #endif
  }
  if(soft_pwm_0 <= pwm_count) WRITE(HEATER_0_PIN,0);
  #if EXTRUDERS > 1
  if(soft_pwm_1 <= pwm_count) WRITE(HEATER_1_PIN,0);
  #endif
  #if EXTRUDERS > 2
  if(soft_pwm_2 <= pwm_count) WRITE(HEATER_2_PIN,0);
  #endif
  #if HEATER_BED_PIN > -1
  if(soft_pwm_b <= pwm_count) WRITE(HEATER_BED_PIN,0);
  #endif
  
  pwm_count++;
  pwm_count &= 0x7f;
  
  switch(temp_state) {
    case 0: // Prepare TEMP_0
      #if (TEMP_0_PIN > -1)
        #if TEMP_0_PIN > 7
          ADCSRB = 1<<MUX5;
        #else
          ADCSRB = 0;
        #endif
        ADMUX = ((1 << REFS0) | (TEMP_0_PIN & 0x07));
        ADCSRA |= 1<<ADSC; // Start conversion
      #endif
      #ifdef ULTIPANEL
        buttons_check();
      #endif
      temp_state = 1;
      break;
    case 1: // Measure TEMP_0
      #if (TEMP_0_PIN > -1)
        raw_temp_0_value += ADC;
      #endif
      #ifdef HEATER_0_USES_MAX6675 // TODO remove the blocking
        raw_temp_0_value = read_max6675();
      #endif
      temp_state = 2;
      break;
    case 2: // Prepare TEMP_BED
      #if (TEMP_BED_PIN > -1)
        #if TEMP_BED_PIN > 7
          ADCSRB = 1<<MUX5;
        #else
          ADCSRB = 0;
        #endif
        ADMUX = ((1 << REFS0) | (TEMP_BED_PIN & 0x07));
        ADCSRA |= 1<<ADSC; // Start conversion
      #endif
      #ifdef ULTIPANEL
        buttons_check();
      #endif
      temp_state = 3;
      break;
    case 3: // Measure TEMP_BED
      #if (TEMP_BED_PIN > -1)
        raw_temp_bed_value += ADC;
      #endif
      temp_state = 4;
      break;
    case 4: // Prepare TEMP_1
      #if (TEMP_1_PIN > -1)
        #if TEMP_1_PIN > 7
          ADCSRB = 1<<MUX5;
        #else
          ADCSRB = 0;
        #endif
        ADMUX = ((1 << REFS0) | (TEMP_1_PIN & 0x07));
        ADCSRA |= 1<<ADSC; // Start conversion
      #endif
      #ifdef ULTIPANEL
        buttons_check();
      #endif
      temp_state = 5;
      break;
    case 5: // Measure TEMP_1
      #if (TEMP_1_PIN > -1)
        raw_temp_1_value += ADC;
      #endif
      temp_state = 6;
      break;
    case 6: // Prepare TEMP_2
      #if (TEMP_2_PIN > -1)
        #if TEMP_2_PIN > 7
          ADCSRB = 1<<MUX5;
        #else
          ADCSRB = 0;
        #endif
        ADMUX = ((1 << REFS0) | (TEMP_2_PIN & 0x07));
        ADCSRA |= 1<<ADSC; // Start conversion
      #endif
      #ifdef ULTIPANEL
        buttons_check();
      #endif
      temp_state = 7;
      break;
    case 7: // Measure TEMP_2
      #if (TEMP_2_PIN > -1)
        raw_temp_2_value += ADC;
      #endif
      temp_state = 0;
      temp_count++;
      break;
//    default:
//      SERIAL_ERROR_START;
//      SERIAL_ERRORLNPGM("Temp measurement error!");
//      break;
  }
    
  if(temp_count >= 16) // 8 ms * 16 = 128ms.
  {
    #if defined(HEATER_0_USES_AD595) || defined(HEATER_0_USES_MAX6675)
      current_raw[0] = raw_temp_0_value;
    #else
      current_raw[0] = 16383 - raw_temp_0_value;
    #endif

#if EXTRUDERS > 1    
    #ifdef HEATER_1_USES_AD595
      current_raw[1] = raw_temp_1_value;
    #else
      current_raw[1] = 16383 - raw_temp_1_value;
    #endif
#endif
    
#if EXTRUDERS > 2
    #ifdef HEATER_2_USES_AD595
      current_raw[2] = raw_temp_2_value;
    #else
      current_raw[2] = 16383 - raw_temp_2_value;
    #endif
#endif
    
    #ifdef BED_USES_AD595
      current_raw_bed = raw_temp_bed_value;
    #else
      current_raw_bed = 16383 - raw_temp_bed_value;
    #endif
    
    temp_meas_ready = true;
    temp_count = 0;
    raw_temp_0_value = 0;
    raw_temp_1_value = 0;
    raw_temp_2_value = 0;
    raw_temp_bed_value = 0;

    for(unsigned char e = 0; e < EXTRUDERS; e++) {
       if(current_raw[e] >= maxttemp[e]) {
          target_raw[e] = 0;
          max_temp_error(e);
          #ifndef BOGUS_TEMPERATURE_FAILSAFE_OVERRIDE
          {
            Stop();;
          }
          #endif
       }
       if(current_raw[e] <= minttemp[e]) {
          target_raw[e] = 0;
          min_temp_error(e);
          #ifndef BOGUS_TEMPERATURE_FAILSAFE_OVERRIDE
          {
            Stop();
          }
          #endif
       }
    }
  
#if defined(BED_MAXTEMP) && (HEATER_BED_PIN > -1)
    if(current_raw_bed >= bed_maxttemp) {
       target_raw_bed = 0;
       bed_max_temp_error();
       Stop();
    }
#endif
  }
}