/*    Max6675 Module  ==>   Arduino

 *    CS              ==>     D9

 *    SO              ==>     D8

 *    SCK             ==>     D10

 *    Vcc             ==>     Vcc (5v)

 *    Gnd             ==>     Gnd      */

#include <SPI.h>

#define MAX6675_CS   9

#define MAX6675_SO   8

#define MAX6675_SCK  10

void setup() {

 Serial.begin(9600);

}

void loop() {

  float temperature_read = readThermocouple();

  Serial.print("TEMPERATURE: ");

  Serial.print(temperature_read);

  Serial.println(" Do C");    

  delay(300);

}

double readThermocouple() {

  uint16_t v;

  pinMode(MAX6675_CS, OUTPUT);

  pinMode(MAX6675_SO, INPUT);

  pinMode(MAX6675_SCK, OUTPUT);

  digitalWrite(MAX6675_CS, LOW);

  delay(1);

  // Read in 16 bits,

  //  15    = 0 always

  //  14..2 = 0.25 degree counts MSB First

  //  2     = 1 if thermocouple is open circuit  

  //  1..0  = uninteresting status

  v = shiftIn(MAX6675_SO, MAX6675_SCK, MSBFIRST);

  v <<= 8;

  v |= shiftIn(MAX6675_SO, MAX6675_SCK, MSBFIRST);

  digitalWrite(MAX6675_CS, HIGH);

  if (v & 0x4)

  {    

    // Bit 2 indicates if the thermocouple is disconnected

    return NAN;    

  }

  // The lower three bits (0,1,2) are discarded status bits

  v >>= 3;

  // The remaining bits are the number of 0.25 degree (C) counts

  return v*0.25;

}