Rewrite of the important parts of the Adafruit MAX31855 library for the Spark.io platform

copy_these_methods_to_your_app.c

// these methods should be fully "functional" in that they 
// work, they have no known "side effects", and that they
// will return the same outputs given the same inputs (unless
// the temperature at the thermocouple changes, of course.)

// in setup() add these lines:
//    SPI.setBitOrder(MSBFIRST);
//    SPI.setDataMode(SPI_MODE0);
//    SPI.begin();
// then use these methods in your application.

int32_t readThermocouple() {
  // thermocouple data is returned as a 32-bit MSB number, like: 
  // 00000001101001000001101010100000
  // 
  // 00000001101001                    14-bit thermocouple data.  2's compliment.
  //               0                   reserved
  //                0                  fault bit, if set, one of the three bits at the end will be set.
  //                 000110101010      12-bit internal temp reading.  2's compliment.
  //                             0     reserved
  //                              0    thermocouple is shorted to VCC
  //                               0   thermocouple is shorted to GND
  //                                0  thermocouple is open circuit

  // the 14-bit thermocouple temp reading is the temperature in C multiplied by 4.
  // Divide it by 4.0 to get quarter degree C precision, or just bitshift right by
  // two to get whole numbers.
  
  // the 12-bit internal temperature of the amplifier is the temperature of the 
  // MAX31855 multiplied by 16.  Divide by 16.0 to get 16th degree C precision, or 
  // bitshift right by 4 if you only care about whole degrees C.  

  int32_t d = 0;

  digitalWrite(A2, LOW);

  for (int bit = 8; bit; bit >>= 1) { //transfer 4 bytes, magically.
    d <<= 8;
    d |= SPI.transfer(0xFF);
  }

  digitalWrite(A2, HIGH);
  
  return d;
}

boolean isError(int thermocoupleReading) {
    return thermocoupleReading >> 16 & 1;
}