text: //
  //    FILE: MAX31855.cpp
  //  AUTHOR: Rob Tillaart
  // VERSION: 0.2.4
  // PURPOSE: Arduino library for MAX31855 chip for K type thermocouple
  //    DATE: 2014-01-01
  //     URL: https://github.com/RobTillaart/MAX31855_RT
  //
  //  HISTORY:
  //  0.2.4  2020-12-30  arduinoCI, unit test
  //  0.2.3  2020-08-30  fix #8 support hardware SPI + example
  //  0.2.2  2020-08-30  fix#9 + fix failing examples + minor refactor
  //  0.2.1  2020-08-26  read rawData and STATUS_NO_COMMUNICATION recognition (thanks to FabioBrondo)
  //  0.2.0  2020-06-20  #pragma once; major refactor; removed pre 1.0 support; fix offset
  //  0.1.10 2019-07-31  add 3 inline functions to test errors + demo sketch
  //  0.1.9  2017-07-27  reverted double -> float (issue33)
  //  0.1.08 2015-12-06  replaced all temperature calls with one TCfactor + update demos.
  //  0.1.07 2015-12-06  updated TC factors from the MAX31855 datasheet
  //  0.1.06 2015-12-05  added support for other types of TC's (experimental)
  //  0.1.05 2015-07-12  refactor robust constructor
  //  0.1.04 2015-03-09  replaced float -> double (ARM support)
  //  0.1.03 2014-01-24  fixed negative temperature
  //  0.1.02 2014-01-03  added offset
  //  0.1.01 2014-01-02  refactored speed/performance
  //  0.1.00 2014-01-02  initial version.
  //
  
  
  #include "MAX31855.h"
  
  
  MAX31855::MAX31855(const uint8_t cs)
  {
    _cs          = cs;
    _hwSPI       = true;
  
    _offset      = 0;
    _SC          = K_TC;
    _status      = STATUS_NOREAD;
    _temperature = MAX31855_NO_TEMPERATURE;
    _internal    = MAX31855_NO_TEMPERATURE;
    _rawData     = 0;
  }
  
  MAX31855::MAX31855(const uint8_t sclk, const uint8_t cs, const uint8_t miso)
  {
    _sclk        = sclk;
    _cs          = cs;
    _miso        = miso;
    _hwSPI       = false;
  
    _offset      = 0;
    _SC          = K_TC;
    _status      = STATUS_NOREAD;
    _temperature = MAX31855_NO_TEMPERATURE;
    _internal    = MAX31855_NO_TEMPERATURE;
    _rawData     = 0;
  }
  
  void MAX31855::begin()
  {
    pinMode(_cs, OUTPUT);
    digitalWrite(_cs, HIGH);
    if (_hwSPI)
    {
      SPI.begin();
      delay(1);
    }
    else
    {
      pinMode(_sclk, OUTPUT);
      pinMode(_miso, INPUT);
    }
  }
  
  
  uint8_t MAX31855::read()
  {
    // return value of _read()
    // BITS     DESCRIPTION
    // ----------------------
    // 00 - 02  STATUS
    //      03  RESERVED
    // 04 - 15  INTERNAL
    //      16  FAULT-BIT
    //      17  RESERVED
    // 18 - 30  TEMPERATURE (RAW)
    //      31  SIGN
    uint32_t value = _read();
  
    if (value == 0xFFFFFFFF)  // needs a pull up on miso pin to work properly!
    {
      // bit 3 and bit 17 should always be 0 - P10 datasheet
      _status = STATUS_NO_COMMUNICATION;
      return _status;
    }
  
    _lastRead = millis();
  
    // process status bit 0-2
    _status = value & 0x0007;
    if (_status != STATUS_OK)
    {
      return _status;
    }
  
    value >>= 3;
  
    // reserved bit 3, always 0
    value >>= 1;
  
    // process internal bit 4-15
    _internal = (value & 0x07FF) * 0.0625;
    // negative flag set ?
    if (value & 0x0800) 
    {
      _internal = -128 + _internal;
    }
    value >>= 12;
  
    // Fault bit ignored as we have the 3 status bits
    // _fault = value & 0x01;
    value >>= 1;
  
    // reserved bit 17, always 0
    value >>= 1;
  
    // process temperature bit 18-30 + sign bit = 31
    _temperature = (value & 0x1FFF) * 0.25;
    // negative flag set ?
    if (value & 0x2000)
    {
      _temperature = -2048 + _temperature;
    }
    return _status;
  }
  
  
  uint32_t MAX31855::_read(void)
  {
    _rawData = 0;
    digitalWrite(_cs, LOW);
    if (_hwSPI)
    {
      SPI.beginTransaction(SPISettings(16000000, MSBFIRST, SPI_MODE0));
      for (uint8_t i = 0; i < 4; i++)
      {
        _rawData <<= 8;
        _rawData += SPI.transfer(0);
      }
      SPI.endTransaction();
    }
    else
    {
      for (int8_t i = 31; i >= 0; i--)
      {
        _rawData <<= 1;
        digitalWrite(_sclk, LOW);
        // delayMicroseconds(1);  // DUE
        if ( digitalRead(_miso) ) _rawData++;
        digitalWrite(_sclk, HIGH);
        // delayMicroseconds(1);  // DUE
      }
    }
    digitalWrite(_cs, HIGH);
    return _rawData;
  }
  
  float MAX31855::getTemperature()
  {
    // offset needs to be added after multiplication TCfactor
    // not before otherwise offset will be larger / smaller
    // default behavior
    if (_SC == K_TC) return _temperature + _offset;
  
    // EXPERIMENTAL OTHER THERMOCOUPLES
    // in practice this works also for K_TC but is way slower..
    // 1: reverse calculate the Voltage measured
    float Vout = K_TC * (_temperature - _internal);  // PAGE 8 datasheet
  
    // 2: from Voltage to corrected temperature using the Seebeck Coefficient
    float _temp = Vout / _SC + _internal;
    return _temp;
  }
  
  // -- END OF FILE --
  