/*
  This file is part of the MachineControl library.
  Copyright (c) 2020 Arduino SA.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library 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
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "MAX31855.h"

MAX31855Class::MAX31855Class(int cs, SPIClass& spi) :
  _cs(cs),
  _spi(&spi),
  _spiSettings(4000000, MSBFIRST, SPI_MODE0)
{
}

int MAX31855Class::begin()
{
  uint32_t rawword;

  pinMode(_cs, OUTPUT);
  digitalWrite(_cs, HIGH);
  _spi->begin();

  rawword = readSensor();
  if (rawword == 0xFFFFFF) {
    end();

    return 0;
  }

  return 1;
}

void MAX31855Class::end()
{
  pinMode(_cs, INPUT);
  digitalWrite(_cs, LOW);
  _spi->end();
}

uint32_t MAX31855Class::readSensor()
{
  uint32_t read = 0x00;

  digitalWrite(_cs, LOW);
  delayMicroseconds(1);

  _spi->beginTransaction(_spiSettings);


  for (int i = 0; i < 4; i++) {
    read <<= 8;
    read |= _spi->transfer(0);
  }

  _spi->endTransaction();

  digitalWrite(_cs, HIGH);
  return read;
}

float MAX31855Class::readTemperature(int type)
{
  uint32_t rawword;
  float celsius;

  rawword = readSensor();

  // Check for reading error
  if (rawword & 0x7) {
    return NAN; 
  }
  // The temperature is stored in the last 14 word's bits 
  // sent by the Thermocouple-to-Digital Converter
  if (rawword & 0x80000000) {
    // Negative value, drop the lower 18 bits and explicitly extend sign bits.
    rawword = 0xFFFFC000 | ((rawword >> 18) & 0x00003FFFF);
  } else {
    // Positive value, just drop the lower 18 bits.
    rawword >>= 18;
  }

  // multiply for the LSB value
  celsius = rawword * 0.25f;
  if (type == PROBE_J) {
    // conversion factor from K type to J type
    celsius = celsius * 4/5; 
  }
  return celsius;
}

float MAX31855Class::readReferenceTemperature(int type)
{
  uint32_t rawword;
  float ref;

  rawword = readSensor();

  // ignore first 4 FAULT bits
  rawword >>= 4;

  // The cold junction reference temperature is stored in the first 11 word's bits
  // sent by the Thermocouple-to-Digital Converter
  rawword = rawword & 0x7FF;
  // check sign bit  and convert to negative value.
  if (rawword & 0x800) {
    ref = (0xF800 | (rawword & 0x7FF))*0.0625;
  } else {
      // multiply for the LSB value
      ref = rawword * 0.0625f;
  }
  Serial.println(ref);
  return ref;
}

MAX31855Class THERM;