mirror of
https://github.com/RobTillaart/Arduino.git
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148 lines
4.0 KiB
C++
148 lines
4.0 KiB
C++
#pragma once
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//
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// FILE: MAX31855.h
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// AUTHOR: Rob Tillaart
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// VERSION: 0.4.3
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// PURPOSE: Arduino library for MAX31855 chip for K type thermocouple
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// DATE: 2014-01-01
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// URL: https://github.com/RobTillaart/MAX31855_RT
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// http://forum.arduino.cc/index.php?topic=208061
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// Breakout board
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//
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// +---------+
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// Vin | o |
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// 3V3 | o |
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// GND | o O | Thermocouple
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// D0 | o O | Thermocouple
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// CS | o |
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// CLK | o |
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// +---------+
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#include "Arduino.h"
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#include "SPI.h"
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#define MAX31855_VERSION (F("0.4.3"))
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#define MAX31855_NO_TEMPERATURE -999
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// STATE constants returned by read()
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#define STATUS_OK 0x00
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#define STATUS_OPEN_CIRCUIT 0x01
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#define STATUS_SHORT_TO_GND 0x02
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#define STATUS_SHORT_TO_VCC 0x04
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#define STATUS_ERROR 0x07
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#define STATUS_NOREAD 0x80
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#define STATUS_NO_COMMUNICATION 0x81
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// Thermocouples working is based upon Seebeck effect.
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// Different TC have a different Seebeck Coefficient (µV/°C)
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// See http://www.analog.com/library/analogDialogue/archives/44-10/thermocouple.html
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//
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// As the MAX31855 is designed for K type sensors, one can calculate
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// the factor needed to convert other sensors measurements.
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// NOTE: this is only a linear approximation.
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//
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// Seebeck Coefficients (sensitivity) from the MAX31855 datasheet page 8
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// to be used in setSeebeckCoefficient()
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//
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// TYPE COEFFICIENT
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#define E_TC 76.373
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#define J_TC 57.953
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#define K_TC 41.276
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#define N_TC 36.256
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#define R_TC 10.506
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#define S_TC 9.587
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#define T_TC 52.18
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class MAX31855
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{
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public:
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MAX31855();
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// HW SPI
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void begin(uint8_t select);
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// SW SPI
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void begin(uint8_t clock, uint8_t select, uint8_t miso);
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// returns state - bit field: 0 = STATUS_OK
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uint8_t read();
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float getInternal(void) const { return _internal; }
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float getTemperature(void);
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uint8_t getStatus(void) const { return _status; };
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inline bool openCircuit() { return _status == STATUS_OPEN_CIRCUIT; };
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inline bool shortToGND() { return _status == STATUS_SHORT_TO_GND; };
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inline bool shortToVCC() { return _status == STATUS_SHORT_TO_VCC; };
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inline bool genericError() { return _status == STATUS_ERROR; };
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inline bool noRead() { return _status == STATUS_NOREAD; };
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inline bool noCommunication() { return _status == STATUS_NO_COMMUNICATION; };
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// use offset to calibrate the TC.
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void setOffset(const float t) { _offset = t; };
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float getOffset() const { return _offset; };
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// set the above E_TC or other Seebeck Coefficients
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// one can also set your own optimized values.
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void setSeebeckCoefficient(const float SC) { _SeebeckC = SC; };
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float getSeebeckCoefficient() const { return _SeebeckC; };
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uint32_t lastRead() { return _lastTimeRead; };
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uint32_t getRawData() { return _rawData;};
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// speed in Hz
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void setSPIspeed(uint32_t speed);
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uint32_t getSPIspeed() { return _SPIspeed; };
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void setSWSPIdelay(uint16_t del = 0) { _swSPIdelay = del; };
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uint16_t getSWSPIdelay() { return _swSPIdelay; };
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// ESP32 specific
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#if defined(ESP32)
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void selectHSPI() { _useHSPI = true; };
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void selectVSPI() { _useHSPI = false; };
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bool usesHSPI() { return _useHSPI; };
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bool usesVSPI() { return !_useHSPI; };
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// to overrule ESP32 default hardware pins
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void setGPIOpins(uint8_t clock, uint8_t miso, uint8_t mosi, uint8_t select);
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#endif
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private:
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uint32_t _read();
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uint8_t _status;
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float _internal;
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float _temperature;
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float _offset;
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float _SeebeckC;
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uint32_t _lastTimeRead;
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uint32_t _rawData;
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bool _hwSPI;
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uint8_t _clock;
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uint8_t _miso;
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uint8_t _select;
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uint16_t _swSPIdelay = 0;
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uint32_t _SPIspeed;
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SPIClass * mySPI;
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SPISettings _spi_settings;
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#if defined(ESP32)
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bool _useHSPI = true;
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#endif
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};
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// -- END OF FILE --
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