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107 lines
2.4 KiB
C++
107 lines
2.4 KiB
C++
//
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// FILE: MAX31855.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.9
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// PURPOSE: MAX31855 - Thermocouple
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// DATE: 2014-01-01
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// URL: http://forum.arduino.cc/index.php?topic=208061
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//
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// HISTORY:
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// 0.1.9 2017-07-27 reverted double -> float (issue33)
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// 0.1.08 2015-12-06 replaced all temperature calls with one TCfactor + update demos.
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// 0.1.07 2015-12-06 updated TC factors from the MAX31855 datasheet
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// 0.1.06 2015-12-05 added support for other types of TC's (experimental)
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// 0.1.05 2015-07-12 refactor robust constructor
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// 0.1.04 2015-03-09 replaced float -> double (ARM support)
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// 0.1.03 fixed negative temperature
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// 0.1.02 added offset
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// 0.1.01 refactored speed/performance
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// 0.1.00 initial version.
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//
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// Released to the public domain
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//
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#include "MAX31855.h"
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MAX31855::MAX31855(const uint8_t sclk, const uint8_t cs, const uint8_t miso)
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{
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_sclk = sclk;
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_cs = cs;
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_miso = miso;
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_offset = 0;
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_TCfactor = K_TC;
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_status = STATUS_NOREAD;
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_temperature = -999;
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_internal = -999;
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}
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void MAX31855::begin()
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{
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pinMode(_cs, OUTPUT);
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digitalWrite(_cs, HIGH);
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pinMode(_sclk, OUTPUT);
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pinMode(_miso, INPUT);
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}
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uint8_t MAX31855::read()
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{
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uint32_t value = _read();
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// process status bit 0-2
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_status = value & 0x0007;
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value >>= 3;
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// reserved bit 3
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value >>= 1;
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// process internal bit 4-15
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_internal = (value & 0x07FF) * 0.0625;
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if (value & 0x0800)
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{
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_internal = -128 + _internal; // fix neg temp
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}
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value >>= 12;
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// Fault bit ignored as we have the 3 status bits
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// _fault = value & 0x01;
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value >>= 1;
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// reserved bit 17
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value >>= 1;
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// process temperature bit 18-30 + sign bit = 31
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_temperature = (value & 0x1FFF) * 0.25;
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if (value & 0x2000) // negative flag
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{
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_temperature = -2048 + _temperature; // fix neg temp
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}
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if (_offset != 0) _temperature += _offset;
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return _status;
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}
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// TODO: optimize performance by direct port manipulation?
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uint32_t MAX31855::_read(void)
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{
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uint32_t value = 0;
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digitalWrite(_cs, LOW);
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for (int8_t i = 31; i >= 0; i--)
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{
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value <<= 1;
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digitalWrite(_sclk, LOW);
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// delayMicroseconds(1); // DUE
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if ( digitalRead(_miso) ) value += 1;
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digitalWrite(_sclk, HIGH);
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// delayMicroseconds(1); // DUE
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}
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digitalWrite(_cs, HIGH);
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return value;
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}
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// END OF FILE
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