mirror of
https://github.com/RobTillaart/Arduino.git
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148 lines
2.9 KiB
C++
148 lines
2.9 KiB
C++
//
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// FILE: MAX6675.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.3.2
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// PURPOSE: Arduino library for MAX6675 chip for K type thermocouple
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// DATE: 2022-01-11
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// URL: https://github.com/RobTillaart/MAX6675
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#include "MAX6675.h"
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// HW SPI
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MAX6675::MAX6675(uint8_t select, __SPI_CLASS__ * mySPI)
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{
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_select = select;
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_miso = 255;
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_clock = 255;
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_mySPI = mySPI;
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_hwSPI = true;
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}
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// SW SPI
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MAX6675::MAX6675(uint8_t select, uint8_t miso, uint8_t clock)
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{
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_select = select;
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_miso = miso;
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_clock = clock;
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_mySPI = NULL;
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_hwSPI = false;
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}
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void MAX6675::begin()
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{
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_lastTimeRead = 0;
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_offset = 0;
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_status = STATUS_NOREAD;
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_temperature = MAX6675_NO_TEMPERATURE;
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_rawData = 0;
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setSPIspeed(1000000);
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pinMode(_select, OUTPUT);
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digitalWrite(_select, HIGH);
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if (_hwSPI)
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{
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// _mySPI->end();
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// _mySPI->begin();
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// delay(1);
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}
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else
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{
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pinMode(_clock, OUTPUT);
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digitalWrite(_clock, LOW);
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pinMode(_miso, INPUT);
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}
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}
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void MAX6675::setSPIspeed(uint32_t speed)
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{
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_SPIspeed = speed;
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_spi_settings = SPISettings(_SPIspeed, MSBFIRST, SPI_MODE0);
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};
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uint8_t MAX6675::read()
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{
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// return value of _read() page 5 datasheet
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// BITS DESCRIPTION
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// ------------------------------
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// 00 three state ?
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// 01 device ID ?
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// 02 INPUT OPEN
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// 03 - 14 TEMPERATURE (RAW)
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// 15 SIGN
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uint16_t value = _read();
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// needs a pull up on MISO pin to work properly!
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if (value == 0xFFFF)
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{
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_status = STATUS_NO_COMMUNICATION;
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return _status;
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}
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_lastTimeRead = millis();
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// process status bit 2
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_status = value & 0x04;
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value >>= 3;
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// process temperature bits
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_temperature = (value & 0x1FFF) * 0.25;
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// dummy negative flag set ?
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// if (value & 0x2000)
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return _status;
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}
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///////////////////////////////////////////////////
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//
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// PRIVATE
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//
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uint32_t MAX6675::_read(void)
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{
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_rawData = 0;
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// DATA TRANSFER
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if (_hwSPI)
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{
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_mySPI->beginTransaction(_spi_settings);
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// must be after mySPI->beginTransaction() - STM32 (#14 MAX31855_RT)
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digitalWrite(_select, LOW);
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_rawData = _mySPI->transfer(0);
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_rawData <<= 8;
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_rawData += _mySPI->transfer(0);
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digitalWrite(_select, HIGH);
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_mySPI->endTransaction();
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}
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else // Software SPI
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{
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// split _swSPIdelay in equal dLow and dHigh
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// dLow should be longer one when _swSPIdelay = odd.
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uint16_t dHigh = _swSPIdelay / 2;
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uint16_t dLow = _swSPIdelay - dHigh;
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digitalWrite(_select, LOW);
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for (int8_t i = 15; i >= 0; i--)
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{
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_rawData <<= 1;
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digitalWrite(_clock, LOW);
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if (dLow > 0) delayMicroseconds(dLow); // DUE might need 1 us
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if ( digitalRead(_miso) ) _rawData++;
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digitalWrite(_clock, HIGH);
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if (dHigh > 0) delayMicroseconds(dHigh); // DUE
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}
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digitalWrite(_select, HIGH);
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}
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return _rawData;
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}
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// -- END OF FILE --
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