83 lines
1.9 KiB
C++
83 lines
1.9 KiB
C++
// this library is public domain. enjoy!
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// https://learn.adafruit.com/thermocouple/
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#include "max6675.h"
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/**************************************************************************/
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/*!
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@brief Initialize a MAX6675 sensor
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@param SCLK The Arduino pin connected to Clock
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@param CS The Arduino pin connected to Chip Select
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@param MISO The Arduino pin connected to Data Out
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*/
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/**************************************************************************/
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MAX6675::MAX6675(int8_t SCLK, int8_t CS, int8_t MISO) {
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sclk = SCLK;
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cs = CS;
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miso = MISO;
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// define pin modes
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pinMode(cs, OUTPUT);
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pinMode(sclk, OUTPUT);
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pinMode(miso, INPUT);
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digitalWrite(cs, HIGH);
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}
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/**************************************************************************/
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/*!
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@brief Read the Celsius temperature
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@returns Temperature in C or NAN on failure!
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*/
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/**************************************************************************/
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float MAX6675::readCelsius(void) {
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uint16_t v;
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digitalWrite(cs, LOW);
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delayMicroseconds(10);
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v = spiread();
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v <<= 8;
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v |= spiread();
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digitalWrite(cs, HIGH);
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if (v & 0x4) {
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// uh oh, no thermocouple attached!
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return NAN;
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// return -100;
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}
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v >>= 3;
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return v * 0.25;
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}
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/**************************************************************************/
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/*!
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@brief Read the Fahenheit temperature
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@returns Temperature in F or NAN on failure!
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*/
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/**************************************************************************/
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float MAX6675::readFahrenheit(void) { return readCelsius() * 9.0 / 5.0 + 32; }
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byte MAX6675::spiread(void) {
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int i;
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byte d = 0;
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for (i = 7; i >= 0; i--) {
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digitalWrite(sclk, LOW);
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delayMicroseconds(10);
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if (digitalRead(miso)) {
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// set the bit to 0 no matter what
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d |= (1 << i);
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}
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digitalWrite(sclk, HIGH);
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delayMicroseconds(10);
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}
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return d;
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}
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