74 lines
1.1 KiB
C++
74 lines
1.1 KiB
C++
// this library is public domain. enjoy!
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// www.ladyada.net/learn/sensors/thermocouple
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#include <avr/pgmspace.h>
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#include <util/delay.h>
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#include <stdlib.h>
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#include "max6675_local.h"
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MAX6675::MAX6675(int8_t SCLK, int8_t CS, int8_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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//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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double MAX6675::readCelsius(void)
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{
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uint16_t v;
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digitalWrite(cs, LOW);
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_delay_ms(1);
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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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{
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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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double MAX6675::readFarenheit(void)
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{
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return readCelsius() * 9.0 / 5.0 + 32;
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}
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byte MAX6675::spiread(void)
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{
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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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{
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digitalWrite(sclk, LOW);
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_delay_ms(1);
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if (digitalRead(miso))
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{
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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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_delay_ms(1);
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}
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return d;
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}
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