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tree: db807c562f
James Sanford
68 lines (51 sloc) 1.073 kb
// this library is public domain. enjoy!
// www.ladyada.net/learn/sensors/thermocouple
#include <avr/pgmspace.h>
#include <util/delay.h>
#include <stdlib.h>
#include "max6675.h"
MAX6675::MAX6675(int8_t SCLK, int8_t CS, int8_t MISO) {
sclk = SCLK;
cs = CS;
miso = MISO;
//define pin modes
pinMode(cs, OUTPUT);
pinMode(sclk, OUTPUT);
pinMode(miso, INPUT);
digitalWrite(cs, HIGH);
}
double MAX6675::readCelsius(void) {
uint16_t v;
digitalWrite(cs, LOW);
_delay_ms(1);
v = spiread();
v <<= 8;
v |= spiread();
digitalWrite(cs, HIGH);
if (v & 0x4) {
// uh oh, no thermocouple attached!
return NAN;
//return -100;
}
v >>= 3;
return v*0.25;
}
double MAX6675::readFahrenheit(void) {
return readCelsius() * 9.0/5.0 + 32;
}
byte MAX6675::spiread(void) {
int i;
byte d = 0;
for (i=7; i>=0; i--)
{
digitalWrite(sclk, LOW);
_delay_ms(1);
if (digitalRead(miso)) {
//set the bit to 0 no matter what
d |= (1 << i);
}
digitalWrite(sclk, HIGH);
_delay_ms(1);
}
return d;
}
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