Permalink
Find file
179 lines (140 sloc) 3.58 KB
/***************************************************
This is a library for the Adafruit Thermocouple Sensor w/MAX31855K
Designed specifically to work with the Adafruit Thermocouple Sensor
----> https://www.adafruit.com/products/269
These displays use SPI to communicate, 3 pins are required to
interface
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing
products from Adafruit!
Written by Limor Fried/Ladyada for Adafruit Industries.
BSD license, all text above must be included in any redistribution
****************************************************/
#include "Adafruit_MAX31855.h"
#ifdef __AVR
#include <avr/pgmspace.h>
#elif defined(ESP8266)
#include <pgmspace.h>
#endif
#include <stdlib.h>
#include <SPI.h>
Adafruit_MAX31855::Adafruit_MAX31855(int8_t _sclk, int8_t _cs, int8_t _miso) {
sclk = _sclk;
cs = _cs;
miso = _miso;
initialized = false;
}
Adafruit_MAX31855::Adafruit_MAX31855(int8_t _cs) {
cs = _cs;
sclk = miso = -1;
initialized = false;
}
void Adafruit_MAX31855::begin(void) {
//define pin modes
pinMode(cs, OUTPUT);
digitalWrite(cs, HIGH);
if (sclk == -1) {
// hardware SPI
//start and configure hardware SPI
SPI.begin();
} else {
pinMode(sclk, OUTPUT);
pinMode(miso, INPUT);
}
initialized = true;
}
double Adafruit_MAX31855::readInternal(void) {
uint32_t v;
v = spiread32();
// ignore bottom 4 bits - they're just thermocouple data
v >>= 4;
// pull the bottom 11 bits off
float internal = v & 0x7FF;
// check sign bit!
if (v & 0x800) {
// Convert to negative value by extending sign and casting to signed type.
int16_t tmp = 0xF800 | (v & 0x7FF);
internal = tmp;
}
internal *= 0.0625; // LSB = 0.0625 degrees
//Serial.print("\tInternal Temp: "); Serial.println(internal);
return internal;
}
double Adafruit_MAX31855::readCelsius(void) {
int32_t v;
v = spiread32();
//Serial.print("0x"); Serial.println(v, HEX);
/*
float internal = (v >> 4) & 0x7FF;
internal *= 0.0625;
if ((v >> 4) & 0x800)
internal *= -1;
Serial.print("\tInternal Temp: "); Serial.println(internal);
*/
if (v & 0x7) {
// uh oh, a serious problem!
return NAN;
}
if (v & 0x80000000) {
// Negative value, drop the lower 18 bits and explicitly extend sign bits.
v = 0xFFFFC000 | ((v >> 18) & 0x00003FFFF);
}
else {
// Positive value, just drop the lower 18 bits.
v >>= 18;
}
//Serial.println(v, HEX);
double centigrade = v;
// LSB = 0.25 degrees C
centigrade *= 0.25;
return centigrade;
}
uint8_t Adafruit_MAX31855::readError() {
return spiread32() & 0x7;
}
double Adafruit_MAX31855::readFarenheit(void) {
float f = readCelsius();
f *= 9.0;
f /= 5.0;
f += 32;
return f;
}
uint32_t Adafruit_MAX31855::spiread32(void) {
int i;
uint32_t d = 0;
// backcompatibility!
if (! initialized) {
begin();
}
digitalWrite(cs, LOW);
delay(1);
if(sclk == -1) {
// hardware SPI
SPI.beginTransaction(SPISettings(4000000, MSBFIRST, SPI_MODE0));
d = SPI.transfer(0);
d <<= 8;
d |= SPI.transfer(0);
d <<= 8;
d |= SPI.transfer(0);
d <<= 8;
d |= SPI.transfer(0);
SPI.endTransaction();
} else {
// software SPI
digitalWrite(sclk, LOW);
delay(1);
for (i=31; i>=0; i--) {
digitalWrite(sclk, LOW);
delay(1);
d <<= 1;
if (digitalRead(miso)) {
d |= 1;
}
digitalWrite(sclk, HIGH);
delay(1);
}
}
digitalWrite(cs, HIGH);
//Serial.println(d, HEX);
return d;
}