• Source 
    1. // this library is public domain. enjoy!
    2. // www.ladyada.net/learn/sensors/thermocouple
    3.  
    4. #ifdef __AVR
    5.   #include <avr/pgmspace.h>
    6. #elif defined(ESP8266)
    7.   #include <pgmspace.h>
    8. #endif
    9. #include <util/delay.h>
    10. #include <stdlib.h>
    11. #include "max6675.h"
    12.  
    13. MAX6675::MAX6675(int8_t SCLK, int8_t CS, int8_t MISO) {
    14.   sclk = SCLK;
    15.   cs = CS;
    16.   miso = MISO;
    17.  
    18.   //define pin modes
    19.   pinMode(cs, OUTPUT);
    20.   pinMode(sclk, OUTPUT); 
    21.   pinMode(miso, INPUT);
    22.  
    23.   digitalWrite(cs, HIGH);
    24. }
    25. double MAX6675::readCelsius(void) {
    26.  
    27.   uint16_t v;
    28.  
    29.   digitalWrite(cs, LOW);
    30.   _delay_ms(1);
    31.  
    32.   v = spiread();
    33.   v <<= 8;
    34.   v |= spiread();
    35.  
    36.   digitalWrite(cs, HIGH);
    37.  
    38.   if (v & 0x4) {
    39.     // uh oh, no thermocouple attached!
    40.     return NAN; 
    41.     //return -100;
    42.   }
    43.  
    44.   v >>= 3;
    45.  
    46.   return v*0.25;
    47. }
    48.  
    49. double MAX6675::readFahrenheit(void) {
    50.   return readCelsius() * 9.0/5.0 + 32;
    51. }
    52.  
    53. byte MAX6675::spiread(void) { 
    54.   int i;
    55.   byte d = 0;
    56.  
    57.   for (i=7; i>=0; i--)
    58.   {
    59.     digitalWrite(sclk, LOW);
    60.     _delay_ms(1);
    61.     if (digitalRead(miso)) {
    62.       //set the bit to 0 no matter what
    63.       d |= (1 << i);
    64.     }
    65.  
    66.     digitalWrite(sclk, HIGH);
    67.     _delay_ms(1);
    68.   }
    69.  
    70.   return d;
    71. }
    72.