#include <SPI.h>

int CS = 10; // Chip Select pin

void setup() {
  Serial.begin(9600);
  pinMode(CS, OUTPUT);
  digitalWrite(CS, HIGH);
  SPI.begin();
}

double readThermocouple() {
  uint16_t v;

  digitalWrite(CS, LOW);           // Select MAX6675
  delay(1);                         // Let MAX6675 stabilize
  
  v = SPI.transfer16(0x00) << 3;    // Read 16-bit data and shift for bits
  v |= SPI.transfer(0x00) >> 5;     // Finish shifting and get temperature

  digitalWrite(CS, HIGH);           // Deselect MAX6675
  
  if (v & 0x4) return NAN;          // Check for thermocouple open
  
  return (v >> 3) * 0.25;           // Convert to Celsius
}

void loop() {
  double temperature = readThermocouple();
  
  if (isnan(temperature)) {
    Serial.println("Thermocouple not connected");
  } else {
    Serial.print("Temperature: ");
    Serial.print(temperature);
    Serial.println(" °C");
  }

  delay(1000); // Wait for next reading
}