MAX6675 thermocouple converter Arduino code sample

max6675_test.ino

//
// MAX6675 thermocouple converter Arduino code sample
//
// 2016.05.12 darell tan
//

#include <SPI.h>

static const int CS_PIN = 13;

void setup() {
  Serial.begin(115200);
  SPI.begin();

  pinMode(CS_PIN, OUTPUT);
  digitalWrite(CS_PIN, HIGH);
}

void loop() {
  SPI.beginTransaction(SPISettings(14000000, MSBFIRST, SPI_MODE0));
  digitalWrite(CS_PIN, LOW);

  // read 16 bits, MSB first
  uint16_t data = 0;
  data |= SPI.transfer(0) << 8;
  data |= SPI.transfer(0) << 0;

  SPI.endTransaction();
  digitalWrite(CS_PIN, HIGH);

  // interpret value
  if (data & 0x8000) {
    Serial.println("sign not zero!");
  } else if (data & 0b100) {
    Serial.println("not conn");
  } else {
    uint16_t temp = (data & 0x7FF8) >> 3;

#if DEBUG
    Serial.print("0x");
    Serial.print(data >> 8, HEX);
    Serial.print(data & 0xFF, HEX);
    Serial.print(" -- ");
#endif

    // ADC is 12 bits (0-4095)
    // temp is 0deg to 1023.75deg
    // therefore each increment is 0.25 deg, or 1/4 deg
    Serial.print(temp / 4);
    Serial.print('.');
    Serial.print(25 * (temp % 4));
    Serial.println();
  }

  delay(1000);
}