Kiln and bath probes on an Arduino Uno

// Kiln and bath probes: a K-type thermocouple on a MAX31855 for the kiln,
// which runs to well over 1000 C, and a PT100 platinum probe on a MAX31865
// for the glaze bath beside it, where a tenth of a degree matters.
//
//   MAX31865  CLK -> 13   SDO -> 12   SDI -> 11   CS -> 10
//   MAX31855  CLK -> 7    CS -> 6     DO -> 5
//
// A thermocouple reaches far hotter than an RTD; an RTD is far more exact.
// The MAX31855 also reads its own board's temperature, the cold junction.
//
// Things to try. Drag the thermocouple slider past 1000 C and watch the
// sketch call the kiln ready. Drag the RTD slider.

#include <SPI.h>
#include "Adafruit_MAX31855.h"
#include <Adafruit_MAX31865.h>

Adafruit_MAX31855 kiln(7, 6, 5);  // CLK, CS, DO
Adafruit_MAX31865 bath(10);       // CS, on the SPI pins

void setup() {
  Serial.begin(9600);
  kiln.begin();
  bath.begin(MAX31865_2WIRE);
  Serial.println("Kiln and bath probes");
}

void loop() {
  double k = kiln.readCelsius();
  float b = bath.temperature(100.0, 430.0);
  Serial.print("kiln ");
  if (isnan(k)) {
    Serial.print("fault");
  } else {
    Serial.print(k, 0);
    Serial.print(" C");
  }
  Serial.print("  board ");
  Serial.print(kiln.readInternal(), 1);
  Serial.print(" C  bath ");
  Serial.print(b, 1);
  Serial.println(" C");
  if (!isnan(k) && k >= 1000) {
    Serial.println("Kiln at temperature");
  }
  delay(500);
}