arduino sample for toaster control

toaster.ino

#include <SPI.h>

#define PROMINI

#ifdef PROMINI
  // pin number
  #define VCC  8
  #define GND  9
  #define SLAVE  10
  
  #define RELAY 9
#else
  // pin number
  #define VCC  8
  #define GND  9
  #define SLAVE  10
  
  #define RELAY 6
#endif

// command
#define PRE_HEAT 1
#define KEEP_60  2
#define PRE_HEAT_160  3
#define KEEP_160  4
#define FINAL_HEAT  5
#define FINISH   6

// temperature keep condition
// 60C : 1min
// 160C : 3.5min
// 220C : done
#define KEEP_60_TIME_SEC     (30)
#define KEEP_160_TIME_SEC    (60 * 1 + 30)
#define KEEP_60_TEMPERATURE_MAX (59.5)
#define KEEP_60_TEMPERATURE_MIN (60.0)
#define KEEP_160_TEMPERATURE_MAX (159.5)
#define KEEP_160_TEMPERATURE_MIN (160.0)
#define FINAL_TEMPERATURE_MIN (220.0)

#define INVALID -1

int state = PRE_HEAT;
unsigned long currentTime = 0;
unsigned long startTime = 0;

void setup() {
#ifdef GND
  pinMode(GND, OUTPUT);
  digitalWrite(GND, LOW);
#endif
#ifdef VCC
  pinMode(VCC, OUTPUT);
  digitalWrite(VCC, HIGH);
#endif
  pinMode(SLAVE, OUTPUT);
  digitalWrite(SLAVE, HIGH);

  pinMode(RELAY, OUTPUT);
  digitalWrite(RELAY, HIGH);

  Serial.begin(9600);
  SPI.begin();
  SPI.setBitOrder(MSBFIRST);
  SPI.setClockDivider(SPI_CLOCK_DIV4);
  SPI.setDataMode(SPI_MODE0);
}

void loop() {
  int value;
  float temp;

  delay(1000);
  digitalWrite(SLAVE, LOW);        //  Enable the chip
  value = SPI.transfer(0x00) << 8;  //  Read high byte
  value |= SPI.transfer(0x00);      //  Read low byte
  digitalWrite(SLAVE, HIGH);         //  Disable the chip

  if ((value & 0x0004) != 0){
    Serial.println("Error");
    temp = 1000; // fail safe
  } else {
    temp = ((value >> 3) * 0.25);
    Serial.print(",");
    Serial.println(temp);
  }

  // state machine
  switch (state) {
  case PRE_HEAT:
    Serial.print("pre 1: ");
    digitalWrite(RELAY, HIGH);
    if (temp < KEEP_60_TEMPERATURE_MIN) {
      /* do nothing; */
    } else {
      // move to next state
      state = KEEP_60;
      currentTime = INVALID;
    }
    break;

  case KEEP_60:
    {
    Serial.print("keep 1: ");
    if (temp < KEEP_60_TEMPERATURE_MIN) {
      digitalWrite(RELAY, HIGH);
      Serial.print(" (ON)");
    } else if (temp > KEEP_60_TEMPERATURE_MAX) {
      digitalWrite(RELAY, LOW);
      Serial.print(" (OFF)");
    }

    if (currentTime == INVALID) {
      startTime = millis();
      currentTime = millis();
    }

    unsigned long diff = (currentTime-startTime) * 0.001;
    if (diff < KEEP_60_TIME_SEC ) {
      currentTime = millis();
      Serial.print(" time(" );
      Serial.print((currentTime-startTime) * 0.001);
      Serial.print(")  " );
    } else {
      // move to next state
      currentTime = INVALID;
      state = PRE_HEAT_160;
    }
    }
    break;

  case PRE_HEAT_160:
    Serial.print("pre heat: ");
    digitalWrite(RELAY, HIGH);
    if (temp < KEEP_160_TEMPERATURE_MIN) {
      /* do nothing; */
    } else {
      // move to next state
      state = KEEP_160;
      currentTime = INVALID;
    }
    break;

  case KEEP_160:
    {
    Serial.print("keep: ");
    if (temp < KEEP_160_TEMPERATURE_MIN) {
      digitalWrite(RELAY, HIGH);
      Serial.print(" (ON)");
    } else if (temp > KEEP_160_TEMPERATURE_MAX) {
      digitalWrite(RELAY, LOW);
      Serial.print(" (OFF)");
    }

    if (currentTime == INVALID) {
      startTime = millis();
      currentTime = millis();
    }

    unsigned long diff = (currentTime-startTime) * 0.001;
    if (diff < KEEP_160_TIME_SEC ) {
      currentTime = millis();
      Serial.print(" time(" );
      Serial.print((currentTime-startTime) * 0.001);
      Serial.print(")  " );
    } else {
      // move to next state
      currentTime = INVALID;
      state = FINAL_HEAT;
    }
    }
    break;

  case FINAL_HEAT:
    Serial.print("final heat: ");
    digitalWrite(RELAY, HIGH);
    if (temp < FINAL_TEMPERATURE_MIN) {
      /* do nothing; */
    } else {
      // move to next state
      state = FINISH;
      currentTime = INVALID;
    }
    break;


  case FINISH:
    Serial.print("finish: ");
    digitalWrite(RELAY, LOW);
    Serial.println(" **** OPEN THE DOOR ****");
    break;
  }
}