unsigned int ADCValue;
double temp_pv, temp_sv;
double timer1_counter; //for timer
boolean stringComplete = false;  // whether the string is complete
boolean start = false;  //start controling temperature
String mySt = "";
int delay_output;
boolean relay_on, relay_on_off;

const byte relay = 2; //relay output on Pin 2

void setup() {
  pinMode(relay,OUTPUT);
  analogReference(EXTERNAL);
  Serial.begin(9600);
  //--------------------------timer setup
  noInterrupts();           // disable all interrupts
  TCCR1A = 0;
  TCCR1B = 0;
  timer1_counter = 59286;   // preload timer 65536-16MHz/256/2Hz (34286 for 0.5sec) (59286 for 0.1sec)

  TCNT1 = timer1_counter;   // preload timer
  TCCR1B |= (1 << CS12);    // 256 prescaler 
  TIMSK1 |= (1 << TOIE1);   // enable timer overflow interrupt
  interrupts();             // enable all interrupts
  //--------------------------timer setup

}

void loop() {
  if (stringComplete) {
    // clear the string when COM receiving is completed
    mySt = "";  //mySt is blank until '\n' is received
    stringComplete = false;
  }

  //receive command from Visual Studio
  if (mySt.substring(0,10) == "temp_start"){
    start = true;
  }
  if (mySt.substring(0,9) == "temp_stop"){
    start = false;
  }
  if (mySt.substring(0,8) == "temp_set"){
    temp_sv = mySt.substring(8,mySt.length()).toFloat();  //get string after temp_set
  }

  if(start) //start controlling temperature - "start" command from Visual Studio
  {
    if (temp_pv < temp_sv - 2.0)  //on heating
    {
      relay_on = true;
    }
    if (temp_pv > temp_sv + 2.0) //off heating
    {
      digitalWrite(relay,0);
      relay_on = false;
    }
    if (relay_on) relay_on_sequence();  //on heating by sequence on_off
  }
  else  //stop controlling temperature - "stop" command from Visual Studio
  {
    digitalWrite(relay,0);
  }
}

ISR(TIMER1_OVF_vect)        // interrupt service routine - tick every 0.1sec
{
  TCNT1 = timer1_counter;   // set timer
  ADCValue = analogRead(0);
  temp_pv = 0.00007*ADCValue*ADCValue-0.1849*ADCValue+103.02+2.3;
  
  //Serial.print(ADCValue); //un-comment for calibration
  //Serial.print("---");    //un-comment for calibration
  Serial.println(temp_pv);
}

void serialEvent() {
  while (Serial.available()) {
    // get the new byte:
    char inChar = (char)Serial.read();
    // add it to the inputString:
    if (inChar != '\n') {
      mySt += inChar;
    }
    // if the incoming character is a newline, set a flag
    // so the main loop can do something about it:
    if (inChar == '\n') {
      stringComplete = true;
    }
  }
}

void relay_on_sequence()
{
  if (relay_on_off)
  {
    digitalWrite(relay,1);
    delay_output++;
    if (delay_output >= 30000) relay_on_off = false;
  }
  else
  {
    digitalWrite(relay,0);
    delay_output++;
    if (delay_output >= 30000) relay_on_off = true;
  }
  if (delay_output >= 30000) delay_output = 0;
}

private: System::Void Form1_Load(System::Object^  sender, System::EventArgs^  e) {
     serialPort1->Open();
     timer1->Start();
     mStr = "0";
     i=3000;
    }
 private: System::Void serialPort1_DataReceived(System::Object^  sender, System::IO::Ports::SerialDataReceivedEventArgs^  e) {
     mStr = serialPort1->ReadLine();
    }
 private: System::Void timer1_Tick(System::Object^  sender, System::EventArgs^  e) {
     label1->Text=mStr;

     this->chart1->Series["Series1"]->Points->AddXY(i,System::Convert::ToDouble(mStr));
     i++;
     this->chart1->ChartAreas["ChartArea1"]->AxisX->Minimum=i-3000; //shift x-axis
    }
 private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
     serialPort1->WriteLine("temp_set"+textBox1->Text);
    }
 private: System::Void button2_Click(System::Object^  sender, System::EventArgs^  e) {
    serialPort1->WriteLine("temp_start");
   }
 private: System::Void button3_Click(System::Object^  sender, System::EventArgs^  e) {
    serialPort1->WriteLine("temp_stop");
   }