Arduino colaborativo/Tutorial Arduino - Lição 7/Software/Fluxograma

String c, string;
int variavel = 0;

void setup()
{
  Serial.begin(9600);
  pinMode(13, OUTPUT); //LED
  pinMode(4, INPUT); //botao
  pinMode(2, INPUT);
  attachInterrupt(0, interrupt , RISING);
}

void loop()
{
  
  if(Serial.available() > 0) string = "";
  
  
  while(Serial.available() > 0)
  {
    c = (byte)Serial.read();
    if(c == ":")
    {
      break;
    }else
    {
      string += c; // string = string + c;
    }
    delay(1);
  }
  
  if(string == "L")
  {
    analogWrite(A4, 255);
    analogWrite(A5, 255);
  }
  if(string =="O")
  {
    analogWrite(A4, 0);
    analogWrite(A5, 0);
  }
  if(string =="X")
  {
    analogWrite(A4, 0);
    analogWrite(A5, 0);
  }
  
  if(string == "A")
  {
    analogWrite(A5, 255);
  }
  if(string == "B")
  {
    analogWrite(A5, 0);
  }
  
  if(string == "C")
  {
    analogWrite(A4, 255);
  }
  if(string =="D")
  {
    analogWrite(A4, 0);
  }

    Serial.println(variavel);
    delay(1500);
}

void interrupt (){
  Serial.print("B1");
  variavel++;
}