#define IR1 10
#define IR2 9
#define IR3 11

int count=0;

int val = 0x00; //Valor entrada serie

void setup()                    
{
  Serial.begin(19200); 
  
  analogWrite(IR1, 0);
  analogWrite(IR2, 0);
  analogWrite(IR3, 0);
}

void loop()                      //run over and over again
{
  
  if (Serial.available()) {
    val = Serial.read();
    
    if (count==0) 
    {
        analogWrite(IR1, val);
        count=1;
    }
    else if (count==1) 
    {
      analogWrite(IR2, val);
      count=2;
    }
    else if (count==2) 
    {
      analogWrite(IR3, val);
      count=0;
    }
  }
}