char val; // variable to receive data from the serial port
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);       // start serial communication at 9600bps
}

void loop() {
  // put your main code here, to run repeatedly:

 if( Serial.available() )       // if data is available to read
  {
    val = Serial.read();
   Serial.print(val);
  }
  if( val == 'H' )               // if 'H' was received
  {
    Serial.print(val);
  } else {
    Serial.print(val);
  }
  delay(100);                    // wait 100ms for next reading
}