// Read data from the serial and turn ON or OFF a light depending on the value
#include <SoftwareSerial.h>

#define RX    A0  // *** D3, Pin 2
#define TX    A1   // *** D4, Pin 3

SoftwareSerial Serial(RX, TX);

char val;                          // Data received from the serial port 
int ledPin = 8;                    // Set the pin to digital I/O 13

void setup() { 
  pinMode(ledPin, OUTPUT);         // Set pin as OUTPUT 
  Serial.begin(9600);              // Start serial communication at 9600 bps 
} 
 
void loop() { 
  if (Serial.available()) {        // If data is available to read, 
    val = Serial.read();           // read it and store it in val 
  } 
  if (val == 'H') {                // If H was received
    Serial.println("H Receive it");
    digitalWrite(ledPin, HIGH);    // turn the LED on 
  } else if (val == 'L') { 
    Serial.println("L Receive it");
    digitalWrite(ledPin, LOW);     // Otherwise turn it OFF
  } 
  delay(100);                      // Wait 100 milliseconds for next reading 
}