// RECEIVE
#include <SoftwareSerial.h>

int led1 = 4;
int led2 = 8;
SoftwareSerial mySerial(A4, A5); // RX, TX

void setup() {
  Serial.begin(9600);
  mySerial.begin(9600);  
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);  
  digitalWrite(led1, LOW);
  digitalWrite(led2, LOW);  
}

void loop() { 
   if (mySerial.available() > 0) {
      char ul = mySerial.read(); // char value
      String inval = String(ul);
      Serial.println(inval); //output on monitor
      if ( inval == "A") // A = 65
      {
          digitalWrite(led1, HIGH);
          delay(200);
          digitalWrite(led1, LOW);
      }
      if ( inval == "B") // B = 66
      {
          digitalWrite(led2, HIGH);
          delay(200);
          digitalWrite(led2, LOW);
      }      
      inval = "";
  }
  delay(100);
}

//------------------------------------------ 

// SEND 
#include <SoftwareSerial.h>
int inPin0 = A0; // U3
int inPin1 = A1; // U3
int val = 0;

SoftwareSerial mySerial(A4, A5); // RX, TX

void setup()
{
  Serial.begin(9600);
  mySerial.begin(9600);
  pinMode(inPin0,INPUT);
  pinMode(inPin1,INPUT);  
}

void loop() // run over and over
{
  digitalWrite(inPin0, HIGH);
  digitalWrite(inPin1, HIGH);  
  delay(50);   
  //val = digitalRead(inPin); 
  if (digitalRead(inPin1) == LOW)
{
     Serial.print("A"); //output on monitor
     mySerial.print("A");
     delay(500);  
}   
   if (digitalRead(inPin0) == LOW)
{
     Serial.print("B"); //output on monitor
     mySerial.print("B");
     delay(500);  
} 
}