#include <SoftwareSerial.h> //Slave
SoftwareSerial mySerial(0, 1); // RX, TX

const char node = 'A'; // network address


int incomingByte;

void setup() {
  mySerial.begin(9600);
  pinMode(PA2, OUTPUT);
}

void loop() {

    incomingByte = mySerial.read();
    if (incomingByte == node) {
      digitalWrite(PA2, HIGH);   
     delay(1000);
      digitalWrite(PA2, LOW);   
       mySerial.write('B');

    }
  }