#include <SoftwareSerial.h> // Arduino 
            SoftwareSerial mySerial(0, 1); // RX, TX
            char incomingByte;
            
            void setup() {
              mySerial.begin(9600);
              pinMode(LED_BUILTIN, OUTPUT);
             
            }
            
            void loop() {
            
                   mySerial.write('A');
                   digitalWrite(LED_BUILTIN, HIGH);
                   delay(1000);
                    digitalWrite(LED_BUILTIN, LOW);
                  delay(1000);
                
                  incomingByte = mySerial.read();
              mySerial.print(incomingByte);
              
                }