code2

// The code is from https://opentutorials.org/module/2106/12247

unsigned char c;  // variable to store the received character
  
void setup() {
  Serial.begin(9600);   // setup serial
}
  
void loop() {
  
  if(Serial.available() > 0){
      c = Serial.read();   // read the character
      Serial.write(c);     // echo
    }
}