/*
  AnalogReadSerial
 Reads a character from serial, an 'A', and returns a 'B' if it's an 'A'.
 */

void setup() {
  Serial.begin(9600);
}

void loop() {
  char val;
  if(Serial.available() > 0){
    val = Serial.read();
    if (val == 'A'){
      Serial.println('B');
    }
    else{
      Serial.write(val);
    }
  }
}