int prev = 0;
void setup() {
  pinMode(2, INPUT_PULLUP);
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
}

void loop() {
  int press = ! digitalRead(2);
  if(press != prev)
  {
    if(press) Serial.print("1");
    else Serial.print("0");
  }
  prev = press;
}