     pressed_at(0),
     pin_number(pin_number_) {
     pinMode(pin_number, INPUT);
+    digitalWrite(pin_number, HIGH); // connect the internal pull-up resistor
   };
 
   // returns the number of ms for which the button has been held down

/* 
* TODO:
* reset button (chronos style?) - P1
* time setting - P1
* case - P1
* wiring diagram - P2 S3

    int pin_status = digitalRead(pin_number);
    // serprintf("PollButton::poll: status is %d (%s)\r\n", pin_status, pin_status == HIGH ? "high" : "not high");

    if (pin_status == LOW) {
      if (!pressed) {
        pressed_at = millis();
        pressed = true;
