       _tft.begin();
       _tft.background(0, 0, 0);
 
+      analogReference(EXTERNAL);
+
       _pid.SetOutputLimits(0.0, 2000.0);
       _pid.SetMode(AUTOMATIC);
 

      : _p(2), _i(5), _d(1),
        _input(0), _output(0), _consign(0),
        _tft(TFT_CS, TFT_DC, TFT_RESET),
        _pid(&_input, &_output, &_consign, _p, _i, _d, DIRECT),
        _tc(TC_CS)
    {
      // Nothing to do...
    }

    {
      _buttons[0] = new Button(2);
      _buttons[1] = new Button(4);
      _buttons[2] = new Button(6);
      _buttons[3] = new Button(5);
    }

    void loop()
