code: function MAX7219(device, count, callback) {
    this._activeController = 0;
    this._totalControllers = count || 1;
    this._buffer = new Buffer(this._totalControllers * 2);
  
    this._spi = new SPI.Spi(device, {
      mode: SPI.MODE.MODE_0,
      chipSelect: SPI.CS.low
    }, function(s) {
      s.open();
      process.nextTick(callback || function(){});
    });
  }
docs: MAX7219 abstraction.
  Please read the datasheet: https://www.adafruit.com/datasheets/MAX7219.pdf
  
  Example use:
  var disp = new MAX7219("/dev/spidev1.0");
  disp.setDecodeNone();
  disp.setScanLimit(8);
  disp.startup();
  disp.setDigitSegments(0, [0, 0, 1, 1, 0, 1, 1, 1]);
  disp.setDigitSegments(1, [0, 1, 0, 0, 1, 1, 1, 1]);
  disp.setDigitSegments(2, [0, 0, 0, 0, 1, 1, 1, 0]);
  disp.setDigitSegments(3, [0, 1, 1, 0, 0, 1, 1, 1]);
  
  Alternate use:
  var disp = new MAX7219("/dev/spidev1.0");
  disp.setDecodeAll();
  disp.setScanLimit(8);
  disp.startup();
  disp.setDigitSymbol(0, "H");
  disp.setDigitSymbol(1, "E");
  disp.setDigitSymbol(2, "L");
  disp.setDigitSymbol(3, "P");
  
  @param string device
  The SPI device on which the controller is wired.
  For example, "/dev/spidev1.0".
  @param number count [optional]
  The total number of controllers when daisy-chained. Defaults to 1.
  @param function callback [optional]
  Invoked once the connection to the SPI device is finished.