code: function(callback) {
      if (!this._decodeModes) {
        this.setDecodeNone();
      }
  
      for (var i = 0; i < this._decodeModes.length; i++) {
        var mode = this._decodeModes[i];
        if (mode == 0) {
          this.setDigitSegmentsByte(i, 0x00, callback);
        } else {
          this.setDigitSymbol(i, " ", false, callback);
        }
      }
    }
docs: Sets all segments for all digits off.
  
  Shortcut for manually calling setDigitSegments or setDigitSymbol
  with the appropriate params. If a decode mode wasn't specifically set
  beforehand, no-decode mode is assumed.
  
  @param function callback [optional]
  Invoked once the write to the SPI device finishes.