anchor.diff:      return completer.future;
     }
   
  -  // TODO rename sendString ?
  +  /// Write as a string
     Future<bool> writeString(String data){
       _checkOpen();
       final completer = new Completer<bool>();
  
positive.code:     return completer.future;
    }
  
    Future<bool> write(List<int> bytes){
      // TODO have a real c implementation for send by bytes
      final writes = bytes.map((byte) => _writeOneByte(byte));
  
negative.code: 
    SerialPort(this.portname, {this.baudrate : 9600, this.databits: 8});
  
    /// Open the connection with serial port.
    Future<bool> open() {
      if(_ttyFd != -1){
        throw new StateError("$portname is yet open.");
  