code: public function deviceSet($device)
      {
          if ($this->_dState !== SERIAL_DEVICE_OPENED) {
              if ($this->_os === "linux") {
                  if (preg_match("@^COM(\\d+):?$@i", $device, $matches)) {
                      $device = "/dev/ttyS" . ($matches[1] - 1);
                  }
  
                  if ($this->_exec("stty -F " . $device) === 0) {
                      $this->_device = $device;
                      $this->_dState = SERIAL_DEVICE_SET;
  
                      return true;
                  }
              } elseif ($this->_os === "osx") {
                  if ($this->_exec("stty -f " . $device) === 0) {
                      $this->_device = $device;
                      $this->_dState = SERIAL_DEVICE_SET;
  
                      return true;
                  }
              } elseif ($this->_os === "windows") {
                  if (preg_match("@^COM(\\d+):?$@i", $device, $matches)
                          and $this->_exec(
                              exec("mode " . $device . " xon=on BAUD=9600")
                          ) === 0
                  ) {
                      $this->_winDevice = "COM" . $matches[1];
                      $this->_device = "\\.com" . $matches[1];
                      $this->_dState = SERIAL_DEVICE_SET;
  
                      return true;
                  }
              }
  
              trigger_error("Specified serial port is not valid", E_USER_WARNING);
  
              return false;
          } else {
              trigger_error("You must close your device before to set an other " .
                            "one", E_USER_WARNING);
  
              return false;
          }
      }
docs: Device set function : used to set the device name/address.
  -> linux : use the device address, like /dev/ttyS0
  -> osx : use the device address, like /dev/tty.serial
  -> windows : use the COMxx device name, like COM1 (can also be used
  with linux)
  
  @param  string $device the name of the device to be used
  @return bool