private void init()
        {
            try
            {
                List <string> list  = new List <string>();
                string[]      ports = USB.getPorts(); //SerialPort.GetPortNames();//

                comboBox_port.Items.Clear();
                for (int i = 0; i < ports.Length; i++)
                {
                    comboBox_port.Items.Add(ports[i]);
                }
                if (ports.Length > 0)
                {
                    comboBox_port.SelectedIndex = ports.Length - 1;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
 public PMT200()
 {
     InitializeComponent();
     usb = new USB();
     init();
 }