就是事先选择好某个数值，然后按设定按钮。
是有串口指令的。
   
private void button3_Click(object sender, EventArgs e)
        {
             Thread.Sleep(500);
            if (comboBox5.Text == "2400")
                hexSend("FC00990607");
            else if (comboBox5.Text == "4800")
                hexSend("FC00990606");
            else if (comboBox5.Text == "9600")
                hexSend("FC00990601");
            else if (comboBox5.Text == "19200")
                hexSend("FC00990602");
            else if (comboBox5.Text == "38400")
                hexSend("FC00990603");
            else
                hexSend("FC00990604");

        }