How to get the BaudRate of the device?

Question

I'd like to know if there is a way to get the Baud Rate when it's connected on the RS232 port
BEFORE you initialize the SerialPort class and set it's values. Let me try to explain the reason for that...

Today, I'm working with two different RFID Reader devices, each one works on a different BaudRate, so if I set a wrong baudrate when I create the SerialPort class, it will read the card id all wrong, instead get the real card's id, it will get something like ????|W2???.
Also, there's a possibilite that the device have a USB port.

That's why I'd like to know the device's baud rate before I instantiate the SerialPort class.

Answer 1

I tried for my serial usb devices. Keep changing the baud rate and check. ComboBox contains series of possible baudrates.

    public void initConfig(SerialPort serialPort)
    {
        // you can assign these values in a combo box
        string[] ports= "{COM1", "COM2", "COM3", "COM4", "COM5", "COM6", "COM7", "COM8"};

        //you can assign these values in a combo box in a string format
        int[] baudRate = { 4800, 9600, 19200, 38400, 57600, 115200, 230400 };

        serialPort.PortName = ports[0]; //else get from combobox  : portCombobox.SelectedItem
        serialPort.BaudRate = baudRate[0];
        //serialPort.BaudRate = Int32.Parse(speedComboBox.SelectedItem.ToString());

        //you can have controls to store and change these values if required
        serialPort.Handshake = System.IO.Ports.Handshake.None;
        serialPort.Parity = System.IO.Ports.Parity.None;
        serialPort.DataBits = 8;
        serialPort.StopBits = System.IO.Ports.StopBits.One;
        serialPort.ReadTimeout = 200;
        serialPort.WriteTimeout = 50;
    }

change the strings into respective types and call open.

finally:

    public void callingMethod() //or your connect event attached control
    {
        SerialPort serialPort = new SerialPort();

        initConfig(serialPort);

        try
        {
            serialPort.Open();
        }
        catch
        {
            MessageBox.Show("Error: Unable to Open the serial interface !");
            return;
        }
    }

Answer 2

Depending upon the details of what you connect to etc. You can loop through a list of baud rates, attempt to connect and then perform an echo test. If you connect at the wrong rate, your echo will be returned as garbage instead of the string you sent. This methodology is working for me.