wrong data coming from LIS analyzer abacus diatron 380

Question

i have below code when i execute the machine, the machine returns "q?". which is not suitable that i want from machine. what i do please please help....

public void SettingRS232()
{
    try
    {
        serialPort1.PortName = comportName.Text;
        serialPort1.BaudRate = Convert.ToInt32(combaudrate.Text);
        serialPort1.DataBits = Convert.ToInt32(comdatabits.Text);
        serialPort1.StopBits = (StopBits)Enum.Parse(typeof(StopBits), comstopBits.Text);
        serialPort1.Parity = (Parity)Enum.Parse(typeof(Parity), comparityBits.Text);
        serialPort1.Handshake = (Handshake)Enum.Parse(typeof(Handshake), comparityBits.Text);
        serialPort1.ReadTimeout = 2000;
        serialPort1.WriteTimeout = 500;

        serialPort1.DtrEnable = true;
        serialPort1.RtsEnable = true;

        serialPort1.Open();

        serialPort1.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler);
        lblstatus.Text = "Port is now ready...";

    }
    catch (Exception ex)
    {
        lblstatus.Text = ex.Message;
    }
}
public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{
    SerialPort sp = (SerialPort)sender;
    string indata = sp.ReadExisting();

    this.Invoke(new Action(delegate() { richTextBox1.Text = indata; }));
}
private void btnStart_Click(object sender, EventArgs e)
{
    if (serialPort1.IsOpen)
    {
    }
    else
    {
         btnStart.BackColor = Color.Green;
         SettingRS232();
         btnStop.BackColor = default(Color);
    }
}