private void btnOpenTestPort_Click(object sender, EventArgs e)
        {
            //Load settings from text boxes
            testPort.PortName = ctbTestPort.Text;
            testPort.BaudRate = ctbTestBaud.Text;
            testPort.DataBits = ctbTestDataBits.Text;
            testPort.Parity   = ctbTestParity.Text;
            testPort.StopBits = ctbTestStopBits.Text;

            //subscribe to event handlers
            testPort.SerialDataReadyEvent += testPort_SerialDataReadyEvent;

            //check if port is open
            if (testPort.OpenSerialPort())
            {
                tbTestDebugOut.AppendText(testPort.PortName + " at " + testPort.BaudRate + " baud is open\n");
            }

            else
            {
                tbTestDebugOut.AppendText("Error: " + testPort.ReadSerialData() + "\n");
            }
        }