System.IO.IOException: A device attached to the system is not functioning C# .NET 4.0

Question

I\'ve built a C# application which reads and writes data from a serial port. The device connected to the serial port is a FTDI USB to serial converter which communicates to hard

Answer 1

I use intensively SerialPort class to communicate continuously with PLCs through USB Adapters for months without any break. So I cannot agree who says SerialPort .NET class does not work. Try to insert creation of class into thread, here is a sample of code with BackgroundWorker.

    void ThreadEngine_DoWork(object sender, DoWorkEventArgs e)
    {
        // Do not access the form's BackgroundWorker reference directly.
        // Instead, use the reference provided by the sender parameter.
        BackgroundWorker objBackgroundWorker = sender as BackgroundWorker;

        try
        {
            mSerialPort = new SerialPort(GetPortName(mPortName), DefaultBaudRate, Parity.Even, 7, StopBits.Two);
            mSerialPort.Open();
            objBackgroundWorker.ReportProgress(0);

            while (objBackgroundWorker.CancellationPending == false)
            {
                if (IOScanner(objBackgroundWorker, false) == true)
                {
                    ScannerStationData();
                    IsReady = true;
                    IsError = false;
                }
                else
                {
                    IsReady = false;
                    IsError = true;
                }
                Thread.Sleep(1);
            }

            // Performs last scan before thread closing
            if (objBackgroundWorker.CancellationPending == true)
            {
                IOScanner(objBackgroundWorker, true);
            }

            mSerialPort.Close();
            mSerialPort = null;
            e.Result = null;
        }
        catch (Exception objErr)
        {
            string sMessage = string.Format("PlcService.ThreadEngine_DoWork Err={0}", objErr.Message);
            mLogSysService.AddItem(sMessage);
            IsError = true;
        }
    }

Method IOScanner calls other methods for to communicate like following one.

    protected bool WriteDMWord(int iAddress, int[] aryValues)
    {
        bool bRetValue = true;
        try
        {
            mSerialPort.NewLine = "\r";
            mSerialPort.ReadTimeout = DefaultTimeout;
            string sTxData = HostLinkProtocol.BuildWriteDMWord(iAddress, aryValues);
            mSerialPort.WriteLine(sTxData);

            string sRxData = string.Empty;
            sRxData = mSerialPort.ReadLine();
            if (HostLinkProtocol.ParseWriteDMWord(sRxData) == true)
            {
                bRetValue = true;
            }
        }
        catch (Exception objErr)
        {
            Console.WriteLine("WriteDMWord [{0}]", objErr.Message);
            bRetValue = false;
        }
        return bRetValue;
    }