C# winforms 冻结：串口、定时器、线程

Question

Edit: Keeping the original question for continuity. I then edited the question with replacement code for the ReadLine() method by using ReadExisting instead. It works however I still have the same freeze, where the app becomes unresponsive. Debug says it's locking (it takes a while to freeze, sometimes seconds, sometimes minutes) in the while () {} function where I wait for the complete message. More explanations below:

-- obsolete --

What is a good way to handle serialport.readtimeout exception?

                    try
                    {
                        serialPort1.Write(Command_);
                        if (!IsWriteComm_)
                        {
                            Response_ = serialPort1.ReadLine().Replace("\r", "");
                        }
                    }
                    catch (TimeoutException err)
                    {
                        DateTime d = DateTime.Now;
                        rtboxDiag.AppendText("\n" + d.ToString("HH:mm:ss") + ": ");
                        rtboxDiag.AppendText(err.Message);
                        if (!serialPort1.IsOpen)
                            InitConnection();
                        return Textbox_;
                    }

this bit of code is exectuted on a timer tick event. I was having a weird "crash" of the app with an IO exception

"The I/O operation has been aborted because of either a thread exit or an application request."

no matter what I do I am not able to "recover" meaning, I am no longer able to poll data from the serial port.

I added this exception catch and it does log the exception. weirdly enough the test on.serialport.isopen is false (meaning the port is still open).

What might be a hint is: this error does STOP the timer somehow, this is not something I am doing in code. so I am suspecting something related to the timer, rather than the serialport, but I could be wrong.

Closing the port manually, and reconnecting does not fix the problem. Disconnecting and reconnecting the USB does not fix the problem.

however, closing the app, and relaunching the app does fix the problem (without even disconnecting the MCU or power cycling the MCU/hardware).

-- /obsolete --

edit: the problem is appearing after a few seconds, sometimes minutes of flawless operations. I cannot repeat the issue using a serialport terminal polling the data the same way, at the same frequency. It seems the problem is not coming from the hardware itself.

cheers

Edit: I have yet to test the following modification, not sure if it will fix this problem (I doubt), but at least it's an attempt at not using.readline() which from what I've gathered is not good practice.

anyway here it is:

                    try
                    {
                        serialPort1.Write(Command_);
                        if (!IsWriteComm_)
                        {
                            while (!SerialRxCplt) ;
                            Response_ = SerialRxResponse.Replace("\r", "").Replace("\n", "");
                            SerialRxCplt = false;
                            //Response_ = serialPort1.ReadLine().Replace("\r", "");
                        }
                    }
                    catch (TimeoutException err)
                    {
                        DateTime d = DateTime.Now;
                        rtboxDiag.AppendText("\n" + d.ToString("HH:mm:ss") + ": ");
                        rtboxDiag.AppendText(err.Message);
                        if (!serialPort1.IsOpen)
                            InitConnection();
                        return Textbox_;
                    }

and I have the datareceived event enabled:

private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
        {
            var serialPort = (System.IO.Ports.SerialPort)sender;
            string dataReceived = serialPort.ReadExisting();
            ProcessSerialData(dataReceived);
        }

and this is how I am processing the data, and manually "waiting" for the \n character which tells me when the data has been fully received.

private void ProcessSerialData(string data)
        {
            SerialRxBuffer += data;
            if (SerialRxBuffer.Contains("\n"))
            {
                SerialRxCplt = true;
                SerialRxResponse = SerialRxBuffer;
                SerialRxBuffer = "";
            }
            else
            {
                SerialRxCplt = false;
            }
        }

any input is welcome.

I have added "stuff" for debugging inside that while loop and it does work fine for a while and then freezes, no error or exception is thrown there. For some reason I have a feeling it's not related to the serial port. I have even added this:

                    try
                    {
                        serialPort1.Write(Command_);
                        if (!IsWriteComm_)
                        {
                            Stopwatch stopWatch = new Stopwatch();
                            stopWatch.Start();
                            while (!SerialRxCplt || Timer2StopWatchMilli > 5)
                            {
                                Timer2StopWatchMilli = stopWatch.Elapsed.TotalMilliseconds;
                                ExceptionMessage = Timer2StopWatchMilli.ToString();
                                IsException = true;
                            }
                            stopWatch.Stop();
                            if (!SerialRxCplt)
                                return Textbox_;
                            Response_ = SerialRxResponse.Replace("\r", "").Replace("\n", "");
                            SerialRxCplt = false;
                            //Response_ = serialPort1.ReadLine().Replace("\r", "");
                        }
                    }

the ExceptionMessage and IsException help me have an idea of what's happening in that loop. And in normal operations, it is what you would except, increments in the order of 0.0x milliseconds. Data is being processed correctly. When it freezes, nothing looks abnormal. I initially thought I was somehow getting "stuck" in an infinite loop but that || Timer2StopWatchMilli > 5 should get me out of it, acting as some sort of timeout.

one extra piece of info: when it freezes, the one CPU core is fully loaded. (I have a 6core CPU, and it's 16-17% in the task manager - memory usage is low < 30MB)

Any help is welcome

Answer 1

I fixed it by clearing RX/TX and stream buffers after each successful transaction. I think data was being sent to the PC faster than it was able to read causing data to eventually accumulating on the Rx Buffer.

private void SerialPortClearBuffers()
        {
            serialPort1.DiscardOutBuffer();
            serialPort1.DiscardInBuffer();
            serialPort1.BaseStream.Flush();
        }