Question

I am trying to get data from a serial port continuously in a very fast speed. The baud rate is 230400.
When I print out the data, time stamp and also BytesToRead in to a file, I noticed a 200ms delay happens whenever BytesToRead drops to a single digit and readLine() is not reading anything in that 200ms. After the delay, BytesToRead goes back to around 3000 and this process happens again and again. Essentially I am not getting data continuously.

I thought maybe I am reading faster than the speed data accumulate in the buffer so I tried changing readBuffer size and put this thread to sleep for 1ms in order to let buffer keep up the speed I am reading. None of them worked. There are still some delays.

Any thoughts is welcomed.

 private void dostuff()//The thread I created after the port is opened
    {
        var startTime = DateTime.Now;
        var stopwatch = Stopwatch.StartNew();
        while (serialPortEncoder.IsOpen)
        {
            if (serialPortEncoder.BytesToRead > 210)
            {
                try
                {
                    var line = serialPortEncoder.ReadLine();
                    var timestamp = (startTime + stopwatch.Elapsed);
                    var lineString = string.Format("{0}  ----{1}",
                                    line,
                                    timestamp.ToString("HH:mm:ss:fff") + " "+serialPortEncoder.BytesToRead+"\r\n");

                    richTextBoxEncoderData.BeginInvoke(new MethodInvoker(delegate()
                    {
                        richTextBoxEncoderData.Text = line;//update UI                           
                    }));                                     
                }
                catch (Exception ex) { MessageBox.Show(ex.ToString()); }


            }}

Answer 1

Unless there’s a line feed every 210 bytes, your ReadLine() function is probably timing out and returning nothing. ReadLine() will read the input buffer till it encounters a newline value, then return whatever data was before it. http://msdn.microsoft.com/en-us/library/system.io.ports.serialport.readline.aspx

What kind of information is coming across the port? If you want to read a specific size buffer, just use the Read method. If you need to read till there’s a line feed, use ReadLine() and check every so often to see if it returns a string.