C＃SerialPort侦听端口

Question

I am trying to do a serial communication between my micro processor and c# form application.

The problem is, data which comes from micro processor can come in 2 seconds or 5 seconds or 10 seconds. I mean there is no specific time and i would like to listen port and get data if it is come in 2 seconds if it is not, wait for the data until it comes.

I tried to this with serialport.readline(); but form hangs on while readline blocking, so i tried to do with backgroundworkers when i do this, i cant close form while backgroundworker is busy because readline command blocks the whole program.

All i am saying is, please give me some clue about listening the port while coming data time is not specific.

Thank you for your time (sorry for english it is not well)

Answer 1

You can use the SerialPort.DataReceived Event to get the data async. After you created an instance of the SerialPort class, you are able to add event handlers to the SerialPort . Thes event handlers are called if data was received.

mySerialPort.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler);

Inside the handler you can read the data from the input buffer and do what ever you want with it.

private static void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{
    SerialPort sp = (SerialPort)sender;
    string indata = sp.ReadExisting();
    //Do what ever you want with the data
}

This is a very common solution to get data in unregular time steps which runs your application without blocking it.

Answer 2

You can use the DataReceived event. It will be fired everytime new data arrives at your port. You need to register to it like this:

SerialPort port = new SerialPort(/*your specification*/);
port.DataReceived += Port_DataReceived;

In the event handler you would then read out the incoming data

private void Port_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
    SerialPort port = sender as SerialPort;

    if (port != null)
    {
        var incoming_message = port.ReadExisting();
    }
}

Now you just need to open the port and it will listen automatically. NOTE! the incoming data will arrive on a different thread than the main thread. So if you want to use controls of your form for display you need to use BeginInvoke

If your data is marked at the end with \\n you could try using the ReadLine method:

var incoming_message = port.ReadLine();

Or you could try ReadTo

var incoming_message = port.ReadTo("\n");

EDIT:

If it is such a long time, than you should read it in batches. You could also try to handle it in a while loop.

private void Port_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
    SerialPort port = sender as SerialPort;

    string message = "";
    if (port != null)
    {

        while(port.BytesToRead > 0)
        {
            message += port.ReadExisting();
            System.Threading.Thread.Sleep(500); // give the device time to send data
        }
    }
}

EDIT 2:

If you want to store the data declare a List<string> outside of the event handler and add the string when it is entirely read.

List<string> dataStorage = new List<string>();


private void Port_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
    SerialPort port = sender as SerialPort;

    string message = "";
    if (port != null)
    {

        while(port.BytesToRead > 0)
        {
            message += port.ReadExisting();
            System.Threading.Thread.Sleep(500); // give the device time to send data
        }
        // add now the entire read string to the list
        dataStorage(message);
    }
}

Since the event handler does not know whether you have send A or B just collect the entire received messages in one list. You know the order in which you have send your commands, so later you can take out the corresponding message and use Split to get the 400 entries in an array:

string [] A_array_data = dataStorage[0].Split(" ");