CODEWITHSUNDEEP
c#
Coolguy
Coolguy

Reputation: 2285

Can I do a timer loop and timeout for serial port communication in C#?

I'm more familiar with C language and recently I've been ask to do C# for serial communication. Below is my code for receiving data from COM port:

public void RxData()
{
    int i = 0;
    int Data;
    bool StartRx = false;
    int timer;

    while (true)
    {
        Data = sp.ReadByte();
        if (Data == 0x01)
        {
            StartRx = true;
        }
        if (StartRx == true)
        {
            RxBuffer[i++] = Data;
        }
        if (Data == 0x04)
        {
            RxChkSum = RxBuffer[i - 2];
            break;
        }
        timer++;
        if(timer>100) 
        {
            timer = 0;
            break;
        }
    } 
}

Above is the way I receive data starting with 0x01 and ends with 0x04.

I'm incrementing a timer to count til 100 and quit the while loop in case I don't receive any data. Some sort like a timeout.

But seems like the timer don't work. When I don't receive any data, my program just stuck in the while loop forever.

I know this is the way we write in embedded c programming. But is this the right way to write in C#?

Upvotes: 2

Views: 1246

Answers (2)

PVitt
PVitt

Reputation: 11770

ReadByte is a synchronous call. It will only return when there is a byte read.

To have your attempt getting to work you can check for available data before reading:

if(sp.BytesToRead > 0)
{
    Data = sp.ReadByte();
}

Besides that I prefer asynchronous reading as hmqcnoesy suggested.

Upvotes: 1

hmqcnoesy
hmqcnoesy

Reputation: 4224

I think you might be interested in handling data coming from the serial port using an event handler. In the .net SerialPort class, you can register an event handler for data received:

var sp = new SerialPort("COM1") {
    BaudRate = 9600,
    Parity = Parity.None,
    StopBits = StopBits.One,
    DataBits = 8,
    Handshake = Handshake.None
};

sp.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler);

You can also set the ReceivedBytesThreshold property on the SerialPort, which determines when your event handler will get fired.

Then, you just set up your event handler to read data and do what you need with it:

private static void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{
    SerialPort sp = (SerialPort)sender;
    string data = sp.ReadExisting();
}

Using this type of pattern, you don't have to loop, you just set the threshold you need, and let the framework call your event handler when the serial port's got that many bytes ready for you.

Hopefully that helps and I haven't missed your point completely. :)

Upvotes: 2

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