How to read data from serial port and write to serial port?

Question

Hi I'm writing an application in c# to connect to a device via rs232(com) port. I need to send a "read" command to read data from it and a "write" command to send some data to it.

I read some articles in here and some other sites and I know there are some methods when I'm defining a serial port in c#.

but my question is ,should I be concerned about DTR ,RTS ,... ? what are they for? How do I use them?

Solution 1

Just to give you an idea this is a very simple function that writes a command as a byte array on a serial and reads corresponding input from serial port (in this example I read only the fourth byte of the value read from the serial port):

private string ReadFromSerial()
{
    try
    {
        System.IO.Ports.SerialPort Serial1 = new System.IO.Ports.SerialPort("COM1", 9600, System.IO.Ports.Parity.None, 8, System.IO.Ports.StopBits.One);
        Serial1.DtrEnable = true;
        Serial1.RtsEnable = true;
        Serial1.ReadTimeout = 3000;

        var MessageBufferRequest = new byte[8] { 1, 3, 0, 28, 0, 1, 69, 204 };
        var MessageBufferReply = new byte[8] { 0, 0, 0, 0, 0, 0, 0, 0 };
        int BufferLength = 8;

        if (!Serial1.IsOpen)
        {
            Serial1.Open();
        }

        try
        {
            Serial1.Write(MessageBufferRequest, 0, BufferLength);
        }
        catch (Exception ex)
        {
            logEx(ex);
            return "";
        }

        System.Threading.Thread.Sleep(100);

        Serial1.Read(MessageBufferReply, 0, 7);

        return MessageBufferReply[3].ToString();
    }
    catch (Exception ex)
    {
        logEx(ex);
        return "";
    }
}

Solution 2

Here is a link to the MSDN documentation that you should find really helpful: the documentation. There are some properties for what you are looking for and some good examples.

Comments

[CodeCaster]

See Reading from and Sending data to Serial port.

[user2628363]

very informative thanks. Another question: If I want to read several times ,'Serial1.IsOpen' should be the condition for the loop or something else?

[Andrea]

@user2628363 Yes, you can create a loop While(Serial1.IsOpen) that keeps on writing/reading on the port.

[user2628363]

thanks and what are dtr and rts for?

[Andrea]

@user2628363 They're for hardware flow control; for correct usage you should check the documentation of the device you want to communicate with