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Serial Ports and Threading

Posted on 2007-12-06
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Last Modified: 2013-12-03
I am writing a code that will output a set of bit array through the com port and too hyperterminal on another computer.  I need to have this transfer till i press stop button on my GUI interface.  I know we need to use threading to do this task.  The code below outputs the bits to hyperterminal once.  I would like to know how to make it a constant loop till i press stop.  Suggestions would be wonderful.

 public void TransmitData()
        {
            byte[] bytearray = new byte[512];
            try
            {
                SerialPort port = new SerialPort("COM2", 9600, Parity.None, 8, StopBits.One);
                port.Open();
                for (int i = 0; i < 512; i++)
                {
                    bytearray[i] = (byte)array[i];
                }
                port.Write(bytearray, 0, 512);
                port.Close();
            }
            catch
            {
                MessageBox.Show("Please Connect Serial Cable");
            }
        }
0
Comment
Question by:jmkotman
6 Comments
 
LVL 6

Expert Comment

by:so3
ID: 20426071
Put 2 buttons on the form.
  private void button1_Click(object sender, EventArgs e)
        {
            TransmitData();
        }
 
        bool working = true;
        public void TransmitData()
        {
            byte[] bytearray = new byte[512];
            try
            {
                working=true;
                SerialPort port = new SerialPort("COM2", 9600, Parity.None, 8, StopBits.One);
                port.Open();
 
                while (working)
                {
                    Application.DoEvents();
                    if (!working) break;
                    port.Write("write data");
                }
                port.Close();
            }
            catch
            {
                MessageBox.Show("Please Connect Serial Cable");
            }
        }
 
        private void button2_Click(object sender, EventArgs e)
        {
            working = false;
        }

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0
 
LVL 3

Expert Comment

by:Dimkov
ID: 20426080
make while(1) loop inside the function
Created thread which points to this function.

Then you have command like thread.start, thread.stop, that tell when the thread sholud work or stop

just an idea :)
0
 
LVL 16

Accepted Solution

by:
gnoon earned 500 total points
ID: 20426165
Just an implementation of Dimkov's idea
// a shared flag indicate that writing data should be continue
bool _continue;
 
/// <summary>
/// Keep transmit data to COM2 port until stop is pressed.
/// </summary>
public void TransmitData(byte[] data)
{
    try
    {
        using(SerialPort port = new SerialPort("COM2", 9600, Parity.None, 8, StopBits.One))
        {
            port.Open();
            while(_continue)
            {
                port.Write(data, 0, data.Length);
                try{System.Threading.Thread.Sleep(100);}catch(Exception){}
            }
        }
    }
    catch(Exception)
    {
        MessageBox.Show("Please Connect Serial Cable");
    }
}
 
public void StartTransmitInAnotherThread()
{
    // make a copy of data
    byte[] data = new byte[512];
    for(int i=0; i<data.Length && i<array.Length; i++)
        data[i] = (byte)array[i];
 
    // start new thread of transmit
    System.Threading.Thread t = new System.Threading.Thread(this.TransmitData);
    t.Name = "SerialPortThread";
    t.IsBackground = true;
    t.Start(data);
}
 
private void btnStart_Click(object sender, System.EventArgs e)
{
    // prevent click start twice
    btnStart.Enabled = false;
    btnStop.Enabled = true;
 
    // set flag to keep writing data
    _continue = true;
 
    // start transmit
    StartTransmitInAnotherThread();
}
 
private void btnStop_Click(object sender, System.EventArgs e)
{
    btnStart.Enabled = true;
    btnStop.Enabled = false;
 
    // set flag to stop writing data
    _continue = false;
}

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Author Comment

by:jmkotman
ID: 20428813
I just implamented So3's code and it worked, but does that have anything to do with threading?  I am implamenting gnoon's code and i am receiving the compile error The best overloaded method match for 'System.threading.thread.thread(System.threading.threadstart)' has some invalid arguments.  This error is refering to: System.Threading.Thread t = new System.Threading.Thread(this.TransmitData);

Thanks for your help
0
 
LVL 6

Expert Comment

by:so3
ID: 20429363
No, my code is not with threading because i don't think that you need it. From what i understood you need to use only one function (with start and stop function). For what you need it will not take the processor so you can use it without threading(and also is a easy solution)
0
 
LVL 16

Expert Comment

by:gnoon
ID: 20433051
>i am receiving the compile error The best overloaded method match for 'System.threading.thread.thread(System.threading.threadstart)' has some invalid arguments
Sorry for that. I did not test it in VS before post.

Compile error because TransmitData does not matched with signature function needed by ParameterizedThreadStart class. It requires a function having a parameter of type Object.

Change the code of TransmitData to this, you will get it compiled

public void TransmitData(object param)
{
    byte[] data = (byte[]) param;
    try
    {
        ....
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