[fb69]

Hi all,
I've 2 buttons. Button Connect(open com port) & Disconnect(close port). When I click on the connect button, the timer will trigger and display the data on Listbox from the com port every few seconds. When I click disconnect and click connect button again, the data will not be displayed on the Listbox and the timer is not triggered. Why is that so?

Here;s my code: (Using C# Windows Form VS2008)

 System.Timers.Timer timer = new System.Timers.Timer();       
        List<byte> buffer = new List<byte>(125);


        public ReadData()
        {
            InitializeComponent();
            
            timer.Interval = 5000;
            timer.Elapsed += new ElapsedEventHandler(TimerElapsed);
          
        }
 private void btnConnect_Click(object sender, EventArgs e)
    {
 
        if (serialPortN.IsOpen)
            serialPortN.Close();
        try
        {
            {
 
                serialPortN.PortName = "COM8";
                serialPortN.BaudRate = 9600;
                serialPortN.Parity = Parity.None;
                serialPortN.DataBits = 8;
                serialPortN.StopBits = StopBits.One;
                serialPortN.Encoding = System.Text.Encoding.ASCII;
                serialPortN.ReadTimeout = 500;
            }
 
            serialPortN.Open();
            label1.Text = "COM8" + " is opened";
 
            
            timer.Start();
 
            serialPortN.DataReceived += new SerialDataReceivedEventHandler(datareceived);
 

            btnDisconnect.Enabled = true;
            btnConnect.Enabled = false;
 
        }
 
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message.ToString());
        }
    }
     void datareceived(object sender, SerialDataReceivedEventArgs e)
    {
        myDelegate d = new myDelegate(update);
        listBox1.Invoke(d, new object[] { });
 
    }
 
    public void update()
    {
 
        while (serialPortN.BytesToRead > 0)
            buffer.Add((byte)serialPortN.ReadByte());
        // Call a routine to process the data.          
        ProcessBuffer(buffer);
     }
 
  private void ProcessBuffer(List<byte> buffer)
    {
       int numberOfBytesToRead = 125;
        if (buffer.Count >= numberOfBytesToRead)
        {
//To display data on the console output
            this.Invoke(new Action(() =>
             Console.WriteLine(string.Format("SPO = {0}, PulseRate = {1}, Time = {2}",
                                                    buffer[43].ToString(),
                                                    buffer[103].ToString(),
                                                    DateTime.Now.ToString()
            ))));
 
            buffer.RemoveRange(0, numberOfBytesToRead);
        }
 
    }
 
   void TimerElapsed(object sender, ElapsedEventArgs e)
    {
 
        int numberOfBytesToRead = 125;
        if (buffer.Count >= numberOfBytesToRead)
        {
//To display data on the LISTBOX
            this.Invoke(new Action(() =>
            listBox1.Items.Add(string.Format("SPO = {0}, PulseRate = {1}, Time = {2}",
                                                    buffer[43].ToString(),
                                                    buffer[103].ToString(),
                                                    DateTime.Now.ToString()
            ))));
            buffer.RemoveRange(0, numberOfBytesToRead);
 
        }
 
  private void btnDisconnect_Click(object sender, EventArgs e)
        {
           
            listBox1.Items.Clear();
            serialPortN.Close();
            buffer.Clear();
}

Thanks all.

[tlhIn`toq]

Why the timer? Just react to when the data comes in. Its a huge waste of CPU cycles to poll like that. Its just plain bad practice.

Personally, instead of trying to fix this so the timer works I'd invest my time in getting rid of the timer and react to the SerialPort.DataReceived.

Tutorial:
http://www.dreaminco...cation-in-c%23/

[eclipsed4utoo]

Why are you using a timer? Simply use the DataReceived event and work from it. You don't need a timer. When the data comes in, read it from the SerialPort, then write it to the ListBox.

Also, notice that you are subscribing to the DataReceived event in the Connect button click. That's going to cause you weird problems because you never unsubscribe. So the second time you click the Connect button, you will now have two subscriptions to the event, which means it will fire twice. Then the third time you click the Connect button, you will have three subscriptions, which means it will fire three times everytime data is received.

[fb69]

tlhIn`toq, on 06 February 2012 - 06:21 AM, said:

Why the timer? Just react to when the data comes in. Its a huge waste of CPU cycles to poll like that. Its just plain bad practice.

Personally, instead of trying to fix this so the timer works I'd invest my time in getting rid of the timer and react to the SerialPort.DataReceived.

Tutorial:
http://www.dreaminco...cation-in-c%23/

Hi, I insert the timer coz I would the data to be displayed every 5 seconds.. How can I do it without inserting the timer? Is there any codes? Thanks.

[tlhIn`toq]

You want to deliberately slow down the display to every 5 second instead of showing the data immediately when it comes in? Really?

[fb69]

eclipsed4utoo, on 06 February 2012 - 06:32 AM, said:

Why are you using a timer? Simply use the DataReceived event and work from it. You don't need a timer. When the data comes in, read it from the SerialPort, then write it to the ListBox.

Also, notice that you are subscribing to the DataReceived event in the Connect button click. That's going to cause you weird problems because you never unsubscribe. So the second time you click the Connect button, you will now have two subscriptions to the event, which means it will fire twice. Then the third time you click the Connect button, you will have three subscriptions, which means it will fire three times everytime data is received.

I would like the data to be displayed every 5 seconds on the listbox. How do I unsubscribe the event? Where is the best place to put my event? Sorry, coz i'm unsure Thanks!

[fb69]

tlhIn`toq, on 06 February 2012 - 06:47 PM, said:

You want to deliberately slow down the display to every 5 second instead of showing the data immediately when it comes in? Really?

Hi, I don't wanna slow down the process.. If I were to slow down the process, the data displayed on the listbox will not be in realtime.. If I didn't insert the timer, it'll read the data continuously every seconds.. which makes it kinda difficult to read on the listbox.. Hmm..

[tlhIn`toq]

If you wait 5 second to display, its not in real time either.

If you read only when data comes in THAT is real time.

Are you saying you have data CONTINUOUSLY with no break?
If that were the case then you would be lagging behind badly because of the delay.

If you have CONTINUOUS data and display it as it comes in...

or have CONTINUOS data and only show chunks of it ever 5 seconds, how does it make it any better? Either the user can read as fast as the data comes in or they can't.

I honestly think you don't understand the data coming in, or the idea of responding to the datareceived event.

[eclipsed4utoo]

fb69, on 06 February 2012 - 09:54 PM, said:

eclipsed4utoo, on 06 February 2012 - 06:32 AM, said:

Why are you using a timer? Simply use the DataReceived event and work from it. You don't need a timer. When the data comes in, read it from the SerialPort, then write it to the ListBox.

Also, notice that you are subscribing to the DataReceived event in the Connect button click. That's going to cause you weird problems because you never unsubscribe. So the second time you click the Connect button, you will now have two subscriptions to the event, which means it will fire twice. Then the third time you click the Connect button, you will have three subscriptions, which means it will fire three times everytime data is received.

I would like the data to be displayed every 5 seconds on the listbox. How do I unsubscribe the event? Where is the best place to put my event? Sorry, coz i'm unsure Thanks!

To unsubscribe, you use a - instead of a +...

subscribe

serialPortN.DataReceived += new SerialDataReceivedEventHandler(datareceived);

unsubscribe

serialPortN.DataReceived -= new SerialDataReceivedEventHandler(datareceived);

The best place should be where you instantiate the SerialPort object. So whereever you have SerialPort serialPortN = new SerialPort();, then that's where you would subscribe to the DataReceived event.