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Thread: SerialPort problems, readline() hangs when using win xp (fine on win 7)

  1. #1

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    SerialPort problems, readline() hangs when using win xp (fine on win 7)

    I am very new to VB.net so please be understanding!!

    I have based an application around some examples from the net. Basically I have a microprocessor connected to a serial port. The Micro does 2 main things, firstly it issues an identification string when powered on, then it waits for a sequence of parameters to configure it, following this it issues other status messages during later operation. My VB form has a rtb that displays the string/s captured on the serial port and a button that sends the sequence of parameters. To capture the identification (which can happen at anytime) I used this code to trigger a read event on any data.

    Code:
    Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
    ReceivedText(SerialPort1.ReadExisting())    ‘Automatically called every time a data is received at the serialPort
    End Sub
    
    Private Sub ReceivedText(ByVal [text] As String)
    ‘compares the ID of the creating Thread to the ID of the calling Thread
    If Me.rtbReceived.InvokeRequired Then
    Dim x As New SetTextCallback(AddressOf ReceivedText)
    Me.Invoke(x, New Object() {(text)})
    Else
    Me.rtbReceived.Text &= [text]
    End If
    End Sub

    Later on when a button is pressed I used this code to send a parameter and wait for a confirmation string back from the micro:


    Code:
    Private Sub btnSendParameters_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOn.Click
    
            Dim response As String
    
            Try
    
                SerialPort1.WriteLine(command)
                response = SerialPort1.ReadLine
    
    
            Catch ex As TimeoutException
                MessageBox.Show(ex.Message)
    
            Catch ex As InvalidOperationException
                MessageBox.Show(ex.Message)
    
            Catch ex As UnauthorizedAccessException
                MessageBox.Show(ex.Message)
    
            End Try
        End Sub
    Now this all works fine when compiled on a win7 machine. However when I deployed to an XP machine the application hangs at a readline() method. I have then tried to debug and rebuild it using vb.net express on the xp machine and found:

    If I comment out the line
    Code:
    ReceivedText(SerialPort1.ReadExisting())    ‘Automatically called every time a data is received at the serialPort
    it works but obviously stops any randomly arriving messages on the port. I think the line above is intercepting the response string before readline gets to see it. Why it works on win 7 and not xp is confusing!!

    So please if anyone can help me to understand what I am missing here I would be greatly appreciated - I 've been on it for days now, although I now see where the problem lies I am not sure how to about solving it.

    Thanks

    Bally

  2. #2
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    Re: SerialPort problems, readline() hangs when using win xp (fine on win 7)

    I am actually surprised that it works consistently anywhere. Depending on the timing you could be reading in the event handler OR the button click. The difference might be the framework you are targeting on the two machines.

    My advice is to ONLY receive data in the event handler. Take the data received and store it in a queue or list. Process it elsewhere, like a timer or separate thread.
    My First Computer -- Documentation Link (RT?M) -- Using the Debugger -- Prime Number Sieve
    Counting Bits -- Subnet Calculator -- UI Guidelines -- SerialPort Answer

    "Those who use Application.DoEvents have no idea what it does and those who know what it does never use it." John Wein
    "They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety." Benjamin Franklin
    "It is not all that I know that is the problem, it is all I think I do that is."

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    Re: SerialPort problems, readline() hangs when using win xp (fine on win 7)

    HI Thanks for the reply

    I will certainly think about how I can change things to avoid the uncertainty of which event gets the port data.

    I had another thought about using a boolean flag set by the button event to prevent the data being read in the datareceived event, (a simple if button pressed statement) - the datarecieved event would still occur but having not read anything the serial data would still be preserved ready for readline to be performed.

    Code:
    Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
    
    if buttonPressed = false then                     ‘Automatically called every time a data is received at the serialPort
    ReceivedText(SerialPort1.ReadExisting())     'Port read only if button was not being processed
    end if
    
    End Sub
    Would this work?.......

    Bally

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    Re: SerialPort problems, readline() hangs when using win xp (fine on win 7)

    Why have the event handler at all?
    My First Computer -- Documentation Link (RT?M) -- Using the Debugger -- Prime Number Sieve
    Counting Bits -- Subnet Calculator -- UI Guidelines -- SerialPort Answer

    "Those who use Application.DoEvents have no idea what it does and those who know what it does never use it." John Wein
    "They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety." Benjamin Franklin
    "It is not all that I know that is the problem, it is all I think I do that is."

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    Re: SerialPort problems, readline() hangs when using win xp (fine on win 7)

    After more head pounding I am left very confused.

    I dropped the serial receiving event and used just readline and write methods triggered simply by button presses. Still i get it hanging at readline.

    For example:

    Code:
        Private Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
            
            txtResponce.Clear()
            ClearBuffer = SerialPort1.ReadExisting       'just in case clear any previous data
            SerialPort1.Write("s")
            responce = SerialPort1.ReadLine              'expect to read back the char "E" in reponce
            txtResponce.Text &= responce
        End Sub
    There are now several other buttons to send out the other parts of the sequence, all following the code structure above. The following sequence of buttons pressed in turn would give: "1" , "1000" + vbcr , "500" + vbcr and finally "100" + vbcr. Completing the output sequence of command parameters.

    Now here's the thing that that's really killing me. If I use a win 7 machine the app runs fine. If I use hyperterminal to send out the sequence above that too works fine. As soon as I go near XP it fails......

    Not sure what to do now, but I am going to be avoiding high places for the foreseeable future

    Any help, suggestions, or debugging ideas will be hugely appreciated....

  6. #6
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    Re: SerialPort problems, readline() hangs when using win xp (fine on win 7)

    What version of .Net are you using? Does hyperterminal work on XP?
    Last edited by dbasnett; Jun 14th, 2013 at 09:19 AM.
    My First Computer -- Documentation Link (RT?M) -- Using the Debugger -- Prime Number Sieve
    Counting Bits -- Subnet Calculator -- UI Guidelines -- SerialPort Answer

    "Those who use Application.DoEvents have no idea what it does and those who know what it does never use it." John Wein
    "They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety." Benjamin Franklin
    "It is not all that I know that is the problem, it is all I think I do that is."

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    Re: SerialPort problems, readline() hangs when using win xp (fine on win 7)

    Taken from VB2010 about menu:

    Microsoft Visual Studio 2010
    Version 10.0.30319.1 RTMRel
    Microsoft .NET Framework
    Version 4.0.30319 RTMRel

    Installed Version: VB Express

    Microsoft Visual Basic 2010 01012-169-2510015-70468
    Microsoft Visual Basic 2010

    Security Update for Microsoft Visual Basic 2010 Express - ENU (KB2251489) KB2251489
    This security update is for Microsoft Visual Basic 2010 Express - ENU.
    If you later install a more recent service pack, this security update will be uninstalled automatically.
    For more information, visit http://support.microsoft.com/kb/2251489.

    Thanks Andy

  8. #8
    Powered By Medtronic dbasnett's Avatar
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    Re: SerialPort problems, readline() hangs when using win xp (fine on win 7)

    Does hyperterminal work on XP?

    An example using timer. Note that there is only one SerialPort read of any kind.

    Code:
    Public Class Form1
    
        Dim WithEvents timer1 As New System.Windows.Forms.Timer
    
        Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles Me.Shown
            'port setup and open
            Dim p() As String = IO.Ports.SerialPort.GetPortNames
            With SerialPort1
                .PortName = p(1)
                .BaudRate = 9600
                .Encoding = System.Text.Encoding.GetEncoding(28591)
                .DtrEnable = True
            End With
            nl = CByte(Asc(SerialPort1.NewLine))
            Try
                SerialPort1.Open()
                timer1.Interval = 50
                timer1.Start()
            Catch ex As Exception
                Debug.WriteLine(ex.Message)
            End Try
        End Sub
    
        Dim nl As Byte
        Dim dataByts As New List(Of Byte)
        Dim dataLock As New Object
        Dim setup As Boolean = False
        Dim datarcvd As New Threading.AutoResetEvent(False)
    
        Private Sub timer1_Tick(sender As Object, e As EventArgs) Handles timer1.Tick
            If datarcvd.WaitOne(0) Then 'do we have bytes to process
                If dataByts.Count > 0 Then
                    Dim s As String = ""
                    Threading.Monitor.Enter(dataLock) 'yes
                    Dim idxOfNL As Integer = dataByts.IndexOf(nl) 'does the list have a newline
                    If idxOfNL >= 0 Then
                        idxOfNL += 1 'include the newline
                        'get the string, including the newline character
                        s = SerialPort1.Encoding.GetChars(dataByts.ToArray, 0, idxOfNL)
                        dataByts.RemoveRange(0, idxOfNL) 'remove the bytes processed
                    End If
                    Threading.Monitor.Exit(dataLock)
                    RichTextBox1.AppendText(s)
                End If
            End If
        End Sub
    
        Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
            Try
    
                SerialPort1.WriteLine("s")
    
            Catch ex As TimeoutException
                MessageBox.Show(ex.Message)
    
            Catch ex As InvalidOperationException
                MessageBox.Show(ex.Message)
    
            Catch ex As UnauthorizedAccessException
                MessageBox.Show(ex.Message)
    
            End Try
        End Sub
    
        Private Sub SerialPort1_DataReceived(sender As Object, _
                                             e As IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
            Dim br As Integer = SerialPort1.BytesToRead '# of bytes to read
            If br > 0 Then
                Dim b(br - 1) As Byte 'create buffer to read into
                Try
                    br = SerialPort1.Read(b, 0, b.Length) 'read the bytes
                    If br < b.Length Then 'adjust length if required
                        Array.Resize(b, br)
                    End If
                    'add bytes just read to list
                    Threading.Monitor.Enter(dataLock)
                    dataByts.AddRange(b)
                    Threading.Monitor.Exit(dataLock)
                    datarcvd.Set() 'signal event fired
                Catch ex As Exception
                    Debug.WriteLine(ex.Message)
                End Try
            End If
        End Sub
    
        Private Sub SerialPort1_ErrorReceived(sender As Object, _
                                              e As IO.Ports.SerialErrorReceivedEventArgs) _
                                          Handles SerialPort1.ErrorReceived
            Debug.WriteLine(e.EventType)
        End Sub
    
        Private Sub SerialPort1_PinChanged(sender As Object, _
                                           e As IO.Ports.SerialPinChangedEventArgs) _
                                       Handles SerialPort1.PinChanged
            Debug.WriteLine(e.EventType)
        End Sub
    End Class
    Last edited by dbasnett; Jun 14th, 2013 at 10:20 AM.
    My First Computer -- Documentation Link (RT?M) -- Using the Debugger -- Prime Number Sieve
    Counting Bits -- Subnet Calculator -- UI Guidelines -- SerialPort Answer

    "Those who use Application.DoEvents have no idea what it does and those who know what it does never use it." John Wein
    "They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety." Benjamin Franklin
    "It is not all that I know that is the problem, it is all I think I do that is."

  9. #9

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    Re: SerialPort problems, readline() hangs when using win xp (fine on win 7)

    Hi

    Yes Hyperterminal works fine on xp.

    Thanks for the code I will check your timer based example sometime over the weekend as right now my heads kind of fried!! - thanks.

    Bally

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