[RESOLVED] VB 2010 Express - Serial port threading problem?

Running on Win 7. The situation is: I have a hardware device sitting on a serial port and it accepts a set of string commands and returns a response string to each command. As a base, I used a set of code I found on the Web that uses a delegate and separate thread and it works just fine up to a point. The requirement is to be able to poll the device up to every 200 ms. with two commands and send other commands less frequently. The device runs at 57,600 bps.

I can send one of the commands every 200ms and receive the responses perfectly and that will run OK for many minutes. If I then add a second command to the sequence and read its response, responses to the first command are received OK for a short while but responses to the second command are never received. These commands are sent and responses read in a timer tick event. So, the sequence would be: send command 1, read response, send command 2, read response. The code includes the ability to send the commands individually under button control and both commands work just fine.

When running in the timer mode, the commands are being sent and responses to both commands are being received OK but the received data isn't there for the second command. I think the problem lies with possible misunderstanding of the delegate and threading on my part. Any suggestions greatly appreciated. Here's the code:

Code:

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Imports System
Imports System.ComponentModel
Imports System.Threading
Imports System.IO.Ports

Public Class frmMain
    Dim myPort As Array  'COM Ports detected on the system will be stored here
    Delegate Sub SetTextCallback(ByVal [text] As String) 'Added to prevent threading errors during receiving of data
    Dim interval As String

    ' The user can send a single ?AF or ?BF command with the SEND button.  Or, he can send the commands repeatedly
    ' by pressing the TIMED SEND button.  In that case, the tick event sends the ?AF, reads the response, and then
    ' sends the ?BF command and reads that response.  The responses to ?AF and ?BF should update the text boxes
    ' labeled VFO A and VFO B with the values returned.

    Private Sub frmMain_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

        'When our form loads, auto detect all serial ports in the system and populate the cmbPort Combo box.
        myPort = IO.Ports.SerialPort.GetPortNames() 'Get all com ports available

        For i = 0 To UBound(myPort)
            cmbPort.Items.Add(myPort(i))
        Next
        cmbPort.Text = cmbPort.Items.Item(0)    'Set cmbPort text to the first COM port detected

        btnDisconnect.Enabled = False          'Initially Disconnect Button is Disabled

    End Sub

    Private Sub btnConnect_Click(sender As System.Object, e As System.EventArgs) Handles btnConnect.Click

        SerialPort1.PortName = cmbPort.Text        'Set SerialPort1 to the selected COM port at startup
        SerialPort1.Open()

        btnConnect.Enabled = False          'Disable Connect button
        btnDisconnect.Enabled = True        'and Enable Disconnect button

    End Sub

    Private Sub btnDisconnect_Click(sender As System.Object, e As System.EventArgs) Handles btnDisconnect.Click

        SerialPort1.Close()            'Close our Serial Port
        btnConnect.Enabled = True
        btnDisconnect.Enabled = False
        Me.Close()

    End Sub

    Private Sub btnSend_Click(sender As System.Object, e As System.EventArgs) Handles btnSend.Click

        SerialPort1.Write(txtTransmit.Text & vbCr) 'The text contained in the txtText will be sent to the serial port as ascii
        'plus the carriage return (Enter Key)

    End Sub

    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

    Private Sub cmbPort_SelectedIndexChanged(sender As System.Object, e As System.EventArgs) Handles cmbPort.SelectedIndexChanged
        If SerialPort1.IsOpen = False Then
            SerialPort1.PortName = cmbPort.Text        'pop a message box to user if he is changing ports
        Else                                                                              'without disconnecting first.
            MsgBox("Valid only if port is Closed", vbCritical)
        End If
    End Sub

    Private Sub Timer1_Tick(sender As System.Object, e As System.EventArgs) Handles tmrTimer1.Tick

        Dim freq As String

        'Each time tick occurs, we send a request to the Orion
        SerialPort1.Write("?AF" & vbCr) 'Requests current value of VFO-A along with carriage return

        'Response to the ?AF is a string like "@AF14236789 which will be displayed as: "14.236.789"
        If Me.rtbReceived.Text.StartsWith("@AF") Then
            freq = Mid(rtbReceived.Text, 4, 2) & "." & Mid(rtbReceived.Text, 6, 3) & "." & Mid(rtbReceived.Text, 9, 3)
            freq = freq.TrimStart("0")
            If freq.Length = 9 Then
                txtVFOA.Text = "  " & freq
            Else
                txtVFOA.Text = freq
            End If
            rtbReceived.Text = ""
        End If

        SerialPort1.Write("?BF" & vbCr) 'Requests current value of VFO-B along with carriage return

        'Response to the ?BF is a string like "@BF14236789 which will be displayed as: "14.236.789"
        If Me.rtbReceived.Text.StartsWith("@BF") Then
            freq = Mid(rtbReceived.Text, 4, 2) & "." & Mid(rtbReceived.Text, 6, 3) & "." & Mid(rtbReceived.Text, 9, 3)
            freq = freq.TrimStart("0")
            If freq.Length = 9 Then
                txtVFOB.Text = "  " & freq
            Else
                txtVFOB.Text = freq
            End If
            rtbReceived.Text = ""
        End If


    End Sub


    Private Sub btnTimerOn_Click(sender As System.Object, e As System.EventArgs) Handles btnTimerOn.Click

        tmrTimer1.Enabled = True
        tmrTimer1.Interval = CInt(cmbTimerInterval.Text)

    End Sub

    Private Sub btnStopTimedSend_Click(sender As System.Object, e As System.EventArgs) Handles btnStopTimedSend.Click

        tmrTimer1.Enabled = False

    End Sub

End Class

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Well, I'm unfortunately busy today so can't fully test or respond to posts as I would like, but an issue that most of these serial port questions have in common is that the user is not treating the serial data as a stream.
When you do ReadExisting, you will read however many bytes (or characters) have been received so far, which may very well be less than you are expecting. so if you're expecting 11 characters, and you've only received the first 3 to 10 characters at the time you read, you need to wait until the next read to receive the rest of the characters so you have a full response.
I mentioned, 3 as the lower value because if it was less than 3, you woundn't match so may end up loosing that response, but hopefully sync up again later. If if was 3 or more, you would probably match your "header", and then try to parse the "fields", without having them all, so would have other issues.

That is about all I can say for now, my free time is lacking.
Once possible, not robust "fix", might be to change the logic so that your timer runs at 100ms, and issues a command on one tick, then looks for the response in the next tick. That 100ms delay might allow for the response to be fully receieved before you try to look at it.

As we do not have the same equipment as you do and it is impossible to test it. I would just recommend a few things. On the Timer1_Tick sub, you write to the serial port and then check the value of rtbReceived. Instead you should wait until there is something there before checking (put a time limit for that) and then do the same after the other write to the port.

Your delegation is very out dated. Take a look at JMC article here http://www.vbforums.com/showthread.p...Worker-Threads

Here is a pattern to deal with data reception. Notice how little the DataReceived event handler does. The work of decoding the protocol is moved to another thread. You should be able to accomplish what you want in 'ProcessProto'

Code:

---

    Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles Me.Shown
        pthrd = New Threading.Thread(AddressOf ProcessProto)
        pthrd.IsBackground = True
        pthrd.Start()
    End Sub

    Dim pthrd As Threading.Thread

    Dim buf As New System.Text.StringBuilder
    Dim bufLock As New Object

    Dim chkBuf As New Threading.AutoResetEvent(False)

    Private Sub ProcessProto()
        Do
            'process received message
            'make certain to remove messages from the buffer
            'and when doing so lock it
            If buf.Length > 0 Then

            End If
            chkBuf.WaitOne(5000)
        Loop
    End Sub

    Private Sub SerialPort1_DataReceived(sender As Object, _
                                        e As IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        If SerialPort1.BytesToRead > 0 Then
            Threading.Monitor.Enter(bufLock) 'lock the buffer while changing
            buf.Append(SerialPort1.ReadExisting)
            Threading.Monitor.Exit(bufLock) 'inlock the buffer
            chkBuf.Set()
        End If
    End Sub

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Quote:

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Originally Posted by kaliman79912

As we do not have the same equipment as you do and it is impossible to test it. I would just recommend a few things. On the Timer1_Tick sub, you write to the serial port and then check the value of rtbReceived. Instead you should wait until there is something there before checking (put a time limit for that) and then do the same after the other write to the port.

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I'm doing it that way because the documentation and explanations I've read so far leave many things hanging. For example, I would think that if I used the Readline method that it would not complete until the entire string ending with CR is in the buffer. In fact, I've never gotten a Readline to complete ever, even though the data has clearly been sent. Another thing very unclear is just when and how often is the DataReceived event triggered. Does that happen when the first character is received? Does it happen again for every character (realizing that maybe two or more characters may have arrived in the meantime). If the goal is to receive the character string of known length, do I have to count the bytes until I know they're all here or is there a method that will pass me just the completed string (like I thought Readline was supposed to do).

Quote:

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Originally Posted by dbasnett

Here is a pattern to deal with data reception. Notice how little the DataReceived event handler does. The work of decoding the protocol is moved to another thread. You should be able to accomplish what you want in 'ProcessProto'

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I still have some basic gaps in my understanding of just what VB is doing in some cases. For example, how often does the DataReceived event handler get triggered when receiving a 12 byte string at 56.7 Kbps? If VB knows what the BytesToRead value is when the handler is entered, doesn't that mean that the entire string has been received already?

Quote:

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Originally Posted by ident

Your delegation is very out dated. Take a look at JMC article here http://www.vbforums.com/showthread.p...Worker-Threads

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The example you pointed to had a date of 2007. The one I used was dated 2010 and written specifically for VB 2010 - so not sure how I can tell when something is outdated or not.

Quote:

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Originally Posted by passel

When you do ReadExisting, you will read however many bytes (or characters) have been received so far, which may very well be less than you are expecting.

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OK - I understand that. I used the ReadExisting approach because that's what was in the working example. Is there an existing method that would handle the waiting for me until the end of the message is received (in this case, every message either way ends with CR). The purpose of this exercise is to allow programs running through two other serial ports to share information obtained from this device on this serial port. The VB program would constantly poll the device and store the info in variables and would then forward that to the other two ports if and when requested. All of these links are running at 57.6 kbps and if I have to introduce delays on all three, I'm concerned about the ability to sustain the desired rate of data flow.

Here's more information on my situation and what I think may be happening. I removed the statements in the Tick routine that set rtbReceived.Text to "". As a result, I can now see every response from the device and every expected response string is there and complete. I can set a much longer timer interval and see that every response is received.
The code in the timer tick event sets the formatted received response into a text box (two - one for each of the two types of command responses). The text for VFOA is always displayed in its text box and in timely fashion. The text for VFOB is NEVER displayed in its text box. Based on the little I know about thread interaction, it seems its not possible to set a variable in one thread from another thread. So, I'm assuming that (for reasons I don't understand) that may be the cause of the problem. Is there some way that I can obtain the thread ID or whatever its called so I can log it and see?

Quote:

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Originally Posted by Solo44

I still have some basic gaps in my understanding of just what VB is doing in some cases. For example, how often does the DataReceived event handler get triggered when receiving a 12 byte string at 56.7 Kbps? If VB knows what the BytesToRead value is when the handler is entered, doesn't that mean that the entire string has been received already?

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My advice is to read what is there when it is there and to worry about the protocol elsewhere. There are several layers of software at play here, and trying to do too much in the handler is problematic.

It looks like the protocol is an @followed by two known characters, some variable amount of characters, and then a CR.

Running several ports at 57.6 Kbps, 7,200 bytes per second, is not an issue unless you cause one. Normally the problem is stalling the handler while trying to update the UI, which is why I take the approach I presented.

edit:
What the code to process received data might look like

Code:

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    Private Sub ProcessProto() 'from post #5
        Dim rcvdMessage As New System.Text.StringBuilder
        Dim messCmplt As Boolean = False
        Do
            'process received message
            'make certain to remove messages from the buffer
            'and when doing so lock it
            Do While buf.Length > 0
                Threading.Monitor.Enter(bufLock)
                Dim rcvdCH As String = buf(0)
                buf.Remove(0, 1)
                Threading.Monitor.Exit(bufLock)
                If rcvdCH = "@" AndAlso rcvdMessage.Length = 0 Then
                    rcvdMessage.Append(rcvdCH)
                ElseIf rcvdCH = "@" Then
                    'error?
                ElseIf rcvdCH = ControlChars.Cr Then
                    messCmplt = True
                    Exit Do
                Else
                    rcvdMessage.Append(rcvdCH)
                End If
            Loop
            If messCmplt Then
                'a complete message
                Dim theMessage As String = rcvdMessage.ToString
                'reset for next message
                messCmplt = False
                rcvdMessage.Length = 0
                'process message just rcvd
                Me.Invoke(Sub()
                              Label1.Text = theMessage
                          End Sub)
            End If
            chkBuf.WaitOne(5000) 'wait for more data
        Loop
    End Sub

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Quote:

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Originally Posted by dbasnett

My advice is to read what is there when it is there and to worry about the protocol elsewhere. There are several layers of software at play here, and trying to do too much in the handler is problematic.

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Well, I implemented your approach and now have the basic code working. I have a better understanding of how the threads function now. I didn't realize that I could define a new thread to run continuously in the background and that was the part that was missing. The VB course book I used never mentioned things like StringBuilder, locking and in fact didn't even mention threads at all. Not new concepts to me, but had no idea they existed or how to implement them in VB.

Your code example was very clear and understandable, after reading about several of the things new to me. The one fault I've found with all the documentation I've seen on VB (VB help, books and forum responses) is the tendency of people answering questions or explaining things to jump directly to long and complex code examples without adequately explaining the concepts. The entire threading subject could be easily explained with a couple of nice diagrams that included notes on how threads can trigger or respond to events in other threads, how threads are initiated and terminated, etc. Anyway, thanks for the advice and I'll probably be back this way if I get into a jam again.

There are some threading threads :) in the forum. Don't know if they are any good or not.

There is no need to write a custom delegate. Use MethodInvoker or Action(of,

vb Code:

Public Class Form1
 
    Private Sub ReceivedText(ByVal text As String)
        Me.BeginInvoke(Sub() Me.TextBox1.Text = text)
    End Sub
 
End Class

Normally (I'd like to say always) the code I use looks like this, in which I read bytes and only convert to strings if required. The form has one label, two comboboxes, and one button.

Code:

---

Imports System.IO.Ports

Public Class Form1
    Dim WithEvents sp As New SerialPort
    Dim isRun As New Threading.ManualResetEvent(False)

    Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
        Try
            isRun.Reset() 'closing
            'wake the threads
            rcvd.Set()
            procproto.Set()
            'wait on them
            rcvdThrd.Join()
            procprotoThrd.Join()
            If sp.IsOpen Then sp.Close()
        Catch ex As Exception

        End Try
    End Sub

    Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles Me.Shown
        'add port names to combobox
        cboxPN.Items.AddRange(SerialPort.GetPortNames)
        'and speeds
        cboxSPD.Items.AddRange([Enum].GetNames(GetType(PortSpeeds)))
        'other setting could be done...

        'this thread reads bytes and adds them to the buffer
        rcvdThrd = New Threading.Thread(AddressOf Receive)
        rcvdThrd.IsBackground = True

        'this thread examines the buffer to see if a
        'complete message, as defined by the protocol, is available
        procprotoThrd = New Threading.Thread(AddressOf Protocol)
        procprotoThrd.IsBackground = True

        isRun.Set() 'we are running
        procprotoThrd.Start()
        rcvdThrd.Start()
    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        'open
        If Not sp.IsOpen AndAlso cboxPN.SelectedIndex >= 0 AndAlso cboxSPD.SelectedIndex >= 0 Then
            'port name and speed selected
            With sp
                .PortName = cboxPN.SelectedItem.ToString
                .BaudRate = CInt([Enum].Parse(GetType(PortSpeeds), cboxSPD.SelectedItem.ToString))
                'other settings
                .DataBits = 8
                .Parity = Parity.None
                .StopBits = StopBits.One
                'if using strings this encoding decodes all 8 bit values
                .Encoding = System.Text.Encoding.GetEncoding(28591)
            End With
            Try
                sp.Open()
                sp.DtrEnable = True 'turn DTR on
                Debug.WriteLine("is open")
                sp.WriteLine("This is a test")
            Catch ex As Exception
                'open failed code here
                Debug.WriteLine(ex.Message)
            End Try
        End If
    End Sub

    Private Sub sp_DataReceived(sender As Object, _
                                e As SerialDataReceivedEventArgs) _
                            Handles sp.DataReceived
        rcvd.Set() 'read the bytes
    End Sub

    Dim rcvd As New Threading.AutoResetEvent(False)
    Dim rcvdThrd As Threading.Thread
    Private Sub Receive()
        Do
            If sp.IsOpen Then 'is port open
                Dim numb As Integer = sp.BytesToRead 'number of bytes to read
                If numb > 0 Then
                    Dim temp(numb - 1) As Byte 'create a temporary buffer
                    Try
                        numb = sp.Read(temp, 0, numb) 'read the bytes
                        If numb <> temp.Length Then
                            Array.Resize(temp, numb)
                        End If
                        'add temp buffer to public buffer
                        Threading.Monitor.Enter(bufLock)
                        buf.AddRange(temp)
                        Threading.Monitor.Exit(bufLock)
                        procproto.Set() 'check for possible message
                    Catch ex As Exception
                        'fix error handler
                    End Try
                End If
            End If
            rcvd.WaitOne() 'wait for event handler to fire
        Loop While isRun.WaitOne(0)
    End Sub

    Dim buf As New List(Of Byte)
    Dim bufLock As New Object

    Dim procproto As New Threading.AutoResetEvent(False)
    Dim procprotoThrd As Threading.Thread
    'in this example the protocol is
    'some number of chars followed by 'eol'
    Private Sub Protocol()
        Const eol As Byte = 10 'EOL = LF
        Do
            If buf.Count > 0 Then 'some data present
                'is it a complete message as defined by our protocol?
                Dim idx As Integer
                Do
                    idx = buf.IndexOf(eol)
                    If idx >= 0 Then 'do I have a EOL?
                        'yes, extract message
                        Dim mess As New System.Text.StringBuilder
                        'get message without EOL and
                        'get rid of processed data in buffer
                        Threading.Monitor.Enter(bufLock)
                        mess.Append(sp.Encoding.GetChars(buf.ToArray, 0, idx))
                        buf.RemoveRange(0, idx + 1)
                        Threading.Monitor.Exit(bufLock)
                        '
                        'process the message, in this case...
                        'show message to user

                        Me.BeginInvoke(Sub()
                                          Label1.Text = mess.ToString
                                          Label1.Refresh()
                                      End Sub)
                    End If
                Loop While idx >= 0
            End If
            procproto.WaitOne() 'wait for signal to proccess next potential message
        Loop While isRun.WaitOne(0)
    End Sub

    Private Sub sp_ErrorReceived(sender As Object, _
                                e As SerialErrorReceivedEventArgs) Handles sp.ErrorReceived
        Debug.WriteLine(e.EventType.ToString)
    End Sub

    Private Sub sp_PinChanged(sender As Object, _
                              e As SerialPinChangedEventArgs) Handles sp.PinChanged
        Debug.WriteLine(e.EventType.ToString)
    End Sub
End Class

''' <summary>
''' enumerates 'standard' port speeds
''' </summary>
''' <remarks>derived from many sources</remarks>
Public Enum PortSpeeds
    b110 = 110
    b300 = 300
    b600 = 600
    b1200 = 1200
    b2400 = 2400
    b4800 = 4800
    b9600 = 9600
    b14400 = 14400
    b19200 = 19200
    b28800 = 28800
    b38400 = 38400
    b56000 = 56000
    b57600 = 57600
    b115200 = 115200
    b128000 = 128000
    b153600 = 153600
    b230400 = 230400
    b256000 = 256000
    b460800 = 460800
    b921600 = 921600
End Enum

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What changes is what is inside of Protocol. The threading shown here is about as simple as four threads can interact with each other.

Quote:

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Originally Posted by dbasnett

Normally (I'd like to say always) the code I use looks like this, in which I read bytes and only convert to strings if required.
What changes is what is inside of Protocol. The threading shown here is about as simple as four threads can interact with each other.

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That's great and very timely. I've determined that my current approach doesn't work very well with a high rate of polling the device. Right now, I'm blasting 12 writes out of the timer tick routine with no delays between and then handling the responses as a stream. What I really want to do is to send the commands one at a time and process the response and not send another command until the previous response is received (no need to wait for the processing of the response to be complete). The device has no way to notify my end that commands are being received faster than they can be processed. I understand the threading mechanism now pretty well, but need to dig into the signaling so I can wake up one thread when something occurs in another. Thanks for your help on this.

Well, I'm getting very close with this. The program is now working with three serial ports and 7 threads in all with a very high message rate and all works well, except.... Every now and then, I get an error on the statement marked "ERROR HERE" in this code segment:

Code:

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'some number of chars followed by a LF
    Private Sub Protocol()
        Const eol As Byte = 10 'LF
        Do
            If buf.Count > 0 Then 'some data present
                'is it a complete message as defined by our protocol?
                Dim idx As Integer
                Do
                    idx = buf.IndexOf(eol)
                    If idx >= 0 Then 'do I have a LF?
                        'yes, extract message
                        Dim mess As New System.Text.StringBuilder
                        'get message without LF
                        mess.Append(sp.Encoding.GetChars(buf.ToArray, 0, idx))  [ERROR HERE]
                        '
                        'process the message, in this case...
                        'show message to user
                        Me.BeginInvoke(Sub()
                                          Label1.Text = mess.ToString
                                      End Sub)
                        'get rid of processed data in buffer
                        Threading.Monitor.Enter(bufLock)
                        buf.RemoveRange(0, idx + 1)
                        Threading.Monitor.Exit(bufLock)
                    End If
                Loop While idx >= 0
            End If
            procproto.WaitOne() 'wait for signal to proccess next potential message

---

I've tried just using your original code and I have the same problem. I'm afraid I just don't know enough about VB yet to understand what's going on. Here's an image showing the error:

Attachment 113323

There's probably a very simple solution?

What was the value of idx when you got the error?
You're checking for greater than or equal to 0, but if it was 0 would a string with only a linefeed in it convert correctly?
Perhaps you want > 0, not >= 0.

Quote:

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Originally Posted by passel

What was the value of idx when you got the error?
You're checking for greater than or equal to 0, but if it was 0 would a string with only a linefeed in it convert correctly?
Perhaps you want > 0, not >= 0.

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An index of 0 is fine. Make this change to the inner most Do and try it.

Code:

---

                    idx = buf.IndexOf(eol)
                    If idx >= 0 Then 'do I have a LF?
                        'yes, extract message
                        Dim mess As New System.Text.StringBuilder
                        'get message without LF and
                        'get rid of processed data in buffer
                        Threading.Monitor.Enter(bufLock)
                        mess.Append(sp.Encoding.GetChars(buf.ToArray, 0, idx))
                        buf.RemoveRange(0, idx + 1)
                        Threading.Monitor.Exit(bufLock)
                        '
                        'process the message, in this case...
                        'show message to user

                        Me.BeginInvoke(Sub()
                                          Label1.Text = mess.ToString
                                          Label1.Refresh()
                                      End Sub)
                    End If

---

If you aren't sure where it goes let me know. When I looked at what I posted it seemed clear that I had made a mistake. The list of bytes (buf) was being manipulated outside of the lock.

Quote:

---

Originally Posted by dbasnett

An index of 0 is fine. Make this change to the inner most Do and try it.

Code:

---

                    idx = buf.IndexOf(eol)
                    If idx >= 0 Then 'do I have a LF?
                        'yes, extract message
                        Dim mess As New System.Text.StringBuilder
                        'get message without LF and
                        'get rid of processed data in buffer
                        Threading.Monitor.Enter(bufLock)
                        mess.Append(sp.Encoding.GetChars(buf.ToArray, 0, idx))
                        buf.RemoveRange(0, idx + 1)
                        Threading.Monitor.Exit(bufLock)
                        '
                        'process the message, in this case...
                        'show message to user

                        Me.BeginInvoke(Sub()
                                          Label1.Text = mess.ToString
                                          Label1.Refresh()
                                      End Sub)
                    End If

---

If you aren't sure where it goes let me know. When I looked at what I posted it seemed clear that I had made a mistake. The list of bytes (buf) was being manipulated outside of the lock.

---

OK - I understand manipulating buf outside the lock. But when I put my message processing where your comments say to put it, nothing gets processed ever. For one thing, I have no idea what this statement is trying to do:

mess.Append(sp.Encoding.GetChars(buf.ToArray, 0, idx))

Assuming that the intent of it is that the message to be processed is in buf, I don't see how that can be as the statement " buf.RemoveRange(0, idx + 1)" seems to have just removed that message before we got to the processing. Some other puzzles to me: Why did we define buf as a byte list to begin with? Everything in this application is pure character - there's no data that isn't character. And, I don't understand why we're working with an array at this moment.

I was blindly using your code without understand those items from the beginning, but since it was working (sort of), I elected not to question those things in the beginning. Thanks for spending the time on this and I think I'm just a small step away from everything being right.

The code was giving you an error on a certain line. Because of the location of the line we know there is a LF. You saying that nothing gets processed doesn't make sense. It may be that all there is are LF's in the buffer, but they are getting processed. Put a breakpoint on the Threading.Monitor.Enter line and step through the code, looking at the buffer as you go. You may have to post your actual code.

The line in question converts the bytes to chars and adds them to the string builder. Why? Because this code comes from a Class that I have that handles a variety of SerialPort input. The bytes are added to the stringbuilder, then deleted from the buffer.

Quote:

---

Originally Posted by dbasnett

The code was giving you an error on a certain line. Because of the location of the line we know there is a LF. You saying that nothing gets processed doesn't make sense.

---

OK - now all is well. I posted the code below just so you could see where I picked off the message for processing. It ran for over an hour with no problem and previously would fail in 1-5 minutes. I happened to mouse on the link in your signature line, the entry about your first computer. You must be almost as old as I am! On my first assignment, that was the new machine on the raised floor.

Code:

---

  Do

            If SP2buf.Count > 0 Then  'we have a message to process
                Dim idx As Integer
                Do
                    idx = SP2buf.IndexOf(13)
                    If idx > 0 Then  'Is the CR there?
                        Dim mess As New System.Text.StringBuilder
                        Threading.Monitor.Enter(SP2buflock)
                        mess.Append(SP2.Encoding.GetChars(SP2buf.ToArray, 0, idx))      'get the message without the vbcr
                        Threading.Monitor.Exit(SP2buflock)
                        SP2Request = mess.ToString
                        Threading.Monitor.Enter(SP2buflock)
                        SP2buf.RemoveRange(0, idx + 1)      'get rid of the processed data in the buffer
                        Threading.Monitor.Exit(SP2buflock)
                        If Microsoft.VisualBasic.Left(SP2Request, 1) = "*" Then
                            If rbSP2TraceOn.Checked = True Then
                                'Write the message to the trace box
                                Me.Invoke(Sub()
                                              Threading.Monitor.Enter(SP2buflock)
                                              rtbSP2Traffic.Text &= SP2Request & vbCr
                                              Threading.Monitor.Exit(SP2buflock)
                                          End Sub)

                                'Now process the message
                                Select Case Mid(SP2Request, 1, 3)

                                    Case "*AF"
                                        freq = Mid(SP2Request, 4, 2) & "." & Mid(SP2Request, 7, 3) & "." & Mid(SP2Request, 10, 3)
                                        freq = freq.TrimStart("0")  'kill the leading zero
                                        If freq.Length = 9 Then  'Indicates a single digit MHz and need padding to maintain display position
                                            Me.Invoke(Sub()
                                                          txtVFOA.Text = "  " & freq
                                                      End Sub)
                                        Else
                                            Me.Invoke(Sub()
                                                          txtVFOA.Text = freq
                                                      End Sub)
                                        End If

                                    Case "*BF"
                                        freq = Mid(SP2Request, 4, 2) & "." & Mid(SP2Request, 7, 3) & "." & Mid(SP2Request, 10, 3)
                                        freq = freq.TrimStart("0")  'kill the leading zero
                                        If freq.Length = 9 Then  'Indicates a single digit MHz and need padding to maintain display position
                                            Me.Invoke(Sub()
                                                          txtVFOB.Text = "  " & freq
                                                      End Sub)
                                        Else
                                            Me.Invoke(Sub()
                                                          txtVFOB.Text = freq
                                                      End Sub)
                                        End If
                                End Select
                            End If

                            Select Case Mid(SP2Request, 1, 4)

                                Case "*RMF"
                                    Me.Invoke(Sub()
                                                  txbMainFilter.Text = Mid(SP2Request, 5, SP2Request.Length - 4)
                                              End Sub)

                            End Select

                            SP1.Write(SP2Request & vbCr)    'Send the command to the Orion immediately
                            If rbOrionTraceOn.Checked = True Then

                                'Write the command to the Orion trace box
                                Me.Invoke(Sub()
                                              rtbOrionTraffic.Text &= SP2Request & vbCr
                                          End Sub)
                            End If

                        End If

                        'Log to SP2 trace

                        If rbSP2TraceOn.Checked = True Then
                            Me.Invoke(Sub()
                                          Threading.Monitor.Enter(SP2buflock)
                                          rtbSP2Traffic.Text &= SP2Request & vbCr  'Log to SP2 trace
                                          Threading.Monitor.Exit(SP2buflock)
                                      End Sub)
                        End If
                    End If
                Loop While idx >= 0
            End If

            SP2respReceived.WaitOne()      'Wait for signal to process next message

        Loop While isRun.WaitOne(0)

---

Glad it works. I did notice a few things. The only time it is required to lock the buffer is if you are manipulating it. When you lock it the other thread could be blocked. Once the string is in SP2Request I don't see the need to lock the buffer, so remove the locking in the Invokes. Also,

Code:

---

                        'replace this
                        Dim mess As New System.Text.StringBuilder
                        Threading.Monitor.Enter(SP2buflock)
                        mess.Append(SP2.Encoding.GetChars(SP2buf.ToArray, 0, idx))      'get the message without the vbcr
                        Threading.Monitor.Exit(SP2buflock)
                        SP2Request = mess.ToString
                        Threading.Monitor.Enter(SP2buflock)
                        SP2buf.RemoveRange(0, idx + 1)      'get rid of the processed data in the buffer
                        Threading.Monitor.Exit(SP2buflock)

                        'with this
                        Threading.Monitor.Enter(SP2buflock)
                        SP2Request = SP2.Encoding.GetChars(SP2buf.ToArray, 0, idx)    'get the message without the vbcr
                        SP2buf.RemoveRange(0, idx + 1)      'get rid of the processed data in the buffer
                        Threading.Monitor.Exit(SP2buflock)

---

I will be 60 in July.

Will make that change, thanks. I'm going to mark this one resolved. Well, you're still a youngster. I turned 70 last month. Almost all of my development work in the past has been in assembler, so the object stuff is new to me. Never worked on the 1620, but the install in my customer location was in the spring of 1966.

Quote:

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Originally Posted by Solo44

Will make that change, thanks. I'm going to mark this one resolved. Well, you're still a youngster. I turned 70 last month. Almost all of my development work in the past has been in assembler, so the object stuff is new to me. Never worked on the 1620, but the install in my customer location was in the spring of 1966.

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I wrote a lot of assembler on the 1620. It was an odd machine. It didn't have fixed length words, was BCD based, and did addition with a look up table.

Glad you resolved your issue.