Problem with COM1, errors....

Hello I'm having an issue with a serial connection program. It connects a motor controller to a computer via RS232.

Here is the code:

VB Code:

Public Class Form1
    Dim COM1 As IO.Ports.SerialPort = My.Computer.Ports.OpenSerialPort("COM1", 38400, IO.Ports.Parity.Odd, 7, IO.Ports.StopBits.One)
    Dim Ring_Vel As Integer = 1
 
    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        'First run setup
        COM1.WriteLine("1PW" & vbCr & vbCr)
        COM1.WriteLine("1RSF" & vbCr)
        COM1.WriteLine("1AC=100000" & vbCr)
        COM1.WriteLine("1VL=" & Ring_Vel & vbCr)
        VScrollBar1.Value = Ring_Vel
        Label3.Text = Ring_Vel
    End Sub
 
  
    Private Sub VScrollBar1_Scroll(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ScrollEventArgs) Handles VScrollBar1.Scroll
        'Speed Controller
        Ring_Vel = VScrollBar1.Value * 1000
        COM1.WriteLine("1VL=" & Ring_Vel & vbCr)
        If Button1.Enabled = False Then COM1.WriteLine("1RFN" & vbCr)
        Label3.Text = VScrollBar1.Value
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'Start Button
        Button1.Enabled = False
        Button2.Enabled = True
        COM1.WriteLine("1RFN" & vbCr)
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        'Stop Button
        Button1.Enabled = True
        Button2.Enabled = False
        COM1.WriteLine("1ST" & vbCr)
    End Sub
End Class

If I change the VScroll1 quickly and often I get this error:
The I/O operation has been aborted because of either a thread exit or an application request.


Why is it doing this? I tried to put the COM1.WriteLine on a timer (.5 sec) so it doesnt overload the buffers or something. And it will still do it.

I dont understand bc I have another program that has a loop, and every cycle of the loop it sends something to the unit. It was able to reach nearly 30 sends per second.

maybe the write buffer is to small

SerialPort1.WriteBufferSize=?????????

is the device you are talking to replying?

.WriteLine may raise an exception so it should be in a try catch block

Code:

---

    Dim anEx As New Exception
    'instead of
    'COM1.WriteLine("1AC=100000" & vbCr)
    'try this
    '
    'anEx = myComWriteLine("1AC=100000" & vbCr)
    '    If anEx Is Nothing Then
    ''io was ok
    '        Stop
    '    Else
    ''process exception
    '        Stop
    '    End If
    Private Function myComWriteLine(ByVal toBeWritten As String) As Exception
        Try
            COM1.WriteLine(toBeWritten)
        Catch ex As Exception
            Return ex
        End Try
        Return Nothing
    End Function

---

how do you prevent it from sending output more often then every .5 seconds? The scrolling event can be raised very quickly. I'm not sure if the WriteLine() method blocks or not but if it doesn't then you could be sending overlapping messages perhaps not waiting long enough for your device to respond....

the default for WriteTimeOut is -1 which blocks until the write is complete.

are you manually scrolling the scroll bar when the error occurs?