vb6 multithread runs 21 times then stops and errors

[martin_green]

Hi,
I have a project that has to read the usb port all the time and look at the data to parse it out and put some strings in a file.
The following code will read the usb port and put the data into a circular buffer so that the top level application can read the data and then process it.
This code seems to run 21 times before it just exits.
I do not know what would cause such behavior,
Can anyone offer any suggestions?
Thanks,
Martin

Public Sub WaitForUsbRet()
Dim EventObject As Long
Dim Result As Long
Dim res2 As Integer
Dim Security As SECURITY_ATTRIBUTES
Dim RecBuffer(65) As Byte
Dim rdNum As Long
Dim i As Integer
Dim res3 As Long
res2 = 1

    Security.lpSecurityDescriptor = 0
    Security.bInheritHandle = CInt(True)
    Security.nLength = Len(Security)
        
    EventObject = CreateEvent(Security, CInt(True), CInt(False), "rdUsb")
    HIDOverlapped.Offset = 0
    HIDOverlapped.OffsetHigh = 0
    HIDOverlapped.hEvent = EventObject

    Do
        Form1.ShpStatus.BackColor = Form1.ShpStatus.BackColor + 1
        DoEvents
        RecBuffer(4) = 0
        RecBuffer(5) = 0
        Result = ReadFile _
        (HIDHandle, _
        RecBuffer(0), _
        CLng(Capabilities.InputReportByteLength), _
        rdNum, _
        HIDOverlapped)

        Form1.lstBoxRec.AddItem "Res=" & Result & " rdnum=" & rdNum & " hid=" & HIDOverlapped.Internal

        Result = WaitForSingleObject(EventObject, 500)
        
        Form1.lstBoxRec.AddItem "Res2=" & Result & " err=" & GetLastError & " hid=" & HIDOverlapped.Internal

        Select Case Result
            Case WAIT_TIMEOUT
            ' Timeout error.
                Form1.lstBoxRec.AddItem "Out"
                CancelIo (ReadHandle)
                Form1.devStatus = RET_USBDEVREVTOOLOW
                DoEvents
            Case WAIT_FAILED Or WAIT_ABANDONED
                Form1.lstBoxRec.AddItem "FAIL"
                DoEvents
            Case WAIT_OBJECT_0
    '        ' Success
    '        ' Use the report data.
                rdNum = (RecBuffer(4) + 5)
                If rdNum > 65 Then rdNum = 65
               If (rdNum > 5) Then
                    For i = 1 To rdNum
                       Form1.putInCircBuff (RecBuffer(i))
                    Next i
                End If
                Form1.lstBoxRec.ListIndex = Form1.lstBoxRec.ListCount - 1
                If (rdNum > 0) Then Form1.tmrCommHndl.Enabled = True
                DoEvents
            Case Else
                Form1.lstBoxRec.AddItem "Else"
                CancelIo (ReadHandle)
                Form1.devStatus = RET_USBDEVREVTOOLOW
        End Select
        res3 = ResetEvent(EventObject)
    Loop Until res2 = 0
End Sub