VB6 to VB.NET conversion issues, .dll function returns an error

[Naveen Bibinaga]

I recently converted a VB6 program to VB.NET. This program is used to communicate with the Superlogics PCM Series DAQ card that the company no more produces and has no support for VB.NET. My program was running fine in VB6 but has problems in VB.net due to the the functions in the external .dll file (I am not sure)

I read many forums and did some changes with respect to the marshaling attributes. So guys please give me your ideas to solving this -

Error

'I am getting an error with intStatus = 350
referring to "Invalid Request Handle", please refer Line 73 in the program

'The superlogics manual asks me to check the PCMDigitalInputVB function and nothing more

Please guide me to the cause, Thanks in advance

 
Public Function singleDigitalInput(ByVal LogicalDevice As Short, ByVal Channel As Short, ByRef InputValue As Byte) As Long
 
        Dim intStatus As Short
        Dim intRequestHandle As Short
        Dim udtDigioRequest As New DigioRequest
        udtDigioRequest.Initialize()
        Dim udtDataBuffer As New PCMDriveBuffer
        Dim udtAllocateRequest As New allocate_request
 
        Dim lngRetChannelAdd As Integer
        Dim lngRetBufferAdd As Integer
 
        Dim blnCompleteStatus As Boolean
        Dim lngEventMask As Integer
        Dim ErrorCode As Short
 
        On Error GoTo errUnknown
 
 
 
        intRequestHandle = 0
        blnCompleteStatus = False
 
        '-------------------------------------------------------------------
        'Allocate and lock memory for the Digital Input
        '-------------------------------------------------------------------
 
        With udtAllocateRequest
            .request_type = DIGIN_TYPE_REQUEST
            .channel_array_length = 1
            .number_of_buffers = 1
            .buffer_size = 1
            .buffer_attributes = RING_BUFFER
        End With
 
        intStatus = PCMAllocateRequestVB(LogicalDevice, udtAllocateRequest)
 
        If intStatus <> 0 Then
            singleDigitalInput = intStatus
            Exit Function
        End If
 
        'Debug.Print "Allocate Request Status = " & intStatus
 
        '-------------------------------------------------------------------
        'Prepare the Digital Input Request Structure
        '-------------------------------------------------------------------
 
        lngRetChannelAdd = PCMGetAddressOfVB(Channel)
        'UPGRADE_WARNING: Couldn't resolve default property of object udtDataBuffer. Click for more: 'ms-help://MS.VSCC.v90/dv_commoner/local/redirect.htm?keyword="6A50421D-15FE-4896-8A1B-2EC21E9037B2"'
        lngRetBufferAdd = PCMGetAddressOfVB(udtDataBuffer)
 
        With udtDigioRequest
            .ChannelArrayPtr = lngRetChannelAdd
            .ArrayLength = 1
            .DigioBufferptr = lngRetBufferAdd
            .NumberOfScans = 1
            .IOMode = ForegroundCPU
            .TriggerSource = InternalTrigger
            .ScanEventLevel = 0
            .RequestStatus = NoEvents
        End With
 
        '-------------------------------------------------------------------
        'Send a digital input request to the PCMDrive
 
 'I am getting an error saying that "Invalid Request Handle" with intStatus = 350
 
'The superlogics manual asks me to check the PCMDigitalInputVB function and nothing more
        '-------------------------------------------------------------------
 
        intStatus = PCMDigitalInputVB(LogicalDevice, udtDigioRequest, intRequestHandle)
 
 
End Function
 
 
 
'-------------------------------------------------------------------
        Function declaration
        '-------------------------------------------------------------------
 
 
 
    Declare Function PCMDigitalInputVB Lib "PCMDrvVB.DLL" (ByVal logical_device As Short, ByRef Request As DigioRequest, ByRef handle As Short) As Short
 
 
'-------------------------------------------------------------------
        Structure declaration
        '-------------------------------------------------------------------
 <StructLayout(LayoutKind.Sequential, Pack:=1)> Structure DigioRequest
        Dim ChannelArrayPtr As Integer ' address of channel scan list
        <MarshalAs(UnmanagedType.ByValArray, SizeConst:=3)> Dim ReservedArray0 As Short() ' reserved for future expansion
        Dim ArrayLength As Short ' length of chan & gain arrays
        Dim DigioBufferptr As Integer ' address of PCMDRIVE_buffer
        <MarshalAs(UnmanagedType.ByValArray, SizeConst:=3)> Dim ReservedArray1 As Short() ' reserved for future expansion
        Dim TriggerSource As Short ' trigger source
        Dim TriggerMode As Short ' continuous / one-shot trigger
        Dim TriggerSlope As Short ' rising / falling edge trigger
        Dim TriggerChannel As Short ' trigger channel number
        '   (analog or digital trigger)
        Dim TriggerVoltage As Double ' trigger voltage (analog trigger)
        Dim TriggerValue As Integer ' value for trigger (digital trigger)
        <MarshalAs(UnmanagedType.ByValArray, SizeConst:=3)> Dim ReservedArray2 As Short() ' reserved for future expansion
        Dim IOMode As Short ' input mode
        '    = 0 poll
        '    = 1 IRQ
        '    = 2 DMA with CPU status
        '    = 3 DMA with IRQ status
        Dim ClockSource As Short ' clock source (0 = internal)
        Dim ClockRate As Double ' clock rate (if not internal)
        Dim SampleRate As Double ' input sampling rate (Hz)
        <MarshalAs(UnmanagedType.ByValArray, SizeConst:=3)> Dim ReservedArray3 As Short() ' reserved for future expansion
        Dim NumberOfScans As Integer ' number of channel scans
        Dim ScanEventLevel As Integer ' generate event each scan_event_level
        '    scans ( 0 = disable )
        <MarshalAs(UnmanagedType.ByValArray, SizeConst:=7)> Dim ReservedArray4 As Short() ' reserved for future expansion
        Dim TimeoutInterval As Short ' timeout interval (in sec)
        Dim RequestStatus As Integer ' request event status
 
        'UPGRADE_TODO: "Initialize" must be called to initialize instances of this structure. Click for more: 'ms-help://MS.VSCC.v90/dv_commoner/local/redirect.htm?keyword="B4BFF9E0-8631-45CF-910E-62AB3970F27B"'
        Public Sub Initialize()
            ReDim ReservedArray0(3)
            ReDim ReservedArray1(3)
            ReDim ReservedArray2(3)
            ReDim ReservedArray3(3)
            ReDim ReservedArray4(7)
        End Sub
End Structure
 
 
 

[!NoItAll]

Just guessing here but you might try changing InRequestHandle from SHORT to either Integer or IntPtr...

[Naveen Bibinaga]

Thanks for your reply. I checked with both of the data types but no luck so far.

[!NoItAll]

Ok - are you passing IntRequestHandle as a parameter to get the return value in that variable - or are you supposed to be passing in a valid handle? Looking at your code it looks like IntRequestHandle is set to 0 when you pass it in - and I imagine that would be an invalid handle if the function is looking for an existing handle. It would appear that you have to provide a valid handle to the process for which you are checking status rather then passing in 0.
Maybe, however IntRequestHandle returns a handle you use later on - it's not clear to me.

[Naveen Bibinaga]

I crosschecked with the DAQ card manual and here is the explanation-
PCMDigitalInput performs the configuration portion of a digital input request. For a new configuration,
the application program sets request_handle to 0 before calling PCMDigitalInput. PCMDigitalInput
then analyzes the data structure specified by user_request to determine if all of the parameters are valid and if the requested operation can be performed by the device specified by logical_device. If the
requested operation is valid, PCMDigitalInput assigns request_handle a unique non-zero value. This
request handle is used to identify this request in all future operations.

And about the error code 150 -

150 Invalid request handle.
A request could not be found with the specified request handle. Make sure the configuration procedure (PCMAnalogInput, PCMAnalogOutput, PCMDigitalInput, or PCMDigitalOutput) executed successfully and that the request handle matches the value returned by the configuration procedure

[!NoItAll]

Well, That all seems confusing. The error (150) is indicating it got a handle it didn't like for a call that is supposed to return a handle.
Ok - another tack...
Your instantiation of the function looks too VB6ish to me...

Declare Function PCMDigitalInputVB Lib "PCMDrvVB.DLL" (ByVal logical_device As Short, ByRef Request As DigioRequest, ByRef handle As Short) As Short

seems like it needs proper decoration.

Try:

<DLLImport("PCMDrvVB.DLL", SetLastError:=True, CharSet:=CharSet.Auto)> _
Private Function PCMDigitalInputVB(ByVal logical_device As IntPtr, ByRef Request As DigioRequest, ByRef handle As IntPtr) As IntPtr
End Function
 

I changed your Shorts to IntPtr - but you might try Integer, Long, Short - it's never clear how data types are handled and returned in external DLLs.

[Naveen Bibinaga]

Thank you!...I will try and keep you updated

[Naveen Bibinaga]

I tried all the data types and no luck still....
But I would like to point you to this specific function through which I get the address of the variable, that I pass to "PCMDigitalInputVB" function

lngRetBufferAdd = PCMGetAddressOfVB(channel)

**************Declaration**********

Declare Function PCMGetAddressOfVB Lib "PCMDrvVB.DLL" (ByRef pointer As Integer) As Integer

Do you think, the returned addresses are right? How do I check? This is the only thing I want to clarify.

I think you are right, its never clear how data types are handled in external Dll. I am breaking my head on this for the past 3 days. Now, I should probably start coding in C, this DAQ card also supports "C". Do you have any more suggestions?

I appreciate all your help.

[!NoItAll]

I don't see the value in getting the address since the DLL appears to have named entry points you are supposed to be able to use.
I guess I'm out of ideas now too. Have you tried contacting the company to see if they have any knowledge of how to use their libs in vb.net?
Also - is their c lib also a dll? You actually may have more luck marshaling the functions from that dll in vb.net then trying to use the lib made for vb6. I would think it would be much the same as using win32 APIs.