I am trying to control a FT601 USB3 interface chip via a C# wrapper that FTDI provide. Unfortunately, they don’t provide an example of using VB.net to do this, but advise that it should be possible. I have written a simple test program to see if this works and it appears to have no errors, but running the call results in a ‘System.IO.FileNotFoundException’, despite having referenced the dll in the project. It seems that I may not be calling the dll correctly, but I haven’t spotted the problem.

Module Module1
    Public Sub FTDread()
        'Find & Open all FTDI devices attached
        Dim ftStatus As FTDI.FT_STATUS = FTDI.FT_STATUS.FT_OK
        Dim d3xxDevice As New FTDI()
        Dim ulNumDevices As UInt32
        ftStatus = d3xxDevice.GetNumberOfDevicesConnected(ulNumDevices)
        If ftStatus <> FTDI.FT_STATUS.FT_OK OrElse ulNumDevices = 0 Then
            Return
        End If
        MsgBox(ulNumDevices)
    End Sub
End Module

Here is the error as shown in VB.net

Exception thrown: ‘System.IO.FileNotFoundException’ in StarMos.dll An
exception of type ‘System.IO.FileNotFoundException’ occurred in
StarMos.dll but was not handled in user code Could not load file or
assembly ‘FTD3XX_NET, Version=1.3.0.10, Culture=neutral,
PublicKeyToken=null’. The system cannot find the file specified.

‘StarMos.exe’ (CoreCLR: clrhost): Loaded ‘C:Program FilesMicrosoft
Visual
Studio2022CommunityCommon7IDEPrivateAssembliesRuntimeMicrosoft.VisualStudio.Debugger.Runtime.NetCoreApp.dll’.
Skipped loading symbols. Module is optimized and the debugger option
‘Just My Code’ is enabled. ‘StarMos.exe’ (CoreCLR: clrhost): Loaded
‘C:Program
FilesdotnetsharedMicrosoft.NETCore.App7.0.15netstandard.dll’.
Skipped loading symbols. Module is optimized and the debugger option
‘Just My Code’ is enabled. The program ‘[29168] StarMos.exe’ has
exited with code 4294967295 (0xffffffff).