#24 System.InvalidCastException: Return argument has an invalid type.

[Olivier D]

I’m working in a team that automatized measurement to characterize chips. Our environment is write in Python and we build drivers for each equipment.
Today I have trouble with an Tektronix Logic Analyzer (TLA7012). Tektronix give a DLL write in .NET to access to the equipment (TlaNetInterfaces.dll) and examples in C++, C# or VB but not in Python.

We began to access using Ethernet with success, but when we use a method that return a .NET reference we have an error. The same code has been built with Labview without problem.

Here my code:

Import clr
Slot = 1
Clr.AddReference(“TlaNetInterfaces”) # load the DLL reference on TLA
configFile= “Connect.config” # config file that contain IP address of TLA
ITlaSystem_reference= clr.Tektronix.LogicAnalyzer.TpiNet.RemoteTlaSystem.Connect(configFile) #open connection on TLA
ITlaSystem_object= clr.Tektronix.LogicAnalyzer.TpiNet.ITlaSystem(ITlaSystem_reference)
Print ITlaSystem_object.SWVersion #return TLA software version 5.8.027.0 for my case
UserName= ITlaSystem_object.GetModuleBySlot(slot) # It should return a reference on module slot 1 in the TLA

The last line of this code give me this error:
System.InvalidCastException: Return argument has an invalid type.

I try to convert the value return, but without success, I always have this error, like .NET module in python don’t support a reference return from a method.
If I can get this reference I can access to all other part of the equipment for example running an acquisition, but actually it’s not possible.

Do you have an idea where is the problem?