Obtaining an activex COM interface from another COM interface

Question

I have Animatics SmartMotors and am using their SMIEngine.dll, which is a COM dll. I'm having trouble with a particular interface called ISMICMotion. The help information for obtaining an instance of it is as follows:
The client application
can obtain an instance of this interface, using the available ISMIComm interface.  The following examples show how to obtain
this interface in Visual Basic and Visual C++. 
In these examples CommInterface is assumed to be the available ISMIComm
interface.
Visual
Basic:
Dim
CMotionInterface As ISMICMotion
      Set
CMotionInterface = CommInterface
Visual
C++:
    ISMICMotionPtr    CMotionInterface;
    HRESULT
hr=CommInterface.QueryInterface(__uuidof(ISMICMotion),&CMotionInterface);
    if
(FAILED(hr))
          AfxMessageBox("The interface
\"ISMICMotion\" not found!");
          return;
I can open a reference to the ISMICMotion interface using Automation Open but the operation of the methods from the ISMICMotion interface is dependent on the ISMIComm interface. So opening an independent reference doesn't work and the ISMIComm interface does not have anything like a GetISMICMotion reference method.
Is there any way to achieve in LabVIEW what the above code does?
It seems to me that I should be able to acquire proper dependencies using only the exposed methods. Is it because the makers of the SMIEngine.dll have not followed some COM rules?
thanks for you help,
Louis

Answer 1

Hi Adam,
The issue I had was with initializing the  ISMICMotion interface which is used for Contouring Mode, also called Coordinated Motion. I've attached a VI with two initialization examples. The first in green is the typical init I use to control motors with individual Motor RefNums. If you are not trying to do Coordinated Motion with the CMotion interface then you would use this init. The second in orange is the init routine I used to start Coordinated Motion. The key there is the Variant to Data VI. I don't remember exactly how it works in this case because it was a while back when I figured this out, but I remember finding relevant information in the Developer Zone on using the Variant to Data VI with Automation or ActiveX.
I hope this helps.
best regards,
Louis
Attachments:
Types of SmartMotor Initialization Routines.vi ‏80 KB