Assuming the DLL files for the call processing tool contain all the
functionality you need for your testing, you may need to write a
wrapper library to "serve" the functional methods/functions in the DLL
to Robot Framework. If the DLL is written very basic (no complex data
structures, simple naming convention, etc.), you might be able to use
just the DLL "as is" depending on how you deploy the DLL with Robot
Framework.
You have two options:
Use IronPython to interface DLL with Robot as a test library. I may be
wrong, others can chime in here, but if you go this route, you will
likely have to write a wrapper in IronPython to expose your DLL to
Robot. There's no ready made solution to just use the DLL with
IronPython yet. Though the following issue has code that will be of
use to you:
http://code.google.com/p/robotframework/issues/detail?id=721
Or plug your DLL into a C# remote library server for Robot. Depending
on how the DLL is designed, you may or may not need to write a wrapper
class around the DLL to use it with the remote server. See this
project for more details:
http://code.google.com/p/sharprobotremoteserver/