I work for a medical company and we produce systems which typically are composed by a data-acquisition device connected via USB to a PC where some desktop application runs so that it can control the hardware and display the connected data in realtime. Our desktop software platform is C#/.Net/WPF.
We are considering to build a prototype where a Pi would control a handful of sensing devices, pre-process the data, and send this data to the PC or laptop. The Pi would also respond to commands and requests sent by the PC application.
I have looked around, but apparently the preferred way for us - direct USB connection - is not available, since the Pi USB is a "master".
I got confused, because I had the impression that it should be easy to connect PC and Pi via physical cable so that they could "talk" to each other, so the questions are:
Is there a way to physically connect Pi and PC so that applications could talk to each other through this connection?
If physical connection is not feasible, what is the most direct way to connect a PC and a Pi for the described purpose?
By "direct" I mean least dependent on external infrastructure (modems, routers, etc.) which might be non-existent on site.