Hi,

What about events published by the DataReceived handler.  On
which thread are those events picked up?  Will these be a
background thread as well?
<<

Yes (unless these events are specifically generated by code in a different
thread).

I'm not sure what you mean by "the object method for creating a
state machine".  Could you elaborate with, perhaps a pointer to
some reading material?
<<

What this means is that you create a class that implements all of the
features of your FSM (instead of inline code).  Then, you create an instance
of that class when you start your program, perhaps when you open the port.
Methods in the class might send commands, wait responses, or process serial
data via a method that is called from the DataReceived event, where you pass
it the serial data that generated the event.

The class itself would have data that represents state (private variables)
and data that represent results that you want to relay to the calling
code -- and events for notification.  Unless this class creates a seperate
thread (and it probably won't), any event notifications based on
DataReceived data will execute in the thread context of the background
thread.

I have a FSM that decodes GPS data (for example) in my book that uses this
form.  I'm sure there are others around.  However, these sort of things tend
to be "designed for a purpose" and while useful as guides will be just that.

Dick