I managed to control the virtual fader in Ardour via the fader on my DDX3216. However, I was not able to establish a connection in the other way: that is, controlling the fader on DDX by moving the virtual fader on Ardour.
Note that I can move the motorized fader of the DDX using other midi applications (such as MuMidi Controller). So I guess it is just a matter of having Ardour to send out the right Control Changes messages when moving its faders. Can this be done?
p.s. I use Ardour on a Mac OSX (10.4 – X11 version)