I think I see the diagram/layout you're referring to Forde. But in the PPT it never mentions the USB being used for HMI comm. It lists usb uses as programming, backplane connections, and firmware flashing. However it does say something about USB being used as a temporary device port (not sure exactly what that means). My gut said it wouldn't work, so I never tried it. Unless someone shoots down the theory here, I may give it a shot. I have a spare L1 controller and a PV component lying around somewhere.