Patrick Bouldin KM5L
Thinking on this some more. Do you envision the CAT command relay coming in over the USB to the radio, or over the serial interface?
Even with an external interface like Arduino or PI, I can see where it could overwhelm the (slower speed) DB9? Should we go for broke and use the USB interface to communicate to the external interface? Or maybe that's what you already said, I wasn't sure.