If you’re using the RTS or DTR reset jumper on the serial servo controller, to you bring the controller out of reset by asserting (setting high) RTS or DTR, or is the signal inverted before pulling the reset pin? The manual doesn’t seem to specify which way it works.
It would be super-easy to figure out in person, but I got hooked on the micro serial servo controllers back when the full-sized one still looked like this:
-Adam