How to setup serial port for gimbal control?

Can anoyone point me in the right direction to control pan/tilt of this camera via one of my serial ports using ardupilot? The trigger etc already works via mavlink. It shows it can use sbus or “serial” and I have pretty much confirmed it is not using sbus. This was taken off of a Swan Voyager and I cant find anything in the oem dump that indicates how it is being controlled. The dials are mapped to channels 12 and 13 and work with the oem board. I just dont know what protocol is being sent to the camera from the oem board so I dont know how to configure the serial port. Thanks

Camera manual

Original PIX4 params