Well, it's Bluerobotics. Thier system works differently from most.
Their LED lights work like a servo. The Pixhawk outputs a PWM signal (like a servo expects) and a controller board inside the light turns it up (brighter) or down (dimmer) depending on the pulse width. Hence the PWM signal for opening and closing the gripper.
The Newton Gripper is a lousy $500 POS that usually breaks after a couple dives. Tons of people on the BlueRobotics forum complain about it. Apparently they Made a plastic ACME nut instead of buying an off-the-shelf brass/steel one for a dollar, and it breaks, rendering the gripper useless. They also try and keep water from entering the gripper housing, which with a motor shaft is basically impossible, so when it floods it shorts out. Simply fill it with mineral oil (non-conductive) and the water won't have a void to fill. The explanation was, due to shipping regulations, an oil-filled unit would be prohibited from being shipped. Well, don't tell them it's full of oil then, iditots...lol. Easier to get forgiveness than permission.
IMO, ataching a gripper to a BlueROV2 or other (expensive but still a toy) ROV is silly. Trying to manuever the tiny lightweight ROV against the current and tether drag is hard enough when you want to look around...try doing it when you need to pick something up. Then the weak-ass gripper drops the object anyway. Just attach a stick with a hook on it. Save $500.
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My ROV design (eta, this year) is the size of a chest freezer, with used freon tanks for buoyancy, cement ingots for ballast, a steel drop cage with a baling-reel-style drum tether-management system (no slipring). Brushless drills (eBay) turning homemade aluminum ducted props, driven by brushless RC boat ESC's. LED light banks (coated with epoxy resin for waterproofing) controlled by brushed ESC's.
https://www.amazon.com/gp/product/B07F2536HR
(2) 9-dof homemade manipulators. They look like backhoe arms with linear servos instead of hydraulic rams (mineral-oil-filled servos turning acme-thread). TLE5010 magnetic position sensors on each joint provide position feedback to the linear servo controller board, giving realtime control of the arm/gripper via topside joystick interface. Tiny FPV cameras
https://www.amazon.com/Camera-Foxeer-Ra ... B07ZCMCVPC on each wrist to get a view from that angle to make it easier to grab stuff without stereoptic vision (no depth perception). 8 realtime camera views. 20x28' cabin-style pontoon boat with gantry-crane moon-pool ROV launch room/ 14x20 control room with cheap LED projectors.
https://www.amazon.com/gp/product/B08DX6983T
I can give links to info/parts suppliers if you wish to build anything. I like giving people ideas. Think outside the box. 3D printing is cool but it isn't the answer to everything. It's easier to buy a piece of pipe at the hardware store, and cut a hole in the side with a hole saw, than 3D print it...lol.