For the isaac sim Conveyor belt node. I want to use ros to send send direction and velocity to the conveyor belt. How to do that?
If you are using ROS 2, you can use the generic action graph publisher/subscriber which should work for most message types: ROS 2 Generic Publisher and Subscriber — Omniverse IsaacSim
Also you could potentially use the WritePrimAttribute node to directly modify the conveyor belt prim via OmniGraph: Write Prim Attributes — Omniverse Extensions
If you want to do something more complex, making a custom ROS 2 node would be a better choice and here is the tutorial ROS 2 Python Custom OmniGraph Node — Omniverse IsaacSim.