Awesome project!! Great details and description and thanks for sharing the code. I wanted to know why most people recommend using Raspberry Pi and Arduino together and this is a concrete example of how it can be done. I recently built a kit robot based on Raspberry Pi + Ubuntu + ROS2 and ROS2 is such a pleasure to work with and very powerful framework. You may want to consider refactoring your code to run as a publisher/subscriber on top of ROS2.