The Create® 3 exposes ROS2 topics, actions, and services over both WiFi and the USB-C cable powering the Raspberry Pi. This gives users access to the battery state, sensor data, docking actions, and more. While the Create® 3 can be used with just the USB-C interface, in order to view the robot model on Rviz or run software such as SLAM or Nav2 from a user PC, the Create® 3 will require a WiFi connection.
The Raspberry Pi 4 on both the TurtleBot 4 and TurtleBot 4 Lite comes preinstalled with Ubuntu 20.04 Server, ROS2 Galactic, and TurtleBot 4 software. The latest TurtleBot 4 images can be found here. The purpose of the Raspberry Pi 4 is to run the TurtleBot 4 ROS nodes, run sensor ROS nodes, use bluetooth to connect to the TurtleBot 4 controller, access GPIO, and more.
The user's PC is used to configure the robot, visualise sensor data, run the TurtleBot 4 simulation, and run additional software. The PC is required to run Ubuntu 20.04 with ROS2 Galactic installed, or to use a Virtual Machine running Ubuntu 20.04. A typical laptop or desktop will offer significantly higher processing performance than the Raspberry Pi can, so running applications such as Nav2 or SLAM on the PC will provide significant performance improvements.