turtlesim | Notion

Yes, turtlesim exists in both ROS 1 and ROS 2, but with some differences in implementation and usage. Here's a breakdown:

Turtlesim in ROS 1 vs. ROS 2

Feature	ROS 1 Turtlesim	ROS 2 Turtlesim
Purpose	Basic 2D simulator for learning ROS 1	Updated 2D simulator for learning ROS 2
Node Structure	Uses ROS 1 nodes (`roscore` required)	Uses ROS 2 nodes (no central `roscore`)
CLI Commands	`rosrun turtlesim turtlesim_node`	`ros2 run turtlesim turtlesim_node`
Teleop	`rosrun turtlesim turtle_teleop_key`	`ros2 run turtlesim turtle_teleop_key`
Parameters	Accessed via `rosparam`	Managed with `ros2 param` commands
Actions	Not natively supported	Includes actions (e.g., `rotate_absolute`)
QoS	N/A	Configurable via DDS QoS policies
Domain ID	N/A	Uses domain IDs for network isolation

Core Functionality: Both simulate a turtle robot in a 2D environment for teaching ROS fundamentals (nodes, topics, services).
Visualization: Use similar GUI windows with a movable turtle and pen trails.
Basic Topics: /cmd_vel (velocity commands), /pose (turtle position), and /color_sensor (trail color).

Architecture:
- ROS 1: Relies on a central roscore for node discovery.
- ROS 2: Uses decentralized discovery via DDS, eliminating the need for roscore[^8^].
Advanced Features:
- ROS 2: Adds native support for actions (e.g., /turtle1/rotate_absolute) and parameters with dynamic reconfiguration[^3^][^6^].
- ROS 1: Limited to basic services like /spawn and /kill.
CLI Tools:
- ROS 2: Uses ros2 CLI (e.g., ros2 topic pub instead of rostopic pub).
- ROS 1: Relies on rosrun, rostopic, and rosservice.

bash*# Start simulator* roscore & rosrun turtlesim turtlesim_node rosrun turtlesim turtle_teleop_key

`bash*# Start simulator* ros2 run turtlesim turtlesim_node ros2 run turtlesim turtle_teleop_key

# Rotate turtle using an action ros2 action send_goal /turtle1/rotate_absolute turtlesim/action/RotateAbsolute "{theta: 1.57}" --feedback`

Educational Tool: It remains the flagship example for teaching ROS concepts like nodes, topics, and services[^3^][^6^].
Backward Compatibility: Ensures a smooth transition for users migrating from ROS 1 to ROS 2.
Lightweight Testing: Useful for debugging ROS network configurations without hardware[^7^].