🆕 Adding New Nodes & Packages

This guide explains how to create new ROS2 nodes and packages for the LIMO Pro + MyCobot + YOLO ecosystem, follow architectural best practices, integrate them into the workflow, and test them safely.

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📦 Creating a New Package

We use ROS2 Python packages for most nodes in this project.

cd ~/krish_ws/src
ros2 pkg create --build-type ament_python my_new_node

Structure:

my_new_node/
 ├── package.xml
 ├── setup.py
 ├── resource/my_new_node
 ├── my_new_node/__init__.py
 ├── my_new_node/my_new_node.py
 └── launch/

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🧩 Node Architecture Guidelines

Keep it Modular

Each node should have one core responsibility (e.g., detection, navigation, arm control) and communicate via ROS2 topics/services/actions.

Required structure inside a node:

1. Initialization

• Node name
• Parameters
• Publishers/Subscribers/Action clients
• Logging start message

2. Core Logic

• Main loop or callbacks
• State handling (if applicable)

3. Shutdown Handling

• Stop motors, close connections, save state

Example skeleton:

import rclpy
from rclpy.node import Node

class MyNewNode(Node):
    def __init__(self):
        super().__init__('my_new_node')
        self.get_logger().info("Node initialized.")

    def main_loop(self):
        pass  # Core logic here

def main(args=None):
    rclpy.init(args=args)
    node = MyNewNode()
    rclpy.spin(node)
    node.destroy_node()
    rclpy.shutdown()

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🔗 Integration Procedures

To integrate a new node:

1. Add to Launch File

Use launch_ros.actions.Node in full_system.launch.py with proper TimerAction so it starts after dependencies are ready.

2. Respect Existing Topics

• If publishing /target_pose, ensure format matches PoseStamped from object_detector.py.
• Avoid name collisions with existing topics.

3. Parameterize IPs and Paths

• For hardware nodes (like MyCobot), accept IP from --ros-args -p m5_ip:=....
• Never hardcode file paths — use ROS2 params.

4. Logging & Voice Feedback

• Use self.get_logger().info() for state changes.
• For user feedback, follow the say() function pattern in pick_node.py and mission_manager.py.

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🧪 Testing New Nodes

Simulation First

• Use RViz2 and fake data to test without risking hardware.
• If it's a detection node, feed it saved images.
• If it's a navigation node, test in Gazebo before the real robot.

Hardware Deployment

1. Ensure the workspace is clear of obstacles.
2. Launch only your new node + dependencies:

   ros2 run my_new_node my_new_node

3. Watch logs in real-time:

   ros2 topic echo /your_topic

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✅ Pre-Merge Checklist for New Nodes

• ☐ Package builds with colcon build --symlink-install
• ☐ Code follows Code Style Guidelines
• ☐ Node starts without errors or warnings
• ☐ Integration tested with full_system.launch.py
• ☐ Does not break Mission Manager or YOLO detection logic

📖 Read Next: Launch & Config File Creation

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Next: Launch Configuration Files