Course navigation

Week 2: Systems and Perception
Course mapDay 1Week 2Previous dayNext day

Day 8

ROS 2 Jazzy: install, nodes, topics, services

This is a valid v1.0 placeholder page for the later curriculum arc. Full interactive lab treatment ships after Week 1 dogfooding.

LECTURE & READING

Glossary primer (12 min)

  • ROS 2 — Open-source middleware framework for robotics. Successor to ROS 1, built on DDS (Data Distribution Service). Jazzy Jalisco is the current LTS release (May 2024 → May 2029).
  • DDS — Real-time pub/sub protocol; ROS 2's default transport layer. Cyclone DDS is the most-used implementation in 2026.
  • Node — A ROS process. Each node owns part of the system: a camera driver, a planner, a Control & PlanningControllerThe algorithm or system that turns desired behavior into motor commands..
  • Topic — A named, typed message stream. Many-to-many: any node can publish, any node can subscribe.
  • Message — A typed data packet. Standard messages live in std_msgs, geometry_msgs, sensor_msgs.
  • Service — Synchronous request/response between two nodes (e.g. "set parameter").
  • Core ConceptsActionA command the robot sends to its motors, controller, or low-level system. — Long-running Core ConceptsGoalThe desired outcome or target state for a robot task. with Control & PlanningFeedbackInformation returned from sensors during action to help correct behavior. (e.g. "navigate to pose"; reports progress, can be cancelled).
  • Manipulation & TasksWorkspaceThe region of space the robot can reach. — A directory tree (src/, build/, install/, log/) where you build ROS 2 packages with colcon.
  • Lifecycle node — A node with explicit states (Unconfigured → Inactive → Active). Standard for production.
  • rclpy / rclcpp — Python and C++ client libraries.

Real-world analogy

A ROS 2 system is a small office. Topics are bulletin boards anyone can pin notes to. Services are walking up to a colleague's desk and asking a yes/no question. Actions are submitting a multi-day project request and getting periodic status updates. Nodes are individual employees, each with one job. DDS is the building's intercom.

Hour 1 — Install ROS 2 Jazzy and verify

Pick one of the two paths.

Path A: native Ubuntu 24.04 (recommended for laptops). Follow the official guide ~30 min: https://docs.ros.org/en/jazzy/Installation/Ubuntu-Install-Debs.html

# Add ROS 2 apt repository
sudo apt update && sudo apt install -y curl gnupg lsb-release
sudo curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -o /usr/share/keyrings/ros-archive-keyring.gpg
echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/ros-archive-keyring.gpg] http://packages.ros.org/ros2/ubuntu $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/ros2.list

sudo apt update
sudo apt install -y ros-jazzy-desktop ros-dev-tools python3-colcon-common-extensions

# Source — add to ~/.bashrc for persistence
echo "source /opt/ros/jazzy/setup.bash" >> ~/.bashrc
source ~/.bashrc

Path B: Docker (recommended on macOS or if you don't want to install system-wide).

docker pull osrf/ros:jazzy-desktop-full
docker run -it --rm --name ros2 \
    --network=host \
    -v ~/robo47:/workspace \
    osrf/ros:jazzy-desktop-full /bin/bash

Verify install (either path):

ros2 --version
ros2 doctor

Expected output:

ros2 cli version: 0.32.x
1/N check failed
...
All N checks passed

Some warnings (e.g. "QoS overrides") are normal. Doctor failing more than 2 checks means something went wrong; usually re-source.

Hour 2 — Concept primer

  • Watch ~50 min of these in order:
  • Quick ROS 2 conceptual overview, "Introduction to ROS Part 1: What is the Core ConceptsRobotA physical system with sensors and actuators that can observe the world and take actions. Operating System?"

    Video

    Quick ROS 2 conceptual overview, "Introduction to ROS Part 1: What is the Core ConceptsRobotA physical system with sensors and actuators that can observe the world and take actions. Operating System?

    Open source
  • Articulated Robotics "Getting Ready to Build Robots with ROS" Lessons 1–4:
  • Lesson 1, "Five Things You Need Before Starting With ROS"

    Video

    Lesson 1, "Five Things You Need Before Starting With ROS

    Open source
  • Lesson 2, "Setting Up Your Network for ROS"

    Video

    Lesson 2, "Setting Up Your Network for ROS

    Open source
  • Lesson 3, "How to install ROS"
  • Lesson 4, "10 things you need to know about ROS"

    Video

    Lesson 4, "10 things you need to know about ROS

    Open source
  • Read ROS 2 Concepts page: https://docs.ros.org/en/jazzy/Concepts.html

LAB

Hour 3 — Lab: build a publisher/subscriber pair (75 min)

What you're building. A two-node ROS 2 system: a Python talker node publishing std_msgs/String messages at 2 Hz on the /chatter topic, and a Python listener node subscribing to /chatter and printing each message it receives. You'll build them with colcon, run both in tmux panes, and inspect the system with ros2 topic echo, ros2 topic hz, and rqt_graph.

What success looks like at the end. You have: 1. A Manipulation & TasksWorkspaceThe region of space the robot can reach. ~/robo47/w2-systems/ros2_ws/ with one package chatter containing two scripts. 2. The talker terminal prints Publishing: 'Hello robotics 0' (1, 2, …) at 2 Hz. 3. The listener terminal prints I heard: 'Hello robotics 0' (1, 2, …) at the same rate. 4. ros2 topic hz /chatter reports average rate: 2.0. 5. rqt_graph shows two nodes connected by /chatter. 6. A screenshot of rqt_graph saved as figures/day8_rqt_graph.png.

Step 1 — Create the workspace and package (10 min)

mkdir -p ~/robo47/w2-systems/ros2_ws/src
cd ~/robo47/w2-systems/ros2_ws/src
ros2 pkg create chatter --build-type ament_python --dependencies rclpy std_msgs --node-name talker

Full source continues in the committed curriculum files. The v1.0 page exposes the day flow and lab surface without inventing content.

Completion controls unlock when this day graduates from placeholder to full lab.