ROS 2 Lab Handout

Ubuntu 22.04 · ROS 2 Humble. Do the steps in order. Each step names the terminal to type in.

Before the first lab

Get the files and install

sudo apt update && sudo apt install -y git
git clone https://github.com/DronaAviation/ROS2_Tutorial26.git ~/ROS2_Tutorial

bash ~/ROS2_Tutorial/install.sh

Takes 15–40 minutes.

Check the laptop

bash ~/ROS2_Tutorial/check_setup.sh

Expected: All checks passed. This laptop is ready. Fix every FAIL before Lab 1.

Open VS Code with four terminals

cd ~/ROS2_Tutorial
code .

Open LAB_HANDOUT.md, press Ctrl+Shift+V, drag the tab to the left half.
**Ctrl+** opens a terminal. Click the split icon three times. Rename them T1, T2, T3, T4`.

+---------------------------+---------------------------+
|                           |  T1          |  T2        |
|   LAB_HANDOUT.md          |--------------+------------|
|                           |  T3          |  T4        |
+---------------------------+---------------------------+

The setup line — every terminal, every time

source ~/ROS2_Tutorial/env.sh

Expected: ROS 2 humble ready (this laptop only). Tutorial folder: ...

Terminal keys: copy / paste = Ctrl+Shift+C / Ctrl+Shift+V. Ctrl+C stops the program.

Lab 1: Turtlesim

Setup line in T1, T2, T3, T4.

Experiment 1A — Drive the turtle with the keyboard

1.1 — T1

ros2 run turtlesim turtlesim_node

Expected: a blue window with a turtle. Don't type in T1 again.

1.2 — T2

ros2 run turtlesim turtle_teleop_key

Click inside T2, press the arrow keys.

✅ Checkpoint: ↑ in T2 moves the turtle.

Experiment 1B — See the topic that connects them

1.3 — T3

rqt_graph

Expected: /teleop_turtle → /turtle1/cmd_vel → /turtlesim. Close the window.

1.4 — T3 (one at a time)

ros2 node list

ros2 topic list

ros2 topic info /turtle1/cmd_vel

ros2 interface show geometry_msgs/msg/Twist

1.5 — T3

ros2 topic echo /turtle1/cmd_vel

Click T2, press ↑, ←, ↓, →. Watch T3. Then Ctrl+C in T3.

Experiment 1C — Drive the turtle yourself

1.6 — T3

ros2 topic pub --rate 1 /turtle1/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 2.0}, angular: {z: 1.8}}"

Expected: the turtle drives in circles. Ctrl+C to stop. Try: bigger z · negative z · x: 0.0.

1.7 — T3

ros2 service call /reset std_srvs/srv/Empty

python3 1_turtlesim/turtle_circle.py

Expected: one full circle, then the script exits.

✅ Checkpoint: your script drew the circle.

Experiment 1D — Read the turtle's position

1.8 — T4

python3 1_turtlesim/turtle_pose.py

Expected: x=… y=… heading=… twice a second. Drive with T2 and watch it change.

✅ Checkpoint: T4's numbers move when the turtle moves.

Experiment 1E — Change the plan (exercise)

Edit only STEPS in 1_turtlesim/turtle_circle.py:

STEPS = [
    ('side', 2.0, twist(forward=1.0)),
    ('turn', 1.0, twist(turn=math.pi / 2)),
] * 4

T3:

ros2 service call /reset std_srvs/srv/Empty

python3 1_turtlesim/turtle_circle.py

Then try: a triangle · a bigger circle · two laps. Reset before each run.

More: tasks T1–T4 in TASKS.md.

Tidy up

ros2 service call /reset std_srvs/srv/Empty

Ctrl+C in T4, T3, T1. q in T2. Then:

ros2 node list

Expected: no output. Close all four terminals.

Lab 2: Gazebo simulated drone

Four new terminals. Setup line in each.

Experiment 2A — Start the simulated drone and the bridge

2.1 — T1

ign gazebo -r multicopter_velocity_control.sdf

Expected: Gazebo opens with two drones. Ours is X3. The first start can take minutes.

2.2 — T2

ros2 run ros_gz_bridge parameter_bridge "/X3/gazebo/command/twist@geometry_msgs/msg/Twist]ignition.msgs.Twist"

Expected: Creating ROS->GZ Bridge. Leave it running.

2.3 — T3

ros2 node list

ros2 topic list

ign topic -l

Experiment 2B — Take off and hover from the terminal

2.4 — T3

ros2 topic pub --once /X3/gazebo/command/twist geometry_msgs/msg/Twist "{linear: {z: 0.5}}"

After 2–3 seconds:

ros2 topic pub --once /X3/gazebo/command/twist geometry_msgs/msg/Twist "{}"

✅ Checkpoint: the drone hovers.

Experiment 2C — Fly with our publisher

2.5 — T4

ros2 topic echo /X3/gazebo/command/twist

2.6 — T3

python3 2_gazebo/sim_drone.py

Expected: climb → circle → hover → descend → hover.

2.7 — T3

diff 1_turtlesim/turtle_circle.py 2_gazebo/sim_drone.py

Write down which lines are different.

Experiment 2D — Fly your own plan (exercise)

Edit STEPS in 2_gazebo/sim_drone.py. Try: climb higher · two circles · a square. To put the drone back on the ground: Ctrl+C in T1, run 2.1 again.

Experiment 2E — Fly the drone with the keyboard

Drone on the ground first (Ctrl+C in T1, run 2.1 again). Keep T2 and T4 running.

2.8 — T3

ros2 run teleop_twist_keyboard teleop_twist_keyboard --ros-args -r cmd_vel:=/X3/gazebo/command/twist

2.9 — T3 (click inside T3 first)

t climb · b descend · i / , forward / back · j / l turn · k hover

✅ Checkpoint: take off, fly forward, turn, land. Then Ctrl+C in T3.

Experiment 2F — Read the drone's height: a Python subscriber

2.10 — T2 (Ctrl+C first)

ros2 run ros_gz_bridge parameter_bridge "/X3/gazebo/command/twist@geometry_msgs/msg/Twist]ignition.msgs.Twist" "/model/x3/odometry@nav_msgs/msg/Odometry[ignition.msgs.Odometry"

Expected: Creating ROS->GZ Bridge and Creating GZ->ROS Bridge.

2.11 — T4 (Ctrl+C first)

python3 2_gazebo/sim_drone_pose.py

Expected: x=0.00 y=-0.00 height=0.05 m climb rate=+0.00 m/s, twice a second.

2.12 — T3

python3 2_gazebo/sim_drone.py

✅ Checkpoint: T4 shows the height rise to about 1.3 m, sag in the circle, and come back to 0.05 m.

More: tasks D1–D4 in TASKS.md.

Tidy up

Ctrl+C in T4, T2, T1. Close the Gazebo window if it stays open.

Lab 3: Real Pluto drone

⚠️ Safety — read before every flight

Open floor. 2 m clear, people behind the line, fresh battery.
Keyboard control reads the whole laptop. Space arms/disarms. Start other terminals before it. Stop it (Ctrl+C) before typing anywhere else.
Never run pluto_flight.py or ros2 topic pub while keyboard control runs.
Emergency stop: keyboard flight → space. Script flight → Ctrl+C.
Stop plutonode only when landed and disarmed. Close its terminal or press Ctrl+\.

Pre-flight

Battery charged and fitted; propellers OK
Drone on flat floor, nothing within 2 m
Laptop on Wi-Fi Pluto_XXXX, password dronaaviation
Four terminals, setup line run in each

Experiment 3A — Connect to the drone and read telemetry

3.1 — T1

ros2 run plutodrone plutonode

Expected: Pluto Connected.

3.2 — T2

ros2 run plutoserver plutoserver

Expected: Roll/Pitch/Yaw, Altitude, Battery. Tilt the drone by hand. Write down the battery voltage.

3.3 — T4

ros2 node list
ros2 interface show custom_msgs/msg/PlutoMsg
ros2 topic echo /drone_command custom_msgs/msg/PlutoMsg

From here until 3.5, do not type in any terminal.

Experiment 3B — Fly with the keyboard

3.4 — T3

ros2 launch plutoserver drone_comb.launch.py

Key	Action	Key	Action
space	Arm / disarm	↑ ↓	Forward / back
q	Take off	← →	Left / right
e	Land	a / d	Turn left / right
w / s	Up / down	r	Sticks to centre

Do not press t.

Sequence: space → q → gentle moves → e → space. Watch T4.

3.5 — T3: Ctrl+C. Typing is safe again.

Experiment 3C — Fly from the terminal

3.6 — T3 (one at a time, wait between)

Take off:

ros2 topic pub --once /drone_command custom_msgs/msg/PlutoMsg "{rc_roll: 1500, rc_pitch: 1500, rc_yaw: 1500, rc_throttle: 1500, rc_aux1: 1500, rc_aux2: 1500, rc_aux3: 1500, rc_aux4: 1500, command_type: 1}"

Land:

ros2 topic pub --once /drone_command custom_msgs/msg/PlutoMsg "{rc_roll: 1500, rc_pitch: 1500, rc_yaw: 1500, rc_throttle: 1500, rc_aux1: 1500, rc_aux2: 1500, rc_aux3: 1500, rc_aux4: 1500, command_type: 2}"

Disarm:

ros2 topic pub --once /drone_command custom_msgs/msg/PlutoMsg "{rc_roll: 1500, rc_pitch: 1500, rc_yaw: 1500, rc_throttle: 1300, rc_aux1: 1500, rc_aux2: 1500, rc_aux3: 1500, rc_aux4: 1200, command_type: 0}"

Copy the commands exactly. Do not leave out any rc_ field.

Experiment 3D — Fly with our script

3.7 — T3 (first run with the propellers removed)

python3 3_pluto/pluto_flight.py

Expected: idle → take off and hover → land → disarm. Watch T4. Then fit the propellers and run it again.

Experiment 3E — Your own telemetry server (exercise)

T2: Ctrl+C to stop plutoserver, then:

python3 3_pluto/pluto_telemetry.py

Expected: battery=… V altitude=… roll=… pitch=… yaw=…. Tilt the drone.

Tidy up

Land and disarm. Ctrl+C in T3, T4. Close the T1 and T2 terminals. Power off, unplug the battery.

Extra A: Topics, services, actions, parameters

Setup line in T1, T2, T3.

T1:

ros2 run turtlesim turtlesim_node

T2:

ros2 run turtlesim turtle_teleop_key

Everything below in T3, one at a time.

Nodes

ros2 node list

ros2 node info /turtlesim

Topics

ros2 topic list -t

ros2 topic info /turtle1/cmd_vel

ros2 topic echo /turtle1/pose

ros2 topic hz /turtle1/pose

ros2 topic pub --rate 1 /turtle1/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 1.0}, angular: {z: 1.0}}"

Message types

ros2 interface show geometry_msgs/msg/Twist

ros2 interface show turtlesim/msg/Pose

Services

ros2 service list -t

ros2 interface show turtlesim/srv/Spawn

ros2 service call /spawn turtlesim/srv/Spawn "{x: 2.0, y: 2.0, theta: 0.0, name: 'turtle2'}"

ros2 topic list

ros2 service call /clear std_srvs/srv/Empty

ros2 service call /reset std_srvs/srv/Empty

Actions

ros2 action list -t

ros2 interface show turtlesim/action/RotateAbsolute

ros2 action send_goal /turtle1/rotate_absolute turtlesim/action/RotateAbsolute "{theta: 1.57}" --feedback

Parameters

ros2 param list

ros2 param get /turtlesim background_b

ros2 param set /turtlesim background_r 255

ros2 service call /clear std_srvs/srv/Empty

Tidy up: Ctrl+C in T3 and T1. q in T2.

Extra B: Your own package

Setup line in T1, T2, T3.

B.1 — T1: make a workspace

mkdir -p ~/ros2_ws/src

cd ~/ros2_ws/src

B.2 — T1: create a package, then copy ours

ros2 pkg create --build-type ament_python --license MIT demo_pkg --dependencies rclpy std_msgs

ls demo_pkg

cp -r ~/ROS2_Tutorial/4_workspace/tutorial_pkg ~/ros2_ws/src/

Open package.xml and setup.py in ~/ros2_ws/src/tutorial_pkg.

B.3 — T1: build

cd ~/ros2_ws

colcon build --symlink-install

Expected: Summary: 2 packages finished. Then in every terminal:

source ~/ros2_ws/install/setup.bash

B.4 — publisher and subscriber

T1:

ros2 run tutorial_pkg talker

T2:

ros2 run tutorial_pkg listener

T3:

ros2 topic list

ros2 topic echo /chatter

Ctrl+C in T1, T2, T3.

B.5 — T1: launch both at once

ros2 launch tutorial_pkg talker_listener.launch.py

Ctrl+C to stop.

B.6 — T1: turtlesim and the square, one command

ros2 launch tutorial_pkg turtle_square.launch.py

Exercise

Copy talker.py to counter.py; publish an Int32 on /count. Add 'counter = tutorial_pkg.counter:main' to entry_points in setup.py.
colcon build --symlink-install, re-source, ros2 run tutorial_pkg counter, ros2 topic echo /count.
Add it to talker_listener.launch.py and launch all three.

Stuck? Check in this order: is the other program running (ros2 node list)? Is the topic name exact (ros2 topic list)? Did this terminal run the setup line? Then raise your hand.

Navigation Menu

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LAB_HANDOUT.md

LAB_HANDOUT.md

ROS 2 Lab Handout

Before the first lab

Get the files and install

Check the laptop

Open VS Code with four terminals

The setup line — every terminal, every time

Lab 1: Turtlesim

Experiment 1A — Drive the turtle with the keyboard

Experiment 1B — See the topic that connects them

Experiment 1C — Drive the turtle yourself

Experiment 1D — Read the turtle's position

Experiment 1E — Change the plan (exercise)

Tidy up

Lab 2: Gazebo simulated drone

Experiment 2A — Start the simulated drone and the bridge

Experiment 2B — Take off and hover from the terminal

Experiment 2C — Fly with our publisher

Experiment 2D — Fly your own plan (exercise)

Experiment 2E — Fly the drone with the keyboard

Experiment 2F — Read the drone's height: a Python subscriber

Tidy up

Lab 3: Real Pluto drone

⚠️ Safety — read before every flight

Pre-flight

Experiment 3A — Connect to the drone and read telemetry

Experiment 3B — Fly with the keyboard

Experiment 3C — Fly from the terminal

Experiment 3D — Fly with our script

Experiment 3E — Your own telemetry server (exercise)

Tidy up

Extra A: Topics, services, actions, parameters

Extra B: Your own package

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ROS 2 Lab Handout

Before the first lab

Get the files and install

Check the laptop

Open VS Code with four terminals

The setup line — every terminal, every time

Lab 1: Turtlesim

Experiment 1A — Drive the turtle with the keyboard

Experiment 1B — See the topic that connects them

Experiment 1C — Drive the turtle yourself

Experiment 1D — Read the turtle's position

Experiment 1E — Change the plan (exercise)

Tidy up

Lab 2: Gazebo simulated drone

Experiment 2A — Start the simulated drone and the bridge

Experiment 2B — Take off and hover from the terminal

Experiment 2C — Fly with our publisher

Experiment 2D — Fly your own plan (exercise)

Experiment 2E — Fly the drone with the keyboard

Experiment 2F — Read the drone's height: a Python subscriber

Tidy up

Lab 3: Real Pluto drone

⚠️ Safety — read before every flight

Pre-flight

Experiment 3A — Connect to the drone and read telemetry

Experiment 3B — Fly with the keyboard

Experiment 3C — Fly from the terminal

Experiment 3D — Fly with our script

Experiment 3E — Your own telemetry server (exercise)

Tidy up

Extra A: Topics, services, actions, parameters

Extra B: Your own package