Install ROS2
This is only to install ROS2-iron-desktop for quick desktop experiments. In general I’d like to use docker containers though.
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# Remove any corrupted ROS2 keyrings.
sudo rm /etc/apt/keyrings/ros-archive-keyring.gpg
sudo mkdir -p /etc/apt/keyrings
# Download ROS2 GPG key
curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.asc | sudo gpg --dearmor -o /etc/apt/keyrings/ros-archive-keyring.gpg
# Verify the GPG keys are added correctly
# Should see "ros-archive-keyring.gpg"
ls /etc/apt/keyrings/
sudo rm /etc/apt/sources.list.d/ros2.list
echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/ros-archive-keyring.gpg] http://packages.ros.org/ros2/ubuntu $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/ros2.list > /dev/null
sudo apt update
# install comprehensive ROS2, like rviz, rqt, and demos
sudo apt install -y ros-iron-desktop
sudo apt install -y python3-colcon-common-extensions
sudo apt install ros-iron-joint-state-publisher
sudo apt install ros-iron-xacro
echo "source /opt/ros/iron/setup.bash" >> ~/.bashrc
source ~/.bashrc
# Run a talker and listener.
ros2 run demo_nodes_cpp talker
ros2 run demo_nodes_cpp listener
Create a Python Package For Publisher & Subscriber
mkdir -p ~/ros2_ws/src && cd ~/ros2_ws/src- Create a package
ros2 pkg create --build-type ament_python --dependencies rclpy std_msgs--build-typespecifies that this is a python pkg.ros2 pkg create my_mixed_pkg --build-type ament_cmake --dependencies rclcpp rclpy std_msgsis the command for creating cmake and python package.- Package naming: in ros2, please use
_instead of-, like ` py_package_1instead ofpy-package-1`
- File Directory
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├── dummy_test
│ ├── demo.py
│ ├── __init__.py
├── package.xml
├── resource
│ └── dummy_test
├── setup.cfg
├── setup.py
└── test
├── test_copyright.py
├── test_flake8.py
└── test_pep257.py
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- `resource`: holds files that do not need executable permissions like config, launch files, data files etc.
- python executables **NEED executable permissions**, so they need to placed in `dummy_test`
setup.py: so this node executable could be run byros2 runcommand
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from setuptools import setup, find_packages
package_name = 'dummy_test'
setup(
name=package_name,
version='0.0.1',
packages=find_packages(),
install_requires=['setuptools', 'rclpy'],
zip_safe=True,
maintainer='Your Name',
maintainer_email='you@example.com',
description='A minimal ROS 2 publisher node',
license='Apache License 2.0',
entry_points={
'console_scripts': [
'demo = dummy_test.demo:main',
],
},
)
dummy_test/demo.py: this is the console script that could be found by the Python environment’sbin- Note:
main()function must be defined
- Note:
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import rclpy
from rclpy.node import Node
from std_msgs.msg import String
class MinimalPublisher(Node):
def __init__(self):
super().__init__('minimal_publisher')
self.publisher_ = self.create_publisher(String, 'topic', 10)
timer_period = 0.5 # seconds
self.timer = self.create_timer(timer_period, self.timer_callback)
self.i = 0
def timer_callback(self):
msg = String()
msg.data = 'Hello World: %d' % self.i
self.publisher_.publish(msg)
self.get_logger().info('Publishing: "%s"' % msg.data)
self.i += 1
def main(args=None):
rclpy.init(args=args)
minimal_publisher = MinimalPublisher()
rclpy.spin(minimal_publisher)
# Destroy the node explicitly
# (optional - otherwise it will be done automatically
# when the garbage collector destroys the node object)
minimal_publisher.destroy_node()
rclpy.shutdown()
- Build and run
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chmod +x dummy_test/resource/dummy_test
colcon build --packages-select dummy_test --symlink-install
source install/setup.bash
ros2 run dummy_test demo
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- `--symlink-install` allows in-place modifications in `colcon build --packages-select dummy_test --symlink-install`
Packaging & Build System
- In ROS2, cpp files require
CMakeLists.txt, python files requiresetup.cfgandsetup.py:
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cpp_package_1/
CMakeLists.txt
include/cpp_package_1/
package.xml
src/
py_package_1/
package.xml
resource/py_package_1
setup.cfg
setup.py
py_package_1/
