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Tutorial: Develop a ROS 2 package with pixi#

In this tutorial, we will show you how to develop a ROS 2 package using pixi. The tutorial is written to be executed from top to bottom, missing steps might result in errors.

The audience for this tutorial is developers who are familiar with ROS 2 and how are interested to try pixi for their development workflow.

Prerequisites#

  • You need to have pixi installed. If you haven't installed it yet, you can follow the instructions in the installation guide. The crux of this tutorial is to show you only need pixi!
  • On Windows, it's advised to enable Developer mode. Go to Settings -> Update & Security -> For developers -> Developer mode.

If you're new to pixi, you can check out the basic usage guide. This will teach you the basics of pixi project within 3 minutes.

Create a pixi project.#

pixi init my_ros2_project -c robostack-staging -c conda-forge
cd my_ros2_project

It should have created a directory structure like this:

my_ros2_project
├── .gitattributes
├── .gitignore
└── pixi.toml

The pixi.toml file is the manifest file for your project. It should look like this:

pixi.toml
[project]
name = "my_ros2_project"
version = "0.1.0"
description = "Add a short description here"
authors = ["User Name <user.name@email.url>"]
channels = ["robostack-staging", "conda-forge"]
# Your project can support multiple platforms, the current platform will be automatically added.
platforms = ["linux-64"]

[tasks]

[dependencies]

The channels you added to the init command are repositories of packages, you can search in these repositories through our prefix.dev website. The platforms are the systems you want to support, in pixi you can support multiple platforms, but you have to define which platforms, so pixi can test if those are supported for your dependencies. For the rest of the fields, you can fill them in as you see fit.

Add ROS 2 dependencies#

To use a pixi project you don't need any dependencies on your system, all the dependencies you need should be added through pixi, so other users can use your project without any issues.

Let's start with the turtlesim example

pixi add ros-humble-desktop ros-humble-turtlesim

This will add the ros-humble-desktop and ros-humble-turtlesim packages to your manifest. Depending on your internet speed this might take a minute, as it will also install ROS in your project folder (.pixi).

Now run the turtlesim example.

pixi run ros2 run turtlesim turtlesim_node

Or use the shell command to start an activated environment in your terminal.

pixi shell
ros2 run turtlesim turtlesim_node

Congratulations you have ROS 2 running on your machine with pixi!

Some more fun with the turtle

To control the turtle you can run the following command in a new terminal 

cd my_ros2_project
pixi run ros2 run turtlesim turtle_teleop_key
Now you can control the turtle with the arrow keys on your keyboard.

Turtlesim control

Add a custom Python node#

As ros works with custom nodes, let's add a custom node to our project.

pixi run ros2 pkg create --build-type ament_python --destination-directory src --node-name my_node my_package

To build the package we need some more dependencies:

pixi add colcon-common-extensions "setuptools<=58.2.0"

Add the created initialization script for the ros workspace to your manifest file.

Then run the build command

pixi run colcon build

This will create a sourceable script in the install folder, you can source this script through an activation script to use your custom node. Normally this would be the script you add to your .bashrc but instead you tell pixi to use it by adding the following to pixi.toml:

pixi.toml
[activation]
scripts = ["install/setup.sh"]
pixi.toml
[activation]
scripts = ["install/setup.bat"]
Multi platform support

You can add multiple activation scripts for different platforms, so you can support multiple platforms with one project. Use the following example to add support for both Linux and Windows, using the target syntax.

[project]
platforms = ["linux-64", "win-64"]

[activation]
scripts = ["install/setup.sh"]
[target.win-64.activation]
scripts = ["install/setup.bat"]

Now you can run your custom node with the following command

pixi run ros2 run my_package my_node

Simplify the user experience#

In pixi we have a feature called tasks, this allows you to define a task in your manifest file and run it with a simple command. Let's add a task to run the turtlesim example and the custom node.

pixi task add sim "ros2 run turtlesim turtlesim_node"
pixi task add build "colcon build --symlink-install"
pixi task add hello "ros2 run my_package my_node"

Now you can run these task by simply running

pixi run sim
pixi run build
pixi run hello
Advanced task usage

Tasks are a powerful feature in pixi.

  • You can add depends-on to the tasks to create a task chain.
  • You can add cwd to the tasks to run the task in a different directory from the root of the project.
  • You can add inputs and outputs to the tasks to create a task that only runs when the inputs are changed.
  • You can use the target syntax to run specific tasks on specific machines.
[tasks]
sim = "ros2 run turtlesim turtlesim_node"
build = {cmd = "colcon build --symlink-install", inputs = ["src"]}
hello = { cmd = "ros2 run my_package my_node", depends-on = ["build"] }

Build a C++ node#

To build a C++ node you need to add the ament_cmake and some other build dependencies to your manifest file.

pixi add ros-humble-ament-cmake-auto compilers pkg-config cmake ninja

Now you can create a C++ node with the following command

pixi run ros2 pkg create --build-type ament_cmake --destination-directory src --node-name my_cpp_node my_cpp_package

Now you can build it again and run it with the following commands

# Passing arguments to the build command to build with Ninja, add them to the manifest if you want to default to ninja.
pixi run build --cmake-args -G Ninja
pixi run ros2 run my_cpp_package my_cpp_node
Tip

Add the cpp task to the manifest file to simplify the user experience.

pixi task add hello-cpp "ros2 run my_cpp_package my_cpp_node"

Conclusion#

In this tutorial, we showed you how to create a Python & CMake ROS2 project using pixi. We also showed you how to add dependencies to your project using pixi, and how to run your project using pixi run. This way you can make sure that your project is reproducible on all your machines that have pixi installed.

Show Off Your Work!#

Finished with your project? We'd love to see what you've created! Share your work on social media using the hashtag #pixi and tag us @prefix_dev. Let's inspire the community together!

Frequently asked questions#

What happens with rosdep?#

Currently, we don't support rosdep in a pixi environment, so you'll have to add the packages using pixi add. rosdep will call conda install which isn't supported in a pixi environment.