日本語のREADME

Rclex

Rclex is a ROS 2 client library for Elixir.

This library lets you perform basic ROS 2 behaviors by calling out from Elixir code into the RCL (ROS Client Library) API, which uses the ROS 2 common hierarchy.

Additionally, publisher-subscriber (PubSub) communication between nodes and associated callback functions are executed by tasks, which are part of a lightweight process model. This enables generation of and communication between a large number of fault-tolerant nodes while suppressing memory load.

What is ROS 2

ROS (Robot Operating System) is a next-generation Robot development platform. In both ROS and ROS 2, each functional unit is exposed as a node, and by combining these nodes you can create different robot applications. Additionally, communication between nodes uses a PubSub model where publisher and subscriber exchange information by specifying a common topic name.

The biggest difference between ROS and ROS 2 is that the DDS (Data Distribution Service) protocol was adopted for communication, and the library was divided in a hierarchical structure, allowing for the creation of ROS 2 client libraries in various languages. This has allowed for the creation of a robot application library in Elixir.

For details on ROS 2, see the official ROS 2 documentation.

Recommended environment

The environment where host (development) and target (operation) are the same

Currently, we use the following environment as the main development target:

• Ubuntu 20.04.2 LTS (Focal Fossa)
• ROS 2 Foxy Fitzroy
• Elixir 1.13.4-otp-25
• Erlang/OTP 25.0.3

For other environments used to check the operation of this library, please refer to here.

Docker environment

The pre-built Docker images are available at Docker Hub. You can also try the power of Rclex with it easily. Please check "Docker Environment" section for details.

Nerves device (target)

rclex can be operated onto Nerves. In this case, you do not need to prepare the ROS 2 environment on the host computer to build Nerves project (so awesome!).

Please refer to Use on Nerves section and b5g-ex/rclex_on_nerves example repository for more details!

Features

Currently, the Rclex API allows for the following:

1. The ability to create a large number of publishers sending to the same topic.
2. The ability to create large numbers of each combination of publishers, topics, and subscribers.

Documentation can be generated with ExDoc and published on HexDocs.
You can find the docs at https://hexdocs.pm/rclex.

Please refer rclex/rclex_examples for the examples of usage along with the sample code.

How to use

This section explains the quickstart for rclex onto the environment where ROS 2 and Elixir have been installed.

Create the project

First of all, create the Mix project as a normal Elixir project.

mix new rclex_usage
cd rclex_usage

Install rclex

rclex is available in Hex.

You can install this package into your project by adding rclex to your list of dependencies in mix.exs:

  defp deps do
    [
      ...
      {:rclex, "~> 0.8.5"},
      ...
    ]
  end

After that, execute mix deps.get into the project repository.

mix deps.get

Setup the ROS 2 environment

source /opt/ros/foxy/setup.bash

Configure ROS 2 message types you want to use

Rclex provides pub/sub based topic communication using the message type defined in ROS 2. Please refer here for more details about message types in ROS 2.

The message types you want to use in your project can be specified in ros2_message_types in config/config.exs. Multiple message types can be specified separated by comma ,.

The following config/config.exs example wants to use String type.

import Config

config :rclex, ros2_message_types: ["std_msgs/msg/String"]

Then, execute the following Mix task to generate required definitions and files for message types.

mix rclex.gen.msgs

If you want to change the message types in config, do mix rclex.gen.msgs again.

Write Rclex code

Now, you can acquire the environment for Rclex API! Of course, you can execute APIs on IEx directly.

Here is the simplest implementation example lib/rclex_usage.ex that will publish the string to /chatter topic.

defmodule RclexUsage do
  def publish_message do
    context = Rclex.rclexinit()
    {:ok, node} = Rclex.ResourceServer.create_node(context, 'talker')
    {:ok, publisher} = Rclex.Node.create_publisher(node, 'StdMsgs.Msg.String', 'chatter')

    msg = Rclex.Msg.initialize('StdMsgs.Msg.String')
    data = "Hello World from Rclex!"
    msg_struct = %Rclex.StdMsgs.Msg.String{data: String.to_charlist(data)}
    Rclex.Msg.set(msg, msg_struct, 'StdMsgs.Msg.String')

    # This sleep is essential for now, see Issue #212
    Process.sleep(100)

    IO.puts("Rclex: Publishing: #{data}")
    Rclex.Publisher.publish([publisher], [msg])

    Rclex.Node.finish_job(publisher)
    Rclex.ResourceServer.finish_node(node)
    Rclex.shutdown(context)
  end
end

Please also check the examples for Rclex.

• rclex/rclex_examples

Build and Execute

mix compile
iex -S mix

Operate the following command on IEx.

iex()> RclexUsage.publish_message

00:04:40.701 [debug] JobExecutor start
 
00:04:40.705 [debug] talker0/chatter/pub
Rclex: Publishing: Hello World from Rclex!

00:04:40.706 [debug] publish ok
 
00:04:40.706 [debug] publisher finished: talker0/chatter/pub
 
00:04:40.710 [debug] finish node: talker0
{:ok, #Reference<0.2970499651.1284374532.3555>}

You can confirm the above operation by subscribing with ros2 topic echo from the other terminal.

$ source /opt/ros/foxy/setup.bash
$ ros2 topic echo /chatter std_msgs/msg/String
data: Hello World from Rclex!
---

Enhance devepoment experience

This section describes the information mainly for developers.

Docker environment

This repository provides a docker compose environment for library development with Docker.

As mentioned above, pre-built Docker images are available at Docker Hub, which can be used to easily try out Rclex. You can set the environment variable $RCLEX_DOCKER_TAG to the version of the target environment. Please refer to here for the available environments.

# optional: set to the target environment (default `latest`)
export RCLEX_DOCKER_TAG=latest
# create and start the container
docker compose up -d
# execute the container (with the workdir where this repository is mounted)
docker compose exec -w /root/rclex rclex_docker /bin/bash
# stop the container
docker compose down

Automatic execution of mix test, etc.

mix test.watch is introduced to automatically run unit test mix test and code formatting mix format every time the source code was edited.

$ mix test.watch
# or, run on docker by following
$ docker compose run --rm -w /root/rclex rclex_docker mix test.watch

Confirmation of operation

To check the operation of this library, we prepare rclex/rclex_connection_tests to test the communication with the nodes implemented with Rclcpp.

cd /path/to/yours
git clone https://github.com/rclex/rclex
git clone https://github.com/rclex/rclex_connection_tests
cd /path/to/yours/rclex_connection_tests
./run-all.sh

In GitHub Actions, we perform CI on multiple environments at Pull Requests. HOwever, we cannot guarantee operation in all of these environments.

Maintainers and developers (including past)

• @takasehideki
• @HiroiImanishi
• @kebus426
• @shiroro466
• @s-hosoai