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[日本語のREADME](README_ja.md)
# 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](https://index.ros.org/doc/ros2/).
## 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](https://docs.ros.org/en/foxy/Releases/Release-Foxy-Fitzroy.html)
- 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](https://github.com/rclex/rclex_docker#available-versions-docker-tags).
### Docker environment
The pre-built Docker images are available at [Docker Hub](https://hub.docker.com/r/rclex/rclex_docker).
You can also try the power of Rclex with it easily. Please check ["Docker Environment"](#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](USE_ON_NERVES.md) section and [b5g-ex/rclex_on_nerves](https://github.com/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](https://github.com/elixir-lang/ex_doc)
and published on [HexDocs](https://hexdocs.pm).
You can find the docs at [https://hexdocs.pm/rclex](https://hexdocs.pm/rclex).
Please refer [rclex/rclex_examples](https://github.com/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](https://hex.pm/docs/publish).
You can install this package into your project
by adding `rclex` to your list of dependencies in `mix.exs`:
```elixir
defp deps do
[
...
{:rclex, "~> 0.8.3"},
...
]
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](https://docs.ros.org/en/foxy/Concepts/About-ROS-Interfaces.html) 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.
```elixir
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](https://hexdocs.pm/rclex/api-reference.html)! 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.
```elixir
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](https://github.com/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](https://hub.docker.com/r/rclex/rclex_docker), 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](https://github.com/rclex/rclex_docker#available-versions-docker-tags) 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 editted.
```
$ 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](https://github.com/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](https://github.com/rclex/rclex/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](https://github.com/takasehideki)
- [@HiroiImanishi](https://github.com/HiroiImanishi)
- [@kebus426](https://github.com/kebus426)
- [@shiroro466](https://github.com/shiroro466)
- [@s-hosoai](https://github.com/s-hosoai)
