Jeremie Deray
on 5 September 2019
Please note that this blog post has old information that may no longer be correct. We invite you to read the content as a starting point but please search for more updated information in the ROS documentation.
After exploring some ROS 2 subtleties and implementing some CLI tools we felt were missing, the time has come to get our hands even more dirty.
What better way to learn than by doing?
C’est en forgeant qu’on devient forgeron
Humm, pardon my french,
Practice makes perfect
To enter the realm of ROS 2 and discover its wording, its patterns, its colors, we decided it was time to do something a little larger than yet another publisher demo. Don’t get me wrong, these kinds of examples are great and often are a goto when the new things aren’t totally mastered yet. But dealing with an actual package better highlights the various intricacies of the code – how the pieces fit together and possibly blow up in your face.
We will leave covering the differences between ROS 1 and ROS 2 to past and future posts. Here instead we will advertise a ROS 2 port of a very useful set of ROS 1 tools: the teleop_tools package.
teleop_tools, tools for tele-operation
As its name suggests, the teleop_tools package is a collection of tools for tele-operating a robot. The three main components are mouse_teleop, key_teleop and joy_teleop.
First allow me to briefly motivate why this particular package was chosen for this exercise. First, I personally use at least two of the three tools on a (very) regular basis. They do a simple job but do it well. If you have never used them, give them a look, they are worth it. Especially if you are a ROS 2 user, there aren’t many such tools just yet and after testing these you may wonder why you’d bother with any others. Second, they aren’t overly complex, but their functionality covers a lot of the main aspects of ROS 2: parameters, topics, services, actions, etc. Combining these two facts, this package is an ideal candidate for better learning ROS 2 while bringing something very useful to the community.
mouse_teleop
Is your 12 000 dpi gamer mouse getting dusty? QtCreator isn’t quite the thrill of a FPS game? Mourn no more, for the mouse_teleop package allows you to send twist commands over a topic with your mouse!
How to use,
$ ros2 run mouse_teleop mouse_teleop
The following GUI should appear,
key_teleop
This package offers a very simple terminal-based interface to send twist commands at the tip of the four arrow keys of a keyboard.
How to use,
$ ros2 run key_teleop key_teleop
The following interface should appear in your terminal,
joy_teleop
The joy_teleop package is likely the more interesting of the three tools as it offers extended functionality compared to the previous two. Listening to a sensor_msgs/msg/Joy message (e.g. published by a joynode), it supports mapping different actions to each button (or buttons combination) of a remote controller through a configuration file. Mapped actions can be any of the three basic ROS 2 interfaces,
- publishing to a topic
- requesting a service
- sending an action goal
A brief example of a joy_teleop configuration file is given below, showcasing each of the three interfaces.
joy_teleop:
ros__parameters:
move:
type: topic
interface_type: geometry_msgs/msg/Twist
topic_name: cmd_vel
axis_mappings:
linear-x:
axis: 1
scale: 0.5
angular-z:
axis: 2
scale: 0.5
add_two_ints:
type: service
interface_type: example_interfaces/srv/AddTwoInts
service_name: add_two_ints
service_request:
a: 11
b: 31
buttons: [10]
fibonacci:
type: action
interface_type: action_tutorials/action/Fibonacci
action_name: fibonacci
action_goal:
order: 5
buttons: [4, 5, 6, 7]
How to use,
ros2 launch joy_teleop joy_teleop.launch.py
Note that the package provides a configuration file example to get you started.
Conclusion
teleop_tools just landed in ROS 2 Dashing, so it’s not available in the ROS Debian repositories just yet. If you’d like to use it now you can always build it from source, but it should be released soon. Overall the experience was successful– I learned more of the ins and outs of ROS 2, and now there’s another incredibly useful set of tools available to the community!
Do you know of any other tools such as teleop_tools that you are deeply missing in your new ROS 2 habits? Please let us know or feel free to share any other feedback and (hopefully not so many) tickets on github!
