Errors and inconsistencies in your instructions for the course project

Course Support ROS Basics In 5 Days (Python)
1

Hello,
I’m currently working my way through the Ros2 Basics in 5 Days course, and have just gotten to the point of trying to start the course project.
However, while I have been generally fairly impressed with your courses so far, I’m finding the instructions here to contain significant errors and/or omissions that are making it EXTREMELY confusing for someone who’s new to all this.

Some specific examples of errors and inconsistencies include:

  • You say in red to create all the files I create in catkin_ws, but then right under that in black you say to use ros2_ws
  • You say to teleop the robot using “rosrun turtlebot3_teleop turtlebot3_teleop_keyboard”, but it says it cannot find the appropriate executable. After some exploring and head scratching I realised that it’s actually “…teleop_key”

Some examples of things that just aren’t clear:

  • When following the instructions to launch the Gazebo simulation, I get a bunch of yellow warnings and red errors in the shell, and the shell never goes back to the command prompt. Is that normal??
  • When following the instructions for the ros1 bridge (which I note is a concept that was not addressed AT ALL in the actual course), you say to “dedicate a terminal to it” - but again after following the instructions I get some lines saying “Failed to look up XYZ”, and again that shell never returns to the command prompt. Is that normal?
  • If I follow what I was taught in the course so far to see what topics are available (using another shell since the first two are still busy), I don’t see any of the familiar ones from the course for e.g. getting the laser scanner data or controlling the robot’s movement. How am I supposed to know what to use?

Overall it feels like maybe this project was updated to a new version of ROS or something, but that the document has not been properly updated to reflect the changes.

Please advise - having paid good money for this course I’m a bit disappointed to be finding issues like these.
Regards
Jordan

2

Hi Jordan, welcome to the community!

Thank you for pointing out those errors to us. I will work on updating the instructions to prevent those confusions. I see that you said you are working in the ROS2 Basics course, correct (ros2_ws is the correct one to work under)? I ask because this section is for ROS1.

As for what is not clear:

  • The gazebo simulation will show errors, yes it is normal, but they are not related to the work you have to do and the simulation works. It doesn’t mean you won’t be able to use it.
  • You do need to have one dedicated terminal to launch the bridge. This error you mention, “Failed to look up XYZ”, when does that happen?
  • The topics that you need for the project is scan, odom and cmd_vel. If you don’t see any familiar ones, then it probably means the bridge isn’t working. To check, you should have your setup like this:
  1. In terminal 1, launch the simulation. Make sure you can see it when clicking the Gazebo button
  2. In terminal 2, run
source ~/.bashrc_bridge
ros2 run ros1_bridge dynamic_bridge --bridge-all-topics
  1. In terminal 3, run

ros2 topic list

And you should see the topics from above. Sometimes the bridge takes a while you you should run the command a couple of times.

I will let you know when the changes in the notebook are made, and please now that you would need to get a new forked copy the same way you did it the first time to reflect the changes.

3

The updated instructions are available now if you refork the rosject.

4

Hi Roalgoal,
thanks so much for your detailed reply! I will try everything you suggested (including reforking the rosject) tomorrow when I have time to work on it again :slight_smile:
And yes, I am doing the Ros2 in 5 days course - apologies that I did not notice I was actually posting to the Ros in 5 days forum!

Regards
Jordan

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