Unit 3 - Wrong references

Course Support ROS2 in 5 Days C++
1

In unit 3.1 you claimed melodic and dashing are sourced, but most updated noetic and foxy are actually sourced in the script above.

Plus in Unit 3.2 (Example 2) it asks for 4 shells, but 3 are actually used.

UPDATE: I’m trying example 3.1.
At first try, showimage opened Gacamole but the X window was frozen. I closed it and the second attempts prompted:

user:~$ ros2 run image_tools showimage

[INFO] [1661269340.475366706] [showimage]: Subscribing to topic 'image'
[INFO] [1661269341.344676430] [showimage]: Received image #camera_link
Received image #camera_link
[INFO] [1661269341.583070626] [showimage]: Received image #camera_link
Received image #camera_link
[INFO] [1661269341.692180233] [showimage]: Received image #camera_link
Received image #camera_link
[INFO] [1661269341.701041787] [showimage]: Received image #camera_link
Received image #camera_link

(showimage:1504): Gdk-ERROR **: 15:42:21.707: The program 'showimage' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadAccess (attempt to access private resource denied)'.
  (Details: serial 263 error_code 10 request_code 130 (MIT-SHM) minor_code 1)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the GDK_SYNCHRONIZE environment
   variable to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)

Changing unit didn’t solve the issue.
I then opened the GUI first, then I run imageshow and apparently now is working.

2

Hello @Gorgo,

welcome to the community!

You are right, noetic and foxy are sourced. The course was updated and we missed to change that sentence. Thanks for your feedback, I just updated that part.

Also true, thanks for pointing that out. That part was also updated now.

Just to be sure, if I understand right, you got it solved now, correct?

Again. many thanks for your comments, and please don’t hesitate to reach out if something else is unclear.

Cheers,

Roberto

3

Hi @rzegers , yes the X window worked eventually.

1 Like
4

@rzegers I took the chance to notify that in es. 4.1 you invite to type rostopic echo /counter but it doesn’t work. The correct command is the one in the box below, but I suggest to fix the reference in the text.

5

Hi @Gorgo,

oops! you are right, that command is a ROS1 command, I have changed the it to the correct one.
Thanks for taking the time to report this.

Roberto

6

This topic was automatically closed after 16 hours. New replies are no longer allowed.