build details

Show: section status errors & todos local changes recent changes last change in-page changes feedback controls

Operation - Using start_gui_tools, ROS tools and no-vnc

Modified 2021-03-13 by duckietown

A note on start_gui_tools

Modified 2021-02-17 by tanij

If you are very familiar with how ROS works and like command line interface, you can run:

laptop $ dts start_gui_tools DUCKIEBOT_NAME

to obtain a terminal (container actually) that is connected to the Duckiebot ROS network. In this terminal you can perform all ROS commands.

You can only start one instance of start_gui_tools container. If you want multiple terminal instances, it is recommended to use no-vnc.

You can add the AND Symbol at the end of your command to run it in the background.

Starting no-vnc images

Modified 2021-02-17 by tanij

To start a image that runs no-vnc, type:

laptop $ dts start_gui_tools --vnc DUCKIEBOT_NAME

Note that in here you input the Duckiebot hostname; do not include .local part.

To use no-vnc, use your browser and navigate to:

http://localhost:8087/

You can treat this environment as a typical Ubuntu machine with ROS installed, and configured to talk with your Duckiebot.

Verifying the output by using the ROS utilities and command line

Modified 2021-02-17 by tanij

Open up a terminal and use the commands below to check the data streams in ROS.

List topics

Modified 2020-07-27 by frank-qcd-qk

You can see a list of published topics with the command:

container $ rostopic list

For more information about rostopic, see Section 1.5 - rostopic.

You should see at least the following topics:

/hostname/camera_node/camera_info
/hostname/camera_node/image/compressed
/rosout
/rosout_agg

There might be other topics if you started other demos.

Show topics frequency

Modified 2021-02-17 by tanij

You can use rostopic hz to see the statistics about the publishing frequency:

container $ rostopic hz /hostname/camera_node/image/compressed

On a Raspberry Pi 3, you should see a number close to 30 Hz:

average rate: 30.016
    min: 0.026s max: 0.045s std dev: 0.00190s window: 841

Use Ctrl-C to stop rostopic.

Show topics data

Modified 2020-07-27 by frank-qcd-qk

You can view the messages in real time with the command rostopic echo:

container $ rostopic echo /hostname/camera_node/image/compressed

You should see a large sequence of numbers being printed to your terminal.

That’s the “image” — as seen by a machine.

rqt_image_view tool

Modified 2021-02-17 by tanij

To see what your Duckiebot sees, you can click on the RQT Image View application icon on the desktop. You will see the rqt_image_view starts up

The rqt image view window with dropdown menu

rqt_graph tool

Modified 2020-09-10 by frank-qcd-qk

If you want to explore the relationship between all the nodes, topics and tf, you can open up a terminal and run:

$ rqt_graph

This will open up a window that contains all the ROS topics being published, all the ROS nodes running, and it is a very handy tool to understand the relationship between nodes.

ROS Troubleshooting

Modified 2021-10-26 by tanij

My ros commands are not working. I cannot use tab to auto complete ROS commands.

You can fix that by sourcing devel/setup.bash.

$ source /code/catkin_ws/devel/setup.bash

I cannot connect to ROS master.

Go to Portainer of the robot to make sure the following containers are running without errors:

ROS
car-interface
duckiebot-interface

If they are not running, refer to Docker troubleshooting to make sure those containers are running.