Questions tagged [topics]
The topics tag has no usage guidance.
107
questions
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2
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views
Topic Remapping at Runtime
Is it possible to remap the name of a topic at runtime?
To formulate the question more clearly, I need to remap the subscription of a node. I know that it can be done from ...
0
votes
1
answer
4
views
Best Practices for Publishing Lots of Related Data
I am developing a system using ROS2 Foxy on Ubuntu 20.04 that interfaces with a Allen Bradley ControlLogix PLC, speaking EtherNet/IP. We pull data from it at 20Hz, and there is a large amount of ...
alluring-mushroom
0
votes
1
answer
21
views
How to list the ros2 topics from a c++ node?
How to list the ros2 topics from a c++ node? I am interested in all the topics in the ros2 network.
Something equivalent to the commnand line ros2 topic list
I ...
0
votes
1
answer
5
views
Subscribe multiple topics using fuzzy string matching?
Hi, let's say I want to subscribe multiple topics in one node. All the topics are named with same prefix, such as ...
runtao
0
votes
1
answer
105
views
Send a 2D array through topics in ROS2
What is a proper way of sending 2D arrays through topics? I want to send small ones (4x6 for example) and so far I created an array msg (float64[]) and then use the .reshape function in order to send ...
jeferrandiz
0
votes
1
answer
2
views
ROS 2 Topic on different ROS DOMAINS
Hey guys,
I want to create a system where two robots are in different ROS_DOMAINS (one has ROS_DOMAIN_ID=1 and the other one has ROS_DOMAIN_ID=2 for example) and publish/subscribe to the same topic. ...
anonymous53443
0
votes
1
answer
3
views
Mechanism to prevent multiple publishers simultaneously publishing contradictory messages to a topic?
Is there a way to prevent multiple publishers simultaneously publishing messages to the same topic? I think I'm looking for a way for a node to lock access to a topic and release it when it's done. ...
grouchy
0
votes
1
answer
8
views
Having trouble publishing JointState msg from Arduino
Hi everyone, I am currently creating my own robotic arm actuated with Dynamixel motors.
The point of my code is to read the motor's position with an Arduino Mega and fulfill a sensor_msgs/JointState ...
Benjamin C
0
votes
1
answer
3
views
Is it correct to set topic names from parameters?
This is a mix of a practical question and an academic question.
When, if ever, is it correct to set topic names from parameters? If it is, how do you handle aspects such as the default topic name and ...
- 1,823
0
votes
1
answer
1
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Empty ConnectionHeader in MessageEvent (C++)
Hi all,
I am trying to get the publisher of a topic message in a C++ subscriber.
However, when I subscribe to the topic via a MessageEvent<> callback and try ...
RainerK
0
votes
1
answer
20
views
Returning a variables form a callback function C++
Hi everyone,
I'm developing a TCP communication ROS node and I want to send a string to another ROS node. In this case, I'm using a std_msgs::String message to send ...
drodgu
0
votes
1
answer
7
views
rosbag Python API not reading messages
Hi
I'm trying to read several topics using the rosbag Python API. However, I'm getting no message back at all. I can call ...
mun
0
votes
1
answer
2
views
About Topics and Namespaces
Hi all,
I'm new in ROS (I'm using Indigo and Ubuntu 16.04), so in order to start to manage ROS environments I have launched the dataset prepared for an algorithm that I have studied (concretely, SVO). ...
Ras Vince
0
votes
1
answer
2
views
Select the desired port
how to set a specific port (Ethernet) for publishing topics. I have 2 Ethernet ports, I want only one port to publish topics.
Originally posted by D0l0RES on ROS Answers with karma: 23 on 2018-12-27
...
D0l0RES
0
votes
1
answer
1
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Don't understand remapping
Could someone explain me in details what the remapping is doing? And how it is working?
Originally posted by S.Yildiz on ROS Answers with karma: 151 on 2018-09-18
Post score: 1
S.Yildiz
0
votes
1
answer
5
views
keeping state: Latched Topics vs ROS Parameters vs Service Request
Hi!
I'm trying to hold state about a piece of software in my stack. For instance, to tell if a fan is on or not from another process through ROS.
The 3 ways that come to mind is changing a parameter ...
- 5,290
0
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1
answer
3
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Partitions Settings in ROS2
Hello,
I ported a RWM for RTI Connext Micro DDS. This DDS does not support partitions. However ROS2 uses partitions for the topics (rt) and other messages in the RMW.
https://github.com/ros2/design/...
pokitoz
0
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1
answer
2
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Syntax of rqt_graph filters
I recently noticed, that you can use a wildcard character in rqt_graph to select node or topic names. For example "/imu*" would only show all nodes/topics which start with "/imu".
...
Andre Volk
0
votes
1
answer
3
views
How to make a server read the latest msg from a topic?
Greetings,
All I want to do is for my server to take a the latest msg from a topic and return it. The service server would take no inputs and return one output. Eg: Return robot position. Or Return a ...
RobotWhisperer
0
votes
1
answer
2
views
Is it possible to receive a msg on a certain topic by calling a service?
Hi all,
I'm working with gazebo, where I created an indoor environment and a mobile robot. The robot is equipped with an RGB-D camera and a logical_camera. Now, I would like to write a node that, ...
schizzz8
0
votes
1
answer
1
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ROS Answers SE migration: topic question
ubuntu 16.04 ROS kinetic
as per http://wiki.ros.org/ROS/Tutorials/UnderstandingTopics, i have listed my verbose details on topics in use rn:
...
moonspacedancer
0
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1
answer
1
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nodes and topics -like i'm 5
I am doing the ROS beginner tutorials and am on the 'understanding nodes' one. What actually is a topic? I see that a node is essentially an executable file and they communicate w eachother using ...
moonspacedancer
0
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1
answer
1
view
Is there a package for topic diagnostics/message rate tracking and warning?
I am interested in having something like a package with general nodes that subscribe to topics and publish warnings when messages aren't being sent or are coming in at the wrong rates and that ...
micah.corah
0
votes
1
answer
4
views
How should a subscriber interpret multiple messages upon subscription?
If I have multiple nodes who each latch a message onto a particular topic, a node that later subscribes to that topic will receive multiple messages immediately upon subscription. If those message ...
BJP
0
votes
1
answer
1
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What tools are available for persistent storage in ROS?
I have a small amount of information (e.g., camera position and orientation) that I would like to persist through roscore shutdowns and restarts. There are potentially multiple providers and multiple ...
BJP
0
votes
1
answer
2
views
Is there a way to call spinOnce for a specific subscriber?
Inside my node I have several callbacks. I want to avoid using spinOnce() inside my node as much as possible since the current job should always finish what it is doing before the next callback begins....
cpagravel
0
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1
answer
3
views
Is it possible to add topic to Rviz from command line?
I want my topics to be added automatically to Rviz. Is it possible??
Wanted to know whether there are commands to add topics
Originally posted by shashankbhat on ROS Answers with karma: 3 on 2017-03-...
shashankbhat
0
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1
answer
1
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How to subscribe to published topics in Baxter SDK environment
I have a c++ program that publishes three topics.
When the rostopic list command is used on the terminal it displays the list of ros topics . After running the code ...
fundamentals
0
votes
1
answer
3
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[Solved] C++: ApproximateTime with more than two topics?
Hi @all,
short version:
Could you please provide me with a full version for synchronizing up to eight image topics with ROS?
long version:
I am currently trying to get my Synchronizer to work.
Thanks ...
BlenderEi
0
votes
1
answer
1
view
active/connected rostopics to terminal list or file
Is there a way to get the active or connected (i.e. excluding leaf topics) ROS topics as a list to the terminal or a text file? The topics can limited to only the active topics from ...
roboticom314
0
votes
1
answer
1
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Not receiving any data from my robot
Main Problem
I am currently trying to check if I am getting any data from the ARDrone 2.0 that I have on my desk. It is connected to the wifi and I can do a roslaunch ardrone_autonomy ardrone.launch. ...
sharan100
0
votes
1
answer
6
views
Is there any actual difference between a topic and a service?
http://wiki.ros.org/ROS/Technical%20Overview#Message_serialization_and_msg_MD5_sums
The above link quotes that:
Establishing a topic connection: Putting it all together, the sequence by which two ...
sam26
0
votes
1
answer
3
views
Connect 2 ros board
Hi, I have 2 arm boards running ros. I need to share the topics between the boards.
I want to use a wired connection, is the uart a good choice? (I've got also lan or usb on both boards)
Is it ...
RoboDroid
0
votes
1
answer
4
views
subsribe to two integer type msgs with one call back function
I tried to subscribe to two integer types .But lot of errors are showing .Please help me to correct the code
code:
...
anadgopi1994
0
votes
2
answers
6
views
astra_launch and astra_camera packages. Problems with RGB
Hello all;
I have recently purchased an Orbbec Astra Pro sensor as a substitute for the difficult to get Asus Xtion Pro Live.
I have installed astra_launch and astra_camera packages. As the sensor was ...
altella
0
votes
2
answers
2
views
How to profile message activity?
Are there any tools for profiling or collecting statistics on the types of message activity per node?
I'm trying to troubleshoot some nodes consuming excessive amounts of CPU, and to help diagnose the ...
Cerin
0
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1
answer
1
view
How to enter the callback function only whenever a topic is updated but otherwise keep doing something else?
Hello folks,
I'm still a beginner here and I'm trying to implement a node that checks if a certain topic is updated.
I need it to be like:
Whenever the topic updates->do something then return.
...
violets
0
votes
1
answer
3
views
time synchronizer for many topics ros
Hi all,
I have four different topics. I'm able to use timesynchronizer for two topics.
My question is can I use it for four topics at the same time?
Originally posted by b-sriram on ROS Answers with ...
b-sriram
0
votes
1
answer
1
view
remap to part of message
Hi. I have written my first node - a Quaternion to euler conversion node (using the tf library). The node subscribes to geometry_msgs::Quaternion and publishes geometry_msgs::Vector3.
I now want to ...
Orangelynx
0
votes
1
answer
3
views
Get topic rate from my node
Hi all! I have a node subscribed to a topic. In principle, the topic rate is constant but unknown from the node. Does exist a method to get the rate of this topic from my node program? Something ...
Rikki
0
votes
1
answer
1
view
Topic/msg inspection tool
All,
I am coming to ROS as an LCM user. One of the LCM tools that I found very useful was lcm-spy (http://lcm.googlecode.com/svn/www/manpages/lcm-spy.html). The tool provided a complete high-level ...
BSBingham
0
votes
1
answer
2
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Python class for subscribing data for several topics
Hello all,
I just get started with ros and now I am working with bagfiles and subscriber. Now I am trying to subscriber several topics from a bagfile using one node written in python. The following ...
Randerson
0
votes
1
answer
2
views
[Roscpp] How to subscribe to a topic once?
Hi guys
I have a little problem here. I am writing just small code for basic joint moves of my arm manipulator in ros. I want to start with topics some services and work with parameters just to train ...
Chickenman
0
votes
1
answer
1
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Publishing in different topics for each wheel
How can I (having a 6-wheeled robot and using the DiffDrivePlugin6w from hectorgazebo plugins) make that each wheel subscribes in a different topic: Now I've been able to make that all the wheels move ...
Ros_user
0
votes
1
answer
1
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No topics published after costmap_2d building from git source
Hi,
I was previously succesfully launching the default costmap_2d package that came with ROS hydro, Ubuntu 12.04, using the following launch file and yaml parameters file:
Parameters file:
...
Ishani Chatterjee
0
votes
1
answer
1
view
parameter_descriptions and parameter_updates topics
Dear friends,
I experiment with hector quadrotor simulation in Hydro. Most of the topics like the one for sonar of the altimeter includes additional topics like /sonar_height/parameter_descriptions ...
angelos.p
0
votes
1
answer
1
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Topic for motor current
Hi everyone,
is there a standard topic to output currents used by a motor? I know i can give efforts of motors in the joint state message but i also would like to provide the raw current values of the ...
heppner
0
votes
1
answer
2
views
Problem with two topics
Hi Ros users:
I have a launch file that it has 2 pkg when I run it. Here it is
...
Alvaro Salcedo
0
votes
1
answer
4
views
get variable from topic with python
I created a node and subscribe a topic (nav_msgs/Odometry Message) i want operate with the quaternion, how i can get it value? With python
i try it this way:
...
Porti77
0
votes
1
answer
1
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Prevent topics in custom node from being prefixed by node name
I wrote out a custom PID position controller for a turtlebot. Basically, it sends velocity to command for the straight-line path to a target. I'm having an annoying issue, though. Every topic that the ...
locustcox