Questions tagged [rostopic]

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ROS message sent but not received

I'm using ROS in my project and I need to send one message from time to time. I have this function: ...
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Is there something like a node supervisor "class" available?

I want a process to control my nodes, starting pausing, restarting, checking if it still is operational etc. Like a library you add to the node doing that with services and is able to set a value to ...
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Synchronous communication with gazebo

Hi, I am trying to implement a robot controller using ros + gazebo - So, what I want it to tell gazebo a particular command and then gazebo should return the state after 1 second. And after that it ...
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Two nodes publish to one topic

There are two node publishing message to cmd_vel topic. One node is for self-driving, the other one is for teleoperation. How to set the teleoperation node has the high priority when publishing to ...
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timestamps for ros topics not updating smoothly

I noticed that the timestamps associated with my topics is not updating smoothly. It will go for several messages without changing (or changing by some very small amount), then change a lot all of a ...
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Getting list of published topics from within C++ code

I'm using the vicon_bridge node, which publishes a topic "vicon/<subject_name>/<segment_name>" for every subject and segment it finds. In this example, consider that it publishes ...
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How can I know the AR.Drone's height in order to control it?

I tried for getting the value of "altd" in /ardrone/navdata and what ever the position of the drone and even the state of drone like flying, landing, landed.. etc the "altd" value ...
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Rostopic Hz inaccurate?

Hello everyone. Sometimes when I measure the frequency of messages in a topic, the numbers printed don't make sense. For example: ...
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Using UWSim GPS

Hello, I am a beginner user of UWSim and I was trying to use the GPS sensor. I run "rosrun uwsim uwsim" and the scene with the robot in a tank loads up. I notice that there is a topic "/...
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Is this RPC communication?

i'm using ssh for ROS network communication. i setted ROS_IP, ROS_MASTER_URI up IP Address that is working roscore. i'm working roscore, roslisp_reql in local. and i'm working turtlesim_node in ssh. ...
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Nodes stop subscribing over time

I'm running ROS hydro on Ubuntu 12.04. I've written a simple python script that calculates the bandwidth though a network interface and then publishes as an Int16. So there's no data acquisition from ...
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Using data from a ROS node in a separate C++/Python program

Suppose there is a user-defined ROS node. I make it publish to a topic. Now i want to use this data published to the topic as input to a C++/Python program. So how do I make the node publish to a ...
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rostopic echo shows wrong format of message from arduino

So I made a custom message: odometry_message: Header header int32 encoder1 int32 encoder2 Then I compile in into arduino sketchbook (rosrun rosserial_arduino make_libraries .) I run a python serial ...
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How to roslaunch a rostopic echo to text file

I would like to do something like this from a launch file: rostopic echo -p /mytopic > outputfile.txt I wrote this in the launch file: ...
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ROS performace as number of topics increase

Hi, I am very curious about how the latency and the communication speed decreases as I increase the number of topics. If I have a package creating 20 topic for control. Is that a good idea? I can make ...
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How to use the keyboard teleop for programs written in C

I am trying to add keyboard support to some programs written in C++. How would I subscribe to that topic and listen for certain keys? Originally posted by bluejamesbond on ROS Answers with karma: 11 ...
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rosjava nodes isolated and ros tools buggy behavior

I'm trying to connect the android pubsub tutorial of android_core with a master core in my server. https://github.com/rosjava/android_core/tree/indigo/android_tutorial_pubsub I'm using ros indigo, ...
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Can rqt_graph visualize nodelets?

Hi all, I'm debugging a ROS application that intensively uses nodelets. However, I found that rqt_graph cannot visualize nodelets. Neither can other command line tools such as rostopic. I'm wondering ...
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rqt_plot for data in DignosticArray message

I have been trying (unsuccessfully) to plot /diagnostics/status[0]/values[0]/value (a stringified floating point number). Is such a topic string supported by rostopic or rqt_plot ? If so, how do I ...
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Check on a rostopic programatically?

I've tried searching for this but have been unsuccessful so far. Is it possible to see a topic's value, programatically? Basically, I need the functionality of rostopic echo, but I need to add it to ...
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Topic not subscribed to properly

I'm writing a new node and am following examples on how to do that in python. This node subscribes to a topic being published from another node (this other node's published topic is being published ...
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rostopic pub multiarray

Quick question, how do I publish a multiarray? I use rostopic a lot, and its tremendously helpful. One thing I was never able to figure out, was how publish a multiarray(I also wasn't able to find a ...
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Read hector quadrotor position and control its yaw angles

Hi I am running hector quadrotor demo with two spawn quadrotors and get two questions: How to read quadrotor's position? I asked it to show topics "/uav/uav1/fix" and it was supposed to ...
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rqt_graph colors and arrows

What is the color code for rqt_graph? And do the bi-directional arrows mean a service between two nodes or just that the node subscribes to AND publishes to the other node or both? Is there some sort ...
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rostopic pub python syntax error

Hi All, I need to use the rostopic pub command in phyton shell script: In c++ the command is: rostopic pub -r 5 /uav1/sug_cmd_vel geometry_msgs/Twist -- '[0.0, 0.2, 0.0]' '[0.0, 0.0, 0.0]' In python I ...
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Is current value of a Topic obtainable if data is not changing?

I'm fairly new to ROS, so forgive me if this is a dumb question. One of my Topics holds some initialization data that never really changes after several seconds of my node running. I noticed that when ...
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2 answers
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How to get the number of subscribers on a topic?

Hi everybody! I want to know the list (or number) of subscribers on a topic programmatically. I know that I can use the rostopic list but I need that information in my node. Thanks! Edit: There is a ...
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Controlling transitions between states in SMACH

Hello, i started working with SMACH few days ago and I was wondering how I could control the transition between my states from external events. For example a transition would be triggered by the event ...
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Why can't I send "123" via rostopic pub?

Hey I'm using an std_msgs/String topic to send some messages between nodes. During testing, I tried to send the string "123" via rostopic pub: rostopic pub /topic_name std_msgs/String "...
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read topic without callback

Is there a way to read the last message of a topic wihout using a callback? I mean, the tutorials teach to read a topic assigning a callback in a node, so that whenever a topic updates, the callback ...
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1 answer
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How to get topic list from ROSBridge?

I've beem unsing ROSBridge 2.0 to communicate with ros, and i'm trying to get the topic list using the following JSON message: { "op": "call_service", "service": "/...
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1 answer
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How to save topics in file?

I want to save these topics in file :/amcl/parameter_descriptions /amcl/parameter_updates what can i do? Originally posted by yasamin on ROS Answers with karma: 11 on 2014-05-14 Post score: 0
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brics_actuator.msg only works with rostopic

Hello, I'm fairly new to ROS and the youBot. I'm trying to move Joint 1 of the arm. A notebook is connected via ssh to the youBot. When I use rostopic everything works as expected and the arm moves. ...
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How to read a value from a ros message?

Dear friends, I am new in ROS, I am usinig CMVISION package, and the tos topic which I need is " /blobs ", with type "cmvision/blobs" $ rosmsg show cmvision/Blob uint32 red uint32 ...
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ROS internals - topics storage and network comms?

I am currently working on a software framework to monitor the energy consumption of robots or any embedded device. I wanted to build my framework in a similar manner as ROS. At the moment, I have ...
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Navigation with Gmapping

Im using navigation with gmapping and wanted to know that if in the global_costmap_params.yaml the static map should be true or false? I have it with false and its working fine. the problem is that ...
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1 answer
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Ros topic published string cannot be captured

Dear my friends, Recently, I have encountered the following problem. I want my ros node to publish a string message if other node is sending request for this message and I want to differentiate each ...
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getting details of topics in a program(node)

Hi guys I want to get details about topics in a program(node) such as how many topic exists in ros or the list of topic's name or how many node that subscribes from a special topic.. I want to get ...
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How to import msgs/Encoder for python scripts

Hey, I'm quite new to ROS and trying to read some encoder data from my robot. The robot published its encoder data on a rostopic with type: msgs/Encoder. I would like to make a python script to ...
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argument remapping: how to find the argument name

Following the UnderstandingServicesParams Tutorial I create another turtle using $ rosservice type spawn| rossrv show I can control the turtle2 by publish a topic ...
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Create Topic using an existing library C++

I am taking part in a robotics project that is introducing ROS into its development. I have an existing library of classes that are used to pass information. My task is to integrate this library into ...
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Using rqt_plot, how to find the topic name?

in the rqt_plot part of understandingTopic toturial http://wiki.ros.org/ROS/Tutorials/UnderstandingTopics the topic is /turtle1/pose/x /turtle1/pose/y /turtle1/pose/theta but I can only find the ...
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ROS Answers SE migration: publish a char

hey community, im a ROS beginner, and my question is how can i publish a char manualy in a rostopic? i have published a string with rostopic pub -1 my_topic std_msgs/String x but the comand rostopic ...
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Python Multiprocessing to publish to multiple topics

I currently have a setup where I have about 10 shell scripts that listen to 10 different KNX addresses (using the shell command grouplisten) and publish their state to a ROS topic. These scripts can ...
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rostopic publish message to remote machine?

Hi folks, I'm trying to connect to ROS running on a remote machine. I can remotely echo the topics from the machine however I cannot publish anything. rostopic echo /odom works like a charm, ...
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Package for Generically Listening to Topics

Is there a way to get a list of topics while running a node. For example, if a new message is published, is there a way to programmatically get the topic name posted (equivalent to running rostopic ...
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check for active state of topic

Hi, I have 2 nodes, 1 publishing the topic, 1 subscribing to that topic. Current situation is that when I start the subscribing node, the values that will be read from the topic are initialized to 0. ...
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how to move Pioneer 3 AT with ROSARIA

Hello, I need some help. I am trying to move a P3 AT with Rosaria. I have installed ROS groovy on Ubuntu 12.04 First of all i am starting roscore at the base ...
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How does ROS Topic data transfer work with large data streams?

I am studying ROS and I have the following question. When a node wants to transfer a relatively big data stream, for example, an image, how many TCP/IP connections are created to do such a transfer. ...
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2 nodes publishing on same topic - merge?

Hello, I have a robot description (urdf file) where the joint state publisher is publishing for all the non-fixed joints a message. I have 4 such joints which are published on topic /joint_states. But ...
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