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ROS publish/subscribe queues

We have two nodes in our system where one node publishes frames from the inbuilt camera and the other processing node takes the image and shows it using imshow in opencv. The messages are essentially...

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Rosbridgelb: Received a message without op

I'm using ROSBridgelb to publish "OccupancyGrid Message" from Unity to ROS. However I'm always getting the "Received a message without op" error. I made sure that there is no problem with all brackets,...

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PYTHON + ROS + V-REP

Hi I have got a problem with publish data. I want to publish msg.linear.x and msg.linear.y to V-REP via ROS. When I write in terminal rostopic pub -1 /cmd_vel geometry_msgs/Twist '{linear: {x: -3.0, y:...

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Are ROS2 messages guaranteed to be received by a Subscriber in the same order...

According to https://github.com/ros2/ros2/wiki/About-Quality-of-Service-Settings it's possible to vary the QoS settings of History, Depth, Reliability and Durability. However, I can't find any mention...

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Return a value from a callback function

Hello ! I want to have a value to be returned when I call a callback function while subscribing to a topic. I am using ROS-Hydro I have wrote a demo code that what I want. Please also suggest some new...

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Not able to echo topics published on separate computer with rosmaster

Hello, rostopic echo /turtle1/cmd_vel on my slave computer outputs nothing after using rostopic pub -r 1 /turtle1/cmd_vel geometry_msgs/Twist -- '[2.0 ,0.0, 0.0]' '[0.0, 0.0, 1.8]' on my master over...

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ros_tutorials roscpp talker/listener loses first message or two

This must've been seen before...I ran into it while trying to track down a lost message from a command-line app which publishes one message then exits. I'm running ros kinetic on Ubuntu 16.04.4. My...

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Accessing previous estimated joint states of a robot

Hi, I am new to ROS and I am trying to implement a Kalman filter for estimating the joints velocity and acceleration of a robotic manipulator. The angular position of each joint is published to the...

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Time performance was dropped by transmission period.

Hello, guys. I have used ROS Kinetic on ubuntu 16.04. I make a two node. The one is publisher node to publish image topic. Another is subscriber node to subscribe publisher's topic. The transmission...

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Daisy-chained motors' publish rate is slow: dynamixel_workbench

I am running ROS kinetic on Ubuntu 16.04.3 LTS (and kernal name 4.13.0-32-generic). I am working with the dynamixel_workbench stack. Specifically, I have a MX-106, an MX-64, and another MX-64...

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Reducing the publishing rate of a topic from RosLaunch

Hi there, I have a custom-built robot which I am trying to control with move_it. I have written the urdf and generated the srdf using the move_it setup assistant. All the topics from my URDF are being...

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ROS Serialization Values Error

Hi there, I am trying to do a simple ipc over ros serial using the publish subscribe module. The data is a 2D array shaped thus: `10001 x 7`. I write my poublisher like so import rospy from...

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hz of our sensor's the topic was DECREASED, When I record some data with rosbag.

Hello, experts. I used rosbag to acquire our sensor data as camera, lidar. You can reference below spec. Camera Node : 1980x1208 (FHD, RGB), 20 hz Lidar Node : 64 Channel, 20 hz I recorded topics on pc...

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"wrong checksum for id and message" when using interrupts to read ultrasonic...

I am using interrupts to read from ultrasonic sensors on a Teensy 3.5 board. When I publish data I get a stream of "wrong checksum for topic id and message" warnings. I will also occasionally get...

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How to use publish and use multiple sonar range_msg data (using rosserial) on...

Hi, I am learning ROS by developing a differential drive collision avoidance robot. (Specifically the Parallax ARLO Robot). I have written a code that can publish one ping sensor's range value to a...

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check if topic is being published to without subscribing

In our project we want to write a node to check sensor nodes for possible errors. One of the checked criterion is, if the topics of the node are actually published and not just have publisher. **Is it...

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How to publish a ROS2 message in a Linux Terminal

In ROS1, when publishing a message in a terminal (such as in [this question](https://answers.ros.org/question/218818/how-to-publish-a-ros-msg-on-linux-terminal/)) when typing rostopic pub -r 10...

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Tutorial for Image Publisher/Subscriber in Python (Video Stream)

Is there any tutorial or code for image publisher/subscriber in Python?...

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what if computation complexity cannot meet the demand of callback frequency

According to the totorials, the callback function frequency is dependent on the its subscribing topic frequency. What will happen if the callback function is very complex and the computation time is...

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