best way to create a topic

asked 2013-08-14 03:00:26 -0600

hvn
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Hi,

I have 2 nodes that need 1-way communication of an array of floating point values, so I want node 1 to publish to a topic (e.g. ref), and node 2 to subscribe to that topic. I've searched on how to create a node with topic, but the tutorial only shows a message topic. Now I've tried 2 approaches: using a yaml file and using a launch file according to working examples, but so far neither creates a new topic. So the question is: how do I best create a new topic for 2 existing nodes ?

Thanks

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answered 2013-08-14 04:02:51 -0600

thebyohazard
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updated 2013-08-15 02:37:18 -0600

felix k

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I'm not sure you understand the concept of topics and messages quite correctly. It might help you to go through the main tutorials again, in particular UnderstandingTopics and WritingPublisherSubscriber(c++).

Messages are always broadcast on topics. To create a topic, one node needs to advertise that they will broadcast messages on that topic. Then another node subscribes to that topic and receives all messages broadcast on that topic.

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Further, the message type that you are likely interested in using will be one of the multiarray datatypes in the http://www.ros.org/wiki/std_msgs/

SL Remy ( 2013-08-15 06:40:20 -0600 )edit

TY @tbh and @trinighost. I did understand but just a minor misconception. The multiarray type did the trick.

hvn ( 2013-08-15 08:23:01 -0600 )edit

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answered 2013-08-14 03:49:23 -0600

dornhege

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I think you got something confused, but I don't know what. The publisher and subscriber tutorials describe exactly the use case that you want.

yaml or launch files are not needed, just the two nodes.

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answered 2018-08-15 06:24:00 -0600

ameni
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HI, I'm using a roboteq magsensor, and I want to read data from.

so I'm going to use Roboteq Linux API to interface one the sensor form a C++ ROS node through CANbus . The problem is I didn't come to know how to work: it's only one node that's gonna read from the sensor , how to use topic in this situation ?

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