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How can I sync massages from two different topics?

asked 2017-02-22 21:36:05 -0500

rose1360 gravatar image

Hi, I am working with Baxter robot and I am trying to synchronize robot_joints which is running in first terminal,and endpoint_state which is running in the second terminal. In other word, I want to see in special end-effector position, what are the relevant joints angles. I can see them separately in two terminals but I dont know how can I see all of them synced together?

Thanks, Rose

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answered 2017-02-23 04:58:44 -0500

TTDM gravatar image

updated 2017-02-23 05:03:58 -0500

One solution is to create a node which read both messages and use message filter to extract simultanious messages or at least message with close time stamps ( depending on your filtering options ).

You can then simply use the node to print thoses 2 messages next to each others.

As a personnal note I must say that despite this solution being what should be use to solve your issue, i had troubles using it because it dropped way too many messages. At least one of my collegues told me that he doesn't think highly of this feature too. Depending on the reactions about this note in the comments, i might erase it. Also, by chance, if someone had a dropped message issue ( even with the approximate time option ) and managed to solve it, I can instead add his comments to this answer.

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I think the note about the msg filters is fair: it's not a magic solution, and will depend on the time sources and how you use them in your publishers. It basically just looks at the timestamps and if two timestamps match (according to the configured policy) it passes on the msgs.

gvdhoorn gravatar imagegvdhoorn ( 2017-02-23 05:36:02 -0500 )edit

Have you tried experimenting with the buffer length (ie: queue_size)?

gvdhoorn gravatar imagegvdhoorn ( 2017-02-23 05:39:33 -0500 )edit

I did but I couldn't reach satisfactory results. Anyway,it was just a refinment for me and I finally ignore this synchronisation matter.

TTDM gravatar imageTTDM ( 2017-02-23 06:13:07 -0500 )edit

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Asked: 2017-02-22 21:36:05 -0500

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Last updated: Feb 23 '17