Dynamic reconfigure default parameters

asked 2012-02-23 09:01:43 -0600

Ivan Dryanovski

4954 ●52 ●70 ●86 http://robotics.ccny.cuny.edu/

updated 2013-04-05 01:42:17 -0600

Philip

990 ●8 ●11 ●28 http://www.kit.edu/

I am writing a node which accepts certain parameters. I would like to be able to pass them through a launch file, as well as make them dynamically reconfigurable.

What are the best practices regarding this? In particular:

What happens if the value in the launch file is not the same as the default value in the .cfg file?
Does it matter whether I register the dynamic reconfigure services before or after getting the parameters from the nodehandle using getParam()?

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Doesn't dynamic_reconfigure initialize the values from the param server automatically?

dornhege ( 2012-02-23 09:18:36 -0600 )edit

It would, but in configurations with "use_sim_time" and "rosbag play foo.bag --clock --pause" and then stepping through the bag file for debugging you potentially run into problems because no spinning seems to take place on sim_time, so no ros::spin()-based callbacks are called.

Crusty ( 2014-04-14 02:40:50 -0600 )edit

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answered 2012-02-23 09:37:10 -0600

Patrick Mihelich
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You should already get the desired behavior for free. When you create the dynamic_reconfigure server in your node, it initializes the configuration in these steps:

Load default values as defined in the .cfg.
Query parameter server for each parameter, overwriting the default value if it's set.
Clamp all parameters to the ranges defined in the .cfg.

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You're right! Unfortunately the ROSNodeTutorialC++ (http://wiki.ros.org/ROSNodeTutorialC%2B%2B) is misleading: It reads the parameters "a", "b" and "message" explicitly from the parameter server even though they are included in the dynamic reconfigure callback...

PiotrOrzechowski ( 2014-01-21 05:33:34 -0600 )edit

That tutorial may very well be in error. Please open a separate question explaining the problem, so we can get it resolved, as explained in the note at the top of each tutorial page.

joq ( 2014-01-21 06:13:43 -0600 )edit

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answered 2012-02-23 09:33:03 -0600

joq
25443 ●181 ●256 ●408

updated 2012-02-23 09:33:57 -0600

Dynamic reconfiguration works fine for your use case.

When you register your callback, it gets invoked immediately with the values currently defined in the parameter server and a level of 0xffffffff. Those initial values will include anything set in your launch file. You don't need to read the parameters yourself using getParam().

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