That's not the correct syntax for private parameters. Your example puts them
into the same namespace as the node, but not the private namespace.

You can find full details here:

http://www.ros.org/wiki/roslaunch/XML/param

For your code, it might look like:

<node pkg="something" ... >
  <param name="port" value="/dev/ttyUSB0" />
</node>

On Wed, Jul 14, 2010 at 12:41 PM, Mike Purvis <mpurvis@clearpathrobotics.com
> wrote:

> Hi everyone,
>
> My current launch file structure is like so:
>
> <launch>
>   <env name="PYTHONPATH" value="$(env PYTHONPATH)" />
>   <group ns="clearpath/robots/$(optenv ID default)" clear_params="true">
>     <param name="port" value="$(optenv CPR_SERIAL_PORT /dev/ttyUSB0)" />
>     <param name="turn_radius" value="0.4" />
>
>     ...
>
>     <node pkg="clearpath_horizon" type="horizon.py" name="$(anon horizon)"
> output="screen" />
>     <node pkg="clearpath_2dnav" type="simple.py" name="$(anon nav)"
> output="screen" />
>     ....
>   </group>
> </launch>
>
> And then inside of horizon.py, I am able to access the parameter
> with rospy.get_param('port'). However, that parameter is really not relevant
> to any node except horizon.py. From my reading of the documentation, I
> should be able to make it private by putting the <param> tag inside the
> relevant node tag, and then calling it with rospy.get_param('~port').
> However, this doesn't seem to work---I consistently just get the default
> parameter.
>
> What am I doing wrong?
>
> Thanks.
>
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