[ros-users] error: cannot load message class. Are you messages built?

[Ken Conley]

This message usually occurs when rostopic cannot load
ardusim/src/ardusim/msg/_TPA.py, which it needs to deserialize the
messages it echos. The rest of the tests with type/show/etc... don't
need the .py file, which is why they don't error.  I would attempt to
rebuild the ardusim package and check for errors. I would also make
sure that ardusim is on your ROS_PACKAGE_PATH.

 - Ken

2010/8/12 Gonçalo Cabrita <goncabrita at gmail.com>:
> Hi guys!
>
> I have made an ROS node for reading sensors connected to an arduino. Along with the node I created some ROS msgs for the sensors. I compiled and tested everything on my MacBook running Ubuntu 10.04 with cturtle, however, when I copy the node to the robots (Eee PC also with Ubuntu 10.04 with boxturtle) I run into some problems.
>
> Everything compiles fine, and the node runs just fine, however I cannot rostopic echo my custom msgs! It gives me this error:
>
> error: cannot load message class for [ardusim/TPA]. Are you messages built?
>
> The topics show up on rostopic list. I can run rostopic type and rosmsg show. I've also tried roswtf but everything seems fine.
>
> What am I missing here? Could it have something to do with having cturtle on one computer and boxturtle on the other? The node was created on the MacBook with boxturtle previous to the cturtle update.
>
> Thanks for the help,
>
> Gonçalo Cabrita
> ISR - University of Coimbra
> Portugal
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