I have some Pioneer 3dx robots and they are equipped with sonar, compass, gyro, odometry and bumpers.  I need to get (store) readings from each of the devices.  I'm writting the code in C and I've used the limited examples for doing so with C ( http://playerstage.sourceforge.net/doc/Player-2.0.0/player/group__libplayerc__example.html).  Nevertheless, I'm still not sure how to properly use the libraries to get the data.  So could someone tell me how/when/why/where to use the playerc_ device_get_geom() functions (device = sonar, position2d, etc.).