ros_control: example RobotHW using RobotTransmissions

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Can someone point me to a good (full) example of a RobotHW subclass that uses TransmissionInterfaceLoader/RobotTransmissions to load transmission information from the URDF and read/write transformed data to/from some lower level hardware? I'm trying to reconcile these examples:

1. http://docs.ros.org/kinetic/api/trans... 2. http://docs.ros.org/kinetic/api/trans...

I'm getting hung up on what data structures store the pos/vel/effort data for read/write, and whether my class needs to set them up, or they're already present in RobotTransmissions.

Thanks!