Check out the following video explaining what micro-ROS is and why you need it!
Fast RTPS 1.9 is the default DDS implementation shipped with the Eloquent release so that Micro XRCE-DDS will be compatible with this new version. Micro XRCE-DDS brings the DDS world to microcontrollers without dynamic memory allocations and using ~2 KB of the stack.
Micro XRCE-DDS is the underlying protocol implementation used in the micro-ROS project. With this alignment and with further development to come following Eloquent release, mainly merging and adapting RMW implementation and examples to the new ROS core layers. micro-ROS will be compatible with Eloquent. This will grant the possibility to easily integrate your microcontroller with Eloquent applications and using the same look and feel. We are bringing the ROS 2 concepts to microcontrollers!