Topic and Messages Clause Samples

Topic and Messages. ‌ Topics are data information that are exchanged between nodes. The former, are characterized by a topic name and an associated type. micro-ROS topics are defined similarly to the ROS2 ones, using rosidl files. These topic definition files need to be processed to generate code supporting the type they define. From rosidl files, the build system generates type support consisting of the in-memory representation of the topic type. In addition to the in-memory representation, the topic needs code supporting middleware required to serialise/deserialise operations. The code generation is provided rosidl files as input and produces middleware vendor-specific type support code as an output. This way, this type of support generation is a process tied to the underlying middleware vendor. As for micro-ROS, the latter generates DDS-XRCE static type support. The rosidl types pool is being expanded to include ever more IDL types with the objective to support the complete OMG IDL 4.2 specification in the future. A complete subset of the desired features from IDL 4.2 specification that ROS2 will include in upcoming releases can be found here. micro-ROS has been aligning and will keep doing so with the set of IDL types supported by ROS 2.