Design

The driver node is written modular and extendable as shown in the following simplified UML class diagram:

The Node manager class implements the rclcpp::Node interface and contains a list of Converter instances and an instance of the Driver class. The Driver class is responsible to set up a thread via an IoContext instance to receive data asynchronously. It also provides a Sender interface to send sensor PDUs. The Driver class will check received PDUs, deserialize them and dispatch the resulting PDU structures to a list of Receiver instances.

For receiving and sending UDP data the Driver class uses an instance of the UdpSocket class which handles sending and receiving bytes over the wire. The UdpSocket class is based on the ASIO library and uses an udp::socket instance.

On the sending side, the Driver class implements a Sender interface, which allows any user of that interface to send PDUs to the sensor. The Driver will serialize PDU input structures and send the byte stream via the UdpSocket instance. The Node class forwards the Sender interface and a weak reference to its rclcpp::Node interface to all of its Converter instances.

Each Converter implements the Receiver interface, such that the Node class can register each Converter as Receiver in the Driver instance.

In conclusion, the list of Converter instances passed to the Node can receive PDUs through the Receiver interface, called by the receiving thread in the IoContext and can send PDUs through the Sender interface to the Driver in the main thread.

Thus, the list of Converter instances is a plugin list, which can be extended by subsequent packages.

The implemented DefaultConstructor maps the received PDU structures into ROS messages through publishers and on the other hand fills PDU structures from a ROS message subscription / service and sends them via the Sender to the sensor. Furthermore, it implements diagnosis for all subscribed and published topics if they are expected to transmit data cyclically.