eProsima FIROS2

eProsima FIROS2 is an application that allows intercommunication between ROS2 and NGSIv2 protocol. Since FIROS2 is powered by eProsima Integration Service, it makes possible the creation of bidirectional communication bridges with customized routing, to map between input and output attributes, and perform data modification between ROS2 and NGSIv2 from FIWARE-Orion contextBroker.

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Table Of Contents

Installation

Configuration

Transformation, mapping and communication

Types and interfaces

Dynamic Types

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Installation of FIROS2

Before using FIROS2, it has to be installed along with the rest of ROS2 Crystal packages of your system. If you have followed the ROS2 installation manual, you only need to clone this repository on your ROS2 workspace.

NOTE: Only ROS2 Crystal is currently supported by FIROS2.

For cloning this project and update its submodules at the same time, don't forget to add the --recursive option.

In Linux, these are the steps:

    $ cd ~/ros2_ws/src/ros2/
    $ git clone --recursive https://github.com/eProsima/firos2
    $ cd ~/ros2_ws

In the case of Windows:

    > cd C:\dev\ros2\src\ros2
    > git clone --recursive https://github.com/eProsima/firos2

On windows you must compile cURL Library as a thirdpary submodule:

    > cd C:\dev\ros2\src\ros2\firos2\thirdparty\curl
    > buildconf.bat
    > cd winbuild
    > nmake /f Makefile.vc mode=dll VC=14
    > cd C:\dev\ros2

Once done, FIROS2 is compiled like any other ROS2 package.

For example:

    $ colcon build --cmake-args -DTHIRDPARTY=ON --packages-select firos

There are several examples to show the behavior under the examples folder.

FIROS2 configuration

FIROS2 offers different parameters that the user can configure. For setting-up a bridge, the user has to define a configuration file with the information about input and output protocols. There is a generic example on config.xml

In this template is it possible to set different bridges between topics and entities. FIROS2's bridges subscribe to a topic and update data of the related entity and subscribe to entities and publish data to the related topic. The parameters that have to be defined are (only shown a bridge section of the config.xml file):

<!-- Declares a custom bridge named 'bridge_ngsiv2' -->
<bridge name="bridge_ngsiv2">
    <!-- Path to the NGSIv2 library -->
    <library>/path/to/ngsiv2bridge.so</library>

    <reader name="sub_ngsiv2">
        <property>
            <name>id</name>
            <value>entity_idPattern</value>
        </property>
        <property>
            <name>host</name>
            <value>context_broker_host</value>
        </property>
        <property>
            <name>port</name>
            <value>context_broker_port</value>
        </property>
        <property> <!-- optional -->
            <name>type</name>
            <value>entity_type</value>
        </property>
        <property> <!-- optional, comma separated values -->
            <name>attrs</name>
            <value>attr1[,attr2...]</value>
        </property>
        <property> <!-- optional -->
            <name>expression</name>
            <value>condition_expression</value>
        </property>
        <property> <!-- optional, comma separated values -->
            <name>notif</name>
            <value>notif_attr1[,notif_attr2...]</value>
        </property>
        <property>
            <name>listener_host</name>
            <value>our_listener_host</value>
        </property>
        <property>
            <name>listener_port</name>
            <value>our_listener_port</value>
        </property>
        <property>
            <!-- optional. In KB, if not specified, 2KB -->
            <name>listener_buffer_size</name>
            <value>our_listener_buffer_size</value>
        </property>
        <property> <!-- optional -->
            <name>expiration</name>
            <value>subscription_expiration_time</value>
        </property>
        <property> <!-- optional -->
            <name>throttling</name>
            <value>subscription_throttling</value>
        </property>
        <property> <!-- optional -->
            <name>description</name>
            <value>subscription_description</value>
        </property>
    </reader>

    <writer name="pub_ngsiv2">
        <property>
            <name>host</name>
            <value>context_broker_host</value>
        </property>
        <property>
            <name>port</name>
            <value>context_broker_port</value>
        </property>
    </writer>
</bridge>

Transformation, mapping and communication

As said before, when a bridge is connecting two nodes with different protocols, the user has to provide a library with a function to transform and to map the attributes from one protocol to another. To make this step easier, there is an empty code template in templatelib.cpp.

This function will be compiled apart and loaded in FIROS2 at runtime.

In this way, the user can map attributes from the input to the output message and at the same time apply changes over the data. The serialization and deserialization functions are generated with provided tools, so the IDL files used are the only thing that the user has to put in the bridge.

FIROS2 provides a built-in NGSIv2 bridge library named libisbridgengsiv2lib.so that implements an ISBridgeNGSIv2 with NGSIv2Publisher and NGSIv2Subscriber that allows communicating RTPS and NGSIv2, implementing the interfaces ISBridge, ISWriter, and ISReader respectively.

You can, of course, implement and use your bridge libraries to define other behaviors.

You can learn more about Bridge Libraries and Transformation Libraries in the documentation of eProsima Integration Service.

Types and interfaces

For interaction with NGSIv2 entities exists an IDL file (and generated files). This IDL is named JsonNGSIv2.idl and contains a structure composed of two strings, entityId, and data.

On receiving messages from NGSIv2 protocol, it only fills the data field. In this case, it ignores the entityId field, and it's better to keep it empty. Integration Service will fill data with the complete JSON string sent to our listener by the contextBroker server (this is, the subscription result).

For sending messages to the contextBroker to update entities from changes received from RTPS subscriber, *JsonNGSIv2" must fill entityId with the entityId of the entity modified and data with a composed JSON containing the attributed to being updated.

The user must implement the interaction with the NGSIv2 entities in the transformation library.

In the example TIS_NGSIv2 the transformation library shows examples of both transformations using the described behavior.

You can create your IDL files to define the required behavior and management of the data. To get a deeper comprehension of the relation between ROS2 and Fast RTPS IDL definitions, you can see this article.

Dynamic Types

An example of integration with Dynamic Types can be found in the Dyn_TIS_NGSIv2 example. RobotExample executable uses static types (to show compatibility), but ROS2 publisher/subscriber uses DynamicTypes, as well as NGSIv2 that uses a dynamic version of the NGSIv2 JSON library. All Dynamic Types related files are under DynNGSIv2 folder, that generates an additional dynamic library to be used with dynamic types transformation libraries.