Inputs and Outputs

Inputs and Outputs#

Components in Kompass are defined to accept only restricted types of inputs/outputs to help lock the functionality of a specific Component implementation. Each input/output is associated with a unique keyword name and is set to accept one or many of ROS2 message types. Additionally, the input/output keyword in the Component can define a category of Topics rather than a single one. To see an example of this check the DriveManager Component. In this component the input sensor_data defines any proximity sensor input (LiDAR, Radar, etc.) and can optionally take up to 10 Topics of such types to fuse it internally during execution.

Configuring an input/output of a Component is very straightforward and can be done in one line in your Python script. Below is an example for configuring the previously mentioned DriveManager:

    from kompass.components import DriveManager
    from kompass.topic import Topic

    driver = DriveManager(component_name="driver")

    # Configure an input
    driver.inputs(sensor_data=[Topic(name='/scan', msg_type='LaserScan'),
                               Topics(name='radar_data', msg_type='Float64')])

    # Configure an output
    driver.outputs(emergency_stop=Topic(name='alarm', msg_type='Bool'))

Configure inputs/outputs for your custom component#

Internally in the component, Inputs/Outputs are attrs classes with the attribute name representing a unique input/output key name and the value equal to the Topic. Each component is created with default inputs and default outputs and restricted with AllowedInputs and AllowedOutputs classes. Custom inputs/outputs classes can be created using create_topics_config method which returns an attrs class where each keyword argument corresponds to a class attribute of type Topic, as shown in the example below:

    from kompass.topic import Topic, create_topics_config
    from kompass.components.component import Component

    # Create the Topics class
    NewTopicsClass = create_topics_config(
                        "MyInputsClass",
                        input_1=Topic(name="/plan", msg_type="Path"),
                        input_2=Topic(name="/location", msg_type="Odometry"),
                    )
    # Get an instance
    inputs = NewTopicsClass()

    # Set as the component inputs
    my_component = Component(component_name='my_component', inputs=inputs)

To restrict your custom component to accept only specific types of inputs/outputs, you can create your your allowed inputs and/or allowed outputs using RestrictedTopicsConfig enum class. Add an enum value of type AllowedTopic for each category of topics and set the key name, allowed ROS2 message types and optionally the number of required and additional optional streams.

Tip

If the number of required and optional streams is not specified for an AllowedTopic, then the only one stream is required with no additional optional streams (default: number_required=1, number_optional=0)

    from kompass.topic import AllowedTopic, RestrictedTopicsConfig
    from kompass.components.component import Component

    # Set the allowed inputs
    class AllowedInputs(RestrictedTopicsConfig):
        PLAN = AllowedTopic(key="input_1", types=["Path"])
        LOCATION = AllowedTopic(key="input_2", types=["Odometry", "PoseStamped", "Pose"], number_required=1,
        number_optional=3)

    # Create the Topics class
    NewTopicsClass = create_topics_config(
                        "MyInputsClass",
                        input_1=Topic(name="/plan", msg_type="Path"),
                        input_2=Topic(name="/location", msg_type="Odometry"),
                    )

    # Get an instance for the default inputs
    inputs = NewTopicsClass()

    # Can change input_2 since it takes other allowed types and upto 3 optional inputs
    inputs.input_2 = [Topic(name="/odom", msg_type="Odometry"), Topic(name="/pose_stamped", msg_type="PoseStamped")]

    my_component = Component(component_name='my_node', inputs=inputs, allowed_inputs=AllowedInputs)
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