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Messages, services and actions generator

Autogeneration tools []

For the autogeneration of model objects we facilitate a bash:

source /your_ROS_workspace
wget https://raw.githubusercontent.com/ipa320/RosCommonObjects/main/de.fraunhofer.ipa.ros.communication.objects/basic_msgs/generate_messages_model_helper.sh
chmod +x generate_messages_model_helper.sh
./generate_messages_model_helper.sh ROS_PACKAGE_NAME > ROS_PACKAGE_NAME.ros

The file generated, independently of the method, will have a .ros extension and can be copied to the folder "basic_msgs" of the "de.fraunhofer.ipa.ros.communication.objects" project, please send us a pull request to our repository with your models to include them to the base dictionary automatically. Alternatively, for cases where the messages types are specific for a concrete component (like the ur_msgs for ur_driver or messages types defined within the same repository that the node). We recommended following the same approach that ROS does, define the communication object models together with the node description, for our tooling that means copying the file to the project that will be created on the next step for your node description.

The autogenerator script doesn't support actions.

ROS communication objects model language grammar

To modify the ROS models (.ros) manually the ROS tooling provides a customized editor which should be the default option to open the .ros extension files, otherwise, it can be selected manually by a right click on the MyFile.ros file and choosing "Open with.."* and "ROS Editor").

This editor contains an autocomplete function (by pressing Ctrl+Space) and will report any error made by editing. The first step is to define a PackageSet (that corresponds to a metapackage for ROS, this definition is optional and its name can be kept empty). Then, the ROS package which contains the msgs has to be defined and within it, the option "spec" has to be selected to write down the objects. In practice, that means that the initial *.ros file that describes ROS objects looks:

ros_package_name:
  msgs:
    msg_name
      message
        type name

The grammar supports 3 types of communication objects messages, services and actions, and consequentially each of these 3 types supports different specifications types:

  • ROS msgs
ros_package_name:
  **msgs:**
    msg_name
      **message**
        ElementType ElementName

For example:

std_msgs:
  msgs:
    ColorRGBA
      message
        float32 r
        float32 g
        float32 b
        float32 a
  • ROS srvs
ros_package_name:
  **srvs:**
    srv_name
      **request**
        ElementType ElementName
      **response**
        ElementType ElementName

For example:

std_srvs:
  srvs:
    SetBool
      request
        bool data
      response
        bool success
        string message
  • ROS actions
ros_package_name:
  **actions:**
    action_name
      **goal**
        ElementType ElementName
      **result**
        ElementType ElementName
      **feedback**
        ElementType ElementName

For example:

control_msgs:
  actions:
    PointHead
      goal
        'geometry_msgs/msg/PointStamped'[] target
        'geometry_msgs/msg/Vector3'[] pointing_axis
        string pointing_frame
        'builtin_interfaces/msg/Duration'[] min_duration
        float64 max_velocity
      result
      feedback
        float64 pointing_angle_error

Where, quite similar to ROS, the allowed element types are:

  • Primitives:

    • bool
    • int8
    • uint8
    • int16
    • uint16
    • int32
    • uint32
    • int64
    • uint64
    • float32
    • float64
    • string
    • time
    • Header

  • Relative reference to another object:

    • NameOftheObject (if it is described within the same ROS package) -> for example Point32
    • 'ROSPackage_name/NameOftheObject' (if it is described in another ROS package) -> for example 'geometry_msgs/Point32'

  • Arrays of element types:

    • ElementType[] -> for example string[] or Point32[] or 'geometry_msgs/Point32'[]

Additionally, the definition of constants with their value is also supported and follows a pattern very similar to the ROS one: constanttype1 CONSTANTNAME1=constantvalue1, for example, byte OK=0 byte WARN=1 byte ERROR=2 byte STALE=3.

The following extract shows the ROS model description correspondent to the nav_msgs package:

nav_msgs:
  msgs:
    Path
      message
        'std_msgs/msg/Header'[] header
        'geometry_msgs/msg/PoseStamped'[] poses
    OccupancyGrid
      message
        'std_msgs/msg/Header'[] header
        'nav_msgs/msg/MapMetaData'[] info
        int8[] data
    Odometry
      message
        'std_msgs/msg/Header'[] header
        string child_frame_id
        'geometry_msgs/msg/PoseWithCovariance'[] pose
        'geometry_msgs/msg/TwistWithCovariance'[] twist
    GridCells
      message
        'std_msgs/msg/Header'[] header
        float32 cell_width
        float32 cell_height
        'geometry_msgs/msg/Point'[] cells
    MapMetaData
      message
        'builtin_interfaces/msg/Time'[] map_load_time
        float32 resolution
        uint32 width
        uint32 height
        'geometry_msgs/msg/Pose'[] origin
  srvs:
    SetMap
      request
        'nav_msgs/msg/OccupancyGrid'[] map
        'geometry_msgs/msg/PoseWithCovarianceStamped'[] initial_pose
      response
        bool success
    LoadMap
      request
        string map_url
      response
        'nav_msgs/msg/OccupancyGrid'[] map
        uint8 result
    GetPlan
      request
        'geometry_msgs/msg/PoseStamped'[] start
        'geometry_msgs/msg/PoseStamped'[] goal
        float32 tolerance
      response
        'nav_msgs/msg/Path'[] plan
    GetMap
      request
      response
        'nav_msgs/msg/OccupancyGrid'[] map

Known-issues

This model doesn't allow the creation of 2 specifications with the same name, although they have different types. That means a ROS model like the following one is not allowed:

my_msgs:
  msgs:
   hello:
    message
     String data 
  srvs:
   hello
     request
     response
      String data

The reason is that when one of these objects has to be referenced during the definition of a node it will be impossible for the model to distinguish which is the correct one (both are defined as my_msgs/Hello and within the dame model file). For these cases, we recommend splitting the objects into two different model files.

The repository RosCommonObjects holds further examples.