Add a custom ROS message

Overview

During the Autoware development, you will probably need to define your own messages. Read the following instructions before adding a custom message.

1. Message in autoware_msgs define interfaces of Autoware Core.

   • If a contributor wishes to make changes or add new messages to autoware_msgs, they should first create a new discussion post under the Design category.

2. Any other minor or proposal messages used for internal communication within a component(such as planning) should be defined in another repository.

   • tier4_autoware_msgs is an example of that.

The following is a simple tutorial of adding a message package to autoware_msgs. For the general ROS2 tutorial, see Create custom msg and srv files.

How to create custom message

Make sure you are in the Autoware workspace, and then run the following command to create a new package. As an example, let's create a package to define sensor messages.

1. Create a package

   cd ./src/core/autoware_msgs
   ros2 pkg create --build-type ament_cmake autoware_sensing_msgs
   

2. Create custom messages

   You should create .msg files and place them in the msg directory.

   NOTE: The initial letters of the .msg and .srv files must be capitalized.

   As an example, let's make .msg files GnssInsOrientation.msg and GnssInsOrientationStamped.msg to define GNSS/INS orientation messages:

   mkdir msg
   cd msg
   touch GnssInsOrientation.msg
   touch GnssInsOrientationStamped.msg
   

   Edit GnssInsOrientation.msg with your editor to be the following content:

   geometry_msgs/Quaternion orientation
   float32 rmse_rotation_x
   float32 rmse_rotation_y
   float32 rmse_rotation_z
   

   In this case, the custom message uses a message from another message package geometry_msgs/Quaternion.

   Edit GnssInsOrientationStamped.msg with your editor to be the following content:

   std_msgs/Header header
   GnssInsOrientation orientation
   

   In this case, the custom message uses a message from another message package std_msgs/Header.

3. Edit CMakeLists.txt

   In order to use this custom message in C++ or Python languages, we need to add the following lines to CMakeList.txt:

   rosidl_generate_interfaces(${PROJECT_NAME}
     "msg/GnssInsOrientation.msg"
     "msg/GnssInsOrientationStamped.msg"
     DEPENDENCIES
       geometry_msgs
       std_msgs
     ADD_LINTER_TESTS
   )
   

   The ament_cmake_auto tool is very useful and is more widely used in Autoware, so we recommend using ament_cmake_auto instead of ament_cmake.

   We need to replace

   find_package(ament_cmake REQUIRED)
   
   ament_package()
   

   with

   find_package(ament_cmake_auto REQUIRED)
   
   ament_auto_package()
   

4. Edit package.xml

   We need to declare relevant dependencies in package.xml. For the above example we need to add the following content:

   <buildtool_depend>rosidl_default_generators</buildtool_depend>
   
   <exec_depend>rosidl_default_runtime</exec_depend>
   
   <depend>geometry_msgs</depend>
   <depend>std_msgs</depend>
   
   <member_of_group>rosidl_interface_packages</member_of_group>
   

   We need to replace <buildtool_depend>ament_cmake</buildtool_depend> with <buildtool_depend>ament_cmake_auto</buildtool_depend> in the package.xml file.

5. Build the custom message package

   You can build the package in the root of your workspace, for example by running the following command:

   colcon build --packages-select autoware_sensing_msgs
   

   Now the GnssInsOrientationStamped message will be discoverable by other packages in Autoware.

How to use custom messages in Autoware

You can use the custom messages in Autoware by following these steps:

• Add dependency in package.xml.
  • For example, <depend>autoware_sensing_msgs</depend>.
• Include the .hpp file of the relevant message in the code.
  • For example, #include <autoware_sensing_msgs/msg/gnss_ins_orientation_stamped.hpp>.