Add custom ros message to micro_ros_espidf_component help

[adam-at-epsilon]

Hi, my project uses micro_ros_espidf_component which works fine with standard int32 messages, but we would like to use a custom message. To be fair I am not an expert in either cmake build system or esp-idf framework.

Our project looks like this:

- ourProject/
             - CMakeLists.txt
             - sdkconfig
             - components/
                           -  micro_ros_espidf_component // copy of repo, revision jazzy
             - main/       
                           - CMakeLists.txt
                           - main.c
                           - idf_component.yml // micro_ros_espidf_component listed as repo dependency
             - build/

As far as my troubleshooting goes, my attempts to add a components/msgs subdirectory have failed and I have since realised that the custom message(s) need to be part of the micro_ros_espidf_component itself so they are compiled into libmicroros.a.

• My approach is to copy micro_ros_espidf_component into a new components directory. Then main/idf_component.yml lists this as a local directory dependency rather than previously a repo dependency
• the msgs components are not part of micro_ros_espidf_component instead micro_ros_espidf_component/libmicroros.mk does git clone https://github.com/micro-ROS/micro_ros_msgs.
  • THE BIG QUESTION What do I need to do here to add a custom message directory which is then picked up and compiled into libmicroros.a?
  • Ideally I would like to add a MyCustomMessage in a myrepo/components/msgs/MyCustomMessage.msg file along the pattern of this video

Any help is appreciated.

[adam-at-epsilon]

the solution I came up with was to hack into libmicroros.mk. This route was chosen as ESP-IDF cmake modules did not have the ament_cmake module necessary to generate .c and .h files from my CustomMessage.msg file.

So libmicroros.mk gets a new line after line 62 which git clones the ros_msgs repo like this:

cp -Rf ../my_custom_interfaces src/custom_interfaces

The project structure now looks like this:

- ourProject/
             - CMakeLists.txt
             - sdkconfig
             - components/
                           -  micro_ros_espidf_component // copy of repo, revision jazzy
                                   - libmicroros.mk // add line which cp -R copies my_custom_interface 
                                                    // like the git clone lines do with ros_msgs
                           - my_custom_interface
                                  - CMakeLists.txt
                                  - package.xml
                                  - msg/
                                          - CustomMessage.msg
             - main/
                           - CMakeLists.txt
                           - main.c
                           - idf_component.yml // micro_ros_espidf_component listed as local path dependency
             - build/

This creates .h and .c files correctly so they can be included in main.c file.

Maybe there is a prettier way to do it, for instance with the extra_packages directory but this works.

[peclatj]

Hi, I had the same question and I just succeded with the extra_packages directory

I followed the instruction here.
https://micro.ros.org/docs/tutorials/advanced/create_new_type/

I create the custom package in my ros2_ws as I would do for any other ROS2 package then I created a simlink from
micro_ros_espidf_component/extra_packages/my_custom_message -> ~/ros2_ws/src/my_custom_message

So from ~/ros2_ws/src

ros2 pkg create --build-type ament_cmake my_custom_message
cd my_custom_message
mkdir msg
touch msg/MyCustomMessage.msg

From micro_ros_espidf_component/extra_packages
Create the simlink with ln -s ~/ros2_ws/src/my_custom_message

add to the CMakeLists.txt

...
find_package(rosidl_default_generators REQUIRED)

rosidl_generate_interfaces(${PROJECT_NAME}
  "msg/MyCustomMessage.msg"
 )
...

and to package.xml

...
<build_depend>rosidl_default_generators</build_depend>
<exec_depend>rosidl_default_runtime</exec_depend>
<member_of_group>rosidl_interface_packages</member_of_group>
...

Add whatever you want in the message and

 idf.py clean-microros
 idf.py build