Create Shareable ROS 2 Custom Message Package

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In this example, you create a shareable ROS 2 custom message package in MATLAB. You must have a ROS 2 package that contains the required msg file. This figure shows an example of an appropriate folder structure.

ROS 2 Custom Messages Folder Structure

After you prepare your custom message package folder, you specify the path to the parent folder and call ros2genmsg with the specified path.

Open a new MATLAB session and create a custom message package folder in a local folder. Choose a short folder path when you generate custom messages on a Windows machine to avoid limitations on the number of characters in the folder path. For example,

genDir = fullfile('C:/test/ros2CustomMessages')

genDir = fullfile(pwd,'ros2CustomMessages');
packagePath = fullfile(genDir,'simple_msgs');
mkdir(packagePath)

Create a folder named msg inside the custom message package folder.

mkdir(packagePath,'msg')

Create a file named .msg inside the msg folder.

messageDefinition = {'int64 num'};

fileID = fopen(fullfile(packagePath,'msg', ...
               'Num.msg'),'w');
fprintf(fileID,'%s\n',messageDefinition{:});
fclose(fileID);

Create a folder named srv inside the custom message package folder.

mkdir(packagePath,'srv')

Create a file named .srv inside the srv folder.

serviceDefinition = {'int64 a'
                     'int64 b'
                     '---'
                     'int64 sum'};
 
fileID = fopen(fullfile(packagePath,'srv', ...
               'AddTwoInts.srv'),'w');
fprintf(fileID,'%s\n',serviceDefinition{:});
fclose(fileID);

Create a folder named action inside the custom message package folder.

mkdir(packagePath,'action')

Create a file named .action inside the action folder.

actionDefinition = {'int64 goal'
                    '---'
                    'int64 result'
                    '---'
                    'int64 feedback'};
 
fileID = fopen(fullfile(packagePath,'action', ...
               'Test.action'),'w');
fprintf(fileID,'%s\n',actionDefinition{:});
fclose(fileID);

Generate custom messages from ROS 2 definitions in .msg, .srv and .action files. Use the CreateShareableFile name-value argument to create a shareable ZIP archive of the generated custom messages.

For information about how to use use this ZIP archive to register the custom messages in another machine, see ros2RegisterMessages.

ros2genmsg(genDir,CreateShareableFile=true);

Identifying message files in folder 'C:/Users/echakrab/OneDrive - MathWorks/Documents/MATLAB/ExampleManager/echakrab.Bdoc23a.ROS2transform/ros-ex71849911/ros2CustomMessages'.Validating message files in folder 'C:/Users/echakrab/OneDrive - MathWorks/Documents/MATLAB/ExampleManager/echakrab.Bdoc23a.ROS2transform/ros-ex71849911/ros2CustomMessages'.Done.
Creating a Python virtual environment.Done.
Adding required Python packages to virtual environment.Done.
Copying include folders.Done.
Copying libraries.Done.
Done.
[1/1] Generating MATLAB interfaces for custom message packages... Done.
Running colcon build in folder 'C:/Users/echakrab/OneDrive - MathWorks/Documents/MATLAB/ExampleManager/echakrab.Bdoc23a.ROS2transform/ros-ex71849911/ros2CustomMessages/matlab_msg_gen/win64'.
Build in progress. This may take several minutes...

Verify creation of the new custom messages by entering ros2 msg list in the Command Window.

ROS 2 custom messages creation

Create Shareable ROS 2 Custom Message Package

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