(20241001).

How To create a customized ROS msg in MATLAB?

MATLAB Help

step-1. Place your custom messages in a location and note the folder path.

It is recommended to put all your custom message definitions in a single packages folder.

% folderpath = 'c:\MATLAB\custom_msgs\packages';
folderpath = '/home/teng/MATLAB/custom_msgs/packages';

The above cmd no need to run, but you need to find your custom msg package folder in catkin_ws, and better to copy it to a single package folder in MATLAB. For example, my custom msg is located in /home/teng/catkin_ws2/src/phantom_omni/teng4pkg_msgs, then I copy the package folder teng4pkg_msgs into the MATLAB path /home/teng/MATLAB/custom_msgs/ where all the custom ROS msg definitions to be used in MATLAB will be collected here in the future.

step-2. In MATLAB, run the command to create custom msg for MATLAB,

% rosgenmsg('c:\MATLAB\custom_msgs')
rosgenmsg('/home/teng/MATLAB/custom_msgs/')

Matlab will run and show the following info if successful,

rosgenmsg(‘/home/teng/MATLAB/custom_msgs/’) Identifying message files in folder ‘/home/teng/MATLAB/custom_msgs’..Done. Validating message files in folder ‘/home/teng/MATLAB/custom_msgs’..Done. [1/1] Generating MATLAB interfaces for custom message packages… Done. Running catkin build in folder ‘/home/teng/MATLAB/custom_msgs/matlab_msg_gen_ros1/glnxa64’. Build in progress. This may take several minutes… Build succeeded.build_log.

To use the custom messages in Matlab, follow these steps:

1. Add the custom message folder to the MATLAB path by executing:

addpath('/home/teng/MATLAB/custom_msgs/matlab_msg_gen_ros1/glnxa64/install/m')
savepath

Note, the above cmd may need to run each time you restart MATLAB (not tested), But it is ok.

2. Refresh all message class definitions, which requires clearing the workspace, by executing:

clear classes
rehash toolboxcache

3. Verify that you can use the custom messages.

Enter “rosmsg list” and ensure that the output contains the generated custom message types.

rosmsg list

It will show a long list including your custom msg types. For example, mine is,

teng4pkg_msgs/Arm_State
teng4pkg_msgs/PoseCartesian6DOF
teng4pkg_msgs/Vector7DOF

4. Check the details of a specific msg type

% custommsg = rosmessage('B/Standalone')
custommsg = rosmessage('teng4pkg_msgs/PoseCartesian6DOF')

custommsg = ROS PoseCartesian6DOF message with properties: MessageType: ‘teng4pkg_msgs/PoseCartesian6DOF’ X: 0 Y: 0 Z: 0 A: 0 B: 0 G: 0 Use showdetails to show the contents of the message

Bingo. All done. Now you can use the custom msg in Matlab.

Debugging.

Matlab may need to configure ROS first. If so, first run this cmd in a Ubuntu terminal.

whereis python #Find the location of python in your pc.
sudo apt install python3.8-venv

Then, in MATLAB go to find Home->Preferences->ROS Toolbox, click button Open ROS Toolbox Preferences. put the path (e.g., mine is /usr/bin/python3.8) in the ‘browse’ line, and click Recreate Python Environment. Done.

Created on 2024-10-01.