ROS2 Message Received Callback for Code Generation

The Question

I'm trying to receive messages on a ROS2 network and exectute a callback function when messages are received. I need to deploy this with Code Generation to a C++ executable. When I run my code below in Matlab I get no errors, but when I try code generation I get the error show at the end of this question. I have included a simplified code and the script I used to deploy this code to my target machine. Any idea what the problem is? It seems there is an issue with the inputs to the callback but I am following the example shown in the section Subscribe Using Callback Functions in the Matlab ROS2 subscriber help file. Thanks in advance for any help with this.

The Program

function [] = multirate_tag_sorter_test_simple()
node = ros2node("myNode",0);
myMsg = ros2message("builtin_interfaces/Time");
mySub = ros2subscriber(node,"/myTopic","builtin_interfaces/Time", @receivedMessageCallback);

while true
    fprintf('Waiting for messages to arrive...')
    [~,~,~] = receive(mySub);
    fprintf('Pulse received and processed.')
end

end

function receivedMessageCallback(msg)
    fprintf('MESSAGE RECEIVED!');
end

The Code Generation Script

cfg = coder.config('exe');
cfg.Hardware = coder.hardware('Robot Operating System 2 (ROS 2)');
%cfg.Hardware.BuildAction = 'Build and run';
cfg.Hardware.BuildAction = 'Build and load';
cfg.Hardware.RemoteDeviceAddress = 'XXX.XXX.XXX.XXX';
cfg.Hardware.RemoteDeviceUsername = 'XXXXX';
cfg.Hardware.RemoteDevicePassword = 'XXXXXXX';
cfg.Hardware.DeployTo = 'Remote Device';
cfg.Hardware.ROS2Folder = '/opt/ros/galactic';
cfg.Hardware.ROS2Workspace = '~/uavrt_ws';
cfg.HardwareImplementation.ProdHWDeviceType = 'Intel->x86-64 (Linux 64)';
cfg.RuntimeChecks = true;%Disable for final deployments.
codegen multirate_tag_sorter_test_simple -args {} -config cfg

Error I am seeing:

??? Error calling

'multirate_tag_sorter_test_simple/receivedMessageCallback'.

This call-site passes more inputs to this function

than it can accept.

Error in ==> ros2subscriber Line: 288 Column: 21

Code generation failed: View Error Report

Error using codegen

Error in multirate_tag_sorter_test_codegen_script (line 22)

codegen multirate_tag_sorter_test_simple -args {} -config cfg

Answer 1

[Karthik Reddy Vennapureddy]

Hi Michael,

Thank you providing detailed reproduction steps, the following works in MATLAB simulation, but has restrictions in code-generation:

function receivedMessageCallback(msg)

fprintf('MESSAGE RECEIVED!');

end

Could you use the below syntax in callback function for code generation, as the code generation requires source event handle as the first argument of the callback function, as mentioned in the following note: Subscribe to messages on a topic - MATLAB (mathworks.com)

function receivedMessageCallback(src, msg)

fprintf('MESSAGE RECEIVED!');

end

Thanks,

Karthik Reddy

[Michael]

Thanks! It all works now.

I had seen that note when I first read the documentation, but then forgot because in the example in the documentation it has the callback function below that uses (messge) not (src, mesage). You might want to reach out the the team that does the technical writing/documentation and have them update this section of the help file or clarify that the additional arguments are needed for code generation.

function exampleHelperROS2PoseCallback(message)    
    % Declare global variables to store position and orientation
    global pos
    global orient
    
    % Extract position and orientation from the ROS message and assign the
    % data to the global variables.
    pos = [message.linear.x message.linear.y message.linear.z];
    orient = [message.angular.x message.angular.y message.angular.z];
end

[Michael]

@Karthik Reddy Vennapureddy I am having issues with passing additional variables to the callback function and posted that as a separate question. If you could answer that as well, I'd appreciated it. That question can be found here:

https://www.mathworks.com/matlabcentral/answers/1851568-ros2-subscriber-callback-function-arguments-for-code-generation?s_tid=srchtitle

[Karthik Reddy Vennapureddy]

Hi Michael,

I see that Josh Chen has responded to your question with a workaround in the same post. We are actively addressing the issues encountered with the subscriber callback and will deliver the fix in future updates.

Thanks,

Karthik Reddy

[Michael]

Yes he did. Thanks for reponding.