ROS in Simulink never receive anything

I am having really hard time getting ROS in Simulink to receive any messages from a remote PC.

It never works in MatLab either but here's the rub:
I run
rosinit('111.111.0.8') % a sudo address for my remote running turtlebot3_fake
I then jump over to Simulink and create a model that looks like this:

I hit run and it is always zero. What am I doing wrong?

Cheers,

Coach

Answer 1

[Ameer Hamza]

Please refer to this link: https://www.mathworks.com/help/ros/ug/connect-to-a-ros-network.html#ConnectToAROSNetworkExample-2

More specifically, you also need to set ROS_MASTER_URI and ROS_IP as specified in the mentioned link to connect to a remote master. Additionally, make sure that you can successfully ssh into the remote server.

[Clayton Allen]

Ameer,

I am going nuts here! I turned off my Jetson TX2 and turned it back on. The TX2 is where my MASTER is running.

On MatLab, I do the following:

% Jetson TX2 IP address
jetson_node_address = '192.xxx.x.8'

% Initialize ROS
rosinit(jetson_node_address,11311,"NodeName","matlab_node")


rosnode list
/matlab_node
/rosout
>> rostopic list
/rosout    
/rosout_agg
>> rostopic list
/clock                        
/cmd_vel                      
/gazebo/link_states           
/gazebo/model_states          
/gazebo/parameter_descriptions
/gazebo/parameter_updates     
/gazebo/set_link_state        
/gazebo/set_model_state       
/imu                          
/joint_states                 
/odom                         
/rosout                       
/rosout_agg                   
/scan                         
/tf 

So clearly, this means there is a connection right?

Next, I run these examples:

laser = rossubscriber('/scan');
>> scandata = receive(laser, 10);
Error using ros.Subscriber/receive (line 294)
The function did not receive any data and timed out.
 
>> odom = rossubscriber('/odom')

odom = 

  Subscriber with properties:

        TopicName: '/odom'
      MessageType: 'nav_msgs/Odometry'
    LatestMessage: [0×1 Odometry]
       BufferSize: 1
    NewMessageFcn: []

>> odomdata = receive(odom, 10)
Error using ros.Subscriber/receive (line 294)
The function did not receive any data and timed out.

[Clayton Allen]

I moved my install to a windows based PC and viola! I would like the MatLab folks to maybe consider this a bug.

Orginal install:

MacBookPro

OS Mojave

[Ameer Hamza]

It appears to be some issues with network configuration or the setting of environment variables. I am able to receive a message published by a node from an external server in MATLAB running on macOS Catalina, and I have previously done it on Mojave too.

The problem you mentioned: you are able to get the node list but cannot receive a message from a subscribed topic that happens when environment variables on the master server and MATLAB are not set properly. This link explains how to configure these variables: https://www.mathworks.com/matlabcentral/answers/119559-why-is-the-ros-subscriber-callback-in-matlab-not-triggered-when-messages-are-published-from-an-exter