MATLAB: Matlab ROS subscriber basic example

Robotics System Toolboxrossubscriberturtlebot

Have you a step by step example to create a subscriber I do this

setenv('ROS_IP','192.168.1.41') % adress PC with Matlab setenv('ROS_HOSTNAME','192.168.1.41') setenv('ROS_MASTER_URI','http://192.168.1.28:11311/') % adress turtlebot rosinit rostopic list

Here I am able to see all the topics that are on the turtlebot And I am able to command to move my turtlebot with

velocity = -0.1; % meters per second robot = rospublisher('/mobile_base/commands/velocity') velmsg = rosmessage(robot) velmsg.Linear.X = velocity; for i=1:50000 i send(robot,velmsg); end

I can also ask to my Turtle to emitting a noise

soundpub = rospublisher('/mobile_base/commands/sound', 'kobuki_msgs/Sound') soundmsg = rosmessage('kobuki_msgs/Sound'); soundmsg.Value = 6; % Any number 0-6 send(soundpub,soundmsg);

But when I want to subscribe to a topic…

odom = rossubscriber('/odom')

odomdata = receive(odom,3);

I have this error message

Error using robotics.ros.Subscriber/receive (line 325)

The function did not receive any data and timed out.

When I apply : rostopic info /odom I obtain :

Type: nav_msgs/Odometry Publishers: * /mobile_base_nodelet_manager (<http://turtlebot.local:58513/>) Subscribers: * /matlab_global_node_86572 (<http://192.168.1.65:49791/>) * /matlab_turtlebot_69671 (<http://192.168.1.65:49752/>)

What I should do to be able to subscribe and read a topic of my Turtlebot with Matlab My configuration is Turtlebot : Ubuntu 14.4 + Indigo PC : Windows10 + Matlab 2017a (I stop all firewall)

Thank you in advance for your help

Best Answer

My problem come to multipl IP adress for my Matlab computer...

To help other persone, the configuration that work well with my Turtlebot

In my case, the IP adress are

PC with Matlab : 192.168.1.41

Turtlebot computer : 192.168.1.28

In the .bashrc, I have

source /opt/ros/indigo/setup.bash

export ROS_MASTER_URI=http//192.168.1.28:11311

export ROS_HOSTNAME=192.168.1.28

export ROS_IP=192.168.1.28

In Matlab 2 solutions are possible:

solution 1:

setenv('ROS_IP','192.168.1.41') % adress PC with Matlab

setenv('ROS_HOSTNAME','192.168.1.41')

setenv('ROS_MASTER_URI','http://192.168.1.28:11311/') % adress turtlebot

rosinit

solution 2 :

rosinit('http://192.168.1.28:11311', 'NodeHost', '192.168.1.41')

Related Solutions

MATLAB: Is the ROS subscriber callback in MATLAB not triggered when messages are published from an external ROS node (not in MATLAB)

This issue arises because the subscriber cannot resolve the URI of the publisher. When a ROS node advertises a topic, it provides a hostname:port combination (a URI) that other nodes use to establish contact when they want to subscribe to that topic. It is important that the hostname the publishing node provides can be used by all other nodes to contact it. The ROS client libraries use the name reported by the machine as hostname. This is the name that is returned by the Linux command “hostname”. If a machine reports a hostname that is not addressable by other machines, you need to set either the ROS_IP or ROS_HOSTNAME environment variables. (Reference: http://wiki.ros.org/ROS/NetworkSetup)

ROS_IP and ROS_HOSTNAME are optional environment variables that set the declared network address of a ROS Node or tool. They are mutually exclusive; if both are set, ROS_HOSTNAME will take precedence. Use ROS_IP if you are specifying an IP address and ROS_HOSTNAME if you are specifying a name. (Reference: http://wiki.ros.org/ROS/EnvironmentVariables)

The environment variable ROS_MASTER_URI is required when the ROS core is not running on localhost. ROS_MASTER_URI are used by ROS nodes to locate the master.

TO RESOLVE THIS ISSUE, ALWAYS SPECIFY ROS_IP BEFORE STARTING A NODE ON LINUX. Use the IP address of the network interface on which the node is communicating with the ROS network.

To ensure the correct behavior of the MATLAB ROS support package, it is recommended that you always specify ROS_IP and ROS_MASTER_URI explicitly.

For example, if the ROS core is running on a machine with IP: 192.168.198.128 and MATLAB is running on a machine with IP: 192.168.198.1, then we should set up the environment variables as follows (please replace the IP addresses below with the IP addresses of your network setup):

In MATLAB,

 setenv('ROS_MASTER_URI','http://192.168.198.128:11311')
 setenv('ROS_IP','192.168.198.1')

In Linux terminal:

 $ export ROS_IP=192.168.198.128
 $ export ROS_MASTER_URI=http://192.168.198.128:11311
 $ start a roscore, publisher or subscriber

To make the above change permanent, put the above two export commands in the “.bashrc” file, as follows,

 $ cd ~
 $ gedit .bashrc

At the end of the file “.bashrc”, add the two export statements.

 export ROS_IP=192.168.198.128
 export ROS_MASTER_URI=http://192.168.198.128:11311

Restart Linux terminal.

MATLAB: Use MATLAB Robotics System Toolbox to receive ROS message

I figureed out the solution for this problem. The following steps seem to be helpful:

1. In Ubuntu PC hosts file (/etc/hosts), add the hostnames and the IP addresses of both Ubuntu PC and Windows PC

2. In Windows PC host file (/windows/system32/driver/etc/host), do the same thing as in previous step

3. Turn off all the firewalls on Window PC and Ubuntu PC (if there is any)

4. Reboot both machines to make the new host files effective

5. Set the following environment variables on Ubuntu PC

   sudo gedit ~/.bashrc

Add the following lines in .bashrc file, save and then restart terminal

   export ROS_MASTER_URI=http://Ubuntu_PC_IP:11311
   export ROS_IP=Ubuntu_PC_IP

6. On Windows MATLAB, set the environment variables for ROS:

   setenv('ROS_MASTER_URI','http://Ubuntu_PC_IP:11311')
   setenv('ROS_IP','Windows_PC_IP')
   rosinit

Then it should work. I did almost everything except Step 2, which caused the above problem. I hope this would help someone who has the similar problem.

Best Answer

Related Solutions

MATLAB: Is the ROS subscriber callback in MATLAB not triggered when messages are published from an external ROS node (not in MATLAB)

MATLAB: Use MATLAB Robotics System Toolbox to receive ROS message

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