Felix Tr's profile - activity

Hello All,

Background:

My idea is to receive not constant number of topics, to which I want to subscribe in my C code. I decided to do it in the next way: I will prepare a text file with the number and the name of the topics ---> convert it using launch file syntax to a string ---> parse the string in my C code ---> decide to which topics to subscribe.

In such a way I will only have to change the text file, while the launch file and the C code will not be changed.

Question:

I have written the next line of code in my launch file:

<param name="topics_list" textfile="$(find package_name)/file_name.txt"/>

And I have placed my text file in the appropriate folder. In my C file I do the next:

if ( nh.getParam("topics_list", topicsList) )
{
   ROS_INFO ("The contents of the file \"file_name.txt\" as a string are: %s\n",   
   topicsList); 
}
else
{
   ROS_INFO ("The topics list was not loaded succesfully. Aborting...\n");
   ros::shutdown();
}

It doesn´t work.

1. Is my way correct?
2. Why the above doesn´t work properly?

Thank you all in advance, Felix.

Hello All,

I am relatively new user of ROS, and would be grateful if you could answer to my question. I work with Linux and C, and I want to deliver arguments to my callback function. Lets say I want to deliver to it the next struct as a parameter:

typedef struct imageManagmentStruct
{
    IplImage*  pSrcIplImage;
    IplImage*  pDstIplImage;
    GdkPixbuf* pGtkPixbuf;
    GtkWidget* pGtkImgWindow;    
    int        previousImageSize;
    int        left_attach;
    int        right_attach;
    int        top_attach;
    int        bottom_attach;    
} ImageManagmentStruct;

My callback is:

void imageCallback ( const sensor_msgs::ImageConstPtr& msg,
                     ImageManagmentStruct* pToImageManagmentStruct
                   )
{
    // My code.
}

The call to the callback from the main done like this:

ros::Subscriber subLeft = nh.subscribe ("/bb2/left/image_raw", 10, imageCallback,  
                                        pointerToImageManagmentStruct);

And this is not compiling...

Thank you all, Felix.

Hello All,

I am relatively new user of ROS, and this is the first time I should write a launch file. I would be happy if you could navigate me to the best way to do it.

What I do is: I subscribe to recorded topics (bag files) using image_transport package, I republish their content to different topics (from compressed to raw), and eventually I subscribe to those topics with my subscriber (the only node I have created). The shell command lines I use in order to run my program without a launch file are:

roscore

rosbag play -l left_camrea.bag

rosbag play -l rigth_camrea.bag

rosrun image_transport republish compressed in:=/bb2/left/image_rect raw 
  out:=lefttopic

rosrun image_transport republish compressed in:=/bb2/right/image_rect raw     
  out:=righttopic

rosrun myPackage myExecutibleFile

I also need to configure parameters for my program via this launch file.

What from the above can/should be included in the launch file? What should not?

What is the conceptual structure of my file should be like?

Thank you for your attention, Felix,

Hello all,

My goal is to subscribe to an "unknown" number of topics. I want to do the next algorithm:

1. Create a "yaml" file for ROS, where all my topics are listed.
2. Extract it´s data as a string.
3. Parse the data, according to which I will know the number and the names of the topics to which I want to subscribe.
4. Subscribe in a loop to all of them.

The problem is that I have never written a "yaml" file, and the explanations in the Wikipedia page are not good for ROS. I would also be happy to know what is the best way to "parse" the info in my code (C).

Thank you for your help, Felix.