ROSCPP Related (e.g., rosbag, callback and spinning, and others...)

[HaFred]

roscpp does not try to specify a threading model for your application. This means that while roscpp may use threads behind the scenes to do network management, scheduling etc., it will never expose its threads to your application. roscpp does, however, allow your callbacks to be called from any number of threads if that's what you want.

[HaFred]

http://wiki.ros.org/roscpp/Overview/Callbacks%20and%20Spinning https://www.ncnynl.com/archives/201702/1298.html

Single-threaded Spinning

The easiest way of doing that is to do the ros::spin() which will hang the program. Or call the ros::spinOnce() periodically. ros::spinOnce() will call all the callbacks waiting to be called at that point in time. It helps on reducing the competition (racing) of different threads in the program. https://ithelp.ithome.com.tw/articles/10238734

[HaFred]

Chinese 中国大学MOOC

This MOOC also talks about the callback function. The whole series of MOOC is good with sample src, worthy for a try for sure! https://sychaichangkun.gitbooks.io/ros-tutorial-icourse163/content/chapter6/6.3.html

[HaFred]

Comparing roscpp & rospy

https://www.jianshu.com/p/997c6108d590

[HaFred]

Control the rate at which ROS updates with spinOnce()

int main()
{
  ros::Rate loop_rate(5); // 5Hz

  while (ros::ok())
  {
    Myclass.saveDataToFile();
    loop_rate.sleep();
    ros::spinOnce();
  }
}

https://answers.ros.org/question/11887/significance-of-rosspinonce/

[HaFred]

Srv Callback vs. topic Callback

Their input params are different: Topic Callback needs to put const msg& msg_param https://blog.csdn.net/qingdu007/article/details/53688625

[HaFred]

Multi-threaded Spin

https://xwlu.github.io/wiki/ros/multi-thread/ https://levelup.gitconnected.com/ros-spinning-threading-queuing-aac9c0a793f https://zhuanlan.zhihu.com/p/375418691

[HaFred]

pkgs settup in cmakelist

• catkin_pkgs vs. find_pkgs https://zhuanlan.zhihu.com/p/299148013

[HaFred]

rosbag

rostopic echo -b bag_name -p topic_name > file_name.csv  # to dump csv from rosbag file

https://zhuanlan.zhihu.com/p/97148509