ROS Learning Notes

ROS Learning Notes 04

Keypoints

• Customized msg type

Customized msg type

• Must in work_space/src/topic_name/msg folder
• Example: /home/lshi/rosleaning/src/topic_learning/Person.msg
  • MSG file definition:

    string name
    uint8 sex
    uint8 age
    
    uint8 unknown = 0
    uint8 male = 1
    uint8 female = 2
    

  • Add dependency in package.xml:

    <build_depend>message_generation</build_depend>
    <exec_depend>message_runtime</exec_depend>
    

  • Add compilation route in CMakeLists.txt:

    message_generation # find_package section
    
    # `Declare ROS messages, services and actions` section
        
    add_message_files(FILES Person.msg)
    generate_messages(DEPENDENCIES std_msgs)
    
    # catkin specific configuration section
    CATKIN_DEPENDS message_runtime ...  
    

  • Compile in work_space to generate the msg head file in devel/include/topic_name/Person.h:

    cd ~/roslearning
    catkin_make
    

• Publisher and subscriber
  • publisher

    # include <ros/ros.h>
    # include "topic_learning/Person.h"
    
    int main(int argc, char **argv){
    
        ros::init(argc, argv, "person_publisher");
        ros::NodeHandle nh;
        ros::Publisher person_info_pub = nh.advertise<topic_learning::Person>("/person_info", 10);
        ros::Rate loop_rate(1);
    
        int count = 0;
        while (ros::ok()){
            topic_learning::Person person_msg;
            person_msg.name = "Tom";
            person_msg.age = 18;
            person_msg.sex = topic_learning::Person::male;
    
            person_info_pub.publish(person_msg);
            ROS_INFO("Publish Person Info: name:%s age:%d sex:%d", person_msg.name.c_str(), person_msg.age, person_msg.sex);
    
            loop_rate.sleep();
        }
    }
    

    #!/usr/bin/env python
    # -*- coding: utf-8 -*-
    import rospy
    from topic_learning.msg import Person
    
    def person_publisher():
      rospy.init_node('person_publisher', anonymous=True)
      person_info_pub = rospy.Publisher('/person_info', Person, queue_size=10)
      rate = rospy.Rate(10)
    
      while not rospy.is_shutdown():
        person_msg = Person()
        person_msg.name = "Tom"
        person_msg.age = 18
        person_msg.sex = Person.male
    
        person_info_pub.publish(person_msg)
        rospy.loginfo("Publish person message[%s, %d, %d]", person_msg.name, person_msg.age, person_msg.sex)
    
        rate.sleep()
    
    if __name__ == '__main__':
      try:
        person_publisher()
      except rospy.ROSInterruptException:
        pass
    

  • subscriber

      #include <ros/ros.h>
      #include "topic_learning/Person.h"
    
      void personInfoCallback(const topic_learning::Person::ConstPtr& msg){
          ROS_INFO("Subscribe Person Info: name:%s age:%d sex:%d", msg->name.c_str(), msg->age, msg->sex);
      }
    
      int main(int argc, char **argv){
    
          ros::init(argc, argv, "person_subscriber");
          ros::NodeHandle nh;
          ros::Subscriber person_info_sub = nh.subscribe("/person_info", 10, personInfoCallback);
          ros::spin();
          return 0;
      }
    

      #!/usr/bin/env python
      # -*- coding: utf-8 -*-
    
      import rospy
      from topic_learning.msg import Person
    
      def personInfoCallback(msg):
        rospy.loginfo("Subscribe Person Info: name:%s age:%d sex:%d", msg.name, msg.age, msg.sex)
    
      def person_subscriber():
        rospy.init_node('person_subscriber', anonymous=True)
        rospy.Subscriber('/person_info', Person, personInfoCallback)
        rospy.spin()
    
      if __name__ == '__main__':
        person_subscriber()
    
    

  • Compile

    # add dependency in CMakeLists.txt
    add_executable(person_publisher src/person_publisher.cpp)
    target_link_libraries(person_publisher ${catkin_LIBRARIES})
    add_dependencies(person_publisher ${PROJECT_NAME}_generate_messages_cpp)
    
    add_executable(person_subscriber src/person_subscriber.cpp)
    target_link_libraries(person_subscriber ${catkin_LIBRARIES})
    add_dependencies(person_subscriber ${PROJECT_NAME}_generate_messages_cpp)
    

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