1 #include "ros/ros.h"
   2 #include "sensor_msgs/Range.h"
   3 
   4 /**
   5  * This tutorial demonstrates simple receipt of sonar sensor data over the ROS system.
   6  */
   7 
   8 /**
   9  * Callback function executes when new topic data comes.
  10  * Task of the callback function is to print data to screen.
  11  */
  12 void chatterCallback(const sensor_msgs::Range::ConstPtr& msg)
  13 {
  14   ROS_INFO("Sonar Seq: [%d]", msg->header.seq);
  15   ROS_INFO("Sonar Range: [%f]", msg->range);
  16 }
  17 
  18 int main(int argc, char **argv)
  19 {
  20   /**
  21    * The ros::init() function needs to see argc and argv so that it can perform
  22    * any ROS arguments and name remapping that were provided at the command line.
  23    * For programmatic remappings you can use a different version of init() which takes
  24    * remappings directly, but for most command-line programs, passing argc and argv is
  25    * the easiest way to do it.  The third argument to init() is the name of the node.
  26    *
  27    * You must call one of the versions of ros::init() before using any other
  28    * part of the ROS system.
  29    */
  30   ros::init(argc, argv, "infrared_listener");
  31 
  32   /**
  33    * NodeHandle is the main access point to communications with the ROS system.
  34    * The first NodeHandle constructed will fully initialize this node, and the last
  35    * NodeHandle destructed will close down the node.
  36    */
  37   ros::NodeHandle n;
  38 
  39   /**
  40    * The subscribe() call is how you tell ROS that you want to receive messages
  41    * on a given topic.  This invokes a call to the ROS
  42    * master node, which keeps a registry of who is publishing and who
  43    * is subscribing.  Messages are passed to a callback function, here
  44    * called chatterCallback.  subscribe() returns a Subscriber object that you
  45    * must hold on to until you want to unsubscribe.  When all copies of the Subscriber
  46    * object go out of scope, this callback will automatically be unsubscribed from
  47    * this topic.
  48    *
  49    * The second parameter to the subscribe() function is the size of the message
  50    * queue.  If messages are arriving faster than they are being processed, this
  51    * is the number of messages that will be buffered up before beginning to throw
  52    * away the oldest ones.
  53    */
  54   ros::Subscriber sub = n.subscribe("sensor/sonar0", 1000, chatterCallback);
  55 
  56   /**
  57    * ros::spin() will enter a loop, pumping callbacks.  With this version, all
  58    * callbacks will be called from within this thread (the main one).  ros::spin()
  59    * will exit when Ctrl-C is pressed, or the node is shutdown by the master.
  60    */
  61   ros::spin();
  62 
  63   return 0;
  64 }