LIDAR LMS111 and rosserial delay

edit

Hy there,

i have following problem: I use a LIDAR LMS111 to get an average distance to an object. The node chain looks like: LIDAR---> scan---> scan_filter---> republisher---> rosserial.

I use the scan_filter to cut out a small area from the whole scan. Then i use a own written node "republisher" to publish an average of some points to a range message. This range message gets then subscribed by a microcontroller.

Now the problem is that i have a huge delay ~ 500ms of the range information on the microcontroller. I use a baudrate of 115200. The range msg gets published with a sampling rate of 50 Hz.

Does somebody have an idea where the delay coudl come from, or a suggestion how to evaluate the timing in ROS?

Thanks in advance!

Michael

The republisher node::

#include "ros/ros.h"
#include "std_msgs/String.h"
#include "sensor_msgs/LaserScan.h"
#include "sensor_msgs/Range.h"
#include "message_filters/subscriber.h"
#include "tf/message_filter.h"
#include "tf/transform_listener.h"
#include "filters/filter_chain.h"

// this node subscribes to the LaserScan_msg /scan_filtered topic does some average
// of the data and republishes the result to the topic of type sensor_msgs::Ranges namely
// ranges
// class in order to not use global variables
class HandelSubandPub
{
public:
sensor_msgs::Range range;
// handle subscriber and publisher
HandelSubandPub()
  {
    //Topic you want to publish
    publish_class_member = n.advertise<sensor_msgs::Range>("ranges", 1000);
    //Topic you want to subscribe
    subscribe_class_member = n.subscribe("scan_filtered", 1000,&HandelSubandPub::chatterCallback,this);
  }
void chatterCallback(const sensor_msgs::LaserScan::ConstPtr& msg_in)
    {
      //ROS_INFO("callback");
      range.header = msg_in->header;
range.range =   (msg_in->ranges[1]+msg_in->ranges[3]+msg_in->ranges[6])/3;
    publish_class_member.publish(range);
    }
private: 
    ros::NodeHandle n;
    ros::Publisher publish_class_member;
    ros::Subscriber subscribe_class_member;
};
int main(int argc, char **argv)
{
 ros::init(argc, argv, "republisher");
 HandelSubandPub HSPObject;
 ros::spin();
 return 0;
}