RS BPearl publishes more points than it is supposed to

[Patrick-Lascombe]

Hello, I'm working with a RS Bpearl 3d lidar at 10 Hz, so it should publish 57600 per sensor_msgs::PointCloud2 message. But around every second I receive a message with 57984 points. I looked the data sent by the lidar through wireshark and I found the same thing : from time to time there is an extra packet of data.

Is this normal ? And if so what is the use of this extra packet ?

Below is a few headers from the sensor_msgs::PointCloud2 message where the extras points appears

header: 
  seq: 10895
  stamp: 
    secs: 1610721842
    nsecs: 488307476
  frame_id: "rslidar_optical_center"
height: 32
width: 1800
fields: "<array type: sensor_msgs/PointField, length: 6>"
is_bigendian: False
point_step: 32
row_step: 57600
data: "<array type: uint8, length: 1843200>"
is_dense: False
---
header: 
  seq: 10896
  stamp: 
    secs: 1610721842
    nsecs: 588924408
  frame_id: "rslidar_optical_center"
height: 32
width: 1812
fields: "<array type: sensor_msgs/PointField, length: 6>"
is_bigendian: False
point_step: 32
row_step: 57984
data: "<array type: uint8, length: 1855488>"
is_dense: False
---
header: 
  seq: 10897
  stamp: 
    secs: 1610721842
    nsecs: 688874483
  frame_id: "rslidar_optical_center"
height: 32
width: 1800
fields: "<array type: sensor_msgs/PointField, length: 6>"
is_bigendian: False
point_step: 32
row_step: 57600
data: "<array type: uint8, length: 1843200>"
is_dense: False
---

[HaoQChen]

Hi, the motor speed is not that accurate, and network has delay. So point is not that steady.

You can set split frame mode to fixed number of package

lidar:
  - driver:
      lidar_type: RS128            #LiDAR type - RS16, RS32, RSBP, RS128, RS80, RSM1, RSHELIOS
      frame_id: /rslidar           #Frame id of message
      msop_port: 6699              #Msop port of lidar
      difop_port: 7788             #Difop port of lidar
      start_angle: 0               #Start angle of point cloud
      end_angle: 360               #End angle of point cloud 
      min_distance: 0.2            #Minimum distance of point cloud
      max_distance: 200            #Maximum distance of point cloud
      use_lidar_clock: false       #True--Use the lidar clock as the message timestamp
                                   #False-- Use the system clock as the timestamp  
     split_frame_mode:2