Velodyne VLP-16 poll() timeout

asked 2022-11-03 22:36:38 -0500

ThomasL624
11 ●4 ●5 ●7

updated 2022-11-03 22:40:13 -0500

Environment:

Docker
Ubuntu 20.04
ROS2 Galactic

Background:

Actually this environment worked few days ago, I can see the scan data from Rviz2. However after I trying to start 2 x VLP-16, then both of them keep sending error about poll() timeout, even I only connect one VLP16 and use the clean source code.

I can ping the LiDAR and also can see there are many UDP packages in Wireshark. The webUI can be access. Below is the IP setup:

Host IP: 192.168.1.100
LIDAR IP: 192.168.1.202:2369
LIDAR destination IP: 192.168.1.100

Whats the problem here? I have browsed quite a bit in Google and still no solution was found yet... Totally no idea how to solve this. I tried directly connect the Lidar to Host, and still same error.

answered 2022-11-04 06:49:07 -0500

Mike Scheutzow
4918 ●2 ●430 ●45

updated 2022-11-04 06:52:48 -0500

A velodyne device transmits its raw scan data to a specific IP port, so in the velodyne config page, you need to assign each velodyne device a unique port number e.g. 2368 and 2369. On the ROS side you will need to run a separate ros-driver for each velodyne device, and configure the driver with the port number you have assigned for the UDP packets to arrive on. In the standard driver, the parameter is named port.

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I config both LiDAR as follow:

lidar_left: port: 2368 Host Dest: 192.168.1.100 IP: 192.168.1.201

lidar_right: port: 2369 Host Dest: 192.168.1.100 IP: 192.168.1.202

Both can be ping at the same time with corresponding IP addr. In ROS2 launch file, I create a new set of config file and change the default launch (clone from repo) with specified namespace as follow:

lidar_left

/lidar_left/velodyne_driver_node
/lidar_left/velodyne_convert_node
/lidar_left/velodyne_laserscan_node

lidar_right:

/lidar_right/velodyne_driver_node
/lidar_right/velodyne_convert_node
/lidar_right/velodyne_laserscan_node

These nodes can be seen via rqt_graph and ros2 node list

However, one of the lidar keep saying that poll() timeout and only one lidar pointcloud can be see in Rviz2, even though there are different topics (left and right). What will be the problem?

In wireshark, I can see both lidar sending UDP to different socket with payload.

ThomasL624 ( 2022-11-07 03:50:36 -0500 )edit

I have this same issue when trying to connect two VLP-16 lidars. Can you help me?

jerek ( 2023-02-08 03:49:27 -0500 )edit

I am not sure if my solution is the fix, but at least it fixed mine. There were no software/config issues, I solved it by unplugging all the ethernet content to the switch, and power cycled the switch. And it showed both lidar scans to me. It might be caused by some network storm issue idk...

ThomasL624 ( 2023-02-09 08:23:31 -0500 )edit

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Velodyne VLP-16 poll() timeout

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