Lidar Behaving Abnormaly

[Pbinu]

Product and Purchase

• Product model: ROSOrin Mecanum (4-mecanum-wheel base with Jetson Orin)
• Controller board: Jetson Orin NX (running ROSOrin_Mecanum per system banner), with onboard STM32 handled via ros_robot_controller serial link

Software and Environment

• Operating system: Ubuntu 22.04.5 LTS, kernel 5.15.148-tegra (aarch64)
• Connection method: SSH over wifi (robot as wifi client) and USB ethernet-gadget
• Software version: V2.0|App_ROS2_1.0|2026-06-04 (per boot banner)
• Tutorial step: LiDAR/Nav2 bringup — trying to launch peripherals/lidar.launch.py as part of setting up autonomous navigation (Nav2)

Issue Description

1. What did you expect to happen?
The LD19 lidar driver should start successfully and continuously publish /scan data for use in obstacle avoidance and Nav2 navigation.

2. What actually happened?
The driver reports a successful start, then fails with “ldlidar communication is abnormal” exactly ~3 seconds later, every single time, and the process exits.

Reproduction Steps

1. Power on the robot and SSH in.
2. Run: ros2 launch peripherals lidar.launch.py
3. Observe “ldlidar node start is success,” followed ~3 seconds later by “ldlidar communication is abnormal” and the process dying (exit code 1). This happens on every attempt, including after full reboot and after physically reseating the lidar’s cable.

Evidence

What You Have Tried

1. Confirmed nothing else is holding the serial port: sudo fuser /dev/lidar returns empty.

2. Read raw bytes directly off the port: sudo timeout 3 cat /dev/ttyACM0 | xxd | head -20 — output never contains the 0x54 frame header the LD19 protocol requires, e.g.

   

Urgency:

Very Urgent- it is for a research paper and I need this set up before my paper deadline

[hiwonder_Ryo]

Official support staff are being brought in to help with this issue. If you still need my help, reply here and @ me. @Hiwonder_Scarlett

[Hiwonder_Scarlett]

Hi there,

Based on the provided information, you did not stop the app auto-start service before launching the LiDAR feature.

Please try stopping the app auto-start first:

sudo systemctl stop start_app_node.service

The command to launch the LiDAR is:

ros2 launch app LiDAR_node.launch.py debug:=true

Please try these steps to see if the gameplay can run normally. Looking forward to your reply.

[Pbinu]

I tried it and here is what I got back:

sudo systemctl stop start_app_node.service
sudo systemctl stop button_scan.service
sleep 2
sudo fuser -k /dev/lidar 2>/dev/null
sleep 2
ros2 launch /home/ubuntu/ros2_ws/src/app/launch/lidar_node.launch.py debug:=true
[INFO] [launch]: All log files can be found below /home/ubuntu/.ros/log/2026-09-09-05-57-40-239132-ubuntu-desktop-7202
[INFO] [launch]: Default logging verbosity is set to INFO

INFO\] \[ldlidar_stl_ros2_node-1\]: process started with pid \[7205

INFO\] \[joint_state_publisher-2\]: process started with pid \[7207

INFO\] \[robot_state_publisher-3\]: process started with pid \[7209

INFO\] \[ros_robot_controller-4\]: process started with pid \[7211

INFO\] \[odom_publisher-5\]: process started with pid \[7213

INFO\] \[ekf_node-6\]: process started with pid \[7215

INFO\] \[servo_controller-7\]: process started with pid \[7219

INFO\] \[lidar_controller-8\]: process started with pid \[7236

[robot_state_publisher-3] [INFO] [1788904660.743672916] [robot_state_publisher]: got segment base_footprint
[robot_state_publisher-3] [INFO] [1788904660.743947432] [robot_state_publisher]: got segment base_link
[robot_state_publisher-3] [INFO] [1788904660.743973705] [robot_state_publisher]: got segment camera_link0
[robot_state_publisher-3] [INFO] [1788904660.743984842] [robot_state_publisher]: got segment imu_link
[robot_state_publisher-3] [INFO] [1788904660.743992907] [robot_state_publisher]: got segment lidar_frame
[robot_state_publisher-3] [INFO] [1788904660.744000203] [robot_state_publisher]: got segment lidar_sim_frame
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.749190491] [LD19]: LDLiDAR SDK Pack Version is: v3.0.3
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.749493521] [LD19]: <product_name>: LDLiDAR_LD19
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.749518003] [LD19]: <topic_name>: scan
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.749526995] [LD19]: <frame_id>: lidar_frame
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.749535252] [LD19]: <port_name>: /dev/lidar
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.749542740] [LD19]: <port_baudrate>: 230400
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.749553461] [LD19]: <laser_scan_dir>: Counterclockwise
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.749562390] [LD19]: <enable_angle_crop_func>: true
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.749569686] [LD19]: <angle_crop_min>: 0.000000
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.749583799] [LD19]: <angle_crop_max>: 0.000000
[ldlidar_stl_ros2_node-1] [INFO] [1788904660.757168913] [LD19]: ldlidar node start is success
[joint_state_publisher-2] [INFO] [1788904661.541661700] [joint_state_publisher]: Waiting for robot_description to be published on the robot_description topic…
[odom_publisher-5] [INFO] [1788904661.630075858] [odom_publisher]: 0.940000 1.020000
[odom_publisher-5] [INFO] [1788904661.685174560] [odom_publisher]: start
[lidar_controller-8] /home/ubuntu/.local/lib/python3.10/site-packages/numpy/core/getlimits.py:518: UserWarning: The value of the smallest subnormal for <class ‘numpy.float64’> type is zero.
[lidar_controller-8] setattr(self, word, getattr(machar, word).flat[0])
[lidar_controller-8] /home/ubuntu/.local/lib/python3.10/site-packages/numpy/core/getlimits.py:89: UserWarning: The value of the smallest subnormal for <class ‘numpy.float64’> type is zero.
[lidar_controller-8] return self._float_to_str(self.smallest_subnormal)
[ros_robot_controller-4] Exception in thread Thread-1 (recv_task):
[ros_robot_controller-4] Traceback (most recent call last):
[ros_robot_controller-4] File “/usr/lib/python3.10/threading.py”, line 1016, in _bootstrap_inner
[ros_robot_controller-4] self.run()
[ros_robot_controller-4] File “/usr/lib/python3.10/threading.py”, line 953, in run
[ros_robot_controller-4] self._target(*self._args, **self._kwargs)
[ros_robot_controller-4] File “/home/ubuntu/ros2_ws/build/ros_robot_controller/ros_robot_controller/ros_robot_controller_sdk.py”, line 538, in recv_task
[ros_robot_controller-4] recv_data = self.port.read()
[ros_robot_controller-4] File “/home/ubuntu/.local/lib/python3.10/site-packages/serial/serialposix.py”, line 595, in read
[ros_robot_controller-4] raise SerialException(
[ros_robot_controller-4] serial.serialutil.SerialException: device reports readiness to read but returned no data (device disconnected or multiple access on port?)
[ros_robot_controller-4] [INFO] [1788904662.343560442] [ros_robot_controller]: 舵机 1 偏差补偿: 0 (来自 /home/ubuntu/software/Servo_upper_computer/servo_config.yaml)
[ros_robot_controller-4] [INFO] [1788904662.344507485] [ros_robot_controller]: 舵机 2 偏差补偿: 0 (来自 /home/ubuntu/software/Servo_upper_computer/servo_config.yaml)
[ros_robot_controller-4] [INFO] [1788904662.345209295] [ros_robot_controller]: 舵机 3 偏差补偿: 0 (来自 /home/ubuntu/software/Servo_upper_computer/servo_config.yaml)
[ros_robot_controller-4] [INFO] [1788904662.345922146] [ros_robot_controller]: 舵机 4 偏差补偿: 0 (来自 /home/ubuntu/software/Servo_upper_computer/servo_config.yaml)
[ros_robot_controller-4] [INFO] [1788904662.351204315] [ros_robot_controller]: start
[servo_controller-7] [INFO] [1788904662.546440376] [servo_manager]: start
[lidar_controller-8] [INFO] [1788904662.586322579] [lidar_app]: start
[servo_controller-7] [INFO] [1788904662.787185762] [controller_manager]: start
[ldlidar_stl_ros2_node-1] [ERROR] [1788904663.758166092] [LD19]: ldlidar communication is abnormal.

ldlidar_stl_ros2_node-1\] \[LDS\]\[INFO\]\[1788904660.756981444\]\[Actual BaudRate reported:230400

[ERROR] [ldlidar_stl_ros2_node-1]: process has died [pid 7205, exit code 1, cmd ‘/home/ubuntu/third_party/third_party_ws/install/ldlidar_stl_ros2/lib/ldlidar_stl_ros2/ldlidar_stl_ros2_node --ros-args -r __node:=LD19 --params-file /tmp/launch_params_cpl0t7et -r scan:=scan_raw’].

INFO\] \[apply_calib-9\]: process started with pid \[7335

INFO\] \[complementary_filter_node-10\]: process started with pid \[7337

[complementary_filter_node-10] [INFO] [1788904665.739027620] [imu_filter]: Starting ComplementaryFilterROS

it still gives me the same error

[Pbinu]

here is a screenshot

[hiwonder_Ryo]

抱歉，我无法处理您的问题，请耐心等待支持人员为您解答。我将不再在此贴中继续回复。如仍需要我的帮助，请@我处理。

[hiwonder_Ryo]

抱歉，我无法处理您的问题，请耐心等待支持人员为您解答。我将不再在此贴中继续回复。如仍需要我的帮助，请@我处理。

[Pbinu]

@Hiwonder_Scarlett any updates?

[Hiwonder_Scarlett]

Hi there,

Thank you for your patience. Please check whether the robot’s wiring is correct and verify whether the lidar configuration in the software tool is correctly set. If possible, please record a short video showing your wiring setup and confirming whether the correct lidar configuration is selected in the tool.

We look forward to your reply.

[Pbinu]

Hello, how do I access the tool settings, is it in the app?
Also I do not have permission to post videos on here

[Hiwonder_Scarlett]

Hello,

The tool is pre-installed in the robot system image. You need to access the system via remote desktop software to use it. For the Jetson Orin NX, you can use the NoMachine remote software. Please follow this tutorial to install it: NoMachine Installation Tutorial.

Regarding the video, you can upload it to your Google Drive and share the link with us.

We look forward to your reply.

[Pbinu]

I’m still confused as to how I can access tool settings I don’t see much in no machine:

Here is the link to the wiring video:

IMG_6523.MOV

[Pbinu]

Hello! I kinda need this to work soon so i would appreciate some kinda solution soon if possible

[lunix0x]

Hi.

I’ve faced this kind of issue on mentor pi t1 (raspberry pi 5). In my case the root cause were undervoltage — I powered up the platform with type-C power bank

Check dmesg output, may be you just need to give enough power (f.e. plug off other devices from usb ports).

Check dmesg output in any curious situations with any devices in Linux.

[Pbinu]

Hello,

I powered up the robot with the provided charger from hiwonder and it sits at 12volts which i think is the maximum charge so i dont think it’s that. How do i access tool settings tho?

[lunix0x]

Anyway check the dmesg output.

[Pbinu]

how do i do that?

[lunix0x]

Open terminal or connect via ssh and then ‘sudo dmesg’. You’ll see huge number of lines, search for errors and lidar driver entries.