ros2_utils

ROS 2 utility nodes for time publication, LiDAR synchronization, and timestamp rewriting.

Package

• Name: ros2_utils
• Build system: ament_cmake

Build

From your workspace root:

colcon build --packages-select ros2_utils
source install/setup.bash

Nodes

clock_publisher_node

Publishes the ROS /clock topic at 100 Hz from the node's clock.

• Publishes:
  • /clock (rosgraph_msgs/msg/Clock)

Run:

ros2 run ros2_utils clock_publisher_node

---

lidar_sync_node

Synchronizes multiple sensor_msgs/msg/PointCloud2 topics to the latest message with timestamp <= /clock + offset, and republishes to <input>/synced.

• Parameters:

  • offset (double, seconds): Time offset applied to /clock when selecting messages. Default: 0.0.
  • lidar_topics (string list): Input topics to synchronize. Default in code: ["/lidar1/points", "/lidar2/points"].

• Subscribes:

  • /clock (rosgraph_msgs/msg/Clock)
  • Each topic in lidar_topics as sensor_msgs/msg/PointCloud2

• Publishes:

  • For each input <topic>, publishes to <topic>/synced (sensor_msgs/msg/PointCloud2)

Example config (config/config.yaml):

lidar_sync_node:
  ros__parameters:
    offset: 0.0
    lidar_topics:
      - "/front/points"
      - "/rear/points"

Run with config:

ros2 run ros2_utils lidar_sync_node --ros-args --params-file $(ros2 pkg prefix ros2_utils)/share/ros2_utils/config/config.yaml

---

time_rewrite_node

Rewrites timestamps for select sensor_msgs/msg/PointCloud2 topics and TF messages to the node's current clock time.

• Subscribes:

  • /control/carla_ros_bridge/points/lidar_left (sensor_msgs/msg/PointCloud2)
  • /control/carla_ros_bridge/points/lidar_rear (sensor_msgs/msg/PointCloud2)
  • /control/carla_ros_bridge/points/lidar_right (sensor_msgs/msg/PointCloud2)
  • /tf_old (tf2_msgs/msg/TFMessage)

• Publishes:

  • /control/carla_ros_bridge/points/lidar_left_fixed (sensor_msgs/msg/PointCloud2)
  • /control/carla_ros_bridge/points/lidar_rear_fixed (sensor_msgs/msg/PointCloud2)
  • /control/carla_ros_bridge/points/lidar_right_fixed (sensor_msgs/msg/PointCloud2)
  • /tf (tf2_msgs/msg/TFMessage)

Run:

ros2 run ros2_utils time_rewrite_node

Notes

• /clock publisher is useful when running with simulated or controlled time.
• lidar_sync_node uses best-effort QoS for /clock and queue size 10 for PointCloud2 topics.