ros-raspbot-v2/lidar

RPLIDAR A1 — LIDAR Container

ROS 2 container for the Slamtec RPLIDAR A1, built on top of a fork of the official sllidar_ros2 driver.

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Architecture

                        ┌──────────────────────────────────────┐
                        │  sllidar_ros2 (rplidar_node)         │
                        │                                      │
                        │  serial 115200 baud                  │
                        │  angle_compensate = true             │
                        │  scan_mode = Sensitivity             │
                        │         ▼                            │
                        │   /dev/ttyUSB0 ──────> RPLIDAR A1   │
                        │                                      │
 /scan          <───────│  LaserScan @ ~10 Hz                  │
 (sensor_msgs/          │  360° scan, range 0.15–12 m          │
  LaserScan)            │                                      │
                        └──────────────────────────────────────┘

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How the build works

The driver source lives in lidar/sllidar_ros2/ as a git subtree of this repository. The Dockerfile copies it directly from the workspace — no network access is required at build time.

Workspace repo                Docker build
──────────────────────────    ──────────────────────────────────────────
lidar/sllidar_ros2/      ───> COPY lidar/sllidar_ros2/ src/sllidar_ros2/
(git subtree of fork)         colcon build --packages-select sllidar_ros2

The upstream fork is maintained at:

https://github.com/m5p3nc3r/sllidar_ros2

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Development workflow

Pulling upstream changes into the workspace

git subtree pull --prefix=lidar/sllidar_ros2 sllidar_ros2 main --squash

This fetches the latest commits from the fork, squashes them into a single merge commit, and updates lidar/sllidar_ros2/ in the workspace.

Making local changes

Edit files inside lidar/sllidar_ros2/ as normal, then commit them to the workspace repo:

git add lidar/sllidar_ros2/
git commit -m "lidar: describe the change"

Pushing changes back to the fork

git subtree push --prefix=lidar/sllidar_ros2 sllidar_ros2 main

This replays only the commits that touched lidar/sllidar_ros2/ and pushes them to the fork's main branch.

First-time setup on a fresh clone

The subtree files are committed in the workspace repo, so a git clone of this repo is all that is needed — there is no separate step to initialise the subtree. To be able to pull or push to the fork later, add the remote:

git remote add sllidar_ros2 https://github.com/m5p3nc3r/sllidar_ros2.git

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Changes relative to upstream

File	Change
src/sllidar_node.cpp	/scan publisher QoS made configurable via scan_qos_depth (int) and scan_qos_reliability (best_effort|reliable) parameters. Defaults to best_effort, depth 2 — required for Nav2 / RViz2 compatibility.
launch/sllidar_a1_launch.py	Exposes scan_qos_depth and scan_qos_reliability as launch arguments.

The upstream Slamtec repository is at:

https://github.com/slamtec/sllidar_ros2

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Published topics

Topic	Type	Description
/scan	sensor_msgs/LaserScan	360° laser scan, BEST_EFFORT QoS, depth 2

Device

The RPLIDAR A1 connects via USB serial at /dev/ttyUSB0 (default), 115200 baud. The container receives access to that device via the devices mapping in docker-compose.yml. To use a different port, set LIDAR_PORT in your .env file:

LIDAR_PORT=/dev/ttyUSB1