# RPLIDAR A1 — LIDAR Container

ROS 2 container for the Slamtec RPLIDAR A1, using the upstream
[sllidar_ros2](https://github.com/Slamtec/sllidar_ros2) driver cloned at build time.

---

## Architecture

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

---

## How the build works

The [Dockerfile](Dockerfile) clones the upstream driver from GitHub at build time:

```
git clone https://github.com/Slamtec/sllidar_ros2.git
colcon build --packages-select sllidar_ros2
```

To pin to a specific branch or tag, pass `SLLIDAR_REF` as a build arg:

```bash
docker compose build --build-arg SLLIDAR_REF=v2.0.0 lidar
```

---

## Published topics

| Topic | Type | Description |
|---|---|---|
| `/scan` | `sensor_msgs/LaserScan` | 360° laser scan |

## 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](../docker-compose.yml). To use a different port, set
`LIDAR_PORT` in your `.env` file:

```bash
LIDAR_PORT=/dev/ttyUSB1
```