# saltybot_bringup — Sensor Topic Reference

ROS2 Humble | ROS_DOMAIN_ID=42 | DDS: CycloneDDS

---

## rosbridge WebSocket (web dashboard)

The web dashboard connects to ROS2 topics via rosbridge WebSocket on **port 9090**.

```bash
# Start rosbridge (and compressed camera republishers):
ros2 launch saltybot_bringup rosbridge.launch.py

# Or via docker-compose:
docker compose up -d rosbridge
```

**Browser connection (roslibjs):**
```javascript
var ros = new ROSLIB.Ros({ url: 'ws://jetson.local:9090' });
ros.on('connection', () => console.log('connected'));
ros.on('error',      (e) => console.error('error', e));
ros.on('close',      () => console.log('disconnected'));
```

**Whitelisted topics** (configured in `config/rosbridge_params.yaml`):

| Topic | Type | Notes |
|-------|------|-------|
| `/map` | `nav_msgs/OccupancyGrid` | Use `throttle_rate: 5000` (0.2 Hz) |
| `/scan` | `sensor_msgs/LaserScan` | 5.5 Hz, 1440 pts |
| `/tf` | `tf2_msgs/TFMessage` | Use `throttle_rate: 100` (10 Hz) |
| `/tf_static` | `tf2_msgs/TFMessage` | One-shot on connect |
| `/saltybot/imu` | `sensor_msgs/Imu` | 50 Hz, pitch/roll/yaw |
| `/saltybot/balance_state` | `std_msgs/String` | JSON balance controller state |
| `/cmd_vel` | `geometry_msgs/Twist` | Subscribe to monitor Nav2 commands |
| `/person/target` | (custom) | Person tracking target |
| `/person/detections` | (custom) | Person detection results |
| `/camera/front/image_raw/compressed` | `sensor_msgs/CompressedImage` | JPEG 75%, 640×480 |
| `/camera/left/image_raw/compressed` | `sensor_msgs/CompressedImage` | JPEG 75%, 640×480 |
| `/camera/rear/image_raw/compressed` | `sensor_msgs/CompressedImage` | JPEG 75%, 640×480 |
| `/camera/right/image_raw/compressed` | `sensor_msgs/CompressedImage` | JPEG 75%, 640×480 |

**Bandwidth tips:**
- Raw 640×480 YUYV = ~900 KB/frame. rosbridge republishes JPEG-compressed ≈ 15–25 KB/frame.
- Always use `throttle_rate` for cameras in roslibjs (e.g. `throttle_rate: 200` = max 5 fps).
- `/map` is large (~100 KB); use `throttle_rate: 5000` or subscribe only on demand.

**Verify connection:**
```bash
# Check WebSocket is listening
ss -tlnp | grep 9090

# List topics visible to rosbridge
ros2 topic list | grep -E 'map|scan|imu|camera|person|cmd_vel'
```

---

## Build & Run

```bash
# From inside the container (or ros2_ws root on host after sourcing ROS2):
cd /ros2_ws
colcon build --packages-select saltybot_bringup --symlink-install
source install/local_setup.bash

# Sensors only (verify data before SLAM):
ros2 launch saltybot_bringup sensors.launch.py

# Full SLAM stack (saltybot-ros2 docker-compose service uses this):
ros2 launch saltybot_bringup slam.launch.py

# Individual drivers:
ros2 launch saltybot_bringup realsense.launch.py
ros2 launch saltybot_bringup rplidar.launch.py
```

---

## Topic Reference

### RPLIDAR A1M8

| Topic | Type | Rate | Notes |
|-------|------|------|-------|
| `/scan` | `sensor_msgs/LaserScan` | ~5.5 Hz | 360°, 1440 pts/scan, 12m range |

```
angle_min:  -π  (-180°)
angle_max:  +π  (+180°)
range_min:   0.15 m
range_max:  12.00 m
scan_time:  ~0.182 s
frame_id:   laser
```

### Intel RealSense D435i

| Topic | Type | Rate | Notes |
|-------|------|------|-------|
| `/camera/color/image_raw` | `sensor_msgs/Image` | 15 Hz | RGB8, 640×480 |
| `/camera/color/camera_info` | `sensor_msgs/CameraInfo` | 15 Hz | Intrinsics |
| `/camera/depth/image_rect_raw` | `sensor_msgs/Image` | 15 Hz | Z16, 640×480 |
| `/camera/depth/camera_info` | `sensor_msgs/CameraInfo` | 15 Hz | Intrinsics |
| `/camera/aligned_depth_to_color/image_raw` | `sensor_msgs/Image` | 15 Hz | Depth in color frame |
| `/camera/imu` | `sensor_msgs/Imu` | ~200 Hz | Accel + gyro fused (linear_interpolation) |

### TF Tree

```
map
└── odom                        (published by slam_toolbox once moving)
    └── base_link               (robot body frame)
        ├── laser               (RPLIDAR A1M8)  ← static, 10cm above base
        └── camera_link         (RealSense D435i) ← static, 5cm fwd, 15cm up
            ├── camera_depth_frame
            ├── camera_color_frame
            └── camera_imu_frame
```

**Note:** Static TF values in `sensors.launch.py` are placeholders.
Update after physical mount with real measurements.

---

## Verification Commands

```bash
# List all active topics
ros2 topic list

# Check data rates
ros2 topic hz /scan
ros2 topic hz /camera/color/image_raw
ros2 topic hz /camera/imu

# Spot-check data
ros2 topic echo /scan --once
ros2 topic echo /camera/imu --once

# TF tree
ros2 run tf2_tools view_frames
ros2 run tf2_ros tf2_echo base_link laser

# SLAM map topic (after slam.launch.py)
ros2 topic hz /map
ros2 topic echo /map --no-arr   # metadata without raw data flood
```

---

## Troubleshooting

### RPLIDAR not found
```bash
# Check udev symlink
ls -la /dev/rplidar
# If missing, fall back to:
ros2 launch saltybot_bringup rplidar.launch.py serial_port:=/dev/ttyUSB0
# Install udev rule (host, not container):
sudo cp /path/to/jetson/docs/99-saltybot.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules && sudo udevadm trigger
```

### RealSense not detected
```bash
# Check USB3 port (blue port on Nano)
lsusb | grep "8086:0b3a"
# Expected: Bus 002 Device 00X: ID 8086:0b3a Intel Corp. Intel RealSense D435i

# Install udev rules (host, not container):
sudo cp /etc/udev/rules.d/99-realsense-libusb.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules && sudo udevadm trigger
```

### IMU not publishing
```bash
# Verify enable_gyro and enable_accel are true
ros2 param get /camera/camera enable_gyro
ros2 param get /camera/camera enable_accel
# Check unite_imu_method (should be 2)
ros2 param get /camera/camera unite_imu_method
```