SLMM - Sound Level Meter Manager

Backend API service for controlling and monitoring Rion NL-43/NL-53 Sound Level Meters via TCP and FTP protocols.

Overview

SLMM is a standalone backend module that provides REST API routing and command translation for NL43/NL53 sound level meters. This service acts as a bridge between the hardware devices and frontend applications, handling all device communication, data persistence, and protocol management.

Note: This is a backend-only service. Actual user interfacing is done via SFM/Terra-View frontend applications.

Features

• Device Management: Configure and manage multiple NL43/NL53 devices
• Real-time Monitoring: Stream live measurement data via WebSocket
• Measurement Control: Start, stop, pause, resume, and reset measurements
• Data Retrieval: Access current and historical measurement snapshots
• FTP Integration: Download measurement files directly from devices
• Device Configuration: Manage frequency/time weighting, clock sync, and more
• Rate Limiting: Automatic 1-second delay enforcement between device commands
• Persistent Storage: SQLite database for device configs and measurement cache

Architecture

┌─────────────────┐         ┌──────────────┐         ┌─────────────────┐
│  Terra-View UI  │◄───────►│  SLMM API    │◄───────►│  NL43/NL53      │
│  (Frontend)     │  HTTP   │  (Backend)   │  TCP    │  Sound Meters   │
└─────────────────┘         └──────────────┘         └─────────────────┘
                                    │
                                    ▼
                            ┌──────────────┐
                            │  SQLite DB   │
                            │  (Cache)     │
                            └──────────────┘

Quick Start

Prerequisites

• Python 3.10+
• pip package manager

Installation

1. Clone the repository:

git clone <repository-url>
cd slmm

2. Install dependencies:

pip install -r requirements.txt

Running the Server

# Development mode with auto-reload
uvicorn app.main:app --reload --port 8100

# Production mode
uvicorn app.main:app --host 0.0.0.0 --port 8100

The API will be available at http://localhost:8100

API Documentation

Once running, visit:

• Swagger UI: http://localhost:8100/docs
• ReDoc: http://localhost:8100/redoc
• Health Check: http://localhost:8100/health

Configuration

Environment Variables

• PORT: Server port (default: 8100)
• CORS_ORIGINS: Comma-separated list of allowed origins (default: "*")

Database

The SQLite database is automatically created at data/slmm.db on first run.

Logging

Logs are written to:

• Console output (stdout)
• data/slmm.log file

API Endpoints

Device Configuration

Method	Endpoint	Description
GET	/api/nl43/{unit_id}/config	Get device configuration
PUT	/api/nl43/{unit_id}/config	Update device configuration

Device Status

Method	Endpoint	Description
GET	/api/nl43/{unit_id}/status	Get cached measurement snapshot
GET	/api/nl43/{unit_id}/live	Request fresh DOD data from device
WS	/api/nl43/{unit_id}/stream	WebSocket stream for real-time DRD data

Measurement Control

Method	Endpoint	Description
POST	/api/nl43/{unit_id}/start	Start measurement
POST	/api/nl43/{unit_id}/stop	Stop measurement
POST	/api/nl43/{unit_id}/pause	Pause measurement
POST	/api/nl43/{unit_id}/resume	Resume paused measurement
POST	/api/nl43/{unit_id}/reset	Reset measurement data
POST	/api/nl43/{unit_id}/store	Manually store data to SD card

Device Information

Method	Endpoint	Description
GET	/api/nl43/{unit_id}/battery	Get battery level
GET	/api/nl43/{unit_id}/clock	Get device clock time
PUT	/api/nl43/{unit_id}/clock	Set device clock time
GET	/api/nl43/{unit_id}/results	Get final calculation results (DLC)

Measurement Settings

Method	Endpoint	Description
GET	/api/nl43/{unit_id}/settings	Get all current device settings for verification
GET	/api/nl43/{unit_id}/frequency-weighting	Get frequency weighting (A/C/Z)
PUT	/api/nl43/{unit_id}/frequency-weighting	Set frequency weighting
GET	/api/nl43/{unit_id}/time-weighting	Get time weighting (F/S/I)
PUT	/api/nl43/{unit_id}/time-weighting	Set time weighting

Sleep Mode

Method	Endpoint	Description
POST	/api/nl43/{unit_id}/sleep	Put device into sleep mode
POST	/api/nl43/{unit_id}/wake	Wake device from sleep
GET	/api/nl43/{unit_id}/sleep/status	Get sleep mode status

FTP File Management

Method	Endpoint	Description
POST	/api/nl43/{unit_id}/ftp/enable	Enable FTP server on device
POST	/api/nl43/{unit_id}/ftp/disable	Disable FTP server on device
GET	/api/nl43/{unit_id}/ftp/status	Get FTP server status
GET	/api/nl43/{unit_id}/ftp/files	List files on device
POST	/api/nl43/{unit_id}/ftp/download	Download file from device

For detailed API documentation and examples, see API.md.

Project Structure

slmm/
├── app/
│   ├── __init__.py          # Package initialization
│   ├── main.py              # FastAPI application and startup
│   ├── routers.py           # API route definitions
│   ├── models.py            # SQLAlchemy database models
│   ├── services.py          # NL43Client and business logic
│   └── database.py          # Database configuration
├── data/
│   ├── slmm.db              # SQLite database (auto-created)
│   ├── slmm.log             # Application logs
│   └── downloads/           # Downloaded files from devices
├── templates/
│   └── index.html           # Simple web interface (optional)
├── manuals/                 # Device documentation
├── API.md                   # Detailed API documentation
├── COMMUNICATION_GUIDE.md   # NL43 protocol documentation
├── NL43_COMMANDS.md         # Command reference
├── requirements.txt         # Python dependencies
└── README.md                # This file

Database Schema

NL43Config Table

Stores device connection configuration:

• unit_id (PK): Unique device identifier
• host: Device IP address or hostname
• tcp_port: TCP control port (default: 80)
• tcp_enabled: Enable/disable TCP communication
• ftp_enabled: Enable/disable FTP functionality
• ftp_username: FTP authentication username
• ftp_password: FTP authentication password
• web_enabled: Enable/disable web interface access

NL43Status Table

Caches latest measurement snapshot:

• unit_id (PK): Unique device identifier
• last_seen: Timestamp of last update
• measurement_state: Current state (Measure/Stop)
• lp: Instantaneous sound pressure level
• leq: Equivalent continuous sound level
• lmax: Maximum sound level
• lmin: Minimum sound level
• lpeak: Peak sound level
• battery_level: Battery percentage
• power_source: Current power source
• sd_remaining_mb: Free SD card space (MB)
• sd_free_ratio: SD card free space ratio
• raw_payload: Raw device response data

Protocol Details

TCP Communication

• Uses ASCII command protocol over TCP
• Enforces ≥1 second delay between commands to same device
• Two-line response format:
  • Line 1: Result code (R+0000 for success)
  • Line 2: Data payload (for query commands)

FTP Communication

• Uses active mode FTP (requires device to connect back)
• TCP and FTP are mutually exclusive on the device
• Credentials configurable per device

Data Formats

DOD (Data Output Display): Snapshot of current display values DRD (Data Real-time Display): Continuous streaming data DLC (Data Last Calculation): Final stored measurement results

Example Usage

Configure a Device

curl -X PUT http://localhost:8100/api/nl43/meter-001/config \
  -H "Content-Type: application/json" \
  -d '{
    "host": "192.168.1.100",
    "tcp_port": 2255,
    "tcp_enabled": true,
    "ftp_username": "admin",
    "ftp_password": "password"
  }'

Start Measurement

curl -X POST http://localhost:8100/api/nl43/meter-001/start

Get Live Status

curl http://localhost:8100/api/nl43/meter-001/live

Verify Device Settings

curl http://localhost:8100/api/nl43/meter-001/settings

This returns all current device configuration:

{
  "status": "ok",
  "unit_id": "meter-001",
  "settings": {
    "measurement_state": "Stop",
    "frequency_weighting": "A",
    "time_weighting": "F",
    "measurement_time": "00:01:00",
    "leq_interval": "1s",
    "lp_interval": "125ms",
    "index_number": "0",
    "battery_level": "100%",
    "clock": "2025/12/24,20:45:30",
    "sleep_mode": "Off",
    "ftp_status": "On"
  }
}

Stream Real-time Data (JavaScript)

const ws = new WebSocket('ws://localhost:8100/api/nl43/meter-001/stream');

ws.onmessage = (event) => {
  const data = JSON.parse(event.data);
  console.log('Live measurement:', data);
};

Download Files via FTP

# Enable FTP
curl -X POST http://localhost:8100/api/nl43/meter-001/ftp/enable

# List files
curl http://localhost:8100/api/nl43/meter-001/ftp/files?path=/NL43_DATA

# Download file
curl -X POST http://localhost:8100/api/nl43/meter-001/ftp/download \
  -H "Content-Type: application/json" \
  -d '{"remote_path": "/NL43_DATA/measurement.wav"}' \
  --output measurement.wav

# Disable FTP
curl -X POST http://localhost:8100/api/nl43/meter-001/ftp/disable

Integration with Terra-View

This backend is designed to be consumed by the Terra-View frontend application. The frontend should:

1. Use the config endpoints to register and configure devices
2. Poll or stream live status for real-time monitoring
3. Use control endpoints to manage measurements
4. Download files via FTP endpoints for analysis

See API.md for detailed integration examples.

Troubleshooting

Connection Issues

• Verify device IP address and port in configuration
• Ensure device is on the same network
• Check firewall rules allow TCP/FTP connections
• Verify RX55 network adapter is properly configured on device

Rate Limiting

• API automatically enforces 1-second delay between commands
• If experiencing delays, this is normal device behavior
• Multiple devices can be controlled in parallel

FTP Active Mode

• Ensure server can accept incoming connections from device
• FTP uses active mode (device connects back to server)
• May require firewall configuration for data channel

WebSocket Disconnects

• WebSocket streams maintain persistent connection
• Limit concurrent streams to avoid device overload
• Connection will auto-close if device stops responding

Development

Running Tests

# Add test commands when implemented
pytest

Database Migrations

# Migrate existing database to add FTP credentials
python migrate_add_ftp_credentials.py

# Set FTP credentials for a device
python set_ftp_credentials.py <unit_id> <username> <password>

Contributing

This is a standalone module kept separate from the SFM/Terra-View codebase. When contributing:

1. Maintain separation from frontend code
2. Follow existing API patterns and error handling
3. Update API documentation for new endpoints
4. Ensure rate limiting is enforced for device commands

License

[Specify license here]

Related Documentation

• API.md - Complete API reference with examples
• COMMUNICATION_GUIDE.md - NL43 protocol details
• NL43_COMMANDS.md - Device command reference
• manuals/ - Device manufacturer documentation

Support

For issues and questions:

• Backend API issues: This repository
• Frontend/UI issues: Terra-View repository
• Device protocol questions: See COMMUNICATION_GUIDE.md