slmm/API.md

SLMM API Documentation

REST API for controlling Rion NL-43/NL-53 Sound Level Meters via TCP and FTP.

Base URL: http://localhost:8000/api/nl43

All endpoints require a unit_id parameter identifying the device.

Device Configuration

Get Device Config

GET /{unit_id}/config

Returns the device configuration including host, port, and enabled protocols.

Response:

{
  "status": "ok",
  "data": {
    "unit_id": "nl43-1",
    "host": "192.168.1.100",
    "tcp_port": 2255,
    "tcp_enabled": true,
    "ftp_enabled": false,
    "web_enabled": false
  }
}

Update Device Config

PUT /{unit_id}/config

Update device configuration.

Request Body:

{
  "host": "192.168.1.100",
  "tcp_port": 2255,
  "tcp_enabled": true,
  "ftp_enabled": false,
  "ftp_username": "admin",
  "ftp_password": "password",
  "web_enabled": false
}

Device Status

Get Cached Status

GET /{unit_id}/status

Returns the last cached measurement snapshot from the database.

Get Live Status

GET /{unit_id}/live

Requests fresh DOD (Display On Demand) data from the device and returns current measurements.

Response:

{
  "status": "ok",
  "data": {
    "unit_id": "nl43-1",
    "measurement_state": "Measure",
    "lp": "65.2",
    "leq": "68.4",
    "lmax": "82.1",
    "lmin": "42.3",
    "lpeak": "89.5",
    "battery_level": "80",
    "power_source": "Battery",
    "sd_remaining_mb": "2048",
    "sd_free_ratio": "50"
  }
}

Stream Live Data (WebSocket)

WS /{unit_id}/live

Opens a WebSocket connection and streams continuous DRD (Display Real-time Data) from the device.

Measurement Control

Start Measurement

POST /{unit_id}/start

Starts measurement on the device.

Stop Measurement

POST /{unit_id}/stop

Stops measurement on the device.

Pause Measurement

POST /{unit_id}/pause

Pauses the current measurement.

Resume Measurement

POST /{unit_id}/resume

Resumes a paused measurement.

Reset Measurement

POST /{unit_id}/reset

Resets the measurement data.

Manual Store

POST /{unit_id}/store

Manually stores the current measurement data.

Device Information

Get Battery Level

GET /{unit_id}/battery

Returns the battery level.

Response:

{
  "status": "ok",
  "battery_level": "80"
}

Get Clock

GET /{unit_id}/clock

Returns the device clock time.

Response:

{
  "status": "ok",
  "clock": "2025/12/24,02:30:15"
}

Set Clock

PUT /{unit_id}/clock

Sets the device clock time.

Request Body:

{
  "datetime": "2025/12/24,02:30:15"
}

Measurement Settings

Get Frequency Weighting

GET /{unit_id}/frequency-weighting?channel=Main

Gets the frequency weighting (A, C, or Z) for a channel.

Query Parameters:

• channel (optional): Main, Sub1, Sub2, or Sub3 (default: Main)

Response:

{
  "status": "ok",
  "frequency_weighting": "A",
  "channel": "Main"
}

Set Frequency Weighting

PUT /{unit_id}/frequency-weighting

Sets the frequency weighting.

Request Body:

{
  "weighting": "A",
  "channel": "Main"
}

Get Time Weighting

GET /{unit_id}/time-weighting?channel=Main

Gets the time weighting (F, S, or I) for a channel.

Query Parameters:

• channel (optional): Main, Sub1, Sub2, or Sub3 (default: Main)

Response:

{
  "status": "ok",
  "time_weighting": "F",
  "channel": "Main"
}

Set Time Weighting

PUT /{unit_id}/time-weighting

Sets the time weighting.

Request Body:

{
  "weighting": "F",
  "channel": "Main"
}

Values:

• F - Fast (125ms)
• S - Slow (1s)
• I - Impulse (35ms)

FTP File Management

Enable FTP

POST /{unit_id}/ftp/enable

Enables FTP server on the device.

Note: FTP and TCP are mutually exclusive. Enabling FTP will temporarily disable TCP control.

Disable FTP

POST /{unit_id}/ftp/disable

Disables FTP server on the device.

Get FTP Status

GET /{unit_id}/ftp/status

Checks if FTP is enabled on the device.

Response:

{
  "status": "ok",
  "ftp_status": "On",
  "ftp_enabled": true
}

List Files

GET /{unit_id}/ftp/files?path=/

Lists files and directories at the specified path.

Query Parameters:

• path (optional): Directory path to list (default: /)

Response:

{
  "status": "ok",
  "path": "/NL43_DATA/",
  "count": 3,
  "files": [
    {
      "name": "measurement_001.wav",
      "path": "/NL43_DATA/measurement_001.wav",
      "size": 102400,
      "modified": "Dec 24 2025",
      "is_dir": false
    },
    {
      "name": "folder1",
      "path": "/NL43_DATA/folder1",
      "size": 0,
      "modified": "Dec 23 2025",
      "is_dir": true
    }
  ]
}

Download File

POST /{unit_id}/ftp/download

Downloads a file from the device via FTP.

Request Body:

{
  "remote_path": "/NL43_DATA/measurement_001.wav"
}

Response: Returns the file as a binary download with appropriate Content-Disposition header.

Error Responses

All endpoints return standard HTTP status codes:

• 200 - Success
• 404 - Device config not found
• 403 - TCP communication is disabled
• 502 - Failed to communicate with device
• 504 - Device communication timeout
• 500 - Internal server error

Error Response Format:

{
  "detail": "Error message"
}

Common Patterns

Terra-view Integration Example

// Get live status from all devices
const devices = ['nl43-1', 'nl43-2', 'nl43-3'];
const statuses = await Promise.all(
  devices.map(id =>
    fetch(`http://localhost:8000/api/nl43/${id}/live`)
      .then(r => r.json())
  )
);

// Start measurement on all devices
await Promise.all(
  devices.map(id =>
    fetch(`http://localhost:8000/api/nl43/${id}/start`, { method: 'POST' })
  )
);

// Download latest files from all devices
for (const device of devices) {
  // Enable FTP
  await fetch(`http://localhost:8000/api/nl43/${device}/ftp/enable`, {
    method: 'POST'
  });

  // List files
  const res = await fetch(`http://localhost:8000/api/nl43/${device}/ftp/files?path=/NL43_DATA`);
  const { files } = await res.json();

  // Download latest file
  const latestFile = files
    .filter(f => !f.is_dir)
    .sort((a, b) => b.modified - a.modified)[0];

  if (latestFile) {
    const download = await fetch(`http://localhost:8000/api/nl43/${device}/ftp/download`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ remote_path: latestFile.path })
    });

    const blob = await download.blob();
    // Process blob...
  }

  // Disable FTP, re-enable TCP
  await fetch(`http://localhost:8000/api/nl43/${device}/ftp/disable`, {
    method: 'POST'
  });
}

Rate Limiting

The NL43 protocol requires ≥1 second between commands to the same device. The API automatically enforces this rate limit.

Notes

• TCP and FTP protocols are mutually exclusive on the device
• FTP uses active mode (requires device to connect back to server)
• WebSocket streaming keeps a persistent connection - limit concurrent streams
• All measurements are stored in the database for quick access via /status endpoint