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Modbus Devices

Configure Modbus TCP devices to acquire data from PLCs, drives, meters, and other industrial equipment.

Modbus Devices List Screenshot placeholder: List of configured Modbus devices

What is a Modbus Device?

A Modbus Device represents a physical piece of equipment on your network that communicates using the Modbus TCP protocol. Examples: - PLCs (Programmable Logic Controllers) - VFDs (Variable Frequency Drives) - Power meters - Temperature controllers - Flow meters - Custom Modbus devices

Adding a Device

Add Modbus Device Form Screenshot placeholder: Add device configuration form

  1. Navigate to Devices → Add Device
  2. Fill in the configuration:

Basic Settings

  • Device Name: Descriptive name (e.g., "Pump 1 VFD")
  • Device ID: Unique identifier for Sparkplug (e.g., "Pump_01")
  • Edge Node: Select the parent edge node
  • Enabled: Enable/disable this device

Connection Settings

  • Primary Host: IP address or hostname
  • Port: Modbus port (default: 502)
  • Slave/Unit ID: Modbus slave address (1-247)
  • Timeout: Connection timeout in milliseconds (default: 5000)
  • Retry Count: Number of retry attempts (default: 3)

Advanced Settings

  • Secondary Host (optional): Failover IP address
  • Frame Delay: Delay between reads in milliseconds

  • Zero-Based Addressing: Use 0-based register addressing

  • Click Test Connection

  • Click Save

Testing Connection

Test Connection Screenshot placeholder: Connection test result

Before saving, verify the device is reachable: 1. Click Test Connection 2. Gateway attempts to connect and read a register 3. Result shows success or error

Common connection errors: - Connection timeout: Check IP address and network - Connection refused: Verify port number - Invalid slave ID: Check Modbus slave/unit ID - No response: Device may be offline or busy

Device Status

Device Status Screenshot placeholder: Device connection status indicators

Each device shows real-time status: - 🟢 Connected: Successfully polling - 🟡 Connecting: Attempting connection - 🔴 Disconnected: Cannot reach device - 🟠 Degraded: Intermittent communication

Host Redundancy

Host Redundancy Screenshot placeholder: Primary/secondary host configuration

Configure primary and secondary hosts for high availability: 1. Set Primary Host - Normal operation 2. Set Secondary Host - Automatic failover 3. Gateway monitors primary health 4. Automatically switches to secondary if primary fails 5. Auto-reconnects to primary when available

See Host Redundancy for details.

Device Operations

Start/Stop Polling

Start Stop Device Screenshot placeholder: Device control buttons

  • Start: Begin polling tags
  • Stop: Stop polling (maintains configuration)
  • Poll Once: Single poll for testing

Edit Device

  1. Click device name or Edit button
  2. Modify settings
  3. Click Save
  4. Device automatically restarts if running

Delete Device

  1. Click Delete button
  2. Confirm deletion

Warning

Deleting a device removes all associated tags and tag groups. This cannot be undone.

Using Templates

Apply Template Device Tag Templates Device tag template configuration

Speed up configuration with device templates: 1. When creating device, select Template 2. Choose appropriate template 3. All tags automatically created 4. Customize as needed

See Device Templates for details.

Monitoring

Connection Statistics

Device Statistics Dashboard Navigator root dashboard view

View real-time metrics: - Total queries sent - Successful responses - Failed queries - Success rate - Average response time - Last error

Logs

Access device-specific logs: - Connection events - Poll cycles - Errors and warnings - Tag read failures

Best Practices

  • ✅ Use descriptive device names
  • ✅ Configure host redundancy for critical devices
  • ✅ Set appropriate timeouts based on network
  • ✅ Group similar tags by poll rate
  • ✅ Use templates for standard equipment
  • ✅ Monitor connection statistics
  • ✅ Test connections before deployment

Next Steps