MCP IoT Gateway

The MCP IoT Gateway is Conduit's multi-protocol industrial translator. It uses the Model Context Protocol (MCP) to dynamically connect to multiple industrial protocols through a single gateway, eliminating the need for separate translators per protocol.

Overview

The MCP IoT Gateway supports:

• Modbus TCP/RTU: PLCs, sensors, meters, and field instruments
• Siemens S7: S7-300, S7-400, S7-1200, and S7-1500 PLCs
• EtherNet/IP: Rockwell/Allen-Bradley ControlLogix and CompactLogix
• BACnet/IP: Building automation systems, HVAC, smart buildings

How It Works

Unlike traditional translators that connect to a single protocol, the MCP IoT Gateway:

1. Receives queries via MCP Mesh Transport from the Control Plane
2. Dynamically routes to the appropriate protocol handler
3. Translates queries to native protocol operations (Modbus register reads, S7 data block reads, etc.)
4. Returns normalized results in a standard format

Prerequisites

1. Network Access: TCP connectivity to target industrial devices
2. Device Documentation: Register maps, data block definitions, or point lists
3. MCP Gateway Service: Running as a Docker container or native process

Configuration

Basic Configuration

translator:
  type: mcp-iot-gateway
  name: gateway-plant-1

  controlPlane:
    url: nats://nats:4222
    apiKey: ${GATEWAY_API_KEY}

  protocols:
    modbus:
      enabled: true
    s7:
      enabled: true
    ethernet-ip:
      enabled: true
    bacnet:
      enabled: true

Modbus Devices

devices:
  - name: vfd-pump-room
    protocol: modbus
    connection:
      type: tcp
      host: 192.168.1.50
      port: 502
      unitId: 1
    registers:
      - name: Tank1_Temperature
        address: 40001
        type: holding
        dataType: float32
        byteOrder: big-endian
        unit: "°F"

      - name: Tank1_Level
        address: 40003
        type: holding
        dataType: uint16
        scale: 0.1
        unit: "%"

      - name: Pump1_Running
        address: 00001
        type: coil
        dataType: bool

Siemens S7 Devices

devices:
  - name: s7-line1
    protocol: s7
    connection:
      host: 192.168.1.100
      rack: 0
      slot: 1
      type: s7-1500
    dataBlocks:
      - db: 1
        name: ProcessData
        variables:
          - name: Temperature
            offset: 0
            type: real
          - name: Pressure
            offset: 4
            type: real
          - name: Running
            offset: 8.0
            type: bool

EtherNet/IP Devices

devices:
  - name: compactlogix-line2
    protocol: ethernet-ip
    connection:
      host: 192.168.1.200
      slot: 0
    tags:
      - name: Line2_Speed
        path: "Program:MainProgram.Line2_Speed"
        type: real
      - name: Line2_Count
        path: "Program:MainProgram.Line2_Count"
        type: dint

BACnet Devices

devices:
  - name: hvac-building1
    protocol: bacnet
    connection:
      host: 192.168.1.150
      port: 47808
      deviceId: 1234
    objects:
      - name: Zone1_Temperature
        type: analog-input
        instance: 1
        property: present-value
      - name: AHU1_Status
        type: binary-input
        instance: 10
        property: present-value

Polling Configuration

Group-Based Polling

pollGroups:
  - name: fast
    interval: 100 # ms
    devices: [vfd-pump-room, s7-line1]
    tags: [Temperature, Pressure, Running]

  - name: normal
    interval: 1000
    devices: [compactlogix-line2]
    tags: [Speed, Count]

  - name: slow
    interval: 10000
    devices: [hvac-building1]
    tags: [Zone1_Temperature, AHU1_Status]

Query Translation

NQE queries are routed to the MCP IoT Gateway when they reference devices connected through it:

Show temperature for Tank 1 over the last hour

The gateway:

1. Identifies Tank1_Temperature is on the Modbus device vfd-pump-room
2. Reads holding register 40001 (float32)
3. Returns the scaled, engineering-unit value

For historical queries, the gateway maintains a local buffer of recent readings that can be queried.

Connection Management

Reconnection

connection:
  reconnect:
    enabled: true
    interval: 5000 # ms
    maxAttempts: -1 # Infinite

  timeout:
    connect: 5000 # ms
    read: 3000

Troubleshooting

Connection Issues

Modbus Connection Refused

• Verify IP and port
• Check firewall rules
• Confirm device is powered on and unit ID is correct

S7 Communication Error

• Verify rack/slot configuration
• Check PLC is in RUN mode
• Confirm network route to PLC

EtherNet/IP Timeout

• Verify slot number
• Check controller is online
• Confirm CIP routing path

Data Issues

Incorrect Values

• Check byte order configuration (Modbus)
• Verify data type matches device documentation
• Check scaling configuration

Example Deployment

version: "3.8"
services:
  conduit-mcp-gateway:
    image: conduit/mcp-iot-gateway:latest
    environment:
      - CONDUIT_CONTROL_PLANE=nats://nats:4222
      - GATEWAY_API_KEY=${GATEWAY_API_KEY}
    volumes:
      - ./config/gateway.yaml:/etc/conduit/gateway.yaml
    networks:
      - plant-network
    # Ensure access to industrial network
    extra_hosts:
      - "plc1:192.168.1.50"
      - "plc2:192.168.1.100"

Next Steps

• Splunk Translator - Connect to Splunk
• MQTT Translator - Subscribe to MQTT
• Architecture - How translators work