Building OPC UA integration topology

Field layer (field protocols)
  BACnet/IP: Siemens PXC200, Distech EC-Net controllers
  Modbus TCP: Schneider PM5xxx energy meters, Janitza UMG 96
  KNX/IP: WEINZIERL KNX IP Interface 731
  M-Bus: heat meters, gas meters (IEC 62056)

  ↓ protocol drivers (inside BMS or gateway)

OPC UA Server layer
  Siemens DESIGO CC with OPC UA server module
    └── exposes BACnet objects as OPC UA Variables
    └── exposes alarm conditions as OPC UA AlarmCondition
  Beckhoff TwinCAT OPC UA Server
    └── exposes PLC variables directly from ADS runtime
  Kepware KEPServerEX
    └── multi-protocol gateway (BACnet + Modbus → OPC UA)

  ↓ opc.tcp:// or opc.wss://

Clients (standard OPC UA)
  Energy management platform (Schneider PME, EcoStruxure)
  SCADA / MES (Ignition, WinCC OA, Aveva)
  Cloud connector (Azure IoT OPC Publisher, AWS Greengrass)
  Analytics / dashboards (Grafana OPC UA plugin, Power BI)

IEC 62541-100 building information model structure

BuildingType (ns=2;s=Building_Alpha_Tower)
├── SiteType (ns=2;s=Site_Riga_01)
│   ├── BuildingStoreyType (ns=2;s=Floor_03)
│   │   ├── SpaceType (ns=2;s=Office_3A)  ← IFC IfcSpace mapping
│   │   │   ├── AirTemperature [Variable, Float, °C]
│   │   │   ├── CO2Concentration [Variable, UInt16, ppm]
│   │   │   └── OccupancyState [Variable, Boolean]
│   │   └── SpaceType (ns=2;s=Meeting_3B)
│   └── BuildingStoreyType (ns=2;s=Floor_04)
├── HVACSystemType (ns=2;s=AHU_Main_01)  ← IFC IfcSystem mapping
│   ├── SupplyAirTemperature [Variable, Float, °C]
│   ├── ExhaustAirTemperature [Variable, Float, °C]
│   ├── HeatingCoilValve [Variable, Byte, 0–100%]
│   ├── CoolingCoilValve [Variable, Byte, 0–100%]
│   ├── FanSpeed [Variable, UInt16, RPM]
│   └── OperatingMode [Variable, Enum: Off/Auto/Heating/Cooling/Night]
└── EnergyMeterType (ns=2;s=MainMeter_kWh)  ← IEC 62056 meter
    ├── ActiveEnergyImport [Variable, Double, kWh]
    ├── ActivePower [Variable, Float, kW]
    └── Timestamp [Variable, DateTime]

OPC UA PubSub — Kepware to MQTT broker configuration

# Kepware IoT Gateway Plugin — OPC UA PubSub to MQTT

Agent type: MQTT Client (Publisher)
Broker URL: mqtts://iot.yourdomain.com:8883
Client ID: kepware-building-01
TLS: enabled (CA cert + client cert for mutual TLS)

Published datasets (JSON encoding, UA-JSON):
  Topic: building/01/hvac/ahu01
  Payload (DataSetMessage, JSON):
  {
    "MessageId": "uuid-xxx",
    "PublisherId": "kepware-building-01",
    "DataSetWriterId": 1001,
    "Timestamp": "2025-03-14T10:30:00Z",
    "Payload": {
      "SupplyAirTemperature": { "Value": 18.4, "StatusCode": "Good", "SourceTimestamp": "..." },
      "FanSpeed":             { "Value": 1450, "StatusCode": "Good" },
      "HeatingCoilValve":     { "Value": 72,   "StatusCode": "Good" }
    }
  }

  Topic: building/01/energy/main-meter
  PublishingInterval: 60000 ms
  QueueSize: 1 (latest value only)

asyncua — connect, browse, read, subscribe

import asyncio
from asyncua import Client
from asyncua.crypto.security_policies import SecurityPolicyBasic256Sha256
from asyncua.ua import MessageSecurityMode

class SubHandler:
    """Callback invoked for each subscription notification."""
    def datachange_notification(self, node, val, data):
        print(f"  DataChange: {node} = {val}  status={data.monitored_item.Value.StatusCode}")

async def main():
    url = "opc.tcp://192.168.10.50:4840/freeopcua/server/"

    async with Client(url=url) as client:
        # --- Security: Sign + Encrypt, Basic256Sha256, X.509 cert ---
        await client.set_security(
            SecurityPolicyBasic256Sha256,
            certificate="client_cert.pem",
            private_key="client_key.pem",
            server_certificate="server_cert.pem",
            mode=MessageSecurityMode.SignAndEncrypt,
        )

        print("Connected. Server namespaces:")
        for i, ns in enumerate(await client.get_namespace_array()):
            print(f"  ns={i}: {ns}")

        # --- Browse Objects root ---
        objects = client.get_objects_node()
        children = await objects.get_children()
        for child in children:
            name = await child.read_browse_name()
            print(f"  Object: {name.Name}")

        # --- Read a specific variable by NodeId ---
        temp_node = client.get_node("ns=1;s=AHU_01.SupplyAirTemperature")
        temp_value = await temp_node.read_value()
        print(f"Supply air temperature: {temp_value:.1f} °C")

        # --- Read EngineeringUnits property ---
        eu = await temp_node.read_data_value()
        print(f"StatusCode: {eu.StatusCode}")

        # --- Subscribe to multiple nodes ---
        handler = SubHandler()
        subscription = await client.create_subscription(500, handler)  # 500 ms publishing
        nodes = [
            client.get_node("ns=1;s=AHU_01.SupplyAirTemperature"),
            client.get_node("ns=1;s=AHU_01.FanSpeed"),
            client.get_node("ns=1;s=Meter.kWh"),
        ]
        await subscription.subscribe_data_change(nodes)

        print("Subscribed. Waiting 30 seconds for notifications...")
        await asyncio.sleep(30)
        await subscription.delete()

asyncio.run(main())