OPC UA to BACnet and Modbus Gateway: Protocol Translation for BMS Integration

Kepware BACnet/IP driver configuration

Channel settings (Connectivity > BACnet/IP Ethernet):
  Network adapter: 192.168.10.5 (Kepware server OT NIC)
  UDP port: 47808 (BAC0 — standard BACnet/IP port)
  BACnet device instance: 1001 (Kepware gateway identity on BACnet network)
  BBMD address: 192.168.10.1 (router acting as BBMD for cross-subnet discovery)
  BBMD UDP port: 47808
  Foreign device registration: enabled (for devices on other subnets)

Auto-discovery:
  Tools > Device Discovery > BACnet/IP
  Scan range: all subnets registered on BBMD
  Result: discovered 47 BACnet devices with object counts
  Import: select all → creates Kepware device entries with all objects

COV subscription (preferred over polling):
  Device property > Subscriptions > Use COV: Enabled
  Lifetime: 3600 seconds (re-subscribe hourly)
  COV increment for Analog Values: 0.5 (only report if change > 0.5 units)
  Fallback poll rate (if COV not supported): 5000 ms

Kepware Modbus TCP tag configuration

Channel: Modbus TCP/IP Ethernet
  Network adapter: 192.168.10.5
  Port: 502 (standard Modbus TCP port)
  Request timeout: 1000 ms
  Failure count before error: 3

Device: Schneider_PM5100
  IP address: 192.168.10.21
  Unit ID (slave address): 1
  Scan rate: 1000 ms (1 second)

Tags (imported from Schneider PM5100 register map):
  Tag name            | Address        | Data type | Scaling
  ActivePower_Total   | 400593 (HR593) | Float (4B) | ×1 → kW
  ActiveEnergy_Import | 400001 (HR001) | DWord (4B) | ×0.1 → kWh
  Voltage_L1_N        | 400003 (HR003) | Float (4B) | ×1 → V
  Current_L1          | 400013 (HR013) | Float (4B) | ×1 → A
  PowerFactor_Total   | 400085 (HR085) | Float (4B) | ×1 (dimensionless)
  Frequency           | 400073 (HR073) | Float (4B) | ×1 → Hz

# Tag addressing format for Kepware Modbus driver:
# Holding Register 40001 → address "400001" or "4:1"
# Input Register 30001   → address "300001" or "3:1"
# Coil 1                 → address "000001" or "0:1"
# Discrete Input 10001   → address "100001" or "1:1"

UaExpert — connection and verification steps

1. Add server:
   Server menu > Add > Advanced > Enter URL:
   opc.tcp://192.168.10.50:4840
   Security policy: Basic256Sha256
   Message security mode: SignAndEncrypt
   Authentication: Certificate (browse to client_cert.pem + client_key.pem)

2. First connection — certificate exchange:
   UaExpert generates a self-signed client cert on first run
   Server will show certificate as "untrusted" initially
   On Kepware: OPC UA Configuration > Trusted Clients > Move cert to Trusted
   On UaExpert: OPC UA > Manage Certificates > Trust the server cert

3. Browse address space:
   Expand Root > Objects > (your channel name) > (device name)
   Locate BACnet tags: PXC_01 > AnalogInput_1 > Present_Value
   Locate Modbus tags: Schneider_PM5100 > ActivePower_Total

4. Read values:
   Double-click any Variable node to open Data Monitor
   Verify values match expected engineering units and range
   Check StatusCode column — should show "Good (0x00000000)"
   StatusCode "Bad_NoCommunication" → check BACnet/Modbus connectivity from Kepware

5. Create subscription:
   Data Access View panel (bottom): drag Variable nodes from address space
   Set PublishingInterval 1000 ms
   Watch values update in real time — confirms subscription pipeline is working

6. Test write (writable tags only):
   Right-click Variable node > Write Value
   Enter test value within EU range
   Verify change reflected on BACnet device Present_Value
   Note: writes on Kepware require the connecting client to have write permission in UA role

OPC Publisher — publishednodes.json for Kepware

// publishednodes.json — defines which OPC UA nodes to publish to Azure IoT Hub
[
  {
    "EndpointUrl": "opc.tcp://192.168.10.50:4840",
    "UseSecurity": true,
    "OpcAuthenticationMode": "UsernamePassword",
    "OpcAuthenticationUsername": "azure-publisher",
    "OpcAuthenticationPassword": "<from keyvault>",
    "OpcNodes": [
      {
        "Id": "ns=2;s=Channel1.PXC_01.AnalogInput_1.Present_Value",
        "DisplayName": "AHU01_SupplyAirTemp",
        "OpcPublishingInterval": 10000,
        "OpcSamplingInterval": 5000,
        "HeartbeatInterval": 60
      },
      {
        "Id": "ns=2;s=Channel1.Schneider_PM5100.ActivePower_Total",
        "DisplayName": "MainMeter_ActivePower_kW",
        "OpcPublishingInterval": 5000,
        "OpcSamplingInterval": 2000
      },
      {
        "Id": "ns=2;s=Channel1.Schneider_PM5100.ActiveEnergy_Import",
        "DisplayName": "MainMeter_Energy_kWh",
        "OpcPublishingInterval": 60000,
        "OpcSamplingInterval": 30000,
        "SkipFirst": true
      }
    ]
  }
]

// Azure IoT Hub receives JSON telemetry:
// {
//   "NodeId": "ns=2;s=Channel1.Schneider_PM5100.ActivePower_Total",
//   "DisplayName": "MainMeter_ActivePower_kW",
//   "Value": { "Value": 47.3, "StatusCode": "Good", "SourceTimestamp": "2025-03-14T10:30:00Z" }
// }