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Edge Gateway

Modbus to OPC UA Server

The gateway as an OPC UA server: every routed tag a variable that SCADA and MES clients browse and subscribe to.

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The data flow

SOURCE TO OPC UA CLIENTSModbus devicePLC · meter · driveEdge Gatewaythe runtime on your devicepolls · decodes · scalesholds the present valueOPC UA Serverin the gatewayns=<namespace>;s=<Device>.<Tag>value, unit, status code, timestampclients browse, read, subscribe

A server-style output: nothing is sent anywhere. The gateway holds the present value of every tag routed to it, and clients come and read or subscribe. A tag that goes BAD is served with a bad status code, never with a stale number.

In the editor

Edge LogicPump house✓ Saved · v3DeployFilter nodes…PLC & INDUSTRIALModbusSiemens S7Allen-Bradley (CIP)…TRANSFORMSScaleDeadbandExpression…LOGIC & ROUTINGCondition / RouteJoinInject / TriggerOUTPUTMQTT outHTTP outSQL out…GATEWAYModbus converterMain meterModbus · 192.168.1.20every 1 s · 6 tagsSCADAOPC UA Server outopc.tcp://gateway:4840SCADALISTEN ADDRESS0.0.0.0PORT4840ADVERTISED HOST NAMEgateway.plant.localNAMESPACE URIurn:modbuslogic:gateway:tagsENDPOINT SECURITYNone
Source straight into OPC UA Server out; there is nothing to filter on the way to a server.

OPC UA Server out holds the listen address and port, the advertised host name that goes into the endpoint URL clients are given, the server and namespace names, and the endpoint security: none, Sign & Encrypt with Basic256Sha256, or both, with the certificate and key as files on the device. Clients connect anonymously.

A server-style output holds the present value of every tag routed to it, so a Deadband, Rate limit, Debounce, Batch or Store & forward on the way to it has nothing to act on; the compiler leaves them off the route and validation says so. A Condition does apply: it decides which values reach the server at all. See Logic and routing nodes.

Test it with the Modbus Simulator

You do not need the PLC to try this flow. The Modbus Simulator answers as a Modbus slave on your own PC, with registers that move, so the whole path from polling to the output can be watched before any hardware is involved.

  1. Start the Simulator and add a slave: Modbus TCP, bind host set to this PC's LAN address (the prefilled one), port 1502, unit ID 1. Add a few holding registers, say 40001–40010 as FLOAT32 or INT16 in random mode so the values change, and press Start.
  2. In the editor, set the source node's host to that address, port 1502, unit ID 1, and the same addresses and data types. Poll interval 1s is fine.
  3. Deploy the design to a device on the same network, or to this very PC: the Edge Gateway Console installs on a laptop as readily as on an edge computer, and the gateway polls the Simulator over the LAN.
  4. The Simulator's request log shows the gateway's reads arriving: function code 03, the start address and quantity, once per poll interval. Neighbouring registers arrive as one read.
  5. Open the endpoint (opc.tcp://<gateway>:4840) in any OPC UA client, UaExpert being the usual free one, browse the namespace and subscribe to a variable: it moves as the Simulator's register does, with a source timestamp from the poll.
THE TEST BENCHModbus Simulatora slave on your PC · port 1502registers in random moderequest log shows each readEdge Gatewaythe runtime on your devicepolls every secondthe live view shows valuesThe outputon the same PC or elsewhere

Registers in fixed mode make a deadband or a condition easy to exercise: change a value by hand and watch what is, and is not, published. A register set to a value the Simulator refuses (uncheck Fill unmapped and read an address that is not there) shows what a BAD quality looks like at the output. The Simulator's own page has the rest.

From design to device

THE SAME FOUR STEPS FOR EVERY FLOWValidateon the design pageInstallthe console on the deviceDevice codeentered on the design pageBundlegiven to the console
  1. Validate. On the design page, Run validation. The editor's rules, the tag document and the runtime binary itself check the design; every issue names its node. Details: Validating a design.
  2. Install. From the Devices panel download the installer for the device's platform (Windows x64, Linux x64 or Linux ARM64). Windows: extract and run Edge-Gateway-Console.exe from an administrator terminal. Linux (Debian, Ubuntu, Raspberry Pi OS): sudo dpkg -i the .deb, then sudo edge-gateway-console. It shows the device code. Details: Installing on the device.
  3. Device code. Enter it in the Devices panel, choose a trial or one of your purchased licences, and press Download activation bundle: one small zip with the design and a licence bound to that machine, sealed so only that machine can open it. Details: Downloading.
  4. Bundle. Give the zip to the console (drag it onto the program, pass its path, or put it beside the program and run it again; a USB stick is fine for a device without internet). It opens the bundle with its own code, installs the runtime as a service and starts it. The device never contacts the site. Details: Activation and the licence.

The console then opens the gateway's web view in a browser (on a device without a desktop it prints the address instead) and stays attached with the live view: devices up or down, values as they change, what was published, and the log.

  • The live view shows the OPC UA server as listening, with the number of connected clients.
  • A client browsing the endpoint finds one folder per device and one variable per tag, with data type, engineering unit and status.

Ctrl-C leaves the gateway running as a service. Run edge-gateway-console again at any time: it shows the service, the licence, every device and destination with what to check, the web view, and the live log. Running covers the data directory, secrets and the diagnostics.

Modbus to OPC UA Server · Edge Gateway documentation | Modbus Logic