Before any SCADA, MES or analytics project, data has to leave the PLCs. The usual options are an OPC server or gateway that speaks many PLC drivers, an edge platform, or publishing directly to MQTT.
The right choice depends mostly on which PLC families you have, how many sites, and whether the destination is on-premises or in the cloud.
Option 1: OPC servers and gateways
Driver libraries that talk to many PLC families and expose the data as OPC UA (and often MQTT). Examples:
- Kepware KEPServerEX (PTC), listed as connecting to Ignition, AVEVA PI, ThingWorx, WinCC, FactoryTalk View and Canary Historian
- Matrikon OPC UA Tunneller (Honeywell), commonly used to bridge classic OPC DA to OPC UA
- Softing dataFEED (Softing)
Compare them side by side: Kepware vs Matrikon OPC, Kepware vs Softing dataFEED.
Option 2: Edge platforms
Collect, normalize and forward data, sometimes running apps at the edge. Examples:
- Ignition Edge (Inductive Automation)
- Litmus Edge (Litmus)
- Siemens Industrial Edge (Siemens)
- AVEVA Edge (AVEVA)
- Node-RED and FlowFuse for flow-based integration
Comparisons: Ignition Edge vs Litmus Edge, Litmus Edge vs Siemens Industrial Edge, Kepware vs Litmus Edge, Node-RED vs FlowFuse.
Option 3: Publish straight to an MQTT broker
Where edge devices publish when you go the MQTT / Unified Namespace route. Examples: HiveMQ, EMQX, Eclipse Mosquitto, often combined with the Cirrus Link MQTT modules on the Ignition side.
Comparisons: HiveMQ vs EMQX, HiveMQ vs Mosquitto, EMQX vs Mosquitto. If you go this way, it's worth reading up on Sparkplug B before you design your topics.
Questions to answer before choosing
- Which PLC families and protocols must be supported?
- Do you need classic OPC DA tunnelling to OPC UA?
- How will you secure and manage gateways across sites?
- Is the destination a SCADA, a historian, or the cloud?
Vendor capabilities change, so always check each vendor's current documentation for driver and protocol support.
This is a cross-post from PlantWired, a free, vendor-neutral directory of which factory software works with what. The full guide lists every connectivity and edge tool with its documented integrations, and you can subscribe to the newsletter there for new comparisons. Corrections are very welcome in the comments.
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