MergenHub All drivers ship in every installation; there is nothing to buy or enable. Each driver has an Address hints panel in the tag editor and a help page inside the application.
| Driver | Transport | Highlights | Detail page |
|---|---|---|---|
| Modbus | TCP, UDP, RTU/ASCII serial, Ethernet encapsulation | FC01–04 reads, FC05/06/15/16/22 writes, zero/one-based addressing, Modicon 5/6-digit, word/bit order, per-area max block size, one socket per channel | Modbus |
| Siemens S7 | ISO-on-TCP (102) | S7-300/400/1200/1500, DB/M/I/Q/T/C areas, optimised PDU packing, 64-bit types | Siemens S7 |
| OMRON | FINS/TCP, EtherNet/IP CIP | CS/CJ/CP FINS memory areas, NJ/NX symbolic tags (CIP), bit and word access | OMRON |
| DNP3 | TCP | Integrity/event polls, unsolicited, SBO/Direct Operate, Secure Authentication, time sync, file control, redundancy | DNP3 |
| IEC 60870-5-104 | TCP | General interrogation, single/double commands, setpoints, time sync, redundancy, RTU compatibility modes | IEC 104 |
| IEC 61850 | MMS | SCL/ICD import, LN-level reads, control model (SBO/direct), reports, VMD addresses | IEC 61850 |
| MQTT | TCP/TLS | Broker per channel, topic devices, JSON/XML/CSV/key-value payload parsing, discovery, arrival watchdog liveness | MQTT |
| OPC UA client | opc.tcp | Connect to other UA servers (PLC, gateway, another MergenHub); channel = session, device = subscription, browse for tags | — |
| Simulator | — | Ramp, sine, random, static functions for testing screens, alarms and logging without hardware | — |
Choosing timeouts and scan rates
- Start with the driver defaults and the device's documented response time. A scan rate lower than the device round-trip only creates back-pressure.
- Serial and GSM/radio links: longer request timeout (2–5 s), fewer retries, and demand-driven scanning so idle devices do not keep the link busy.
- Large Modbus devices: keep max block size below what the device supports (many RTUs reset above 64 registers).
Writes
Writes are executed immediately, ahead of the scan queue, and are verified: the driver checks the device acknowledged the write (Modbus exception codes, S7 return codes, DNP3/104 command responses). Failed writes are reported to the caller (OPC UA StatusCode / REST error) and logged in the audit log with user and value.
Redundancy and recovery
Every channel runs under a supervisor. Broken sockets are reopened, dead workers are recreated, and quarantine/back-off prevents a flapping device from flooding the log. DNP3 and IEC 104 support dual-address redundancy.
Diagnostics
Select a device › Diagnostics to see the raw frames (TX/RX hex), byte counters and last error. For cache-based protocols (DNP3, 104, 61850) the packet tap shows the real link traffic, not the cached values. See Troubleshooting.