IO-Link — Smart Sensor Master
IO-Link (IEC 61131-9) is a single-wire bidirectional serial communication standard that connects industrial sensors/actuators to a master. The master connects to higher-level systems (PLC, SCADA, Edge) via PROFINET / EtherNet/IP / Modbus TCP / OPC UA and forwards process data (PD), identification data (ISDU), and events.
The IOLINK driver in this gateway is a stub. IO-Link uses a 3-wire serial (24V / GND / C/Q) physical layer, so a PC cannot generate or decode the signals directly.
Recommended integration path: register the IO-Link master's upper-level interface (PROFINET / Modbus TCP / EtherNet/IP / OPC UA / REST) using another PlantPulse driver.
Why master hardware is required
IO-Link devices are inherently reachable only through a master. The master aggregates multiple IO-Link sensors — typically 8 or 16 ports — and exposes the results over industrial Ethernet.
| Master category | Representative products | Upper-level interface |
|---|---|---|
| 8-port PROFINET master | ifm AL1100 / AL1xxx, Balluff BNI008x | PROFINET, OPC UA |
| 8-port EtherNet/IP master | Balluff BNI EIP, ifm AL13xx | EtherNet/IP, REST |
| 8-port Modbus TCP master | Pepperl+Fuchs ICE3-8IOL, Murr Cube67 | Modbus TCP |
| Hybrid (multi-protocol) | Turck TBEN-S2, Banner R90C | PROFINET / EIP / Modbus / REST |
Recommended integration path
| Interface provided by the master | PlantPulse driver to use | Page |
|---|---|---|
| OPC UA Companion Spec for IO-Link (cleanest) | OPCUA | OPC-UA |
| Modbus TCP | MODBUS | Modbus TCP |
| EtherNet/IP | EIP | AB EtherNet/IP |
| PROFINET | PROFINET | Siemens Profinet |
| JSON REST | HTTP | HTTP Push |
On masters that support the OPC Foundation IO-Link Companion Spec (recent firmware from ifm / Balluff, for example), each port's PD/ISDU is exposed as OPC UA nodes. Registering them directly with the PlantPulse OPCUA driver lets you poll per-port sensor values, which is the cleanest approach.
Example register map when registering via Modbus TCP (ifm AL1100)
The register map differs for every master, so read the vendor manual carefully.
| Data | Typical location (e.g. ifm AL1100) | PlantPulse notation |
|---|---|---|
| Port 1 PD-In (Process Data In) | Holding Register 0x1000+ | 4096 (decimal) |
| Port 2 PD-In | 0x1100+ | 4352 |
| Per-port status bit | 0x0000 area | 0 + bit number |
| Per-port PD-Out (write) | 0x2000+ | 8192 |
stub registration (for reference)
| Input field | What to enter |
|---|---|
| IP address | (not used) |
| Port | (not used) |
| Automatic collection | Disabled recommended |
Common problems
| Symptom | Possible cause | Resolution |
|---|---|---|
| No values after registering IOLINK | stub driver | Re-register with OPCUA / MODBUS / EIP instead |
| PD values received over Modbus look corrupted | 16-bit / 32-bit endianness | Apply DW / RDW conversion in the format helper |
| OPC UA node tree is too deep | Standard structure of the Companion Spec | Register aliases only for frequently used nodes |
| Stale values after a sensor disconnect | Differences in the master's fail-safe policy | Change fail-safe from Last value to Zero in the master settings |
| RFID reader response is corrupted | ISDU is a byte array — truncated by the 16-bit Modbus unit | Use the OPC UA Companion Spec or the master's REST API |
Next steps
- Obtain the register map or OPC UA node tree from the IO-Link master manual
- See the OPC-UA registration / Modbus registration / EIP registration pages
- Technical background: IO-Link driver (advanced)