omron-ethernet-ip

Node.js client for Omron NJ/NX series PLCs over EtherNet/IP using CIP symbolic tag messaging.

Existing Node.js EtherNet/IP libraries target Allen-Bradley controllers and do not handle Omron's CIP variant correctly. This library implements the Omron wire format directly, so tags can be read by name from an Omron NJ/NX PLC.

Status

Early development. Working today:

• TCP connection and EtherNet/IP session registration
• Reading scalar tags by name: BOOL, SINT/INT/DINT/LINT, USINT/UINT/UDINT/ULINT, REAL, LREAL
• Writing scalar tags by name (the CIP type is auto-discovered, or can be given)
• Reading and writing STRING tags
• Reading a whole array in one request (BOOL bit-packed, and scalar element types)
• Listing all variables published on the PLC
• Importing a Sysmac Studio variable export into a FUXA device JSON (parseSysmacTags, and the tools/sysmac-to-fuxa.js converter)
• Structure-member and array-element addressing in the request path (e.g. Recipe.Setpoint, Conveyor[3])

Not yet implemented: whole-structure decoding, per-tag type metadata.

Install

No runtime dependencies (uses the Node.js net module). Node.js >= 14.

npm install omron-ethernet-ip

Usage

const { OmronEipClient } = require('omron-ethernet-ip');

(async () => {
  const client = new OmronEipClient({ host: '192.168.250.1' });
  await client.connect();                  // TCP + RegisterSession

  const r = await client.readTag('PV_Temper_ETC1');
  console.log(`${r.name} = ${r.value} [${r.typeName}]`);

  await client.writeTag('SET_Timer_V1', 30); // CIP type discovered automatically

  client.close();
})();

Try it

node examples/read-scalar.js <plc-ip> <tag-name>

Run the offline checks

npm test

These verify the protocol byte encoding without a PLC. Interoperability with real hardware must be confirmed with the live example.

Notes

• The PLC must be reachable on TCP port 44818.
• The variable must be published in the PLC's global variable table, otherwise the controller returns CIP status 0x04 (path segment error).
• The EtherNet/IP wire format was cross-referenced with the Omron W506 manual, the ODVA CIP specification, and the aphyt Python library (GPLv2) as a protocol reference. This is an independent implementation.

License

MIT