x/eipRead component: v0.37.0+ Reads controller tags in batch from Rockwell Automation Allen-Bradley ControlLogix/CompactLogix/Micro820 PLCs over the EtherNet/IP (CIP) protocol. Only CIP devices are supported; PCCC protocol devices such as PLC5, SLC, and MicroLogix are not supported.

Additional extension library required: rulego-components-iot (opens new window)

Configuration

Field	Type	Description	Default
server	string	PLC host address (host only); port 44818 is built in by gologix, e.g. 127.0.0.1; supports ref://nodeId to reuse an existing connection in the chain	127.0.0.1
slot	int	CPU slot on the backplane; auto-generates the CIP path (e.g. 1,0)	0
path	string	Optional CIP path override, e.g. 1,0; empty = auto-generated from slot	None
timeout	int	Request timeout in seconds	5
points	array	Default points table; points in msg.Data take precedence	None

Points fields:

Field	Type	Description
name	string	Point name
addr	string	Controller tag name (CIP tag), e.g. MyTag, MyDB.Temperature
type	string	Tag data type, required (gologix Read requires a concrete type pointer); see options below
scale	float	Optional scale multiplier (default 1); conversion formula eng = raw*scale + offset
offset	float	Optional offset (default 0)

Point Fields

addr: Controller tag name. Supports controller-scoped tags (e.g. Temperature), struct members (e.g. MyDB.Temperature), array elements (e.g. MyArray[0]), and program-scoped tags (e.g. Program:MainProgram.Tag).

type: Tag data type, required. Because gologix's Read requires a concrete Go type pointer (Go is statically typed), the type cannot be inferred from the tag and must be specified explicitly by the caller.

Supported values (case-insensitive):

Category	Accepted aliases
Boolean	BOOL
8-bit integer	BYTE, SINT, USINT
16-bit integer	INT, INT16, UINT, WORD, UINT16
32-bit integer	DINT, INT32, UDINT, DWORD, UINT32
64-bit integer	LINT, INT64, ULINT, UINT64
32-bit float	REAL, FLOAT
64-bit float	LREAL, DOUBLE
String	STRING

Output

Read results are written back to msg.Data (JSON array) with a unified contract and routed through the Success chain. One object per point, with the following fields:

Field	Type	Description
name	string	Point name
address	string	Tag name (equals the configured/input addr)
value	any	Read value
type	string	Data type (uppercase)
quality	string	Quality: good or bad
timestamp	string	Acquisition time (RFC3339 format)

Example data:

[
  {
    "name": "temperature",
    "address": "MyDB.Temperature",
    "value": 23.5,
    "type": "REAL",
    "quality": "good",
    "timestamp": "2026-07-23T10:00:00.123456789Z"
  }
]

A failure on a single point does not affect other points (that point is marked quality=bad); only when all points fail is it treated as a connection-level error and routed to the Failure chain.

Input (Optional)

msg.Data may carry a points list in JSON, using the same format as the points configuration; when non-empty it takes precedence over the configured points, which is useful for dynamic collection scenarios:

[
  {"name": "temp", "addr": "MyDB.Temperature", "type": "REAL"}
]

Features

1. Periodic collection: Pair with an endpoint/schedule endpoint upstream as a trigger; maintain points in the points configuration.
2. Template variables: Point fields (name/addr/type/value) support ${msg.xx} / ${metadata.xx} placeholders.
3. Dynamic points: Points in msg.Data take precedence over configured points.
4. Same-chain connection pool: Other nodes in the same chain can borrow the EtherNet/IP connection already established by this node via ref://nodeId, avoiding duplicate connections.
5. Auto-reconnect & retry: On connection-level failure (all tags fail) the node reconnects and retries automatically, up to 3 times.

Relation Type

• Success: On successful execution, the message is sent to the Success chain.
• Failure: On failed execution, the message is sent to the Failure chain.

Example

{
  "ruleChain": {
    "name": "eip-read-demo",
    "root": true,
    "debugMode": false
  },
  "metadata": {
    "endpoints": [],
    "nodes": [
      {
        "type": "x/eipRead",
        "name": "read tags",
        "debugMode": false,
        "configuration": {
          "server": "192.168.1.10",
          "slot": 0,
          "timeout": 5,
          "points": [
            {"name": "temperature", "addr": "MyDB.Temperature", "type": "REAL"},
            {"name": "running", "addr": "MyDB.Running", "type": "BOOL"}
          ]
        }
      }
    ],
    "connections": []
  }
}