Logix Connector

Overview

The Logix connector enables communication with Allen-Bradley/Rockwell Automation PLCs using the EtherNet/IP (CIP) protocol. This includes ControlLogix, CompactLogix, and other Logix-based controllers.

Connector Types:

• LogixReader - Read tags from Logix PLCs
• LogixWriter - Write tags to Logix PLCs

Features

• ✅ EtherNet/IP (CIP) protocol support
• ✅ TCP and UDP transport options
• ✅ Multiple data types (BOOL, SINT, INT, DINT, LINT, REAL, LREAL, STRING)
• ✅ Configurable slot routing
• ✅ Polling-based data acquisition

Basic Configuration

Logix Reader

{
  "type": "LogixReader",
  "config": {
    "endpoint": "192.168.1.100:44818",
    "protocol": "TCP",
    "pollingRate": 1000,
    "slot": 0
  },
  "variables": [
    {
      "key": "temperature",
      "tagName": "MainProgram:Temperature",
      "dataType": "REAL"
    },
    {
      "key": "motor_running",
      "tagName": "MainProgram:Motor_Running",
      "dataType": "BOOL"
    }
  ]
}

Logix Writer

{
  "type": "LogixWriter",
  "config": {
    "endpoint": "192.168.1.100:44818",
    "protocol": "TCP",
    "slot": 0
  },
  "variables": [
    {
      "key": "setpoint",
      "tagName": "MainProgram:Setpoint",
      "dataType": "REAL"
    },
    {
      "key": "enable",
      "tagName": "MainProgram:Enable",
      "dataType": "BOOL"
    }
  ]
}

Configuration Parameters

Connection Config

Parameter	Type	Required	Description
endpoint	string	✅	PLC address (host:port). Default port is 44818
protocol	string	✅	Transport protocol: TCP or UDP
pollingRate	integer	✅ (Reader)	Polling interval in milliseconds
slot	integer	❌	Slot number for chassis routing (default: 0)

Variable Config

Parameter	Type	Required	Description
key	string	✅	Output key name in data payload
tagName	string	✅	PLC tag name (e.g., Program:TagName)
dataType	string	✅	Data type of the tag

Data Types

Boolean

{
  "key": "motor_status",
  "tagName": "Motor_Running",
  "dataType": "BOOL"
}

Integer

// 8-bit signed integer (-128 to 127)
{"dataType": "SINT"}

// 16-bit signed integer (-32768 to 32767)
{"dataType": "INT"}

// 32-bit signed integer
{"dataType": "DINT"}

// 64-bit signed integer
{"dataType": "LINT"}

Floating Point

// 32-bit float
{"dataType": "REAL"}

// 64-bit float (double precision)
{"dataType": "LREAL"}

String

{
  "key": "product_name",
  "tagName": "Product_Name",
  "dataType": "STRING"
}

Slot Routing

For ControlLogix systems with multiple slots, specify the slot number:

{
  "endpoint": "192.168.1.100",
  "protocol": "TCP",
  "slot": 2
}

The slot parameter configures the CIP routing path to reach the target controller.

Common Use Cases

1. Process Monitoring

Read process variables from a ControlLogix PLC:

{
  "type": "LogixReader",
  "config": {
    "endpoint": "192.168.1.100:44818",
    "protocol": "TCP",
    "pollingRate": 500,
    "slot": 0
  },
  "variables": [
    {
      "key": "temperature",
      "tagName": "Process:Temperature_PV",
      "dataType": "REAL"
    },
    {
      "key": "pressure",
      "tagName": "Process:Pressure_PV",
      "dataType": "REAL"
    },
    {
      "key": "flow_rate",
      "tagName": "Process:Flow_Rate",
      "dataType": "REAL"
    },
    {
      "key": "valve_position",
      "tagName": "Process:Valve_Position",
      "dataType": "INT"
    }
  ]
}

2. Setpoint Control

Write setpoints to a PLC:

{
  "type": "LogixWriter",
  "config": {
    "endpoint": "192.168.1.100:44818",
    "protocol": "TCP",
    "slot": 0
  },
  "variables": [
    {
      "key": "temp_setpoint",
      "tagName": "Process:Temperature_SP",
      "dataType": "REAL"
    },
    {
      "key": "pressure_setpoint",
      "tagName": "Process:Pressure_SP",
      "dataType": "REAL"
    },
    {
      "key": "auto_mode",
      "tagName": "Process:Auto_Mode",
      "dataType": "BOOL"
    }
  ]
}

3. Production Counters

Read production statistics:

{
  "type": "LogixReader",
  "config": {
    "endpoint": "192.168.1.100:44818",
    "protocol": "TCP",
    "pollingRate": 5000
  },
  "variables": [
    {
      "key": "total_count",
      "tagName": "Production:Total_Count",
      "dataType": "DINT"
    },
    {
      "key": "good_count",
      "tagName": "Production:Good_Count",
      "dataType": "DINT"
    },
    {
      "key": "reject_count",
      "tagName": "Production:Reject_Count",
      "dataType": "DINT"
    },
    {
      "key": "batch_id",
      "tagName": "Production:Batch_ID",
      "dataType": "STRING"
    }
  ]
}

Troubleshooting

Connection Failed

Solutions:

• Verify PLC IP address and port (default: 44818)
• Check network connectivity and firewall rules
• Ensure PLC is in Run mode
• Verify Ethernet module is properly configured

Tag Read/Write Failed

Solutions:

• Verify tag name is correct (case-sensitive)
• Check tag scope (controller vs program scope)
• Ensure data type matches PLC tag type
• Verify tag is not protected or read-only (for writes)

Invalid Data Type

Solutions:

• Match data type exactly to PLC tag definition
• Use correct type for arrays (read individual elements)
• Check for UDT (User Defined Type) - not directly supported

Slot Routing Error

Solutions:

• Verify slot number matches controller location
• Check chassis configuration
• Ensure communication module is in correct slot

Best Practices

1. Use Descriptive Tag Names: Match PLC naming conventions
2. Appropriate Polling Rate: Balance data freshness with network load
3. Group Related Tags: Organize variables by function or area
4. Handle Connection Loss: Implement retry logic in workflows
5. Test in Offline Mode: Verify tag names before connecting to production PLCs

Related Connectors

• OPC UA - Alternative industrial protocol
• Modbus - Legacy industrial protocol
• Siemens S7 - Siemens PLC communication
• InfluxDB - Store PLC data in time-series database