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PLC Communication Details (EtherNet/IP)

The OV20i vision system supports real-time communication with EtherNet/IP-based PLCs. This guide explains how to configure cyclic I/O connections, map data structures, and use Overview’s Node-RED tools to access both global and ROI-level inspection results.

note

For basic connection instructions, see Connect to PLC (EtherNet/IP, PROFINET).

Overview​

The OV20i functions as an EtherNet/IP adapter, while your PLC operates as a scanner (or master). Once configured, the devices exchange structured data every cycle using a compact and predictable format.

Supported Features​

  • Cyclic I/O communication - 20–10,000 ms cycle time support
  • Data throughput - Up to 256 bytes in each direction
  • Custom data handling - Read/write Node-RED data as part of the active recipe

Input Assembly (OV20i → PLC)​

The input assembly contains data sent from the OV20i to the PLC on every cycle. This includes system status, inspection results, recipe information, and optional ROI breakdowns.

Byte and bit layout of the OV20i input assembly

Output Assembly (PLC → OV20i)​

The output assembly contains control data sent from the PLC to the OV20i. You can use it to trigger inspections, change recipes, or pass in custom parameters.

Byte and bit layout of the OV20i output assembly

Timing and Handshake Behavior​

EtherNet/IP Triggering Timing Diagram

Custom Data Support​

The OV20i can accept or return additional custom data as part of your Node-RED flow.

PLC → OV20i​

  • Write external flags, thresholds, or counters to influence logic in Node-RED

OV20i → PLC​

  • Return calculated values, measurements, timestamps, or conditional outputs

Custom data fits into the extended portion of the assemblies, starting after the core signals and recipe info.

ROI Result Breakdown (Classification Recipes Only)​

For classification recipes, you can expose per-ROI results to the PLC using Overview’s custom Node-RED node: Format data for PLC.

How it works:​

  • Placed between All Blocks Output Data and Send Data to PLC in the Node-RED flow

Format Data for PLC Node-RED Flow Example

  • Automatically populates a structured ROI region starting at byte 16 in the input assembly

  • Supports up to 4 ROIs per inspection

  • Each ROI includes:

    • ROI ID
    • Pass/fail bit
    • Confidence score
    • Reserved bytes for future use
warning

Format Data for PLC Node works with Classification Recipes Only.

Byte and bit layout of the OV20i output assembly