KC868-A16 EtherNet/IP

Overview

A proof-of-concept port of the OpENer EtherNet/IP stack to ESP32 with Ethernet, targeting the Kincony KC868-A16 Ethernet I/O controller. The firmware exposes 16 relay outputs, 16 opto-isolated digital inputs, and 4 analog inputs over EtherNet/IP implicit messaging, suitable for PLC integration and industrial automation.

This implementation demonstrates the feasibility of running industrial EtherNet/IP communication protocols on cost-effective, widely available microcontroller platforms. The device acts as an EtherNet/IP adapter, supporting both explicit messaging (for configuration and diagnostics) and implicit I/O connections (for real-time data exchange).

Hardware Platform

The Kincony KC868-A16 is an ESP32-based Ethernet I/O controller with the following specifications:

• Microcontroller: ESP32 (Espressif)
• Ethernet: LAN8720 PHY with RMII interface (PHY address 0)
• Digital Outputs: 16 relay outputs via PCF8574 I/O expanders (active-low)
• Digital Inputs: 16 opto-isolated inputs via PCF8574 I/O expanders (active-low)
• Analog Inputs: 4 channels via ESP32 ADC
• I2C Configuration: SDA GPIO4, SCL GPIO5 @ 400 kHz

Analog Input Configuration

The device provides four analog input channels with the following mapping:

• A1 (INA1): 4–20 mA current input
• A2 (INA2): 0–5 V voltage input
• A3 (INA3): 0–5 V voltage input
• A4 (INA4): 4–20 mA current input

All analog inputs are sampled at 12-bit resolution (0–4095 counts) with 11 dB attenuation.

EtherNet/IP Assembly Structure

The device implements two EtherNet/IP assemblies for I/O data exchange:

Output Assembly (Instance 150)

2-byte output assembly used to send relay control data from the EtherNet/IP scanner (PLC) to the device:

Byte	Bits	Outputs	Description
0	0–7	Y01–Y08	Relay outputs 1–8
1	0–7	Y09–Y16	Relay outputs 9–16

Note: Bit value 1 = relay on, 0 = relay off. Outputs are active-low at the PCF8574, so the firmware inverts bits when writing to the expander.

Input Assembly (Instance 100)

10-byte input assembly used to send digital input states and analog readings from the device back to the EtherNet/IP scanner:

Offset	Size	Inputs	Description
0	1	X01–X08	Opto-isolated inputs 1–8
1	1	X09–X16	Opto-isolated inputs 9–16
2	2	A1 (INA1)	4–20 mA raw ADC count (little-endian)
4	2	A2 (INA2)	0–5 V raw ADC count (little-endian)
6	2	A3 (INA3)	0–5 V raw ADC count (little-endian)
8	2	A4 (INA4)	4–20 mA raw ADC count (little-endian)

Implementation Notes:

• Digital inputs are active-low; the firmware reports a bit as 1 when the physical signal is low.
• Analog values are 12-bit (0–4095 counts), little-endian byte order.
• Analog input mapping: A1 (INA1) and A4 (INA4) are 4–20 mA inputs; A2 (INA2) and A3 (INA3) are 0–5 V inputs.

Software Stack & Tooling

This project uses the following software components:

• ESP-IDF: Version 5.5.1 or later
• OpENer: Open-source EtherNet/IP stack for I/O adapter devices
• lwIP: Lightweight TCP/IP stack for embedded systems
• Web UI: Minimal HTTP interface for IP configuration (/api/ipconfig)

Device Identity

The device presents the following identity information to EtherNet/IP scanners:

• Vendor ID: 55512 (AG Sweeney Automation)
• Product Name: KC868-A16
• Device Type: Generic Device
• Product Code: 1

Connection Types

The device supports standard EtherNet/IP connection types:

• Exclusive Owner: Bidirectional I/O connection (Output Assembly 150 → Input Assembly 100)
• Input Only: Unidirectional input connection (Input Assembly 100 only)
• Listen Only: Unidirectional multicast input connection (Input Assembly 100 only)

Network Configuration

The device supports both DHCP and static IP configuration:

• DHCP: Automatically obtains IP address, gateway, and DNS from network DHCP server
• Static IP: Manually configured IP address, netmask, gateway, and DNS servers
• NVS Storage: Network configuration is saved to NVS flash and persists across reboots

A minimal web interface is provided at http://<device-ip>/api/ipconfig for network configuration and diagnostics.