EIP Ground Truth

Overview

A comprehensive EtherNet/IP communication adapter for the ESP32-P4 microcontroller, integrating sensor support, Modbus TCP, and web-based configuration. The device serves as a bridge between EtherNet/IP networks and local I/O, sensors, and other industrial automation components.

This project implements a full-featured EtherNet/IP adapter device on the ESP32-P4 platform using the OpENer open-source EtherNet/IP stack. The device provides IMU-based ground-truth measurements for counterbalance applications, calculating roll, pitch, ground angle, and opposed-cylinder pressures.

Hardware Platform

This project targets ESP32-P4 with Ethernet connectivity:

• Microcontroller: ESP32-P4 (Espressif)
• Ethernet PHY: IP101 (or compatible)
• I2C Devices: Optional IMU sensor (MPU6050 or LSM6DS3)
• GPIO Configuration: Ethernet: MDC, MDIO, PHY Reset (configurable); I2C: SDA, SCL (configurable, defaults GPIO7/GPIO8)

IMU Integration

The device supports 6-axis motion sensor support with automatic fallback:

• MPU6050: Primary sensor - Accelerometer-based orientation calculation
• LSM6DS3: Fallback sensor - Sensor fusion (complementary filter) combining accelerometer and gyroscope for accurate orientation

IMU Capabilities

Both sensors provide the following measurements:

• Roll and Pitch: Orientation angles from horizontal (degrees)
• Ground Angle: Angle from vertical (degrees)
• Cylinder Pressures: Calculated pressures for two opposed cylinders based on orientation, tool weight, tip force, and cylinder bore

Calculation Precision

All sensor calculations use 32-bit float precision (IEEE 754 single precision):

• Ground angle calculation: acos(cos(roll) × cos(pitch)) for both MPU6050 and LSM6DS3 (correct 3D angle formula)
• Typical accuracy: ±0.04° for ground angle calculations (sufficient for industrial sensor applications)
• Values are scaled by 10000 for angles and 1000 for pressures when stored in assembly data

EtherNet/IP Assembly Structure

The device exposes three EtherNet/IP assembly instances:

Input Assembly (Instance 100) - 32 Bytes

Contains IMU sensor data and other input data:

Offset	Size	Field Name	Description
0-3	4	DINT 0	Roll angle (degrees × 10000)
4-7	4	DINT 1	Pitch angle (degrees × 10000)
8-11	4	DINT 2	Ground angle from vertical (degrees × 10000)
12-15	4	DINT 3	Bottom cylinder pressure (PSI × 1000)
16-19	4	DINT 4	Top cylinder pressure (PSI × 1000)
20-31	12	Reserved	Available space for other sensor data

Note: Byte offset is configurable (0-12) to avoid conflicts with other sensors.

Output Assembly (Instance 150) - 32 Bytes

Contains control commands and configuration parameters:

• Byte 29: Cylinder bore diameter (scaled by 100: 0.01-2.55 inches)
• Byte 30: Tool weight (0-255 lbs)
• Byte 31: Tip force (0-255 lbs)
• Bytes 0-28: Control commands and other output data

Configuration Assembly (Instance 151) - 10 Bytes

A 10-byte configuration assembly is available for device-specific configuration parameters.

Modbus TCP Server

Standard Modbus TCP/IP server (port 502) provides additional protocol access:

• Input Registers 0-15: Map to Input Assembly 100 (32 bytes = 16 registers)
• Holding Registers 100-115: Map to Output Assembly 150 (32 bytes = 16 registers)
• Holding Registers 150-154: Map to Configuration Assembly 151 (10 bytes = 5 registers)

All assembly data is stored in little-endian format (Modbus converts to big-endian for transmission).

Network Configuration

The device includes RFC 5227 compliant Address Conflict Detection (ACD):

• RFC 5227 compliant static IP assignment (implemented in application layer)
• ACD probe sequence runs before IP assignment (deferred assignment)
• Natural ACD state machine flow
• EtherNet/IP conflict reporting in TCP/IP Interface Object Attribute #11
• User LED indication (GPIO27): blinks during normal operation, solid on ACD conflict

Web-Based Configuration Interface

Essential device management via web interface:

• Network Configuration: Set IP address, netmask, gateway, DNS (DHCP/Static IP modes)
• Firmware Updates: Upload firmware updates via web browser (OTA)
• REST API: All other device configuration, monitoring, and status information available via REST API

Access the web interface at http://<device-ip>/ after the device has obtained an IP address.

Sensor Configuration

Configuration via web API:

• Enable/disable sensor
• Configure byte offset (0-12) to avoid conflicts with other sensors
• View real-time readings (roll, pitch, ground angle, pressures)
• Calibrate sensor (LSM6DS3 only)

The device automatically detects and uses MPU6050 if available, otherwise falls back to LSM6DS3.

Software Requirements

• ESP-IDF: Version 5.5.1 or compatible
• Python: 3.x (for build scripts)
• CMake: 3.16 or higher

Connection Types

The device supports standard EtherNet/IP connection types:

• Exclusive Owner: Bidirectional I/O connection
• Input Only: Unidirectional input connection
• Listen Only: Unidirectional input connection (multicast)