Modbus TCP IO Module

A flexible Ethernet-based Modbus TCP IO module built on the Wiznet W5500-EVB-Pico board (RP2040). Features a modern web interface for configuration and real-time monitoring.

Features

Network Configuration

• DHCP support with fallback to static IP
• Configurable network settings via web interface
• Custom hostname support
• Real-time IP address display
• Built-in LED indicates Modbus client connection status

IO Capabilities

• Digital Inputs: 8 channels (GP0-GP7)
  • Configurable pullup resistors
  • Input inversion option
  • Latching capability (inputs remain ON until reset)
  • Latch reset via web interface or Modbus
• Digital Outputs: 8 channels (GP8-GP15)
  • Toggle outputs directly from web interface
  • Configurable initial state (ON/OFF at startup)
  • Output inversion option
  • Real-time status updates
• Analog Inputs: 3 channels (GP26-GP28)
  • 12-bit resolution (0-4095)
  • 3.3V reference voltage
  • Values displayed in millivolts (0-3300mV)
  • Real-time trend graphs

Modbus Server

• Protocol: Modbus TCP
• Default Port: 502
• Register Map:
  • 16 Discrete Inputs (Digital Inputs)
  • 16 Coils (Digital Outputs)
    • Coils 0-7: Control digital outputs
    • Coils 100-107: Reset digital input latches
  • 16 Input Registers (Analog Inputs)
  • 16 Holding Registers

Web Interface

• Modern, responsive design
• Live IO status updates
• Interactive digital output control
• Digital input latch reset functionality
• Configuration management
  • Network settings
  • DHCP toggle with sliding switch
  • Hostname configuration
  • IO configuration with table-based layout
    • Digital input pullup, inversion, and latching options
    • Digital output initial state and inversion options
• Status indicators
  • Current IP address
  • Hostname
  • Modbus client connection status
• Analog input trend visualization

Hardware

Board

• Module: Wiznet W5500-EVB-Pico
• Processor: RP2040 (Dual-core ARM Cortex-M0+)
• Ethernet: W5500 with lwIP stack
• Power: USB or PoE (requires PoE module)
• USB: Custom VID/PID for unique device identification

IO Pin Assignments

Digital IO

Function	GPIO Pin	Description
DI1	GP0	Digital Input 1
DI2	GP1	Digital Input 2
DI3	GP2	Digital Input 3
DI4	GP3	Digital Input 4
DI5	GP4	Digital Input 5
DI6	GP5	Digital Input 6
DI7	GP6	Digital Input 7
DI8	GP7	Digital Input 8
DO1	GP8	Digital Output 1
DO2	GP9	Digital Output 2
DO3	GP10	Digital Output 3
DO4	GP11	Digital Output 4
DO5	GP12	Digital Output 5
DO6	GP13	Digital Output 6
DO7	GP14	Digital Output 7
DO8	GP15	Digital Output 8

Analog Inputs

Function	GPIO Pin	ADC Channel	Range
AI1	GP26	ADC0	0-3300mV
AI2	GP27	ADC1	0-3300mV
AI3	GP28	ADC2	0-3300mV

Ethernet Interface

Function	GPIO Pin
CS	GP17
IRQ	GP21
SCK	GP18
MOSI	GP19
MISO	GP16

Development

Environment

• PlatformIO
• Framework: Arduino
• Board: Raspberry Pi Pico
• Core: Earlephilhower's Arduino core

Dependencies

• Arduino Framework
• W5500lwIP Ethernet Library
• ArduinoModbus
• ArduinoJson
• LittleFS for file system operations

Building and Flashing

1. Clone the repository
2. Open in PlatformIO
3. Build and upload to the board

Configuration

Default Network Settings

• DHCP: Enabled
• Fallback Static IP: 192.168.1.10
• Subnet: 255.255.255.0
• Gateway: 192.168.1.1
• Modbus Port: 502

Memory Layout

• Configuration stored in LittleFS
• Version control for config structure
• Automatic migration of settings

Usage

1. Power up the board via USB or PoE
2. Connect to network via Ethernet
3. Access web interface via IP address
4. Configure network settings if needed
5. Configure IO settings as required:
   • Set digital input pullup, inversion, and latching options
   • Configure digital output initial state and inversion options
6. Control digital outputs via web interface or Modbus
7. Monitor inputs and outputs in real-time
8. Reset latched inputs via web interface or by writing to Modbus coils 100-107

Debugging

• Serial debug output (115200 baud)
• Web interface status indicators
• Modbus client connection monitoring
• Built-in LED indicates Modbus client connection