This project enables the DN23E08, an Arduino-based PLC module, to function as a Modbus RTU slave device, allowing it to be integrated into industrial automation systems and controlled remotely via Modbus communication.

Features

Modbus RTU Slave: Implements standard Modbus RTU protocol over RS485
I/O Mapping: Maps DN23E08 inputs/outputs to Modbus registers
Arduino-based: Easy to customize and extend using Arduino IDE

Hardware Requirements

DN23E08 PLC module
Arduino Nano v3.0 (required for DN23E08 operation)
RS485 communication interface
12-24V power supply

Installation

Clone this repository:

git clone https://git.nielsgeens.be/projects/DN23E08_modbus.git
cd DN23E08_modbus

Open the Arduino sketch in Arduino IDE
Install required libraries (if any - check the code for dependencies)
Configure your Modbus settings:
- Slave ID
- Baud rate
- Parity settings
Upload the sketch to your Arduino Nano

Configuration

Edit the configuration parameters in the main sketch:

// Modbus Configuration
#define SLAVE_ID 1          // Modbus slave address
#define BAUD_RATE 9600      // RS485 baud rate
#define PARITY SERIAL_8N1   // Parity settings

Modbus Register Map

Register Type	Address Range	Description
Coils	0x0000-0x0007	Digital outputs (relays)
Discrete Inputs	0x0000-0x0007	Digital inputs (opto-isolated)
Input Registers	0x0000-0x0007	Analog inputs (current/voltage)
Holding Registers	0x0000-0x00FF	Configuration and control registers

Usage

Connect the DN23E08 to your Modbus master via RS485
Configure your Modbus master with the correct slave ID and communication settings
Use standard Modbus function codes to read inputs and write outputs:
- Read Coils (0x01): Read relay output status
- Read Discrete Inputs (0x02): Read digital input status
- Read Input Registers (0x04): Read analog input values
- Write Single Coil (0x05): Control individual relay outputs
- Write Multiple Coils (0x0F): Control multiple relay outputs