RS-485 MODBUS Serial Communication with Arduino as Master

This project establishes a robust serial communication network using an Arduino Uno configured as a MODBUS master device. At the heart of the system is the ModbusMaster library, which allows the Arduino to format and transmit standard MODBUS requests over serial lines. Because standard microcontroller TTL logic levels cannot travel far or survive industrial electrical noise, a MAX-485 TTL to RS-485 converter module translates the Arduino's serial signals into differential RS-485 voltages. Two push buttons connected with 10k resistors serve as local input triggers for the master, allowing users to send specific commands or requests. When the master acts, it communicates over the RS-485 bus to a computer running Witte Software MODBUS slave simulation, or receives queries from it via a USB to RS-485 converter module. To provide immediate visual feedback without relying solely on a PC monitor, a 16x2 LCD display is wired directly to the Arduino. A 10k potentiometer is connected to the LCD contrast pin to ensure crisp legibility of the system status, transmitted commands, and received data. Connecting wires tie the microcontrollers, transceivers, user inputs, and display peripherals together into a cohesive, long-distance industrial communication test bench.