Custom Matrix Keypad Module

This project involves the development of a compact, sealed, and intelligent keypad module designed for industrial automation environments. The system integrates tactile rubber buttons, LED-based visual indication feedback, audible feedback through a buzzer, and dual communication interfaces for seamless connectivity with Siemens PLC systems. The keypad front face is built using a single molded rubber keypad sheet with tactile feedback beneath each button. The internal electronics are fully enclosed with a protective back cover, ensuring resistance to dust, moisture, environmental variation, and mechanical stress. A total of 35 keys are arranged in a structured matrix configuration (7×5), scanned by an STM32-based controller (Nucleo - STM32H723ZG ) to ensure fast and accurate detection with software-based debounce and event handling. Each key includes three dedicated indicator LEDs, enabling multi-mode status visualization. LED control is managed using a daisy-chained array of TLC59282 industrial-grade constant-current LED drivers, ensuring consistent brightness, low power consumption, and minimal thermal impact even in sealed operation. The system further includes a buzzer to provide audible feedback or alarm signaling. Communication to the PLC is achieved through RS-485 (SN65HVD75) (Modbus-RTU or equivalent protocol) and Ethernet (via the onboard Nucleo PHY interface). This dual-interface architecture ensures compatibility with the Siemens S7-1200 PLC. Power is derived from a 24 V DC industrial source, regulated down through protected internal power stages to provide stable 5 V and 3.3 V rails for logic, LEDs, and peripherals. The internal components are selected for high-temperature tolerance (≥85 °C), ensuring long-term reliability in enclosed, low-ventilation environments. Key Technical Features • 35 tactile rubber keys with mechanical actuation • 105 LED indicators (3 per key) using TLC59282 LED drivers • 7×5 hardware key matrix scanning via STM32 GPIOs • Sealed enclosure for harsh environments (dust, moisture, vibration) • Audible buzzer feedback with GPIO/PWM control • RS-485 industrial communication interface with fail-safe biasing and termination • Native Ethernet connectivity via STM32 Nucleo board • 24 V industrial input with protected and regulated power stages (5 V and 3.3 V rails) • Low current LED design optimized for visibility and thermal control • Industrial temperature-rated components for sealed operation

Proje No: 40075633