Hello friends! Today, we are going to interface a 4×4 keypad with an 8051 microcontroller in Proteus. We will read the pressed key through the AT89C51 and display its character on a 20×4 LCD, so we can see exactly what the program receives. This project builds on our LCD interfacing tutorial . The display remains our output device, while the keypad becomes an input device. Together, they form the basic user interface for a calculator, menu, password entry system or small control panel. I will explain the keypad matrix before discussing the program. We will then add debouncing, prevent one held button from producing repeated characters and keep typed text within the upper two LCD rows. The original simulation, images and download are preserved for reference. Figure: Original keypad characte ...