Most of the applications of embedded systems require keypads to take the user inputs, especially in case where an application requires more number of keys. With simple architecture and easy interfacing procedure, matrix keypads are replacing normal push-buttons by offering more inputs to the user with the lesser I/O pins. As a Human Machine Interface (HMI) keypad plays a major role in vital microprocessor and microcontroller based projects and equipments. Therefore, this article gives you a brief idea on matrix keypad interfacing with 8051 microcontroller.
Introduction to Matrix Keypad
A Matrix keypad is the most commonly used input device in many of the application areas like digital circuits, telephone communications, calculators, ATMs, and so on. A matrix keypad consists of a set of push button or switches which are arranged in a matrix format of rows and columns. These keypads are available in configurations like 3×4 and 4×4 based on the application it is implemented for. Internal diagram of this matrix keypad is shown in the below figure.
Matrix Keypad Interfacing with 8051 Microcontroller: