Any kind of computing system has basically three parts namely input unit, processing unit and output unit. In case of a Personal Computer the standard input units are the mouse and the keyboard and the output units is the LCD or CRT Monitor. The input and the outputs are controlled by the Central Processing Unit (CPU) which has a powerful processor inside it. When it comes to small microcontroller based system having less processing power most of them still can interface the standard input devices of a PC with them due to their simplicity in interfacing method.  As far as the output is concerned the most commonly used are small LCD modules like monochrome 16*2, graphical or small sized color LCD display screens.This particular project discusses method of interfacing a standard PS2 keyboard with the Arduino board and display the keys pressed in a 16*2 LCD screen. 

Keypads have integrated deep into everyday schedule of an average person that it is almost impossible to carry out working on electronic devices without using them. Computer keyboards, calculators, remote controls, game joysticks, electronic locks and ATM machines are just a few cases where one cannot do even a single task without using keypad. It becomes quite uncanny that how deeply this electronic accessory has embedded into lives of a major part of the population. Various types of keypads exist as per user’s requirements. For instance, computer and some smartphones have QWERTY keypad while calculators and simple telephones come with an alphanumeric keypad.

Computer keyboard is a device used to convert the keystrokes in to the electrical signals that a computer can understand. There are special types of switches and circuits to do this.When we press a key, it completes its corresponding circuit and an electrical signal goes to keyboard’s internal processor which detects the key which is pressed.A keyboard works on a 5V power which it takes from the computer through the Serial cable or USB. When we press a key on the keyboard, it pushes down the dome shaped rubber button which in turn electrically connects the top & bottom layer at that point and the signal is sent to the COB IC.