A 16 key keypad design was developed for adequate functionality without introducing redundancy or increasing the size of the phone. Currently it is connected to P1 of 8x51.

DESIGN

An ad hoc Keypad using 16 push buttons was created for testing purposes till a proper touch key keypad is procured. Large bounce bars from it being called a "good" keypad by any means, but is a work of art none the less.

Keypad (front)

Keypad (back)

A51 Source code for basic scanning of keypad

A51 Source code for Alphanumeric overloading of keypad

A scanner chip is also available for a 4X4 keypad : MM74C922.

Click here for MM74C922 data sheet