Hex keypad interfacing in PIC18F4550

INTRODUCTION
The keypad used in the OpenLab platform is a 4×4 matrix or a hex keypad. It has 8 pins that are connected onto the base board. The keypad is a feature on many consumer devices and instruments that is a crucial part of a user interface. In this chapter, we will discuss in depth, the working of a keypad and the common issues of implementing this device practically and its work around for its successful implementation.

OBJECTIVES

1. It is very important to understand the circuit of the keypad before writing a code. We will discuss in detail about circuit configuration in section 1.
2. Since the Keypad interface requires IO ports, we will not be providing a description on a register level. Refer Topic 1 for more information.
3. Rather than providing the code snippet, we will be giving you an idea on how to perform this operation. Therefore, this topic will be covered in two detailed sections.