mikroElektronika Keypad 4x4 User Manual

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Keypad 4x4

All Mikroelektronika’s development systems feature a large number of peripheral
modules expanding microcontroller’s range of application and making the
process of program testing easier. In addition to these modules, it is also
possible to use numerous additional modules linked to the development system
through the I/O port connectors. Some of these additional modules can operate
as stand-alone devices without being connected to the microcontroller.

Manual

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Keypad 4x4

Keypad 4x4

Keypad 4x4 is used for loading numerics into the microcontroller. It consists of 16 buttons arranged in a form of an array containig four
lines and four columns. It is connected to the development system by regular IDC 10 female connector plugged in some development
system’s port.

Figure 1: Keypad 4x4

Figure 3: Keypad 4x4 connection schematic

A far easier way to load data by using keypad 4x4 is by employing ready-to-use funtions provided in the Keypad Library of any
Mikroelektronika’s compiler. On the following pages there are three simple examples written for PIC16F887 microcontrolller in mikroC,
mikroBasic and mikroPascal programming languages. In all cases, the number loaded via keypad is converted into the equivalent
ASCII code (0...9, A...F) and then it is displayed in the second line of LCD display. In this case, pull-down resistors are placed on output
pins RD0 - RD3 and are used to determine logic zero (0) in idle state.

Figure 2: Keypad 4x4 connected to development system

The keyboard is usually used as follows:

1.

Four microcontroller’s pins should be dened as outputs,
and other four pins should be dened as inputs. In order the

keypad to work properly, pull-down resistors should be placed

on the microcontroller’s input pins, thus dening logic state

when no button is pressed.

2.

Then, the output pins are set to logic one (1) and input pins’
logic state is read. By pressing any button, a logic one (1) will
appear on some input pin.

3.

By combining zeros and ones on the output pins, it is
determined which button is pressed.

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