Pic 18f matrix

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Keypad 4x4


Additional board

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.

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 2: Keypad 4x4 connected to development system

The keyboard is usually used as follows: 1. Four microcontroller’s pins should be defined as outputs, and other four pins should be defined as inputs. In order the keypad to work properly, pull-down resistors should be placed on the microcontroller’s input pins, thus defining 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.

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.


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