资料介绍
Many applications require d r iving LEDs along with an
inter face to a keypad. Implementing such designs
usually i nvol ves using up significant amounts of the
processors I/O lines. This application note desc r ibes a
method which uses only 16 I/O pins of a PIC16C5X
microcontroller to sample a 4x4 keypad matr ix, and
directly dr ive four 7-segment LEDs (Figur e 1) . AN529
Multiplexing LED Drive and a 4x4 Keypad Sampling
drive of the LEDs is possible, because of the high sink
Author: Stan D’Souza and source capabilities of PIC16C5X microcontroller,
Microchip Technology Inc. thus eliminating the use of an external drive transistor,
and results in a reduction in both cost and complexity of
INTRODUCTION the overall circuit.
Typically applications having LEDs a
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