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AN529
| Title |
Title
Multiplexing LED Drive and 4x4 Keypad Sampling
|
|---|---|
| Name |
Name
AN529
|
| Date |
Date
06/24/2015
|
| Application Categories |
Application Categories
Home Appliance /
User Interface
Lighting /
LED
|
| Product Categories |
Product Categories
8-bit MCU
|
| Description |
Description
Many applications require driving LEDs along with an interface to a keypad. Implementing such designs usually involves using up significant amounts of the processors I/O lines. This application note describes a method which uses only 16 I/O pins of a PIC16C5X microcontroller to sample a 4x4 keypad matrix, and directly drive four 7-segment LEDs (Figure 1). Direct drive of the LEDs is possible, because of the high sink and source capabilities of PIC16C5X microcontroller, thus eliminating the use of an external drive transistor, and results in a reduction in both cost and complexity of the overall circuit. Typically applications having LEDs and keypads also keep track of real-time, in order to synchronize certain related events. An Industrial Clock/Timer example has been used in this application note as a demonstration of these functions. The software overhead to keep track of real time is minimal and the user can modify the code to significantly expand the functionality of this circuit.
|
Files
| Title | Title | Download | Date | Size |
|---|---|---|---|---|
| AN529 Source Code - Multiplexing LED Drive and 4x4 Keypad Sampling 34.8 KB 06/23/2015 | AN529 Source Code - Multiplexing LED Drive and 4x4 Keypad Sampling | Download | 06/23/2015 | 34.8 KB |