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Raspberry Pi Zero Cookbook

You're reading from   Raspberry Pi Zero Cookbook Delve into the practical world of the Raspberry Pi Zero

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Product type Paperback
Published in Mar 2017
Publisher Packt
ISBN-13 9781786463852
Length 422 pages
Edition 1st Edition
Languages
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Author (1):
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Edward Snajder Edward Snajder
Author Profile Icon Edward Snajder
Edward Snajder
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Table of Contents (11) Chapters Close

Preface 1. Kick-Start Your Raspberry Pi Zero FREE CHAPTER 2. Setting Up Physical and Wireless Connections 3. Programming with Linux 4. Programming with Python 5. Getting Your Hands Dirty Using the GPIO Header 6. Controlling the LEDs and Displays 7. Controlling the Hardware 8. Taking Digital Inputs to the Raspberry Pi Zero 9. Interfacing Sensors with the Raspberry Pi Zero 10. Cooking up Projects to Amaze the World!

Interfacing a keypad with the RPZ


Now that we've looked at the Raspberry Pi Zero's pull-up and pull-down resistor options, we can apply our knowledge to operating a 12- or 16-digit keypad. Let's take a look!

Getting ready

All you'll need for this recipe is a 16-key numeric keypad. One is included in the Elegoo kit, and they are available from most online retailers. A typical keyboard input looks something like this:

How to do it...

  1. There are eight pins on a 16-key numeric keypad. Here is how you wire them to your Raspberry Pi:

  2. Understanding the internals of the keypad makes it easy to understand how to control it. Effectively, each number is a switch tied to a column and a row, as shown here:

    The Internals of a 16-key Input Pad

  3. Suppose we set our rows as inputs with the pull-down circuit enabled and configure the columns as outputs. Now, when a button is pressed, if we can detect which output and input were connected, we can determine which key was pressed. Look at keypad.py in the ch8 directory...

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