Hardware Reference
In-Depth Information
number or entered a PIN for an ATM withdrawal or debit purchase knows how to use
it. But added to a Raspberry Pi, you could use a keypad as part of a locking mechanism
or for any kind of numeric input. You could even use it to turn your Raspberry Pi into
a Voice over IP (VoIP) phone, but with that old push-button feel.
In addition to your Pi, you'll need:
• Linux preinstalled with python2 (any distribution should work).
• A matrix input numeric keypad. We used the Membrane 3x4 Matrix Keypad avail-
able from Adafruit, but you can adjust our instructions to work with other key-
pads.
• A breadboard and male-to-female jumper wires. These are just for prototyping
the numeric keypad connection to the GPIO on the Raspberry Pi. For a more
permanent setup, you should solder things together.
These instructions assume you're using a Raspberry Pi Model B, revision 2. If
you're not, the GPIO pin numbers are different, and you'll need to adjust.
How the Matrix Keypad Works
The Membrane 3x4 Matrix Numeric Keypad is simple. It has three columns with four
rows of buttons and one wire for each row and column, as shown in Figure 6-13 .
Figure 6-13.
Membrane 3 x 4 Matrix Numeric Keypad
 
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