4x4 Keypad User`s Manual

4x4 Keypad User`s Manual
4x4 Keypad
User’s Manual
V1.0
September 2009
Information contained in this publication regarding device applications and the like is intended through suggestion only and may be
superseded by updates. It is your responsibility to ensure that your application meets with your specifications. No representation or
warranty is given and no liability is assumed by Cytron Technologies Incorporated with respect to the accuracy or use of such information
or infringement of patents or other intellectual property rights arising from such use or otherwise. Use of Cytron Technologies’s products
as critical components in life support systems is not authorized except with express written approval by Cytron Technologies. No licenses
are conveyed, implicitly or otherwise, under any intellectual property rights.
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Product User’s Manual – 4x4 Keypad
Index
1. Introduction
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2. Warranty
3
Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved
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Product User’s Manual – 4x4 Keypad
1. INTRODUCTION
Keypad is an array of switch. There will be 2 wires connected each time a button is pressed.
For example; when button ‘1’ is pressed, pin col1 and row1 is connected. There is no
connection between rows and also columns. The button make it connect.
To scan which button is pressed, users need to scan it column by column and row by row.
Make rows as input and columns as output. For example; set all columns by default. 1st scan,
clear (logic low) column 1 and scan row1-row4 low logic, this will determine which button is
pressed in column1. If one of those buttons is pressed, record it and jump out from the
scanning loop and continue with the action required. If none button is pressed in column1, set
it back to default (logic high) and clear column2. Scan row1-row4 again and this will scan
button press of ‘2’, ‘5’, ‘8’ and ‘0’. And this process is being repeated until all four columns
being completed scanned.
For keypad wiring, keypad pins need to pull up or pull down to avoid floating case happen.
Pull up normally connect to 5V and pull down is connect to ground.
4x4 Keypad pin can directly connect to microcontroller or keypad decoder IC for decode
purpose. However, DIY scanning of keypad consumes a lot of understanding in programming
and more program space. The better way to interface a keypad to the PIC is to use a keypad
encoder in between the keypad and the microcontroller. One of the Keypad Encoder is the
Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved
1
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Product User’s Manual – 4x4 Keypad
MMC74C922. Simply hook up all the row and the column pins directly to the encoder and it
will output a HIGH pulse on the Data Available pin whenever a key is pressed. After that, the
encoder will output 4 bits of data to the PIC. Please refer MMC74C922 datasheet for more
information.
Below is example keypad which connects directly to a PIC microcontroller.
Figure 1: 4x4 Keypad connection to microcontroller
Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved
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Product User’s Manual – 4x4 Keypad
2. WARRANTY
¾
¾
¾
¾
Product warranty is valid for 6 months.
Warranty only applies to manufacturing defect.
Damage caused by mis-use is not covered under warranty.
Warranty does not cover freight cost for both ways.
Prepared by
Cytron Technologies Sdn. Bhd.
19, Jalan Kebudayaan 1A,
Taman Universiti,
81300 Skudai,
Johor, Malaysia.
Tel:
Fax:
+607-521 3178
+607-521 1861
URL: www.cytron.com.my
Email: [email protected]
[email protected]
Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved
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