This document provides an overview of interfacing a 4x4 matrix keypad with an AVR microcontroller. It discusses that a matrix keypad reduces the number of I/O pins needed by organizing the keys in a grid with rows and columns. When a key is pressed, it connects a row and column. The document outlines that the rows are connected to an output port and the columns to an input port. It also mentions that scanning involves initializing the keypad ports and then scanning one row at a time to detect which key is pressed. The document is intended as lecture notes for a course on programming AVR microcontrollers.

1. 1
06-Interfacing 4x4
keypad.
By : Mohamed Fawzy
Programming AVR Microcontrollers
© Mohamed F.A.B 2015

2. Lecture Notes:
2
o Set Your Phone To Vibration Mode.
o Ask any time.
o During labs, Feel Free To Check Any Materials or
Internet.
o Slides are self content.
o Feel Free To Share This Materials With Your Friends.
o Work Hard For Achieving Most Of This Course.
© Mohamed F.A.B 2015

3. 3
Don't Forget !!!!
© Mohamed F.A.B 2015
Any Expert Was Once A Beginner


4. 4
Lesson(12).
© Mohamed F.A.B 2015
Lesson (11):
Interfacing Keypad 4*4 .

5. 5
Lesson (11) Topics.
© Mohamed F.A.B 2015
► Why Matrix Keypad.
► Matrix Keypad Theory.
► Scanning Key pressed.

6. 6
Why Matrix Keypad?
© Mohamed F.A.B 2015
o To reduce the microcontroller I/O pin usage, keyboards
are organized in a matrix of rows and columns.
o The CPU accesses both rows and columns through ports.
o When a key is pressed, a row and a column make a
contact; otherwise, there is no connection between
rows and columns.
o A 4 × 4 matrix connected to two ports. The rows are
connected to an output port and the columns are
connected to an input port.

7. 7
Keypad Theory.
© Mohamed F.A.B 2015
.

8. 8
Scanning Key pressed.
© Mohamed F.A.B 2015
Configurations for keypad:
Initialization for keypad PORT:

9. 9
Scanning Key pressed. Cont’
© Mohamed F.A.B 2015
Scanning one row:

10. 10
Scanning Key pressed. Cont’
© Mohamed F.A.B 2015

11. 11
Questions:
© Mohamed F.A.B 2015

12. Thank You All 
12
mo7amed.fawzy33@gmail.com
01006032792
fawzy.fab@gmail.com
© Mohamed F.A.B 2015