key

1. MICROCONTROLLER AND EMBEDDED SYSTEM
[21CS43]
Seminar on:
“KEYBOARD”
Submitted by:
ISHA S SHETTY
4JK21CS022
Under the guidance of
DR. LAXMI GULAPPAGOL
01/08/2023

2. Objectives
 To k n o w a b o u t k e y b o a r d
 To u n d e r s t a n d t h e M a t r i x k e y b o a r d I n t e r f a c i n g

3. Keyboard
 Keyboard is an input device 'HIGH' Pulse generator for user
interfacing.
 Christopher Latham Sholes was the inventor of the keyboard for
computing devices. He patented the typewriter that we commonly
use today in 1868.
 Nowadays, different types of keyboard are available such as :
 QWERTY Keyboards, Numeric Keypads, Wired Keyboards,
Wireless Keyboards, Ergonomic keyboards, etc.

4. Keyboard keys
 Keyboards generally has 104 keys.
 A standard QWERTY keyboard has various keys on it, like:
a) Alphanumeric keys b) Punctuation keys c) Special keys
 These keys allow us to enter data and to perform some other
commands.
 If the number of keys required is very limited, push-button switches
can be used and they can be directly interfaced to the port pins for
reading.

5. Keyboard keys
 However, there may be situations demanding a large number of keys for
user input (e.g., PDA device with alpha-numeric keypad for user data
entry).
 In such situations it may not be possible to interface each key to a port
pin due to the limitation in the number of general-purpose port pins
available for the processor/ controller in use and moreover it is wastage
of port pins.
 Matrix keyboard is an optimum solution for handling large key
requirement. It greatly reduces the number of interface connections.

6. Matrix Keyboard Interfacing
• For interfacing 16 keys, in the direct
interfacing technique, 16 port pins
are required,
• whereas in the matrix keyboard only
8 lines are required. The 16 keys
are arranged in a 4-column
• x 4 Row matrix. The following
Figure illustrates the connection o
keys in a matrix keyboard.
• Fig.1 Matrix keyboard Interfacing

7. Matrix Keyboard Interfacing
 In a matrix keyboard, the keys are arranged in matrix fashion.
 For detecting a key press, the keyboard uses the scanning technique, where each
row of the matrix is pulled low and the columns are read. After reading the status of
each column corresponding to a row, the row is pulled high and the next row is
pulled low and the status of the columns are read.
 This process is repeated until the scanning for all rows are completed. When a row
is pulled low and if a key connected to the row is pressed, reading the column to
which the key is connected will give logic 0.
 Since keys are mechanical devices, proper key de-bouncing technique should be
applied.

8. Outcomes
 We came to know about keyboard
 We understood the Matrix keyboard Interfacing

9. Reference
• “Introduction to Embedded Systems”, by Shibu K V
• https://www.slideshare.net/kekencalvo/computer-keyboard

10. THANK YOU