This document provides an overview of microcontrollers and embedded systems. It discusses characteristics of embedded systems and integrated circuits used in processors. It also describes challenges in embedded system design and common microcontrollers like the 8051. Examples are given of interfacing components like seven segment displays, keypads, and LCDs to microcontrollers. Finally, an example project is outlined for an electronic code lock using a microcontroller and password input from a keypad.

1. MICROCONTROLLER
AND
EMBEDDED
SYSTEM

2. CONTENTS
1. EMBEDDED SYSTEM & CHARACTERSTICES
2. INTEGRATED CIRCUIT
3. FULL & SEMI CUSTOM DESIGN
4. PROGRAMABLE LOGIC DEVICE
5. DESIGN CHALLENGES IN EMBEDDED SYSTEM
6. EMBEDDED OPERATING SYSTEM
7. MICROCONTROLLERS & 8051
MICROCONTROLLER
8. SEVEN SEGMENT DISPLAY & KEYPAD
INTERFACING
9. LCD INTERFACING
10. PROJECT - ELECTRONIC CODE LOCK WITH
USER -DEFINED PASSWORD

5. Integrated Circuit
Processors are implemented on an integrated
circuit (IC). IC, often called as chip consists of
a set of transistors interconnected with other
devices. There are different processes to
fabricate semiconductors namely n-MOS, p-MOS
and C-MOS.
The most widely used process is CMOS
(complementary metal oxide semiconductor).
Semiconductors devices are built with
different layers. The bottom-most layers are of
transistors.
—
—

6. EXAMPLES OF EMBEDDED SYSTEM
•Automated tiller machines (ATMS).
•Cellular telephones and telephonic switches.
•Computer printers, Copiers.
•Disk drives (floppy disk drive and hard disk drive)
•Engine controllers and antilock brake controllers for automobiles.
•Home automation products like thermostat, air conditioners
sprinkles and security monitoring system.
•House hold appliances including microwave ovens, washing
machines, TV sets DVD players/recorders.
•Medical equipment.
•Measurement equipment such as digital storage oscilloscopes,
logic analyzers and spectrum analyzers.
•Multimedia appliances: internet radio receivers, TV set top boxes.
•Stationary video game controllers.

7. MICROPROCESSOR
A microprocessor is a general-purpose digital computer central
processing unit (CPU). Although popularly known as a “computer on
a chip” is in no sense a complete digital computer. The block
diagram of a microprocessor CPU is shown, which contains an
arithmetic and logical unit (ALU), a program counter (PC), a stack
pointer (SP),some working registers, a clock timing circuit, and
interrupt circuits
Data Bus
CPU
Serial COM
Port
RAM
ROM
I/O Port
Timer

8. MICROCONTROLLERS
A microcontroller is an economical computer-on-a-chip built for dealing
with specific tasks, such as displaying or receiving information through
LEDs or remote controlled devices. The most commonly used set of
microcontrollers belong to 8051 Family. 8051 Microcontrollers
continue to remain a preferred choice for a vast community of
hobbyists and professionals. Through 8051, the world became witness
to the most revolutionary set of microcontrollers.

9. MICROCONTROLLER 8051
Microcontroller (also MCU or µC) is a computer-on-a-chip. It is
a type of microprocessor emphasizing high integration, low
power consumption, self-sufficiency and cost-effectiveness, in
contrast to a general-purpose microprocessor (the kind used in
a PC). In addition to the usual arithmetic and logic elements of
a general purpose microprocessor, the microcontroller typically
integrates additional elements such as read-write memory for
data storage, read-only memory, such as flash for code storage,
EEPROM for permanent data storage, peripheral devices, and
input/output interfaces. At clock speeds of as little as a few
MHz or even lower, microcontrollers often operate at very low
speed compared to modern day microprocessors, but this is
adequate for typical applications. They consume relatively little
power .

10. Special features of 8051 are:
•8-bit data bus
•16-bit address bus
•32 general purpose registers each of 8 bits
•16 bit timers (usually 2, but may have more, or less).
•3 internal and 2 external interrupts.
•Bit as well as byte addressable RAM area of 16 bytes.
•Four 8-bit ports, (short models have two 8-bit ports).
16-bit program counter and data pointer

11. REGULATED POWER SUPPLY
Transformer
circuit symbol
Transformer
Transformers convert AC electricity from one voltage to another with little
loss of power. Transformers work only with AC and this is one of the reasons
why mains electricity is AC.
Step-up transformers increase voltage, step-down transformers reduce
voltage. Most power supplies use a step-down transformer to reduce the
dangerously high mains voltage (230V in UK) to a safer low voltage.
The input coil is called the primary and the output coil is called the
secondary. There is no electrical connection between the two coils, instead
they are linked by an alternating magnetic field created in the soft-iron core
of the transformer. The two lines in the middle of the circuit symbol represent
the core.
Transformers waste very little power so the power out is (almost) equal to the
power in. Note that as voltage is stepped down current is stepped up.

12. STRUCTURE OF POWER SUPPLY
There are many types of power supply. Most are designed to convert
high voltage AC mains electricity to a suitable low voltage supply for
electronics circuits and other devices. A power supply can by broken
down into a series of blocks, each of which performs a particular
function.
For example a 5V regulated supply:
Each of the blocks is described in more detail below:
Transformer - steps down high voltage AC mains to low voltage AC.
Rectifier - converts AC to DC, but the DC output is varying.
Smoothing - smoothens the DC from varying greatly to a small ripple.
Regulator - eliminates ripple by setting DC output to a fixed voltage.

13. SEVEN SEGMENT DISPLAY
A seven segment display is the most basic electronic display
device that can display digits from 0-9. They find wide
application in devices that display numeric information like digital
clocks, radio, microwave ovens, electronic meters etc. The most
common configuration has an array of eight LEDs arranged in a
special pattern to display these digits. They are laid out as a
squared-off figure ‘8’. Every LED is assigned a name from 'a' to
'h' and is identified by its name. Seven LEDs 'a' to 'g' are used to
display the numerals while dot/decimal eighth LED 'h' is used to
display them.

14. LCD INTERFACING
The most commonly used Character based LCDs are based on
Hitachi's HD44780 controller or other which are compatible
with HD44580. In this tutorial, we will discuss about character
based LCDs, their interfacing with various
microcontrollers, various interfaces (8-bit/4bit), programming, special stuff and tricks you can do with
these simple looking LCDs .

15. PROJECT
Security code lock
with user defined
password using 8051
microcontroller
(AT89C51)

16. INTRODUCTION

17. WORKING
A 4x3 matrix keypad and a 16x2 LCD have been used here. Keypad
and LCD are very commonly used input & output devices,
respectively. A four digit predefined password needs to be specified
the user. This password is stored in the system.
While unlocking, if the entered password from keypad matches with
the stored password, then the lock opens and a message is
displayed on LCD. Also an output pin is made high to be used for
further purpose.
The connections in the circuit are as following: port P2 of
microcontroller AT89C51 is used as data input port which is
connected to data pins (7-14) of LCD. P1^0, P1^1 and P1^2 pins
of microcontroller are connected to control pins RS, RW and EN of
LCD. Port P0 is used to take input from keypad. P0^7 has been
used as lock output pin of controller.

18. As the program starts, string ‘Enter Password’ is displayed on
LCD. The keypad is scanned for pressed digits one by one.
Every time, row and column of the key pressed is detected and
a ‘*’ is displayed on LCD corresponding to the entered
number. After the four digits are entered, the user is prompted
to ‘Confirm Password’ and again the input is taken through LCD.
If the passwords do not match, a message is displayed to
indicate ‘Wrong Password’; otherwise the user is prompted to
unlock the device.
To unlock, user needs to ‘Enter Password’ through keypad. Again the
keypad is scanned for pressed keys and corresponding digits are
identified. The passkey is displayed as ‘****’ on the LCD screen.
After the four digits are entered, they are compared with the pre-set
password. If all the four digits match with set password, LCD
displays ‘Lock Open’ and the lock output pin goes high. If the
security code is wrong, ‘Wrong Password’ is sent to be displayed on
LCD. The system gets locked if more than three attempts are made
with wrong password to open the electronic lock. The system needs
to be reset in such a case.

19. CIRCUIT DIAGRAM

20. THANKS