Project

1An adaptive hands free technique for mobile communication system

CHAPTER 1: INTRODUCTION

Now-a-days, using Mobile phones while driving motor vehicles have became common.

As a result of which the drivers are getting distracted resulting in many accidents. From the

previous statistics it’s been confirmed that about 70 percent of the accidents on the roads are due

to the use of mobile phones while walking and driving. But in some situations some of the

people feel it responsible using the mobile while driving.

Mainly used systems to avoid the calls in traffic while driving till date are call-diverting,

voice mail converting, flight mode, etc….

So, let’s go on for a new technique by which we can intimate the calling-subscriber by a

voice message that we are in driving directly when we get the call. Only in the case of

emergency, there is an option whether to send a voice message or answer the call. If the call is

answered the speed of car the driver gets reduced.

Here we are going to use a prototype in which there are two sections:

1. Dash Board section which is fixed in the car to control the speed of the car using a relay while

driving.

2. Mobile section where the speaker, buzzer and an LCD display are present to imitate to the

driver from whom the call is received. Buzzer blows when the call comes for the second time.

Speaker is used to hear the recorded message stored in the memory of the micro controller.

NALLA MALLA REDDY ENGINEERING COLLEGE ELECTRONICS AND COMMUNICATION ENGINEERING


1.1 BLOCK DIAGRAM

Block diagram consists of two major parts:

1. Dash Board section

2. Mobile section

DASH-BOARD SECTION

Fig1: Dash-Board Section


RELAY

ENGINE

8051 MCU

ENCODER

RECIEVER (433.34 MHz)

TRANSMITTER (27 MHz)

POWER - SUPPLY


MOBILE SECTION

Fig2: Mobile Section

POWER SUPPLY SECTION

Fig3: Power Supply


TRANSMITTER (433.34 MHz) GSM

MODEM

RECIEVER (27 MHz)

PIC MCU

DECODER

MAX232

POWER - SUPPLY

POWER - SUPPLY

Power supply 230V AC

TRANSFORMER (230-9V AC)

RECTIFIER (9V DC)

VOLTAGE REGULATOR

FILTER 5V DC

Call INDICATOR (BUZZER, SPEAKER)


1.2 EXISTING SYSTEM

The methods so far used for avoiding the calls are:

Muting the call

The process in which the cell phone is switched on to silent mode is called “Call

Muting”. In this mode call is received but the ring is not heard.

Call diverting

The process in which the call is diverted to a particular number as assigned by the

person is called “call diverting”.

Voice mail conversion

In “voice mail” process the call gets lifted but the tone is not heard.

Flight mode

There is no signal for the phone. So, there is no connectivity.

1.3 PROPOSED SYSTEM

In this technique we have two options. They are:

Auto answering of call, provides the information of the driver in the form of voice

message.

Only emergency calls are allowed to access.

1.4 ADVANTAGES OF PROPOSED SYSTEM

Requires low cost for building this system.

As the circuitry is very small it can be easily carried anywhere.

The output of the system is accurate.

Consumes less power.

It is portable in nature.



1.5 BLOCK DIAGRAM EXPLANATION

The block diagram as shown above consists of two sections. Dash-board section and

Mobile section.

Mobile Section:

The mobile section mainly consists of GSM modem, MAX232, PIC Micro Controller,

Call Indicator and RF- transmitter and receiver. This section is present with the driver. After

getting the confirmation from the dash board section that the mobile got switched in to driving

mode this section comes in to picture.

When the call comes to the mobile section for the first time, the GSM modem receives

the call. An indication is sent to the micro controller with the help of RS-232 cable. PIC

controller has an in built ADC which converts frequency signal in to bits stream and is feed to

the call indictor. LCD present displays the mobile number from which call is received. The

speaker in the call indicator shutters a message that the “called subscriber is in driving”.

When the call is received from the same number with in no time for the second time the

same procedure continues till the call indicator. But the buzzer will indicate that the call is

emergency one. There will be a switch providing an option to accept or reject the call. If the call

is rejected then same voice message is heard through the speaker. If the call is accepted then a

signal is send to the dash board section. In the dash board section with the help of the relay the

car speed is reduced.

If the call comes from a second subscriber in between the two calls from the first

subscriber again a voice message is sent to the first subscriber



Dash-Board Section:

When the car gets started, an indication is sent to the micro controller (8051) through the

relay. The micro controller with the help of RF Transmitter sends an indication to the mobile

section the car has started and the mobile got switched in to driving mode.

The Dash Board Section waits for the confirmation from the mobile section that the call

is accepted. The signal is in the form of RF signal which is decoded and is feed to the micro

controller. The controller with the help of the relay reduces the speed of the stepper motor

present in the car. As a result the car speed gets reduced.

When the call is terminated again a signal is send from the dash board section to the

mobile section that the car is started and the mobile got switched to driving mode.

Power Supply:

There are two types of power supplies used here:

1. An adapter is used for connecting the GSM modem. The output of that adapter is 9V dc.

2. For both micro controllers we are giving 5V DC.

Designing:

Now the aim is to design the power supply section which converts 230V AC in to 5V

DC. Since 230V AC is too high to reduce it to directly 5V DC, therefore we need a step-down

transformer that reduces the line voltage to certain voltage that will help us to convert it in to a

5V DC.

The output of the transformer is 9V AC; it feed to rectifier that converts AC to pulsating

DC.Here we are using Bridge rectifier, because half wave rectifier has we less in efficiency.

Even though the efficiency of full wave and bridge rectifier are the same, since there is no

requirement for any negative voltage for our application, we gone with bridge rectifier.



1.6 SCHEMATIC DIAGRAM AND DESCRIPTION

The schematic diagram here consists of mainly two parts:

1. Dash Board Section.

2. Mobile Section.

1.6.1 DASH-BOARD SECTION

Fig 4: Dash Board Section



1.6.2 MOBILE SECTION

Fig 5: Mobile Section

1.7 SCHEMATIC DIAGRAM EXPLANATION

Mobile Section:

When the Engine gets started the micro controller indicates by pin16. Micro controller in

the dash board section is interfaced with the pin10 of the decoder through pin27 of the controller.

Pin14of decoder is interfaced with data port of RF transmitter. The RF receiver of the mobile

section receives it and feeds the information to pin19 of encoder. The pin16 of encoder in mobile



section is interfaced with the pin38 of micro controller. Then successfully the information is

received that the car is started and the mobile got switched to driving mode.

Now actually mobile section comes in to picture. When we get the call for the very first

time it is received by the GSM modem. The GSM modem is interfaced with the serial

communication port RS-232 to the micro controller. Pin2 and pin3 of the serial port is interfaced

with pin8 and pin7 of the MAX232 ports. Pin9 and pin10 of the MAX232 is interfaced with

pin26 and pin25 of the PIC micro controller.pins13 and 14 are given to the crystal oscillator. PIC

has an inbuilt ADC which converts the analog signal to digital. The PIC controller interfaces

pin19 to pin30 with pin14 to pin7 of the LCD. Pin40 is interfaced with the Buzzer. Pin39 is

interfaced with the voice module. Pin23 is interfaced with the pin10 of the decoder. The pin14 of

the decoder is feed to the data pin.

Dash-Board section:

When the Engine of the car gets started it intimates to the mobile section that mobile is

switched on to driving mode. Engine is feed to pin16. When the required signal is received by

the RF Receiver, it is then feed to encoder through pin17. Pin10 to pin14 of encoder are

interfaced with pin21 to pin25 of the micro controller. Pin28 of controller is interfaced with relay

which is again interfaced with the stepper motor.



CHAPTER 2: WORKING

The operation first starts in the dash board section. When the car gets started Engine of it

provides the power supply to the micro controller (8051) and makes it on. The micro controller

with the help of a decoder converts the bits stream in to continuous signal and feeds to the

RF-Transmitter (27MHz). In the RF-Transmitter the frequency modulation takes place. The

resultant signal of RF-Transmitter is transmitted from the dash board section to the mobile

section.

The RF-Receiver (27MHz) at the mobile section receives the signal and then encodes and

feeds the signal to the PIC controller. The received signal indicates that the car got started and

the mobile is switched on to driving mode.

When the GSM modem of the mobile section gets the call for the first time, signal is feed

to the PIC controller by interfacing it with GSM modem using RS232 cable. The signal from PIC

is feed to the call indicator section. In this section there is a LCD display where the number of

the dialed subscriber gets displayed. The speaker in that section utters a voice message that the

called subscriber is in driving.

If within no time if the mobile section gets the call for the second time, the signal is again

feed to the PIC controller as discussed above. The signal from the PIC is now feed to the

indicator section again. But for the second time, the Buzzer blows off and there is a switch which

provides an option either to accept or reject the call. The number of the called subscriber is again

displayed on the LCD display.

If the call is accepted the PIC controller with the help of a decoder converts bit stream

into continuous signal and transmits the signal undergoing frequency and amplitude modulation

in RF-Transmitter. RF-Receiver in the dash board section receives the transmitted signal and

converts it in to bit stream and feed to the micro controller (8051). The micro controller with the

help of a relay driver steps down the speed of the car. After terminating the call again a signal is

transmitted to the mobile section that the mobile got switched to driving mode.



If the call is rejected then also a voice message is heard from the speaker that the

subscriber is busy. Immediately after the voice message is heard again a signal is transmitted to

the mobile section that the mobile got switched to driving mode.



CHAPTER 3: MICRO CONTROLLER

In this project we are using two micro controllers namely:

1. 8051 micro controller

2. PIC micro controller

3.1 8051 MICRO CONTROLLER (89s51)

3.1.1 INTRODUCTION:

89S51 microcontrollers is a low-power, high-performance CMOS 8-bit micro computer

with 8K bytes of Flash programmable and erasable read only memory (PEROM). The device is

manufactured using Atmel high-density nonvolatile memory technology and is compatible with

the industry-standard 89S51 microcontrollers. The on-chip Flash allows the program memory to

be reprogrammed in-system or by a conventional nonvolatile memory programmer. By

combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel 89s51

Microcontroller is a powerful microcomputer which provides a highly-flexible and cost-effective

solution to many embedded control applications.

3.1.2 FEATURES OF 89S51 MICROCONTROLLERS:

The 89s51 microcontrollers provides the following standard features: 8k bytes of flash,

256 bytes of ram, 32 i/o lines, three 16-bit timer/counters, a six-vector two-level interrupt

architecture, a full-duplex serial port, on-chip oscillator, and clock circuitry. In addition,

the 89s51 Microcontroller is designed with Static Logic for operation down to zero frequency

and supports two software selectable power saving modes. The idle mode stops the CPU while

allowing the ram, timer/counters, serial port, and interrupt system to continue functioning. The

power-down mode saves the RAM contents but freezes the oscillator, disabling all other chip

functions until next Reset.



3.1.3 PIN DIAGRAM

Fig6: Pin Diagram of 89s51

3.1.4 PIN DESCRIPTION

VCC - Supply voltage.

GND - Ground.

Port0

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin

can sink eight TTL inputs. When 1s are written to Port 0 pins, the pins can be used as

high impedance inputs. Port 0 can also be configured to be the multiplexed low order

address/data bus during accesses to external program and data memory.

Port1

Port 1 is an 8-bit bi-directional I/O port with internal pull ups. The Port 1 output

buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are

pulled high by the internal pull ups and can be used as inputs. As inputs, Port 1 pins that



are externally being pulled low will source current (IIL) because of the internal pull-ups.

In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count

input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, Port1

also receives the low-order address bytes during Flash programming and verification.

Port2



pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that

are externally being pulled low will source current (IIL) because of the internal pull-ups.

Port2 emits the high-order address byte during fetches from external program memory

and during accesses to external data memory that uses 16-bit addresses (MOVX @

DPTR).

Port3



pulled high by the internal pull ups and can be used as inputs. As inputs, Port 3 pins that

are externally being pulled low will source current (IIL) because of the pull-ups.

RST

Reset input. A high on this pin for two machine cycles while the oscillator is

running resets the device.

ALE/PROG

Address Latch Enable is an output pulse for latching the low byte of the address

during accesses to external memory. In normal operation, ALE is emitted at a constant

rate of 1/6 the oscillator frequency and may be used for external timing or clocking

purposes.



PSEN

Program Store Enable is the read strobe to external program memory. When

the 89s51 Microcontroller is executing code from external program memory, PSEN is

activated twice each machine cycle, except that two PSEN activations are skipped during

each access to external data memory.

EA/VPP

EA (External Access Enable) must be strapped to GND in order to enable the

device to fetch code from external program memory locations starting at 0000H up to

FFFFH.

XTAL1

Input to the inverting oscillator amplifier and input to the internal clock operating

circuit.

XTAL2

Connected to the output of the inverting oscillator amplifier.

Timer0-and-Timer1

Timer 0 and Timer 1 in the 89S51 microcontrollers operate the same way as

Timer 0 and Timer 1 in the 89S51 microcontrollers. The type of operation is selected by

bit C/T2. Timer 2 has three operating modes: capture, auto-reload and baud rate

generator.

3.1.5 SPECIAL FUNCTION REGISTERS

A map of the on-chip memory area is called as Special Function Register (SFR). Note

that not all of the addresses are occupied, and unoccupied addresses may not be implemented on

the chip. Read accesses to these addresses will in general return random data, and write accesses

will have an indeterminate effect. Timer 2 Registers Control and status bits are contained in



registers T2CON and T2MOD for Timer 2. The register pair (RCAP2H, RCAP2L) is the

Capture/Reload registers for Timer 2 in 16-bit capture mode or 16-bit auto-reload mode.

Interrupt registers the individual interrupt enable bits are in the IE register. Two priorities can be

set for each of the six interrupt sources in the IP register.

Interrupts

The 89S51 microcontrollers has a total of six interrupt vectors: two external interrupts

(INT0 and INT1), three timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. Each

of these interrupt sources can be individually enabled or disabled by setting or clearing a bit in

Special Function Register IE. IE also contains a global disable bit, EA, which disables all

interrupts at once.

3.1.6 ARCHITECTURE OF 89s51

Fig7: Architecture of 89s51



3.2 PIC Micro Controller (18F452)

3.2.1 INTRODUCTION

PIC18F452 microcontroller is a 40-pin microcontroller housed in a DIL package, with a

pin configuration similar to the popular PIC16F877.

PIC18F2X2 microcontrollers are 28-pin devices, while PIC18F4X2 microcontrollers are

40-pin devices. The architectures of the two groups are almost identical except that the larger

devices have more input-output ports and more A/D converter channels. In this section we shall

be looking at the architecture of the PIC18F452 microcontroller in detail. The architectures of

other standard PIC18F-series microcontrollers are similar, and the knowledge gained in this

section should be enough to understand the operation of other PIC18F-series microcontrollers.

Program memory addresses consist of 21 bits, capable of accessing 2Mbytes of program

memory locations. The PIC18F452 has only 32Kbytes of program memory, which requires only

15 bits. The remaining 6 address bits are redundant and not used. A table pointer provides access

to tables and to the data stored in program memory. The program memory contains a 31-level

stack which is normally used to store the interrupt and subroutine return addresses.

The data memory bus is 12 bits wide, capable of accessing 4Kbytes of data memory

locations. The data memory also consists of special function registers (SFR) and general purpose

registers, all these are organized in banks.

The PIC18F452 consists timers/counters, capture/compare/PWM registers, USART, A/D

converter, and EEPROM data memory. The PIC18F452 consists of:

1. 4 timers/counters

2. 2 capture/compare/PWM modules

3. 2 serial communication modules

4. 8 10-bit A/D converter channels

5. 256 bytes EEPROM



3.2.2 PIN DIAGRAM

Fig8: Pin Diagram of PIC

3.2.3 PIN DESCRIPTION

Parallel I/O Ports

The parallel ports in PIC18F microcontrollers are very similar to those of the PIC16

series. The number of I/O ports and port pins varies depending on which PIC18F microcontroller

is used, but all of them have at least PORTA and PORTB. The pins of a port are labeled as RPn,

where P is the port letter and n is the port bit number. For example, PORTA pins are labeled

RA0 to RA7; PORTB pins are labeled RB0 to RB7, and so on.

The first three operations are the same in the PIC16 and the PIC18F series. In some

applications we may want to send a value to the port and then read back the value just sent. The

PIC16 series has a weakness in the port design such that the value read from a port may be

different from the value just written to it. This is because the reading is the actual port bit pin



value, and this value can be changed by external devices connected to the port pin. In the PIC18F

series, a latch register (e.g., LATA for PORTA) is introduced to the I/O ports to hold the actual

value sent to a port pin. Reading from the port reads the latched value, which is not affected by

any external device. In this section we shall be looking at the general structure of I/O ports.

PORTA in the PIC18F452 microcontroller PORTA is 7 bits wide and port pins are shared

with other functions. There are three registers associated with PORTA:

1. Port data register—PORTA

2. Port direction register—TRISA

3. Port latch register—LATA

PORT A

PORTA is the name of the port data register. The TRISA register defines the direction of

PORTA pins, where logic 1 in a bit position defines the pin as an input pin, and a 0 in a bit

position defines it as an output pin. LATA is the output latch registers which shares the same

data latch as PORTA. Writing to one is equivalent to writing to the other. But reading from

LATA activates the buffer at the top of the diagram, and the value held in the PORTA/LATA

data latch is transferred to the data bus independent of the state of the actual output pin of the

microcontroller. Bits 0 through 3 and 5 of PORTA are also used as analog inputs. After reset,

these pins are programmed as analog inputs and RA4 and RA6 are configured as digital inputs.

To program the analog inputs as digital I/O, the ADCON1 register (A/D register) must be

programmed accordingly. Writing 7 to ADCON1 configures all PORTA pins as digital I/O. The

RA4 pin is multiplexed with the Timer 0 clock input (T0CKI).

PORT B

In PIC18F452 microcontroller PORTB is an 8-bit bidirectional port shared with interrupt

pins and serial device programming pins.

PORTB is controlled by three registers:

1. Port data register—PORTB



2. Port direction register—TRISB

3. Port latch register—LATB

The general operation of PORTB is similar to that of PORTA. Each port pin has a weak

internal pull-up which can be enabled by clearing bit RBPU of register INTCON2. These pull-

ups are disabled on a power-on reset and when the port pin is configured as an output. On a

power-on reset, PORTB pins are configured as digital inputs. Internal pull-ups allow input

devices such as switches to be connected to PORTB pins without the use of external pull-up

resistors. This saves costs because the component count and wiring requirements are reduced.

www.nPortB pins RB4–RB7 can be used as interrupt-on-change inputs, whereby a change on

any of pins 4 through 7 causes an interrupt flag to be set. The interrupt enable and flag bits RBIE

and RBIF are in register INTCON. PORTC, PORTD, PORTE, and in addition to PORTA and

PORTB, the PIC18F452 has 8-bit bidirectional ports PORTC and PORTD, and 3-bit PORTE.

Each port has its own data register (e.g., PORTC), data PIC18F452 PORTB RB4–RB7 pins.

PORT C and PORT D

In the PIC18F452 microcontroller PORTC is multiplexed with several peripheral

functions. On a power-on reset, PORTC pins are configured as digital inputs. In the PIC18F452

microcontroller, PORTD has Schmitt trigger input buffers. On a power-on reset, PORTD is

configured as digital input. PORTD can be configured as an 8-bit parallel slave port (i.e., a

microprocessor port) by setting bit 4 of the TRISE register.

PORT E

In the PIC18F452 microcontroller, PORTE is only 3 bits wide. Port E pins are shared

with analog inputs and with parallel slave port read/write control bits. On a power-on reset,

PORTE pins are configured as analog inputs and register ADCON1 must be programmed to

change these pins to digital I/O.

The PIC18F452 microcontroller has four programmable timers which can be used in

many tasks, such as generating timing signals, causing interrupts to be generated at specific time



intervals, measuring frequency and time intervals, and so on. This section introduces the timers

available in the PIC18F452 microcontroller.

3.2.4 FEATURES OF PIC 18F452

Power Supply

PIC18F452 can operate with a supply voltage of 4.2V to 5.5V at the full speed of

40MHz. The lower power version, PIC18F452, can operate from 2.0 to 5.5 volts. At lower

voltages the maximum clock frequency is 4MHz, which rises to 40MHz at 4.2V. The RAM data

retention voltage is specified as 1.5V and will be lost if the power supply voltage is lowered

below this value. In practice, most microcontroller-based systems are operated with a single 5V

supply derived from a suitable voltage regulator.

Reset

The reset action puts the microcontroller into a known state. Resetting a PIC18F

microcontroller starts execution of the program from address 0000H of the program memory.

The microcontroller can be reset during one of the following operations:

1. Power-on reset (POR)

2. MCLR reset

3. Watchdog timer (WDT) reset

4. Brown-out reset (BOR)

5. Reset instruction

Power-on Reset

The power-on reset is generated automatically when power supply voltage is applied to

the chip. The MCLR pin should be tied to the supply voltage directly or, preferably, through a

10K resistor.

For applications where the rise time of the voltage is slow, it is recommended to use a

diode, a capacitor, and a series resistor. In some applications the microcontroller may have to be



reset externally by pressing a button. Normally the MCLR input is at logic1.When the RESET

button is pressed, this pin goes to logic 0 and resets the microcontroller.

The Clock Sources

The PIC18F452 microcontroller can be operated from an external crystal or ceramic

resonator connected to the microcontroller’s OSC1 and OSC2 pins. In addition, an external

resistor and capacitor, an external clock source and in some models internal oscillators can be

used to provide clock pulses to the microcontroller.

Watchdog Timer

In PIC18F-series microcontrollers family members the watchdog timer (WDT) is a free

running on-chip RC-based oscillator and does not require any external components.

When the WDT times out, a device RESET is generated. If the device is in SLEEP mode,

the WDT time-out will wake it up and continue with normal operation. The watchdog is

enabled / disabled by bit SWDTEN of register WDTCON. Setting SWDTEN = 1 enables the

WDT, and clearing this bit turns off the WDT. On the PIC18F452 microcontroller an 8-bit post

scalar is used to multiply the basic time-out period from 1 to 128 in powers of 2. This post scalar

is controlled from configuration register CONFIG2H. The typical basic WDT time-out period is

18ms for a post scalar value of 1.

The PIC18F452 has five parallel ports named PORTA, PORTB, PORTC, PORTD, and

PORTE. Most port pins have multiple functions. For example, PORTA pins can be used as

parallel inputs-outputs or analog inputs. PORTB pins can be used as parallel inputs-outputs or as

interrupt inputs.

Timers

The PIC18F452 microcontroller has four programmable timers which can be used in

many tasks, such as generating timing signals, causing interrupts to be generated at specific time

intervals, measuring frequency and time intervals, and so on.



Timer 0:

Timer 0 is similar to the PIC16 series. Timer 0, except that it can operate either in 8-bit or

in 16-bit mode. Timer 0 has the following basic features:

8-bit or 16-bit operation

8-bit programmable pre scalar

External or internal clock source

Interrupt generation on overflow

Timer 0 control register is T0CON, shown in Figure 2.24. The lower 6 bits of this register

have similar functions to the PIC16-series OPTION register. The top two bits are used to select

the 8-bit or 16-bit mode of operation and to enable/disable the timer.

Timer 1: PIC18F452 Timer 1 is a 16-bit timer controlled by register T1CON

Timer 2: Timer 2 is an 8-bit timer with the following features:

8-bit timer (TMR2)

8-bit period register (PR2)

Programmable pre-scalar

Programmable post-scalar

Interrupt when TM2 matches PR2

Timer 3: The structure and operation of Timer 3 is the same as for Timer 1, having registers

TMR3H and TMR3L.

Capture/Compare/PWM Modules (CCP)

The PIC18F452 microcontroller has two capture/compare/PWM (CCP) modules, and

they work with Timers 1, 2, and 3 to provide capture, compare, and pulse width modulation

(PWM) operations. Each module has two 8-bit registers.



Analog-to-Digital Converter (A/D) Module

An analog-to-digital converter (A/D) is another important peripheral component of a

micro controller. The A/D converts an analog input voltage into a digital number so it can be

processed by a microcontroller or any other digital system. There are many analog-to-digital

converter chips available on the market, and an embedded systems designer should understand

the characteristics of such chips so they can be used efficiently.

Interrupts

The PIC18F452 microcontroller has both core and peripheral interrupt sources.

The core interrupt sources are:

External edge-triggered interrupt on INT0, INT1, and INT2 pins.

PORTB pins change interrupts (any one of the RB4–RB7 pins changing state)

Timer 0 overflow interrupt

The peripheral interrupt sources are:

Parallel slave port read/write interrupt

A/D conversion complete interrupt

USART receive interrupt

USART transmit interrupt

Synchronous serial port interrupt

CCP1 interrupt

TMR1 overflow interrupt

TMR2 overflow interrupt

Comparator interrupt



3.2.5 MEMORY ORGANIZATION

Program Memory Organization

All PIC18F devices have a 21-bit program counter and hence are capable of addressing

2Mbytes of memory space. User memory space on the PIC18F452 microcontroller is 00000H to

7FFFH. Accessing a nonexistent memory location (8000H to 1FFFFFH) will cause a read of all

0s. The reset vector, where the program starts after a reset, is at address 0000. Addresses 0008H

and 0018H are reserved for the vectors of high-priority and low-priority interrupts respectively,

and interrupt service routines must be written to start at one of these locations.

The PIC18F microcontroller has a 31-entry stack that is used to hold the return addresses

for subroutine calls and interrupt processing. The stack is not part of the program or the data

memory space. The stack is controlled by a 5-bit stack pointer which is initialized to 00000 after

a reset. During a subroutine call (or interrupt) the stack pointer is first incremented, and the

memory location it points to is written with the contents of the program counter. During the

return from a subroutine call (or interrupt), the memory location the stack pointer has pointed to

is decremented. The projects in this book are based on using the C language.

Program memory is addressed in bytes, and instructions are stored as two bytes or four

bytes in program memory. The least significant byte of an instruction word is always stored in an

even address of the program memory.

An instruction cycle consists of four cycles: A fetch cycle begins with the program

counter incrementing in Q1. In the execution cycle, the fetched instruction is latched into the

instruction register in cycle Q1. This instruction is decoded and executed during cycles Q2, Q3,

and Q4. A data memory location is read during the Q2 cycle and written during the Q4 cycle.

Data Memory Organization

The data memory address bus is 12 bits with the capability to address up to 4Mbytes. The

memory in general consists of sixteen banks, each of 256 bytes, where only 6 banks are used.

The PIC18F452 has 1536 bytes of data memory (6 banks of 256 bytes each) occupying the lower



end of the data memory. Bank switching happens automatically when a high-level language

compiler is used, and thus the user need not worry about selecting memory banks during

programming.

The special function register (SFR) occupies the upper half of the top memory bank. SFR

contains registers which control operations such as peripheral devices, timers/ counters, A/D

converter, interrupts, and USART.

3.2.6 ARCHITECTURE OF PIC 18F452

Fig9: Architecture of PIC 18f452



CHAPTER 4: SERIAL COMMUNICATION

4.1 INTRODUCTION:

Computers transfer data in two ways: parallel and serial. In parallel data transfers, often 8

or more lines (wire conductors) are used to transfer data to a device that is only a few feet away.

Examples of parallel transfers are printers and hard disks; each uses cables with many wire

strips. Although in such cases a lot of data can be transferred in a short amount of time by using

many wires in parallel, the distance cannot be great.

To transfer to a device located many meters away, the serial method is used. In serial

communication, the data is sent one bit at a time, in contrast to parallel communication, in which

the data is sent a byte or more at a time. The 8051 has serial communication capability built into

it, thereby making possible fast data transfer using only a few wires.

When a microprocessor communicates with the outside world, it provides the data in

byte-sized chunks. In some cases, such as printers, the information is simply grabbed from the 8-

bit data bus of the printer. This can work only if the cable is not too long, since long cables

diminish and even distort signals. The Figures shows serial versus parallel data transfers

Peer-to-peer connection

Many-to-many connection

Fig10: Communication Process


Sender

Receiver

Sender

Receiver


The fact that in serial communication a single data line is used instead of the 8-bit data

line of parallel communication makes it not only much cheaper but also makes it possible for two

computers located in two different cities to communicate over the telephone. For serial data

communication to work the byte of data must be converted to serial bits using a parallel-in-

serial-out shift register; then it can be transmitted over a single data line. This also means that at

the receiving end there must be a serial-in-parallel-out shift register to receive the serial data and

pack them into a byte. Of course, if data is to be transferred on the telephone, it must be

converted from 0s and 1s to audio tones, which are sinusoidal-shaped signals. This conversion is

performed by a peripheral device called modem, which stands for “modulator/ demodulator.”

When the distance is short, the digital signal can be transferred as it is on a simple wire

and requires no modulation. This is how IBM PC keyboards transfer data to the motherboard.

However, for long-distance data transfers using communication lines such as a telephone, serial

data communication requires a modem to modulate (convert from 0s and 1s to audio tones) and

demodulate (converting from audio tones to 0s and 1s).

Serial data communication uses two methods, asynchronous and synchronous. The

synchronous method transfers a block of data (characters) at a time while the asynchronous

transfers a single byte at a time. It is possible to write software to use either of these methods, but

the programs can be tedious and long. For this reason, there are special IC chips made by many

manufacturers for serial data communications. These chips are commonly referred to as UART

(Universal Asynchronous Receiver-Transmitter) and USART (Universal Synchronous-

Asynchronous Receiver-Transmitter). The 8051 chip has a built-in UART.

Data transfer rate: The rate of data transfer in serial data communication is stated in bps (bits

per second). Another widely used terminology for bps is baud rate. However, the baud and bps

rates are not necessarily equal. This is due to the fact that baud rate is the modem terminology

and is defined as the number of signal changes per second. In modems, there are occasions when

a single change of signal transfers several bits of data. As far as the conductor wire is concerned,

the baud rate and bps are the same.



The data transfer rate of a given computer system depends on communication ports

incorporated into that system. For example, the early IBM PC/XT could transfer data at the rate

of 100 to 9600 bps. However in recent years, Pentium-based PCs transfer data at rates as high as

56K bps. It must be noted that in asynchronous serial data communication, the baud rate is

generally limited to 100,000 bps.

4.2 RS232 STANDARDS

To allow compatibility among data communication equipment made by various

manufacturers, an interfacing standard called RS232 was set by the Electronics Industries

Association (EIA) in 1960. In 1963 it was modified and called RS232A. RS232B and RS232C

were issued in 1965 and 1969, respectively. Today, RS232 is the most widely used serial I/O

interfacing standard. This standard is used in PCs and numerous types of equipment. However,

since the standard was set long before the advent of the TTL logic family, its input and output

voltage levels are not TTL compatible. In RS232, a 1 is represented by -3 to -25V, while a 0 bit

is +3 to +25V, making -3 to +3 undefined. For this reason, to connect any RS232 to a

microcontroller system we must use voltage converters such as MAX232 to convert the TTL

logic levels to the RS232 voltage level, and vice versa. MAX232 IC chips are commonly

referred to as line drivers.

Connection to RS232

The details of the physical connections of the 8051 to RS232 connectors are given here.

The RS232 standard is not TTL compatible; therefore, it requires a line driver such as the

MAX232 chip to convert RS232 voltage levels to TTL levels, and vice versa. The interfacing of

8051 with RS232 connectors via the MAX232 chip is discussed here.

4.3 MAX232

Since the RS232 is not compatible with today’s microprocessors and microcontrollers, a

line driver (voltage converter) is needed to convert the RS232’s signals to TTL voltage levels

that will be acceptable to the 8051’s TxD and RxD pins. One example of such a converter is



MAX232 from Maxim Corp. The MAX232 converts from RS232 voltage levels to TTL voltage

levels, and vice versa.

One advantage of the MAX232 chip is that it uses a +5V power supply we can power

both the 8051 and MAX232, with no need for the dual power supplies that are common in many

older systems. The MAX232 has two sets of line drivers for transferring and receiving data. The

line drivers used for TxD are called T1 and T2, while the line drivers for RxD are designated as

R1 and R2. In many applications only one of each is used.

RxD and TxD pins in the 8051: The 8051 has two pins that are used specifically for

transferring and receiving data serially. These two pins are called TxD and RxD and are part of

the port 3 group (P3.0 and P3.1). Pin 11 of the 8051 (P3.1) is assigned to TxD and pin 10 (P3.0)

is designated as RxD. These pins are TTL compatible; therefore, they require a line driver to

make them RS232 compatible. One such line driver is the MAX232 chip.

Baud rate in the 8051: The 8051 transfers and receives data serially at many baud rates. The

baud rate in the 8051 is programmable. This is done with the help of timer 1.The relationship

between the crystal frequency and the baud rate is discussed here.

The 8051 divides the crystal frequency by 12 to get the machine cycle frequency. In the

case of XTAL = 11.0592 MHz, the machine cycle frequency is 921.6 kHz (11.0592 MHz / 12 =

921.6 kHz). The 8051’s serial communication UART circuitry divides the machine cycle

frequency of 921.6 kHz by 32 once more before timer 1 to set the baud rate uses it. Therefore,

921.6 kHz divided by 32 gives 28,800 Hz.

To get the baud rates compatible with the PC, we must load TH1 with the values shown

in table given below. The values shown in this table are the Baud rates supported by

486/Pentium IBM PC BIOS.

2400

4800

9600

19200

Table 1: Baud rates



CHAPTER 5: SOFTWARE TOOLS

5.1 INTRODUCTION

OrCAD-Circuit Design:

This tool is used to design the schematic of the hardware.

Using Orcad the PCB layout is designed

Keil IDE’s:

This tool is used to develop the source code needed for the design.

The tool helps us not only to develop but also compile the code and simulate the code.

The keil tool is also used to convert the compiled Embedded C code to its equivalent hex

code.

Flash Programmer:

Flash programmer is used to fuse the built hex code into the Microcontroller AT89c51.

Language: Embedded C.

5.2 ORCAD CAPTURE CIS

OrCAD Capture CIS is designed to reduce production delays and cost overruns through

efficient management of components. It reduces the time spent searching existing parts for reuse,

manually entering part information content, and maintaining component data. Users search parts

based on their electrical characteristics and OrCAD Capture CIS automatically retrieves the

associated part. Flexible and scalable, the solution is quickly implemented. OrCad Capture CIS is

ideal for individual design teams or multi-site teams who need to collaborate across multiple

locations, OrCAD Capture CIS gives designers access to correct part data early in the design

process and enables complete component.

Specifications to be passed to board designers and other members of the design team,

reducing the potential for downstream errors. It provides access to cost information so designers

can use preferred, lower cost, and in stock parts. The embedded part selector accesses



information stored in MRP/ERP systems and engineering databases and synchronizes externally

sourced data with the schematic design database, so bills of materials can be automatically

generated.

5.2.1 BENEFITS

• Provides fast, intuitive schematic editing.

• Boosts schematic editing efficiency by design reuse

• Automates the integration of FPGA and PLD devices

• Makes changes quickly through a single spreadsheet editor

• Imports and exports virtually every commonly used design file format

• Reduces delays caused by out-of-stock parts (CIS)

• Promotes reuse of preferred components (CIS)

• Encourages reuse of known good part data (CIS)

• Makes reuse of duplicate circuitry easy through hierarchical blocks (CIS)

Fig11: Schematic Layout

5.3 KEIL C COMPILER:

Keil Software publishes one of the most complete development tool suites for 8051

software, which is used throughout industry. For development of C code, their Developer's Kit



product includes their C51 compiler, as well as an integrated 8051 simulator for debugging. A

demonstration version of this product is available on their website, but it includes several

limitations

The C programming language was designed for computers, though, and not embedded

systems. It does not support direct access to registers, nor does it allow for the reading and

setting of single bits, two very important requirements for 8051 software. In addition, most

software developers are accustomed to writing programs that will be executed by an operating

system, which provides system calls the program may use to access the hardware. However,

much code for the 8051 is written for direct use on the processor, without an operating system.

To support this, the Keil compiler has added several extensions to the C language to replace what

might have normally been implemented in a system call, such as the connecting of interrupt

handlers.

The purpose of this manual is to further explain the limitations of the Keil compiler, the

modifications it has made to the C language, and how to account for these in developing

software for the 8051 microcontroller.

KEIL LIMITATIONS

There are several very important limitations in the evaluation version of Keil's

Developer's Kit that users need be aware of when writing software for the 8051.

Object code must be less than 2 Kbytes

The compiler will compile any-sized source code file, but the final object code may not

exceed 2 Kbytes. If it does, the linker will refuse to create a final binary executable (or HEX file)

from it. Along the same lines, the debugger will refuse any files that are over 2Kbytes, even if

they were compiled using a different software package.

Program code starts at address 0x4000

All C code compiled and linked using the Keil tools will begin at address 0x4000 in code

memory. Such code may not be programmed into devices with less than 16Kbytes of Read-Only

Memory. Code written in assembly may circumvent this limitation by using the "origin"



keyword to set the start to address 0x0000. No such work-around exists for C programs, though.

However, the integrated debugger in the evaluation software may still be used for testing code.

Once tested, the code may be compiled by the full version of the Keil software, or by another

compiler that supports the C extensions used by Keil.

C MODIFICATIONS

The Keil C compiler has made some modifications to another wise ANSI-compliant

implementation of the C programming language. These modifications were made solely to

facilitate the use of a higher-level language like C for writing programs on microcontrollers.

Variable Types

The Keil C compiler supports most C variable types and adds several of its own.

Standard Types

The evaluation version of the Keil C compiler supports the standard ANSI C variable

types, with the exception of the floating-point types. These types are summarized below.

Type Bits Bytes Range

Char 8 1 -128 to +127

Unsigned char 8 1 0 to 255

Enum 16 2 -32,768 to +32,767

Short 16 2 -32,768 to +32,767

Unsigned short 16 2 0 to 65,535

Int 16 2 -32,768 to +32,767

Unsigned int 16 2 0 to 65,535

Long 32 4-2,147,483,648 to

+2,147,483,647

Unsigned long 32 4 0 to 4,294,697,295

Table2: Embedded Specifications



In addition to these variable types, the compiler also supports the struct and union data

structures, as well as type redefinition using typedef.

Keil Types

To support a microcontroller and embedded systems applications, Keil added several new

types to their compiler. These are summarized in the table below.

Type Bits Bytes Range

Bit 1 0 0 to 1

Sbit 1 0 0 to 1

Sfr 8 1 0 to 255

sf16 16 2 0 to 65,535

Table3: keil specifications

Of these, only the bit type works as a standard variable would. The other three have

special behavior that a programmer must be aware of.

bit

This is a data type that gets allocated out of the 8051's bit-addressable on-chip RAM.

Like other data types, it may be declared as either a variable. However, unlike standard C types,

if may not be used as a pointer.

Sbit, sfr, and sf16

These are special types for accessing 1-bit, 8-bit, and 16-bit special function registers.

Because there is no way to indirectly address registers in the 8051, addresses for these variables

must be declared outside of functions within the code. Only the data addressed by the variable

may be manipulated in the code.

Conveniently, the standard special function registers are all defined in the reg51.h file

that any developer may include into their source file. Only registers unique to the particular



8051-derivative being used for the project need have these variable declared, such as registers

and bits related to a second on-chip serial port.

Keil Variable Extensions

In writing applications for a typical computer, the operating system handles manages

memory on behalf of the programs, eliminating their need to know about the memory structure

of the hardware. Even more important, most computers having a unified memory space, with the

code and data sharing the same RAM. This is not true with the 8051, which has separate memory

spaces for code, on-chip data, and external data.

To accommodate for this when writing C code, Keil added extensions to variable

declarations to specify which memory space the variable is allocated from, or points to. The most

important of these for student programmers are summarized in the following table.

Extension Memory Type Related ASM

DataDirectly-addressable data memory (data

memory addresses 0x00-0x7F)MOV A, 07Fh

IdataIndirectly-addressable data memory

(data memory addresses 0x00-0xFF)

MOV R0, #080h

MOV A, R0

Xdata External data memory MOVX @DPTR

Code Program memory MOVC @A+DPTR

Table 4: Variable Extensions

These extensions may be used as part of the variable type in declaration or casting by

placing the extension after the type, as in the example below. If the memory type extension is not

specified, the compiler will decide which memory type to use automatically, based on the

memory model.



Keil Function Extensions

Keil provides two important extensions to the standard function declaration to allow for

creation of interrupt handlers and reentrant functions.

Fig 12: Keil Programming

5.4 FLASH PROGRAMMER

This ISP Programmer can be used either for in-system programming or as a stand-alone

SPI programmer for Atmel ISP programmable devices. The programming interface is compatible

to STK200 ISP programmer hardware so the users of STK200 can also use the software which

can program both the 8051 and AVR series devices.



HARDWARE

fig13: Circuit Diagram of the In-System Programmer Interface

The power to the interface is provided by the target system. The 74HCT541 IC isolates

and buffers the parallel port signals. It is necessary to use the HCT type IC in order to make sure

the programmer should also work with 3V type parallel port.

SOFTWARE

The ISP-30a.zip file contains the main program and the I/O port driver. Place all files in

the same folder. The main screen view of the program is shown in figure9.4.2.

Also make sure do not program the RSTDISBL fuse in

ATmega8, ATtiny26 and ATtiny2313otherwise further SPI programming is disable and you

will need a parallel programmer to enable the SPI programming. For the fuses setting

consult the datasheet of the respective device. For the auto hardware detection it is necessary to

short pin 2 and 12 of DB25 connector, otherwise the software uses the default parallel port i.e.

LPT1.



Fig14: Main screen of the program ISP-Pgm Ver 3.0a



CHAPTER 6: HARDWARE TOOLS

The following are the hardware components used:

PIC 18F452 and 89s51 micro controller

RF transmitter and Receiver

Encoder and decoder

GSM modem

Power supply unit

Buzzer and Stepper motor

LCD display

6.1 GSM MODEM:

Definition:

Global system for mobile communication (GSM) is a globally accepted standard for

digital cellular communication. GSM is the name of a standardization group established in 1982

to create a common European mobile telephone standard that would formulate specifications for

a pan-European mobile cellular radio system operating at 900MHz.

6.1.1 GSM NETWORK

GSM provides recommendations, not requirements. The GSM specifications define the

functions and interface requirements in detail but do not address the hardware. The reason for

this is to limit the designers as little as possible but still to make it possible for the operators to

buy equipment from different suppliers. The GSM network is divided into three major systems:

the switching system (SS), the base station system (BSS), and the operation and support system

(OSS). The basic GSM network elements are shown in below figure



Fig15: GSM Network Elements

GSM MODEM:

A GSM modem is a wireless modem that works with a GSM wireless network. A

wireless modem behaves like a dial-up modem. The main difference between them is that a dial-

up modem sends and receives data through a fixed telephone line while a wireless modem sends

and receives data through radio waves.

A GSM modem can be an external device or a PC Card / PCMCIA Card. Typically, an

external GSM modem is connected to a computer through a serial cable or a USB cable. A GSM

modem in the form of a PC Card / PCMCIA Card is designed for use with a laptop computer. It

should be inserted into one of the PC Card / PCMCIA Card slots of a laptop computer. Like a

GSM mobile phone, a GSM modem requires a SIM card from a wireless carrier in order to

operate.

As mentioned in earlier sections of this SMS tutorial, computers use AT commands to

control modems. Both GSM modems and dial-up modems support a common set of standard AT

commands. You can use a GSM modem just like a dial-up modem.

In addition to the standard AT commands, GSM modems support an extended set of AT

commands. These extended AT commands are defined in the GSM standards. With the extended

AT commands, you can do things like:



Reading, writing and deleting SMS messages.

Sending SMS messages.

Monitoring the signal strength.

Monitoring the charging status and charge level of the battery.

Reading, writing and searching phone book entries.

The number of SMS messages that can be processed by a GSM modem per minute is

very low -- only about six to ten SMS messages per minute.

6.1.2 FACTS OF GSM/GPRS MODEM:

The GSM/GPRS Modem comes with a serial interface through which the modem can be

controlled using AT command interface. An antenna and a power adapter are provided. The

basic segregation of working of the modem is as under

• Voice calls

• SMS

Voice calls:

Voice calls are not an application area to be targeted. In future if interfaces like a

microphone and speaker are provided for some applications then this can be considered.

SMS:

SMS is an area where the modem can be used to provide features like:

• Pre-stored SMS transmission

• These SMS can be transmitted on certain trigger events in an automation system

• SMS can also be used in areas where small text information has to be sent.

The navigator keeps on sending SMS at particular time intervals. SMS can be a solution

where GSM data call or GPRS services are not available.

6.1.3 APPLICATIONS SUITABLE FOR GSM COMMUNICATION:



If your application needs one or more of the following features, GSM will be more cost-

effective then other communication systems.

Short Data Size:

You data size per transaction should be small like 1-3 lines. E.g. banking transaction

data, sales/purchase data, consignment tracking data, updates. These small but important

transaction data can be sent through SMS messaging which cost even less than a local telephone

call or sometimes free of cost worldwide. Hence with negligible cost you are able to send critical

information to your head office located anywhere in the world from multiple points.

You can also transfer faxes, large data through GSM but this will be as or more costly

compared to landline networks.

Multiple remote data collection points:

If you have multiple data collections points situated all over your city, state, country or

worldwide you will benefit the most. The data can be sent from multiple points like your branch

offices, business associates, warehouses, and agents with devices like GSM modems connected

to PCs, GSM electronic terminals and Mobile phones. Many a times some places like

warehouses may be situated at remote location may not have landline or internet but you will

have GSM network still available easily.

High uptime:

If your business require high uptime and availability GSM is best suitable for you as

GSM mobile networks have high uptime compared to landline, internet and other

communication mediums. Also in situations where you expect that someone may sabotage your

communication systems by cutting wires or taping landlines, you can depend on GSM wireless

communication.

Large transaction volumes:

GSM SMS messaging can handle large number of transaction in a very short time. You

can receive large number SMS messages on your server like e-mails without internet



connectivity. E-mails normally get delayed a lot but SMS messages are almost instantaneous for

instant transactions. Consider situation like shop owners doing credit card transaction with GSM

technology instead of conventional landlines. time you find local transaction servers busy as

these servers use multiple telephone lines to take care of multiple transactions, whereas one

GSM connection is enough to handle hundreds of transaction.

Mobility, Quick installation:

GSM technology allows mobility, GSM terminals, modems can be just picked and

installed at other location unlike telephone lines. Also you can be mobile with GSM terminals

and can also communicate with server using your mobile phone. You can just purchase the GSM

hardware like modems, terminals and mobile handsets, insert SIM cards, configure software and

are ready for GSM communication.

6.2 RS 232

When we look at the connector pin out of the RS232 port, we see two pins which are

certainly used for flow control. These two pins are RTS, request to send and CTS, clear to send.

With DTE/DCE communication (i.e. a computer communicating with a modem device) RTS is

an output on the DTE and input on the DCE. CTS are the answering signal coming from the

DCE.

Before sending a character, the DTE asks permission by setting its RTS output. No

information will be sent until the DCE grants permission by using the CTS line.

If the DCE cannot handle new requests, the CTS signal will go low. A simple but useful

mechanism allowing flow control in one direction. The assumption is that the DTE can always

handle incoming information faster than the DCE can send it. In the past, this was true. Modem

speeds of 300 baud were common and 1200 baud was seen as a high speed connection.

For further control of the information flow, both devices have the ability to signal their

status to the other side. For this purpose, the DTR data terminal ready and DSR data set ready



signals are present. The DTE uses the DTR signal to signal that it is ready to accept information,

whereas the DCE uses the DSR signal for the same purpose.

The last flow control signal present in DTE/DCE communication is the CD carrier

detect. It is not used directly for flow control, but mainly an indication of the ability of the

modem device to communicate with its counterpart. This signal indicates the existence of a

communication link between two modem devices.

6.2.1 MAX 232

MAX-232 is primary used for people building electronics with an RS-232 interface.

Serial RS-232 communication works with voltages (-15V ... -3V for high) and +3V ... +15V for

low) which are not compatible with normal computer logic voltages. In the other direction

(sending data from some logic over RS-232) the low logic voltage has to be "bumped up", and a

negative voltage has to be generated.

Fig16: Pin Diagram of Max 232

6.3 RF MODULES

Radio Frequency-any frequency within the electromagnetic spectrum associated with

radio wave propagation. When an RF current is supplied to an antenna, an electromagnetic field

is created that then is able to propagate through space. Many wireless technologies are based on

RF field propagation.



Receiver Module Transmitter Module

Fig17: RF module

Radio Frequency: The 10 kHz to 300 GHz frequency range that can be used for wireless

communication. Generally refers to the radio signal generated by the system transmitter, or to

energy present from other sources that may be picked up by a wireless receiver.

Applications:

Wireless mouse, keyboard

Wireless data communication

Alarm and security systems

Home Automation, Remote control

Automotive Telemetry

Intelligent sports equipment

Industrial telemetry and Tele-communications

In-building environmental monitoring and control

High-end security and fire alarms

6.3.1 TRANSMITTER

The TWS-434 extremely small, and are excellent for applications requiring short-range

RF remote controls. The transmitter module is only 1/3 the size of a standard postage stamp,

and can easily be placed inside a small plastic enclosure.

TWS-434: The transmitter output is up to 8mW at 433.92MHz with a range of approximately

400 foot (open area) outdoors. Indoors, the range is approximately 200 foot, and will go through

most walls.


http://www.rentron.com/images/tws434.jpg


Fig18: Transmitter

The TWS-434 transmitter accepts both linear and digital inputs can operate from 1.5 to

12 Volts-DC, and makes building a miniature hand-held RF transmitter very easy. The

TWS=434 is approximately 1/3 the size of a standard postage stamp.

PIN DIAGRAM

Fig19: Tws-434 Pin Diagram

6.3.2 RECEIVER

Fig20: Receiver

RWS-434: The receiver also operates at 433.92MHz, and has a sensitivity of 3uV. The WS-434

receiver operates from 4.5 to 5.5 volts-DC, and has both linear and digital outputs.

PIN DIAGRAM


http://www.rentron.com/images/tws434.jpg


Fig21: Pin out Diagram

Application circuit for transmitter and receiver

Fig22: Application circuit

Generating Data



The TWS-434 modules do not incorporate internal encoding. If you want to send simple

control or status signals such as button presses or switch closures, consider using an encoder and

decoder IC set that takes care of all encoding, error checking, and decoding functions. Motorola

and Holtek make these chips. They are an excellent way to implement basic wireless

transmission control.

Receiver Data Output

A 0V to Vcc data output is available on pins. This output is normally used to drive a

digital decoder IC or a microprocessor which is performing the data decoding. The receiver’s

output will only transition when valid data is present. In instances, when no carrier is present the

output will remain low.

Decoding Data

The RWS-434 modules do not incorporate internal decoding. If you want to receive

Simple control or status signals such as button presses or switch closes, you can use the encoder

and decoder IC set described above. Decoders with momentary and latched outputs are available.

Transmitting and Receiving

Full duplex or simultaneous two-way operation is not possible with these modules. If

transmit and receive module are in close proximity and data is sent to a remote receive module

while attempting to simultaneously receive data from a remote transmit module, the receiver will

be overloaded by its close proximity transmitter. This will happen even if encoders and decoders

are used with different address settings for each transmitter and receiver pair. If two way

communications is required, only half duplex operation is allowed.

Antennas- Wire Whip



The WC418 is made of 26-gauge carbon steel music wire that can be soldered to a PC board.

This antenna has a plastic coated tip for safety and is 6.8 inches long, allowing .1 inch for insertion

in a terminal or PC board.

Fig 23: Antenna

Antenna

The following should help in achieving optimum antenna performance:

Proximity to objects such a users hand or body, or metal objects will cause an antenna to

detune. For this reason the antenna shaft and tip should be positioned as far away from

such objects as possible.

Optimum performance will be obtained from a one-forth or half wave straight whip

mounted at a right angle to the ground plane. A one-forth wave antenna for 418 MHz is

6.7 inches long.

6.4 ENCODER AND DECODER

6.4.1 ENCODER (HT-12E)

The Encoder, which we are using in our project, is HT12E series, which is a Holtek, made

Encoder. The 212 encoders are a series of CMOS LSIs for remote control system applications.

They are capable of encoding information, which consists of N address bits and 12_N data bits.

Each address/ data input can be set to one of the two logic states. The programmed

addresses/data are transmitted together with the header bits via an RF or an infrared transmission

medium upon receipt of a trigger signal. The capability to select a TE trigger on the HT12E

enhances the application flexibility o f the 212 series of encoders.

6.4.2 FEATURES

Operating voltage 2.4V~12V for the HT12E



Low power and high noise immunity CMOS technology

Built-in oscillator needs only 5% resistor

HT12E: 18-pin DIP/20-pin SOP package

6.4.3 PIN DIAGRAM

Fig24: Encoder Pin Diagram

PIN DESCRIPTION



Table 5: Pin Description of Encoder

6.4.4 DECODER (HT-12D)

The Decoder, which we are using in our project, is HT12D series, which is a Holtek, made

Decoder. The 2 12 decoders are a series of CMOS LSIs for remote control system applications.

For proper operation, a pair of encoder/decoder with the same number of addresses and data

format should be chosen. They compare the serial input data three times continuously with their

local addresses. If no error or unmatched codes are found, the input data codes are decoded and

then transferred to the output pins. Of this series, the HT12D is arranged to provide 8 address

bits and 4 data bits.

6.4.5 FEATURES

Operating voltage: 2.4V~12V

Low power and high noise immunity CMOS technology

Low standby current

Capable of decoding 12 bits of information

Received codes are checked 3 times

Built-in oscillator needs only 5% resistor



6.4.6 PIN DIAGRAM

Fig25: Decoder pin diagram

PIN DESCRIPTION

Table6: Pin Description of Decoder

6.5 LCD DISPLAY (2X16 Character)

Dot matrix LCD modules is used for display the parameters and fault condition.16

characters 2 lines display is used. It has controller which interface data’s and LCD panel.

Liquid crystal displays (LCD’s) have materials, which combine the properties of both liquids and

crystals. Rather than having a melting point, they have a temperature range within which the

molecules are almost as mobile as they would be in a liquid, but are grouped together in an

ordered form similar to a crystal. An LCD consists of two glass panels, with the liquid crystal

material sandwiched in between them. The inner surface of the glass plates are coated with

transparent electrodes which define the character, symbols or patterns to be displayed polymeric

layers are present in between the electrodes and the liquid crystal molecules to maintain a

defined orientation angle.



One each polarizer’s are pasted outside the two glass panels. These polarizer’s would

rotate the light rays passing through them to a definite angle, in a particular direction When the

LCD is in the off state, light rays are rotated by the two polarizes and the liquid crystal, such that

the light rays come out of the LCD without any orientation, and hence the LCD appears

transparent.

When sufficient voltage is applied to the electrodes, the liquid crystal molecules would be

aligned on a specific direction. The light rays passing through the LCD would be rotated by the

polarizes, which would result in activating/highlighting the desired characters.

Fig 26: LCD Display

The LCD's are lightweight with only a few millimeters thickness. since the LCD's

consume less power, they are compatible with low power electronic circuits, and can be

powered for long durations .The LCD's don't generate light is needed to read the display. By

using backlighting, reading is possible in the dark .The LCD's have long life and a wide

operating temperature range.

One of the most popular output devices for embedded electronics is LCD. The LCD

interface has become very simple. This is due to the availability modules for LCDs. The LCD

along with necessary controller (LCD Controller) and mounting facility is made available in the

module itself. The LCD controller takes care of everything necessary for the LCD. We

communicate with the LCD controller with the help of a command set provided by the

manufacturer.

6.6 BUZZER



Basically, the sound source of a piezoelectric sound component is a piezoelectric

diaphragm. A piezoelectric diaphragm consists of a piezoelectric ceramic plate which has

electrodes on both sides and a metal plate (brass or stainless steel, etc.). A piezoelectric ceramic

plate is attached to a metal plate with adhesives. Applying D.C. voltage between electrodes of a

piezoelectric diaphragm causes mechanical distortion due to the piezoelectric effect. For a

misshaped piezoelectric element, the distortion of the piezoelectric element expands in a radial

direction. And the piezoelectric diaphragm bends toward the direction. The metal plate bonded to

the piezoelectric element does not expand. Conversely, when the piezoelectric element shrinks,

the piezoelectric diaphragm bends in the direction Thus, when AC voltage is applied across

electrodes, the bending is repeated, producing sound waves in the air.

Fig 27: Buzzer

6.7 RELAY

A relay is an electrically operated switch. Current flowing through the coil of the relay

creates a magnetic field which attracts a lever and changes the switch contacts. The coil current

can be on or off so relays have two switch positions and they are double throw (changeover)

switches.

Relays allow one circuit to switch a second circuit which can be completely separate

from the first. For example a low voltage battery circuit can use a relay to switch a 230V AC

mains circuit. There is no electrical connection inside the relay between the two circuits, the link

is magnetic and mechanical.



Relays are very simple devices. There are four major parts in every relay. They are

Electromagnet

Armature that can be attracted by the electromagnet

Spring

Set of electrical contacts

WORKING

When a current flows through the coil, the resulting magnetic field attracts an armature

that is mechanically linked to a moving contact. The movement either makes or breaks a

connection with a fixed contact. When the current to the coil is switched off, the armature is

returned by a force approximately half as strong as the magnetic force to its relaxed position.

Usually this is a spring, but gravity is also used commonly in industrial motor starters. Most

relays are manufactured to operate quickly. In a low voltage application, this is to reduce noise.

In a high voltage or high current application, this is to reduce arcing.

CHOOSING A RELAY:

One needs to consider several features when choosing a relay:

1. Physical size and pin arrangement: If you are choosing a relay for an existing PCB you

will need to ensure that its dimensions and pin arrangement are suitable. You should find

this information in the supplier's catalogue.

2. Coil voltage: The relay's coil voltage rating and resistance must suit the circuit powering

the relay coil. Many relays have a coil rated for a 12V supply but 5V and 24V relays are

also readily available. Some relays operate perfectly well with a supply voltage which is

a little lower than their rated value.



3. Coil resistance: The circuit must be able to supply the current required by the relay coil.

You can use Ohm's law to calculate the current:

Relay coil current = supply voltage / coil resistance

For example: A 12V supply relay with a coil resistance of 400 passes a current of

30mA. Most ICs will require a transistor to amplify the current.

4. Switch ratings (voltage and current): The relay's switch contacts must be suitable for

the circuit they are to control. You will need to check the voltage and current ratings.

Note that the voltage rating is usually higher for AC, for example: "5A at 24V DC or

125V AC".

5. Switch contact arrangement (SPDT, DPDT etc.): Most relays are SPDT or DPDT

which are often described as "single pole changeover" (SPCO) or "double pole

changeover" (DPCO).

Fig 28: Relay

6.8 STEPPER MOTOR

Stepper motors operate differently from DC brush motors, which rotate when voltage is

applied to their terminals. Stepper motors, on the other hand, effectively have multiple "toothed"

electromagnets arranged around a central gear-shaped piece of iron. The electromagnets are

energized by an external control circuit, such as a microcontroller. To make the motor shaft turn,

first one electromagnet is given power, which makes the gear's teeth magnetically attracted to the

electromagnet's teeth. When the gear's teeth are thus aligned to the first electromagnet, they are

slightly offset from the next electromagnet. So, when the next electromagnet is turned on and the

first is turned off, the gear rotates slightly to align with the next one, and from there the process


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is repeated. Each of those slight rotations is called a "step", with an integer number of steps

making a full rotation. In that way, the motor can be turned by a precise angle.

Stepper motor characteristics

1. Stepper motors are constant power devices.

2. As motor speed increases, torque decreases.

3. Steppers exhibit more vibration than other motor types, as the discrete step tends to snap the

rotor from one position to another. The vibration makes stepper motors noisier than DC motors.

4. The effect can be mitigated by accelerating quickly through the problem speeds range,

physically damping the system, or using a micro-stepping driver.

5. Motors with a greater number of phases also exhibit smoother operation than those with

fewer phases

Fig 29: Stepper Motor

CONCLUSION AND FUTURE SCOPE

CONCLUSION

Using Mobile phone while driving is common, but controversial. Certainly there has been

large number of figures that shows that people have used their mobile phones just before their

accidents. Studies have shown that if people reduce their usage of cell phone while driving, it can

reduce the accident rates too.

FUTURE SCOPE



This technology will overcome most of the road accidents occurring as people are using

mobile phone while driving. This technology should be implemented in the cars by the

manufacturers as it has very effective use of preventing road accidents by reducing the speed of

the car whenever the call is answered.

There may be further more development can be seen in this technology in the coming

years as the world has the technology evolving tendency. Further development will solve almost

all the reasons for car accidents using mobile phone.

Fig 30: Sample Model

REFERENCES

Vince Stanford, “ Pervasive computing goes the last hundred feet with RFID systems”,

IEEE pervasive computing

www.keil.com

www.wavecom.com

www.microcontroller.com

www.rentron.com

www.flashprogrammer.com

www.alldatasheets.com


http://www.flashprogrammer.com/


Text books:

1. Raj kamal –“Microcontrollers Architecture, Programming, Interfacing and System Design”

2nd edition, PHI publications

2. Mazidi and Mazidi –Embedded Systems,3rd edition

3. PCB Design Tutorial –David.L.Jones

4. PIC Microcontroller Manual – Microchip.

5. Embedded C –Michael.J.Pont.


Project

Documents

dash board section

mobile number

communication engineering

use of mobile phones

voice message

adaptive hands free

power supply fig1

voice mail process