1

Draft for

Design and Implementation FSK

Remote Control System Using

ATmiga16 Microcontroller A project is just a draft so; many mistakes and grammar errors

will be there. Abdullah

Abdullah A. Mohamed; Khalaf Al-sabaawi

Communication Department

Collages of Electronics Engineering - Mosul university-Iraq

Abdullah.4Mohamed@Gmail.com; khalif.i.taha@gmail.com

Abstract

The meaning of remote control is the controlling of the equipment or devices without

any physical connections and it provide access for the devices that cannot be reached

easily.

There are many approaches for doing remote control one of them is our project which

include FSK techniques.

2

Chapter 1

Introduction

• Many of practical applications (for example, the machines in factory ,

missiles tracking ) require a way to communicate electronically with a central

office , so that measured data can be reported back to the central office and

new tariffs can be set in the remote site and feedback the necessary orders to

the controlled device through the remote controlling unit system . This

controlling order is usually digital codes, in digital signaling we seek to send

one of two logic states. Traditionally we label these states as logic “1” or logic

“0”. In a digital circuit, voltages such as 5v for logic "1" and 0v for logic "0"

usually represent these states. Frequency shift keying (FSK) is one of the most

popular methods of representing digital data. FSK is also known as frequency

shift modulation and frequency shift signaling. FSk is data signal converted

into specific frequency or tone in order to transmit it over wire ,optical fiber

or wireless media to a destination point , and it has many types such as

1. 1_ Binary Frequency Shift Keying (BFSK)

2. 2_ Multiple Frequency Shift Keying (MFSK)

3. 3_Audio frequency-shift keying (AFSK)

4. 4_Minimum frequency-shift keying or minimum-shift keying (MSK)

5. 5_Gaussin Minimum Shift Keying(GMSK)

The simplest FSK is binary FSK (BFSK). BFSK literally implies using a pair of

discrete frequencies to transmit binary (0s and 1s) information. With this scheme,

the "1" is called the mark frequency and the "0" is called the space frequency

3

1.1 Motivation

We choose this project because of most of the modern technique today use the

remote control unite where it provide a good facilities for human.

1.2 Aim of the project

This project aim to build wireless control unit for several devices ( 8 switches

turn on/off ) , and here we used the technique of frequency shift keying (FSK)

Chapter2

Background

The trend in wireless system is overwhelmingly towards digital modulation for a

variety of reasons. An obvious reason is that if we want to transmit digital

information (e.g., digital code) we need to employ digital modulation. However,

even for analog signals like voice, digital modulation is very attractive because in

the digital domain we can employ coding for the purposes of data compression,

encryption, and error correction. These results in a system that makes much more

efficient use of bandwidth and power and can provide a wider array of services for

our customers.

The “real world” is analog. As such we implement digital modulation using analog

systems. For the same reasons that FM is superior to AM for analog radio

communication, most digital schemes employ frequency- or phase-shift techniques.

4

2.1 Digital Signals

In digital signaling, we seek to send one of two logic states. Traditionally we label

these states as logic “1” or logic “0”. In a digital circuit these states are usually

represented by voltages such as 5 V for logic 1 and 0 V for logic 0. In RF it is almost

always more convenient to have a symmetric representation, so we will typically use,

say 1 V for logic 1 and –1 V for logic 0.

Although we ultimately are interested is communicating a stream of discrete bits, we

must implement this with continuous-time signals. Say we wish to send the bit

pattern 010… with one bit being sent every Tb seconds. Tb is called the bit period.

The bit rate, or number of bits per second, is Rb= 1/ Tb .We communicate a bit pattern

by forming a continuous-time function m (t) where m (t) = -1 for 0 ≤ t < Tb

m (t) = +1 for Tb ≤ t <2 Tb , and so on. We then modulate m (t) on to an RF channel,

transmit it, receive and demodulate it, and finally sample it to reconstruct the bit

pattern. In the presence of noise, this process may fail and we might end up with

logic 1 when logic 0 was sent, or vice versa. In this case, we say we have a bit error.

The fraction of all bits that are in error is called the bit error rate or BER. The BER

is the same as the probability that a given bit will be in error, which we write as Pe.

The BER will depend on the choice of modulation (amplitude, phase, frequency) that

we use to send m (t). The modulation scheme will also affect the required RF

bandwidth. One important question is: How much RF bandwidth is required to

communicate at a bit rate Rb? A modulation scheme that uses less RF bandwidth is

said to be more bandwidth efficient. Another important question is: What received

power level is required to achieve a given BER? A modulation scheme that requires

less power is said to be more power efficient. Whether power or bandwidth efficient

is more important depends on our application.

2.2 Frequency Shift Keying (FSK)

Conceptually FSK is very simple. If we wish to send binary data, we associate each

of the two logic states “0” and “1” with distinct frequencies, say, f0 and f1. To send

logic “0” we tune our transmitter to f0; to send logic “1” we tune our transmitter to

f1. An audio analogy would be to press one of two particular keys of a piano to send

“0” or “1”. The receiver need only be able to distinguish between the two

frequencies. This can be accomplished by, for example, using two band-pass filters,

5

one centered at f0 and the other at f1 and seeing which produces the larger output.

Errors occur when noise randomly causes the wrong filter to have a larger response.

FSK can, in theory and in practice, be implemented using analog FM transceivers.

This is an attractive feature and was especially so in the past when analog FM

transceiver technology was much more mature than the corresponding digital

technology. To transmit FSK using analog FM we simply apply one of two discrete

modulation voltages ±1 to the transmitter. At the receiver we do an analog FM

demodulation and ideally the receiver will output the original bit pattern. Recall that

FM produces an RF signal of the form

t

fcc dxxmktfAtS0

)(22cos)(

We take m (t) to be a binary signal, i.e., m(t) = ±1 . Since the amplitude of the

modulating signal is unity, the frequency deviation is equal to the frequency

deviation constant, i.e., Δ f =kf .

The instantaneous frequency is

This takes on one of the two discrete values f = f c ±Δf . Thus, as we claimed, FSK

involves transmitting one of two frequencies to represent one of the two possible

logic states. Logic 1 would be represented by a frequency f1 = f c + Δf and logic 0

by f0= f c – Δf.

An example of an FSK signal is shown in Fig. 2.1

………………………………….. ( 2.1 )

………………………………….. ( 2.2 )

Reference No. ( 1 )

Reference No. ( 1,2 )

6

Figure 2.1: Simulated FSK signal Square wave (thick curve) is the modulating signal. The bit

period is 1. The thin waveform is the resulting “RF” signal.

In this figure, the carrier frequency is 4 and the frequency deviation is 1. So, as seen

in the figure, logic 1 is represented by a frequency of 4+ 1=5 and logic 0 by 4-1=3 .

In a real system, there would be many more oscillations during each bit period.

Recall that for FM we defined the modulation index as β= Δf/fm. For the square-

wave bit pattern shown in Fig. 2.1, the period is 2Tbso the frequency is fm = (1/2T

b)

and β = 2Δ f Tb

.Usually the symbol “h” is used in the FSK case and we write the

modulation index as h = 2Δ f TbAlthough an ideal FM receiver would output m(t) ,

in the presence of noise things are more complicated.

2.3 BER for FSK

In general, to demodulate an FSK signal and recover the modulation m(t) , we need

to determine at which of the frequencies f 0 , f 1 there is more power present during

a given bit period. Ideally all the power would be at one or the other frequency and

then we would know which logic state was being sent. However, we are doing this

in the presence of noise. With noise, it is possible that more power will appear at the

wrong frequency than at the right one, and we will have a bit error. We want to figure

7

out how often this happens mathematically, we can take the approach we use to

calculate Fourier series coefficients namely, multiply by a sinusoid and integrate.

This can be implemented in hardware using mixers and integrators. Assume a logic

“1” is being sent. The received signal will be Ac cosω1t for a period Tb. The receiver

adds noise to give us a total signal of Ac cos1ω t + n (t) . Now calculate the

Fourier coefficient at ω1. We get

The second term X1

is the Fourier coefficient of for the noise. We assume this is a

zero mean Gaussian random variable. Since the time interval is Tb , spectral

components within a bandwidth of B = 1/Tb

will contribute to this. This corresponds

to a noise power of N0B where N0 =kTN is the noise spectral density. Therefore, the

variance is ﴾ Xj2﴿= N0B = N0/ Tb. Now let's calculate the Fourier coefficient at w0.

We get

Here we have assumed that cosw1t and cosw0t are orthogonal over this interval.

This sets a constraint on the difference of the two frequencies, as we will see later.

X0 is another Gaussian random variable with variance N0 / Tb. If ax> a0 then we

conclude, correctly, that the logic level is "1". Otherwise, we make a bit error.

Equivalently, we look at r = ax - a0. If this is positive then we assume logic level

"1" while if it is negative we assume logic level "0". Now r = Ac + X1 -X0. X0,X1

………………………………….. ( 2.3 )

………………………………….. ( 2.4 )

Reference No. ( 1,2 )

Reference No. ( 1,2,3 )

8

are both zero-mean Gaussian RVs with variance N0 / Tb. If they are independent,

then statistical theory tells us that their difference with also be a zero-mean Gaussian

RV with variance a2 = 2N0 / Tb. Therefore r will be a Gaussian RV with mean Ac

and variance a2 = 2N0 / Tb as illustrated in Fig. 2.2.

We make an error in figuring out the logic state if r < 0. The probability of this is

Figure 2.2: PDF of FSK detector output .

9

Let's express Ac /σ in a couple of different ways to get some insight into

this expression. Using σ2 = 2N0 / Tb and Eb = Ac2Tb / 2, we can write

(Ac / σ)2 = Ac2Tb /2N0=Eb/N0, so

Pe = Q(√(Eb/N0))

This is plotted in Fig. 21.5. Given a receiver noise temperature,N0

= KT Nis determined, and this expression tells us the received energy per

bit required to achieve a given BER. For example, from Fig. 2.3 we can see

that to get a BER of about10−3 we would need Eb/N0 to be about 10 db.

The fact that Eb/N0 determines the BER has implications for our bit rate

Rb=1/Tb. With a fixed N0 we need to keep Eb fixed to maintain a given

BER. But Eb=PR,w Tb= PR,W / Rb So, if we increase our bit rate, we must

increase received power by the same amount. Conversely, if received

power decreases, we can maintain our BER by reducing the bit rate. So, the

data rate your radio link will operate at is an important consideration in

determining the required received power.

Recall that for a bandwidth of B=1/Tb and a noise spectral density N0=KTN,

the noise power is PN,W = N0B . Now

Eb /N0 = ( PR,wTb) /N0

= PR,w / (N0B )

= PR,w / PN,W

That is Eb/N0, is also the S/N ratio. However, since the noise power

depends on the bandwidth, which depends on the data rate Eb/N0, is in a

sense a more fundamental quantity.

r

………………………………….. ( 2.5 )

………………………………….. ( 2.6 )

………………………………….. ( 2.7 )

Reference No. ( 2 )

Reference No. ( 2 )

Reference No. ( 2,3 )

10

If the cosine in the signal and the cosine in our detector had the same phase.

This kind of detection scheme we have outlined is a coherent scheme. If

you cannot get phase coherence, you have to use a no coherent detector.

For example, you could compare the amplitudes of the output of two band

pass filters, one tuned to f 0 and the other to f 1 . The analysis is more

difficult than for the coherent case. The result is

Pe=(1/2)𝑒Eb /2N0

This is also plotted in Fig. 2.3 we can see that the BER is higher than for

the coherent detector. Typically, however, less than 1 dB of increase in

signal power will make up the difference.

Solid blue curve corresponds to coherent 0/NbEFigure 2.3 : BER vs

detection; dashed red curve corresponds to incoherent

detection.

………………………………….. ( 2.8 )

Reference No. ( 2,3 )

11

2.4 FSK Spectrum To signal a sequence of logic states, we are sending a series of pulses of

the form (2.4) each with frequency or f1 = f c +Δf or f0 = f c - Δf. We

might be inclined to think that the power spectrum of an FSK signal would

therefore consist of two squared sincs, one centered at f0 and one at f

1. This

is more-or-less true if the frequency deviation is greater than or about equal

to the width of one sinc, namely 1/Tb , . For the waveform shown in Fig.

2.1, the power spectrum is as shown in Fig. 2.5

Figure 2.4: The sinc function, sinc function squared, and rect“Figure 2.4 energy” of sinc

90% of energy lies in the main lobe (i.e، between –1 and 1)) of the energy lies between –

10 and 10% 99 “energy” of sinc2lies in the main lobe (i.e.، between –1 and 1.) 99% of the

energy lies between –10 and

12

For this situation we can estimate the bandwidth as the difference of the

frequencies f0 and f1, which is 2∆f, plus half the width of the lower sinc,

plus half the width of the upper sinc, i.e.

B = 2∆f +1/Tb

Minimum band width =∆f +1/Tb

For the situation illustrated in Fig. 2.5, this would be 3. Or we can use

Carson’s rule B =( 2∆f +f m )In this case we have to realize that if our bits

are flipping back and forth between –1 and 1, then has a period of2Tb ,

corresponding to a frequency of f m =1/2TbPutting this into Carson’s rule

gives (2.9)So, we see that our BER is given by (2.6) and our bandwidth by

(2.9). Since the BER doesn’t (apparently) depend on B, why not let ∆f →

0so that we only need to use a bandwidth 1/Tb? Clearly something must be

in our way, because ∆f= 0 would mean that there would be no modulation

and hence no information being sent

Figure 2.5: Power spectrum of the FSK signal shown in Fig 2.1

. Power in dB vs. frequency

………………………………….. ( 2.9 )

Reference No. ( 2,3 )

13

Chapter 3

3.1 Procedure and the practical results

To design and implement our control unit we have to keep in our mind that

we must generate suitable digital code then we pass this code to RF unit to

be exchange from digital code to analog modulated signal(FSK) and in the

receiver we must do the reverse step back to back.

3.2 The problems that we have face it

1_ The first problem that we don’t find the component that give FSK signal

such as IC (TDA5100,SX1210).

2_ The second and main the problem is the synchronization between the

Tx& Rx when compare the code.

3.3 The solution that we use it

1_ we overcome this problem through using µ-c(ATmega16) that gives

high flexibly and solve the problem.

2_ we use codes that the same of Nec code that we would explain it later,

and we do our job by two stages .The first stage we designed IR system to

check and verify the efficiency of our system to deal with this codes also,

we used IR because we had IR component that work with high efficiency

such as(IR LED &PNA4602).The second stage we removed the IR unit

and connected the RF unit to reach to final form of our system shown in

fig(3.1&3.2) below.

14

S4

S1

S2

S3 VCO

AMP C _µ

S5

BPF

Envelop

COMP

o/p

o/p

8

LNA

ANT

BPF

f2

Envelop

C _µ

The transmitter

The Receiver

Figure.3.1: The Transmitter of the system

Figure.3.2: The Receiver of the system

15

3.4 First stage IR unit

3.4.1 The Transmitter

3.4.1.1 Microcontroller

Overview The ATmega16 is a low-power CMOS 8-bit microcontroller based on the

AVR enhanced RISC architecture. By executing powerful instructions in a

single clock cycle, the ATmega16 achieves throughputs approaching 1

MIPS per MHz allowing a system designer to optimize power consumption

versus processing speed.

2.2k Ώ

Our code

38

KH Z

20

0 Ώ

Ω 000

5V

2.2µF

C945

Figure.3.3: The Transmitter of IR Unit

-cµ

16

The AVR core combines a rich instruction set with 32 general

purpose working registers. All the32 registers are directly connected to the

Arithmetic Logic Unit (ALU), allowing two independent registers to be

accessed in one single instruction executed in one clock cycle. The

resulting architecture is more code efficient while achieving throughputs

up to ten times faster than conventional CISC microcontrollers. The

ATmega16 provides the following features: 16K bytes of In-System

Programmable Flash Program memory with Read-While-Write

Figure.3.4:Block Diagram OF µ-C

Reference No. ( 6 )

Block Diagram

17

capabilities, 512 bytes EEPROM, 1K byte SRAM, 32 general purpose I/O

lines, 32 general purpose working registers, a JTAG interface for Boundary

scan On-chip Debugging support and programming, three flexible

Timer/Counters with compare modes, Internal and External Interrupts, a

serial programmable USART, a byte oriented Two-wire Serial Interface,

an 8-channel, 10-bit ADC with optional differential input stage with

programmable gain (TQFP package only), a programmable Watchdog

Timer with Internal Oscillator, an SPI serial port, and six software

selectable power saving modes. The Idle mode stops the CPU while

allowing the USART, Two-wire interface, A/D Converter, SRAM,

Timer/Counters, SPI port, and interrupt system to continue functioning.

The Power-down mode saves the register contents but freezes the

Oscillator, disabling all other chip functions until the next External

Interrupt or Hardware Reset. In Power-save mode, the Asynchronous

Timer continues to run ,allowing the user to maintain a timer base while

the rest of the device is sleeping. The ADC Noise Reduction mode stops

the CPU and all I/O modules except Asynchronous Timer and ADC, to

minimize switching noise during ADC conversions. In Standby mode, the

crystal/resonator Oscillator is running while the rest of the device is

sleeping. This allows very fast start-up combined with low-power

consumption. In Extended Standby mode, both the main Oscillator and the

Asynchronous Timer continue to run. The device is manufactured using

Atmel’s high density nonvolatile memory technology. The On chip ISP

Flash allows the program memory to be reprogrammed in-system through

an SPI serial interface, by a conventional nonvolatile memory programmer,

or by an On-chip Boot program running on the AVR core. The boot

program can use any interface to download the application program in the

Application Flash memory. Software in the Boot Flash section will

continue to run while the Application Flash section is updated, providing

true Read-While-Write operation. By combining an 8-bit RISC CPU with

In-System Self-Programmable Flash on a monolithic chip ,the Atmel

ATmega16 is a powerful microcontroller that provides a highly-flexible

and cost-effective solution to many embedded control applications The

ATmega16 AVR is supported with a full suite of program and system

development tools including: C compilers, macro assemblers, program

debugger/simulators, in-circuit emulators and evaluation kits

,

. Reference No. ( 6 )

18

The infrared LED emitter is a high power (150 mW) infrared LED that is

commonly used in a wide variety of remote control and communications

projects. It's wide 60 degree beam width and high output power make it a

great infrared transmitter. Combined with the PNA4602M IR receiver and

we have the makings for a solid IR communications or control link

Specifications :

Peak Wavelength 940 nm

Spectral Bandwidth 45 nm

Half Angle Beam Width +/- 30 degrees (60 degrees total)

Package T1-3/4 (5mm)

Max Current: 100 mA

Breakdown Voltage 5V

Forward Voltage 1.4V-1.5V

Power Dissipation 150 mW

Figure.3.5: IR LED

Figure.3.6:a- IR LED Transmitter

b-PNA4602MIR receiver

a

b

b

Reference No. ( 6 )

3.4.1.2 IR LED

19

3.4.1.3 Mode of operation

We have five switch in our Tx circuit as shown in fig.3.3 the switches

(1,2,3,4) control the first four devices and the 5th switch is work as shift

that if it pressed the switches (1,2,3,4) will control the second of our 8

devices all that doing through the controller. We work Tx program that

make the µ-c generate two digital signal the first from timer two

pin21(OC2) and it 38KHZ ,the second from timer one pin19(OC1A) and it

represent our code (Nec code) through AND gate(transistor & IR LED) as

shown in fig.(3.3) so the o/p will be pass as OOK.

3.4.2Neccode

We aimed to use Nec code because that is widely used in the remote control

of many devices such as ( TV,DVB&CD player).

NEC TRANSMISSION FORMAT (frame waveform)

The NEC transmission format consists of the transmission of a leader code,

16-bit custom codes (Custom Code, Custom Code’), and 16-bit data codes

(Data Code, Data Code) at one time, as shown in Figure 3.7

Also refer to FRAME WAVEFORM. Data Code is the inverted code of

Data Code. The leader code consists of a 9-ms carrier waveform and a 4.5-

ms OFF waveform and is used as leader for the ensuing code to facilitate

reception detection. Codes use the PPM (Pulse Position Modulation)

method, and the signals “1” and “0” are fixed by the interval between

pulses.

20

(1) Magnification of stage 1

(2) Magnification of waveform 3

Figure.3.7: REM Output Code

Reference No. ( 6 )

FRAME WAVEFORM

21

Figure.3.8: Remote control use Nec code

From fig.3.7 we can see that the time of logic 1 = 2.25 ms and the time of

logic 0 = 1.125 ms, so we can calculate the maximum bit rate:

bit rate = 1

Tb

=1

1.125 = 889 bit/sec and it is equal to the bandwidth that the line coding is

return to zero, so the efficiency is equal to one

………………………………….. (3.1)

Reference No. ( 1 )

22

Configuration setting

Active port (D,B) ,set PortD( PD7,PD5) as o/p ,set PortB

(PB0,PB1,PB2,PB3,PB4) as i/p , set Timer2(CLK_IO/1,CTC Mode ,Toggle OC2

ON Compare Match ) , set OCR2=104

portB

updated

!(PINB)

Variables and Function

Send key ()

, customercode , PINB , headerdatacode

!(PB4)

!(PB1)

Datacode=

Send key(0)

Datacode=

Send key(1)

Datacode=

Send key(2)

!(PB0)

!(PB2)

Datacode=S

end key(3)

Datacode=

Send key(4)

Datacode=

Send key(5)

Datacode=

Send key(6)

Datacode=

Send key(7)

!(PB1)

!(PB0)

!(PB2)

1

2

Y

Y

N Y

Y

Y

N

N Y

N N

Y N Y

N

N

Tx Flow Chart

23

1>

0

Send header

Send customer code

Send data code

1

Y

24

Program text of Tx

/*--------------------- FSK Remote Control Transmitter --------------------*/

/*------------AVR used: ATMEGA16 (8 MHz Internal oscillator)---------*/

/*-----------------------Compiler: AVR-GCC (WinAVR 2010)-------------*/

/*-------------------------- I N C L U D E S ------------------------------------*/

#include <avr/io.h>

#include <util/delay.h>

#include "keys.h"

/*------------------------- D I F I N I T I O N S --------------------------------*/

#define SetIR() PORTD|=(1<<PD5)

#define ClrIR() PORTD&=~(1<<PD5)

/*------------------------- V A R I A B L E S -----------------------------------*/

voidSendKey(unsigned char Key);

/*------------------------------- M A I N -----------------------------------------*/

int main( void)

/* Set PD.7 , PD.5 as output.*/

DDRD = (1<<PD7) | (1<<PD5);

PORTB= (1<<PB4) |(1<<PB3) |(1<<PB2) |(1<<PB1) |(1<<PB0);

/* Set Timer2 (CLK_io/1 , CTC mode ,Toggle OC2 on compare

match).*/

TCCR2=(1<<WGM21)|(1<<COM20)|(0<<CS22)|(0<<CS21)|(1<<CS20)

;//xxxxx001

OCR2 = 104;

while( 1)

if(!(PINB &(1<<PB0)))//key0 pressed

if(!(PINB &(1<<PB4)))//key0 pressed

SendKey(_4);

else

SendKey(_0);

if(!(PINB &(1<<PB1)))//key1 pressed

if(!(PINB &(1<<PB4)))//key0 pressed

SendKey(_5);

else

25

SendKey(_1);

if(!(PINB &(1<<PB2)))//key2 pressed

if(!(PINB &(1<<PB4)))//key0 pressed

SendKey(_6);

else

SendKey(_2);

if(!(PINB &(1<<PB3)))//key3 pressed

if(!(PINB &(1<<PB4)))//key0 pressed

SendKey(_7);

else

SendKey(_3);

return 0;

// main

/*-------------------------- S E N D K E Y --------------------------------------*/

Void SendKey(unsigned char data)

Unsigned int Code =(data<<8) | (data^0xFF);

Unsigned int CostumCode =0x00FF;

unsigned char i;

/*Send Header*/

SetIR();

_delay_us(9000);

ClrIR();

_delay_us(4500);

/*Send Costum code ' Costum code */

for(i=0;i<16;i++)

SetIR();

_delay_us(560);

ClrIR();

if (CostumCode& (1<<(15-i)))

_delay_us(1690);// send "1"

else

_delay_us(565); // Send "0"

26

/* Send Data code , ~Costum code */

for(i=0;i<16;i++)

SetIR();

_delay_us(560);

ClrIR();

if (Code & (1<<(15-i)))

_delay_us(1690);// send "1"

else

_delay_us(565); // Send "0"

/*Send Stop bit*/

SetIR();

_delay_us(560);

ClrIR();

27

3.4.3.1 IR Detector

The PNA4602M is primary use to decode infrared signals modulated at 38

KHz, a frequency used by most remote controls. This unit, like others of it

type, are largely replacing the 'metal can' style of IR

receiver/demodulators. This new generation of device is smaller, less

expensive, and has better performance. Typical detection range is 5m

O/P

O/P O/P O/P O/P O/P O/P

O/P

VCC

100Ω

100Ω

100Ω

100Ω

100Ω

100Ω

100Ω

100Ω

2.2µF

000Ω

µ-c

Figure.3.9:The Receiver of IR Unit

Figure.3.10:IR Detector(PNA 4602M)

3.4.3 The Receiver

28

(straight ahead) and 3m (30 deg. either-side of centre). The PNA4602M

contains all the circuitry needed to decode IR remote signals used by most

consumer electronics devices (stereos, TVs, VCRs etc.).

Features

• Extension distance is 8 m or more

• External parts not required

• Adoption of visible light cutoff resin

The IR Detector will recover the base band signal(digital code),so it feed

to the µ-c and through a program the µ-c decide who device was meaned

by this code in o/p

Note: The IR Detector invert the base band signal ,so we had to process

this problem through our RX program.

c b

a

Figure.3.11:a-Block Diagram of IR Detector(PN4602)

b-BPF frequency characteristics-Directivity characteristics

29

y

y

y

Bit count+1 , IR<<=1 , IR|=1

Bit

count>=

33

1

1

Rx Flow chart Configuration setting

Active timrt1, set timer1 CLK at 64, set

timskat TICIE1

Old ICR1=new ICR1

New ICR1=ICR1, Cycle count=new ICR1-old

ICR1

Bit count=0

Variable sign function

Key code[] ,old ICR1, new ICR1, cycle

count, temp ,Bit count, data code,ICR1, IR

Bit

count=0

Cycle

count<1

800&>16

20

Bit count+1

Cycle

count<150

&>140

Cycle

count<300

&>280

Bit count+1, IR<<=1

y

N

y

N

N

N

N

2

30

Bit count=0

˜Data cod=˜((IR & 0xffff) & 0xff) , Data cod = ( IR & 0xffff) >>8 ,

Costumer cod =˜(( IR >>16)& 0xff) , costumer cod =(IR>>16)>>8˜

Data code=

˜Data cod

y

Temp=0

Data code=

Key

code[temp]

Temp+1

Temp>=

8

portB^=(1<<t

emp) , break

2

N

N

y N

y

31

/*--------------- IR remote control receiver (NEC format):------------------*/

/*-------------AVR used: ATMEGA16 (8 MHz Internal oscillator)-------*/

/*----------------Compiler: AVR-GCC (WinAVR 2010)--------------------*/

/*--------------------------------- I N C L U D E S -----------------------------*/

#include <avr/io.h>

#include <avr/interrupt.h>

#include "keys.h"

/*-------------------------------- V A R I A B L E S ---------------------------*/

unsigned char

BitCount,DataCode,CustomCode,_DataCode,_CustomCode;

unsigned long IR=0;//received 32-bit command( custom code , custom

code' , Data Code , Data Code' )

unsigned int oldICR1,newICR1,CycleCount;

unsigned char temp;

unsigned char KeyCodes[]=_0,_1,_2,_3,_4,_5,_6,_7,_8,_9;

/*------------------------------ D I F I N I T I O N S ---------------------------*/

ISR (SIG_INPUT_CAPTURE1)

oldICR1 = newICR1 ;

newICR1 = ICR1;

CycleCount=newICR1-oldICR1;

if(BitCount==0)

Rx program text

32

If((CycleCount<1800) && (CycleCount>1620)) // Header detected

(1687.5 cycles)

BitCount+=1;

if((BitCount>0) && (CycleCount<150) && (CycleCount>140))// logical

"0" detected

BitCount+=1;

IR<<=1;

if((BitCount>0) && (CycleCount<300) && (CycleCount>280))// logical

"1" detected

BitCount+=1;

IR<<=1;

IR|=1;

if(BitCount ==33)

BitCount=0;

DataCode = ~((IR & 0xFFFF) & 0xFF);//must equal to DataCode

DataCode = (IR & 0xFFFF)>>8;

_CustomCode = ~((IR >> 16) & 0xFF);//must equal to CustomCode

33

CustomCode = (IR >> 16)>>8;

if(DataCode== _DataCode)

for(temp=0;temp<8;temp++)

if(DataCode == KeyCodes[temp])

//a key between 0 and 7 was pressed so toggle that bit

PORTB^=(1<<temp);

break;

void intIR(void)

TCCR1B=(1<<CS11)|(1<<CS10); // clk/64

TIMSK=(1<<TICIE1);

sei();

34

3.5 second stage RF Unit

Here we must remove the IR Unit and pass the digital code to the RF Unit

as shown in figure below

VCO AMP

Figure.3.12: circuit of Tx& RX for our project

Digital

code FSK

Figure.3.13: RF Unit (Tx)

35

3.5.1 Voltage Control Oscillator(VCO)

We used Varctor Tuned Oscillator that give 27 MHZ frequency and we

used varctor diode from type( SVC224) and it has 80 pf with no reverse

voltage apply on it

The input digital code has 5VP-P,so when it apply on the varctor diode will

change the reverse bias capacitor of the diode, so the VCO frequency will

change according to that

Calculation of the VCO:

Vb=VCC*R2 / (R2 + R3 )

= 2.17 v

Ve = vb – 0.7 = 1.47 v

Q1

2N2222A

R110k

R2470k

R3150k

R41k

R51k C1

0.1uF

C20.01uF

C3

1uF

C4

1uF

L12mH

L20.43uH

D1BB112

VCC

9V

R6

198k i/p digital code

digital code

RFC

Figure.3.14:vco circuit

………………………………….. (3.2)

o/p fsk

digital code

Reference No. ( 5 )

36

Ie = ve / R5 = 1.47 mA

Re = 26 mv / Ie

= 27 Ω

Av = RL / (RE + re )

≈ 10

The oscillator must satisfy Barkhausen criterion

Av ≥ B

B= C2 / C1

= 10

fo = 1 / ( 2π√(L Ct ) )

Ct = C1//C2//Cv Cv<< C1 &C2 So Ct ≈ Cv

fo = 27 MHz with no reverse voltage applied

From equation (3.6 ) we got L2=0.43µH

Our coil (L2) to satisfy( 0.43µH) it must designed under the formula

L=µN2A/l where µ is the permeability of the core(4π10-7 for free space),

N number of turns of coil , A cross section area of coil, l length of the coil.

We choose copper wire gauge 24 (0.0201 inch diameter ) and the coil

radius =5mm so the N=8 and l=1.5 cm

To reduce the frequency deviation (Δf) we must reduce the voltage that

applied on varector diode to be from 5v to 26.3 my ( R6& R4 ) that give

Δf = 500 kHz , so less band width required

Cv= Co/ √(1- 2V)

Co = 80 pf

Cv=78 pf , So f1 = 27.5 MHz

From eq. (2.9)

………………………………….. (3.3)

………………………………….. (3.4)

………………………………….. (3.5)

………………………………….. (3.6)

………………………………….. (3.7)

Reference No. ( 5 )

Reference No. ( 5 )

Reference No. ( 5 )

Reference No. ( 5 )

Reference No. ( 5 )

37

Bw =Δf + 1/Tb = 0.50088 MHz ≈ .5 MHz

3.5.2 Power Amplifier(PAMP)

We used class C PAMP because it usually used in high frequency and

provide a good efficiency about (100%) and it has frequency selector

circuit

=RC > t in , t in=ז1

27∗106 = 37 n sec

let80 =ז nsec = RC , C1 = 80 pf

R1 = 1 kΩ

fo = 27.25 MHz

fo = 1 / ( 2π√ (L C )) , let L =0.43 µH

C2 = 79.4 pf≈ 80 pf

Bw = .5 MHz , so Quality factor (Q) = fo /Bw =50.5

Q= R/(wL) =3.7 kΩ = R2

C1

80pF

R1

1k

Q1

BF517

L1

0.43uH

C2

80pF

VCC

5V

R2

3.7k

C3

1uF

Figure.3.15 class C PAMP

………………………………….. (3.8)

o/p

digital code i/p

digital code

Reference No. ( 5 )

38

3.5.3 Antenna

We used antenna of type Rubber Ducky antenna(helical antenna normal

mode ) and it consist of a conducting wire wound in the form of a helix . It

is primarily designed to replace very large antennas. Their reduced size is

therefore most suitable for Mobile and Portable High-frequency (HF)

communications in the 1 MHz to 30 MHz operating range.

where R is resistance in ohms, C is the circumference of the helix, and λ is

the wavelength and N is the number of turns and S is the spacing between

turns .

portable radios use Rubber Ducky antennaFigure.3.16 :

………………………………….. (3.9)

………………………………….. (3.10)

………………………………….. (3.11)

………………………………….. (3.12)

Reference No. ( 7 )

Reference No. ( 7 )

39

Our antenna has 20 turns ,2.5mm radius , 1mm space ,f= 27.5MHz,

λ =11m So from above equations R=158Ω ,

3.5.4 Band Pass Filters & Envelop Detectors

At the receiver we used antenna & PAMP the same that used in transmitter

then the signal is passed to two band pass filters & envelop detectors as

shown in figure(3.2) to recover the base band signal (digital code) that the

band pass select the specified frequency and the envelop detector

discriminate the signal to change it to amplitude signal .

The value of ( C , L , R ) can calculated from the formula below .

fo = 1 / ( 2π√ (L C ) for (L1,C1 )

RC = 1 / ( 2π√ (fc fm ))for C2,R2 = ז

where fm = 888Hz

So for the band pass filters & envelop detectors 1st f1 = 27.5 MHz let

L1=0.43μH then C1=78pf & C2=1nf, R1&R2=1kΩ

For 2ndband pass filters &envelop detectors fo= 27 MHz C1=80pf ,

C2= 1nf , L1= 0.43pf , R1&R2=1kΩ

R11k

C180pF

L10.43uH

D1

1BH62 R21k

C280pF

Figure.3.17:band pass filters & envelop detectors

………………………………….. (3.13)

i/p

digital code

o/p

digital code

Reference No. ( 5 )

40

Then we can use comparter( Lm1458 ) then the recovered signal feed to

the µ-C and the RF unit would be finished ..

Chapter 4

Conclusions

We can summery the conclusions that we got from our project that we can

separate the controlling of the devices by use deferent code for each device

and the header provide synchronization and security also we found that

when the code has some shift , would not cause any problem at the decision

because all the parts of the code would have the same shift .

References

1. Jack K. , An Introduction to Digital Communications ,library of Congress Cataloging

in publication Data 1999, pp 270_283 .

2. Anderson, J. B., Digital Transmission Engineering, IEEE Press, 1999, ISBN 0-13-

082961-7.

3. Burr, A., Modulation and Coding for Wireless Communications, Prentice Hall, 2001,

ISBN 0-201-39857-5.

4. Charles D. Knutson with Jeffrey M. Brown, IrDA Principles and Protocols, 2004,

ISBN 0-9753892-0-3 _ Retrieved from

"http://en.wikipedia.org/wiki/Infrared_Data_Association

5. Roy B. ,Basic Electronic Communication ,Ch2 _pp 59_65 ,80_93 ,by West

Publishing company 1993.

6. ATMEGA16 datasheet _ Retrieved from _ http://www.atmel.com/doc2466.pdf

7. Balanis , Antenna Theory Analysis and Design ,3rd Edition _ helical antenna_ pp

255_267 _Retrieved from _ http://www.arab-eng.org/vb/t234948.html