Bachelorthesis.compressed

Biomedical Wireless Sensor Network
DDU (Faculty of Tech., Dept. of IT) Page 1
BE-Sem- VIII
Prepared at
Prepared by
Shah Dhara M. ID No. 056079
Viroja Pooja S. ID No. 051118
Shah Ishan D. ID No. 13821
Guided By
Prof. Dr. Prabhat Ranjan Prof. R.S.Chhajed
Dept. of Wireless Communication Head of Dept. of Information
Technology Technology
DA-IICT, Gandhinagar DDU, Nadiad
Department of Information Technology
Faculty of Technology, Dharamsinh Desai University
College Road, Nadiad-387001
March-April 2009

TABLE OF CONTENTS
Title Page No
ABSTRACT…………………………………………………………………..5
1.0 Introduction…………………………………………………….............8
1.1 Project Details
1.2 Purpose
1.3 Scope
1.4 Objective
1.5 Technology and Literature Review
1.5.1 ECG Signal
1.5.2 Electrodes
1.5.3 Amplifiers and Filters
1.5.4 QRS Detector
1.5.5 STK_500 Kit
1.5.6 Microcontroller IC-ATMEGA32
1.5.7 XBee
2.0 Project Management………………………………………………….54
2.1 Feasibility Study
2.1.1 Technical feasibility
2.1.2 Time schedule feasibility
2.1.3 Operational feasibility
2.1.4 Implementation feasibility
2.2 Project Planning
2.2.1 Project Development Approach and justification
2.2.2 Project Plan
2.2.3 Milestones and Deliverables
2.2.4 Roles and Responsibilities
2.2.5 Group Dependencies
2.3 Project Scheduling
Project scheduling chart
3.0 System Requirements Study………………………………………….57
3.1 History of ECG
3.2 Study of Current System
3.3 Problems and Weaknesses of Current System
3.4 System User Characteristics

3.5 Hardware and Software requirements
3.6 Constraints
3.6.1 Regulatory Policies
3.6.2 Hardware Limitations
3.6.3 Interfaces to Other Applications
3.6.4 Parallel Operations
3.6.5 Higher Order Language Requirements
3.6.6 Reliability Requirements
3.6.7 Criticality of the Application
3.6.8 Safety and Security Consideration
3.7 Assumptions and Dependencies
4.0 System Analysis………………………………………………………..62
4.1 Requirements of New System (SRS)
4.1.1 User Requirements
4.1.2 System Requirements
4.2 Features of New System
4.3 Navigation Chart
4.4 Class Diagram (Analysis level, without considering impl. environment)
4.5 System Activity(Use case and/or scenario diagram)
4.6 Sequence Diagram (Analysis level, without considering impl.
Environment)
4.7 Data Modeling
4.7.1 Data Dictionary
4.7.2 ER Diagram
5.0 System Architecture Design………………………………………….65
5.1 Pre-Amplifier Circuit
5.2 Post-Amplifier Circuit
5.3 QRS Detector Circuit
5.4 Controller Circuit
5.5 Hardware Module
6.0 Implementation Planning…………………………………………….74
6.1 Implementation Environment
6.2 Program Specification
6.3 Coding Standards

7.0 Testing…………………………………………………………………83
7.1 Testing Plan
7.2 Testing Strategy
7.3 Testing Methods
7.4 Test Cases
7.4.1 Purpose
7.4.2 Required Input
7.4.3 Expected Results
8.0 Limitation and Future Enhancements……………………………..84
9.0 Conclusion and Discussion …………………………………………86
9.1 Conclusions and Future Enhancement
9.2 Discussion
9.2.1 Self Analysis of Project Viabilities
9.2.2 Problem Encountered and Possible Solutions
9.2.3 Summary of Project work
EXPERIENCE…………………………………………………………….87
REFERENCES……………………………………………………………89

Abstract
The object of our project is acquisition of Electro cardiogram signal from
patient‟s body through wearable system, analyze whether it is normal or
abnormal at patient‟s end, then transmit the wireless signal if found that it is
abnormal. Transmission is to be done wirelessly through XBEE Technology
and then higher level analysis is to be done on computer which is situated at
base -station. To achieve our objective we have used microcontroller AT Mega
32 and for its programming we have used dynamic C with AVR Studio base.
For higher level analysis we have made software using Java J2EE, Java Script
and PHP.

Chapter 1 INTRODUCTION
1.1 PROJECT DETAILS
This document aims to define the overall hardware and software requirements for “Biomedical
Wireless Sensor Network” project. Efforts were exhaustively accurate to fulfill the requirements.
The final system will be having only features mentioned in this document and assumptions for any
additional functionality should not be made by any of the parties’ moves in developing this system.
This system will be working to take an ECG Signal from the patient and analysis it. If any abnormality
is present, transmit it and inform the Doctor through wireless device.
1.2 PURPOSE
This specification document describes the capabilities that will be provided by the hardware as well
as software application. It also states the various required constraints by which the system will
abide. The intended evidence for this document is the Development Team, Testing Team and users
of this document.
This system is designed basically for old age people. We know that in Old Age Home people move
freely in the surrounding area and for their heart care, we make wearable ECG monitor which is rang
a buzzer if any abnormality happened with patient heart and send this abnormal signal to the Doctor
through wireless then corresponding, immediately Doctor service can be provided.
1.3 SCOPE
According to project aim the heart patient can consult Doctor if any abnormal thing happened with
his or her heart. And for that this wearable ECG monitor is helpful. Like for Old Age Home people,
they wear it and move freely in campus. Another scope is that we can use it in hospitals for heart
patients and in resident society, mall, office building. The coverage area can change according the
range of the wireless device.

1.4 OBJECTIVE
Estimation was made that about 17.5 million people were died from cardiovascular disease in 2005,
representing 30 % of all global deaths. Out of these deaths, 7.6 million were due to heart attacks and
5.7 million were due to stroke. If current trends are allowed to continue, by 2015 an estimated 20
million people will die from cardiovascular disease, mainly from heart attacks and strokes.
Unfortunately, out of these heart attacks, 250,000 are sudden, causing the patient to die within an
hour. And it is estimated that about 47% of cardiac deaths occur before emergency services or
transport to a hospital.
This wearable ECG sensor can provide emergency services and may reduce the death rate, occur
before emergency services.
1.5 TECNOLOGY AND LITERATURE REVIEW
1.5.1 ECG Signal
 Blood Circulation Through Heart
The heart is one of the most important organs in the entire human body. It is really nothing
more than a pump, composed of muscle which pumps blood throughout the body, beating
approximately 72 times per minute of our lives.

Figure 1.1 Anatomy of the Heart Figure 1.2 Blood circulation in the Heart
Figure 5.1.2 shows the circulation of blood through the heart. The blood enters the right
atrium of the heart through the superior vena cava. The right atrium contracts and pushes the
blood cells through the tricuspid valve into the right ventricle. The right ventricle then
contracts and pushes the blood through the pulmonary valve into the pulmonary artery, which
brings it to the lungs. In the lungs, the blood cells exchange carbon dioxide for oxygen. This
oxygenated blood returns to the heart by way of the pulmonary vein and enters the left
atrium. The left atrium contracts and pumps the blood through the mitral valve into the left
ventricle. Then, the left ventricle contracts and pushes the blood into the aorta. The aorta
branches off into several different arteries that pump the oxygenated blood to various parts of
the body. So the flow is…
Anterior and posterior vena cava -> right atrium -> tricuspid valve -> right ventricle ->
pulmonary semi lunar valve -> pulmonary artery -> lungs -> pulmonary veins -> left atrium -
> bicuspid valve -> left ventricle -> aortic semi lunar valve -> aorta -> arteries -> body.

Heart is having its own source of oxygenated blood. The heart is supplied by its own set of
blood vessels. These are the coronary arteries. There are two main ones with two major
branches each. They arise from the aorta right after it leaves the heart. The coronary arteries
eventually branch into capillary beds that course throughout the heart walls and supply the
heart muscle with oxygenated blood. The coronary veins return blood from the heart muscle,
but instead of emptying into another larger vein, they empty directly into the right atrium.
 Electrical Activity Of The Heart
The heart has a natural pacemaker that regulates the pace or rate of the heart. It sits in
the upper portion of the right atrium (RA) and is a collection of specializes electrical cells known as
the SINUS or SINO-ATRIAL (SA) node.
Figure 1.3 Sequence of electrical activity within the Heart
The sequence of electrical activity within the heart is displayed in the diagrams above and occurs as
follows:
As the SA node fires, each electrical impulse travels through the right and left atrium.
This electrical activity causes the two upper chambers of the heart to contract. This electrical activity
and can be recorded from the surface of the body as a "P" wave" on the patient's EKG or ECG
(electrocardiogram).
The electrical impulse then moves to an area known as the AV (atrium-ventricular) node.
This node sits just above the ventricles. Here, the electrical impulse is held up for a brief period. This
delay allows the right and left atrium to continue emptying its blood contents into the two
ventricles. This delay is recorded as a "PR interval." The AV node thus acts as a "relay station"
delaying stimulation of the ventricles long enough to allow the two atria to finish emptying.
Following the delay, the electrical impulse travels through both ventricles. The electrically
stimulated ventricles contract and blood is pumped into the pulmonary artery and aorta. This
electrical activity is recorded from the surface of the body as a "QRS complex". The ventricles then
recover from this electrical stimulation and generate an "ST segment" and T wave on the EKG.

In case of the heart, adrenaline plays the role to increase the number of impulses per
minute, which in turn increases the heart rate. The release of adrenaline is controlled by the nervous
system. The heart normally beats at around 72 times per minute and the sinus node speeds up
during exertion, emotional stress, fever, etc., or whenever our body needs an extra boost of blood
supply. In contrast, it and slows down during rest or under the influence of certain medications. Well
trained athletes also tend to have a slower heart beat.
Figure 1.4 Graphical Representation of ECG Signal
The different waves that comprise the ECG represent the sequence of depolarization and
repolarization of the atria and ventricles. The ECG is recorded at a speed of 25 mm/sec, and
the voltages are calibrated so that 1 mV = 10 mm in the vertical direction. Therefore, each
small 1-mm square represents 0.04 sec (40 msec) in time and 0.1 mV in voltage.
1.5.2 Electrodes
 Limbs Electrodes
There are different types of electrodes like Augmented Electrodes, Limbs Electrodes and Chest
Electrodes. In which limbs electrodes are mostly used. Bipolar recordings utilize standard limb lead
configurations depicted at the right. By convention, lead I have the positive electrode on the left

arm, and the negative electrode on the right arm, and therefore measure the potential difference
between the two arms. In this and the other two limb leads, an electrode on the right leg serves as a
reference electrode for recording purposes. In the lead II configuration, the positive electrode is on
the left leg and the negative electrode is on the right arm. Lead III has the positive electrode on the
left leg and the negative electrode on the left arm. Whether the limb leads are attached to the end
of the limb or at the origin of the limb makes no difference in the recording because the limb can
simply be viewed as a long wire conductor originating from a point on the trunk of the body.
Figure 1.5 Leads Configuration
Based upon universally accepted ECG rules, a wave a depolarization heading toward the left arm
gives a positive deflection in lead I because the positive electrode is on the left arm. Maximal
positive ECG deflection occurs in lead I when a wave of depolarization travels parallel to the axis
between the right and left arms. If a wave of depolarization heads away from the left arm, the
deflection is negative. Also by these rules, a wave of repolarization moving away from the left arm is
recorded as a positive deflection. Similar statements can be made for leads II and III in which the
positive electrode is located on the left leg. For example, a wave of depolarization traveling toward
the left leg produces a positive deflection in both leads II and III because the positive electrode for
both leads is on the left leg. A maximal positive deflection is recorded in lead II when the
depolarization wave travels parallel to the axis between the right arm and left leg. Similarly, a
maximal positive deflection is obtained in lead III when the depolarization wave travels parallel to
the axis between the left arm and left leg.

1.5.3 AMPLIFIER AND FILTERS
Low Pass Filter
Figure 1.9 – Implemented Low Pass Filter
Since the ECG signal is contained in the relatively narrow frequency spectrum below 100Hz, a low
pass filter can remove a large amount of ambient noise. With microprocessors and an RF transmitter
in close proximity to the analogue circuitry, the low pass filter is responsible for ensuring these do
not detrimentally affect the ECG obtained. The low pass filter implemented is shown in Figure above.
It is a first order active filter. The corner frequency is calculated to be 105Hz. An active filter was
used as it also provides gain. The gain of the filter is given by the ratio of R9 to R8; in this
implementation it is 13.6. Figure below shows the frequency response of the filter as generated by
PSPICE.

Figure 1.10 – Frequency Response of Low Pass Filter
A first order filter was deemed to be adequate since little noise is contained in the frequency band
immediately above 100Hz and the 20dB/decade attenuation roll-off is effective in removing the
microprocessor and RF circuitry noise contained in the megahertz.

50Hz Notch Filter
Figure 1.11 – Implemented Notch Filter
Mains power noise is the biggest problem for normal ECG measurement, and especially so in this
system due to the unsuitability of right leg driver circuitry. In order to combat this, a notch filter is
implemented. Numerous filter topologies were tried in PSPICE such as the Fliege and Sallen-Key,
before it was decided that the Twin T provided the best result. The implemented filter is shown in
Figure above, with the frequency response to a 1V AC signal shown in Figure below.

Figure 1.12 – PSPICE Simulation of Notch Filter Response

Difficulties arise in the physical construction of the filter due to the large tolerances of capacitors.
The depth of the notch depends greatly on accurate components and much effort is required to
identify capacitors which give good attenuation at the correct frequency. In the final product,
capacitors C7, C8 and C9 are implemented as a couple of capacitors in parallel after having been
tested and proven to work together to give a good result. The rejection quality could be easily
improved by decreasing R3, but is not easy to implement because a narrower filtering bandwidth
requires more accurate components determining the bandwidth.
Summing Amplifier
Figure 1.12 – Implemented Summing Amplifier
After filtering and amplification, the data is ready to be digitised by the ADC. The ADC requires the
signal it is sampling to be contained completely in the positive voltage domain. The summing
amplifier is used to achieve this and its topology is shown in Figure above. The DC voltage that the

signal will be added to is supplied by the voltage divider formed with two 2.2kΩ resistors. The other
resistors set the gain of the amplifier to be one, and are much larger than the resistors in the voltage
divider so they don't influence the voltage division. In this way the output of the summing amplifier
is the ECG signal transposed up by 2.5V.
Instrumentation Amplifier
An instrumentation amplifier is a type of differential amplifier that has been outfitted with input
buffers, which eliminate the need for input impedance matching and thus make the amplifier
particularly suitable for use in measurement and test equipment. Additional characteristics include
very low DC offset, low drift, low noise, very high open-loop gain, very high common-mode rejection
ratio, and very high input impedances. They are used where great accuracy and stability of the
circuit both short- and long-term are required. The Analogue Devices LM324 was chosen for
implementation in the system. These devices consist of four independent high-gain frequency-
compensated operational amplifiers that are designed specifically to operate from a single supply
over a wide range of voltages.
 Design and Construction
The circuitry for capturing ECG signals was built in our laboratory using traditional components and
techniques. Fig.3 shows the actual breadboard circuit. The following sections elaborate on the
details of the design and circuitry layout of each stage or component.

Fig. 1.13 Signal Acquisition Board - Developed In-lab
The ECG signals were amplified by the instrumentation amplifier and fed into the noise filtering
circuits in different stages. To get required output we split Instrumentation amplifier in two parts,
one of them is Pre-amplifier and second one is Post-amplifier. They include simple amplifier, notch
filter and buffer amplifier.
 Pre-amplifier and Post-amplifier
A voltage buffer amplifier is used to transfer a voltage from a first circuit, having a low
output impedance level, to a second circuit with a high input impedance level. The interposed
buffer amplifier prevents the second circuit from loading the first circuit unacceptably and
interfering with its desired operation. In the ideal voltage buffer, the input resistance is
infinite, the output resistance zero.

Notch filters used for eliminating 50Hz noise signal. It is must for clear appearance. The
object is to get the signal between the lower and upper cutoff frequencies (f1 and f2,
respectively). This will cause the signal to be reduced by at least 3 decibels, or effectively
half the power of the desired signal.
Butterworth filter has a more linear phase response. And its frequency response is
maximally flat (has no ripples) in the pass band, and rolls off towards zero in the stop band. It
has a monotonically changing magnitude function with ω. The Butterworth is the only filter
that maintains this same shape for higher orders compared with other filters, the Butterworth
filter has a slower roll-off, and thus will require a higher order to implement a particular stop
band specification. Here we are using 3rd
order Butterworth filter.
Figure 1.14– QRS Detector
1.5.4 QRS DETECTOR

The QRS complex represents ventricular depolarization. The duration of the QRS complex is normally
0.06 to 0.1 seconds. It has high amplitude among one heart signal. So, using R wave detector
detection and analysis become easy to decided coming signal is normal or abnormal. Fig.3 shows the
actual breadboard circuit. The following sections elaborate on the details of the design and circuitry
layout of each stage or component.

Figure 1.16 QRS Detector circuit on bread board
 Design and Construction
The output of ECG amplifier is given as an input to the QRS Detector circuit. The first stage of it is
notch filter of 50 Hz. It has same functionality as describe in filter section.

Primary Results
Figure QRS Detector Output

Figure Test point 4 output

Figure 1st
ECG Signal

Figure work place circuit implementation

Figure Work place part 2

Circuit

Then filter is come. It is sometimes convenient to design a simple active high pass filter using
transistors. Using transistors, this filter is convenient to place in a larger circuit because it contains
few components and does not occupy too much space. The active high pass transistor circuit is quite
straightforward, using just a total of three resistors, three capacitors and two transistors. The
operating conditions for the transistor are set up in the normal way. The resistor Re is the emitter
resistor and sets the current for the transistor.
A rectifier is an electrical device that converts alternating current (AC) to direct current
(DC). Rectifiers may be made of opamp, diodes, resistors and capacitors. Here we are used
full wave rectifier. When only one diode is used to rectify AC (by blocking the negative or
positive portion of the waveform), the difference between the term diode and the term
rectifier is merely one of usage, Almost all rectifiers comprise a number of diodes in a
specific arrangement for more efficiently converting AC to DC than is possible with only one
diode.
For R wave detector, we use transistor and few passive components; you can build a fairly sensitive
peak detector circuit. You can find a peak signal although you only detect the peak of positive cycle.
Here we use pnp transistor as well as npn. The input stage is biased so that the supply voltage is
divided equally across the two complimentary output transistors which are slightly biased in
conduction by the diodes between the bases. The resistors are used in series with the emitters of
the output transistors to stabilize the bias current so it doesn't change much with temperature or
with different transistors and diodes. Here is the actual circuit’s schematic diagram is shown below.
1.5.5 STK_500 Kit
STK_500 Kit is designed to give designers a quick start to develop code on the AVR and for
prototyping and testing of new designs. Its features are given below
 AVR Studio Compatible
 RS-232 Interface to PC for Programming and Control
 Regulated Power Supply for 10 - 15V DC Power
 Sockets for 8-pin, 20-pin, 28-pin, and 40-pin AVR Devices
 Parallel and Serial High-voltage Programming of AVR Devices
 Serial In-System Programming (ISP) of AVR Devices
 In-System Programmer for Programming AVR Devices in External Target System
 Reprogramming of AVR Devices
 All AVR I/O Ports Easily Accessible through Pin Header Connectors
 8 Push Buttons , 8 LEDs and RS-232 Port are for General Use
 On-board 2-Mbit Data Flash for Nonvolatile Data Storage

Figure 5.1 STK_500 Kit Components
 Turn on the kit
First of all connect the power cable between a power supply and the STK_500 and
apply 10 - 15V DC to the power connector. The input circuit is a full bridge rectifier and the
STK_500 automatically handles both positive and negative center connectors. The red LED is lit
when power is on, and the status LEDs will go from red, via yellow, to green that indicates the
target VCC is present.
 Description
o LEDs and Switches:
The STK500 starter kit includes 8 yellow LEDs and 8 push-button switches. The
LEDs and switches are connected to debug headers that are separated from the rest of the Board.
The cables should be connected directly from the port header to the LED or switch header. Valid
target voltage range is 1.8V < VTG < 6.0V.

Figure 5.2 Ports of LEDs and Switches
Figure 5.3 Connection of LEDs and Switches on kit
o Description of Ports:
The pin out for the I/O port headers is explained in Figure where x is stand for
A, C, D. The supplied cables can be used if the Data Flash is connected to the hardware SPI
interface on PORTB of the AVR microcontroller. The connection of the I/O pins is shown in
Figure. The PORTE/AUX header has some special signals and functions in addition to the PORTE
pins.

Figure 5.4 Various types of Ports
o Jumper Setting:
A master microcontroller and the eight jumpers control the hardware settings of the
starter kit. During normal operation these jumpers should be mounted in the default position.
To configure the starter kit for advanced use, the jumpers can be removed or set to new
positions.
 Default Setting
 VTARGET : On-board VTARGET supply connected
 AREF : On-board Analog Voltage Reference connected
 RESET : On-board Reset System connected
 XTAL1 : On-board Clock System connected
 OSCSEL : On-board Oscillator selected
Jumper mounted on pins 1-2: On-board software clock signal connected (default).
Jumper mounted on pins 2-3: On-board crystal signal connected.
Jumper not mounted : On-board XTAL1 signal disconnected.
 BSEL2 : Uncounted. Used for High-voltage Programming of various types of AT mega
Chips
 PJUMP : Unmounted. Used for High-voltage Programming of AT90S2333,AT90S4433,
and ATmega8
 Work on the kit

Connect a serial cable to the connector marked RS232 CTRL on the evaluation board to a COM
port on the PC. When AVR Studio is started, the program will automatically detect to which COM
port the STK_500 is connected. The STK_500 is controlled from AVR Studio, version 3.2 and
higher. AVR Studio is an integrated development environment (IDE) for developing and
debugging AVR applications.AVR Studio provides a project management tool, source file editor,
simulator, in circuit emulator interface and programming interface for STK500.
To program a hex file into the target AVR device, select STK500 from the Tools menu in AVR
Studio. Select the AVR target device from the pull-down menu on the Program tab and locate
the Intel-hex file to download. Press the Erase button, followed by the Program button. The
status LED will now turn yellow while the part is programmed, and when programming succeeds,
the LED will turn green. If programming fails, the LED will turn red after programming.
o Program Settings
It is divided into four different subgroups and includes an erase button on the
selected device, erasing Flash and EEPROM memories. For devices only supporting High-voltage
Programming, the ISP option will be grayed out. If both modes are available, select a mode by
clicking on the correct method. Erase Device before Programming will force STK500 to perform
a chip erase before programming code to the program memory (Flash). Verify Device after
Programming will force STK500 to perform a verification of the memory after programming it
(both Flash and EEPROM) select the “Input HEX File” option.

Figure 5.5 Program Modes
o Board Settings:
VTAR controls the operating voltage for the target board. This voltage can be
regulated between 0 and 6.0V in 0.1V increments. AREF controls the analog reference voltage
for the ADC converter. This setting only applies to devices with AD converter. Both voltages are
read by pressing the “Read Voltages” button, and written by pressing the “Write Voltages”
button. The board uses a programmable oscillator circuit that offers a wide range of frequencies
for the target device.
Figure 5.6 Board Modes
o Auto Settings:
When programming multiple devices with the same code, the “Auto” tab offers a
powerful method of automatically going through a user-defined sequence of commands. They
are executed, if selected. To enable a command, the appropriate check box should be checked.

For example, if only “Program FLASH” is checked when the “Start” button is pressed, the Flash
memory will be programmed with the hex file specified in the “Program” settings.
Figure 5.7 Auto Modes

1.5.7 Xbee or Xbee-PRO
 Introduction
If you are looking for wireless monitoring and remote control solutions, XBee may be the
answer. Xbee nodes can tie up a home, office or factory building for nodes safety, security and
control.
The modules have high performance at a low-cost and low-power wireless sensor networks.
The modules require minimal power and provide reliable delivery of critical data between
devices. The modules operate within the ISM (Industrial Scientific Medical) 2.4 GHz frequency
band .RF Data Rate is 250kbps .They are pin-for-pin compatible with each other.
We can easily use them.
 Xbee RF Module
Communication range of it in Urban is up to 100 m and line-of-sight is up to 300 m with 100mW
power. Its TX current is 270mA, 3.3v and RX current is 55mA, 3.3v. And its receiver sensitivity is -
100dBm.
 Pin Configuration
XBee has 20 pins. Minimum connections are VCC, GND, DOUT and DIN. Unused pins should be
left disconnected. Signal. And direction is specified with respect to the module.
Figure 7.1 XBee or XBee-PRO

 Procedure
Data enters the XBee Module UART through the DI pin (pin 3) as an asynchronous serial signal.
The signal should idle high when no data is being transmitted. Each data byte consists of a start
bit (low), 8 data bits (LSB first) and a stop bit (high). The XBee UART performs tasks, such as
timing and parity checking, that are needed for data communications. Serial communication
consists of two UARTs configured with compatible settings (baud rate, parity, start bits, stop bits,
data bits). One illustration is given below
Figure 7.2 UART data packet 0x1F transmitted through the RF module
 Flow Control
When physical connection is established, at the transmitter site the data is transmitted
from microcontroller to XBee through buffer and vice versa procedure at the receiver.
Here we have to mention in software program that which connected XBee is worked as a
transmitter or as a receiver. The internal diagram and flow of communication is shown in
figure.
•DI Buffer, Hardware Flow Control (CTS).
•DO Buffer, Hardware Flow Control (RTS).

Figure 7.3 External and Internal flow of data
o DI Buffer may become full and possibly overflow:
If the module is receiving a continuous stream of RF data, any serial data
that arrives on the DI pin is placed in the DI Buffer. The data in the DI buffer will be
transmitted over-the-air when the module is no longer receiving RF data in the
network.
o DO Buffer may become full and possibly overflow:
1. If the RF data rate is set higher than the interface data rate of the module,
the module will receive data from the transmitting module faster than it can send the
data to the host.
2. If the host does not allow the module to transmit data out from the DO
buffer because of being held off by hardware or software flow control.
Solution
1. Send messages that are smaller than the DI buffer size.
2. Interface at a lower baud rate (BD parameter, p16) than the fixed RF data
rate.
 Modes

XBee is operated in five modes. It operates in one mode at a time.
 Serial data is received in the DI Buffer : Transitions to Transmit Mode
• Valid RF data is received through the antenna : Transitions to Receive Mode
• Sleep Mode condition is met : Transitions to Sleep Mode
• Command Mode Sequence is issued : Transitions to Command Mode
 Programming the RF module
In the Command Mode section entering Command Mode, sending AT commands and exiting
Command Mode.
Send AT Command: System Response
 +++ : Enter into command mode
 ATCH : Channel command
 ATMY : 16-bit source address
 ATDH : Read current Destination Address High
 ATDL : Read current Destination Address Low
 ATWR : Write to non-volatile memory
 ATGT : Guard Timer , prevent inadvertent entrance into AT command
mode
 ATRE : Restore Defaults
 ATSM : Sleep mode
 ATBD : Interface data rate , 9600bps is default value
 ATCN : Exit AT command mode

There are also many other AT Commands are presents, these are mostly using. All these
commands are written in minicom software which has Fedora9 platform.
Following are its screenshots

Chapter 2 Project Management
2.1 Feasibility Study
2.1.1 Technical feasibility
Project aim required both Hardware and Software
competencies as we were required to build wearable system and robust software to support it.
To check whether it was possible or not we read lot of books to understand basics of ECG
and implemented a simple circuitry shown below from the book called “Biomedical
Instrumentation”. As per our expectations Signal wasn‟t clear as it was theoretical circuit and
not practical but it was clear that project was technically feasible.
2.1.2 Time schedule feasibility
As the Technologies to build the project was Analog
Electronics, XBEE, Java Script, and STK 500 which were completely new to us. We were
quite apprehensive regarding tight Time Schedule within which time frame project needed to
be submitted. But detailed Time Analysis and Disciplined work help us to complete project in
determined time schedule.
2.1.3 Operational feasibility
To acquire operational feasibility we choose java language as
our coding language in software part. Because of that all major features of Java language are
imbibed in our project also. Like reusability inheritance and portability. So this way we
achieved Operational Feasibility.
2.1.4 Implementation feasibility
As we implemented our project‟s software part as Web
Application on J2EE Platform our project can be implemented on any machine and can be
access by any machine. Hence it‟s feasible in Implementation side.
2.2 Project Planning
2.2.1 Project Development Approach and justification
Our project development plan was continuously monitored by
both our External guide and internal guide. Every 15 days we submitted our report and
seminar to our internal guide at our Institution. And almost every week we had discussion
with our External guide regarding our proceedings. On day of our seminar with our internal
guide we had to report our next 15 days goal and decide deadline for the next work. Our
Schedule of project worked smoothly.
2.2.2 Project Plan
Table below shows our schedule.

Date Goal To Be Achieved
15/12/2008 To 28/12/2008 Feasibility Study
29/12/2009 To 03/01/2009 Time Schedule and Analysis
04/01/2009 To 25/01/2009 Requirement Analysis
26/01/2009 To 08/02/2009 Design of Hardware Module
09/02/2009 To 22/02/2009 Implementation of Hardware
Module
23/02/2009 To 01/03 /2009 Design and Implementation of
Wireless Module
02/03/2009 To 08/03/2009 Design and Implementation of
Software Module
09/03/2009 To 22/03/2009 Integration of modules
23/03/2009 To 29/03/2009 Testing and Modifications
30/03/2009 To 04/04/2009 Documentation Finalization
2.2.3 Milestones and Deliverables
Our set goals had been achieved on time hence all the sub goals had been our
milestones which were delivered on time.
2.2.4 Roles and Responsibilities
In our project following Roles were required
1. Requirement Engineer
In our project exhaustive requirement analysis and detailed study of the
subject was required.
2. Design Engineer
As our project was both hardware and software designing of PCB required a
Design Engineer from the Background of Hardware and Web Application
required Software Design Engineer.
3. Programmer
As mentioned above we required programmer with knowledge of Dynamic C
and JavaScript both, which is rare combination. But we learnt the entire
requisite to fulfill all requirements.
2.2.5 Group Dependencies
As it was combined effort, the group never felt that they had lot of
dependencies.

2.3 Project Scheduling
Practical Implementation of Schedule in form of Gantt Chart
Phases 1-
10
11-
20
21-
30
31-
40
41-
50
51-
60
61-
70
71-
80
81-
90
91-
100
101-
110
111-
112
Feasibility Study
Time Schedule
and Analysis
Requirement
Analysis
Design of
Hardware
Module
Implementation
of Hardware
Module
Design and
Implementation
of Wireless
Module
Design and
Implementation
of Software
Module
Integration of
modules
Testing and
Modifications
Documentation
Finalization

Chapter 3 System Requirements Study
3.1 History of Electrocardiogram
The electrical activity accompanying a heart-beat was first discovered by Collier and Mueller
in 1856. After placing a nerve over a beating frog's heart they noticed that the muscle
associated with the nerve twitched once and sometimes twice. Stimulation of the nerve was
obviously caused by depolarization and repolarization of the ventricles. At that time there
were no galvanometers that could respond quick enough to measure the signal, so
Dodders (1872) recorded the twitches of the muscle to provide a graphic representation of the
electrocardiographic signal. In 1876, Mary made use of a capillary electrometer to describe a
crude electrocardiogram of a tortoise using electrodes placed on the tortoise's exposed heart.
The news of this led many investigators to create their own instruments and the ECG of
mammals including humans was taken and different types of electrodes and their positioning
was investigated. One such investigator was Waller, who recorded the ECG of a patient
called Jimmy. Waller later revealed the identity of Jimmy to be his pet bulldog. Jimmy's ECG
was recorded by having a forepaw and hind paw in glass containers containing saline and
metal electrodes as shown in Figure.
Figure 3.1. – Jimmy the Bulldog
The fidelity of ECG obtained using a capillary electrometer was poor and Einthoven (1903)
wanted to create a better system using Adder‟s string telegraphic galvanometer. Einthoven's
system proved to be a great success and soon string galvanometer based ECG systems were
in clinical practice worldwide. Einthoven also came up with his theory regarding the
Einthoven triangle and the lead positions based on this are still in use today and is responsible
for the labeling of the various waves forming an ECG signal.
Figure shows Einthoven's string galvanometer and a patient having his
ECG recorded.

Figure 3.2 – William Einthoven’s ECG System [2]
Since the early 1900s advances have come through the use of a greater number of leads such
as in the augmented lead system or through body surface mapping (>64 recording sites used).
As technology has advanced, so has the measuring system, making use of vacuum tubes,
transistors, integrated chips and microprocessor technology as time has passed. The use of the
electrocardiogram has also spread out from the hospital with ambulatory egg, home
electrocardiography and electrocardiograph telemetry systems in wide use.
3.2 Study of Current System
The electrical impulses within the heart act as a source of voltage, which generates a
current flow in the torso and corresponding potentials on the skin. The potential distribution
can be modeled as if the heart were a time-varying electric dipole.
If two leads are connected between two points on the body (forming a vector between them),
electrical voltage observed between the two electrodes is given by the dot product of the two
vectors [9]. Thus, to get a complete picture of the cardiac vector, multiple reference lead
points and simultaneous measurements are required. An accurate indication of the frontal
projection of the cardiac vector can be provided by three electrodes, one connected at each of
the three vertices of the Einthoven triangle. The 60 degree projection concept allows the
connection points of the three electrodes to be the limbs

Figure 3.3 – Lead Positioning [2]
Modern standard ECG measurement makes use of further electrode connection points. The
12-lead ECG is made up of the three bipolar limb leads, the three augmented referenced limb
leads and the six Wilson terminals (Vow) referenced chest leads. The augmented lead system
provides another look at the cardiac vector projected onto the frontal plane but rotated 30
degrees from that of the Einthoven triangle configuration (Figure 2.6b). The connection of six
electrodes put onto specific positions on the chest and the use of an indifferent electrode
(Vow) formed by summing the three limb leads allows for observation of the cardiac vector on
the transverse plane [3] (Figure2.6c). Other subsets of the 12-lead ECG are used in situations
which don't require as much data recording such as ambulatory ECG (usually 2 leads),
intensive care at the bedside (usually 1 or 2 leads) or in telemetry systems (usually 1lead).
The modern ECG machine has an analogue front-end leading to a 12- to 16bit analog-to-
digital (A/D) converter, a computational microprocessor, and dedicated input-output (I/O)
processors.

3.3 Electrodes used in Electrocardiogram
Electrodes are used for sensing bio-electric potentials as caused by muscle and
nerve cells. ECG electrodes are generally of the direct-contact type. They work as transducers
converting ionic flow from the body through an electrolyte into electron current and
consequentially an electric potential able to be measured by the front end of the egg system.
These transducers, known as bare-metal or recessed electrodes, generally consist of a metal
such as silver or stainless steel, with a jelly electrolyte that contains chloride and other ions
(Figure 3.1).
Figure 3.4 – Recessed Electrode Structure [4]
On the skin side of the electrode interface, conduction is from the drift of ions as the ECG
waveform spreads throughout the body. On the metal side of the electrode, conduction results
from metal ions dissolving or solidifying to maintain a chemical equilibrium using this or a
similar chemical reaction:
Ag ↔ Ag+ + e-
The result is a voltage drop across the electrode-electrolyte interface that varies depending on
the electrical activity on the skin. The voltage between two electrodes is then the difference in
the two half-cell potentials.
Figure 3.5 – Dry Electrode Structure [2]

Plain metal electrodes like stainless steel disks can be applied without a paste. The theory of
operation is the same but the resistivity of the skin electrode interface is much greater. They
are useable when proper electrostatic shielding against interference is applied and the
electrode is connected to an amplifier with very high input impedance, but the voltage
measured will be considerably less than that obtained with an electrode utilizing an
electrolyte.
3.4 Problems and Weaknesses of Current System
Main problem with the current system which is most commonly used
in the hospitals is that it is not compact. It requires 12 leads to cover the view of whole heart.
Due to these reasons patient can not move freely during test. Also long duration of test can
cause irritation to patient.
Patients who are suffering from heart diesis must themselves come to
know about emergency, means every time they can not be in hospitals. So any problem
comes without they are admitted to the hospitals can cause fatal.
3.5 System User Characteristics
System is designed especially for old age people. So the
characteristics are:
 Mobility
 Constant monitoring of patient
 Immediate action during emergency condition
3.5 Hardware and Software requirements
Hardware Requirements:
 Electrodes
 ECG monitor
 Microcontroller IC ATMEGA32
 Transmission part
 Computer System for Doctor
 Internet Explorer
Software Requirements:
 AVR Studio
 PSpice
 Minicom
 Google API mode

Chapter 4 SYSTEM ARCHITECTURE DESIGN
4.1 Pre Amplifier Circuit
Figure 4.1 Pre-Amplifier Circuit
4.2 Post-Amplifier Circuit Diagram

Figure 4.2 Post-Amplifier Circuit
4.3
QRS Detector Circuit Diagram

Figure 4.2 Filter and Rectifier portion of QRS Detector Circuit
Figure 4.3 R-Wave Detector portion of QRS Detector Circuit

Chapter 5 Implementation Planning
5.1 Implementation Environment
We implemented our hardware program that is program in
Microcontroller using AVR Studio and Language used is Dynamic C. Following are the
Details of Special Registers.

5.2 Program Specification
Program Details are as Follows:-

5.3 Coding Standards
 J2EE 1.4 java version is used for making display software
 NET Beans IDE
 Java enabled Web Browser
 JDK for windows is installed
 We have used standard JAVA Naming convention like
1. displayEcg.java
2. showAnnotation.java

Chapter 6 Testing
6.1 Testing Plan
We planned to test our project using unit testing and Integration testing strategy.
Hence Regression Testing method was applied. We implemented at each and every
stage modules and tested their required outputs.
Some of the test results are as follows:-
Figure 6.1 QRS Detector Output

Figure 6.2 1st
ECG Signal
Figure 6.3 Work place circuit implementation

Figure 6.4 Work place part 2

Figure 6.5 Circuit

Figure 6.6 Test Point 1
Figure 6.7 Test Point 2

Figure 6.8 Test point 3

6.2 Testing Strategy
As mentioned above and results shown above we have strictly followed regression
testing completely.

6.3 Testing Methods
Testing methods applied are Unit Testing and Integration Testing.
6.4 Test Cases
6.4.1 Purpose: - To test whether ECG Module was working or
not.
6.4.2 Required Input: - Heart Signal from Patient
6.4.3 Expected Results: - ECG to displayed on Digital
Oscilloscope.
Use Case Test Case Expected
Output
Actual Output Test Case
Status
50 Hz Notch
Filter
Frequency
higher than 50hz
Pass only till 49
Hz
Passed only till
45 Hz
Pass
ECG Module Heart Signal of
50 mille volt
Heart Signal of
2 Volt
Heart Signal of
1.8 Volt
Pass
Hardware
program to
detect
Abnormality
Give Heart pulse
between 60 to
70
Detect it Normal Detected it
Normal
Pass
Give Heart pulse
less than 60
Detect it
Abnormal and
transmit it.
Detected it
Abnormal and
transmit it.
Pass
Software to
Display Heart
Signal
Samples at 1.6
Kilo Hertz
Show it
properly.
Showed it
properly
Pass

Chapter 7 Limitations and Future Enhancements
7.1 Limitations
Following are the limitations of the System.
 The System is not multiparameter. It is including only electrical signal from heart
 Range of XBEE Pro differs according to medium. In closed room range is decreased a
lot.
 Constant wear of electrodes can cause irritation to patient.
 Due to memory constraint and battery ECG signal can‟t transmitted for long period.
7.2 Future Enhancements
Following are the future enhancements intended for the System.
 More features can be added to monitor like SPO2, Blood Pressure and Blood Sugar
level. This way it ensures proper monitoring of patient.
 Range can be improved.
 More powerful power source can be devised so that for longer time ECG can be
transmitted to base station and patient can be diagnosed more precisely.
 GPS System can be added to provide alarm signal to doctor with exact location of
patient so that immediate assistance can be provided.

Chapter 8 Conclusion and Discussion
8.1 Conclusions and Future Enhancement
We are successful in getting accurate ECG signal and Transmitting it to base station
successfully which was our aim. Overall Experience of building this project was enthralling
and unique. So overall it can be concluded that we were successful in making a wearable
ECG system which transmits signal when it detects abnormality.
8.2 Discussion
8.2.1 Self Analysis of Project Viabilities
We did self analysis and project viabilities by meeting few Doctors and
old age home people. This device will be very much useful to both old age homes and old age
people. We goggled lot of topics and found out heart ailments are the major problems for
people of all age. So we concluded that project is most viable both commercially and for
society. Future Enhancements in this project will help technology serve better to mankind.
Portable ECG system is the demand of the day. And its miniaturization will help mankind a
lot.
8.2.2 Problem Encountered and Possible Solutions
Following were the problems encountered and their solutions
 ECG has amplitude of only about 1 mV, so to detect it an amplifier is needed. There
is a problem, though - electrical noise, or electromagnetic interference (EMI). EMI is
generated by many common appliances, such as power lines, fluorescent lights, car
ignitions, motors and fans, computers, monitors, printers, TVs and cell phones.
 When the ECG is amplified, the noise is amplified too, and often swamps the ECG
signal. And the noise is usually of a higher frequency than the ECG.
 In the beginning we implemented amplifier and QRS detector circuits from textbook
which is not give proper output. Then we asked senior students, research engineers,
professors and searched in medical-instrumentation books, reference books, on
Internet Explorer etc.
 Finally we get one circuit of amplifier and QRS detector and implemented them on
PCB board. We changed or added or removed some components in those circuits. In
that we break instrumentation amplifier circuit into Pre-amplifier circuit and Post-
amplifier circuit and also include notch filter and simple amplifier.
 We are using RL configuration in Pre-amplifier which gives better output than RC
configuration.

 Moreover we modify the ECG electrodes and probes from where we take an ECG
signal. In the beginning we used clamp electrodes with long wired probes. Due to
those we faced much noise in signal. Then after we switch over to chest electrodes
with short and shielded probes but we can‟t get sufficient input from them.
So we use combination of them, we use aluminum plate, good conductor under chest
electrodes so that we increase the surface area and take proper ECG signal. But it took much
time in arrangement like to stick them on chest.
So, finally we use limb electrodes which fulfill our requirements.
 To solve the problem of DC offset we put RC circuit at those pins where we give
supply voltage to ICs.
 Another problem is motor driving effect which is due to distribution of supply voltage
from one source to all the ICs. Because of this the internal noise will generate and it
affects the incoming signal that has low amplitude. For its solution we give individual
supply the all the ICs according to their requirement.
 Earthen is one of the problems in our bred board circuit and PCB circuit in lab. For it
we make our module with proper earthen and shielding,
After solving all these problems on board to get better and appropriate output, we design
ECG signal amplifier module with assembly components on GREEN PCB.
8.2.3 Summary of Project work
Our main aim behind this project is to show a way by which old age homes
can monitor their old age people. It is a relief for old age people also they roam about freely
without any assistance. Also they get immediate help from doctors whenever they are in
trouble or in need. We have made it in such a way that even young ones can have it. This
project has huge commercial viability if produced in masses.

Experience
We are going to share an experience we had at DA-IICT Dhirubhai Ambani Institute of
Information and Communication Technology during our project work.
DA-IICT being one of the premier institute of India our expectations was high. After
reaching their the kind of Ambience and Hospitability we received was beyond our
expectation. DA-IICT has very fine architecture with great facilities and above all very
experienced faculty. We were given separate lab to work in with personal computers issued
to us. Also if we needed anything like Resistors, Capacitors, Breadboard etc anything of that
sort it could be issued. Not only small things like that even we were given personal CRO,
DSO and Function generator in our very own lab. We were free to access lab anytime any
day. DA-IICT has one of the most resourceful libraries which we utilize maximum.
Whenever we had some difficulties we got answers from there. Not only that entire lab
building of DA-IICT is Wi-Fi connected we had free access to internet in Lab and also at our
Hostel Rooms. We had very good staying and food facility which made us work more
cheerfully. We also had help of three research engineers who eventually became our very
good friends. They are Mr. Vishwas, Mr. Aman and Mr. Ravi Bagree and we owe special
thanks to them for their support and special attention. Without them project wouldn‟t have
been successful.
Our very sincere thanks to Professor Prabhat Ranjan because it was because of
them we were in DA-IICT. We had very good time and learning time with Sir. We can never
ever pay our thanks to him for what he has given to us and taught us. His dedication in work
inspired us to work more and more. Very sincere thanks to Professor Prabhat Ranjan and we
mean it from our bottom of our heart.
Overall complete experience of DA-IICT was mystic and we shall remember it for our life
time.

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Bibliography / Literature Review
1. Barry N. Feinberg, Applied Clinical Engineering, 1996 Chapters 4 & 5
Chapter four of this book contains a fairly detailed explanation of the electrical
Activity of the heart and what the ECG waveform represents. It goes on to give lead
Locations for standard, augmented and primordial lead systems. Chapter five details
Noise sources and solutions, electrode information including skin/electrode equivalent
Circuits and explanations of performance measures.
2. A. Edward Profit, Biomedical Engineering, 1993 Chapter 3
This book contains similar information to that provided in [1], but provides
Less in-depth explanations. Contains an informative page on microelectrodes.
3. A. Khorovets, What Is An Electrocardiogram?, 2000
www.ispub.com/journals/IJANP/Vol4N2/ekg.html
This article taken from the „Internet Journal of Health‟, contains information
On exactly what activity in the heart the electrocardiogram represents. It includes
Information on what common abnormalities in ECG signals mean in terms of cardiac
Disease or misplaced connection points.
4. S. Choir, J. Nyberg, K. Fudged, E. Kael, Telemedicine ECG – Telemetry with
Bluetooth Technology, Computers in Cardiology 2001, 28:585-588
This journal entry deals with the use of a Bluetooth system to transmit
Digitized ECG data to a Web server via GSM phone modem. The cardiologist then
Can access the ECG data over the web and is also able to make use of the on-line
Knowledge base. The article talked mostly about the results of trials of their system.
5. A. Praetor, C. Malines, Multichannel ECG Data Compression Method Based on a
New Modelling Method, Computers in Cardiology 2001, 28:261-264
The work described in this article concerns a new method of multichannel
ECG data compression based on the identification of a FIR system. The compression
Method achieved is in development but achieved a compression ratio of 8 with a
Signal-to-Reconstruction Noise Ratio of 25dB.
6. Sate M. S. Jalaleddine, Chris well G. Hutchens, William A. Soberly, Robert D.
Stratton, Compression of Halter ECG Data, ISA 1988 – Paper #88-0205
This paper described many compression schemes utilised in compression of
Halter ECG data including problems such as distortion inherent in them. Nine data
Compression techniques are detailed with two more proposed.
7. Robert S. H. Istepanian, Arthur A. Petrofina, Optimal Ronal Wavelet-Based ECG
Data Compression for a Mobile Telecardiology System, IEEE Transactions on

Information Technology in Biomedicine, Vol. 4 No. 3, September 2000
This paper details a new approach for ECG data compression for use in mobile
Telecardiology. The compression achieved a maximum compression ratio of 18:1 and
Was able to reproduce clinically acceptable signals with a 73% reduction in
Transmission time. This compression method is rather complicated and is probably not
Practical for implementation on our slave nodes and also requires a block size for
Compression that is larger than that which is suited for our purposes.
8. Li Gang, Ye Winy, Lin Ling, Yu Qilian, Yu Xiamen, An Artificial-Intelligence
Approach to ECG Analysis, IEEE Engineering in Medicine and Biology, March/April
2000.
Within this paper is contained information on the use of Neural Networks to
Identify QRS complexes in a measured ECG signal. It includes some information on
Compression methods of ECG, which is of some relevance but otherwise is not very
Useful.
9. D. Marr, ECG Application Featuring Data Transmission by Bluetooth, University
Of Queensland Thesis, 2001
The thesis deals with the design of an ECG system which measures and filters
An ECG signal with analogue circuitry before A/D converting it and sending it using
Bluetooth elsewhere. The analogue circuitry detailed is a bit dodgy, and the results
Section is useless.

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