1

CHAPTER 1

INTRODUCTION

Public transportation is provided by the Government as a public service, and its service

quality directly impacts on the travel convenience of the public. As a result, punctual arrival

stations of the buses and accurate reporting stations name are important tasks. At present,

punctuality of buses can be guaranteed because some employee monitor the states of buses

operating and adjust the departure time of buses rationally at the bus start station and bus

terminal. But it is difficult to monitor the punctuality of buses via the intermediate stations.

The purpose of the project is to develop an Intelligent Bus management system. Punctual

arrival stations of the buses and accurate reporting stations name are important tasks. To

solve the question mentioned above, we should obtain the arrival time of buses at

intermediate stations in time. However, these bus stations are distributed in whole city,

vehicles are moving from one place to another ceaselessly, the buses arrival time at

intermediate stations are stochastic. Consequently, the wireless technology should be applied

in the intelligent public transport management system in order to monitoring the buses

operation states. Recently, a method is to use GPS system to monitor the movement of buses,

and then use SMS to send the vehicle location information to the monitoring center.

However, it is difficult to apply the technology in large scale because of the higher the cost of

GPS systems. In fact, we need not to care about the movement process of buses, but

concentrate on the buses arrival time or the departure time at stations. In addition, the bus

driver report station name by pressing a button at present that may misguide passengers when

a mistake occurred.

Most bus station follows fixed schedules, and dont uses intelligent systems for vehicle

tracking and control. Many supervisors are deployed at the station to control the entrance and

the exit of buses and prepare the trip sheets containing the schedules manually which is time

consuming and inaccurate. Moreover, transport departments have no visibility over utilization

of its fleet on real-time, which results in underutilization of resources. So, all these naturally

results in avoidable stress, costly errors and sub cost optimal fleet utilization and finally

dissatisfaction and inconvenience to millions of commuters. The provision of timely and

accurate transit travel time information is so important.

2

New technology provide a smart solution managing the bus schedule in the bus stations

and offering helpful information to passengers. The problems such as underutilization of

buses fleet and long waiting time at the bus station will be reduced. So, both passenger and

bus station administrators will benefit from the system as real time information are provided

1.1 Objectives Of The System

The objectives of the thesis are:

1. To study the various wireless technologies that can be used for bus management

2. Design a best system for intelligent bus management that overcomes the

disadvantages of existing systems.

3. Study and implementation of zigbee technology

4. Implementation of Intelligent public transport management system using zigbee and

GSM/GPRS

1.2 Organization Of The Chapters

The thesis has been organized as follows: Chapter 2 describes about the existing technologies

for bus management and its drawbacks. Chapter 3 describes the research method employed.

The structure of the bus management system and the block diagram explanation of the

subsystems and operation of the system are presented in Chapter 4. The hardware section is

presented in chapter 5. Chapter 6 deals with the protocol stack and architecture of zigbee.

chapter 7 presents the software section with flowcharts of the relevant subsystems. The

simulations results are in chapter 8. Chapter 9 concludes the thesis. More details about GSM

modem,features of ARM and its peripherals,MCB development board,details of developing

tool and details of zigbee are presented in appendix.

3

CHAPTER 2

BACKGROUND INFORMATIN AND LITERATURE SURVEY

Existing wireless identification technologies used for Intelligent Public Transport

Management include Global Positioning System (GPS) and RFID based bus management system

2.1 GPS (Global Positioning System)

Global Positioning System (GPS) has three components namely

1. The space segment: consisting of 24 satellites orbiting the Earth at an altitude of

11000 nautical miles.

2. The user segment: consisting of a receiver, which is mounted on the unit whose

location has to be determined.

3. The control segment: consists of various ground stations controlling the satellites.

The system have permitted civilian use of the satellite signals. Each satellite generates

radio signals that allow a receiver to estimate the distance between the satellite and the

receiver. The receiver then uses these measurements to calculate its own location with

reference to Earth in terms of coordinates expressed in latitude and longitude. Thus the

receiver continuously records its coordinates at given time intervals. This data, which is

continuously recorded, can be stored in a memory module along with the receiver, or it can

also be transmitted instantaneously to the central facility. The former would be an off-line

system and the latter an on-line system.

Fig (2.1) Twenty Four Satellites of GPS

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2.1.1Accuracy Of GPS

GPS has two positioning services:

1. Precise Positioning Service (PPS)

2. Standard Positioning Service (SPS).

PPS is used by authorized users such as U.S. and Allied military while SPS is used by

civilian users worldwide. The accuracy of PPS was within 22 meters, and the accuracy of

SPS was within 100 meters. To improve the accuracy of SPS, an additional correction

(differential) signal was added, and is called Differential GPS (DGPS). The accuracy of

DGPS was better than 10 meters. The SPS accuracy was dramatically improved when the US

military removed the intentional degradation to the signal. Currently the accuracy of PPS and

SPS are the same. The current accuracy of GPS is between 10 and 20 meters, and that of

DGPS is between 3 and 5 meters.

2.1.2 Limitations Of GPS System

i. Higher the cost of GPS system

ii. Sometimes the GPS may fail due to certain reasons and in that case we need to carry a

backup map and directions.

iii. Requires external power supply in case of battery failure

iv. Sometimes the GPS signals are not accurate due to some obstacles to the signals such as

buildings, trees and sometimes by extreme atmospheric conditions such as geomagnetic

storms.

v. The bus driver report station name by pressing a button at present that may misguide

passengers when a mistake occurred.

2.2 RFID

Radio-frequency identification (RFID) is the use of a wireless non-contact system that

uses radio-frequency electromagnetic fields to transfer data from a tag attached to an object,

for the purposes of automatic identification and tracking.

Traditional RFID system consists of three main components

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Fig(2.2) general RFID architecture

1.RFID Reader: sends an electromagnetic wave which carries a signal to identify objects.

Then, the reader receives the information returned back by these objects.

2.RFID tag: attached to these objects, reacts to receiving the signal sent by the reader in

order to forwarding to it the requested information.

3. A computer/database: stores and processes information collected by the reader.

Traditional RFID readers are imitated in their mobility and their potential applications they

are usually connected to the host application via a serial port or via Ethernet.

Some tags require no battery and are powered by the electromagnetic fields used to read

them. Others use a local power source and emit radio waves (electromagnetic radiation at

radio frequencies). The tag contains electronically stored information which can be read from

up to several meters (yards) away. Unlike a bar code, the tag does not need to be within line

of sight of the reader and may be embedded in the tracked object.

A radio-frequency identification system uses tags, or labels attached to the objects to be

identified. Two-way radio transmitter-receivers called interrogators or readers send a signal

to the tag and read its response. The readers generally transmit their observations to a

computer system running RFID software or RFID middleware.

The tag's information is stored electronically in a non-volatile memory. The RFID tag

includes a small RF transmitter and receiver. An RFID reader transmits an encoded radio

signal to interrogate the tag. The tag receives the message and responds with its identification

information. This may be only a unique tag serial number, or may be product-related

information such as a stock number, lot or batch number, production date, or other specific

information.

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RFID tags can be either passive, active or battery assisted passive. An active tag has an

on-board battery and periodically transmits its ID signal. A battery assisted passive (BAP)

has a small battery on board and is activated when in the presence of a RFID reader. A

passive tag is cheaper and smaller because it has no battery. Instead, the tag uses the radio

energy transmitted by the reader as its energy source. The interrogator must be close for RF

field to be strong enough to transfer sufficient power to the tag. Since tags have individual

serial numbers, the RFID system design can discriminate several tags that might be within the

range of the RFID reader and read them simultaneously.

Figure(2.3) Schematic Representation of RFID Technology

Tags may either be read-only, having a factory-assigned serial number that is used as a

key into a database, or may be read/write, where object-specific data can be written into the

tag by the system user. Field programmable tags may be write-once, read-multiple; "blank"

tags may be written with an electronic product code by the user. RFID tags contain at least

two parts: an integrated circuit for storing and processing information, modulating and

demodulating a radio-frequency (RF) signal, collecting DC power from the incident reader

signal, and other specialized functions; and an antenna for receiving and transmitting the

signal. Fixed readers are set up to create a specific interrogation zone which can be tightly

controlled. This allows a highly defined reading area for when tags go in and out of the

interrogation zone. Mobile readers may be hand-held or mounted on carts or vehicles.

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2.2.1Disadvantages Of RFID System

(i) Though it is very beneficial, it quite is expensive to install.

(ii) It is difficult for an RFID reader to read the information in case of RFID tags installed in

liquids and metal products. The problem is that the liquid and metal surfaces tend to reflect

the radio waves, which makes the tags unreadable.

(iii) Interference has been observed if devices such as forklifts and walkies-talkies are in the

vicinity of the distribution centres. The presence of mobile phone towers has been found to

interfere with RFID radio waves.

Thereby we develop an Intelligent Traffic Management System based on Zigbee and

GSM/GPRS in order to solve these disadvantages of GPS and RFID systems.

8

CHAPTER 3

RESEARCH METHOD

The main idea of our research is to integrate Zigbee technology and GSM to build an

intelligent bus tracking system. Two scenarios of integration have been implemented. In the

first one, we have extended the read range of the Zigbee system by adding wireless facility to

Zigbee readers. Each Zigbee reader is equipped with a wireless module which can transmit

data to and from the reader. Zigbee reader acts as sensor node: it reads the identification of an

object and sends it to the host application via an ad-hoc network. The second scenario of

integration provides Zigbee readers with sensing ability. Several motion sensors are installed

near each reader to detect the presence of a tagged object and to command the reader activity.

This approach is tested through an application which can track buses traffic in the bus

station. Here we interface Zigbee with the GSM module. When designing this system, the

following constraints have been considered:

Modularity and expandability constraints: the system must be modular in design. Both

hardware and software should be divided into small components or modules to ensure

easy scalability for further feature expansions. Modules must be produced independently

from each other, so that changes or the crash of one module cannot affect the other ones.

Economic constraint: We should take into account performance to cost ratio so as to

design a cost-effective solution.

Environmental constraint: In our design and implementation, we should keep in mind the

Impact on environment. Low power consumption devices should be used to keep

the power of the system very low. Energy optimization should be involved in all the

designs steps.

9

CHAPTER 4

SYSTEM STRUCTURE

The system we designed comprises of the electronic

boards at stations,

the wireless identifier installed in buses

the monitoring software operated in PC.

Fig(4) structure of bus management system

The electronic modules used in the project is,

XBee/XBee PRO RF Modules

XBee End device

XBee Cordinator

ARM Microcontroller ARM 7 Microcontroller board

GSM/GPRS Modem

And finally the server with database.

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Block Diagrams

The two main subsystems are wireless identifier & station monitor. The block diagrams

are shown below:

4.1 Block Diagram Of Wireless Identifier

Fig(4.1) block diagram of wireless identifier

The function of the zigee end device installed in bus is to communicate with the zigbee

coordinator of the station monitor. The end device has a unique ID and it respond to the RF

signals from the zigbee coordinator.

Zigbee device and LCD is interfaced through the ARM microcontroller.

LCD display helps the passengers by displaying the bus route and by displaying the

station name automatically when the bus enters the station.

4.2 Block Diagram Of Station Monitor

Fig(4.2) block diagram of station monitor

Zigbee coordinator communicate with the zigbee end device. It tracks the bus and sends

the corresponding information to the bus server.

The controller used in the station is the ARM7TDMI family32 bit microcontroller.it is

serially interfaced with the zigbee coordinator.

GSM module is used for the messaging purpose.the relevant informations such as bus ID,

arrival time and leaving time of bus from the station are send to the main server.

Zigbee end device ARM

microcontroller

LCD display

Zigbee

coordinator

ARM

microcontroller

GSM/GPRS

module

LCD display

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LCD display of the station monitor displays the bus ID,route and bus arrival time and

leaving time.

4.3 Operation Of The System

To monitor the runing of buses and improving the punctuality of buses at intermediate

stations, we shoud obtain the accurate arrival time, and send this information to the

company's monitoring center. So, we need not to use the expensive GPS sytem to positioning

their locations. Here, we combine the technology of ZigBee with GSM/GPRS to monitor the

arrival or departure time of buses at stations and report bus stations automatically.

The electronic board of each bus station consists of a station monitor, GSM

communication module and the LCD display. Here, the station monitor is a ZigBee

coordinator which can accept the request from other ZigBee devices to join the network, and

can identify every device configured with ID.

At the same time, we install the wireless identifier device in every bus. When the system

is operating, the station monitor transmit beacon frame continuously. The wireless identifier

in buses can receive the beacon frame which include relevant information about this bus

station, when buses approach the station. Then the bus can report the station name

automatically. Meanwhile, it send itself information to the station monitor, and the monitor

obtain the information about bus ID , arrival time and the license plate number of bus. Those

information can be transmitted back the company's monitoring center by GSM/GPRS system.

After the bus depart from the station, the station monitor also transmit the message-----"XX

bus has left the station" to the center. At the same time, the center send this message to next

station's electronic board and display "XX bus has left YY station, arriving this station at ZZ

time" on the LCD. That can provide convenience for passengers waiting. The monitoring

centre can be in control of the operation of each bus accurately to guarantee its punctuality.

ZigBee's effective operating range is only tens of meters, and it can estimate the distance

between the vehicle and the platform according to the signal strength. As a result, the monitor

can be aware of the bus arrival only when the bus reaches near the station. In addition, the

system can also operate smoothly when many buses approach the same station, because

ZigBee coordinator allow ZigBee devices to connect with it. The whole system's cost is very

low because it has a few of station monitors and low cost wireless identifiers.

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CHAPTER 5

THE HARDWARE DESIGN

Hardware design of the station monitor.

1. The STATION MONITOR consist of,

i. Microcontroller unit (ARM7 )

ii. XBee Coordinator Module

iii. GSM/GPRS module

Same modules are used for each station

The wireless identifier and station monitor comprises of XBee module. Of the XBee

module, one is XBee coordinator and other is XBee end device which is located in bus

(Wireless Identifier)

The XBee coordinator is interfaced to the microcontroller through serial interface, the

XBee information is extracted in the microcontroller, it is manipulated there in accordance

with the format and the corresponding data ie, the bus information and the station information

is sent to the main server through GSM/GPRS module.

Similarly, information from the server about the bus arrival is also send to corresponding

bus station and the arrival time is also displayed on the LCD panel for information of bus

travellers.

5.1 Microcontroller

ARM Microcontroller used in the station is ARM7TDMI family 32-bit microcontroller

LPC2388 which offers high performance and very low power consumption. The ARM

architecture is based on Reduced Instruction Set Computer (RISC) principle and results in a

high instruction throughput and impressive real-time interrupt response from a small and cost

effective processor core. Pipeline techniques are employed so that all parts of the processing

and memory systems can operate continuously. Typically, while one instruction is being

executed, its successor is being decoded and a third instruction is being fetched from

memory. In this project ARM microcontroller is serially interfaced with zigbee module and

GSM module.

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5.2)Xbee Coordinator Module

The coordinator is the most capable device that maintains the overall network knowledge.

It forms the root of the network tree and might bridge to other networks. It is the coordinator

which tracks the bus and send the corresponding information to the bus server. Physical layer

provide the information of link quality which can determine the distance between a receiver

and a sender. The communication distance is usally about tens of meters.

At present, many manufacturers developed the design platform for ZigBee technology. In

this project we are using the Zigbee solution provided by Maxstream XBee/XBee PRO

OEM RF Modules 802.15.4.The XBee and XBee-PRO OEM RF Modules were engineered

to meet IEEE 802.15.4 standards and support the unique needs of low-cost, low-power

wireless sensor networks. The modules require minimal power and provide reliable delivery

of data between devices. The modules operate within the ISM 2.4 GHz frequency band and

are pin-for-pin compatible with each other.

It utilizes direct-sequence spread spectrum modulation and operates on a fixed channel. A

total of 27 channels numbered 0 to 26 are available per channel page. As a result, the

flexibility of ZigBee application can be improved greatly because several different ZigBee

networks in the same area can coexist with each other by selecting different channels.

Comparing with other network technology, the protocol stack of ZigBee network is more

simple and only 32KB flash memory consumption

UART Data Flow

Zigbee module is connected to the microcontroller by the serial interface.Serial Data

Devices that have a UART interface can connect directly to the pins of the RF module as

shown in the figure below.

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Fig(5.1). System Data Flow Diagram in a UARTinterfaced environment (Lowasserted signals distinguished

with horizontal line over signal name.)

Data enters the module UART through the DI pin 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 (least significant bit first) and a stop bit (high).

5.3)Gsm Modem

GSM stands for Global System for Mobile Communication and is an open, digital cellular

technology used for transmitting mobile voice and data services.The GSM Modem is the part

responsible for communication ie, here messaging purpose. GSM is a digital wireless

network standard. It provides a common set of compatible services and capabilities to all

GSM mobile users. The services and security features to subscribers are subscriber identity

confidentiality, subscriber identity authentication, user data confidentiality on physical

connections, connectionless user data confidentiality and signalling information element

confidentiality.

A GSM modem is a specialized type of modem which accepts a SIM card, and operates

over a subscription to a mobile operator, just like a mobile phone. From the mobile operator

perspective, a GSM modem looks just like a mobile phone. When a GSM modem is

connected to a computer, this allows the computer to use the GSM modem to communicate

over the mobile network. While these GSM modems are most frequently used to provide

mobile internet connectivity, many of them can also be used for sending and receiving SMS

and MMS messages. A GSM modem can be a dedicated modem device with a serial, USB or

15

Bluetooth connection, or it can be a mobile phone that provides GSM modem capabilities.

The GSM is a circuit-switched system that divides each 200kHz channel into eight 25kHz

time-slots. GSM operates in the 900MHz and 1.8GHz bands in Europe and the 1.9GHz and

850MHz bands in the US. The GSM makes use of narrowband Time Division Multiple

Access (TDMA) technique for transmitting signals.

Fig(5.2)GSM Modem

Advantages Of Gsm

Improved spectrum efficiency

International roaming

Low-cost mobile sets and base stations (BSs)

High-quality speech

Compatibility with Integrated Services Digital Network (ISDN) and other telephone

company services

Support for new services

5.4 Wireless Identifier

This unit as stated above is powered from the bus and carries limited functionality for

lowering the cost and complexity of the system. The device has just enough functionality to

talk to its parent node ie, the coordinator. There is no problem for power supply because the

monitor installated in station. However, in case of power supply failed, we should take the

capacity of rechargeable battery into account carefully, since GSM/GPRS module would

consume energy a lot. In addition, we should solve the problem of the RF interference

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between GPRS module and ZigBee device in the hardware. The structure of wireless

identifier circuit equipped in bus is really simple.

Figure(5.3) Wireless Identifier in bus

5.5 Server

This part is entirely software which can be developed using JAVA technology. This

requires a database connection which can be ORACLE. The server also requires a

GSM/GPRS connection through which data send by the station monitor is extracted and

corresponding checking of information is done using the database. Then the next location of

corresponding bus is obtained and information is sent to next location

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CHAPTER 6

ZIGBEE

ZigBee is a specification for a suite of high level communication protocols using small,

low-power digital radios based on an IEEE 802 standard for personal area networks. ZigBee

devices are often used in mesh network form to transmit data over longer distances, passing

data through intermediate devices to reach more distant ones. This allows ZigBee networks to

be formed ad-hoc, with no centralized control or high-power transmitter/receiver able to

reach all of the devices. Any ZigBee device can be tasked with running the network.

Fig (6.1)zigbee module

ZigBee is targeted at applications that require a low data rate, long battery life, and secure

networking. ZigBee has a defined rate of 250 kbit/s, best suited for periodic or intermittent

data or a single signal transmission from a sensor or input device. Applications include

wireless light switches, electrical meters with in-home-displays, traffic management systems,

and other consumer and industrial equipment that requires short-range wireless transfer of

data at relatively low rates. The technology defined by the ZigBee specification is intended to

be simpler and less expensive than other WPANs, such as Bluetooth.

A coordinator in ZigBee network can be used to initiate, terminate, or route

communication around the network. The coordinator is the primary controller of the network.

ZigBee devices can also apply to join or leave the network. Physical layer provide the

18

information of link quality which can determine the distance between a receiver and a sender.

The communication distance is usually about tens of meters. To monitoring the running of

buses and improving the punctuality of buses at intermediate stations, we should obtain the

accurate arrival time, and send this information to the company's monitoring centre. Note

that, our concern here is the time of the bus arriving the stations; we are not interesting in

their position and their travel time between stations. So, we need not to use the expensive

GPS system to positioning their locations. Here, we combine the technology of ZigBee with

GSM/GPRS to monitor the arrival or departure time of buses at stations and report bus

stations automatically.

6.1 Protocols

The protocols build on recent algorithmic research (Ad-hoc On-demand Distance Vector,

neuRFon) to automatically construct a low-speed ad-hoc network of nodes. In most large

network instances, the network will be a cluster of clusters. It can also form a mesh or a

single cluster. The current ZigBee protocols support beacon and non-beacon enabled

networks.

Fig(6.2)zigbee protocol stack

In non-beacon-enabled networks, an unslotted CSMA/CA channel access mechanism is

used. In this type of network, ZigBee Routers typically have their receivers continuously

active, requiring a more robust power supply. However, this allows for heterogeneous

19

networks in which some devices receive continuously, while others only transmit when an

external stimulus is detected. The typical example of a heterogeneous network is a wireless

light switch: The ZigBee node at the lamp may receive constantly, since it is connected to the

mains supply, while a battery-powered light switch would remain asleep until the switch is

thrown. The switch then wakes up, sends a command to the lamp, receives an

acknowledgment, and returns to sleep. In such a network the lamp node will be at least a

ZigBee Router, if not the ZigBee Coordinator; the switch node is typically a ZigBee End

Device.In beacon-enabled networks, the special network nodes called ZigBee Routers

transmit periodic beacons to confirm their presence to other network nodes. Nodes may sleep

between beacons, thus lowering their duty cycle and extending their battery 15 life. Beacon

intervals depend on data rate; they may range from 15.36 milliseconds to 251.65824 seconds

at 250 kbit/s, from 24 milliseconds to 393.216 seconds at 40 kbit/s and from 48

millisecondsto 786.432 seconds at 20 kbit/s. However, low duty cycle operation with long

beacon intervals requires precise timing, which can conflict with the need for low product

cost.

In general, the ZigBee protocols minimize the time the radio is on, so as to reduce power

use. In beaconing networks, nodes only need to be active while a beacon is being transmitted.

In non-beacon-enabled networks, power consumption is decidedly asymmetrical: some

devices are always active, while others spend most of their time sleeping .

6.2 ZIGBEE/IEEE 802.15.4 General Characteristics

1) Dual PHY (2.4GHz and 868/915 MHz) , Data rates of 250 kbps (@2.4 GHz), 40 kbps

(@ 915 MHz), and 20 kbps (@868 MHz) , Optimized for low duty-cycle applications

(

20

6.3 Zigbee Network And Architecture

The Co-ordinator is responsible for starting a ZigBee network. Network initialization

involves the following steps:

1. Search for a Radio Channel-The Co-ordinator first searches for a suitable radio

channel (usually the one which has least activity). This search can be limited to those

channels that are known to be usable - for example, by avoiding frequencies in which

it is known that a wireless LAN is operating.

2. Assign PAN ID- The Co-ordinator starts the network, assigning a PAN ID (Personal

Area Network identifier) to the network. The PAN ID can be pre-determined, or can

be obtained dynamically by detecting other networks operating in the same frequency

channel and choosing a PAN ID that does not conflict with theirs.At this stage, the

Co-ordinator also assigns a network (short) address to itself. Usually, this is the

address 0x0000.

3. Start the Network- The Co-ordinator then finishes configuring itself and starts itself in

Co-ordinator mode. It is then ready to respond to queries from other devices that wish

to join the network.

Fig(6.3) Layered Architecture of Zigbee

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6.4 Forming A Zigbee Security Architecture

ZigBee uses 128-bit keys to implement its security mechanisms. A key can be associated

either to a network, being usable by both ZigBee layers and the MAC sub layer, or to a link,

acquired through pre-installation, agreement or transport. Establishment of link keys is based

on a master key which controls link key correspondence. Ultimately, at least the initial

masterkey must be obtained through a secure medium (transport or pre-installation), as the

security of the whole network depends on it. Link and master keys are only visible to the

application layer. Different services use different one way variations of the link key in order

to avoid leaks and security risks.

Key distribution is one of the most important security functions of the network. A secure

network will designate one special device which other devices trust for the distribution of

security keys: the trust center. Ideally, devices will have the trust center address and initial

master key preloaded; if a momentary vulnerability is allowed, it will be

sent as described above. Typical applications without special security needs will use a

network key provided by the trust center (through the initially insecure channel) to

communicate.

Thus, the trust center maintains both the network key and provides point-to-point

security. Devices will only accept communications originating from a key provided by the

trust center, except for the initial master key. The security architecture is distributed among

the network layers as follows:

1) The MAC sub layer is capable of single-hop reliable communications. As a rule, the

security level it is to use is specified by the upper layers.

2) The network layer manages routing, processing received messages and being capable

of broadcasting requests. Outgoing frames will use the adequate link key according to

the routing, if it is available; otherwise, the network key will be used to protect the

payload from external devices.

3) The application layer offers key establishment and transport services to both ZDO and

applications. It is also responsible for the propagation across the network of change

in devices within it, which may originate in the devices themselves (for instance, a

22

simple status change) or in the trust manager (which may inform the network that a

certain device is to be eliminated from it). It also routes requests from devices to the

trust center and network key renewals from the trust center to all devices. Besides

this, the ZDO maintains the security policies of the device. The security levels

infrastructure is based on CCM*, which adds encryption- and integrity-only features

to CCM.

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CHAPTER 7

SOFTWARE DESIGN

The system software includes the application software and the ZigBee protocol

software. Two development methods are provided by TI corporation. One is only a simple

application which takes advantage of MAC layer operation supported by IEEE802.15.4

hardware. Another is a complete ZigBee implementation which includes the function of

network layer and application layer. The API functions of physical layer and MAC layer are

provided by those schemes. We only call those functions when implement the ZigBee

protocol stack. TI corporation offer some design examples in datasheet which can help to

implement our application design.

The software that can run on a simple multi-tasking operating systems, various tasks are

scheduled by the operating system to complete the specific application. Each task has two C

language function, one is the initialization function, another is the event handle fuction. Most

applications can be extended by modifying source code of these examples. There are two

modification methods,adding a new task or increasing an event in the existing task. In order

to avoiding the collision between an existing event and a new event, we should think before

doing that carefully. In addition, this operating system is non-preemptive but order

scheduling, so the time of handling an event should not be taken up too much. We implement

our design by increasing a new event in a task.

The station monitor itself is a ZigBee network coordinator which configured with a

GSM module. When we tum on the device power supply, the GSM/GPRS module and

ZigBee protocol stack would be initialized by MCV. Then the station monitor can use a

channel scan to measure the energy on the channel. Before starting a new network, the results

of a channel scan can be used to select an appropriate logical channel and channel page, as

well as the network identifier that is not being used by any other network in the area. The

superframe is bounded by network beacons sent by the ZigBee coordinator and then waiting

for the connection requestes from ZigBee devices. The coordinator should first confirm their

validity when it receives the connection requestes from ZigBee devices to join the network,

and then send the connection permission command. Once the connection established, the

station monitor can obtain the device identifier and register it in the list. At the same time, the

monitor send the message "XX bus YY clock arrive ZZ station" to monitoring center. Of

24

course, the station monitor allow a lot of devices to connect with it at one time and register

them in the list. When monitor receives the disconnection request from a bus, itdelete the bus

information from the list, and then send the message "XX bus leave YY station". The flow

chart of station monitor is as follows:

Fig(7.1) flowchart of station monitor

The wireless identifier installed in the bus is a ZigBee device too. When power supply is

on, the ZigBee protocol stack is initialized, then the wireless idetifier begin to scan channel

GSM init

Zigbee init

Init PAN

Connect

request?

Valid

request

Register the bus

connect

Send msg with GSM/GPRS

Disconn

ect

request?

Disconnect

Delete registered bus

Begin

Begin

25

and look for a ZigBee coordinator. After detecting the superframe which is transmitted by the

coordinator, the identifier requestes to communicate with the coordinator. The Flow chart of

wireless idetifier is as follows:

no

yes

no

yes

Fig(7.2) Flowchart Of Wireless Identifier

When the connection is established, it would obtain theinformation about the station

monitor. Meanwhile, it can report the name of the bus station automatically. Once the bus

depart from the station, the signal strength is low than a certain level, the bus send the

disconnection request to the station monitor

Begin

Zigbee init

Found a

cooperat

or?

Request connect

Report station

RSSI

value is low?

Disconnect

26

CHAPTER 8

SIMULATION RESULTS

Step I: The code is opened in Keil Microvision IDE and the following operations are done:

Translate Current File

Built Target

Start/Stop Debug Session

Run

fig(8.1)simulation result 1

27

Step II: the zigbee coordinator sending beacon frames containing the information about

station that is displayed in the bus when the zigbee end device is detected.

In the figure below EKLM is the station name transmitted.

Fig 8.2: Simulation ResultII

28

Step III: When any Zigbee end device comes in the range of the beacon frame transmitted by the

zigbee coordinator, it receives the frame and send request to the station or the zigbee coordinator

to establish connection. Here the beacon frame EKLM is given as input into the UART#1windo

of ARM microcontroller associated with the bus.

Fig( 8.3): Simulation ResultIII

29

Step IV: 10-bit ID of the wireless bus identifier stored in the program is given as input to

UART #2 window in the format CTRL +Enter, 10-bit unique ID, Enter

Fig (8.4): Simulation ResultIV

Current station name, 3-bit bus ID and route of the bus is displayed in the LCD of Keil

software and 3-bit bus ID, current station name and bus entering time is displayed in the UART

#1 window.

30

Step V: Bus leaving is programmed in the code as an Interrupt. So pin 2.10 of General Purpose Input/Output

(GPIO 2) Interrupts is activated.

Fig( 8.5): Simulation ResultV

3-bit bus ID, current station name and bus leaving time is displayed in the UART #1 window.

31

CHAPTER 9

CONCLUSIONS

In accordance with the situation of the public transportmanagement system at present, we

design a new intelligent bus monitor and management system by using ZigBeetechnology

and GSM/GPRS technology. It can improve the quality of the public transport service

effectively. Its low cost is easy to accept by many public transport Corporation.

ZigBee's effective operating range is only tens of meters, and it can estimate the distance

between the vehicle and the platform according to the signal strength. As a result, the monitor

can be aware of the bus arrival only when the bus near the station. In addition, the system can

also operate smoothly when many buses approach the same station, because a ZigBee

coordinator allow ZigBee devices to connect with it. The whole system's cost is very low

because it has a few of station monitors and low cost wireless identifiers.

32

APPENDIX

GSM MODEM

GSM Modem Product, provides full functional capability to Serial devices to send SMS

and Data over GSM Network. The product is available as Board Level or enclosed in Metal

Box. The Board Level product can be integrated in to Various Serial devices in providing

them SMS and Data capability and the unit housed in a Metal Enclosure can be kept outside

to provide serial port connection. The GSM Modem supports popular "AT" command set so

that users can develop applications quickly. The product has SIM Card holder to which

activated SIM card is inserted for normal use. The power to this unit can be given from UPS

to provide uninterrupted operation. This product provides great feasibility for Devices in

remote location to stay connected which otherwise would not have been possible where

telephone lines do not exist.

TO TEST GSM MODEM CONNECTIVITY USING HYPER TERMINAL

Select a suitable GSM Modem. Here Pulraj GSM is selected.

Understand the AT Command set required to communicate with the modem.

33

Connect the modem to the computer according to the setup guide specified in the

manual provided with the GSM modem.

Put a valid SIM card into the mobile phone or GSM/GPRS modem.

Connect the mobile phone or GSM/GPRS modem to a computer, and set up the

corresponding wireless modem driver.

Run the MS HyperTerminal by selecting Start -> Programs -> Accessories ->

Communications -> HyperTerminal.

In the Connection Description dialog box, enter a name and choose an icon for the

connection. Then click the OK button.

In the Connect To dialog box, choose the COM port that mobile phone or

GSM/GPRS modem is connecting to in the Connect using combo box. For example,

choose COM1 if the mobile phone or GSM/GPRS modem is connecting to the COM1

port. Then click the OK button.

The Properties dialog box comes out. Enter the correct port settings for the mobile

phone or GSM/GPRS modem. Then click the OK button.

Type "AT" in the main window. A response "OK" should be returned from the mobile

phone or GSM/GPRS modem.

If OK returns, it means your mobile phone or GSM/GPRS modem is connected

successfully.

AT COMMANDS

AT commands are instructions used to control a modem. AT is the abbreviation of

ATtention. Every command line starts with "AT" or "at". That's why modem commands are

called AT commands. There are two types of AT commands:

(i) Basic commands are AT commands that do not start with a "+". For example,

D (Dial), A (Answer), H (Hook control), and O (Return to online data state) are

the basic commands.

(ii) Extended commands are AT commands that start with a "+". All GSM AT

commands are extended commands. For example, +CMGS (Send SMS message),

+CMGL (List SMS messages), and +CMGR (Read SMS messages) are extended

commands.

34

For sending SMS in text Mode:

AT+CMGF=1 press enter

AT+CMGS=mobile number press enter

Once The AT commands is given > prompt will be displayed on the screen. Type the

message to sent via SMS. After this, press ctrl+Z to send the SMS. If the SMS sending is

successful, ok will be displayed along with the message number.

For reading SMS in the text mode:

AT+CMGF=1 Press enter

AT+CMGR= no.

Number (no.) is the message index number stored in the sim card. For new SMS, URC

will be received on the screen as +CMTI: SM no. Use this number in the AT+CMGR

number to read the message.

Application areas

Mobile Transport vehicles.

LAN based SMS server

Alarm notification of critical events including Servers

Network Monitoring and SMS reporting

Data Transfer applications from remote locations

Monitor and control of Serial services through GSM Network

Dispatch notification through SMS.

AMR- Automatic Meter Reading

GSM

Global System for Mobile Communications, originally Groupe Spcial Mobile, is a

standard set developed by the European Telecommunications Standards Institute (ETSI) to

describe protocols for second generation (2G) digital cellular networks used by mobile

phones.

35

Network structure

The structure of a GSM network

The network is structured into a number of discrete sections:

The Base Station Subsystem (the base stations and their controllers).

The Network and Switching Subsystem (the part of the network most similar to a

fixed network). This is sometimes also just called the core network.

The GPRS Core Network (the optional part which allows packet based Internet

connections).

The Operations support system (OSS) for maintenance of the network.

GSM carrier frequencies

GSM networks operate in a number of different carrier frequency ranges (separated into

GSM frequency ranges for 2G and UMTS frequency bands for 3G), with most 2G GSM

networks operating in the 900 MHz or 1800 MHz bands. In rare cases the 400 and 450 MHz

frequency bands are assigned in some countries because they were previously used for first-

generation systems. Most 3G networks in Europe operate in the 2100 MHz frequency band.

Regardless of the frequency selected by an operator, it is divided into time slots for

individual phones to use. This allows eight full-rate or sixteen half-rate speech channels per

radio frequency. These eight radio timeslots (or eight burst periods) are grouped into a

TDMA frame. Half rate channels use alternate frames in the same timeslot. The channel data

rate for all 8 channels is 270.833 kbit/s, and the frame duration is 4.615 ms.The transmission

power in the handset is limited to a maximum of 2 watts in GSM 850/900 and 1 watt in GSM

1800/1900.

ADVANTAGES

Improved spectrum efficiency

International roaming

Low-cost mobile sets and base stations (BSs)

High-quality speech

Compatibility with Integrated Services Digital Network (ISDN) and other telephone

company services

36

ZIGBEE TECHNOLOGY

ZigBee is a specification for a suite of high level communication protocols using small,

low-power digital radios based on an IEEE 802 standard for personal area networks. ZigBee

devices are often used in mesh network form to transmit data over longer distances, passing

data through intermediate devices to reach more distant ones. This allows ZigBee networks to

be formed ad-hoc, with no centralized control or high-power transmitter/receiver able to

reach all of the devices. Any ZigBee device can be tasked with running the network.

Device Types

Zigbee devices are of three types:

ZigBee coordinator (ZC): The most capable device, the coordinator forms the root of

the network tree and might bridge to other networks. There is exactly one ZigBee

coordinator in each network since it is the device that started the network originally. It

stores information about the network, including acting as the Trust Center &

repository for security keys.

ZigBee Router (ZR): As well as running an application function, a router can act as an

intermediate router, passing on data from other devices.

ZigBee End Device (ZED): Contains just enough functionality to talk to the parent

node (either the coordinator or a router); it cannot relay data from other devices. This

relationship allows the node to be asleep a significant amount of the time thereby

giving long battery life. A ZED requires the least amount of memory .

37

Communication and device discovery

In order for applications to communicate, their comprising devices must use a common

application protocol (types of messages, formats and so on); these sets of conventions are

grouped in profiles. Furthermore, binding is decided upon by matching input and output

cluster identifiers, unique within the context of a given profile and associated to an incoming

or outgoing data flow in a device. Binding tables contain source and destination pairs.

Depending on the available information, device discovery may follow different methods.

When the network address is known, the IEEE address can be requested using unicast

communication. When it is not, petitions are broadcast (the IEEE address being part of the

response payload). End devices will simply respond with the requested address, while a

network coordinator or a router will also send the addresses of all the devices associated with

it.

This extended discovery protocol permits external devices to find out about devices in a

network and the services that they offer, which endpoints can report when queried by the

discovering device (which has previously obtained their addresses). Matching services can

also be used. The use of cluster identifiers enforces the binding of complementary entities by

means of the binding tables, which are maintained by ZigBee coordinators, as the table must

be always available within a network and coordinators are most likely to have a permanent

power supply. Backups, managed by higher-level layers, may be needed by some

applications. Binding requires an established communication link; after it exists, whether to

add a new node to the network is decided, according to the application and security policies.

Communication can happen right after the association. Direct addressing uses both radio

address and endpoint identifier, whereas indirect addressing uses every relevant field

(address, endpoint, cluster and attribute) and requires that they be sent to 16 the network

coordinator, which maintains associations and translates requests for communication. Indirect

addressing is particularly useful to keep some devices very simple and minimize their need

for storage. Besides these two methods, broadcast to all endpoints in a device is available,

and group addressing is used to communicate with groups of endpoints belonging to a set of

devices.

38

Advantages Of Zigbee

Zigbee is poised to become the global control/sensor network standard. It has been

designed to provide the following features:

(1)Low power consumption, simply implemented.

(1) Users expect batteries to last many months to years.Consider that a typical single

family house has about 6 smoke/CO detectors. If the batteries for each one only

lasted six months, the home owner would be replacing batteries every month.

(2) Bluetooth has many different modes and states depending upon your latency and

power requirements such as sniff, park, hold, active, etc.; ZigBee/IEEE 802.15.4 has

active (transmit/receive) or sleep. Application software needs to focus on the

application, not on which power mode is optimum for each aspect of operation.

(3) Low cost (device, installation, maintenance)

(4) Low cost to the users means low device cost, low installation cost and low

maintenance. ZigBee devices allow batteries to last up to years using primary cells

(low cost) without any chargers (low cost and easy installation). ZigBees simplicity

allows for inherent configuration and redundancy of network devices provides low

maintenance.

(5) High density of nodes per network ZigBees use of the IEEE 802.15.4 PHY and MAC

allows networks to handle any number of devices. This attribute is critical for

massive sensor arrays and control networks.

(6) Simple protocol, global implementation

(7) ZigBees protocol code stack is estimated to be about 1/4th of Bluetooths or 802.11s.

(8) Simplicity is essential to cost, interoperability, and maintenance. The IEEE 802.15.4

PHY adopted by ZigBee has been designed for the 868 MHz band in Europe, the 915

MHz band in N America, Australia, etc; and the 2.4 GHz band is now recognized to

be a global band accepted in almost all countries.

39

ARM

The ARM7TDMI core is a member of the ARM family of general-purpose 32-bit

microprocessors. The ARM family offers high performance for very low power consumption,

and small size. The ARM architecture is based on Reduced Instruction Set Computer (RISC)

principles. The RISC(software) instruction set and related decode mechanism are much

simpler than those of Complex Instruction Set Computer (CISC) designs. This simplicity

gives:

a high instruction throughput

an excellent real-time interrupt response

a small, cost-effective, processor macro cell

LPC2364/6/8/78 is an ARM-based microcontroller for applications requiring serial

communications for a variety of purposes. These microcontrollers incorporate a 10/100

Ethernet MAC, USB 2.0 Full Speed interface, four UARTs, two CAN channels, an SPI

interface, two Synchronous Serial Ports (SSP), three I2C interfaces

Features

ARM7TDMI-S processor, running at up to 72 MHz.

Up to 512 kB on-chip Flash Program Memory

Up to 32 kB of SRAM on the ARM local bus for high performance CPU access.

16 kB Static RAM for Ethernet interface. Can also be used as general purpose SRAM.

8 kB Static RAM for USB interface. Can also be used as general purpose SRAM.

Dual AHB system that provides for simultaneous Ethernet DMA, USB DMA, and

program execution from on-chip Flash with no contention between those

functions.

External memory controller that supports static devices such as Flash and SRAM. An

8-bit data/16-bit address parallel bus is available in LPC2378 only.

Advanced Vectored Interrupt Controller, supporting up to 32 vectored interrupts.

Serial Interfaces

Ethernet MAC with associated DMA controller. These functions reside on an

independent AHB bus.

USB 2.0 Device with on-chip PHY and associated DMA controller.

Four UARTs with fractional baud rate generation, one with modem control I/O, one

40

with IrDA support, all with FIFO. These reside on the APB bus.

Two CAN channels with Acceptance Filter/FullCAN mode, Three I2C, SPI controller

are reside on the APB bus.

Secure Digital (SD) / MultiMediaCard (MMC) memory card interface.

Up to 70 (LPC2364/6/8) or 104 (LPC2378) general purpose I/O pins.

10 bit A/D converter with input multiplexing among 6 pins (LPC2364/66/68) or 8

pins LPC2378).

10 bit D/A converter.

Four general purpose Timers with two capture inputs each and up to four compare

output pins each. Each Timer block has an external count input.

Real Time Clock with separate power pin, clock source can be the RTC oscillator or

the APB clock.

2 kB Static RAM powered from the RTC power pin, allowing data to be stored when

the rest of the chip is powered off.

Watchdog Timer. The watchdog timer can be clocked from the internal RC oscillator,

the RTC oscillator, or the APB clock.

Standard ARM Test/Debug interface for compatibility with existing tools.

Emulation Trace Module

Single 3.3 V power supply (3.0 V to 3.6 V).

Four reduced power modes: Idle, Sleep, Power Down, and Deep Power down.

Four external interrupt inputs. .

On-chip Power On Reset.

On-chip crystal oscillator with an operating range of 1 MHz to 24 MHz.

MCB 2300

The connectors on the evaluation board provide easy access to many of the on-chip

peripherals.

Block Diagram

The hardware block diagram displays input, configuration, power system, and User I/O

on the board. This visual presentation helps you to understand the MCB2300 board

components.

41

MCB 2300 Development board

42

(1) USB 2.0 Full Speed Interface

Standard USB connectors for USB Device, USB Host and UART via USB on the MCB2300

board for applications requiring USB communications.

(2) LCD Display

A 2-line by 16-character, 8-bit LCD display. You may use this text display device to show

real-time debug and program status messages

(1) SD Card

(2) Power LED

(5) JTAG Download and Debug

A JTAG interface is on the MCB2300 board and, coupled with the ULINK USB-JTAG

adapter, allows flash programming. The on-chip debug interface can perform real-time in-

circuit emulation of the LPC2300 device. For fast PC communication, use your PC's USB

port.

(6) & (7) Dual Serial Ports

Standard DB9 connectors are on the MCB2300 for both of the LPC2300's serial ports

COM1 & COM2

(8) Potentiometer

An adjustable analog voltage source is on the MCB2300 board for testing the Analog to

Digital output feature of the LPC2300. A configuration jumper enables and disables this

feature

(9) Reset: To reset the processor

(10) INT0:To enable external interrupt

(11) Configuration Jumpers: To enable or disable certain features

(12) Processor: LPC 2388

(13) Prototyping area

(14) LF Amplifier

An LF Amplifier on the MCB2300 connects the D/A output of the LPC2300 device to a

speaker & use this LF Amplifier to generate sound.

43

(15) configuration jumper for LF amplifier

(16) & (17) Dual CAN Ports

Standard DB9 connectors are on the MCB2300 board for applications requiring CAN

communications .Application may use either or both of these ports, or they may be disabled

with a configuration jumper.

(18) configuration jumper for USB

(19) Host USB

(21) Power USB

Applications

Industrial control

Medical systems

User Peripherals

(1)General Purpose I/O

The LPC23xx has up to five General purpose IO ports which each contain 32 IO lines

giving a maximum of 160 pins..PORT0 and PORT2 can generate an interrupt when there is a

rising or falling edge on an individual pin.

Fast IO Registers

To maintain compatibility with the earlier LPC21xx devices PORT0 and PORT1 have

aset of control registers on the APB bus. But controlling these two ports by these registers is

quite slow. The LPC23xx family has a second set of GPIO control registers located on the

local bus called the Fast GPIO control registers. On reset the pin connect block configures all

the peripheral pins to be general purpose I/O (GPIO) input pins. The GPIO pins are

controlled by four registers, as shown below

44

Each GPIO pin is controlled by a bit in each of the four GPIO registers. These bits data direction, set,clear and pin status .The FIODIR pin allows each pin to be individually

configured as an input (0) or an output (1). If the pin is an output the FIOSET and FIOCLR

registers allow you to control the state of the pin. Writing a 1 to these registers will set or clear the corresponding pin. The state of the GPIO pin can be read at any time by reading the

contents of the FIOPIN register The FIOMASK register is used to mask individual bits of the

FIOSET,FIOCLR and FIOPIN register. If a bit in the FIOMASK register is set to 0 the corresponding bit in the FIOSET,FIOCLR and FIOPIN will be updated. This masking helps speed up low level IO bit manipulation.

PORT0 and PORT1 can be accessed as general purpose as well as fast ports, but

P2,P3&P4 can be accessed only as fast ports.

(2)UART

The LPC23xx devices currently have four on-chip UARTS. They are all identical to use ,

but UART1 has additional modem support and UART3 which has IrDA support. All the

UARTs have a built-in Baud rate generator with autobaud capability and 16 byte transmit

and receive FIFOs

First the pinselect block must be programmed to switch the processor pins from GPIO to the

UART functions.Then LCR configures the format of transmitted data. Usually the character

format is set to 8 bits, no parity and one stop bit. In the LCR, there is an additional bit called

DLAB which is the divisor latch access bit. In order to be able to program the Baud rate

generator, this bit must be set. The Baud rate generator is a sixteen bit prescaler which

divides down Pclk to generate the UART clock which must run at 16 times the Baud rate.

This is formula used to calculate the UART Baud rate

Divisor = Pclk/16 * BAUD

Consider Pclk= 30MHz,

Divisor = 30,000,000/16 x 9600 = 194 or 0xC2

Often it is not possible to get an exact Baud rate for the UARTs, they will work with up to

around a 5% error in the bit timing. The divisor value is held in two registers: Divisor latch

45

MSB (DLM) and Divisor latch LSB (DLL). The first eight bits of both registers holds each

half of the divisor as shown below. Finally, the DLAB bit in the LCR register must be set

back to zero to protect the contents of the divisor registers.

Data Transfer

Once the UART is initialised, characters can be transmitted by writing to the Transmit

Holding Register.Similarly, characters may be received by reading from the Receive Buffer

Register. Both these registers occupy the same memory location. Writing a character places

the character in the transmit FIFO and reading from this location loads a character from the

Receive FIFO. The putchar() and getchar functions are used to read/write a single character

to the UART. These low level drivers are called by the Keil STDIO functions such as printf()

and scanf(). So, if you want to re direct the standard I/O from the UART to say an LCD

display and a keypad, rewrite these functions to support sending and receiving a single

character to your desired I/O devices. Both the putchar() and getchar() functions read the

Link Status Register (LSR) to check on UART error conditions and to check the status of the

receive and transmit FIFOS

(3)ADC(Analog to Digital Converter)

The A/D converter present on LPC2300 variants is a 10-bit successive approximation

converter with a conversion time of 2.44 uSec. The A/D converter has either 6 or 8

multiplexed inputs depending on the variant. The converter is available with 4 or 8 channels

of 10-bit resolution.

The A/D control register establishes the configuration of the converter and controls the start

of conversion. The first step in configuring the converter is to set up the peripheral clock. The

A/D clock is also derived from the PCLK. This PCLK must be divided down to equal

4.5MHz. This is a maximum value and if PCLK cannot be divided down to equal 4.5MHz

then the nearest value below 4.5MHz which can be achieved should be selected AD Control

register: The control register PCLK is divided by the value stored in the CLKDIV field plus

one. Hence the e quation for the A/D clock is as follows:

CLKDIV = (PCLK/Adclk) - 1

Unlike other peripherals the A/D converter can make measurements of the external pins

when they are configured as GPIO pins. The A/D has a maximum resolution of 10 bits but

can be programmed to give any resolution do wn to 3 bits. The conversion resolution is equal

46

to the number of clock cycles per conversion minus one. Hence for a 10-bit result the A/D

requires 11 ADCLK cycles and four for a 3-bit result. Once you have configured the A/D

resolution, a conversion can be made. The A/D has two conversion modes, hardware and

software. The hardware mode allows you to select a number of channels and then set the A/D

running. In this mode a conversion is made for each channel in turn until the converter is

stopped. At the end of each conversion the result is available in the A/D Global data register

and in a dedicated results register for each channel, ADDR0 ADDR7.

At the end of a conversion the Done bit is set and an interrupt may also be generated if

the global enable and channel interrupt enable bits are set in the AtoD Interrupt enable

register. The conversion result is stored in the V/Vdd a field as a ratio of the voltage on the

analog channel, divided by the voltage on the analog power supply pin. The number of the

channel for which the conversion was made is also stored alongside the result. This value is

stored in the CHN field. Finall y, if the result of a conversion is not read before the next result

is due, it will be overwritten by the fresh result and the OVERUN bit is set to on e. If you are

using multiple A/D channels the A/D status register provides global access to the DONE and

Overrun bits for each channel

(4)Digital To Analog Converter

The LPC23xx variants have a 10-bit Digital to analog converter. This is an easy-to-use

peripheral as it only has a single register. The DAC is enabled by wr iting to bits 20 and 21 of

PINSEL1 and converting pin 0.26 from GPIO to the AOUT function. It should also be noted

that a channel of the analog to digital converter also shares this pin. The DAC is controlled by

a single register. The value to be converted is written here along with the bias value. Once

enabled a conversion can be started b y writing to the VALUE bits in the control register.

The conversion time is dependant on the value of the BIAS bit. If it is set to one the

conversion time is 2.5uSec but it can drive 700 uA. If it is zero, the conversion time is 1 uSec

but it is only able to deliver 350 uA. However, the total settling time is also dependent on the

external impedance and the data setsheet values are valid for a 100pFcapacitance

(5)Real Time Clock

The LPC23xx Real Time Clock (RTC) is a clock calendar accurate up to the year 2099.

The RTC has the option to run from and external 32KHz watch crystal or from the internal

PCLK. The RTC also has an associated 2K of Low power SRAM called the battery RAM.

47

The RTC and batter y SRAM have a separate p ower domain so by supplying 3.3V to the

Vbat pin, the RTC can be kept running and the contents of the battery ram may be preserved

when the LPC2 3xx is powered down. Both the RTC and the battery ram are designed to

consume minimum power and can be run from a battery. This arrangement means that the

RTC may be used to provide a perpetual clock calendar, if this is not re quired, the RTC can

be used to provide a time reference and periodic interrupts without the need for an additi ona

l external oscillator

(6)Timer

The LPC23xx has four general purpose timers. All of the general purpose timers are

identical in structure and use. The timers are based around a 32-bit timer-counter with a 32-

bit prescaler. The default clock source for all of the timers is the APB peripheral clock Pclk.

The tick rate of timer is controlled by the value stored in the prescaler register. The prescaler

register will increment on each tick of Pclk until it reaches the value stored in prescaler

register. When it reaches the prescale value, the timer-counter is incremented by one and the

prescale counter resets to zero, and starts counting again.

Capture Mode : Each timer has upto four capture channels. The capture channels allows

to capture the value of the timer-counter when an input signal makes a transition.

Counter Mode : The count control register allows to select between each timer as a

counter or a pure timer.

Match Mode : Each timer has upto four match channels. Each match channel has a match

register which stores a 32-bit number. The current value of timer-counter is compared against

the match register. When the values match, an event is triggered.

48

DEVELOPING TOOL

Vision3 Overview

The Vision3 IDE is a Windows-based software development platform that combines a

robust editor, project manager, and make facility. Vision3 integrates all tools including the

C compiler, macro assembler, linker/locator, and HEX file generator. Vision3 helps

expedite the development process of your embedded applications by providing the following:

Full-featured source code editor,

Device database for configuring the development tool setting,

Project manager for creating and maintaining your projects,

Integrated make facility for assembling, compiling, and linking your embedded

applications,

Dialogs for all development tool settings,

True integrated source-level Debugger with high-speed CPU and peripheral simulator,

Advanced GDI interface for software debugging in the target hardware and for

connection to Keil ULINK,

Flash programming utility for downloading the application program into Flash ROM,

Links to development tools manuals, device datasheets & user's guides.

The Vision3 IDE offers numerous features and advantages that help you quickly and

successfully develop embedded applications. They are easy to use and are guaranteed to help

you achieve your design goals.

The Vision3 IDE and Debugger is the central part of the Keil development toolchain.

Vision3 offers a Build Mode and a Debug Mode.

In the Vision3 Build Mode you maintain the project files and generate the application.In the

Vision3 Debug Mode you verify your program either with a powerful CPU and peripheral

simulator or with the Keil ULINK USB-JTAG Adapter (or other AGDI drivers) that connect

49

the debugger to the target system. The ULINK allows you also to download your application

into Flash ROM of your target system

50

REFERENCES

[1] A Bus Management System Based on ZigBee 978-1-4244-7237-6/10/$26.00 2010

IEEE

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