avr web server

March 2009

AVR MICROCONTROLLER BASED WEB SERVER

Submitted by

Vishram Mishra

in partial fulfillment of requirement of the Degree of

Bachelor of Technology (B.Tech)

in

COMPUTER SCIENCE AND ENGINEERING

SCHOOL OF ENGINEERING

COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY

KOCHI- 682022

COCHIN UNIVERSTY OF SCIENCE AND TECHNOLOGYDIVISION OF COMPUTER ENGINEERING

CENTRE FOR ENGINEERING STUDIESCOCHIN-682022

Certficate

Certified that this is a bonafide record of the project work entitled

“AVR MICROCONTROLLER BASED WEB SERVER”

done by the following student

VISHRAM MISHRA

Of the VIthsemester ,Computer Science and Engineering in the year 2009 in partial

fulfilment of the requirements to the award of Degree Bachelor of Technology in

Computer Science and Engineering of Cochin Universty of Science and Technology.

Mr.Vinod Kumar P.P. Dr. David PeterProject Guide Head of the Department

Place:KochiDate:30.03.2009

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ACKNOWLEDGEMENT

I take this occasion to thank God, Almighty for blessing me with

his grace and taking my endeavor to a successful culmination. I extend

my sincere and heart felt thanks to my esteemed guide, Mr. Vinod Kumar

P.P. for providing me with the right guidance and advice at the crucial

junctures and for showing me the right way. I extend my sincere thanks to

my respected head of the division Dr. David Peter, for allowing me to use

the facilities available. I would like to thank the other faculty members

also ,at this occasion. Last but not least, I would like to thank my friends

and family for the support and encouragement they have given to me

during the course of my work.

Vishram Mishra

Abstract

This project aims at implementing a web server over an AVR

Microcontroller. The web server will host a small web page which will be

stored in the Microcontroller’s Flash memory. Through the interface of

the web page, a user can control the devices attached to the

Microcontroller. Additionally an LCD is also interfaced with the

Microcontroller to provide user interface through the use of four keys.

I am sure that this project will be helpful to control the devices remotely

by embedding AVR web server onto each of the devices to be controlled.

ii

LIST OF TABLES

1 Two pair crossover cable pin outs..............................................14

2 SPI pins of ATmega32 Microcontroller.....................................16

3 Classes of IP...............................................................................25

4 HTTP Methods...........................................................................35

5 HTTP status code.......................................................................35

iii

LIST OF FIGURES

1.1 Monitoring Home Equipment from the Office....................................2

1.2 Implementation of Web Server using 8-bit Microcontroller….............2

2.1 Pin Configuration of ATmega32 Microcontroller.................................5

2.2 Block Diagram of ATmega32...............................................................6

2.3 AVR CPU Core.....................................................................................8

2.4 Pin Configuration of ENC28J60...........................................................9

2.5 Block diagram of ENC28J60..............................................................10

2.6 Connection of ENC28J60 with Microcontroller.................................11

2.7 MagJack...............................................................................................12

2.8 Schematic of Integrated Magnetics RJ-45 Jack..................................12

2.9 RJ-45 Connector..................................................................................13

2.10 Interaction between different devices supporting SPI.........................15

2.11 Pins of LM 7805..................................................................................17

2.12 Pins of LM 317....................................................................................17

2.13 JHD 162A LCD display......................................................................18

2.14 AVR Web Server Interfacing..............................................................19

2.15 TCP/IP protocol stack.........................................................................20

2.16 Example of various protocols involvesd.............................................22

2.17 Encapsulation of data as it goes down the protocol stack...................24

2.18 Five different classes of internet addresses.........................................25

2.19 IP headers fields................................................................................26

2.20 Encapsulation of TCP data in IP datagram.........................................29

2.21 TCP header fields................................................................................30

iv

2.22 Ethernet Encapsulation.......................................................................32

2.15 Example POST request.......................................................................34

2.15 HTTP response message.....................................................................34

4.1 AVR web server screen shot…...........................................................44

7.1 Select New Project in AVR Studio....................................................47

7.2 Select AVR GCC in AVR Studio......................................................48

7.3 Select Microcontroller type................................................................48

7.4 Write the program in the editor..........................................................49

7.5 Setup the interface of PonyProg .........................................................50

7.6 Select the appropiate hardware programmer type..............................50

7.7 Write appropriate configuration bits..................................................51

7.8 Burn the code onto the Microcontroller.............................................51

7.9 Error message of PonyProg................................................................52

7.10 Parallel Port Programmer Hardware..................................................53

v

TABLE OF CONTENTS

ACKNOWLEDGEMENT....................................................................i

ABSTRACT.........................................................................................ii

LIST OF TABLES...............................................................................iii

LIST OF FIGURES..............................................................................iv

TABLE OF CONTENTS.....................................................................vi

1. INTRODUCTION.....................................................................................1

1.1 Embedded Web Server.........................................................................1

1.2 8-bit Microcontroller Based Web Server.............................................1

2. SYSTEM STUDY.....................................................................................4

2.1 HARDWARE...........................................................................................4

2.1.1 Atmel ATmega32 Microcontroller.........................................................4

2.1.1.1 PIN Configuration.....................................................................5

2.1.1.2 Overview...................................................................................5

2.1.1.3 AVR CPU Core.........................................................................7

2.1.2 ENC28J60 Ethernet Controller...............................................................9

2.1.2.1 Pin Configuration......................................................................9

2.1.2.2 Overview...................................................................................9

2.1.3 Integrated Magnetics RJ-45 Jack ..........................................................12

2.1.3.1 Overview.................................................................................12

2.1.3.2 AutoMDIX ..............................................................................12

2.1.3.3 Cabling....................................................................................13

2.1.4 SPI (Serial Peripheral Interface) ..........................................................14

2.1.4.1 Overview.................................................................................14

vi

2.1.4.2 Data transmission between Master and Slave................................15

2.1.4.3 Pins of the SPI.........................................................................16

2.1.5 Miscellaneous Components..................................................................17

2.1.5.1 LM 7805 IC.............................................................................17

2.1.5.2 LM 317 IC ..............................................................................17

2.1.5.3 JHD-162A LCD Display.........................................................18

2.1.6 Interfacing of Different Components....................................................19

2.2 NETWORKING....................................................................................20

2.2.1 TCP/IP Protocol Suite................................................................20

2.2.1.1 Application Layer..........................................................20

2.2.1.2 Transport Layer.............................................................21

2.2.1.3 Network Layer..............................................................21

2.2.1.4 Link Layer.....................................................................21

2.2.2 Combining all.............................................................................22

2.2.3 Port Numbers..............................................................................23

2.2.4 Encapsulation........................................................................................23

2.2.5 Internet Addresses......................................................................25

2.2.6 IP (Internet Protocol) .................................................................26

2.2.6.1 IP Header.......................................................................26

2.2.7 TCP (Transmission Control Protocol) .......................................28

2.2.7.1 TCP Header...................................................................29

2.2.8 Ethernet Encapsulation...............................................................32

2.2.9 HTTP (Hyper Text Transfer Protocol) ......................................33

2.2.9.1 HTTP Message .............................................................33

2.2.9.2 HTTP Methods..............................................................34

2.2.9.3 Status Codes..................................................................34

vii

viii

2.2 Software Package..................................................................................36 2.3.1 WinAVR....................................................................................36

2.3.2 AVR Studio version 4................................................................36

2.3.3 PonyProg....................................................................................36

3. Software Code...................................................................................38

3.1 Header Files..................................................................................38

3.1.1 enc28j60.h........................................................................38

3.1.2 arp.h..................................................................................38

3.1.3 ip.h....................................................................................39

3.1.4 tcp.h..................................................................................39

3.1.5 http.h ................................................................................40

3.1.6 menu.h..............................................................................41

3.1.7 main.h...............................................................................42

4. EXECUTION.....................................................................................43

4.1 Testing and Debugging.......................................................43

4.2 Procedure for Execution......................................................43

5. CONCLUSION..................................................................................45

REFERENCES..................................................................................46

APPENDICES...................................................................................47

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CHAPTER 1

INTRODUCTION

This chapter provides an introduction to the embedded web server and their

implementation. Their typical application is explained with the help of examples.

Section 1.2 gives a brief explanation of implementation of embedded web server

based on Atmel AVR microcontroller.

1.1 Embedded Web Server

Small systems to large systems may provide an interface and control via the

onboard switches or via IR or RF based remote control. But what if the User who

wants to control a device, is out of reach of the device or is at another part of world.

There are other methods developed to control the devices remotely, but each

technique requires some new implementations to be done. Here we use the existing

technique of Internet Web based HTTP protocol with TCP/IP protocol suite to control

the devices. Embedding a web application in a system is termed as embedded web

server.

Suppose an Embedded Web Server is embedded in several units in a house as

shown in figure 1.1. Every server is connected to the network. A computer located at

home as on figure controls all devices and can receive requests from other computers

on the Internet. The web server is identified by its unique IP address and can be

controlled remotely from anywhere in the world.

A computer located in an office may send a request to turn off the Refrigerator

located at home via Internet. The web server will be running an HTTP application

through the interface of which the user can control and monitor the devices.

1.2 8-bit Microcontroller based Web Server

It is not a new technique to control or monitor a device via web based

interface. Many of the day-to-day life devices are already using this technique. For

example a printer connected via an Ethernet link, Remote Surveillance Camera etc

provides such services. But all these devices use 32 bit-processors like ARM, AVR32,

Division of Computer Engineering, S.O.E. 1

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COLDFIRE, POWER ARCHITECTURE etc. The usage of these 32-bit

microprocessor increases the cost of an application. For a simple Embedded Web

Server we can also use 8-bit Microcontrollers!

Fig 1.1: Monitoring Home Equipment from the Office

The following high level diagram explains how we can implement a web server on an

8-bit Microcontroller.

Fig 1.2: Implementation of Web Server using 8-bit Microcontroller


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Fig 1.2 shows how an 8-bit microcontroller is interfaced with an Ethernet controller

which controls the physical layer of TCP/IP stack model. The standard RJ-45

connector is used for interfacing the Ethernet controller with a PC. When a request is

made from the web browser it is transferred as raw bits through the Ethernet lines and

is then fetched by the Ethernet Controller. The Ethernet Controller then passes this

information above to it that is to the Microcontroller. The program running on the

microcontroller then decodes the request and performs the required operation.

Usage of 8-bit AVR Microcontroller simplifies the design step. One of the most

popular 8-bit AVR Microcontroller is ATmega32 which has 32 Kb of Flash memory,

large enough for storing a small web page.

In the next coming sections we will perform system study and deals with various

hardware and software requirements of the project.


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CHAPTER 2

SYSTEM STUDY

In this section we perform the system study by studying and analyzing various

hardware, software requirement and constraints. Section 2.1 deals with the hardware

requirements and explains the constraints associated with some of the hardware. The

constraints are removed by selecting different hardware. Section 2.2 deals with the

study of networking which is required for writing the various protocols. These

protocols include TCP, IP, HTTP, ICMP etc. In section 2.3 we give a brief

introduction to the software packages used.

2.1 Hardware Study

To implement a web server on an 8 bit Microcontroller we will use AVR

microcontroller because of its high throughput. Also ENC28J60 Ethernet controller is

used instead of Realtek family of Ethernet controller because of low number of pins

which provides an easy interfacing with 8 bit Microcontroller.

We will discuss some of the following important components in brief (For further

study their datasheet can be referred):

Atmel ATmega32 Microcontroller.

ENC28J60 Ethernet Controller.

Integrated Magnetics RJ -45 Jack.

Along with these we will also discuss some of the miscellaneous components used

and about the SPI (Serial Peripheral Interfacing) used to interface ATmega32 with

ENC28J60.

2.1.1 Atmel ATmega32 Microcontroller

A Microcontroller is a highly integrated chip that contains all the components

comprising a controller. Typically this includes a CPU, RAM, some form of ROM,


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I/O ports, and timers. The reason for using ATmega32 as an 8-bit Microcontroller in

our application is because of its high throughput and SPI(Serial Peripheral Interface)

interfacing. The SPI interfacing provides serial interface with the device and hence

lowering the number of address and data lines used.

2.1.1.1 PIN Configuration

Fig 2.1: Pin Configuration of ATmega32 Microcontroller

2.1.1.2 Overview

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

AVR enhanced RISC architecture. By executing powerful instructions in a single

clock cycle, the ATmega16 achieves throughputs approaching 1 MIPS per MHz

allowing the system designer to optimize power consumption versus processing

speed. The block diagram is shown in fig 2.2.


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Fig 2.2: Block Diagram of ATmega32

The AVR core combines a rich instruction set with 32 general purpose

working registers. All the 32 registers are directly connected to the Arithmetic Logic

Unit (ALU), allowing two independent registers to be accessed in one single

instruction executed in one clock cycle. The resulting architecture is more code

efficient while achieving throughputs up to ten times faster than conventional CISC

microcontrollers.


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The ATmega32 provides the following main features:

Up to 16 MIPS Throughput at 16 MHz

On-chip 2-cycle Multiplier

32K Bytes of In-System Self-programmable Flash program memory

1024 Bytes EEPROM

2K Byte Internal SRAM

In-System Programming by On-chip Boot Program

JTAG (IEEE std. 1149.1 Compliant) Interface

Two 8-bit Timer/Counters with Separate Prescalers and Compare Modes

One 16-bit Timer/Counter with Separate Prescalers, Compare Mode, and

Capture Mode

Real Time Counter with Separate Oscillator

Four PWM Channels

8-channel, 10-bit ADC

Byte-oriented Two-wire Serial Interface

Programmable Serial USART

Master/Slave SPI Serial Interface

Programmable Watchdog Timer with Separate On-chip Oscillator

On-chip Analog Comparator

Internal Calibrated RC Oscillator

External and Internal Interrupt Sources

Six Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down,

Standby and Extended Standby

2.1.1.3 AVR CPU Core

The main function of the CPU core is to ensure correct program execution.

The CPU must therefore be able to access memories, perform calculations, control

peripherals, and handle interrupts. Figure 2.3 represents a typical AVR CPU core.


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In order to maximize performance and parallelism, the AVR uses Harvard

architecture – with separate memories and buses for program and data. Instructions in

the program memory are executed with a single level pipelining. While one

instruction is being executed, the next instruction is pre-fetched from the program

memory. This concept enables instructions to be executed in every clock cycle. The

program memory is In-System Reprogrammable Flash memory.

Fig 2.3: AVR CPU Core

The fast-access Register File contains 32 x 8-bit general purpose working

registers with a single clock cycle access time. Six of the 32 registers can be used as

three 16-bit indirect address register pointers for Data Space addressing – enabling

efficient address calculations.

The ALU supports arithmetic and logic operations between registers or

between a constant and a register. Single register operations can also be executed in

the ALU. After an arithmetic operation, the Status Register is updated to reflect

information about the result of the operation.


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2.1.2 ENC28J60 Ethernet Controller

An Ethernet Controller is a device used to implement Ethernet Protocol. The

reason for using ENC28J60 as an Ethernet Controller in our application is because its

supports SPI(Serial Peripheral Interface) interfacing. The SPI interfacing provides

serial interface with the device and hence lowers the number of address and data lines

used.

2.1.2.1 Pin Configuration

Fig 2.4: Pin Configuration of ENC28J60

2.1.2.2 Overview

The ENC28J60 is a stand-alone Ethernet controller with an industry standard

Serial Peripheral Interface (SPI). It is designed to serve as an Ethernet network

interface for any controller equipped with SPI. The ENC28J60 meets all of the IEEE

802.3 specifications. It incorporates a number of packet filtering schemes to limit

incoming packets. It also provides an internal DMA module for fast data throughput

and hardware assisted checksum calculation, which is used in various network

protocols. Communication with the host controller is implemented via an interrupt pin

and the SPI, with clock rates of up to 20 MHz. Two dedicated pins are used for LED


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link and network activity indication. A simple block diagram of the ENC28J60 is

shown in figure 2.5. With the ENC28J60, two pulse transformers and a few passive

components are all that is required to connect a microcontroller to an Ethernet

network.

Fig 2.5: Block diagram of ENC28J60

The ENC28J60 consists of seven major functional blocks:

1. An SPI interface that serves as a communication channel between the host

controller and the ENC28J60.

2. Control Registers which are used to control and monitor the ENC28J60.

3. A dual port RAM buffer for received and transmitted data packets.

4. An arbiter to control the access to the RAM buffer when requests are made from

DMA, transmit and receive blocks.

5. The bus interface that interprets data and commands received via the SPI interface.

6. The MAC (Medium Access Control) module that implements IEEE 802.3

compliant MAC logic.

7. The PHY (Physical Layer) module that encodes and decodes the analog data that is

present on the twisted pair interface.


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Following are the features of ENC28J60:

IEEE 802.3 compatible Ethernet controller

Integrated MAC and 10BASE-T PHY

Supports one 10BASE-T port with automatic polarity detection and correction

Supports Full and Half-Duplex modes

Programmable automatic retransmit on collision

Programmable padding and CRC generation

Programmable automatic rejection of erroneous packets

SPI Interface with clock speeds up to 20 MHz

A typical application circuit using the device is shown in the following figure 2.6

Fig 2.6: Connection of ENC28J60 with Microcontroller

Here only five lines are required to interface the Microcontroller with the

ENC28J60. Whenever a data packet is received by ENC28J60 it sends an interrupt to

the Microcontroller. Based upon the timing of the interrupt the main program checks

the packet received and check to which protocol it belong. Based on that, appropriate

handling is done.


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2.1.3 Integrated Magnetics RJ-45 Jack

2.1.3.1 Overview

An integrated Magnetics RJ-45 Jack includes the required Pulse Magnetics

within the RJ-45 Jack itself. Generally a pulse transformer is used in conjunction with

the RJ 45 jack to maintain the input pulse waveform and power while transforming

the source impedance to a value approximating the load impedance. The use of

Integrated Magnetics RJ-45 Jack excludes the overhead of using Pulse Transformer in

the Circuit.

A typical circuit inside of a Integrated Magnetics

RJ-45 is shown in figure 2.8. Figure 2.7 shows a typical

Integrated Magnetics RJ-45 jack called as MagJack. The

MagJack also provide a feature called as AutoMDIX.

Fig 2.8: Schematic of Integrated Magnetics RJ-45 Jack


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2.1.3.2 AutoMDIX

An Ethernet has one wire pair for transmit (Tx) and one for receive (Rx). A

Hub/Switch will amplify the signal and cross connect Tx of one network element with

Rx of the other. If we want to connect the AVR web server directly to our computer

without a Hub/Switch in-between then we will normally need a cross connect

Ethernet cable. A cross connect cable is a cable where Tx and Rx are swapped on one

side. The AutoMDIX magjack has some additional logic inside which will

automatically swap the cable for us if needed. In other words we can always use a

straight cable no matter if weconnect to a Hub/Switch or directly to a computer.

2.3.3 Cabling

ENC28J60 supports 10BASE-T transmission which means 10 Mbps of data

transfer rate. BASE is short for baseband, meaning that there is no frequency-division

multiplexing (FDM) or other frequency shifting modulation in use i.e. each signal has

full control of wire, on a single frequency. T designates twisted pair cable, where the

pairs of wires are twisted together for purposes of reducing crosstalk

The cabling used for the transmission uses

8 position modular connectors (shown in figure

2.9), usually called RJ-45 in the context of Ethernet

over twisted pair. The cables usually used are four-

pair or above twisted pair cable. This standard

supports both full-duplex and half-duplex

communication. According to the standards, this

operates over distances of 'up to 100 meters'.

To connect two computers directly together without a switch, an Ethernet crossover

cable is often used. Two pair crossover cable pin outs are shown in the table 1. This

table shows the connection at both the ends of the cable. This constraint can be

removed by using the AutoMDIX feature of a RJ 45 Jack.


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Table 1: Two pair crossover cable pin outs

2.1.4 SPI (Serial Peripheral Interface)

2.1.4.1 Overview

An ATmega 32 Microcontroller uses SPI (Serial Peripheral Interface) to

effectively communicate with the Ethernet controller ENC28J60. The usage of SPI

provides serial communication thus eliminating large number of lines used for data

and addressing purpose. The SPI allows high-speed synchronous data transfer

between the AVR and peripheral devices or between several AVR devices. On most

parts the SPI has a second purpose where it is used for In System Programming (ISP).

The interconnection between two SPI devices always happens between a

master device and a slave device. Compared to some peripheral devices like sensors

which can only run in slave mode, the SPI of the AVR can be configured for both

master and slave mode. The mode the AVR is running in is specified by the settings

of the master bit (MSTR) in the SPI control register (SPCR). Special considerations

about the SS pin have to be taken into account.


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The master is the active part in this system and has to provide the clock signal a serial

data transmission is based on. The slave is not capable of generating the clock signal

and thus can not get active on its own. The slave just sends and receives data if the

master generates the necessary clock signal. The master however generates the clock

signal only while sending data. That means that the master has to send data to the

slave to read data from the slave.

2.1.4.2 Data transmission between Master and Slave

The interaction between a master and a slave AVR is shown in the figure 2.10

Fig 2.10: Interaction between different devices supporting SPI

Two identical SPI units are displayed. The left unit is configured as master

while the right unit is configured as slave. The MISO, MOSI and SCK lines are

connected with the corresponding lines of the other part. The mode in which a part is

running determines if they are input or output signal lines. Because a bit is shifted

from the master to the slave and from the slave to the master simultaneously in one

clock cycle both 8-bit shift registers can be considered as one 16-bit circular shift

register. This means that after eight SCK clock pulses the data between master and

slave will be exchanged. The system is single buffered in the transmit direction and

double buffered in the receive direction.


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This influences the data handling in the following ways:

1. New bytes to be sent can not be written to the data register (SPDR) / shift register

before the entire shift cycle is completed.

2. Received bytes are written to the Receive Buffer immediately after the transmission

is completed.

3. The Receive Buffer has to be read before the next transmission is completed or data

will be lost.

4. Reading the SPDR will return the data of the Receive Buffer.

After a transfer is completed the SPI Interrupt Flag (SPIF) will be set in the SPI Status

Register (SPSR). This will cause the corresponding interrupt to be executed if this

interrupt and the global interrupts are enabled. Setting the SPI Interrupt Enable (SPIE)

bit in the SPCR enables the interrupt of the SPI while setting the I bit in the SREG

enables the global interrupts.

2.1.4.3 Pins of the SPI

The SPI consists of four different signal lines. These lines are the shift clock

(SCK), the Master Out Slave In line (MOSI), the Master In Slave Out line (MISO)

and the active low Slave Selectline (SS). When the SPI is enabled, the data direction

of the MOSI, MISO, SCK and SS pins are overridden according to the following table

2.

Table 2: SPI pins of ATmega32 Microcontroller


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2.1.5 Miscellaneous Components:

2.1.5.1 LM 7805 IC

LM7805 is a three-terminal positive voltage regulator employ built-in current

limiting, thermal shutdown, and safe-operating area protection which makes them

virtually immune to damage from output overloads. Here we use LM 7805 for getting

an output of 5V required by ATmega32 Microcontroller. Figure 2.11 shows the pin

layout of LM7805 IC.

Fig 2.11: Pins of LM 7805

2.1.5.2 LM 317 IC

LM317 is an adjustable 3-terminal positive voltage regulator capable of

supplying in excess of 1.5A over a 1.2V to 37V output range. They are exceptionally

easy to use and require only two external resistors to set the output voltage. Further,

both line and load regulation is better than standard fixed regulators. Here we use LM

317 voltage regulator for getting an output of 3.3 V required by ENC28J60 IC. .

Figure 2.12 shows the pin layout of LM317 IC.

Fig 2.12: Pins of LM 317


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2.1.5.3 JHD-162A LCD Display

An LCD display offers high flexibility to user to display the required data on

it. It may be also used for debugging purpose of the program i.e. by checking which

all subroutines are executed by displaying the value on LCD display. In our case a

16x2 alphanumeric LCD display is used to display the current AVR IP, the ADC

value (if connected) and temperature. An LCD driver is a link between the

microcontroller and LCD. The JHD 162A LCD display uses driver HD44780U. The

header file included in the program depends upon the LCD display driver used.

Figure 2.13 shows a JHD 162A LCD display

Fig 2.13: JHD 162A LCD display


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2.1.6 Interfacing of Different Components

The following figure shows the main interfacing of AVR web server:

Fig 2.14: AVR Web Server Interfacing


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2.2 Networking

Before we can actually write a program for ATmega32 microcontroller we

must have knowledge about TCP/IP protocol stack, Ethernet frame structure, Web

browser protocol (HTTP) etc. We will discuss these one by one in this section.

2.2.1 TCP/IP Protocol Suite

The TCP/IP protocol suite allows computers of all sizes, running different

operating systems, to communicate with each other. It forms the basis for what is

called the worldwide Internet, a Wide Area Network (WAN) of several million

computers.

TCP/IP Suite Layers: The TCP/IP protocol suite is a combination of different

protocols at various layers. TCP/IP is normally considered to be a 4-layer system as

shown in figure below (fig. 2.15).

. Fig 2.15: TCP/IP protocol stack

2.2.1.1 Application Layer

The Application layer handles the details of a particular application. Common

TCP/IP applications include:

• Telnet for remote login

• Browser support for displaying web pages

• File transfer applications

• E-mail applications


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The three lower layers do not know anything about the specific application and only

take care of communications details.

2.2.1.2 Transport Layer

TCP is responsible for a reliable flow of data between two hosts. Typically,

TCP divides data passed to it from the application into appropriately sized chunks for

the network layer below, acknowledging received packets that are sent and

retransmits lost packets. Since this reliable, flow of data is provided by the Transport

Layer, the Application Layer above can ignore these details.

UDP is a much simpler service to the Application Layer. It sends packets of

data called datagrams from one host to the other, but with no guarantee that the

datagrams reach the other end. Desired reliability must be added by the application

Layer.

2.2.1.3 Network Layer

This layer is sometimes called the Internet Layer. It handles the movements of

packets around the network. Routing of packets, for example, takes place here. IP

(Internet Protocol) and ICMP (Internet Control Message Protocol) provides the

Network Layer in the TCP/IP Protocol Suite.

2.2.1.4 Link Layer

Data-link or Network Interface Layer is another common name of this layer.

The Link Layer normally includes the device driver in the operating system and the

corresponding network interface (card) in the computer. Together they handle all the

hardware details of physically interfacing with the cable.

2.2.2 Combining all


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Figure 2.16 shows an example that includes two hosts on a Local Area Network

(LAN) such as Ethernet, using HTTP.

Fig 2.16: Example of various protocols involved

One side represents the client, and the other the server. The server provides

some type of service to clients, in this case, access to web pages on the server host.

Each layer has one or more protocols for communicating with its peer at the same

layer. One protocol, for example, allows the two TCP layers to communicate, and

another protocol lets the two IP layers communicate.

The Application Layer is normally a user-process while the lower three layers

are usually implemented in the kernel (the operating system).


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2.2.3 Port Numbers

Different applications can use TCP or UDP at any time. The Transport layer

protocols store an identifier in the headers they generate to identify the application.

Both TCP and UDP use 16-bit port numbers to identify applications. TCP and UDP

store the source port number and the destination port number in those respective

headers. Servers are normally known by their well-known port number. Every TCP/IP

implementation with a FTP server provides that service on TCP port 21. Every Telnet

server is on TCP port 23. Services provided by any implementation of TCP/IP have

well-known port numbers between 1 and 1023. The well-known ports are managed by

the Internet Assigned Numbers Authority (IANA).

The combination of an IP address and a port number is called a socket.

2.2.4 Encapsulation

When an application sends data using TCP, the data is sent down the protocol

stack, through each layer, until it is sent as a stream of bits across the network. Each

layer adds information to the data by prepending headers and adding trailers to the

data it receives. Figure 2.17 shows this process.

Some abbreviations:

• TCP segment: The unit of data that TCP sends to IP.

• IP datagram: The unit of data that IP sends to the network interface.

• Frame: The stream of bits that flows across the Ethernet.

IP (Internet Protocol) adds an identifier to the IP header it generates to indicate

which layer the data belongs to. IP handles this by storing an 8-bit value in its header

called the protocol field. Similarly, many different applications can be using TCP or

UDP at any time. The Transport Layer protocol stores an identifier in the header they

generate to identify the application. Both TCP and UDP use 16-bit port numbers to

identify applications.


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Fig 2.17: Encapsulation of data as it goes down the protocol stack

The TCP and UDP store the source port number and the destination port

number in their respective headers. The network interface sends and receives frames

on behalf of IP, ARP, RARP. There must be some form of identification in the

Ethernet header indicating which network layer protocol generates the data. To handle

this, there is a 16- bit frame type field in the Ethernet header.

2.2.5 Internet Addresses

Every interface on the internet has a unique Internet Address (IP Address).

The addresses are 32-bit numbers. Following figure 2.18 shows the structure and the

five different classes of Internet addresses:


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Fig 2.18: Five different classes of internet addresses

The 32-bit addresses are normally written as four decimal numbers, one for

each byte of the address. This notation is called dotted-decimal. Since every interface

on internet must have a unique IP address, there must be one central authority for

allocating these addresses for networks connected to the worldwide Internet. Internet

Network Information Center (NIC) is the responsible authority. Table 3 gives the

dotted decimal notation of classes of IP.

Table 3: Classes of IP


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2.2.6 IP (Internet Protocol)

All TCP, UDP and ICMP data get transmitted as IP datagrams. IP provides an

unreliable, connectionless datagram delivery service. There is no guarantee that an IP

datagram successfully gets to its destination. When something goes wrong, IP has a

simple error handling algorithm: Throw away datagram and try to send an ICMP

message back to the source. Any required reliability must be provided by the upper

layers.

2.2.6.1 IP Header

Figure 2.19 shows the format of an IP datagram. The normal size of the IP

header is 20 bytes, unless options are present. The most significant bit is numbered 0

at the left, and the least significant bit of a 32-bit value is numbered 31 on the right.

The 4 bytes in the 32-bit value are transmitted in the order: bits 0 - 7, then bits 8 - 15

and so on. This is called Big-Endian byte ordering, which is the byte ordering

required for all binary integers in the TCP/IP headers as they traverse a network. This

is called the network byte order.

Fig 2.19: IP headers fields

Header length:

The header length is the number of 32-bit words (4 bytes per word) in the header,

including any options. This limits the header length to 60 bytes.


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Type of Service (TOS):

The field, (TOS) is composed of a 32-bit precedence field (which is currently

ignored), 4 TOS bits, and an unused bit that must be 0. The 4 TOS bits are: minimize

delay, maximize throughput, maximize reliability and minimize monetary cost. Only

1 of these bits can be turned on. If all 4 bits are 0, it implies normal service.

Total Length:

This is the total length of the IP datagram in bytes. Using this field and the header

length field, we know where the data portion of the IP datagram starts and its length.

Since this is a 16-bit field, the maximum size of an IP datagram is 65535 bytes.

Identification:

This field uniquely identifies each datagram sent by a host. It normally increments by

One each time a datagram is sent.

Time To Live:

Time-to-live sets an upper limit on the number of routers through which datagram can

pass. It limits the lifetime of the datagram. It is initialized by the sender to some value

(often 32 or 64) and decrements by one in every router that handles the datagram.

Then this field reaches 0, the datagram is discarded, and the sender is notified with an

ICMP message. This prevents the packet from getting caught in eternal routing loops.

Protocol:

Protocol is used by IP to demultiplex incoming datagrams. It identifies which protocol

gave the data for IP to send.

Header Checksum :

The Header checksum is calculated over the IP header only. It does not cover any data

that follows the header. ICMP, UDP and TCP all have a checksum in their own

headers to cover their own header and data. Every IP datagram contains the source IP

address and the destination IP address. These are 32-bit values.


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The Option Field:

This is a variable-length list of optional information for the datagrams. The options

are rarely used and not all hosts and routers support the option.

2.2.7 TCP (Transmission Control Protocol)

TCP and UDP use the same network layer (IP), but TCP provides a totally

different service to the Application Layer. TCP provides a connection-oriented,

reliable, byte stream service. The term connection-oriented means the two

applications using TCP must establish a TCP connection with each other before they

can exchange data.

TCP provides reliability by doing the following:

• The application data is broken into what TCP considers the best sized chunks to

send. This is totally different from UDP, where each write by the application generate

a UDP datagram of that size. The unit of information passed by TCP to IP is called a

segment.

• When TCP sends a segment it maintains a timer, waiting for the other end to

acknowledge reception of the segment. If an acknowledge is not received in time, the

segment is retransmitted.

• When TCP receives data from the other end of the connection, it sends an

acknowledgment. This acknowledgment is not sent immediately, but normally

delayed a fraction of a second.

• TCP maintains a checksum on its data header page. This is an end-to-end checksum

whose purpose is to detect any modifications of the data in transit. If a segment

arrives with an invalid checksum, TCP discards it and does not acknowledge

receiving it. This expects the sender to time out and retransmits.


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• Since TCP segments are transmitted as IP datagrams, and since IP datagrams can

arrive out of order, TCP segments can also arrive out of order. A receiving TCP

resequences the data if necessary, passing the received data in the correct order to the

application.

• Since IP datagrams can get duplicated, a receiving TCP must discard duplicate data.

• TCP also provides flow control. Each end of a TCP connection has a finite amount

of buffer space. A receiving TCP only allows the other end to send as much data as

the receiver has buffer for. This prevents a fast host from taking the entire buffer on a

slower host.

TCP data is encapsulated in an IP datagram, as shown in fig 2.20

Fig 2.20: Encapsulation of TCP data in IP datagram

2.2.7.1 TCP Header

Figure 2.21 shows the format of the TCP header. Its normal size is 20 bytes, unless

options are present.

Sequence Number:

This identifies the byte stream of data from the sending TCP to the receiving TCP that

the first byte of data in this segment represents. TCP numbers each byte with a

sequence number. The sequence number is a 32-bit unsigned number that wraps back

around to 0 after reaching 232-1.


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Fig 2.21: TCP header fields

Acknowledge Number:

This contains the next sequence number that the sender of the acknowledgment

expects to receive. This is therefore the sequence number plus 1 of the last

successfully received byte of data. This field is only valid if the ACK flag is set. The

32-bit acknowledgment number field is always part of the header, as is the ACK flag.

This field is always set and the ACK FLAG is on.

Header Length:

This gives the length of the header in 32-bit words. This is required because the length

of the options field is variable. With a 4-bit field, TCP is limited to a 60-byte header.

Without options, however, the normal size is 20 bytes.

Flag Bits:

There are six flag bits in the TCP header – one or more of them can be turned on at

the same time:

1. URG – The urgent pointer is valid.

2. ACK – The acknowledgment number is valid.

3. PSH – The receiver should pass data to the application as soon as possible.

4. RST – Reset the connection.

5. SYN – Synchronize sequence numbers to initiate a connection.

6. FIN – the sender is finished sending data.


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Window Size:

TCP’s flow control is provided by each end advertising a window’s size. This is the

number of bytes, starting with the one specified by the acknowledgment number field,

that the receiver is willing to accept. This is a 16-bit field, limiting the window to

65535 bytes.

Checksum:

Checksum covers the TCP segment: the TCP header and the TCP data. This is a

mandatory field and must be calculated and stored by the sender and then verified by

the receiver.

Urgent Pointer:

The urgent pointer is valid only if the URG flag is set. This pointer is a positive offset

that must be added to the sequence number field of the segment to yield the segment

number of the last byte of urgent data. TCP’s urgent mode is a way for the sender to

transmit emergency data to the other end.

Checksum:

The most common option field is the MSS (maximum segment size). Each end of a

connection normally specifies this option on the first segment exchanged (the one sent

with the SYN flag set to establish the connection). It specifies the maximum size

segment that the sender wants to receive.

Data:

The data portion of the TCP header is optional. A header without data is used to

acknowledge received data if there is no data to be transmitted in that direction. There

are also some cases dealing with time-outs when a segment can be sent without any

data.


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2.2.8 Ethernet Encapsulation

Ethernet encapsulation is performed before sending the IP datagram over the

transmission lines. A typical Ethernet frame looks like as in fig. 2.22:

Fig 2.22: Ethernet Encapsulation

Some of its fields are:

Destination Address:

This field contains the 48-bit destination MAC address.

Source Address:

This field contains the 48-bit source MAC address.

Ethernet Type:

Identifies the type of data that follows.


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CRC:

Cyclic redundancy checksum used to detects errors in the rest of the frame.

Preamble:

The Ethernet frame begins with 8 byte preamble field to synchronize the sender’s

clock with the receiver clock.

Minimum Size:

For an Ethernet frame it is 46 bytes. To handle this, pad bytes are inserted to assure

that the frame is sufficiently large

2.2.9 HTTP (Hyper Text Transfer Protocol)

The HTTP protocol is a protocol that allows a (web) client to request files or

other resources from a server. Various types of requests can be sent by the client. The

most basic are the “GET” request and the “POST” request which are used to fetch and

post data, respectively. The server processes the request, returns a header containing a

status code and either a file or an HTML document attached after the header. Finally,

the server closes the connection.

2.2.9.1 HTTP Message

An HTTP message consists of requests from client to server and responses

from server to client. The message format is similar in many ways to that used by

Internet Mail and the Multipurpose Internet Mail Extension (MIME) as defined in

RFC 822 and RFC 1521.

HTTP Request Message

A request message consists of a request-line followed by some header-lines

specifying the request. Example (POST) request is shown in figure 2.23.


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HTTP Response Message

The response message consists of a response-line followed by header-lines and the

entity body. The entity body is separated from the headers by a null line. Example of

(GET) response is shown in figure 2.24:

Fig 2.23: Example POST request

Fig 2.24: HTTP response message

2.2.9.2 HTTP Methods

The first word in the request line is the name of the method to be executed.

The common methods are listed in table 4.

2.2.9.3 Status Codes

Every request gets a response starting with a status line. The status line consists of the

protocol version followed by a numeric status code and its associated textual phrase.


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The common HTTP/1.0 status codes are listed in table 5.

Table 4: HTTP Methods

Table 5: HTTP status code


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2.3 Software Packages

In this section we will discuss in brief about the software packages used in the

project. The software packages used in the project are:

WinAVR

AVR Studio

PonyProg

2.3.1 WinAVR

WinAVR (pronounced "whenever") is a suite of executable, open source

software development tools for the Atmel AVR series of RISC microprocessors

hosted on the Windows platform. It includes the GNU GCC compiler for C and C++.

It provides libraries for various inbuilt functions.

WinAVR contains all the tools for developing of an AVR application. This

includes Programmers Notepad (editor), avr-gcc (compiler), avrdude (programmer),

avr-gdb (debugger).

2.3.2 AVR Studio version 4

AVR Studio 4 is the new professional Integrated Development Environment

(IDE) for writing and debugging AVR applications in Windows 9x/NT/2000/XP

environments. It provides a C compiler, assembler and Simulator.

2.3.3 PonyProg

A software Programmer is a program which sends the hex code generated

from the compiler/assembler to the microcontroller via Serial/Parallel/USB port link.


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A hardware programmer is a circuit used to interface Microcontroller with the

Computer to burn the hex code from the computer onto the microcontroller.

PonyProg is a serial device programmer software with a user friendly GUI

framework available for Windows95/98/ME/NT/2000/XP and Intel Linux. Its purpose

is reading and writing every serial device. At the moment it supports I²C Bus,

Microwire, SPI eeprom, the Atmel AVR and Microchip PIC micro.


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CHAPTER 3

SOFTWARE CODE

3.1 Header Files

The header files are written by declaring the necessary Macros and Function

into a file ending with .h extension. The real definition of the function appears in the

C program with the same file name as header file but ending with .C extension.

Most of the header files are obtained under GNU general public license and are

rewritten for our convenience. Some of these headers files are discussed here:

3.1.1 enc28j60.h

It provides the driver for ENC28J60 IC. Some of the functions defined in this

header file are:

enc28j60_init (): Used to initialize ENC28J60.

enc28j60_packet_send (): Send packet to network.

enc28j60_tx_checksum (): It adds the checksum calculated to the packet to be

send.

enc28j60_packet_receive (): check received packet and return length of data

3.1.2 arp.h

ARP (Address Resolution Protocol) is the method for finding a host's

hardware address when only its network layer address is known. Some of the

functions written in it are:


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arp_generate_packet (): Used for generating an arp packet.

arp_send_request (): Used for sending an arp request packet. It calls function

arp_generate_packet.

arp_send_reply (): Send reply if recieved packet is ARP and IP address is

match with avr_ip

arp_packet_is_arp (): check received packet, that packet is match with arp and

avr ip or not?

arp_who_is(): send arp request to destination ip, and save destination MAC to

dest_mac.

3.1.3 ip.h

This function implements basic IP protocol. Some of the functions provided

by this header file are:

ip_packet_is_ip (): It checks whether a received packet is an IP packet or not.

ip_generate_header (): It generates all IP headers.

3.1.4 tcp.h

Used to implement basic TCP protocol. Some of functions defined in this

header file are:

tcp_get_dlength ( ): It calculates the data length of the received tcp segment.

tcp_get_hlength ( ): It calculates the header length of the received tcp segment.


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tcp_puts_data_p ( ): It puts data from program memory to tx buffer.

tcp_puts_data (): It puts data from Atmega32 RAM to tx buffer of ENC28J60.

tcp_send_packet (): It sends the tcp packet to the network.

3.1.5 http.h

This header file implements basic http protocol.

Some of the global values declared are:

web_title[] = "AVR Web Server";

tag_br[] = "<br>";

tag_hr[] = "<hr width=\"100%\" size=\"1\"><br>";

tag_form[] = "<form action=\"./?\" method=\"get\">";

Some of the functions declared in this header file are:

http_webserver_process(): Used for initial connection to web server.

http_get_ip(): Used for getting the IP address from the buffer.

http_get_variable(): Used to get http variable from ‘GET’ method.

hex2int (): Used to convert hexadecimal number into integer number.

urldecode (): Used to decode the URL by separating characters like % or +.

http_put_request (): Used to put http put request.


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http_home (): It prepares the web page by writing the HTML data to the TCP

send buffer.

3.1.6 menu.h

This header file implements Menu structure used in 16x2 LCD display.

Functions defined in this header file are:

my_strcpy(): copy string (end '\0') from program memory to ram and return

pointer to end of string.

print_decimal(): Print decimal to buffer, up to 5 digits.

print_temp(): Print ADC0 and temparature to buffer.

print_ip(): Print ip address format to buffer e.g. 10.1.1.1

standby_display(): Display board status such as AVR ip, server IP,

temperature etc.

menu_init(): Used to initialize the Menu.

display_menu(): Display LCD user interface menu on LCD.

menu_process(): Used to process the menu using the up and down keys.

Following are the functions related to the two keys:

a) key_up_process (): Used to move up in the menu.

b) key_dw_process(): Used to move down the menu.


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3.1.7 main.h

This is the main header file where the infinite loop is implemented. It also has

some function defined as Server Process which is called by main loop. The infinite

loop is implemented as:

for(;;)

{ // wait until timer1 overflow

while ( (TIFR & _BV ( TOV1 )) == 0 );

TIFR |= _BV(TOV1);

TCNT1 = 1536; // Timer1 overflow every 1/16MHz * ( 65536 -

1536 ) = 4ms, 250Hz

time_base (); // general time base, generate by timer1

adc_read_temp(); // read temperature

server_process (); // server process response for arp, icmp, http

menu_process (); // lcd user interface menu

standby_display (); // display AVR ethernet status

}

return 0;

}

Here since the AVR is clocked at 16 MHz and the counter is set to count downward

from 65536 to 1536, this loops runs at 250 Hz (or 4 ms).


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CHAPTER 4

EXECUTION

This section deals with the testing, debugging and execution of the program.

The program is written based on the header files which we have discussed in the

previous section.

4.1 Testing and Debugging

All the codes were written on AVR Studio (refer Appendix 1). Each of the

function was independently tested with the set of inputs and was simulated by inbuilt

Simulator of AVR Studio. After integration of all the functions a sample input was

provided to check the output. Also in between code LCD display messages were

provided so as to perform debugging through LDC display.

The project is tested with different versions of browsers running on different

operating systems. All browsers supporting HTTP V1.0 are able to communicate with

the Microcontroller. And through the interface of the web page devices were

controlled.

4.2 Procedure for Execution:

When the whole software code is written in C in AVR Studio environment,

the output hex file is transferred to the Microcontroller with the help of

PonyProg(refer appendix 1, 2 and 3).

Now plug one of the RJ 45 connector of the cross over cable to the RJ 45 jack

of AVR web server and the other end connector to the RJ 45 Jack of CPU. Manually

configure the Internet Connection. If the AVR IP is set to 10.1.1.1, then type this

address in the address bar of the web browser and hit enter. After a short period of

time a web page will be displayed which shows the current status of the devices


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attached to the microcontroller. Now through the interface of this web page devices

attached to the microcontroller can be controlled.

Following is one of the screenshot of the web page:

Fig 4.1: AVR web server screen shot


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CHAPTER 5

CONCLUSION

The project on “AVR Microcontroller based Web Server” has been developed

which hosts a small web page. The web page is stored onto the ATmega32 Flash

memory.

Through the interface of the web page a user is able to control the devices

remotely. A user can also monitor the devices remotely by embedding each device to

be controlled or monitored with the AVR web server. Each device now has a separate

IP address assigned to it. When the IP address is type onto the address bar of the web

browser the web page associated with that device get opens.

The Project can be further developed to provide interfacing with SD/MMC

cards or an IDE hard disk, so that a user can also upload files onto this web server

through the web page interface. In a similar way the Microcontroller can be interfaced

with a Camera and can be used for Remote Surveillance through web page.


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REFERENCES

[1] Atmel ATmega32 Datasheet, Atmel Corporation. www.atmel.com/dyn/resources/prod_documents/doc2503.pdf [2] AVR 460 Application Note, Atmel Corporation. www.atmel.com/atmel/acrobat/doc2396.pdf [3] Berners-Lee, Fielding, T.R. Irvine, H. UC, Frystyk. Request for

Comment:1945, May 1996. http://www.faqs.org/rfcs/rfc1945.html [4] ENC28J60 Datasheet, Microchip Technology Inc. http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en022889 [5] Gary Desrosiers,99. Embedded Ethernet. http://www.embeddedethernet.com/ [6] Postel, Jon, Information Science Institute. University of Southern California.,

Network Working Group, Request for Comment: 791, September 1981. http://www.faqs.org/rfcs/rfc791.html [7] Postel, Jon, Information Science Institute. University of Southern California.,

Network Working Group, Request for Comment: 792, April 1984 http://www.faqs.org/rfcs/rfc792.html [8] Plummer, David C., Network Working Group. Request for Comment: 826,

November 1982. http://www.faqs.org/rfcs/rfc826.html


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Appendices

Appendix 1

Working with AVR Studio:

Perform the installation of WinAVR before installing AVR Studio. It helps in locating

the libraries by AVR Studio.

Step1: Open AVR Studio and Select New Project

Fig 7.1: Select New Project in AVR Studio

Step 2: Select AVR GCC compiler and enter a name for the project


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Fig 7.2: Select AVR GCC in AVR Studio

Step 3: Select AVR Simulator and device to be used (here ATmega32)

Fig 7.3: Select Microcontroller type


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Step 4: Start writing your program

Fig 7.4: Write the program in the editor

Step 5: Goto Build and click Build

When the build is successful a build successful message is shown otherwise any error

occurred is reported.

If the build is successful a hex file of the above code is generated in a directory called

‘Default’ where the project is saved. Now transfer this hex file to the Microcontroller.


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Appendix 2

Transfering Code to the Micrcontroller (Using PonyProg)

Step 1: Open PonyProg and goto Interface setup

Fig 7.5: Setup the interface of PonyProg

Step2: Make the settings depending upon your hardware programmer type

Fig 7.6: Select the appropiate hardware programmer type


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Step 3: Click on “Setup” menu and click on “Calibration”, click Yes to Calibrate.

Step5: Click on “Security and Configuration Bits”. Click on read, make the

appropriate changes depending upon the Oscillator used. Here we are using external

16 MHz crystal. Click on write after the changes are done.

Fig 7.7: Write appropriate configuration bits

Step 6: Open the hex file generated by AVR studio and click on “Write All” under

“Command” tab, then click yes.

Fig 7.8: Burn the code onto the Microcontroller


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If a write successful message appears, then the Code was successfully written onto the

microcontroller.

If an error like this appears

Fig 7.9: Error message of PonyProg

Then following possibilities are there:

Power supply is not ON.

Length of the programming cable is too large

Programmer Circuit is not correctly implemented

Problem with the CPU parallel port or serial port

Otherwise, the Microcontroller used is dead.


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Appendix 3

Programmer Hardware:

A simple hardware programmer for AVR microcontroller using parallel port is shown

here. There are several other programmer hardware circuit available using Serial and

USB port, but using Parallel Port is the easiest one.

Fig 7.10: Parallel Port Programmer Hardware

The length of the wire to target should not exceed more than 20 cm, otherwise the

SCK line starts oscillating and there would be no synchronization between the

Microcontroller and the CPU


avr web server

Documents

avr web server

web serverdone

implementation of web

small web page

techincomputer science

engineering studiescochin

vinod kumar

user interface