i

Abstract

This report includes the first and second chapters of the final project report on Digital

Communication and Computer Networking Embedded Systems designing.

The first chapter consists of an introduction to the project. The basic review about the project and

main steps which will be carried out to solve the problem is also embodied in it. Furthermore it

describes the resources and required tentative budget.

The second chapter of this report includes the progress of the project and the theoretical

knowledge and the practical experiences we have achieved during the works. This chapter

consists of the designing of the module with details step to step.

ii

Preface

Remote accessing for non pc devices is can be found very beneficial as it can be used to remote

monitoring and remote controlling the device. But at the same time it can be found difficult as

they havent any inbuilt structure which is supporting for networking capability. This would be

rather straitened task for non pc devices which are not having RS 232 interfaces. But some non

pc devices are coming with RS 232 interfaces which are used to controlling and modifying

functions.

This report points out the necessity of an external device which will functioning as a networking

enable device on behalf of non pc devices and a brief analysis in designing of such a product and

its feasibilities. The next chapter discusses about designing of an external module using sbc65ec

microchip. It consists of necessary steps and commands.

iii

Acknowledgements

As an undergraduate, completing a final year project successfully will be a great pleasure. It will

be a great opportunity to gather practical experience in industry.

Therefore firstly our sincere gratitude must be goes to Dr.Jayasundare for guiding us as our

supervisor and also for Mr.U.N.Weerapperuma as the core supervisor of our project in

conducting us with his busy daily routine.

Then our gratitude must be extended to Dr. K.Gunawickrama, final year project coordinator for

offering this great opportunity in completing an undergraduate project.

Also our sincere gratitude must be extended to Dr. P. D. C.Perera for valuable assistance in

accomplishing our project goals.

Also we would be fond of extend our praise for colleagues for their encouragement.

Finally, all the mentioned & unmentioned people who contribute to complete my training

successfully are sincerely appreciated and thanked.

iv

Contents

Preface ...................................................................................................................................... ii

Acknowledgements .................................................................................................................. iii

Contents ................................................................................................................................... iv

Acronyms ................................................................................................................................. vi

List of Tables ......................................................................................................................... viii

List of Figures.......................................................................................................................... ix

Chapter 01 .................................................................................................................................1

Introduction .............................................................................................................................1

1.1 Background of the problem ................................................................................................1

1.2 Problem Statement .............................................................................................................3

1.3 Objectives and scope .........................................................................................................3

1.4 Research Methodology ......................................................................................................5

1.5 Resources required and tentative budget ............................................................................6

1.6 Time plan ..........................................................................................................................7

Chapter 02 .................................................................................................................................8

2.1 Selecting the chip and advantageous ..................................................................................8

2.1.1 Features .......................................................................................................................8

2.1.2 Main components of the module ..................................................................................9

2.2 The steps of the project up to the first progress ................................................................ 12

2.2.1 Testing the module .................................................................................................... 12

2.2.2 Configure the web server step1 .................................................................................. 15

2.3 Testing the program ......................................................................................................... 18

2.4 Selecting a non-pc device................................................................................................. 18

2.4.1 Universal Asynchronous Receiver/Transmitter (UART) ............................................ 20

2.4.2 The components used for built the power meter ......................................................... 21

2.4.3 Ratings ...................................................................................................................... 22

2.4.4 Measuring the voltage of single phase power line ...................................................... 23

2.5 Development of the database and web applications .......................................................... 25

v

2.5.1 Mysql database .......................................................................................................... 26

2.5.2 Php code in web client ............................................................................................... 27

2.5.4 Web pages ................................................................................................................. 28

2.6 Results ............................................................................................................................. 30

Chapter 3 ................................................................................................................................. 34

3.1 Conclusions ..................................................................................................................... 34

3.1.1 Future Development .................................................................................................. 35

References................................................................................................................................ 37

Appendix A .............................................................................................................................. 38

Part1: Developing firmware ................................................................................................... 38

1.1 HTTPEXEC.C ............................................................................................................. 38

1.2 HTTP.C ....................................................................................................................... 39

1.3 CMD.C ........................................................................................................................ 40

Part 2: C program code of power monitoring device .............................................................. 44

Appendix B .............................................................................................................................. 46

B.1 Serial data transmission [13]

.............................................................................................. 46

B.1.1 Asynchronous and Synchronous Communications .................................................... 46

B.1.2 Bit Rate and Baud Rate ............................................................................................. 48

B.1.3 Word Formats ........................................................................................................... 48

B.1.4 Sending Bits ............................................................................................................. 48

B.2 COM PORT configuration on PC .................................................................................... 50

vi

Acronyms

ASCII

American Standard Code for Information Interchange

HTML Hyper-Text Markup Language

HTTP Hyper-Text Transfer Protocol

IC Integrated Circuit

ICSP In-Circuit Serial Programming

IDE Integrated Development Environment

IEEE Institute of Electrical and Electronics Engineers

IP Internet Protocol

ISO International Standards Organization

MCC16 Microchip C compiler for 16 series PICs

MCU Microcontroller Unit

NIC Network Interface Controller

OSI Open Systems Interconnect

RFC Request for comments

RM Reference Model

RX Receive / Receiver

SPI Serial Peripheral Interface

TCP Transmission Control Protocol

TX Transmit / Transmitter

ESDNC Embedded serial data-network converter

vii

LAN Local Area Network

FTP File Transfer Protocol

ICMP Internet Control Message Protocol

TFTP Trivial File Transfer Protocol

SMTP Simple Mail Transfer Protocol

POP3 Post Office Protocol version 3

API Application programming Interface

ICSP In-Circuit Serial Programming

IDE Integrated Development Environment

ICD In-Circuit Debugging

PIC Peripheral Interface Controllers

RFC Request for comments

TCP Transfer Control Protocol

UDP User Datagram Protocol

HTTP Hyper Text Transfer Protocol

BMS Building Management System

viii

List of Tables

Table 1.1: Resources required and tentative budget ... 5

Table 1.2: Time plan for the project..7

ix

List of Figures Figure 1.1: Local area network of an industrial environment .......................................................2

Figure 1.2: implementing the embedded system converter in the industrial LAN .........................3

Figure 2.1: SBC65EC Module .....................................................................................................9

Figure 2.2: The testing environment .......................................................................................... 12

Figure 2.3: Setting up the parameters of the HyperTerminal of PC A ........................................ 13

Figure 2.4: Sending characters from Hyperterminal ................................................................... 14

Figure 2.5: Capturing the data packets from Wireshark ............................................................. 14

Figure 2.6: Embedded system converter .................................................................................... 15

Figure 2.7: The Network Bootloader ......................................................................................... 16

Figure 2.8: The newly designed web page ................................................................................. 17

Figure 2.9: Testing the program ................................................................................................ 18

Figure 2.10: Circuit diagram of the power meter ....................................................................... 19

Figure 2.11: Implemented power meter ..................................................................................... 22

Figure 2.12: Block diagram of the voltage measuring process of the single phase power line .... 23

Figure 2.13: Circuit diagram for the connectivity of the transformers ........................................ 24

Figure 2.14: Power monitoring from remote computer .............................................................. 25

Figure 2.15: Deploying database/web server ............................................................................. 26

Figure 2.16: Mysql database ...................................................................................................... 26

Figure 2.17: Home Page ............................................................................................................ 28

Figure 2.18: Data displaying page ............................................................................................. 29

Figure 2.19: Contact Page ......................................................................................................... 29

Figure 2.20: Data received from the power meter ...................................................................... 30

Figure 2.21: Real time power measured by the power meter ...................................................... 31

Figure 2.22: Data capturing of Wireshark .................................................................................. 31

Figure 2.24: Retrieved data from the Mysql database ................................................................ 33

Figure 2.25: Monitoring the power consumption through the web ............................................. 33

Figure 3.1: Power monitoring system of the Department of Electrical & Information

Engineering ............................................................................................................................... 35

Figure B.1: Synchronous transmission ...................................................................................... 47

Figure B.2: Asynchronous transmission .................................................................................... 47

Figure B.3: To determine when to send data and read received data, the transmitter and receiver

each use a clock that is typically 16 times the bit rate ................................................................ 49

Figure B.4: COM Port Properties .............................................................................................. 51

Figure B.5: Set the COM1 Properties ........................................................................................ 52

1

Chapter 01

Introduction

Generally computers are independent units and they cannot exchange information with

other computers near or far without having a special technique. But these computers have local

interfaces such as USB or RS-232 to communicate with printers or other devices close at hand.

Networking technology is a popular way, used in homes, offices and factories which

allow sharing resources and information efficiently among interconnected PCs and devices.

Without such a networking property exchanging information will become more complicated and

time consuming. Now even network security became more significant providing confidentiality

for transmitting data with networking techniques.

Remote access is one of an advantage in networking computers. Remote access allows

accessing to PCs, files from any Internet-connected computer in the world. Remote access can be

developed in LANs (Local Area Network) and also through Internet. Developing such an

application in system is more advantageous for remote monitoring and remote controlling. This

project is developing an embedded system module (Ethernet data- Serial data converter) for

remote monitoring purpose.

1.1 Background of the problem

Nowadays networking computers has become a necessity for exchanging data among a

set of computers. Generally networking computers in a small area (ex: within an organization) is

referred as a LAN. LANs can be connecting to the internet through a router as it has the ability to

facilitate the routing capability for data. Within a LAN the data exchanging is done by using

Ethernet technology. The terms such as Switches, CSMA/CD and half and full duplex are

coming with Ethernet technology.

Eventually the development in Ethernet technology has became a new milestone in

industrial applications. That is by connecting industrial devices to a network people took the

advantage in remote controlling and remote monitoring of the devices. By doing this labor cost

can be reduced and the flexibility in controlling applications has increased. The LANs used

within an industry is using industrial Ethernet technology and as the name implies it carries bit

2

different features rather than a common Ethernet application. Figure 1.1 shows the industrial

Local area network of an industrial environment.

Figure 1.1: Local area network of an industrial environment

But the problem is many of devices used in factories (We call as non-pc devices) cannot

be connected to a network directly because these devices do not have an installed TCP/IP stack

on their memory and no RJ45 port (Ethernet port). Therefore obviously they cannot perform any

of the function which will be supported for networking capability. But fortunately these kinds of

devices have RS232 serial interfaces. These interfaces are build-in units and they are supposed to

use for configuration purposes in the device. Technicians connect laptops or PCs to the device by

using these interfaces and do the configurations or modifications to the device.

But developments in technology have made it possible for embedded systems to

communicate in networks as well as on the Internet. This kind of embedded system [3] has

computer intelligence and is dedicated to performing a single task, or a group of related tasks. As

an example embedded systems can be used for perform monitoring and control functions such as

gathering and reporting sensor readings or controlling motors and switches. Then the information

can be send through the network by getting necessary networking functions.

These embedded system features and network capability can be used for remote

accessing for non-pc devices. In this project this an embedded system converter between RS232

interfaces and RJ45 interface is developed. This feature will upgrade the position of non-pc

Power Meters

(Non-pc devices)

? Ethernet

interface

Serial

interface

Power meter

(Non-PC device)

Firewall

Server

Router

PC3 PC2 PC1

Switch

3

devices. Then the non-pc devices can be connected to the Ethernet network through the

embedded system converter. Then they can be monitored, controlled and modified by remote

logging to the device. Non-pc devices such as power meters, generators, motors and factory

modules can be used more effectively if they can be remote accessed. After developing the

embedded system converter it will be implemented as shown in figure 1.2.

Figure 1.2: implementing the embedded system converter in the industrial LAN

1.2 Problem Statement

Developing, networking capability in non-pc devices which can be found very beneficial.

But implementing such an application can be found as difficult because they have not inbuilt

structure. Also developing such an application in non-pc devices will be need high cost. It will

change the basic structure of the device. Basically this kind of implementation cannot be done to

existing devices.

1.3 Objectives and scope

The objective of this project is to develop a compact, integrated web enable solution for

any non-pc devices with serial capability. Non-pc devices dont have the networking capability

or installed TCP/IP stack in the devices. Therefore to enable the networking capability in a non-

pc device there has to be a separate device.

Power Meters

(Non-pc devices)

? Ethernet

interface

Serial

interface

Embedded system converter

Power meter

(Non-PC device)

Embedded System

Converter

Firewall

Server

Router

PC3 PC2 PC1

Switch

4

Thousands of existing devices that dont support Ethernet have an RS232 serial interface.

This serial interface can be used to gather the output or the measurement reading of the device.

As an example in a power meter, the power meter reading. These data are transmitted as bits in

digital format. The purpose of creating this embedded Ethernet module (serial-to-Ethernet

Bridge), is to communicate with devices having RS232 serial interface in an Ethernet network.

This module connects to the non-pc devices serial interface and to an Ethernet network.

Computers anywhere in the network can then exchange data with the device. After being

configured, the module sends received serial data on the network in TCP segments and sends

data received in TCP segments to the devices serial interface.

With the embedded Ethernet module, it can be used with any electronic product for

applications such as:

Remote diagnostics and upgrades.

Asset tracking and replenishment.

Automation and control.

Power management.

Remote collaboration.

Personalized content delivery.

This system comprises of Ethernet Controller, Microcontroller and associated interfacing

circuitry. By incorporating this device to a product, users can quickly and easily gain serial to

Ethernet networking capability as a standard feature. Therefore equipment can be accessed and

controlled over the Internet.

The development of the embedded Ethernet module will contain the following:

To study and research on the technology of embedded system design.

To study and research about various microcontroller architectures.

To study and research about the external EEPROM technology.

To study and research about the TCP/IP stack.

To study and research about security of network infrastructure including encryption

methods.

5

To study about the commands, this can be sent to the target board via UDP messages or

the HTTP GET.

To learn programming using C language.

To study on how to interface Ethernet Controllers.

To research and study about the embedded design for power requirements.

To design the database program for the user.

To research on future developments in this area.

All the processing of the system flow is done by the Microcontroller and the RS232 interface

is used for receiving data from the user device. This system can be easily expanded and

customized based on the users requirements.

1.4 Research Methodology

An embedded microchip is required by the project. Therefore a Modtronix sbc65ec

microchip [1] is selected as it was the most suitable, efficient and affordable microchip that has

been found. It is further explained in below paragraph why this microchip has been chosen. But

the problem is this specified chip is not available in the local market. Therefore in order to

achieve the target it has to be imported from abroad.

This microcontroller is included 32 general purpose user programmable I/O ports and

also this is included 12 users programmable, 10 bit Analog to Digital converters. Microcontroller

can be used RJ45 connector with built in LEDs to indicate link and activity status. And also

microcontroller can be used RS232 interface via 3 pin connector. The SER3S6FT serial port

cable can be used to connect to the serial port of a target DTE device. Target device is sent bit

values through RS232 serial port to module and then module is processed and converted bit

values to IP packets using TCP/IP stack. Microcontroller is Full TCP state machine and also it is

modular Design. Free Modtronix TCP/IP stack is recompiled in order to deliver the MAC, IP,

ARP, ICMP, TCP, UDP, HTTP, FTP, DHCP, NetBIOS, and DNS. TCP and UDP are supported

to socket. It is expected to program the micro controller with C language using the MPLAB

IDE tool, and further it is expected to implement a web server for remote monitoring. Web

application is totally developed with HTML.

6

Then Web Server is implemented a HTTP Web Server supporting CGI commands and it

is capable of creating Dynamic Web Pages. This can be used to display port values, analog input

values and other real time information on web pages. CGI commands are accepted via the HTTP

GET command. These commands can for example be used for setting the state of port pins.[2]

The firmware has to be written in C, and can be compiled with the Hi Tech or Microchip

MPLAB C18 compilers. If there are errors exist in the program, then the program has to be

debugged and compiled again. This process is continued until program is corrected. Then the

module is to be simulated using PROTEUS simulating tool. After that the microcontroller is to

be programmed in a using program development kit with WINPIC tool. Then module circuit is to

be developed based on the successfulness of the previous steps. Then MySQL database is used to

save past time information of microcontroller board. These stored data is used to make a decision

and analysis the system.

1.5 Resources required and tentative budget

Item Required Quantity Price per

item ($)

Total price

Microcontroller PIC18F6621 1 - -

Ethernet Controller RTL8019AS 1 - -

Serial port Cable 1 - -

SBC65EC Module with Serial 1 76.18 76.18

TCP/IP stack 1 - -

PICkit2 Programmer 1 27 27

PGM2KIT Adapter 1 16 16

DC Power adapter (7-35v) 1 10 10

Expansion boards 2 3 6

CAT 5E Network cable 3 1.5 4.5

4-port Switch 1 30 30

Table 1.1: Resources required and tentative budget

7

1.6 Time plan

Table 1.2: Time plan for the project

8

Chapter 02

2.1 Selecting the chip and advantageous

The SBC65EC is a cheap module compared to other modules in the market. And also it

possesses interesting features which will be helpful for the project aspects. The SBC65EC is a

single board computer with 10Mbs Ethernet and RS232 interface. It can be added to any

10/100Mbs Ethernet network. It is assembled with a PIC18F6621 CPU and supplied with the

Modtronix Free TCP/IP stack (a modified version of the free Microchip TCP/IP stack) written in

C, that can be compiled with the Hi Tech or Microchip PIC18 C compilers. And the TCP/IP

stack can be downloaded through modtronix product page. Typical applications include HTTP

Web servers, Mail clients, Ethernet to RS232 interface converter, Ethernet to RS485 interface

converters, Remote control via Web Server, Protocol Bridge applications - Ethernet to USART,

CAN, I2C, SPI etc. The most interesting advantage of the module is it doesnt need any kind of

programming tool to program the module. The module can be configured directly through a PC

without using a special programming tool.[2]

2.1.1 Features

Module can be easily upgrade or expand it with any of the other MixroX products.

Has 32 general purpose user programmable I/O, of which 12 can be configured as 10 bit

Analog Inputs.

Can be used as a daughter board to Ethernet enables any product.

Diode protected 2.1mm power connector for standard DC transformer. Center is positive.

64KBytes FLASH, 3840 Bytes SRAM and pluggable EEPROM. Default TCP/IP stack

uses less than half the available memory, which leaved heaps of code space for custom

code.

Wide operating voltage range from 7-35V.

Default operating frequency of 40MHz, software configurable low power mode that runs

at 10MHz.

RJ45 connector with two built in LEDs. Green LED is for link indication, yellow LED is

for activity.

9

Assembled with 10BaseT Ethernet and RS232 interface with +- 15kV ESD protection.

RS232 interface via 3 pin Molex type connector or Daughter Board connector.

Has a 40 pin Daughter Board connector.

Assembled with brand name, quality components.

Has an ICSP (In Circuit Serial Programming) connector (ICPC1 type) - CPU can be

programmed and debugged in circuit.

Is designed to run with the freely available Modtronix TCP/IP stack that features:

Includes MAC, IP, ARP, ICMP, TCP, UDP, HTTP, FTP, DHCP, IP Gleaning, MPFS

Socket support for TCP and UDP

Portable across PIC18 MCUs

Out-of-box support for Microchip C18 and Hi-Tech PICC-18 compilers

RTOS independent

Full TCP state machine

Modular Design

2.1.2 Main components of the module

Figure 2.1: SBC65EC Module

Serial port

Ethernet port

(RJ45)

PIC18F6621 CPU

EEPROM

RTL8019AS

Ethernet Controller

ISCP connector

Power connector

Analog and

Digital I/O pins

Analog and

Digital I/O pins

10

RTL8019AS Ethernet Controller

The RTL8019AS is a highly integrated Ethernet Controller which offers a simple

solution to implement a Plug and Play NE2000 compatible adapter with full-duplex and power

down features. The full-duplex function enables simultaneously transmission and reception on

the twisted-pair link to a full-duplex Ethernet switching hub. This feature not only increases

the channel bandwidth from 10 to 20 Mbps but also avoids the performance degrading

problem due to the channel contention characteristics of the Ethernet CSMA/CD

protocol.[4]

PIC18F6621 CPU

This is the central processing unit of the module with 64KB program memory and

1024bytes internal data EEPROM.[2]

External EEPROM

The SBC65EC board has an 8 pin IC socket for mounting a serial EEPROM, like the

24LC256 (32Kbytes) or 24LC512 (64 Kbytes) chips. Depending on the SBC65EC variant, an

EEPROM might be fitted. The standard SBC65EC board is fitted with a 24LC256 EEPROM and

the PIC programmed with the Modtronix TCP/IP stack (modified Microchip TCP/IP stack) that

uses the external EEPROM for storing configuration data and web pages. The 24LC256 has

32Kbytes of non volatile memory, which is large enough for several web pages, including some

small pictures. If this is not large enough, a larger 24LC512 chip can be fitted that can hold twice

as much data.[2]

Power connector

This is the connector point of external DC power to the main board. The operating

voltage range is from 7 30V. In the project the operating voltage is kept in 12V.

Ethernet (RJ45)

The SBC65EC has a 10Mbs Ethernet port. The RJ45 connector meets IEEE 802.3

standards and FCC mechanical requirements. The RJ45 connector has two built in LEDs, a green

LED for link indication, and a yellow LED for activity.[2]

11

RS232

The SBC65EC has a USART interface with +- 15kV ESD protection. The USART

signals are available via a 3 pin Molex type connector or the Daughter Board connector. Four

solder jumpers (SJ1 to SJ4) on the back of the board are used to configure if the USART signals

are RS232 or TTL voltage levels see circuit diagram at end of document for details.

At delivery solder jumpers SJ3 and SJ4 are made, which configures the USART signals

for RS232 voltage levels. By making solder jumpers SJ1 and SJ2, and opening SJ3 and SJ4, the

USART pins can be configured for TTL signal levels.[2]

ISCP connector

The SBC65EC has an ICSP (In Circuit Serial Programming) connector (ICPC1 type).

This enables the PIC to be programmed and debugged in circuit.[2]

Analog and Digital I/O pins

The SBC65EC has 32 I/O pins available for general purpose user I/O. Each of these pins can

be configured separately to be inputs or outputs. Digital inputs and outputs are 0 to 5V. Inputs

are 3V tolerant, and outputs can be made 3V tolerant by adding a series resistor (assuming 3V

input will have clamping diodes). The SBC65EC can be configured to have between 1 to 12

analog inputs. Each channel has a 10 bit resolution. [2]

An interesting feature of the module is the embedded server in the device. It can be used for

remote login to the module as a web client. A remote user can log on to the web server and

retrieve data from the module. If the industrial LAN is connected to the internet users from the

internet can be also log on the module. Therefore the user has the power to adjust variables

potentially from anywhere in the world.

However, the main disadvantages of using an embedded system to host a web server, rather

than a PC are the limited processing power and memory size. Nevertheless, with the rapid

increase of silicon density and ongoing microprocessor / microcontroller technology, it is

foreseeable that these problems can be overcome although there would be significant impact on

the price of the overall product, when using a high specification system.

12

Since the microchip TCP/IP stack is written in C, a C compiler must be used to convert the

program to machine code. Fortunately, there is a free student edition of the microchip C compiler

for the 18 series of PIC (a.k.a. MCC18). The only differences to a C compiler for the PC are the

additional library functions.

Not all the functions usually available are present

Some of the functions that are present have more limited functionality than their

counterparts on PC C compilers

Data-types must be handled correctly, especially when data-passing between functions,

e.g. when comparing a string, two variables must be passed strcmp(str1,str2); and not

strcmp(str1,teststring);

2.2 The steps of the project up to the first progress

2.2.1 Testing the module

Figure 2.2: The testing environment

The purpose of this test is verifying that the module is working properly and it converts

the serial data into Ethernet data packets and vice versa. If the module is working properly, the

data send by the PC A should be captured by Wireshark [5] in PC B. In the testing environment

PC B and module will have been assigned to IP addresses in a same network.

The PC A connected to the RS232 interface of the embedded system converter and it is

running a HyperTerminal[6] program ( HyperTerminal is a program which can be used to

connect to other computers, Telnet sites and host computers, using either a modem or Ethernet

PC A

Hyperterminal

PC B

Wireshark

Embedded

system

converter

13

connection). The PC B connected to the Ethernet (RJ45) interface and it is running Wireshark

(Wireshark is an open-source packet analyzer. It used for network troubleshooting, analysis,

software and communications protocol development).

In PC A,by setting up the Hyperterminal parameters as in figure 2.3 ,a connection

between PC A and module can be established. Then character a send to the PC B by using

hyperternminal (see figure 2.4). The wireshark program running in PC B captured the data

packet which was send by PC A (see figure2.5). [7]

Figure 2.3: Setting up the parameters of the HyperTerminal of PC A

14

Figure 2.4: Sending characters from Hyperterminal

Figure 2.5: Capturing the data packets from Wireshark

15

By analyzing the Wireshark captured UDP packet (see blue line of figure 2.5) it is shown

that the ASCII value of received data is 61. That is the ASCII value of character a. It means the

module is working properly. After that the module is mounted on a Vero board and connects a

female RS232 interface to the module as shown in figure 2.6.

Figure 2.6: Embedded system converter

2.2.2 Configure the web server step1

The module has to be developed so that, it can extract the necessary details from the

device and display them at the web server. By developing the web server outsiders will be able to

log on to the web server for information. The module extracts serial data from the device through

the serial interface, converts them to data packets and sends them via Ethernet interface to the

network. This is done by three steps.

1. Develop the program

The configurations files are located in the firmware on the SBC65EC. The firmware

consists many header files and three header files are developed so that, it meets our

requirements. Those header file are HTTPEXEC.C, HTTP.C and CMD.C. The developed C

codes are in Appendix A-Part1.

16

2. Update firmware on SBC65EC web server

Update firmware on SBC65EC web server that is install program into PIC18F6621 micro

controller can be done with the Modtronix Network Bootloader, no PIC programmer is required.

To do this downloads the latest version of the firmware (V3.10) from

www.modtronix.com/products/sbc65ec/firmware and Downlaod and install the Modtronix

Network Bootloader (V1.06) from www.modtronix.com/soft/netloader/

The boot loader is in-built software in the module. When the module is connected to a

network, the firmware updates files can send to the module using the network loader in a PC.

Through the network loader the developed program was send to the module using default web

server as shown in figure 2.7. The target IP address is IP address of the SBC65EC web server.

Web server automatically inserts the relevant programs to the proper memory locations. [8]

Figure 2.7: The Network Bootloader

17

3. Web page designing

After developing the web server, the default web pages are modified as necessary and a

new web page is designed to display the necessary data. The source code for the default web

pages contained on the Modtronix SBC65EC Web Server is located in the

"../src/webpages/default" folder of the downloaded source code. The newly designed web page is

shown in figure 2.8.

Figure 2.8: The newly designed web page

The Modtronix SBC65EC Web Server uses the FSEE File System to store Web pages in

the external EEPROM. All files making up the web pages have to have the format 8.3 (file name

no longer than 8 characters and extension no longer than 3 characters), and must be located in a

single folder. Any file starting with the 'X' character will require the user to be logged in to view

it, for example "XPAGE.HTM".

Web files cannot be uploaded to the Modtronix SBC65EC Web Server individually. All

files have to be compiled into a File System Image, and then this image is uploaded to the target.

The Modtronix Network Bootloader application is used to create and upload this file to the target

Ethernet board. The following method is used to upload the File System Image to the target

board.[9]

18

Uploading the File System Image with a FTP client

A FTP client is used to connect to the target board and upload the File System Image.

The default user name is "admin" and the password is "pw". After connecting to the target board,

simply upload the entire File System Image file. After doing this, the target will contain the new

Web pages.

2.3 Testing the program

Figure 2.9: Testing the program

The PC A connected to the RS232 interface of the module and setting up the parameters

of the HyperTerminal of PC A for serial communication. (See Appendix B) The PC B connected

to the Ethernet (RJ45) interface. Through PC B connect to the SBC65EC Web Server using the

internet explorer and browse the newly created web page. Then the serial data can be sent to the

module by typing some characters in the HyperTerminal of PC A and the newly created web

page shows the characters sent from PC A. Here, the PC A is used as the serial device instead

digital power meter.

2.4 Selecting a non-pc device

In order to illustrate the mechanism of the converter, a serial input is needed during the

project. In the 1st progress a PC is used in order to supply a serial input to the converter. But

during the 2nd

progress a power meter is suggested to illustrate the serial input for the converter.

The power meter is supposed to get from CEB. But Galle CEB hasnt any single phase power

meters. Therefore we have decided to use an oscillator for supply serial input to the converter

device. But present lab oscillators havent any proper serial output which compatible with our

PC B

PC A

Embedded

system

converter

Ethernet data Serial data

19

converter device. Finally we decided to develop a device which is supplying serial input for the

converter.

The device is act as a single phase power meter because it converts the analog input into

serial data. The purpose of this converter is supply a serial data to the embedded system

converter. The power is measured by using a voltage transformer and given to the power meter.

A microcontroller should be used in the power meter programmed by Micro C. An Analog to

Digital convertor is needed to convert the analog input to a digital format. Then the digital data is

supposed to convert to the serial data format according to the MikroC commands. The circuit

diagram is designed as shown in the figure 2.10.

Figure 2.10: Circuit diagram of the power meter

The PIC18F452 is used as the micro controller of the power meter. USART (Universal

Synchronous Asynchronous Receiver Transmitter) is the implementation technology of the

power monitoring device.

20

2.4.1 Universal Asynchronous Receiver/Transmitter (UART)

The Universal Asynchronous Receiver/Transmitter (UART) controller [10][11] is the key

component of the serial communications subsystem of a computer. The UART takes bytes of

data and transmits the individual bits in a sequential fashion. At the destination, a second UART

re-assembles the bits into complete bytes. Serial transmission is commonly used with modems

and for non-networked communication between computers, terminals and other devices. There

are two primary forms of serial transmission: Synchronous and Asynchronous. Depending on the

modes that are supported by the hardware, the name of the communication sub-system will

usually include a A if it supports Asynchronous communications, and a S if it supports

Synchronous communications. Some common acronyms are:

UART Universal Asynchronous Receiver/Transmitter

USART Universal Synchronous-Asynchronous Receiver/Transmitter

Synchronous serial transmission requires that the sender and receiver share a clock with one

another or that the sender provide a strobe or other timing signal so that the receiver knows when

to read the next bit of the data. In most forms of serial Synchronous communication, if there is

no data available at a given instant to transmit, a fill character must be sent instead so that data is

always being transmitted. Synchronous communication is usually more efficient because only

data bits are transmitted between sender and receiver, and synchronous communication can be

more costly if extra wiring and circuits are required to share a clock signal between the sender

and receiver.

Asynchronous transmission allows data to be transmitted without the sender having to

send a clock signal to the receiver. Instead, the sender and receiver must agree on timing

parameters in advance and special bits are added to each word which is used to synchronize the

sending and receiving units. When a word is given to the UART for Asynchronous

transmissions, a bit called the "Start Bit" is added to the beginning of each word that is to be

transmitted. The Start Bit is used to alert the receiver that a word of data is about to be sent, and

to force the clock in the receiver into synchronization with the clock in the transmitter.

21

The most common use of the USART in asynchronous mode is to communicate to a PC

serial port using the RS-232 protocol. Please note that a driver is required to interface to RS-232

voltage levels.

The signals on the USART pins of the microcontroller use logic levels. This means that

for a five volt supply, the signals will be close to five volts when they are high and close to

ground when they are low. When communicating with other logic devices, these signals can be

used directly. In many applications, particularly with asynchronous communications,

transmission standards such as RS-232 and RS-485 require different voltage levels to be used.

For example, RS-232 uses a voltage below minus five volts to represent a logic one and a voltage

above five volts to represent a logic zero.

The rate at which data is transmitted or received must be always be set using the baud

rate generator unless the USART is being used in synchronous slave mode. As an example of a

baud rate calculation, consider the case of a microcontroller operating at 4MHz that is required to

communicate at 9600 baud with a serial port on a PC. The USART would then be used in

asynchronous mode. [11]

The PIC is programmed using a PIC programmer. The mikroC program codes of the

power meter are in Appendix A-part2. ADCON1 is the analog to digital convertor register. The

ADCON1 = 0x80 configures which pins should be used to convert the analog inputs to digital

output. USART_Init(2400) command initialize the serial port. Within the while loop

ADC_read(1) generate the digital value of the analog signal of the channel one. It is assigned to

Volt_1 variable. After executing the algorithm, while loop returns the value of the variable

power. Using Proteous software, the circuit was executed and Proteous PCB layout is taken.

Then the circuit is implemented. (Figure2.11)

2.4.2 The components used for built the power meter

1) PIC18f452 micro controller

2) MAX232

3) 10uf capacitor 4

4) 15uf capacitor 4

5) 7805 voltage regulator

22

6) Push button

7) Serial female jack

8) Crystal oscillator

9) LED

10) Resistor 1k,330,100

11) 2010 connector 2

Figure 2.11: Implemented power meter

2.4.3 Ratings

Input power: 5V

Baud rate: 2400

Input Signals voltage range: 0-5V

PIC18f452

MAX232

8MHz Crystal oscillator

RS232 Interface

Current transformer terminals

(Signal Input)

Power connector

23

2.4.4 Measuring the voltage of single phase power line

Figure 2.12: Block diagram of the voltage measuring process of the single phase power line

Usually the power line voltage range is 0-230V. But the input of the power meter should

be 0-5V range. Therefore a voltage transformer [8]

should be used to reduce the power range.

When voltage in a circuit is too high to directly apply to measuring instruments, a voltage

transformer produces a reduced voltage accurately proportional to the voltage in the circuit

which can be conveniently connected to measuring and recording instruments. When the power

line voltage is applied to the voltage transformer, it reduces 0-230V range to 0-5V range and

input to the power meter. The current transformer is used to step down the line current. Input to

output ratio of the current transformer is 4:1. Then the output of the power meter is serial data

and it is input to computer through RS232 interface of the PC. The HyperTerminal is set up as

Appendix B. The baud rate is set to 2400.

The voltage transformer and current transformer are connected to the power line and

power meter as figure 2.13. Two full bridge diode rectifiers are used to convert AC to DC. A

load is connected to the power line and the power meter measures the power consumption of the

load. To calculate the power Eq. (2.1) is used. The power factor is 0.8 lagging.

= (2.1)

Where P=Power (W)

V= RMS Voltage (V)

I= RMS Current (A)

= Power Factor

Voltage

Transformer Power Line Power meter

Computer

0-230V 0-5V

Serial Data

24

Current Transformer

45.5

17W

Load

D1D4D2

D3

D1D4D2

D3

CH1

Power

Meter

CH217W

55.5

Figure 2.13: Circuit diagram for the connectivity of the transformers

The power meter outs data periodically as serial data. Period is set to one second. The

power meter is connected to the computer through RS232 interface. The data receiving to the

computer can be seen by Mikro C terminal. The data format is string and size is one byte.

Then the power meter is connected to the embedded system converter though the serial

interface as the block diagram shown in figure 2.14. The serial data is received to the converter

converts into UDP packet and sends them to remote database server via Ethernet interface using

the LAN. Then user can remote log to the web server running on the same server with database

and he/she can analyze real time data as well as previous data.

Current Transformer (2.5V)

230V

6V

Voltage

Transformer

(300mA)

20:5

Power Line

(230V, 50Hz)

25

Figure 2.14: Power monitoring from remote computer

2.5 Development of the database and web applications

Deploying a database for store target devices past records is a good practice in

monitoring aspects of the device.It is the final step of the project.

The client server concept is used as the outputdata gathering statergy in this case.The

remote machine with the database acts as a client to the web server within the converter module.

When the embedded system converter attatched to the industrial application continuosly sends

data to the client machine and client machine will store the data in the database for further

examination.

In addition another web server is running in the remote machine in retriving data from

the database.Any user can log on to the remote web server for observe past records of the target

industrial application.By logging in to the web server, users will be able to not only retrive past

records but also obtain a brief idea about performance of the target device with respect to the

time.

26

Figure 2.15: Deploying database/web server

The database was developed by using mysql and web pages were developed by php,html.

The php code in web client is included mysql queries to store data from the web server in the

databse. The remote web server php code is included mysql queries to retive data from the

databse and show them to the user.

2.5.1 Mysql database

Figure 2.16: Mysql database

Power meter Serial data-

Ethernet data

Converter

Remote machine/

Database /web server

Remote users

27

2.5.2 Php code in web client

Php code in web server

28

2.5.4 Web pages

There are three web pages are developed using Macromedia Dreamweaver Dreamweaver MX.

They are:

Home page

Data displaying page

Contact page

Figure 2.17 shows the home page. It contents a selection list indicating which floor you want

to monitor. Though there are four floors, only ground floor has been considered within the

project scope.

Figure 2.17: Home Page

Second page is developed to display data relevant to the selected floor. It displays a real-

time power consumption graph, current power and total power consumption of the previous

month. Also it facilitates to select the date or time period which you want to check the power

consumption. Figure 2.18 shows the second page.

29

Figure 2.18: Data displaying page

As shown in figure 2.19 third page is the contact page. It shows the contact details

regarding to the system. It contains the names, contact numbers and email addresses of the group

members of the group 4.

Figure 2.19: Contact Page

30

2.6 Results

Electric iron is connected to the power line of the system and the power meter is directly

connected to the computer. Using the Mikro C terminal the data can be seen as figure 2.20.

Figure 2.20: Data received from the power meter

Then the power meter disconnected from the computer and connected to the embedded system

converter and converter is connected to the computers Ethernet port. By logging to the

embedded system converter through the web browser, the real time data received to it from the

power meter can be seen in the web page Group 4. The result is shown in the figure 2.21. The

value shown in the webpage is the power consumed by the electric iron. Figure 2.20 shows that

the received values have been changing. The reason is the behavior of the electric iron, which it

always tries to keep its temperature at a constant value by changing power consumption.

31

Figure 2.21: Real time power measured by the power meter

Then another load (a fan) is applied to the system. Wireshark tool is used to capture the data

received to the database server machine from the converter. The data is received as 1byte UDP

packets. Captured packet is shown in figure 2.22.

Figure 2.22: Data capturing of Wireshark

At the same time another capturing tool is used to capture the receiving UDP packets.

The tool is SocketTest. The captured data are shown in the SocketTest terminal line by line. One

32

value send by the power meter is shown by eight lines. Therefore the value is 445.4771 W. (See

figure 2.23)

Figure 2.23: Data capturing of SocketTest

The data are stored in the Mysql database in the central database server. Using the SQL

query the data stored in the database can be seen as shown in the figure 2.24. The SQL query is

Select * from outputdata;

The database has been developed to store the received data in a table. The table consists

of two columns, which are rcvd_time and value. The data in the database have been varied time

to time. It because two loads are connected to the system and one load is a variable load. The

variable load is electric iron. Before power on the loads the received values are zero. First the

iron is powered on. The power consumption is 445.4771W. Then the fan is powered on without

switching off the iron. Then the power consumption is 545.4771W. Power consumption of the

iron is changed time to time to keep it constant temperature. Therefore, the total power

consumption of both load are vary as shown in the figure 2.24.

33

Figure 2.24: Retrieved data from the Mysql database

Remote computer is used to logon to the central database servers web server. All the

values are displayed in the web page as shown in the figure 2.25.

Figure 2.25: Monitoring the power consumption through the web

34

Chapter 3

3.1 Conclusions

Implemented embedded system converter has special added features with comparing the

other such kind of serial to Ethernet converters in the market. The main features are

User name & password authentication.

The user who has administrative credential, can remotely logging to the embedded

system web server and perform the configurations to the PIC18F6621 CPU.

Data Speed of the serial interface :300 bps to 921,600 bps and Ethernet

interface:10/100MB

Low cost

This project is only focused on remote power measuring and monitoring system using the

implemented embedded system converter. The system can be easily install on the existing local

area network an organization and the one who wants to monitor the energy consumption can

remotely log to the central database server and can monitor real time power consumption as well

as past data. It is very beneficial showing the real power consumption on a graph and total

energy for a period of time on the same users screen especially for a production environment.

As there is a database to store previous data user can simply gets the consumed power at any

day, any week, any month and any defined period.

Another advantage is, there is no such kind of embedded system converter in the local

market and the one who is going to import has to pay high cost per one item and also has to spent

money for shipping and other expenses. The converter has one serial port and one Ethernet port.

Therefore you need to install a converter per serial device.

The application of this embedded system converter is greatly broad. It can be used in

power management system, electric power net automatic system, transmission and distribution of

electric power control system, Internet/LAN long-distance visit, industry/factory's automatic

system, building management system, Super markets, label printer and barcode reader system

and medical equipment monitoring system with the new features.

35

3.1.1 Future Development

As explain above the embedded system converter has broad applications. The project is

used only one application. That is remote power measuring and monitoring system. But the

usage of the embedded system converter can be extended by configuring the converter to support

for label printers, medical equipments, barcode reader and various time of measuring equipments

used by the industry.

The remote power monitoring system implemented in the project can be further extended

as a major portion of a building management system (BMS). A Building Management System is

a computer-based control system installed in buildings that controls and monitors the buildings

mechanical and electrical equipment such as power systems, ventilation, lighting, fire systems,

and security systems. A BMS consists of software and hardware; the software program, usually

configured in a hierarchical manner, can be proprietary, using such protocols as C-bus, Profibus,

and so on. Vendors are also producing BMSs that integrate using Internet protocols and open

standards such as DeviceNet, SOAP, XML, BACnet, LonWorks and Modbus.[14] Figure 3.1

shows a power monitoring system for the whole labs in the Department of Electrical and

Information Engineering, Faculty of Engineering, University of Galle.

Figure 3.1: Power monitoring system of the Department of Electrical & Information Engineering

LB5 LB6

LB3

LAB1 LB2

LB4

Heads PC Network Administrators PC

Other Servers

Database Server

Router

Switch1

Department of Electrical & Information Engineering

Power line

Power line

Power line

Power line

Power line

Power line

Power meter 5

Power meter 3

Power meter1

Power meter 6

Power meter 4

Power meter 2

Converter 5

Converter 3

Converter 1 Converter 2

Converter 4

Converter 6

Internet

36

As figure 3.1 shows, the system can be extended to monitor whole labs in the Department

of Electrical & Information Engineering from one computer. The department head as well can

monitor the power consumed by each lab from his computer. The network administrator of the

department is given the administrative credential to configuring and troubleshooting the system.

37

References

[1] www.modtronix.com

[2] http://www.digitale-elektronik.de/shopsystem/sbc65ecr3.pdf

[3] Embedded Ethernet and Internet Complete, Designing and Programming Small Devices for

Networking, Jan Axelson, Published by Lakeview Research LLC.

[4] RTL8019AS Realtek Full-Duplex Ethernet Controller with Plug and Play Function

(RealPNP), REALTEK SEMICONDUCTOR CORP.

[5] http://www.wireshark.org/

[6] http://technet.microsoft.com/en-us/library/bb457166.aspx

[7] http://www-

tss.cisco.com/eservice/compass/common/tasks/task_veri_Config_Hyperterminal.htm

[8]http://www.modtronix.com/products/sbc65ec/websrvr65_v310/mainpage.php?mainpagehtml=

page_webpages&mainpageName=

[9]http://www.modtronix.com/products/sbc65ec/websrvr65_v310/mainpage.php?mainpagehtml=

page_update_webpages&mainpageName=

[10] http://www.freebsd.org/doc/en/articles/serial-uart/index.html

[11] http://ww1.microchip.com/downloads/en/DeviceDoc/usart.pdf

[12] http://en.wikipedia.org/wiki/Transformer

[13] Serial Port Complete: COM Ports, USB Virtual COM Ports, and Ports for Embedded

Systems, Second Edition, Jan Axelson, Lakeview Research LLC, Madison, WI 53704.

[14] http://en.wikipedia.org/wiki/Building_management_system September 8, 2011.

38

Appendix A

Part1: Developing firmware

1.1 HTTPEXEC.C

#define THIS_IS_HTTPEXEC_MODULE

#include

#include "projdefs.h"

#include "httpexec.h"

#include "cmd.h"

#include "debug.h"

#include "appcfg.h"

#include "net\stacktsk.h"

#include "net\http.h"

#include "net\delay.h"

#include "net\helpers.h"

#include "net\security.h" //Security related code

WORD HTTPGetVar(HTTP_INFO* httpInfo, BYTE* val)

{

GETTAG_INFO getTagInfo;

getTagInfo.tagVal = httpInfo->var.get.tagVal; //Value of

requested tag

getTagInfo.tagGroup = httpInfo->var.get.tagGroup; //Group of

requested tag

getTagInfo.ref = httpInfo->var.get.varRef; //Current

callback reference with respect to 'var' variable.

getTagInfo.val = val;

//In case requested var not found, set it to NULL character and

return HTTP_END_OF_VAR

*val = '\0';

//Get the current user logged in for this HTTP connection

getTagInfo.user = HTTPGetCurrentUser(httpInfo);

cmdGetTag(&getTagInfo);

return getTagInfo.ref;

39

}

#endif

1.2 HTTP.C

#define THIS_IS_HTTP_SERVER

#include

#include "projdefs.h"

#include "net\checkcfg.h"

#include "net\http.h"

#include "net\fsee.h"

#include "net\tcp.h"

#include "cmd.h"

#include "debug.h"

#if defined(STACK_USE_HTTP_SERVER)

void HTTPServer(void)

{

BYTE conn;

//If no activity for 2 minutes, log out

//if (TickGetDiff16bit(lastActivity) >= ((TICK16)TICKS_PER_SECOND *

(TICK16)120) ) {

//Future code might implement an auto logout method again

//}

//Process each connection

for ( conn = 0; conn < MAX_HTTP_CONNECTIONS; conn++ ) {

HTTPProcess(conn);

}

}

static void HTTPProcess(HTTP_HANDLE h)

{

BYTE rqstRes[HTTP_MAX_RESOURCE_NAME_LEN + 1];

HTTP_COMMAND httpCommand;

BOOL lbContinue;

BYTE i; //Temp variable

HTTP_INFO* ph;

40

ROM char* romString;

WORD rxBufPos;

union

{

struct

{

unsigned char bHasParameters : 1;

unsigned char bTemp : 1;

} bits;

BYTE val;

} flags;

ph = &HCB[h];

lbContinue = TRUE;

while( lbContinue )

{

lbContinue = FALSE;

flags.val = 0;

.

1.3 CMD.C

#define THIS_IS_CMD_MODULE

#include

#include "projdefs.h"

#include "cmd.h"

#include "debug.h"

#include "appcfg.h"

#include "lcd2s.h"

#include "ior5e.h"

#include "mxd2r.h"

#include "busser1.h"// edit..............................

#include "net\stacktsk.h"

#include "net\udp.h"

#include "net\helpers.h"

#include "net\security.h" //Security related code

41

/////////////////////////////////////////////////

//General purpose and Port pin variables - they are:

// - 'a' Used for port a value. a0x will display 1 or 0, a1x will

display on or off

// - 'b' Used for port b value.

// - 'c' Used for port c value.

// - 'd' Reserved for port d value.

// - 'e' Reserved for port e value.

// - 'f' Used for port f value.

// - 'g' Used for port g value.

// - 'h' Reserved for port h value.

// - 'i' Reserved for future use

// - 'j' Reserved for port h value.

if ((tagGroup >= VARGROUP_PORTA) && (tagGroup

42

p = (BYTE *)(&TRISA) + tmp;

//Requested pin is an output - use LATCH register

if ( (*p & mask) == 0 )

{

p = (BYTE *)(&LATA) + tmp; //Get pointer to LATCH register

flags |= FLAGS_OUTPUT_PIN;

}

//Requested pin is an input - use PORT register

else

{

p = (BYTE *)(&PORTA) + tmp;

}

tmp = tagVal & 0xf0;

//Return "0" or "1"

if (tmp == 0x00)

{

//Set val to '0' or '1' depending on state of pin

*pGetTagInfo->val = ((*p & mask) == 0) ? '0' : '1';

pGetTagInfo->ref = HTTP_END_OF_VAR;

return 1; //One byte was written

}

//Return "on" or "off"

else if (tmp == 0x10)

{

pGetTagInfo->ref = cmdGetROMStringVar(ref, pGetTagInfo-

>val,

((*p & mask) == 0) ? HTMLSTR_OFF : HTMLSTR_ON);

return 1; //One byte was written

}

//Return "" depending on if port is configured as

input or output

else if ( ((tmp == 0x20) && ((flags & FLAGS_OUTPUT_PIN) == 0))

||

((tmp == 0x30) && ((flags & FLAGS_OUTPUT_PIN) != 0))

)

{

pGetTagInfo->ref = cmdGetROMStringVar(ref, pGetTagInfo-

>val,

((tagVal & 0x08) == 0) ? HTMLSTR_CMNT_START :

HTMLSTR_CMNT_END);

return 1; //One byte was written

43

}

//Return "checked" if port configured as output or input

else if (tmp == 0x40)

{

if (tagVal & 0x08) {

//Return "checked" if port configured as input

if ( (flags & FLAGS_OUTPUT_PIN) == 0 ) {

pGetTagInfo->ref = cmdGetROMStringVar(ref,

pGetTagInfo->val, HTMLSTR_CHECKED);

return 1; //One byte was written

}

}

else {

//Return "checked" if port configured as output

if ( (flags & FLAGS_OUTPUT_PIN) != 0 ) {

pGetTagInfo->ref = cmdGetROMStringVar(ref,

pGetTagInfo->val, HTMLSTR_CHECKED);

return 1; //One byte was written

}

}

}

//Return "1" if port configured as input, else 0

else if (tmp == 0x50)

{

//Set val to '0' or '1' depending on pin direction

*pGetTagInfo->val = (flags & FLAGS_OUTPUT_PIN) ? '0' : '1';

pGetTagInfo->ref = HTTP_END_OF_VAR;

return 1; //One byte was written

}

}

//custom code apply here, serial input

else if (tagGroup == 'T')

{

BYTE v;

if (tagVal == 1){

if (ref == HTTP_START_OF_VAR)

{

v = serGetByte();

}

if (v==198)

v='*';

}

44

pGetTagInfo->ref = cmdGetStringVar(ref, pGetTagInfo->val,

&v);

return 1; //One byte was written

}

Part 2: C program code of power monitoring device

int j;

float

z_max,r_max,v_max,i_max,v_sub,i_real,v_rms,i_rms,power,i_final,k,r_ac,z_ac,k1

;

char txt[8];

void main()

{

unsigned int x=0,p=0,y=0,q=0,r=0,z=0;

ADCON1 = 0x80; // Configure analog inputs and Vref

TRISA = 0xFF; // PORTA is input

TRISC = 0xBF; // RC6 output

Usart_Init(2400);

while(1)

{

int a;

for(j=0;jz)

{

z=x;

}

else

{

z=z;

}

if(y>z)

{

z=y;

}

else

{

z=z;

}

z_max=(z*5.0)/1024;

45

if(zr)

{

r=p;

}

else

{

r=r;

}

if(q>r)

{

r=q;

}

else

{

r=r;

}

}

r_max= (r*5.0)/1024.0;

if(r

46

}

Appendix B

B.1 Serial data transmission [13]

A serial port is a computer interface that transmits data one bit at a time. Most serial ports

are bidirectional. It means they can both send and receive data. Transmitting one bit at a time

might seem inefficient but has advantages, including the ability to use inexpensive cables and

small connectors. Communicating via serial ports requires three things. Those are computers

with serial ports, a cable or wireless interface that provides a physical link between the ports, and

programming to manage the communications.

Devices with asynchronous serial ports typically contain a hardware component called a

Universal Asynchronous Transmitter/Receiver (UART). The UART converts between parallel

and serial data and handles other low-level details of serial communications.

Often in Embedded systems, serial ports with microcontrollers are used to communicate with

other embedded systems and PCs. These microcontrollers, which contain CPU and I/O hardware

such as UARTs. Microcontroller chips can be classified by data-bus width: 8-bit chips have an 8-

bit data path and are popular in monitoring and control applications.

A serial port output that functions as a transmitter or driver sends bits one at a time to a serial-

port input that functions as a receiver, typically on a different computer. The cable between the

computers typically has a dedicated data path for each direction. Some serial interfaces have a

single, shared data path for both directions, with the transmitters taking turns.

B.1.1 Asynchronous and Synchronous Communications

In a synchronous protocol the interface includes a clock line typically controlled by one

of the computers and all transmitted bits synchronize to that clock. Each transmitted bit is valid

at a defined time after a clocks rising or falling edge depending on the protocol.

47

Figure B.1: Synchronous transmission

In an asynchronous serial port the interface doesnt include a clock line. Instead, each

computer provides its own clock to use as a timing reference. The computers must agree on a

clock frequency and the actual frequencies at each computer must match within a few percent. A

transmitted Start bit synchronizes the transmitters and receivers clocks.

Figure B.2: Asynchronous transmission

48

Therefore basically Synchronous transmission needs a clock line from a centralized

computer, while asynchronous transmissions require each computer to have its own clock.

B.1.2 Bit Rate and Baud Rate

The bit rate is the number of bits per second transmitted or received per unit of time,

usually expressed as bits per second (bps). Baud rate is the number of possible events, or data

transitions, per second. The number of characters transmitted per second equals the bit rate

divided by the number of bits in a word. With 8-N-1 format, a byte of data transmits at 1/10 the

bit rate because each word contains 10 bits: 1 Start bit, 8 data bits, and 1 Stop bit. So a 9600-bps

link using 8-N-1 format can transmit 960 data bytes per second.

To gain access to a port, an application selects a bit rate and other port parameters and

requests to open, or gain access to, the desired port. To send a byte, the application writes the

byte to the transmit buffer of the selected port. The UART then sends the data, bit by bit in the

requested format, adding Stop, Start, and parity bits as needed. In a similar way, the UART

stores received bytes in a buffer. After receiving a byte, the UART can generate an interrupt to

notify an application of received data, or software can poll the port to find out if data has arrived.

B.1.3 Word Formats

A UART transmits data in chunks often called words. Each word contains a Start bit, data

bits, an optional parity bit, and one or more Stop bits. The parity bit can provide a basic form of

error detecting. Most UARTs support multiple word formats. A common format is 8-N-1, where

the transmitter sends each word as one Start bit, followed by eight data bits and one Stop bit. The

data bits transmit beginning with bit 0 (the least significant bit, or LSb).

B.1.4 Sending Bits

Figure B.2 shows how a byte transmits in 8-N-1 format. When idle, the transmitters

output is logic 1. To indicate the beginning of a transmission, the transmitter sends logic 0 for

one bit width. This is the Start bit. After the Start bit, the transmitter sends the 8 data bits in

sequence, beginning with the LSb. The transmitter then sends a logic 1, which functions as the

Stop bit. Immediately following the Stop bit or at any time after, the transmitter can send a new

Start bit to signify the beginning of a new transmitted word.

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At the receiving computer, the transition from logic 1 to the Start bits logic 0 indicates

that a new word is arriving. The transition and the bit rate determine the timing for detecting the

bits that follow. The receiver attempts to read the logic state of each bit near the middle of the

bits time period. Reading in the middle of the period helps ensure that the receiver detects the

bit values correctly even if the transmitting and receiving clocks dont exactly match in

frequency or phase.

A UART typically uses a receive clock with a frequency 16 times faster than the highest

supported bit rate. If the highest bit rate is 9600 bps, the receive clock should be at least 153,600

bps. As Figure 3 shows, after detecting the transition that signals a Start bit, the UART waits 16

clock cycles for the Start bit to end, then waits 8 more cycles to read bit zero in the middle of the

bit. The UART then reads each bit that follows 16 clock cycles after the previous bit. If the

transmitting and receiving clocks dont match exactly, the receiver will read each new bit closer

and closer to an edge of the bit. To read all of the bits in a 10-bit word correctly, transmit and

receive clocks should vary no more than about three percent. With greater variation, by the time

the receiver tries to read the final bits, the timing may be off by so much that the receiver will

read the wrong bits and might not detect the Stop bit. The clocks need to stay

in sync only for the length of a word because each word begins with a new Start bit that

resynchronizes the clocks.

Figure B.3: To determine when to send data and read received data, the transmitter and receiver each use

a clock that is typically 16 times the bit rate

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The clocks need to stay in sync only for the length of a word because each word begins with a

new Start bit that resynchronizes the clocks. Because of the need for accurate timing,

asynchronous interfaces require stable timing references such as crystal oscillators.

B.2 COM PORT configuration on PC

In PCs, applications access most serial ports as COM ports. Other names for COM ports

are communications port and Com port. For each COM port, an operating-system driver assigns

a symbolic link name such as COM1, COM2, and so on, which applications use to detect and

access the port.

The Windows Device Manager shows information about each COM port. To access the

Device Manager, right click on My Computer, click Manage, and in the Computer Management

pane, select Device Manager. Or click Start and select Settings > Control Panel > System >

Hardware > Device Manager. Or save some clicks by creating a shortcut to the file

devmgmt.msc in Windows\System32.

To view a COM port in the Device Manager, click Ports (COM & LPT), right-click a

COM port, and select Properties. The Properties window has several tabs that display the ports

property pages. A vendor-provided co-installer can supply custom property pages for vendor-

specific device properties. The pages shown below are typical. In order to establish a serial

connection between two PCs, several parameters should be matched and have to be set prior to

the connection opening etc bit rate. During the testing process, in order to open a serial

connection between PC A and the module these parameters had been set according to the

connection type.

The Port Settings tab displays the default settings for the port. A USB/serial converter

doesnt use the bit rate, parity, and Stop bits in communications between the PC and the

converter, but a driver can send these values to a device that uses the settings on its serial port.

For example, a USB/RS232 converter can set the parameters of its RS232 port to match values

specified on the PC. The Advanced Settings window enables setting buffer properties and the

COM-port number. Applications can change the parameters from the default values set in the

Device Manager.

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Figure B.4: COM Port Properties

In order to establish a serial connection between two PCs, several parameters should be

matched and have to be set prior to the connection opening etc bit rate. During the testing

process, in order to open a serial connection between PC A and the module these parameters had

been set according to the connection type.

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Figure B.5: Set the COM1 Properties