A Quick Introduction to RFID

8/20/2019 A Quick Introduction to RFID

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A Quick Introduction to RFID

In its bare minimum, a RFID system consists of two main components:

• Reader/Writer

• Tags

An RFID reader/writer contains a scanning antenna and a transceiver It

uses t!e scanning antenna to send out radio fre"uency signa#s in a

re#ati$e s!ort range T!e radio fre"uency sent out is used to

communicate and power tags %a#so known as transponders& t!at are

wit!in range, w!ic! wi## t!en transmit t!e data on t!e tag back to t!e

reader T!e information sent out by t!e tag is t!en picked up by t!e

scanning antenna T!e data is t!en interpreted and decoded by t!etranscei$er

T!ere are two types of RFID tags'active and passive Acti$e RFID tags

!a$e t!eir own power source and !ence t!ey can transmit signa#s t!at

tra$e# fart!er In contrast, passi$e RFID tags !a$e no power source and

t!ey !a$e to re#y so#e#y on t!e signa# sent from t!e scanning antenna

to power t!em (ence t!e range supported by passi$e tags is #imited

Acti$e tags are bigger in si)e t!an passi$e tags and !a$e a #imited #ife

span %unti# t!e power source runs out& *assi$e tags, on t!e ot!er !and,

are muc! sma##er in si)e and !a$e $irtua##y un#imited #ife span

T!ere are two types of RFID tags: acti$e andpassi$e

RFID systems are categori)ed by t!eir transmitting fre"uencies and are

broad#y grouped into t!ree bands: +ow Fre"uency %+F&, (ig! Fre"uency

%(F&, and #tra (ig! Fre"uency %F(& Table 1 s!ows t!e di-erent

fre"uencies used by t!e t!ree bands and t!eir c!aracteristics.ac! RFID tag !as a uni"ue tag ID Tags carry no more t!an 01 of

data and can store information suc! as !istory, #ocation, etc

2ost common RFID app#ications use t!e tag ID transmitted by RFID

tags as a key to information stored in databases For e3amp#e, an RFID

tag attac!ed to an emp#oyee passcard on#y contains an RFID tag ID,


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w!ic! an app#ication can use to retrie$e more detai#ed emp#oyee

information stored in t!e organi)ation databases W!i#e read-only RFID

app#ications are c!eaper, t!ere are occasions w!ere you mig!t need to

write data back to an RFID tag, in w!ic! case you4## use read'write

tags 5ou mig!t 6nd read'write RFID systems in a subway, for e3amp#e,

w!ere you may need to write back information to a tag in stored $a#ue

cards 7ote t!at some tags can on#y be written once

1ui#ding Attendance TrackingApp#ication

7ow t!at you !a$e a good understanding of !ow RFID works, I4## s!ow

you !ow to bui#d a simp#e attendance app#ication t!at registers an

emp#oyee w!en !e reports for workFigure 1 s!ows t!e user interface

of t!e app#ication

Figure 1: T!e

attendance system you wi## bui#d in t!is artic#e

W!en an emp#oyee scans !is emp#oyee passcard t!at !as an

embedded RFID tag, t!e app#ication t!at recei$es t!e ID from t!e RFID

tag wi## disp#ay t!e emp#oyee information T!e app#ication4s

administrator can assign an unused tag to an emp#oyee by using t!e

buttons on t!e rig!t of t!e app#ication For security reasons, t!e

app#ication wi## c#ear t!e emp#oyee information after t!ree seconds To


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dep#oy t!is app#ication in a rea#'#ife setting, you wou#d !ide t!e

administrati$e functions so t!at t!e user on#y sees t!e necessary

information %see Figure 2&

Figure 2: (iding t!e administrati$e

functions in a dep#oyed en$ironment

RFID Reader 89: *ara##a34s RFID Reader 2odu#e

In t!is e3amp#e, I4## s!ow you !ow to use *ara##a34s RFID Reader 2odu#e

%!ttp://wwwpara##a3com/detai#aspproduct;id?& T!is #ow'cost

RFID reader %@B& reads passi$e RFID transponder tags and uses seria#

communication to transmit t!e tag IDs As you can see in Figure 3,

t!e reader !as four pins at t!e bottom %from #eft to rig!t&:

http://www.parallax.com/detail.asp?product_id=28140http://www.parallax.com/detail.asp?product_id=28140


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Figure 3: T!e *ara##a34s RFID Reader

2odu#e

• C ' EC D power

• /.7A1+. ' .nab#e %Ground& or disab#e %EC D& pin

• HT ' Heria# output

• G7D ' Ground

T!e e-ecti$e read range of *ara##a34s RFID Reader modu#e is 9JK to K

inc!es %depending on t!e tag used& W!en t!e Reader 2odu#e ac"uires

a tag ID, data is sent t!roug! t!e seria# port using a 9'byte AHII

string T!e +F %+ine Feed& ser$es as t!e Htart byte and t!e R %arriageReturn& ser$es as t!e Htop byte T!e ten digits in between ser$e as t!e

uni"ue tag ID

RFID Tags

T!e *ara##a34s RFID Reader 2odu#e reads t!e fo##owing tags:

• > mm 3 = mm Rectang#e Tag

%!ttp://wwwpara##a3com/detai#aspproduct;id9L @ eac!&• ? mm Round Tag %!ttp://wwwpara##a3com/detai#asp

product;idL @ eac!&

Hetting p t!e Reader

http://www.parallax.com/detail.asp?product_id=28141http://www.parallax.com/detail.asp?product_id=28142http://www.parallax.com/detail.asp?product_id=28142http://www.parallax.com/detail.asp?product_id=28141http://www.parallax.com/detail.asp?product_id=28142http://www.parallax.com/detail.asp?product_id=28142


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In order to connect t!e reader to your computer, you need to perform a

TT+'to'RH' #e$e# s!ifting so t!at t!e data can be read $ia a seria#

port ne way wou#d be to connect t!e reader to t!e RS-232 DCE

AppMod %!ttp://wwwpara##a3com/detai#aspproduct;id


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Tip: 1e sure to use a Ostraig!tK seria# cab#e to connect t!e board to

your computer, or e#se you wi## not be ab#e to get any data from t!e

reader

If you do not !a$e a seria# port on your computer, you can use a H1'

to'seria# con$erter to con$ert a H1 connector into a seria# port 5ou

wi## a#so need a D1B straig!t seria# cab#e

Figure 5 s!ows t!e assemb#ed reader and board


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Figure 5: T!e *ara##a3 RFID Reader and t!e Na$e#ine Demo 1oard

connected and ready to go

1ui#ding t!e App#ication ser Interface


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sing Cisua# Htudio ??, create a new Windows app#ication and name

it :PAttendance 5ou wi## use t!e 7ort!wind samp#e database pro$ided

by HQ+ Her$er ??? wit! HQ+ .3press %Hee t!e sidebar, Installing the

Sample Database& To simp#ify data'binding, you wi## use t!e drag'and'

drop data'binding feature t!at is new in Cisua# Htudio ??

In addition, you wi## a#so add a new TagID 6e#d to t!e .mp#oyees tab#e

in t!e 7ort!wind database To do so:

• Go to Her$er .3p#orer %from t!e View menu c!oose Server

Eplorer&

• Rig!t'c#ick on Data onnections and se#ect Add onnection

• He#ect t!e 2icrosoft HQ+ Her$er %H"##ient& data source and in t!e

ser$er name 6e#d, enter OPHQ+.*R.HHK %assuming you !a$e HQ+.3press insta##ed on your #oca# computer& He#ect 7ort!wind as t!e

database name and c#ick 0

• In Her$er .3p#orer, e3pand t!e 7ort!wind database and t!en

t!e Table! item Doub#e'c#ick E"plo#ee! and add t!e TagID 6e#d

%Figure $&


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Figure $: Adding a new TagID 6e#d to t!e .mp#oyees tab#e

%o&e: .nsure t!at t!e data source se#ected is O2icrosoft HQ+ Her$er

%H"##ient&K If it is not, c#ick !ange and se#ect 2icrosoft HQ+ Her$er

First, add a new data source to your proMect by se#ecting Add 7ew Data

Hource from t!e Data menu In t!e Data Hource on6guration Wi)ard

dia#og bo3, se#ect Database and c#ick 7e3t #ick t!e 7ew onnection

button to specify t!e database to use 5ou wi## see t!e Add onnection

dia#og bo3 %Figure '& As before, enter OPHQ+.*R.HHK as t!e ser$er

name and se#ect 7ort!wind as t!e database #ick 0


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Figure ': Adding a new

connection to t!e 7ort!wind database

1ack in t!e Data Hource on6guration Wi)ard, c#ick 7e3t In t!e ne3t

screen, se#ect t!e tab#e and 6e#ds to use .3pand t!e Tab#es and

.mp#oyees item and t!en c!eck t!e fo##owing 6e#ds %Figure (&:


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Figure (: !oosing t!e 6e#ds to use in t!e .mp#oyees tab#e

• .mp#oyeeID

• +ast7ame

• First7ame

• Tit#e

• *!oto

• TagID

From t!e Data menu, c!oose H!ow Data Hources to $iew t!e new#y

added data sourceFigure ) s!ows t!e .mp#oyees data source 1y

defau#t, t!e .mp#oyees tab#e is bound to a DataGridCiew contro# and a##

its 6e#ds %e3cept t!e *!oto 6e#d& are bound to Te3t1o3 contro#s 5ou

s!ou#d c!ange t!e bindings to t!ose as s!own in Table 2


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Figure ): T!e

.mp#oyees data source

T!e .mp#oyees data source s!ou#d now #ook #ike t!e rig!t side

of Figure )

Drag t!e .mp#oyees data source onto t!e defau#t Form9 Figure1* s!ows t!e contro#s t!at automatica##y popu#ate t!e form For t!e

*icture1o3 contro#, set its Hi)e property to OB,99?K and Hi)e2ode to

OHtretc!ImageK

Figure 1*:

T!e data'bound contro#s

%o&e: 2o$e t!e TagID #abe# and its accompanying +abe# contro# %on t!e

rig!t& to t!e top


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To test t!at t!e data'binding works, you can now press F to debug t!e

app#icationFigure 11 s!ows t!e app#ication disp#aying t!e records in

t!e .mp#oyees tab#e

Figure 11:

Testing to ensure t!at t!e data'binding works

7e3t you4## add contro#s to t!e form to a##ow an administrator to assign

a RFID tag to a user Figure 12 s!ows t!e contro#s to add


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Figure 12: *opu#ating t!e form wit! t!e $arious contro#s

For t!e t3tTagID contro#, set bot! t!e Readn#y and t!e 2u#ti#ine

properties to True

In addition, drag a Timer contro# from t!e Too#bo3 onto t!e form T!is

contro# wi## ensure t!at t!e disp#ayed emp#oyee record wi## be c#eared

after t!ree seconds

oding t!e App#ication

Wit! t!e I of t!e app#ication out of t!e way, you can now focus on

writing t!e code to wire up a## t!e contro#s Hwitc! to t!e code'be!ind

of Form9 and import t!e fo##owing namespaces

Imports HystemData


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Imports HystemDataH"##ient

Imports HystemI

Dec#are t!e member $ariab#es and constants seen in +i!&i,g 1

W!en t!e form #oads, you 6rst c#ear t!e disp#ayed emp#oyee by setting

its 6#ter to a non'e3istent tag ID T!e Timer contro# c#ears t!e disp#ayed

emp#oyee after a certain amount of time, and in t!is case you wi## set it

to t!ree seconds %as de6ned by t!e Inter$a# constant& T!at is to say,

w!en an emp#oyee is identi6ed using !is RFID tag, !is information wi##

be c#eared from t!e screen after t!ree seconds

As t!e *ara##a34s RFID Reader 2odu#e uses a seria# connection, you wi##

use t!e Heria#*ort c#ass to communicate wit! t!e reader

%o&e: For t!is e3amp#e, I !a$e assumed t!at you4## connect t!e 2

port to t!e RFID Reader 2odu#e 5ou need to c!ange it to t!e correct

port number for your own use

+i!&i,g 2 s!ows t!e code for t!e Form9;+oad e$ent

To recei$e incoming data from t!e Heria#*ort c#ass, you need to ser$ice

t!e DataRecei$ed e$ent In t!is case, w!en incoming data is recei$ed,

you wi## update t!e t3tTagID contro#+i!&i,g 3 s!ows t!e code for t!e

DataRecei$ed e$ent

5ou need to de6ne a de#egate to ca## a routine to update t!e t3tTagID

contro# (ere, de6ne t!e myDe#egate%& de#egate and t!e

updateTe3t1o3%& subroutine

S''' update t!e Tag ID te3tbo3

*ub#ic De#egate Hub myDe#egate%&

*ub#ic Hub updateTe3t1o3%&

S for recei$ing p#ain AHII te3t

Wit! t3tTagID

AppendTe3t% ;

seria#*ortRead.3isting&

Hcro##Toaret%&

.nd Wit!

.nd Hub


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ne important point you need to understand about RFID readers %at

#east for t!e two RFID readers s!own in t!is artic#e& is t!at w!en a tag

is scanned, it wi## continuous#y send t!e tag ID to t!e seria# connection

For e3amp#e, suppose a tag wit! ID of ?F?BAF is p#aced near t!e

reader In t!is case, t!e reader wi## continuous#y send t!e $a#ue of

?F?BAF to t!e seria# connection For t!e *ara##a34s reader, eac!

$a#ue starts wit! t!e #ine feed c!aracter %c!aracter 9? ' U9?V& and

ends wit! a carriage return c!aracter %c!aracter 9 ' U9V& To make

matters comp#icated, using t!e Read.3isting%& met!od of t!e Heria#*ort

c#ass does not guarantee t!at you wi## read t!e comp#ete tag ID in its

entirety T!is is because a $a#ue may be sent in four b#ocks, #ike t!is:

U9?V?F?B

AF

U9V

5ou may be tempted to use t!e Read+ine%& met!od of t!e Heria#*ort

c#ass to read incoming data, but t!at wi## not work as t!e Read+ine%&

met!od wi## #ook for U9VU9?V at t!e end of t!e #ine 1ut since t!e

incoming data does not end wit! U9?V, t!is wi## cause t!e app#ication

to go into an in6nite #oop

In addition, if you don4t c#ear t!e incoming data bu-er fast enoug!, you

may get a series of data "ueued up #ike t!is:

U9?V

?F

?B

AF

U9VU9?V

?>

9=D

=1

U9V


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Instead of writing e#aborate #ogic to process t!e incoming data, an easy

way is to append a## incoming data to a Te3t1o3 contro# %wit! t!e

2u#ti#ine property set to True& sing t!e data Must described, Figure

13 s!ows w!at t!e Te3t1o3 contro# wi## #ook #ike

Figure 13: Appending incoming

data to a Te3t1o3 contro#

T!e second to t!e #ast #ine wi## !ence a#ways contain t!e Tag ID t!at

you are interested in if t!e #ast #ine is an empty string In contrast, if

t!e tag ID is on#y partia##y recei$ed, t!e state of t!e Te3t1o3 contro#wou#d be as s!own in Figure 14

Figure 14: T!e state of t!e

Te3t1o3 contro# containing t!e #ast incomp#ete tag ID

As a## incoming data is updated in t!e Te3t1o3 contro#, you can c!eck if

t!e tag ID be#ongs to an emp#oyee w!ene$er t!ere are c!anges in t!e

content of t!e Te3t1o3 contro# 5ou4## use t!e Te3t!anged e$ent%+i!&i,g 4& to detect t!e c!ange

T!e Te3t!anged e$ent 6rst e3amines if t!e #ast #ine in t!e t3tTagID

contro# is an empty stringL if it is, t!en t!e scanned tag ID can be found

in t!e second to #ast #ine sing t!is tag ID, t!e code c!ecks t!e time

di-erence between t!e current time and t!e #ast time t!e tag ID was

read If it is #ess t!an t!ree seconds and t!e tag ID is t!e same as t!e

#ast read tag ID, it means t!at it is t!e same user and t!e current tag

ID s!ou#d be ignored sing t!is imp#ementation, t!e same user wou#d

be ignored for t!e ne3t t!ree seconds from t!e moment !e 6rst

scanned !is tag

Wit! t!e tag ID, you wi## app#y a 6#ter to t!e .mp#oyees1indingHource

contro# to #ook for an emp#oyee wit! a matc!ing tag ID If an emp#oyee


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is found, an entry wi## be written to t!e #og 6#e using t!e WriteTo+og%&

subroutine

*ri$ate Hub WriteTo+og% ;

1yCa# emp#oyeeID As Htring, ;

1yCa# emp#oyee7ame As Htring&

S''' write to #og 6#e

Dim str As Htring < emp#oyeeID ;

X,X emp#oyee7ame X,X ;

7ow !r%9&

2yomputerFi#eHystem ;

WriteA##Te3t%FI+.;7A2., str, ;

True&

.nd Hub

Figure 15 s!ows t!e content of a typica# #og 6#e

Figure 15:

T!e content of a typica# #og 6#e

T!e Timer contro# wi## 6re t!e Tick e$ent e$ery t!ree seconds %as

determined by t!e $a#ue set in its Inter$a# property& (ence you need

to ser$ice t!e Tick e$ent so t!at e$ery time it 6res, you can c#ear t!e

current emp#oyee information t!at is disp#ayed (ere is t!eimp#ementation of t!e Tick e$ent

*ri$ate Hub Timer9;Tick% ;

1yCa# sender As HystembMect, ;

1yCa# e As Hystem.$entArgs& ;


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(and#es Timer9 Tick

S''' c#ear t!e emp#oyee

.mp#oyees1indingHourceFi#ter < ;

XTAGID


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5ou are now ready to test t!e app#ication *ress F to debug t!e

app#ication Take a tag and scan it using t!e RFID reader T!e

app#ication s!ou#d register your tag ID and s!ows t!at no emp#oyee is

found %Figure 1$&

Figure 1$:

Hcanning a tag t!at does not be#ong to any emp#oyee

5ou can associate t!e tag ID wit! an emp#oyee by searc!ing for an

emp#oyee %enter t!e emp#oyee ID in t!e Te3tbo3 and c#ick t!e Find

button or #ea$e it empty and it wi## return a## records& nce you !a$e#ocated t!e emp#oyee you want, c#ick t!e Assign Tag to .mp#oyee

button to assign t!e tag ID to t!e emp#oyee

T!e ne3t time you scan t!e same tag, t!e app#ication wi## s!ow t!e

emp#oyee

RFID Reader 8: *!idgetRFID

T!e second RFID reader I wi## s!ow you !ow to use is t!e *!idgetRFID

reader %!ttp://wwwp!idgetsusacom/cat/$iewproductasp

category


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Figure 1': T!e *!idgetRFID

n#ike t!e *ara##a34s RFID Reader 2odu#e, t!e *!idgetRFID uses a H1

connection, w!ic! is actua##y easier for most peop#e since a#most a##

computers today support H1 de$ices And since it draws power from

t!e H1 connection, you don4t need to pro$ide an e3terna# power

source Himp#y connect t!e *!idgetRFID to your computer and start

scanning

RFID Tags

Instead of purc!asing t!e standa#one *!idgetRFID reader, I suggest

you purc!ase t!e *!idgetRFID kit%!ttp://wwwp!idgetsusacom/cat/$iewproductasp

category


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1ui#ding t!e Hamp#e App#ication

Rat!er t!an modify t!e app#ication bui#t in t!e pre$ious section to work

wit! t!e *!idgetRFID reader %and !a$e a #ot of repeating code

snippets&, I !a$e opted to bui#d a simp#er app#ication so t!at you can

#earn t!e fundamenta#s wit!out being bogged down wit! t!e detai#s of

t!e app#ication

sing Cisua# Htudio ??, create a new Windows app#ication and

popu#ate t!e defau#t form wit! t!e contro#s as s!own in Figure 1(

Figure 1(: *opu#ating t!e

form wit! t!e contro#s

sing t!is app#ication, you can $iew t!e tag ID t!at is being scanned

and you can a#so programmatica##y turn on/o- t!e +.D on t!e reader

itse#f and enab#e/disab#e t!e reader

Running t!e *!idgetRFID Web Her$ice

*!idget !as made it easy for 7.T programmers to use t!e *!idgetRFID

reader De$e#opers can contro# t!e reader by t!e *!idgetWebHer$ice, a

component t!at interacts wit! your *!idgetRFID reader 5ou must

insta## and run t!e *!idgetWebHer$ice on t!e computer t!at !as t!e


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*!idegetRFID connected nce t!e *!idgetWebHer$ice is up and

running, your program can t!en communicate wit! it in order to contro#

t!e *!idgetRFID reader 5ou can obtain t!e *!idget #ibrary %containing

t!e *!idgetWebHer$ice& from!ttp://wwwp!idgetsusacom %go to

Down#oads t!en c!oose Re#ease& and down#oad t!e *(IDG.Tmsi 6#e

%o&e: *!idget4s use of t!e term OWebHer$iceK is a #itt#e mis#eading

!ere *!idgetWebHer$ice is not an 2+ Web ser$ice t!at most

de$e#opers are fami#iar wit! Rat!er, it is a Windows Her$ice t!at runs

in t!e background

nce insta##ed, you can 6nd t!e *!idgetWebHer$ice in t!e :P*rogram

Fi#esP*!idgets directory 5ou can in$oke t!e *!idgetWebHer$ice

2anager %a GI $ersion of t!e WebHer$ice& by running t!e

*!idgetWebHer$ice2angere3e from t!is directory nce it is up andrunning, you4## 6nd it in t!e Hystem Tray %Figure 1)&

Figure 1): T!e *!idgetWebHer$ice 2anager in t!e

Hystem Tray

Doub#e'c#ick on t!e icon to #aunc! t!e *!idgetWebHer$ice 2anager

sing t!e manager, you can c!ange t!e settings of t!e WebHer$ice as

we## as manage your *!idget de$ices %not Must t!e *!idgetRFID reader&

As s!own in Figure 2*, t!e *!idgetWebHer$ice is #istening at port

??9 and re"uires a password OpassK %t!e defau#t& in order to access it

Wit! your *!idegetRFID reader attac!ed to your computer, c#ick Htart

In my case, my reader !as t!e seria# number of ?Y, w!ic! can be

used to uni"ue#y identify it

http://www.phidgetsusa.com/http://www.phidgetsusa.com/


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Figure 2*:

T!e *!idgetWebHer$ice 2anager

ne uni"ue feature of t!e *!idgetWebHer$ice is t!at your c#ient

app#ication need not necessari#y be running on t!e same computer as

t!e one wit! t!e reader connected T!e c#ient app#ication uses sockets

communication to ta#k to t!e *!idgetWebHer$ice, so t!is means t!at

you can connect t!e *!idgetRFID reader to one computer and you can

run t!e c#ient app#ication on anot!er computer %as #ong as t!ey can see

eac! ot!er on t!e network& Figure 21 s!ows one possib#e scenario

T!e ad$antage of t!is approac! is t!at your c#ient can be running on

mobi#e p#atform de$ices %suc! as *ocket *& as #ong as it can

communicate wit! t!e !ost computer using sockets communications


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Figure 21: T!e c#ient and

t!e reader need not be on t!e same computer

*!idgetRFID A*Is T!e *!idgetRFID reader, w!ic! is insta##ed w!en you insta## t!e

*!idgetWebHer$ice, e3poses its functiona#ity as A*Is #ocated in t!e

*!idget7.Td## #ibrary

To use t!e *!idgetRFID, 6rst import t!e *!idget7.Td## #ibrary into your

app#ication Rig!t'c#ick on t!e proMect name in Ho#ution .3p#orer and

t!en se#ect Add Reference In t!e 1rowse tab, na$igate to :P*rogramFi#esP*!idgetsP and se#ect *!idget7.Td##

oding t!e App#ication


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Hwitc! to t!e code'be!ind of Form9 and 6rst dec#are a member

$ariab#e representing t!e *!idgetRFID reader:

*ub#ic #ass Form9

Dim Wit!.$ents RFIDReader As ;

*!idgets7.T*!idgetRFID

W!en t!e form is #oaded, instantiate t!e *!idgetReader $ariab#e and

open a connection to t!e computer running t!e *!idgetWebHer$ice

T!is is accomp#is!ed in t!e Form9;+oad e$ent:

*ri$ate Hub Form9;+oad% ;



(and#es 2y1ase+oad

RFIDReader


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*ri$ate Hub RFIDReader;Attac!% ;

1yCa# sender As bMect, ;

1yCa# e As ;

*!idgets7.TAttac!.$entArgs& ;

(and#es RFIDReaderAttac!

S''' disp#ay t!e status

Too#HtripHtatus+abe#9Te3t < ;

X*!idget RFID Reader onnectedX

S''' .nab#e onboard +.D

c!kTurnn+.D!ecked


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*ri$ate Hub RFIDReader;Tag% ;

1yCa# sender As bMect, ;

1yCa# e As ;

*!idgets7.T Tag.$entArgs& ;

(and#es RFIDReader Tag

S''' w!en incoming data is

S''' recei$ed, update t!e

S''' TagID te3tbo3

t3tTagID1eginIn$oke%7ew ;

myDe#egate% ;

Addressf updateTe3t1o3&, ;

7ew bMect%& ZegetTag[&

.nd Hub

T!e de#egate and t!e subroutine to update t!e te3tbo3 wit! t!e tag ID

is de6ned as fo##ows:

S''' update t!e Tag ID te3tbo3

*ub#ic De#egate Hub myDe#egate% ;

1yCa# str As Htring&

*ub#ic Hub updateTe3t1o3% ;

1yCa# str As Htring&

S''' update t!e te3tbo3 contro#

Wit! t3tTagID Te3t


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Himi#ar#y, you can enab#e/disab#e t!e reader by ser$icing t!e

!eck!anged e$ent of t!e c!k.nab#eReader contro#

*ri$ate Hub ;

c!k.nab#eReader;!ecked!anged% ;



(and#es ;

c!k.nab#eReader!ecked!anged

S''' .nab#e RFID Reader

RFIDReaderHetutputHtate%, ;

c!k.nab#eReader!ecked&

.nd Hub

Testing t!e App#ication T!at4s it\ 5ou can now press F to test t!e app#ication .nsure you4$e

used *!idgetWebHer$ice 2anager to enab#e your *!idgetRFID

reader Figure 22 s!ows a tag scanned successfu##y

Figure 22: A tag scanned successfu##y

omparing t!e Two RFID Readers

5ou !a$e seen t!e two types of RFID readers and so w!ic! one s!ou#d

you go for (ere are some factors you can consider

ost

In terms of cost, t!e *ara##a3 RFID reader is $ery a-ordab#e at @B

(owe$er, you need to factor in t!e additiona# cost of wiring up t!e unit

5ou need to buy a power adapter %output C D&, a seria# cab#e, as we##

as t!e additiona# !ardware needed to con$ert t!e signa# to seria#

output In contrast, t!e *!idgetRFID kit costs about @= and inc#udes

e$eryt!ing you need


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.ase of se

In terms of use, t!e *!idgetRFID is tru#y p#ug and p#ay Nust make sure

you down#oad t!e *!idgetWebHer$ice and you can start coding straig!t

away T!e *ara##a3 RFID Reader 2odu#e takes some e-ort to set up,especia##y if you are not fami#iar wit! e#ectronics and worry about

causing damage to t!e unit

F#e3ibi#ity

If you simp#y want to connect an RFID reader to your computer, t!en

t!e *!idgetRFID is c#ear#y an easy option (owe$er, t!e beauty of t!e

*ara##a3 RFID Reader 2odu#e is t!at it a##ows you to connect t!e unit to

de$ices ot!er t!an a *, suc! as an embedded contro##er sing t!e

*ara##a3 RFID Reader 2odu#e, you can embed it in a door and write

your own code to aut!enticate users

Tip: W!i#e at t!e moment, you can4t rea##y use t!e 7.T Framework %or

t!e 7.T ompact Framework& to write code for an embedded

contro##er, I am rea##y #ooking forward to t!e new 7.T 2icro Framework

%!ttp://wwwaboutnetmfcom/entryasp& to a##ow me to do t!e Mob in t!e

near future

Dimension

1ot! readers are simi#ar in si)e, and are ]at enoug! to be !idden from

$iew

Hummary

In t!is artic#e, you !a$e seen !ow RFID works and t!en #earned to bui#d

a Windows app#ication t!at uses two RFID readers'one from *ara##a3

and one from *!idget Depending on your needs, bot! #ow'cost readers

o-er a #ot of e3citing possibi#ities for integrating RFID capabi#ities into

your proMects If you !a$e not tried RFID yet, t!is is a good time to

begin\

http://www.aboutnetmf.com/entry.asphttp://www.aboutnetmf.com/entry.asp


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^Hource: !ttp://wwwatme#com/dyn/resources/*rod;documents/secrerf;

;?>pdf

RFID and 1arcodingHome critics critici)ed t!at RFID is simp#y a more e3pensi$e type of barcoding

tec!no#ogy, since t!e aim is to pick up a number stored on t!e tag %eit!er an

RFID tag or a barcode #abe#& (owe$er, RFID o-ers se$era# ad$antages o$er

barcode:

T!ere is no need for #ine of sig!t for RFID to work For barcoding, you need to

point t!e #aser at t!e #abe# before you can scan its ID

.ac! RFID tag ID is uni"ue A barcode #abe# does not uni"ue#y identify aproduct'it Must identi6es a particu#ar product type

ompanies can use RFID to track t!e w!ereabouts of goods In p#aces #ike

supermarkets, RFID readers can track e3pensi$e goods If an item is remo$ed

from t!e s!e#f, an RFID reader can detect its absence and take t!e

appropriate action

Insta##ing t!e Hamp#e DatabaseHince HQ+ Her$er ?? .3press does not come wit! any samp#e databases,

you need to insta## t!e samp#e databases yourse#f

5ou can insta## t!e pubs and 7ort!wind samp#e databases by down#oading

t!eir insta##ation scripts at!ttp://wwwmicrosoftcom/down#oads/detai#sasp3

fami#yid


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:PHQ+ Her$er ??? Hamp#e DatabasesVs"#cmd 'H PHQ+.*R.HH 'i

instnwnds"#

+i!&i,g 1: Dec#aring member $ariab#es and constants*ub#ic #ass Form9

S'''seria# port to #isten toS incoming data''' *ri$ate Wit!.$ents seria#*ort As ; 7ew I*ortsHeria#*ort S'''tag ID read from t!e reader''' *ri$ate tagID As Htring < ; Htring.mpty S'''t!e time t!at t!e tag ID was

S recorded''' *ri$ate timeRecorded As ; DateTime < 7ow

S'''2 port to #isten to''' onst 2 As Htring


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Wit! seria#*ort *ort7ame


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If %temptagID < tagID& And ; timeInter$a# U I7T.RCA+ T!en S'''if it is t!e same tag and

S t!e time inter$a#S is #ess t!an seconds, t!eS tag wonSt be registered.3it Hub

.nd If

S'''t!e tag is sa$edtagID < temptagID

.mp#oyees1indingHource ; Remo$eFi#ter%&

S'''6nd t!e emp#oyee associatedS wit! t!e tag.mp#oyees1indingHource ;

Fi#ter < XTAGID


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If t3tTagID Te3t UV Htring.mpty ; T!en S'''assign t!e Tag ID to t!e

S current emp#oyee TagID+abe#9 Te3t


36/36

+it%e +e,t-o,

hoto ictu!e-o,

+g/' +e,t-o,

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A Quick Introduction to RFID

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