presentation - university of illinois at urbana-champaign

RFID Checkout Line

12Team

Xin Henry Fang Calvin Hsieh David Yi

RFID Checkout Line• - Purpose Using RFID technology to

eliminate the need of scanning. barcodes

• - Motivation all experienced long lines and wait times in public convenience

stores

:Benefits , Customer convenience time saving process

Better inventory management Further the application of RFID technology

:Features• RFID tags for item identification• - - Ultra High Frequency RFID reader• Antenna selection for optimal read

/ range tag orientation compatibility• Organized PCdisplay of scanned items with

running total• - Quick self checkout system

Objectives Maximize reliability and customer convenience

• 2 Read multiple tags at up to feet consistently without error• Reasonable amount of flexibility with angle and orientation of tags• , Associate tag IDs with item name description and price• , , Integration of reader PIC and PC• Constantly refreshing display of current items detected• Allow customer to add or remove items while at checkout• Minimize time to detect an item addition and item removal• Customer confirmation of final price

Block Diagram

• 9 Skyetek©M RFIDreader

862-955 UHF MHz

1-3 m read range• 2 Gen Protocol RFID tags

-best range and anti collision• 16 877 Microchip F APIC• 232 MAX chip• -232 RS serial port communication• PCmonitor display

Antenna RFID Tag

RFID Reader

Power Supply

Display

Memory Management/Microprocessor

Initial Hardware Test Setup

Protoboard was the primary tool that was used for testing and

debugging

Used for functionality of Individual components as well as

communication betweencomponents

232 RS PICto PC

232 RS Reader to PIC

Power Supply

MAX232

20Mhz Oscillator

PIC

Final Hardware Overview

PIC

232 RS PICto PC

232 RS Reader to PIC Power Supply

MAX232

20Mhz Oscillator

PIC

5 , , Power supply v to PIC Oscillator 232and MAX

232 : RS Reader to PIC feeds both tx and rx lines

232 RS PICto PCconnector tx to PC

232 MAX to step down voltage from Reader to PICand step up voltage

from PICto PC

Microchip PIC/RFID Reader Communication

9 Skyetek M RFID Reader• -232 RS TTL communication• : 38400 Baud Rate bps• : 27 Output Power Level dBm

16 877Microchip PIC F A• -Programmed in PIC C• -232, 2 , Supports RS I C SPI protocols• 20 Operates at MHz

Skyetek Communications Protocol v3

( ) :Request Command Format

: [ ][ ][ ]Basic Inventory Command Option Flags Command Tag Type

, , , Supports commands such as Inventory Kill Tag Write Tag Set password

( ) :Response Received Format

: [ ][ ][ ][ ]Basic Inventory Response Command Tag Type Tag ID Success Flag

Programming the Tags

Tags came pre-programmed with the same EPC ID’s

•Memory of the PIC was a problem – PIC only has ~3KB of RAM, while incoming RFID responses were 320 bytes each

•Needed to re-program the ID’s to be unique, but also allow the PIC to ignore storing all incoming characters except for the ones in the unique ID’s.

•Used ‘Write Tag’ command (0x0103) to re-program tags to ID range from ASCII “EEEE” to “FEEF”

Requesting Tag Inventory

PIC sends ASCII Inventory Select command: <LF>[0002][0101][8200]<LF>

•Tells reader to look for all Gen2 tags with in the field with unique ID’s

•Command is looped periodically, with about a 50 ms delay between successful responses.

-Allows the display to update in the case of an erroneous reading or if the shopper wants to add or remove items to their cart.

-No user intervention is required to continue scanning/sending info

Inventory Request Snapshot

Inventory Response Snapshot

Request Command

Tag ID’s

Request Complete Flag

Tag Request Interrupts

’ PICdoes not know how many tag ID s will be coming in• 10 , ’ Will try to read a maximum of tags even if there s less in the field• Interrupts are used to prevent PIC from waiting endlessly for data• ’ 8- , 256, Using the PIC s internal bit counter and a prescale factor of interrupt

timeout length set to 0.131 secs

Processing Received Information

After receiving ID’s, PIC performs ID matching to send to PC.

• PIC converts the tag ID’s read into an ASCII encoded string to send to the PC for checkout display.

• User intervention not required – PIC periodically sends this data out

8 Send “Mario Party ” encoding“FEEE”4

Send “Katamari Damacy” encoding“EEEF”3

Send “God of War” encoding“EFEF”2 Send “Kingdom Hearts” encoding“EEEE”1

Action Read Tag IDTag #

Received Tag ID Snapshot

Tag ID’s

Inventory Complete Flag

Testing of PIC to PC Initial PICto PCImplementation

• / Plan to have all calculations database performed on the PIC

:Problems• Limited PICmemory• HyperTerminal is a very simple tool

Constantly refreshes itself Data cannot be edited

Final Implementation• Raw Data sent to PCfrom PIC

Implement “Checkout” Screen in Visual Studios using Visual Basic

: Benefits Allows input data to be manipulation to store

information and perform calculations

: Problem Distinguish between individual tags

: Solution Pass a constant unique 8- string of bytes that represents

(00000000,…each tag99999999, where FFFFFFFF is

)garbage

Visual Studio Programming• Contains database of tag IDs

and associated item information• Processes received data from PIC

and determines which items are in the checkout line

• Calculates totals• Displays items and prices on

screen• User interface to confirm final

price

Quality Control

YesNoYesYesPrevious response →

YesNoNoYes2nd to last response →

YesNoYesYes3rd to last response →

Tag 4

Tag 3

Tag 2

Tag 1

• , Reader does not always detect every tag especially as range and number of tags

increase

• Implemented quality control checks using .previous responses to avoid errors

• Varied the number of previous responses to, , check “m” in order to optimize the

reliability without introducing too much delay in detecting the removal of a tag

• …More on this later(m=3)

Overview of Testing

/ -Readability Anti collision• # . (1,2,3,4) of tags read vs incremental m values and distances

(0.5, 1.5, 3 ) ft• ( , )Tag Orientation fanned directly behind

:Angle• . Read range vs AngleSubstrate

: Timing• . Mvalue vs Tag Removal Detection Time• . Interrupt Timeout time vs Tag Removal Detection Time

-Analysis of Anti collisionEffect of 'm' on Read Success (Dist 0.5 ft, tags fanned/spread out)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0 1 2 3 4 5 6 7 8 9 10

Number of Tags in Field

Su

cc

es

sfu

l re

ad

s (

ou

t o

f 1

5)

m=1

m=2

m=3

m=4

Effect of 'm' on Read Success (Dist 0.5ft, Tags directly behind each other)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0 1 2 3 4 5 6 7 8 9 10

Number of Tags in Field

Su

cc

es

sfu

l R

ea

ds

(o

ut

of

15

)

m=1

m=2

m=3

m=4

Comparison of Orientations on Read Success (Dist 0.5ft, m=3)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0 1 2 3 4 5 6 7 8 9 10

Number of Tags in Field

Su

cc

es

sfu

l R

ea

ds

(o

ut

of

15

)

Spread orientation

Not spread orientation

Effect of 'm' on Read Success (Dist 1.5ft, Fanned Orientation)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0 1 2 3 4 5 6 7 8 9 10

Number of Tags in Field

Su

cc

es

sfu

l R

ea

ds

(o

ut

of

15

)

m=1

m=2

m=3

m=4

Effect of 'm' on Read Success (Dist 1.5ft, Non-spreaded orientation)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0 1 2 3 4 5 6 7 8 9 10

Number of Tags in Field

Su

cc

es

sfu

l R

ea

ds

(o

ut

of

15

)

m=1

m=2

m=3

m=4

Comparison of Tag Orientation on Read Success (Dist 1.5ft, m=3)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0 1 2 3 4 5 6 7 8 9 10

Number of Tags in Field

Su

cc

es

sfu

l R

ea

ds

(o

ut

of

15

)

Tags spreaded

Tags not spreaded

Read Success vs Number of Tags with Spread Orientation (Dist 3ft, m=4)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0 1 2 3 4 5 6 7 8 9 10

Number of Tags in Field

Su

cc

es

sfu

l R

ea

ds

(o

ut

of

15

) o

f 1

5)

Spread orientation

Angle Testing Orientations

Max Read Distance vs Angle (single tag, m=1)

0

5

10

15

20

25

30

35

40

45

50

55

60

65

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

Angle (degrees)

Ma

x R

ea

d D

ista

nc

e (

inc

he

s)

Angle Type 1

Angle Type 2

Angle Type 3

Angle Type 4

Effect of substrate on max read distance(one tag, m = 1, optimal orientation)

0

10

20

30

40

50

60

70

Air

Paper

Cardbo

ard

Phone

Boo

k (th

ick pa

per)

Plastic

(vide

o gam

e ca

se)

Jans

port

Backp

ack

Met

al (p

artia

lly b

lock

ed)

Met

al (ta

g abo

ut 4

in be

hind

)

Liquid

(wat

er b

ottle

)M

etal

Met

al+Li

quid

(Spr

ite ca

n)

Substrate placed in between antenna and tag

Max

imum

rea

d di

stan

ce (

inch

es)

Effect of M on time to detect a tag removal(I.T. = 0.131 sec)

0

1

2

3

4

5

6

7

8

9

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

m (number of insurance loops)

Rem

ova

l d

etec

tio

n d

elay

tim

e (s

eco

nd

s)

Effect of interrupt timeout on time required to detect tag removal (m = 3)

0

2

4

6

8

10

12

0 0.05 0.1 0.15 0.2 0.25 0.3

Interrupt timeout per tag (seconds)

Rem

ova

l d

etec

tio

n d

elay

tim

e (s

eco

nd

s)

Successes

Introductory proof of concept for checkout lines

( 60 . )Overall system has satisfactory range as much as in for a single tag

- 10 , 5-6 Anti collision up to tags working quite well for items

, - Elegant store like display capable of displaying all items at once including , , price sums unique descriptions and error checking enhancement

Permanent boxed enclosure for circuitry

Improvements

/Goals Improvements• Expand the total number of allowable tags• Multiplexed array of antennas for larger

interrogation zone• Antenna amplifier for longer read ranges• Metal Shield to act as an RFwave reflector• Inventory database• Interface with Credit Card machine and Receipt

Printer

Ethical Considerations

• , Shoplifting issues if tags could be ripped off but tags .could be embedded

• Shoplifting detection could be implemented at store exits . similar to existing security measures Tag IDs could be

.overwritten or turned off when payment is confirmed

• , . , Invasion of consumer privacy what you buy However information could aid companies in more effectively

.targeting advertisements and avoid spamming

:Special Thanks To

• Professor Carney• Alex Spektor

• .Skyetek Inc• Parts shop

Questions