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