CA1330367C - Shopping cart position sensing system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A shopping cart display system and position sensing system includes a cart mounted display that is responsive to trigger signals provided by transmitters associated with a particular location. When the display receives a unique trigger signal, it displays advertising media associated with that location. In one embodiment, the display includes a sensor for determining whether the information is displayed in the presence of a consumer, and a memory for storing all trigger signals received during a given shopping trip. The stored data is transmitted to a polling transceiver located at a point of sale register for later analysis and gives a log of all locations that the cart has visited.

Description

~L33~3~

This application relates to a shopping car.
display system and a position sensing system for such shopping carts.
This applica~ion is a divisional application of applicant's co-pending Canadian application serial No. 616,243, filed December 2, 1991 which is a divisional application of application serial no.
578,071 filed September 21, 1988.
Consumer purchasing behavior may be influenced at different times in the purchase-consume-purchase cycle. For example, some grocery stores, in an attempt to influence future purchases, employ video screens located at checkout stations to display advertisements and offer coupons based on the items being purchased by z particular consumer. This type of system has not been entirely successful because the time of the advertisement's maximum influence on the consumer, i.e., during checkout, is temporally furthest from the time that the consumer can respond to the coupon or information.
Because the individual consumer has just completed his purchases, it may be a relatively long time before he is in the store again.
Television advertisements, newpaper coupons and feature advertisements also influence the consumer during the middle of the purchase-consume-purchase cycle. Again, the effectiveness of these promotions varies with the time between the consumer's receipt of the promotional information and his next shopping trip.
In-store display~ are more effective in influencing consumer purchases since they are encountered more or less contemporaneously with the actual item -1- : `
sd/sp ~ ~

selection process. One type of in-store display, i.e., point-of-purchase (POP) displays, tend to be physically fixed displays that promote a single product or group of products and must be changed periodically by store personnel, a time consuming and costly task.
Another type of in-store advertisement is the fixed paper placard attached to the front of shopping carts. As with POP displays, the placards must be changed periodically.
Effectiveness of the placards is also limited, because they are quickly obscured by groceries as the cart is filled.
It is therefore a feàture of the invention to ~ `
provide an advertising system that optimizes the effect of - .:
product advertisements by presenting the information just before the consumer is ready to make a purchase and which jc overcomes the limitations of known in-store promotions.
It is also a feature of the invention to provide a ;
system for determining the position of a shopping cart within a retail establishment.
SUMMARY OF THE INVENTION ~ ;
The invention overcomes the disadvantages of the prior art by providing the consumer with dynamically changing advertisements and information that influence the consumer at ~-the place and time of product selection and using portions of the same system to follow the path taken by a shopping cart.
Specifically, the invention relates to a system for determining the position of a shopping cart within a retail establishment comprising: means at a first location in the `
retail establishment for transmitting a position signal; ~
means associated with the shopping cart for receiving the `
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~33~7 2a position signal; means for generating positional data from the position signal, wherein the positional data is representative of the position of the shopping cart within the retail establishment; and means for storing the positional data.
The Shopping Cart Display ~SCD) System is a media system capable of delivering visual and aural messages to a consumer maneuvering a shopping cart through a store.
Specifically, an electronic display device mounted on the cart can deliver unique messages depending on the location of the cart in the store. For example, if the consumer is in the bread department, a bread advertisement can be delivered.
The display may also be mounted on hand-held shopping baskets present in many stores for those consumers intent on purchasing only a few items. In the presently preferred embodiment, the display has a number of additional features.
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It can deliver news and information, interact ,:

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~ 3 ~ 7 with the consumer to distribute electronic coupons, play electronic games for entertainment and education, or perform convenience functions for the consumer such as budget management.
The electronic messages displayed in the store may originate at a composition workstation located in a remote studio or at a message creation workstation located in the store. The message may contain text, including botll still line and pictorial artwork along with full motion video, graphic messages, and audio, including speech, music or attention alert tones. In the presently preferred embodiment, a series of Universal Product Code (UPC) numbers, a unique ad identifier, and other data are included with the message.
The messages are sent from the studio via a `~ -communications network to a particular store or series of stores. SCD system computers located in particular retail establishments store messages that are intended for that location. The retailer can also compose and insert local (store specific) ads into the stores SCD
computer which transmits the active messages to all of ~
the SCD displays located on the store's carts. Each~ `
SCD stores messages for subsequent display.
Throughout the store at various locations are transmitters mounted on the shelves, or where shelves do not exist, on any convenient structure, e.g., hung from the ceiling. Each transmitter radiates a uni~ue electromagnetic signal that causes the SCD electronics to display, either immediately or after a time delay, the advertisement corresponding to that signal. In this manner, the transmitters act as signposts to inform the SCD of its location and orientation.
Consequently, a bread ad is displayed while the consumer is in the vicinity of the bread section, and a cereal ad when he is in the vicinity of the cereal section, etc.

. ,:, ~33~3~7 The features and advantages of the invention will be further understood upon consideration of the following description of the preferred embodiment taken in conjunction with the drawings, in which:

BRIEF DESCRIPTION OF EIE DRAWINGS
FIG. 1 is a block diagram of a presently preferred embodiment of the SCD Media System.
FIG. 2 is a bloclc diagram of the message composition workstation.
FIG. 3 is a block diagram of the studio and billing control computer. `~
FIG. 4 is a diagram of the in-store . - . ,.
components.
FIG. 5 is a block diagram of the message refresh transmitter.
FIG. 6 is a block diagram of the trigger transmitter. '~~
FIG. 7 is an ideal trigger-transmitter zone coverage.
FIG. 8 is a practical trigger-transmitter zone coverage.
FIG. 9 shows the physical configurat.ion of the display and cart.
FIG. 10 is a block diagram of the cart-based electronics.
FIG. 11 is a detailed block diagram of the trigger transmitter.
FIG. 12 shows the trigger transmitter power cycle.
FIG. 13 shows tlle format of characters used in the SCD Media System.
FIG. 14 shows the trigger transmitter trigger transmission format.
FIG. 15 is a flowchart of tlle trigger ~ :
transmitter software.
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-: 133~367 FIG. 16 shows the orientation of the trigger transmitter antenna and the trigger receiver antenna.
FIG. 17 is a bloclc diagram of the trigger receiver and response transmitter.
FIG. 18 is a block diagram of the pol].ing transceiver.
FIG. 19 shows the format of a transmission bloclc sent by the polling transceiver to the tric,~ger , '~
receiver. ,"`'~' FIG. 20 shows the format of a transmission block sent by the response transmitter to the polling transceiver in response to a poll request. " ~, FIG. 21 shows the format of a transmission block sent by the response transmitter to the polling transceiver in response to a log dump re~uest. , `' , FIG. 22 shows the format of a transmission~ , ' block sent by the response transmitter to the polling transceiver in response to a clear log request. :'`
FIG. 23 is a flow chart of the foreground task performed by the SCD microprocessor.
FIGS. 24A-D are flowcharts of the subroutines called during the foreground taslc performed by the SCD
microprocessor. ~, FIGS. 25A and B are flowcharts of routines performed when a motion sensor, a halldle sensor, a ':~
keyboard, or an activity watchdog timer in-terrupt occurs.
FIG. 26 shows an example of a message refresh transmission by the tnessage refresh transmitter. ,~
FIG. 27 shows the message refresh transmitter bloc]c type values. -FIG. 28 shows the format of a message refresh ;
transmitter header.
FIG. 29 shows the format of a message refresh ' ~ `
transmitter data block. ,~

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FIG. 30 shows the format of a message refreshtrallsmitter cloclc set command.
FIG. 31 shows the format of a message refresh transmitter power-down command.
FIGS. 32A-E are flowcharts of a portion o~
the message refresh reception software.
FIG. 33 is a flowchart of another portion of the message refresh reception software.
FIGS. 34A-D are flowcharts of another portion of the message refresh reception software.
FIGS. 35A-C are flowchar-ts of another portion of the message refresh reception sof-tware.
FIGS. 36A-D are flowcharts of a portion of tlle trigger reception software. .
FIGS. 37~-C are flowcharts of another portion of the trigger reception software. ~ -~
FIGS. 38A-E are flowcharts of another portion of the trigger reception software.
FIG. 39 shows an example of a trigger ;
reception log entry.

DESCRIPTION OF A PRESENTL~
PREFERR EMBODIMENT OF_THE INVENTION
FIG. l is a diayram of the Shopping Cart Display (SCD) Media System. Eleetronic messages are created on computer worlcstations loeated at a central studio 103. Alternatively, the messac3e may be c3enerated at an advertising agency lno, a manufacturer 101, a xetail chain headquarters 110, or at any other location that is ec~uipped with a compati.ble woI]cstation. In ~
this event, the completed ads can be communicated to ~;
the central studio 103 via floppy disk, macJnet:iC tape, -`
modem and te].ephone line, satellite network, etc. 102.
Also, workstations may be equipped with a display that simulates the cart-based display electronics. This ~33~67 allows newly created ads to be tested in a real-life situation to judge their visual and aural impact and appropriateness. Additionally, local messages c:an be created directly at the selected retail store 107. The ability to create ads at the store allows the store manager to insert his OWII store-specific messages (e.g.
store welcome messages, manager's specials, dai]y specials, close-out sales, etc.).
The central studio 103 attaches additional ~ -information to ads received from remote workstations 100, 101, 110 in anticipation of sending the ad over the communica-tion network to a specific store or stores. The information may include the ad "flight"
(starting date and time-stopping date and time), a list of store network addresses, the Universal Product Codes (UPCs) or article numbers associated with the ad, and a unique ad identifier.
The message and added data are sent via a bidirectional bus or link 104 to a communications ~ -networ]~ 105 which may be located in the central studio 103 or elsewhere. The network routes the messages and data over a bidirectional link 106 to an appropriately addressed store or chain of stores 107. The unique addressing allows complete flexibility in distribution of messages. Return data from the stores 107 may be sent back to the studio 103 via the communications network 105 and links 104, 106.
At a particular store, the meSsacJes are forwarded to SC~ electronics 514 mounted on all product~
carrying devices, such as shoppiIlg carts and hand-held : -shoppiIlg baskets. Any subse~uent references to shoppingcarts includes all product-carrying devices. The SCD
electronics keep the messages in memory. When a cart is in the proximity of a trigg~r transmitter, an appropriate message 10~ is d:isplayed to the cons,umer ~3~67 109, either immediately, or after a time delay. The -message 108 is determined by the composition of the trigyer signal and previously enco~lntered trigger sign~ls.
FIGURE 2 is a block diagram of the message composition workstation located, for example, at central studio 103. It is based on a personal computer 300 with a hard d.isk drive and at least one floppy disk drive, a standard display device 301 (e.g. a Cathode Ray Tube (CRT)), and a keyboard 302. Eor ease of graphic image entry, an optional copy camera with digi-tizer, or document scanner 303 can be attached.
For ease of-graphic image editing, an optional pointing device (e.g., mouse or light pen) 308 can be attached.
An optional display device 304 which emulates the SCD
electronics present on the carts in the retail stores may also be attached to the computer 300. The display emulator allows messages to be presented in the exact way that they will ultimately be presented in the store (video and audio). The last optional hardware is a telephone modem 305 that allows networking with a studio billing computer for transfer of completed mes~ages 306. Alternatively, messages may be ~ransferred by manually transferring floppy disks 307 :
to the studio b.illing computer. `-The software operating on the personal computer 300 preferably includes a graphics image editor which allows composition of graphics and text messages, graphics image capture via copy camera or document scanner 303, graphics animation, audio composition, and image storage and retrieval. The -software also includes a program for driving the display emulation hardware, and for compressing the -~
completed messages before transmission via flopp~ disk ~33~7 307 or modem 305, 306. Messages can be compressed via several means: one dimensional rull l.ength encoding or two dimensional Relative Element Address Designate (READ) coding (similar to the CCITT Group III and IV
diyital facsimile standards); conversion to North American Presentation Level Protocol Syntax (NAPLPS);
conversion to PostScrip-t or PreScript; conversion to `
Initial Graphics Exchange System (IGES); conversion to Electronic Design Interchange Format (EDIF); or conver-sion to the Graphic Kernel System (GKS).
FIGURE 3 is a more detailed diagram of central studio 103 and an associated billing computer `~
sys-tem. The studio includes a series of message :
composition workstations 401 tied together in a known manner with a Local Area Network (LAN) 402 to facilitate production of SCD system messages. The LAN 40~ connects all of the work stations to the billing and control comp~lter (BCC) 400. After messages are composed, they are transmitted to the BCC. Messages composed a.t off-site work stations are received via telephone modem 405, floppy disks and magnetic tapes 406. Other inputs to the BCC are time and date via a radio-coordinated clock 407, local terminals for advertising account exec~l~ives 408, and external data sources 409 such as United Press International, Dow Jones data services, Silent Radio , etc. The BCC has local disk storage 403 and printer facilities 404.
The BCC operating software accepts SCD system messages, attaches additional data to the messages from -~
the local data base, prints acknowledgm;ents of the ~ -messages for verification of off-site clients and account executives, and, based on information retrieved from the data base, forwards the messages on for distribution to the stores via a Wide Area Network ' ' ,: :
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(WAN). The messages are also logged for client billing and co].lections purposes.
Several cycles of start and s-top dates and timei-i can be loaded into the data base of the BCC to automatically sched~lle an advertisement's "flight" and "hiatus" durations. This can be loaded via the work-stations or the local terminals by the account execu-tives.
The data base resident on the BCC also contains games and information that is periodically downloaded via the WAN into computers located in the stores and subsequently into the display devices on the carts. The BCC software also accepts data returned from the stores to the studio vla the WAN.
The WAN may be constructed of many technologies or combinations thereof such as direct satellite links, terrestrial microwave links, Multiple Address System (MAS) radio frequency links, subcarrier links from FM
broadcast stations, fiber opti.c links, laser optical links, Integrated Services Digital Network (ISDN) offered by phone companies, T1 serv.ice offered by phone companies, dedicated phone lines with modems, dedicated phone lines with line drivers, conventional non-dedicated dial-up telephone lines with modems, or other means, as techllology advances.
The WAN ro~tes individual messages to the ~;`
inclividual retail s-tores or c3roups of stores based on addressing information contained in the messages and the s~ore address loaded into each of the SCD in-store computers. Each store has a ~Inique address. The `~
address consists of two parts, a chain address and a store address within that chain. The WAN also handles broadcast messages (i.e. messayes that are to be received in a].l stores connected to the WAN.) The time `~
and date are examples of messacJes that may be received by all of the stores.
-- 1 0 -- ' ' .''~' -- ~3~67 The WAN also routes return information from the stores to the studio in a manner known in the art.
FIGURE 4 shows the in-store components of the SCD System. The communication device 501 interfaces to the Wide Area Network. FIG. 5 depicts the c~mmunication device as a satellite dish for interfacing with a satellite-based WAN. Whatever hardware or transmission link is used, device 501 would include associated demodulating circuitry to convert the incoming signal into computer readable form. If the WAN is to be bidirectional, device 501 must also include modulation and transmitting capabilities. Devices of this type are well known in the art. Messages for the store 107 arrive on link 518.
The SCD System In-Store Computer (~SC) 502 compares the address of each message to its own uni~ue ~`
address. If the address matches or if the message is a broadcast transmission which is destined for all stores, the ISC accepts the message and opti~nally spools it to local nonvolatile storage such as battery- ~-~
backed Random Access Memory (R~M) or disk.
A message that is to be displayed on the ` -SCD electronics 514 is merged with data from the local ~
data base present in the ISC. This data base contains ~`
trigger transmitter (TT) 512 shelf location lnformation.
This data base is kept current by store personnel. The Universal Product Codes (UPCs) or article numbers associated with the message may be checked v~a the in-store scanning system 510 to ensure that the advertised products are presen-t in the store.
Locally generated messages may be created by a local workstation 506 (optional) and transferred to the ISC 502 via link 507. This allows the store manager -to create à message to welcome shoppèrs -t:o his ~;

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~ ~ 3~3~7 store, and advertise the stores monthly, weekly, daily or hourly special, along with any special promotions in the meat department, delicatessen, bakery, etc. The store manager edits a data base in the ISC to control the locally generated ads' flight and hiatus.
Other local store data can be input to the ISC 502 via the link 508. In the preferred embodiment, the ISC contains a "product look-up" table that enables consumers to find a particular product by making the appropriate selection at the SCD electronics keyboard. ;-In addition, data showing which ticket number is currently being served in the deli, the winning state lottery numbers for the day, and local news or financial '~
information may also be displayed on all the carts in ``~
the store. Public service information such as weather warnings, may also be entered into the ISC and transmitted to the SCD's. Other uses including ones similar to an audio public address system may be made of the SCD. In addition, the SCD's provide an interactive store directory. ':~ ~.
To make the wait in line at the checkout ~ ~
counter appear shorter, the SCD can be used to play ;-games. Trivia games, brain teasers, hangman, etc. can -~
be played. The games are loaded in the ISC via the WAN `; `~
or locally via the composition workstation 506.
Consumers interact using the cart-ba'sed di.splay and ;;~
overlaid keyboard described below.
All data required for SCD system operation is sent s-torewide by the ISC to the SCD electronics 514 present on all the carts by the Message Refresh Transmitter (MRT) 503. The MRl' transmits radio signals -~
containing the messages (depicted at 504). A Message '~
Refresh Receivers (MRR) Subassembly 1317 (FIG. 13) on each of the carts 514 receive -t:he message signals from the MRT. The signals are then converted into digital messages. If the messages are to be displayed only when triggered, they are stored in a memory in the cart. If the messages are for immediate display and the cart is active (recen-tly in mot:ion) the message is uncompressed and displayed.
Mounted below the shelves are a large number of Trigger Transmitters (TT) 512 located throughout the store in all categories and departments. In aisles where shelves are not present (i.e. soda pop, meat, frozen foods, etc.) TTs can be hung from the ceiling or otherwise located in the vicinity of the product;. TTs .~.
transmit at a very short (approximately 1%) duty cycle ~ -to conserve their battery power. Each TT in a given store has a unique address which it transmits ac; part of its trigger message.
When the SCD cart-mounted electronics 514 receive a valid trigger transmission 513 of adequate amplitude (i.e. the cart is within the trigger trans~
mitter zone), it searches its memory for any message with the corresponding trigger address. If an address match is found, the message associated with that~ f~
. . ~
address is displayed either immediately or after a -time delay. This is how a bread message (advertisement) is displayed in the vicinity of the cereal section, etc.
In the presently preferred embodiment, the SCD
electronics 514 log all received triggers and the displayed message directs the consumer's attention to ~ ~
the left or right depending UpC)II which trigger signals ~ ;
have previously been encountered.
The SCD electronics 5l4 stores every valid unique trigger transmission and the date and time that it receives it as the cart traverses the store to form a log of all the places thatt -the cart has been. This log is uploaded to the In-Store Compu-ter 502 during checkout at point-of-purchase station 515. Located at .~ ~ ,:.;;

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~33~67 the station 515 is a polling transceiver 516, the elec-tronics of which are identical to -the SCD transceiver electronics 514 except that the data processing is done by the ISC computer 512 which receives data from transceiver 516 via linlc 517. The log is then cleared in anticipation of the next shopping trip. The data is :~ .
merged with the Trigger Transmit-ter location -information and up loaded to the studio for analysis. ` `
Consumer surveys can be conducted via the scn system. System messages in the form of questions are composed and transmitted to the SCD electronics. ~ -Consumer responses are entered Oll the keyboard and logged in memory on the cart. These responses are up -: , ..: .
loaded from the cart to the lSC during chec}c-out time 515, 516, 517 and ultimately returned to the studio.
The Trigger Transmitters (TT) 51~ are easily attached and removed from the shelves. Thi.s facilitates easy TT ex~hange, relocation and bat~.ery replacement by store personnel. When the items on the shelves are relocated, the TTs must be relocated also.
Store personnel must keep the TT location data base resident in the ISC 502 up to date.
Batteries in the SCD cart-based electronics are recharged by a battery recharging system 505. This can be accomplished, for example, by an inductive pick-up (electric transformer secondary coil) moullted in the cart. A corresponding inductive transm:itter (electric transformer primary c:oil) can be mounted in the cart storage area. When the cart is in storage, recharge energy will be magnetically transferred to the cart. An electrical contact could also be used to ~`
transfer energy into the cart. While in storage, an electrical contact mounted on the cart would connect with a corresponding contact mounted in the storage area to transfer energy. Photovoltaic cells (i.e.
solar cells) can provide recharge energy vi.a ambient :

~33a~s7 light, sun light, a2ld auxlliary lighting placed over -the cart storage area. A wheel generator could also be employed to conver-t energy from the mo-tion of -the cart.
In the presently preferred embodiment, the discharged battery packs are easily removed and exchanged with recharged ones by store personnel. The spent packs are placed in rechargers in anticipation of the next exchange.
FIGURE 5 is a block diagram of the Message~ ~-Refresh Transmit-ter (MRT) 503 which receives data stream 600 from the SCD In-Store Computer (ISC) 502. :~
The MRT consists of frequency shift }ceyed (FSK) modulator 601, this mod~llates the incomiIlg data in a manner known to the art at VHF frequencies. The modulated si.gnal is ~ :
transmitted throughout the store by an RF transmitter 602. The MRT VHF Transmissions are authorized ~Inder FCC Part 90.267 "ASSIGNMENT AND USE OF 12.5 KHZ FREQUENC.Y
OFFSETS". Since the MRT is continuously transmitting to refresh the message stored in the carts, batteries wi].l not work as a power source for -the MRT. It is powered by the alternating current (AC) power mains 605 via power supply 604. ~ ~
Alternatively, the MRT transmissions 603 ~ ~;
could be via low-frequency radio-fre~uency (LFRF) transmissions, microwave radio-freql~ency transmissions, or infra-red (IR) transmissions, or other FCC Part 90 authorized transmissions.
FIGURES 26, 28 and 2~ show an example of an ~ -MRT data transmission. The MRT continuously re~eats a ~ ;
series of data frames 3001. Each data frame consists of a header block 3003 and a series of data blocks star-ting with block 1 3005, and ending wi-th block N
3007. The header includes idle time 3201 followed by a flag byte 3202, and a length indicator 3203. The ~33~7 ` ~
length indicator tells how long the complete header block is. Next comes a block type indicator 3204. It :~
indlcates whether the next data is part of a header ~-~
block 3003 or a data bloc~{ 3005, 3007. Next an SCD
message number and version number 3205, an indlcator of -the number of subsequent data blocks 3206, and finally --an error detection check sum or cyclic red~lndancy chec}c (CRC) 3207 for verifying the integrity of the block.
The SCD cart-based electronics 514 listens to tlle header and makes a decision during the idle time `~
3301 following the header 3003 a part of the following data block 3005. It irst computes the check sum or CRC for the headèr and compares it to the transmitted check sum or CRC 3207 to determine that the header is valid and error free. If the header is valid, the SCD
then checks the message number and message version 3205 against the message version numbers it has stored i.n ~` `
memory already. If there is a match, the SCD has previously stored the message that is in the following data blocks 3005, 3007 of the current frame. The SCD
can turn off the MessacJe Refresh receiver and 'Icfo to sleep" (to save battery life) during the remainder of this da-ta frame. It knows how many data blocks are in the current frame from the header information 3003. It can measure the transmission rate and calc~late the time duration of the rest of the current data rame.
It then sets and starts a timer that will "wake upll the SCD electronics in time to read the next header. This minimizes the power consumption of the cart-based electronics to maximize battery life.
If the message number and version number do not match any message numbers or version numbers in memory, the SCD reads and validates the remain:ing data ;~

.':

~3~67 blocks 1 3005 through N 3007 of the current frame and loads them into memory. It then continues with the next data frame and header.
FIGURE 6 is a block diagram of the Trigger Transmitter (TT). The Transmission Controller 800 `~
contains a unique TT address, and a power se~uencer. -~
The data modulator and transmitter 801 generate modulated low-frequency radio-frequency (LFRF) energy that is coupled to the antenna 802. ~ ~
All antennas generate both an electric (E) `
and magnetic (H) field. In the far fiel.d (approximately 5 wavelengths away from -the an-tenna) the E and H fields obey a fixed relationship that is independent of the type of antenna. In the far field region, the energy falls off as an inverse function of the distance squared. In the near field (less than 5 wavelengths~, the energy falls off as an inverse function of the distance cubed. The presently preferred embodiment operates in the near field to take advantage of the inverse cubed rolloff in energy to control the size of desirecl zone vs the zone of interference to adjacent trigger transmitters. In particular, the system employs a small loop antenna 802 which acts like a magnetic dipole to create a large H
near field component. A similar magnetic loop 2101 antenna mounted within SCD electronics 518 is employed -to receive the signal. In this way the two antennas are coupled not unlike the primary and secondary coils of a transformer when they are close to each other.
(See FIGURE 20.) The cart-based receiver responds primarily ~ `
the magnetic component of the field 803. When the cart receiver antenna coil is in proximity of the trans~
mitter antenna coil, the coils are magnetically coupled ~:

';
~ 3 ~ 7 ~ :
and act as a trans~ormer. The transmitter coil ac-ts as the primary winding aIld the receiver coil acts as the - ~ :
secondary winding. Both coils are oriented with their maill axis in the vertical pOSitiOIl for more rapld -~
dropoff of the coupling.
FIGURE 14 shows an exemplary Trigger Transmitter (TT) message. Most of the time the transmitter is powered down to conserve battery energy.
The transmission controller 800 is always powered up `~ -and running. ~fter a predetermined off time, for example 5 seconds, the transmission controller 800 powers up the data modulator and transmitter 801 and begins transmitting the idle 1802. During the idle 1802 the transmitter circuits and the receiver automatic gain control circuits (AGC) stabilize. By the end of the idle 1802, the receiver is ready to receive message data. Next a preamble 1804, a flag indicator 1805, a length indicator 1&06, a block type ~ `
indicator 1807 (indicating that this is a trigger block), a unique trigger transmitter address and battery status indicator 1808, and a CRC for message validation 1809 is sent. Then a postamble (i.e. idle) ~
1810 is sent. The trigger block ].803 is repea1:ed three ~; i more times. At the end of 1810, the transmission sequencer 800 powers down the data modulator arld transmitter 801 and begins timing tl~e of d~ral:ion ayain. When the time-out elapses, the whole message ;
sequellce is repeated.
During the Trigger Transmi.tter idel 1802, the cart-based receiver AGC stab:ilizes and the received siyllal strength is measured against an adaptive reference based on the AGC voltage. If the signal strength i3 below the reference, the rest of the message is ignored. If the signal strength is above - 18 ~

-~ ~ 3 ~

the reference, the receiver output is gated on and the cart-based central processing unit (CPU) is interrupted ("woken up") to begin message reception. The CPU
receives the trigger transmitter address 1808 and the CRC 1809. It then validates the data by calculating the check sum or CRC and comparing i-t to the received value 1809. If the data is not valid, the CPU igno~es the Trigger Transmitter message. If the data is valid, the CPU searches it memory for any message that has the received trigger address 1808 associated with it. If a match is found, the associated message is displayed to the consumer who is pushing the cart. As explained later, the message displayed may include a component tha-t is dependant upon the triggers previously received. If no match is found, no message is displayed.
Regardless of whether a match is found, all valid trigger transmissions received by the cart are logged in memory, along with the time and date of reception. This allows the path, speed, direction etc.
of the cart to be tracked by cart-based software. This allows messages to be selectively displayed based on the consumer's path through the store.
During check-out, the information logged in SCD memory is up loaded to the In-Store Computel and ul-timately up loaded over the WAN to the Billing and Control computer in the studio. This data can be allalyzed to determine how the store aisles are traversed by the consumers, dwell time in each category, overall shopping trip duration, etc.
Figure 11 shows the trigger transmitter in detail. The trigger transmitter is designed to c:onsume minimal power. This is to maximize the service life of the battery 1501. The only part of the transmitter - 19 - .
, 133~7 : ~
which has continuous power is the power-off timer 1502.
It-.s output signal is low for approximately 5 seconds ;~
and then it goes high. This high signal activates power switch 1503 (a power MOS FET) which allows battery power to be applied to the voltage regu].ator 1504 and the battery sense inp~lt of the battery state .-detector 1507. The voltage regulator 1504 supplies power to the remainder of the trigger transmitter circ~litry. On power-up, the reset clrcuit 1506 holds ; ,~', the microprocessor 1505 in the reset condition until the power is stable and the microprocessor clock 1509 is stable. The microprocessor 1505 then begins executing ' the software detailed in Eigure 19. The microprocessor '~
1505 is an 87C51 type manufactured by Intel ~ ' Corporation. It contains an on-chip program storage which is implemented as an Erasable Programmable Read Only Memory (EPROM). Tlle program is loaded into the ,-;,, ;~
EPROM at the time of manufacture of the trigger transmitter. '~' The battery state detector 1507 compares the switched battery voltage 1516 agains-t its internal ~ '' reference voltage. If the voltage is above the reerence '~
a logic 1 is returned to the microprocessor. If it is ,'~';
below the reference a logic O is returned to the ~, ,, '~
micl~oprocessor.
When the battery voltage is below the reference, ~ ' the battery is nearing the end of lts life. Store personnel must be alerted -to replace the battery before ;' it fails. The battery status and trigger transmitter address are communicated by the trigger transmitter 512 `~
to the electronics 514 on all shopping carts as they pass by. As the slloppillg carts go through the check-out lane, they are polled by the polling transceiver 516. This information is passed Oll to the ISC 502 by link 517. Once a day or on demand, t,he ISC
prints a list of trigger transmitters that have low - 20 - '~,`;''~`l,.', '"' ',;~'-'.".."."'~' ~ 3~3~7 ba-t-teries so that store personnel can service the batteries in the transmitters.
The 400 KHz oscillator 1510 provides a carrier to the Phase Shift Keyed (PSK) Modulator 1511.
The PSK modulator 1511 either passes the carrier s.ignal through with no change or it provides a 180 degree phase shift, under control of the da-ta input signal 1515 provided by the microprocessor 1505 to the modulator 1511. The logic inverter 1512 and the two power drivers 1513 (each a power MOS FET) provicle current gain and complementary drive to the loop antenna 1514. The antenna 1514 is resonant at 900 KHz.
The Dual In-line Package (DIP) switch 1508 provides 7 Single Pole Single Throw (SPST) switches. , The switches are set by personnel in a binary fashion to indicate the address of the Trigger Transmitter.
The trigger address is sent as a part of the trigger transmissions to the shopping cart. ~ach Trigger Transmitter has a unique address which indicates a unique location within the store.
Figure 12 shows the trigger transmitter power -cycle. At point 1601 the power~off timer 1502 is rulllling and power to the rest of the transmitter is off. At pOillt 1602 the timer completes its timirlc~ ;
cycle and powers-up the rest of the transmitter circuitry. ~t pOillt 1603, after the power-up reset cycle is complete, the microprocessor 1505 begins execution of its software. To provide forward error correction and establish rel.iable communications, the software transmits the trigger block 1803 redunclantly 4 times. This is to overcome any possible noise present in the store that may interfere with the trigger transmissions. The shopping cart only needs to receive one of the trigger blocks 1803 error free to act (i.e.
display a message to the consumer if there is a message with the matching trigger address present in the :',,'.~''`~`

1 3 ~ 7 shopping cart memory). At point 160~ tlle software has completed its transmission task and now it toggles a bit 1517 high and then back to low 011 one of i ts output ports. This l:riggers the power-off timer circuit 1502 which removes power to all of the res-t of the transmitter circuitry for the next 5 seconds. The trigger input to the power-off timer is pulled down by a resistor so that while the microprocessor is powered-down spurious triggers do not occur. The power-up to power-down duty cycle is approximately 1 pe rc ent .
Area 1605 shows a failure in which the - -microprocessor 1505 is hung-up ancl never re-triggers the power-off timer 1502 after completing its transmissions. This could be due -to some transient event (i.e. electrostatic discharge). In this case, the power off timer circuitry 1502 drops power to the ~ :
rest of the transmitter circuitry after a short time, preferably twice the typical power up time 1603. This -~
resets the microprocessor 1505 and allows the normal power cycle to resume.
Figure 13 shows the format of each character transmitted by -the trigger transmitter, the response trallsmi tter, and the message refresll transmitter . Each character that is transmitted by the Trigger Transmitter 512, the Polling Transceiver 516, and the Message Refresh Transmitter 503 is sen-t i.n serial asynchroncus forma-t. A start bit 1701 is transmitted followed by ei~ht data bits 1702 and one stop bi-t 1703. The least s.ignificant bit 1705 is sent first. This format is ;
common in the computer industry. It is implemented in many Universal Asynchronous Receiver Transmi tter (UART) integrated circuits. AII example is the 8250 Asynchronous - `
Communication Element manufactured by National Semiconductor Corporation.

- 22 - ;

','~ '';-'. ~' ` ~330~S7 Figure 14 shows an example of the group of 4 trigger blocks 1803 that is -transmitted every 5 seconds by the Trigger Transmitter 512. When the transmitter circuitry is powered-up at the end of the power-off timer cycle 1601, the hardware begins transmitting carrier with no modulation 1802. This idle time allows the transmitter circuits and the receiver circuits on the shopping cart to stabilize. Next the trigger bloc}c 1803 is transmitted 4 times.
Each trigger block 1803 includes a preamble 1804 followed by a flag character 1805, a length character 1806, a block type character 1807, a combined transmitter address and battery status character 1808, ancl finally a Cyclic Redundancy Check (CRC) 1809 which is two characters long. The preamble 1804 is three character-times of no modulation. This allows the character watchdog timer that is running in the shopping.
car-t electronics to time out and clear the reception buffer in the cart if a partial trigger block 1803 was received. This clearing occurs before each trigger block during the preamble time 1804. If a shopping cart enters the range of a Trigger Transmitter 512 whlle the transmit-ter is in the middle of sendincl a trigger block 1803, the cart will only receive part of the trigger block. When the preamble 1804 of the next tricJger block occurs, the partially received tricJger block~ will be cleared from the receiver and all software values will be re-initialized in anticipation of receiving the data in the current trigger block. The flag character 1805 is a unique fixed value that indicates that the next character is the length. The length character 1806 indicates how many characters are remaining in this block after the length character starting with the block type character 1807 through the last CRC character. The trigger block shown has a - 23 ~

~ 113~03~7 length value of 4. The block type character 1807 indicates what kind of block this is. The Trigger Transmitter sends a block type value of ~ero to indicate that this is a trigger block. The next character 1808 is made up of two data fields. The most significant ~:
bit is the battery sta-tus as received from the battery state detector circuitry 1507. The low order 7 binary .
bits are the transmitter address as read from the 7 position DIP switch 1508. The two characters that make up the Cyclic Redundancy Check (CRC) 1809 are computed by the transmitter microprocessor 1505 from the values of the preceding characters in the block. The algorithm is CRC-16 which is commonly used in the computer industry. The CRC 1809 is used -to detect errors in the transmission of the blocks 1803. The receiver determines the validity of the data in the block by calculating the CRC from the received data block using tlle same algorithm as the transmitter. It then compares t.he calculated CRC to the received CRC 1809. If tlley match the data block 1~03 has a very high probability of being correct. If they do not match, the block is ignored by the receiver. ~ ~
A short duration of unmodulated carrier 1810 ~ :
is sent after the fourth trigger block. During t:his time the microprocessor Oll the shopping cart is calculating the CRC on the fourt}l block to verify t}le `~
data in the block. There is a possibility that spurious characters may be received by t:he cart when the transmitter power is shut off. This idle time delays the possible reception of these noise characters and the m.icroprocessor interrupts that they produce.
Figure 15 is a flow chart of the software that the trigger transmitter single chip miCropIocessor 1505 executes on power-up after the reset cycle is complete. It first performs its initialization routine 1901 to set the processor operation modes, interrupts, ~- ~3~3~7 reyisters, etc. The only variable part of the transmission block is the address and ba-ttery status byte 1808. At 1902 the microprocessor 1505 reads the 7 bits of transmitter address from the DIP switch 1508 and reads the battery status from the battery state detector 1507. This data is combined into one byte, the top bit being the battery status and the low order 7 bi-ts the transmitter address. Next at 1903 the CRC
is calculated for the complete trigger transmission block 1803. The software next delays at 1904 to allow the external transmitter and receiver circuits t:o stabilize.
The next area of the flow chart is a loop that is executed 4 times. Firs~ the loop counter is incremented 1905. Next at 1906 a three character-time delay is executed. This -transmi-ts a preamble 1804 that has no modulation on it. Then at 1907 the rest of the trigger block 1803 is trallsmitted. The res-t of the block consists of a flag character 1805, a length ch~racter 1806, a block type character 1807, a character 1808 that is the transmitter address (7 bits) combined witll the battery status as the most significant hit, and finally two characters of Cyclic Redundancy C'heck (CRC) 1809. The transmission is done in software by toggling a bit on an outpu-t port. This is a "software U~RT" except that the start, data, and stop bits are differentially encoded as they are sent by the ;~
microprocessor 1505. This encoding, along with the . ~:: .. .....
Phase Shift Keyed (PSK) modulat:or circuit, produces Radio Frequency ~RF) transmissi.ons that are Differentially Phase Shift Keyed (DPSK).
The loop counter is tested at 1908. ~hen the 4 loops are complete, the software delays again to transmit unmodulated carrier 1810 at 1909. Then a bit 1517 on an output port is toggled at 1910. This :

~ 1 3~67 triygers the power-down timer circuit 1502 which ~`
removes battery power from all of the transmittc:r circuitry except the power-down timer itself. ~s the battery power to the CPU is falling, the CPU attempts to put itself into power-down mode at 1912. This is to save additional battery power.
In Figure 16 the Trigger Transmitter antenna coil 2001, which is preferably mounted on a she].f edge at the floor, and the shopping-cart-moun-ted recei.ve antenlla 2002 are shown schematically. Each is a solenoid of wire with its main axis oriented vertically.
The primary coupling between the two coils is magnetic :
(H-field). Each coil is resonant at 400 KHz. ~
FIGURE 7 depicts an ideal Trigger Transmitter ~ "
aisle zone coverage. The figure is a top view of an -aisle with shelves 1001 on both sides. Two example trigger transmitters 1002 are mounted on the left side of the aisle. The resultant "ideal" zone coverage 1003 of the aisle is shown. The zones are perfectly rectangular, of uniform field density, and abut each -other perfectly with no overlap. "~
FIGURE 8 is similar to FIGURE 10, but depicts a practical Trigger Transmitter aisle zone coverage.
The zones are not rectangular, not of uniform field :~
density, and do not abut each other perfectly. Within the zone, the trigger transmissions are strong enough `~
to trigger the display of a message if there is a corresponding message stored in the cart.
As shown in Figure 17, the Response Transmitter 2107, 2112, 2111, 2110, 2109, 2108, 2102, 2101 in the shopping cart electronics is very similar to the Trigger Transmitter 512 that is located`on the shelf edge. In the presently preferred embodiment UART
2107 a Model No. SCC 2691 manufactured by Signetics Inc. Serial asynchronous data 2113 from the UART 2107 and 9600 baud data clock 2114 are app].ied to DPSK

, ~3~3~7 encocler 2110. The encoder 2110 provides a zero degree Ol` 180 degree phase shift from carrier input to OUtp~lt based on data 2113 and data clock 2114. The 400 KH~
oscillator 2111 provides unmodulated carrier to the modulator 2110. The CMOS logic inverter 2109 and the two power drivers 2108 (eacll a power MOS FET) provide current gain and complementary drive to the loop antellna 2101 when they are connected to the antenna by the antenna switch 2102. Control of the antenna switch 2102 is by the transmit enable input to 2102. When high, the antenna 2101 is attached to the power drivers 2108. The antenna 2101 is resonant at 400 KHz. The tran6missions radiated by the antenna 2101 are 400 KHz DPSK, asynchronous, half-duplex, at 9600 baud. The Response Transmitter allows the shopping cart electronics to respond to interrogations from the Polling Transceiver 516 during the time tlle cart is at the check out station 515.
The Trigger Receiver 2101, 2102, 2103, 2104, 2105, 2106, 2107 mounted Oll the shopping cart picks up trigger transmissions 513 from the Trigger Transmitters -~
512 mounted Oll the shelves. It also picks up transmissions from the PollincJ Transceiver 516 nlounted at the check-out lane 515 when the cart is in the check-out lane. When the transmit enable input to the antenna switch 2102 is low, RF energy pickecl up by the ;~
antenna is coupled to the amplifier and bandpass filter 2103. The output of the amplifier 2103 is simultaneously coupled to the DPSK decoder 2104 and carrier threshold detector 2105. The carrier threshold detector 2105 generates an AGC signal which is fed back to control the gain of ampli~ier 2103. This is well known i.n the art. When the received signal is of adequate level, the -threshold detector 2105 outputs a signal that is coupled to 2104 and the logic gate 2106. The DPSK
decoder 2104 contains a Phase Locked Loop (PLL). Only :

- ~33~367 whell the PLL is in lock and the signal from 2105 i8 present does the decoder 2104 enable the received data (RXD) 2115 to the UART 2107. Gate 2106 asserts the Data Carrier Detect (DCD) signal 2116 to the UART 2107 only when the carrier level as measured by 2105 is adequate and the PLL in 2104 is in a locked condition.
The UART 2107 contains an on-chip Baud Rate Generator to control data transmit 2113, 2114 and receive 2115 rates. Clock is controlled by the crystal 2112. The UART 2107 provides data, status and interrupts to the microprocessor bus 1310 and microprocessor 1311.
Power utilization of the Trigger Receiver and Response Transmitter is minimized by powering Up only necessary sections of the circuit (i.e. the recei.ver section 2117 or the transmitter section 2118) and by controlling the power down mode of UART 2107. This is to maximi~e battery life in the shopping cart e~ectronics. `~
Figure 18 shows the Polling Transceiver (PT) ;~
516, which is mounted at the checkout lane. It forwards queries from the In-Store Computer (ISC) 502 ~
to the electronics mounted on the shopping cart. The ~ ~:
cart sends responses which the Polling Transceiver 516 returns to the ISC 502. The Local Area Network (LAN) 517 connection between the ISC 502 and PT 516 is by an RS-422 multidrop asynchronous hardwired linl{ at a rate :
of 9600 baud. Eaeh PT 516 has a unique address on the LAN which corresponds with the check-out lane number.
The linlc between the PT 516 aIlcl the shopping cart based :~
electronics 514 is 400 KHz Differentially Phase Shift Keyed (DPSK) Radio FrequeIlcy (RF), asynchronous, half `~
duplex, at a rate of 9600 baud. All links use a byte COUIIt protocol.
The description of the Polling Transceiver `~
516 is very similar to the previously described Trigger Receiver and Response Transm.itter except for the following exceptions. Block 2207 is now a single ch.ip `

- 13~3~7 microprocessor (Intel Corporation 87C51) instead of a UART 2107. Block 2204 I10W provides signal DCDl. Block 2205 now provides signal DCD2. The microprocessor 2207 does a logical ~ND of these two signals to produce a Data Carrier Detect (DCD) signal in software. The microprocessor 2207 directly controls the state of the antenna switch 2202 by signal "Request To Send not"
(RTS not) 2218. The serial data 2219 sent from the microprocessor 2207 to the encoder 2210 is differentially encoded by the "software UART"
(previously described in -the Trigger Transmitter 512) therefore 2210 is now a PSK encoder and does not require a data clock as in the Response Transmitter.
The Polling Transceiver 516 has additional circuitry. The power supply 2212 converts 120 volt alternating current to direct current to supply all of the circuits. The data memory 2213 provides a buffer for messages received from the ISC 502 via the LAN 517 which are to be forwarded to the shopping cart electronics 514 and vice versa. The crystal 2214 ~y controls the clock signal to the microprocessor 2207 in a reset state during power-up until the power supply voltages and microprocessor clock are stable.
The ISC 502 originates a l,ocal Area Network (LAM) which iS connected to all of the PT 516 units in the store. The interface to the LAN is via driver 2216, receiver 2217 and the seriaI interface of the microprocessor 2207. The link is RS-422 multidrop.
The LAN address of each speciflc PT is put into the EPROM of the single chip microprocessox 2207 at time of manuEacture.
Figure 19 shows the format of a transmission block sent by the Polling Transceiver 516. The Polling Transceiver (PT) 516 can send four types of commands to the shopping cart electronics 514, They are poll, log dump, log clear, and power down. The value of the - 29 - ~
'; . ', ' ' "

'~''.','' : ''~
' . "~.,~'" ' `~ '.'.

3 ~ 7 block type character 2304 determines what the command is. The format of the commands is similar to t}ie trigger blocks transmitted by the Trigger Transmitter 512. The protocol is a byte coun-t type. Each character of the transmission block is sent asyncllronously one start bit 1701 eight data bits (least significant bit first) 1702 and one stop bit 1703. A command includes a preamble (30 bit-times of idle state) 2301 a flag character 2302 a length character 2303 a block type character 2304 a Polling Transceiver address 2305 two ~ ;
characters of Cyclic Redundancy Check (CR~) 2306 and a ~-postamble (30 bit-times of idle state) 2307. The flag 2302 is a fixed eight bit value. The length character 2303 indicates how many characters are in the block starting with the block type character 2304 through the last CRC character 2306.
The block type character 2304 has foul -values. A value of one indicates that this is a poll request (command) to the shopping cart. The cart will respond with a status response as described in Fi.gure 20. ~ value of two indicates that this is a log dump request (command) to the shopping cart. The cart will respond with a log dump response shown in Figure 21. A
value of three indicates that this is a log clear request (command) to the shopping cart. A value of four indicates a power down request (command) to the `~
shopp.ing cart. The cart will then power down. The cart will respond with a log clear response as shown in ~ :
Figure 22. The response blocks (Figures 24 25 and 26) use a byte count protocol t:hat is s.imilar to that ;~
of the Trigger Transmitter 512 except that the by-te count field 2403 2503 2603 are two characters ;~
(s.ix-teen bits) long.
FIGURE l9 shows the presently preferred embodiment of the display mounted on the shopping cart.
The back of the display electronics rests on the ~ ~ :

"
: ~

~ 33~36'7 original cart handle. A new handle 1201 is attached in front of the display. The display is a super-twist or hyper-twist liquid crystal display (LCD) for low power consumption and high contrast. Its resolution is 640 picture-elements (pixels) across by 200 pixels high.
The display is overlaid with a transparent touch-sensitive keyboard This provides for a very flexible keyboard configuration because the key legends can be changed under program control.
FIGURE 10 is a block diagram of the SCD ~;
cart-based electronics 514. The man-machine interface is provided by the display :13~)1, keyboard 1303 and -audio speaker 1308 sections. The liquid crystal display (LCD) 1301 i9 preerably a super-twist type for high contrast and wide viewing angle. The display is a multiplexed type that requires a refresh controller 1302. The lceyboard i s a clear overlay on tlle LCD . The keyboard scanner 1304 provides an interrupt pex character to the central processing unit (CPU) 1311.
This allows the CPU to go into low power mode whenever i-t is idle in order to conserve battery life. The keyboard interrupt will bring the CPU out of low power mode when required. The keyboard interface 1304 can produce CPU reset to the CPU 1311 for a keystrohe, when conditioned by software. The audio output s~lbsystem 1308 and 1309 provides output of various ~ -pitches and crude speech~
The Read Only Memory ( ROM ) subsystem 1305 provides storage and retrieval of f ixed program and data segments for the CPU 1311~ Data is loaded into the ROM at time of system manufacture. An example of -fixed data is the unique serial number which is loaded -into each cart during manufacture.
The static Random Access Memory (RAM) 1306 -with non-volatile power prov:ides dynamically changeable storage and retrieval of program and data segments for ~ ~-.. ~ . : ~ ..:
':..,''''` :,,`.'..

~` ~3~3~7 ~: ~
the CPU. Program and data segments can be down ].oaded via the refresh receiver 1316 and 1317 from the In-Store Computer. Thi.s allows rapid update o ~-software in the carts. The non-volatile clock and calendar provides date, time of day, and clock interrupts to the CPU. The clock circuitry 1307 can -produce CPU reset to the CPU 1311 when an "alarm" date and time is reached. `
The Central Processing Uni-t (CPU) 1311 provides overall system control and program execution.
It is a low power Complementary Metal Ox.ide Semi~
conductor (CMOS) microprocessor.
The Trigger Receiver subassembly 1312 COIISiStS of a loop antenna 1314, receiver circuitry ; ~.
1313, and a CPU bus interface 1312. The antenna 1314 is optimized for reception of low-frequency magnetic (H-field) transmissions 1315 from trigger transmitters 512 and polling transceiver 516. The trigger receiver has a fast acting Automatic Gain Control (AGC) ci rcuit with signal amplitude discrimination. Only siqnal amplitudes above a set reference enable the output of the receiver circuitry and cause an interr-lpt to the CPU 1311. The reference is based on the AC:C voltage and, therefore, varies as the AGC voltage varies.
The Trigger Receiver could alternately be implemented as a microwave, infra-red, or ultrasonic receiver in correspondence with the Trigger Trans-mi t ter . ~ `
A return transmi t path is also provided bytransceiver 1312, 1313, and ant:enna 314. This a].lows low duty cycle return transmission from the cart to the In-Store Computer and store scanning system at check o~lt.
The Message Refresh Receiver subassembly also contains a VHF receiver 1317 along with a recelver to '"';'''''`''~'.
. ~ ,","'~ ~'' .

- 33 - __ ~ 3 ~ 7 bus interface 1316. Only signal amplitudes above a set ~ `~
reference level enable the output of the receiver circuitry and cause an interrupt to the CPU 1311.
The power supply 1320 provides power, power control, battery recharge control, and power supply ~ ::
status to the cart-based electronics to minimize power dissipation and maximize battery life. The lithium primary battery 1321 provides non-volatile power to the Static RAM 1306 and the clock and calendar 1307. The lithium rechargeable battery 1322 is the main power so~rce for all of the SCD cart-based electronics 514.
The current status (discharged or charged) of these batteries can be reported to the CPU via the power supply interface 1319. This status is returned by the response transmitter to the ISC during check-out.
Store personnel can be a].erted to replace discharged battery packs.
The power supply can also turn power on and off tG various subsystems on the cart, under control of the CPU. Power can be independently controlled to the display 1301 and 1302, the audio subsystem 1308 and 1309, the trigger receiver and response transmitter 1312, 1313, and 1314, and the message refresh receiver 1316 and 1317.
The power supply also monitors and report~
the status of a cart motion (shake) sensor and handle touch sensor 1323 ancl provides an interrupt to the CPU ~ ;
upon detection of motion. The motlon sensor might be combined in the wheel generator 1326 if a yenerator is used on the cart sys-tem. If -the cart has not moved in a relatively long time, the CPU turns off power to all of the subsystems that it can and puts itself into power down mode. -The handle touch sensor is used to determine if a consumer was a-t the cart when a particular ad was displayed. This data on ad delivery is returned during `~

~33~3~7 check-out to the ISC and to tlle studio. This data is similar to the electronic diaries ("People Meters") usecl in the television ratings business. ~-DESCRIPTION OF SHOPPING-CART-BASED_SOFTWARE
The Shopping Cart Display (SCD) software COllSi sts of foreground and background tasks. The foreground tasks consists of initialization, idle loop, and display execution. Thére are two background (interrupt driven) tasks exec~lting. The first t:ask is Message Refresl1. It is detailed in Figures 26 through 35- The second task operating is the Trigger reception . .
task. Trig~er reception is detailed in Figures 36 throu~h 39- ~-EOREGROUND TASK (MAIN LOOP~ -In Figure 23, at 2701 the microprocessor 1311 has completed a hardware reset. Reset occurs for "~
several reasons. First, power up after an unexpected power down (i.e. complete battery failure). The other sources of a microprocessor hardware reset occur as a result of some peripheral device action. The software at 2703 tests the warm boot flag. If the flag is not set, then this reset occurred unexpectedly (as a part of power up upon installation of new batteries.) Consequently, the diagnostic programs are executecl at 2705 with the results displayed Oll the liquid crystal -~
display. Next, the.cold boot i.nitialiæation routine is `~
executed at 2707 to initialiæe system variables and 1 memory.
If the warm boot flag was set, it indic:ates ~ `~
that this reset was anticipated by the software. These types of resets can occur rom the motion sensor, :
handle sensor, clock or keyboard after their int~rface circuitry has been conditioned by software to output - 34 ~

~ 3 ~
the hardware reset signal instead of interrupt signal.
If after CPU reset, a keyboard request is pending, then at 2709 and 2711 the character is taken from the interface circuit and loaded into the keyboard buffer.
Next the warm boot flag is cleared at 2713 and t.he warm boot initialization routine is executed at 2715. Next, at 2717, the external interfaces which could cause CPU
resets, are initialized so as to generate interrupts not CPU reset. Next tlle software powers up the Trigger and Message Refresh receivers at 2719 and loads and starts the activity watchdog timer at 2721. This watchdog timer is reinitialized and loaded by any activity (keystrokes, cart motion, handle touch). When the watchdog timer times out, for example after 15 minutes of inactivity, the cart will power down to conserve battery life.
Next at 2733 is the start of the idle loop.
At 2735 the microprocessor 1311 is put into a low-power halt mode. In this mode, the CPU clock is still running, but CPU execution is halted at the ins-truction that put the CPU into the low-power halt mode, and interrupts are still active. In this mode CPU power `
cons~mlption is significan-tly reduced. After an i.nterrupt occurs and the return from the interrupt service ~ ~:
routine is executed, the CPU begins execution at the ~ ;
instruction following the iIlstruction that caused the CPU to enter the low-power halt mode. The Hitachi 6~180 and the Intel 80C31 examples of CMOS micro-processors with this low-power halt mode.
At 2735 the CPU Waits in this low-power mode for the next interrup-t to occur. ~t the termination of the interrupt service routine, the next instruction after 2735 is executed. First the display state machine activity is tested at 2737 (i.e. is a message be.ing actively displayed now). If the state machine is active, control is given to the DISPLAY software 35 - ;

~ 3~Q3~
rout:lne at 2739. When -the DISPLAY routine is done executing, it returlls to IDL (to enter low-power mode again). If the display state machine is not active, then at 2741 and 2743 any pending display requests from the Trigger Receiver are executed. This routine is called TSTART. At the termination of TSTART low-power mode is re-entered via IDL. Next at 2745 a test is made for any pending display request from an immedi~te message delivered to the shoppiny cart via the Message Refresh radio link. If any requests are pending, the MSTART routine is executed. Upon completion of MSTART, low power mode is re-entered via IDL. At 2749 and 2751 any pending keyboard requests are handled (information requests, game requests, calculator mode). These requests are handled by tlle KSTART subroutine. At the termination of the KSTART subroutille, the low-power mode is re-entered via IDL. If none of the 4 previous requests are pending, low-power mode is re-entered via IDL to conserve battery power while waiting for the next interrupt.
Referring now to Figures 24A-D, at 2801, the DISPLAY subroutine is shown. Its purpose is to execute the display state machine. Each message to be displayed has a control structure and data areas that `~
contain image and audio. The contlol areas defines a `
"scrlpt" which governs how the image and audio are displayed on the screen. The script structure is slmilar to that available in a commercial program called SHOW PARTNER by Brightbill-Roberts and Company, Ltd. Tllis is a slide show program witll a script associated with it to control transitions between slides. The script structure is quite flexible, in tha-t it can branch between image seyments based on keyboaxd input, time, or other external program inputs (i.e. current trigger address or loy of previous trigger receptions). It is a c:omplete application :

-~ ~ 33~7 language for controlling display of images and a~ldio.
The state machine at 2803 executes this script control structure. At 2805, the DISPL~Y subroutine returns to the point where it was called.
The TSTART subroutine at 2807 is executed as a result of a Trigger block being received. The subroutine first gets the message address or number that it is to display at 2809. It then loads ancl initializes the state machine with the information from the control structure of the requested message at 2811.
It next calls the DISPLAY subroutine at 2813 to begin the execution of the script. Finally, at 2815, I'START
returns to the point where it was called.
The MSTART subroutine is executed at 2817 as a result of reception of an Immediate Type 1 or Immediate Type 2 message over the Message Refresh radio -link. The header associated with the message is ~ -~
retrieved by the MSTART subroutine at 2819 to determine -`
the message whether it was an immediate 1 or immediate 2 type. Next at 2821 the state machine is loaded with the control information tscript) from the requested ~ ~ `
message. The DISPLAY subroutine is then execute~i at 2803 to begin execution of the script. Finally, at "~
2825, MSTART returns to the pOillt where it was called. ~- ;
The KSTART subroutine 2827 is executed upon re~uest from the consumer via the keyboard for information, games or calculator mode. Mucll like the previous TSTART and MSTART subroutines, the KSTART
s~lbl~outine initializes the stat:e machine with the control information from the keyboard message at 2829. -Next, at 2831, it begins execution of the state machine by calling the DISPLAY subroutine. Then, at 2833, KSTART returns to the point where it was called. `~
Figures 25 A and B show the interrupt routines associated with the main idle loop. A motion sensor interrupt at 2901 or handle sensor interrupt at - 3~ -- ~ 33~7 2902 loads and restarts the activity watchdog timer at 2909. Each keyboard interrup-t at 2905 also loads and restarts the activity watchdog timer at 2909, but first -:
the keystroke data is saved in the keyboard buffer at 2907. If a long period elapses with no motion or handle touch or keystroke, the activity watchdoy timer will count down to zero and generate an interrupt. At this point 2913, the software executes a power-down command by branching to the INACT routine at 2915.
This is to conserve battery power. A
return-from-interrupt is executed a-t 2911.

MESSAGE REFRESH TASK
One of the background (interrupt driven) tasks that executes in the Shopping Cart Display (SCD) electronics is the Message Refresh task. The data frames 3001 that it receives are shown in Figur~ 26.
Each frame Co2lSiStS of a header block 3003 follcwed by -~
a variable number of subsequent data blocks 3005. The main purpose of the Message Refresh task is to receive, validate and conditionally load the header and data bloc]cs from the Message Refresh Transmitter into `~
: .:
memory. The data on this link is a byte-count protocol, consisting of a preamble, a flag character, a length field (2 characters), a block type character, a variable length data field, followed by a 2 character Cyclic Redundancy Check (CRC) field.
Figure 27 shows the t:ype of data blocks that can be received over the Message Refresh radio l.ink.
In Figure 28, iE the block type is hexadecimal 00, this block is a message header. Thi.s indicates the subsequent blocks are to have a block type of hexadecimal 08. These are message data blocks. With information present in the message header, the software is ahle to decide if it already has this message and version stored in loca]. memory. If .it already has this message - 3~ -~- 133~67 and version number, it ignores the subse~uent blocks and waits for the next header or command. In a similar manner, Figure 28 shows the format of an immediate one, and immediate two message header and a code segment header along with what type of subsequen-t data ~Iocks are to be expected after each one.
Figure 29 shows the format of a subsequent message block. It contains a preamble 3301, flag byte 3303, length field 3305 (2 characters), block type -~
character 3307, message number and version number field` `~
3309 (2 characters), Subsequent Message Blocks field -~
3311 (2 characters), followed by a variable length data field 3313 and a two character CRC field 3315. Bloclc type values 3307 of hexadecimal 08, 09 or OA indicates that the data field 3313 is part of a message. The data field 3313 is compressed video and audio along ``~-`
with trigger information and a display control structure (state machine variables or script). If the block type value 3307 is hexadecimal OB, the data field 3313 is part of a program that is to be loaded into ;~
memQry.
In addition -to headers and data blocks, the Message Refresh radio ].ink can deliver commands to the SCD electronics. The format of a clock set command is shown in Figure 30. In conformance with the byte-count protocol, the command contains a preamble 3~01, a flag character 3403, a length field 3~05 (2 characters), bloclc type character 3407, fol]owed by a data field ~;
3~09 tha-t contains cloclc set parameters a~d a CRC 3411 (2 characters). In the clock set command the block type value 3407 is hexadecimal 10. When the SCD
electronies receives this command, it initializes its ;~
time of day clock to the time and date values in the data field.

~ :
- 39 - ~ ~
": :.

~1 3 ~ 7 -A second command that can be received over the Message Refresh radio link is the power down command. It has a similar format to that of the previous clock set command. The format of a power down command is shown in Figure 31. Its block type 3507 is hexadecimal 11. The optional data field 3509 contains a power-up date and time. If the field 3509 is present .
and contains data within a legal range, the SCD time of day clock alarm is initialized with the values from the data field 3509. The shopping cart then goes into a power down mode to conserve battery power and ~ -optionally powers up at the alarm time.
The Message Refresh reception software is :
detailed in Figures 32 through 35. At 3601 upon reception of a message receiver interrupt, this routine `
is entered. The routine first checks to see that there are no errors detected by the receiver circuitry at 3603. If errors are present, the error exit ME is executed at 3605. If no errors are present, the MR
character reception watchdog timer is reloaded with its in.itial count value and enabled to begin countdown at 3607. This timer is continuously reloaded on reception of each character from the Message Refresh radio link.
If a gap in characters longer -than the time value of the Message Refresh character reception watchdog timer occurs (approximately 2.5 character times at the link ra-te of 9600 baud), the timer generates an interrupt at 3630 and exec~ltes the ME error exit at 3632. This guarantees that if a partial b].ock is received, the preamble (3 character times) of -the next block causes a Message Refresh character watchdog timer interrupt which clears out the partially-received block and reinltializes the software to correctly receive the next block.
After the timer is loaded with its init.ial ~ ;
value, the received character i.s read from the receiver -- 133~3~7 circuitry 3609. Depencling on the state variable MCRS
(Message-Refresh Character Reception State) a series of routines are executed. These routines comprise a state machine for reception of data blocks in the format depicted in Figures 26, 27, 28, 29, 30, and 31. If the state is 0 (MCRS = 0) at 3611, the message refresh ~ ;~
idle, awaiting flag byte (MIDL) routine is executed at 3613. The routine MIDL first checks to see if the received byte equals the flag value at 3637. If not, `-~
it discards the character and does a Return From ~`-Interrupt (RET I) at 3641. If the received byte is ec~ual to the flag value, then the Message-Refresh Character Recep-tion State (MCRS) is advanced to Active Awaiting Length Byte High at 3639 and a Return E'rom Interrupt (RET I) is executed at 3641.
On receipt of the next Message Refresh character interrupt, the Message-Refresh Active Awaiting Length Byte High (MAALH) routine is chosen at 3615 and is executed at 3617. This routine loads the received byte into the Message-Refresh Byte Count (MBC) high byte at 3645. Next, at 3648, it advances the -~
Message-Refresh Character Reception State (MCRS) to Active Awaiting Length Byte Low. It then executes a Return From Interrup-t (RET I) at 3650.
On receipt of the next Message Refresh character interrupt, the Message-Refresh Active, Awai-ting Length Byte Low (MAALL) routine is cho~en at 3619 and is executed at 3621. This routine loac1s the received byte into the Message-Refresh Byte Count (MBC) low byte at 3fi57. It then advances the Message-Refresh Character Reception State (MCRS) to Active Rec~iving Block at 3659 and executes a Return from Interrupt (RET I) at 3661. ` :
Subsequent Message Refresh character interrupts cause the Message-Refresh Active Receiving Block (MARB) ;
to be chosen at 3623 and executed at 3625. Upon entry, - 42 - : .
~L3~3~
this routine loads the received byte into the next location in the MR Block Reception Buffer at 3701.
Next, at 3703, the MR Byte Count (MBC, a 16 bit value) -~
is decremented. If the MBC is not 0 at 3705, more :~
~haracters are to be received in this block, and therefore, a Return from Interrupt (RET I) is executed -~
at 3707. If the MBC is equal to 0 at 3705, all of the ~s~ ~.
characters for this block have been received. The routine next calculates the CRC on the received block at 3709 and compares this to the CRC that was received in the block at 3711. If they do not match a-t 3713, the ME Error Exit is executed at 3632. I the two CRC's match at 3713, then it is highly probable that the block has been received correctly. The routine next disables the Message Refresh character reception ~ :
watchdog timer at 3715 and dispatches on the block type field as received in the data block at 3717, 3719, 3721, 3723, 3725, 3727, 3729, 3731 and 3632.
If the block type is hexadecimal 0, 1, 2 or .
3, the Message Header (MH) routine is executed at 3719. ~ :
If the block type is hexadecimal, 8, 9, A or B, then the Message Block (MB) routine is executed at 3723. If .
the b70ck type equals hexadecimal 10, then the Set `~
Clock Command (SCC) routine is executed at 3727. If :.
the block type e~uals hexadecimal 11, then the Power Down command (PDC) routine is executed at 3731. If the block type value does not fall into any of the ~revious four categories, then the ME Error Exit routine i.s executed at 3632.
The Message ~eader (MH) rou-tine 3719 compares -:
the message number and version number from the received .
header block to those message numbers and version ~:
numbers currently in message memory at 3801. If a matching message and version are found at 3803, the software does not need to interpret the subsequent data blocks which will be transmitted on the Message Refresh .

.
3 ~ 7 :~:
radio link. The routine will calculate when it expects the next header block to be received based on the baud ;~
rate of the Message Refresh radio link and the value of the Subsequent Message Block (SMB) field rom the recently received header block, and will then subtract ~:
a small value from this and load this value into the Message Refresh (MR) Off Timer, and enable the count down to begin at 3805. It will then disable MR :~
receiver interrupts at 3807 and power down the MR
receiver circuits at 3809 to conserve ba-ttery power. ~ `
It then executes a Return from Interrupt (RET I) at 3811.
At the end of the Message Refresh (MR) Off Timer period, an interrupt is generated. The interrupt routine 3825 powers up the MR receiver circuits at 3827 and executes an Error Exit ME routine at 3632 to `
reinitialize all variables. This will allow the state machine to begin reception of the next data block in anticipation of receiving the next header block.
I~ the message number and version number from the received header block is not found in message memory at 3803, the Message Refresh State (MRS) is set to active (MRS=1) at 3813. Next, the Subsequent Message Block (SMB) field, is read into the SMB
variable in memory at 381S. The Message Refre.sh block ~ `~
reception watchdog timer is loaded with its initial val~le and enabled to begin countdown at 3817. I~ a `~
subsequent message block is not received within the watchdog timer period, an interrupt is generated. The interrupt routine 3823 executes an Error Exit ME
routine at 3632 to reinitialize the state machine variables. At 3819 the received header data is saved in memory in a header save area. Next, at 3821, the MX
message exit routine is executed.
Once a message header has been received, the next blocks will be message blocks. This will cause - ~3 -- 4~ --- ~33~3S7 execution of the message block (MB) routine 3723. Tlle routine checks the Message Refresh State (MRS) to see that it is active at 3830. If a message block is received without a previous header being recei~ed, this is an error, and the ME error exit routine is executed at 3632. If a message block is received after a ;~
header, the message number and version number of this block is compared with the saved header message and version values at 3832. If the values do not match at 3834, this block is to be discarded and the ME Error~ ~
Exit routine is executed at 3632. If they do match, `
the variable SMB (Subse~uent Message Block) is decremented at 3836. This is compared with the received SMB field from the curren-t message block at 3838. If they do not match, this block is out of sequence and the ME Error Exit is executed at 3632. If the received SMB matches the in memory SMB, then this data block is correct. The routine next sets the Update In Progress flag on this parti.cular messR~e in memory at 3840. Using the con-trol information from this received message block, the data area of the ~ ~
received block is moved to the message memory area at ~ ;
3842.
If the in-memory SMB variable is not equal to zero at 3844, then more message blocks are expected for the update on this message and the MX exit routine is executed at 3821 in anticipation o~ receiving the next bloclcs. If the SMB variable is equal to zero at 384g, thell this is the last message bloclc for this message. ~ :
Tlle routine clears the Update ~n Pro~ress flag on this message in memory at 3846. It next examines the the ~;
saved header area ~n memory at 3848. If the saved header type is not an immediate 1 or immediate 2 type, then this message refresh is complete and the ME exit rou-tine is executed at 3632 to clean up variables~ If the saved header type i.s an lmmediate 1 or immediate 2, `
- 4~ -.' ".,~

- ~5 -133~7 -then the saved header area is copied into the queue for ; -~
the foreground display task to retrieve at 3850. Next, at 3632, the ME exit routine is executed to cleanup variables.
At 3727, the Set Clock Command (SCC) is shown. This routine retrieves the data field from the received block and loads this into the SCD time-of-day clock. It then executes an MX exit routine 3821 to clean up variables. ~:
Tha Power Down Command (PDC) routine 3731 first disables all interrupts at 3903 and checks the data field of the received command to see if the time and date are within valid ranges at 3905. If they are, ~`
the routine conditions the clock interface circuitry to produce a CPU reset signal upon detection of an alarm condition at 3907. Next, at 3909, the alarm section of the time-of-day clock is loaded with the data from the received block. If the data field of the power down command does not contain valid time values, the routine does not set or condition the alarm section of the time-of-day clock. Next, the warm boot flag is set at 3911. This flag indicates to the reset sof-tware 2701 that this CPU reset is expected. The INACT rout;ine 2915, after disabling all interrupts at 3910, enters the routine just before the setting of the warm boot flag at 3911. Next, at 3913, the motion sensor interface, handle sensor interface and keyboard interface are conditioned to produce tlle CPU reæet signal not the interrupt signal. The routine next powers down the receivers, the response transmitter and display at 3915 to conserve battery power. Next, at 3917, the program counter return stack is cleanecl up by popping-off and discarding the interrupt return address. Finally, this routine sets the microprocessor into its power-down halt mode at 3919. In this mode, the only way that the microprocessor will restart is - 45 ~

'' ''~.~'',: ' ' , ~
~ 3 3 ~
via a hardware reset signal. Since the CPU clock is not running at this time, interrupts are ignored. The -microprocessor will stay in this mode until a reset signal is generated by one or more of four events occurring: 1) motion sensed by the motion sensor -~
interface, 2) a handle touch sensed by the handle sensor, 3) a key-press on the keyboard, 4) an alarm condition produced by the time-of-day clock.
The ME exit routine 3632 sets MRS=0 at 3921, SMB=0 at 3923, disables the MR block reception watchdog timer at 3925, and clears the header save area in memory at 3927. The MX message exit routine 3821 clears the Message Refresh (MR) block reception buffer at 3929. It sets the MR Character Reception State to idle at 3931. It disables the MR character reception watchdog timer at 3933. It then reinitializes the MR ~;~
receiver circuitry at 3935 and enables the MR receiver interrupts at 3937. Finally, at 3939, a Returll from Interrupt (RET I) is executed.

TRIGGER RECEPTION TASK
Another background (interrupt driven) taslc that is executed in the Shopping Cart Display (5CD) electronics is the Trigger Reception task. The main `
purpose of this software is to receive, validate and act upon receptions from the Trigger Transmitters 512, and Polling Transceivers 516. These transmissions are in a byte-count protocol and are detailed in figures 18 and 23. Optionally, depending on tha transmission received, the SCD electronics caIl return a response to the Polling Transceiver 516 in a format detailed in figures 2~, 21 and 22. , The Trigger reception software is detailed in Figures 36 through 3~9. At 4001 upon reception of a TricJcJer receiver interrupt, this routine is entered.
The routine first checks to see that there are no ~-- 46 - ~

.
~3~3~7 errors detected by the Trigger receiver circuitry at 4003 If errors are present, the TE error exit routine is executed at 4005 If no errors are present, the Trigger character reception watchdog timer ls reloaded with its initial count value and enabled to begin countdown at 4007 This timer is continuously reloaded on reception of each character from the Trigger Receiver If a gap in characters longer than the time value of the Trigger character reception watchdog timer occurs (approximately 2 5 character times at the link rate of 9600 baud), the timer generates an interrupt 4130 and executes the TE error exit routine 4005 This guarantees that if a partial Trigger block is received, ~;
the preamble (3 character times) of the next block will cause a Trigger character watchdoy timer interrupt which clears out the partially-received block and reinitializes the software to correctly receive the nex-t Trigger block After the timer is loaded with its initial value, the received character is read from the Trigger receiver circuitry at 4009 Depending on the state variable TCRS (Trigger Character Reception State) a series of routines are executed These routines comprise a state machine for reception of data blocks in the format depicted in Figures 1~ and 19 If the state is 0 (TCRS = 0) at 4011, the Trigger Idle, awaiting flag by-te (TIDL) routine is executed at ~013 Tlle routine TIDL first chec}cs to see if the received byte equals t:he flag value at 4037 If not, it discards the character and does a Return from Interrupt (RET I) at 4041 If the received byte is equal to the flag value, then the Trigger Character Receptlon State (TCRS) is advanced to Trigger Active Awaiting Length at ~ c 4039 and a Return From Interrupt (RET I) is executed at 40~

-` ~33~367 On receipt of the next Trigger character interrupt at 4015, the Trigger Active Awaiting Length (T~AL) routine is executed at 4017. The routine T~AL
first checks the value of the received byte at 4029.
I f the received byte value i s 3 or less, it i s not a valid length byte and the TE error exit routine is executed at 4005. If the received byte value is 4 or more, the value is loaded into the Trigger Byte Count (TBC) at 4031. It next advances the Trigger Character ~eception State (TCRS) to Trigger Active Receiving Block at 4033. It then exacutes a Return from Interrupt (RET I ) at 4035.
Subsequent Trigger character interrupts at 4019 cause the execution of the Trigger Active Receiving Block (TARB) routine at 4021. Upon entry, this routine loads the received byte into the next location in the Trigger Block Reception Buffer at 4043.
Next, at 4045, the Trigger Byte Count (TBC~ is decremented . I f the TBC i s not 0 at 4047, more characters are to be received in this Trigger block, and therefore, a Returll from Interrupt (RET I ) is exec~lted at 4049. If the TBC is equal to 0 at 9:047, all of the characters for this Trigger block have been received. The routine next calculates the CRC on the rece.ived block at 4051 and compares this to the CRC
that was received in the bloclc at 4053. If tlley do not matcll at 4055, the TR error exit routine is executed a-t 4005. I f the two CRC ' s match a t 4055, then i t i s h.i~llly probable that the Trigger block has been received correctly. The routine next disables the Trigger character reception watchdog timer at 4057 and dispatches on the block type field as received in the Trigger block . Based on the block type charac ter, one of six routines is executed.
If the received block type field equals 0 at 4059, the received bloch is a Trigger block. The -- 4 ~

: .

.

.:

3~36~
Trigger block routine begins at 4061. The SCD
electronics keeps track of all trigger blocks received by keeping a log in memory. This allows the SCD to track its route within the retail store. It also allows interpolation between different -trigger addresses to allow display of message that have a direction sense (i.e., left or right). A display state machine uses the trigger log to modify the display of images. At 4101 the last trigger log entry is examined. If the logged address equals the current trigger address at 4103, then the exit time field of the last log entry is overwritten with the current time from the time-of-day clock at 4105. If the log record indicates that we have displayed a message based on this trigger address at 4107, then the message is not displayed again and the TE exit routine is executed at ~ ~ :
4005. If the last log entry does not match the current trigger address at 4103, then a new entry is created in the trigger log at 4109. ~n example of the trigger log format is shown in figure 39 If the display state machine is currently executing (the state machine is not idle, which indicates that we are in the process of ::
displaying a message) at 4111, then the TE exit is .::
executed at 4005. If the display state machine is idle at 4111, then message memory is searched for a message ~:
that matches the current trigger address at 4113. If no match is found, the TE exit is executed a-t 4005. If a ~atching message is foulld, an additional test is made at 4117. If the message update flag for this particular message is set, then it is not to be displayed and the TE exit is executed at 4005. If the message is not in the process of being updated, then the message address i5 saved for the foreground display task at 4119. Next, a display request flag is set for the foreground display task at 4121. Next, the displayed bit is set in the last trigger log entry at : ~
~ 49 - :
;~

. . .

~3~67 4123. Nex-t, the status of the halldle and motion sensors is logged in the c~lrrent trigger log entry at 4125. Finally, the TE exit is executed at 4005.
The trigger exit, TE routine, is shown at 4005. This is a normal and error exit routine that cleans up the trigger block reception buffer at 4132, the trigger character reception state at 4134, the trigger reception watchdog timer at 4136, and the trigger receiver circuits at 4138. This is in anticipa-tion of receiving the next valid trigger block. The routine finally does a ReturII from In-terrupt ~RET I) at ~-4140.
If the received block type equals 2, it is a poll request (PL) from the check-out transceiver. The PL routine is entered at 4065 and at 4201 builds a status response block in memory as shown in figure 20.
It then, at 4203, calls the transmit response (TRESP) subroutine and finally does a TE error exit at 4005.
If the received block type equals 2, then a dump log (DL) request has been rèceived. The DI.
routine is entered at 4069 and at 4205, builds a response block in tnemory from the data logs that have been accumulated. The format of the response .is as shown in figure 21. The DL routine next, at 4207, calls the transmit response (TRESP) subroutine and does a TE exit at 4005.
If the received block type equals 3, then a clear log (CL) request has been received. The CL, routine is entered at 4073 and at 4209, clears memory resident logs. The routine, at: 4211, builds a respc~nse block in memory whose format is according to Figure 22, and at 4213 calls the transmit response (TRESP~ routine and does a TE exit at 4005. -~
If the received trigger block type equals 4, :'.~:.,.'!~.~,'.' then a Power Down Request (PDR) has been received. The - 50 - .

133~7 PDR routine 4077 branches to the power down routine (INACT) at 2915.
The transmit response subroutine controls the response trans~it circuitry. It is called by commands that are requested to return status and data to the check-out transceiver. Upon entry at 42~0, the routine disables the trigger receiver interrupts at 4222. It then waits until the received carrier drops at 4224, -~
which indicates that end of the postamble of the received block. It then powers up -the response transmitter circuitry at 4226 and delays until the transmit circuitry is stable at 4228. It then transmits the response block that was built up by the calling routine at 4230. It next powers down the rasponse transmitter circuitry at 4232 and delays ùntil the transmitter circuitry is fully down at 4234. Next, at 4236, it initializes the trigger receiver circuitry and at 4238, enables trigger receiver interrupts.
Finally, the transmit response subroutine returns at 4240 to the routine that called it. ..
A new log entry is created each time the SCD
encounters a trigger transmitter whose address is ; -`
different than the previously logged trigger address.
Figure 39 is an example of the format of the trigger log entry. The log contains the address 4301 of the trigger transmitter wllose transmissions crea-ted this ;~
log. The entry time field 4303 contains the time of : :-~
day during which this log record was first created.
The exit time 1eld 4305 is ~lpclated continuously with the -time of day while we are iII the raIIge of this trigger transmitter. If a message was displayed, the corresponding message number 4307 and version number 4309 is entered into the log. Additional bit 1ags are present in the log entry. They are: Message Displayed - this flag indicates that a tnessage was displayed;
Statu~ o~ Motion Detector - thi.s flag indicates whether :

---` 133Q367 the cart was in motion during the message display;
Status of Handle Sensor ~ this flag indicates if the cart handle was being held during -the time of message display; Trigger Transmitter Battery Status - this flag is the status of the trigger transmitter battery as received in the trigger transmission block. This status is ultimately reported back to the in-store computer (ISC) 502 via the Polling Transceiver 516 and local area Network (LAN) 517 so that store personnel can replace the batteries in trigger transmitters before they fall. ~ -While the invention has been described with reference to a particular embodiment, those of skill in -~
the art wiil recognize modifications which nevertheless fall within the scope of the invention.

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Claims (4)

1. A system for determining the position of a shopping cart within a retail establishment comprising:
means at a first location in said retail establishment for transmitting a position signal;
means associated with said shopping cart for receiving said position signal;
means for generating positional data from said position signal, wherein said positional data is representative of the position of said shopping cart within said retail establishment; and means for storing said positional data.

2. The system of claim 1 further comprising means for analyzing said stored positional data.

3. The system of claim 2 further comprising means for analyzing said stored positional data to determine the path taken by said shopping cart within said retail establishment.

4. A system for determining the position of a shopping cart within a retail establishment comprising:
means at a first location in said retail establishment for transmitting a position signal;
means associated with said shopping cart for receiving said position signal;
means for generating positional data from said position signal, wherein said positional data is representative of the position of said shopping cart within said retail establishment; and means associated with said shopping cart for communicating directional information, in a form discernable by a human, based on said positional data.