SimpleLink Wi-Fi® Enabled Electronic Smart Lock

1 1 SWAA169 December2017 SubmitDocumentationFeedbackCopyright 2017,TexasInstrumentsIncorporatedSimpleL ink Wi-Fi EnabledElectronicSmartLockApplicationRep ortSWAA169 December2017 SimpleLink Wi-Fi EnabledElectronicSmartLockBenjaminMoore, SimpleLinkWi-FiApplicationsTeamABSTRACTT hisapplicationreportdescribesthe developmentof Wi-Fi enabledelectronicsmartlocks(e- locks ).Spe cifically,the benefitsof addingWi-Fito an e-lockdesignare casesare presentedalongwith an estimateof systembatterylife for two SimpleLink Wi-Fimakesit possibleto createa batterypowerede-lockdesignthat can be securelymonitoredand controlledfromthe SmartLockReferenceDesignEnabling5+ YearsBatteryLife on 4 AA Batteries[1] is referencedthroughoutthis documentas theSmartLockReferenceDesign. For a list of supportingdocumentationand additionalresources,see (E- locks ).. Casesand Lockis or PowerUse of CC3220 SFromHibernateto TLS Connectionto CC3220 SFromHibernateto TLS Connectionto CurrentWithLSI = 500 SimpleLink of December2017 SubmitDocumentationFeedbackCopyright 2017,TexasInstrumentsIncorporatedSimpleL ink Wi-Fi EnabledElectronicSmartLockTrademarksSimp leLink,MSP430,CapTIvate,Internet-on-achi p,TexasInstruments,LaunchPad,BoosterPack ,MSP432are trademarksof a registeredtrademarkof a trademarkof a registeredtrademarkof othertrademarksare the propertyof December2017 SubmitDocumentationFeedbackCopyright 2017,TexasInstrumentsIncorporatedSimpleL ink Wi-Fi EnabledElectronicSmartLock1 IntroductionThoughtraditionallockshavebe enaroundfor thousandsof years,doorlockshavecontinuouslyevolvedin to morecomplexsystemswith integratedelectroniccontrolsand accesshomesand buildings,whileactingas the first line of defensein locksare commonlycalledelectronicsmartlocks(e-loc ks).

2 E-locksare changingthe way wethinkaboutand interactwith ,fobs,pin numbers,or evenmobiledevicescan act askeysthat lock or unlocka manyresidentialapplications,e-lockscan eliminatethe needfor usersto ,changingthe formof the key usedto opena doorhelpsaddressoneof the mainproblemsfacedby traditionallocks providinga methodfor quicklycreatingand an e-locksystemmakesit easyto createand manageaccesskeysat enablesnew features,suchas the abilityto remotelymonitorand ,integratingWi-Fidirectlyinto the e-lockeliminatesthe needto use a bridgeforconnectingthe lock to the integrateddesignprovidesan all-in-oneproductthat reducesoverallBOMcost and enablesapplicationsthat demandhigh throughputdirectlyto the casesfor and benefitsof integratingWi-Fiin an electronicsmartlockdesign,as well as someof the key requirementsfor e-lockswith ,this guidedescribeshow SimpleLinkWi-Fienablesthe developmentof batterypowerede-locksthat can be securelymonitoredand controlledthroughthe followingterminologyis usedthroughoutthis Asymmetrickey pairsare usedin algorithmswhereone partyperformsacryptographicoperationwith a key that is not the sameas the key usedto applythe pairsare definedas publicand privatekeys,and usedmostlyfor digitalsigningandsymmetrickey Authenticityensuresthat assetsor entitiesare genuineand authorizedto performa taskor usedas verificationprocessusuallyinvolvescrypto graphicalgorithms,whichcheckthat the entitiesare who they claimto be.

3 Somepredefinedtrustmechanismis alwayspart ofan Certificatesare publickey of thesubject,and a CA signatureof the headerand publickey. Anyoneprovidedwith the CA publickey(or sub-CAin caseof certificatechain)can verifythe subject s Confidentialityensuresthat an assetis not madeavailableor mostcases,confidentialitytranslatesinto encryption,whilein othercases,obfuscationtechniquesare usedto Integrityis an attributedescribingan objectthat remainsintact,in its entirety,comparedto Keysare usedfor dataencryption,key establishment,and key lengthsand typesdependon the algorithmused,theirpurpose,and the Measuresthat aim to providethe intendedprotectionof (E- locks ) December2017 SubmitDocumentationFeedbackCopyright 2017,TexasInstrumentsIncorporatedSimpleL ink Wi-Fi EnabledElectronicSmartLock3 ElectronicSmartLocks(E- locks )E-lockscan typicallybe classifiedin two categoriesbasedon wherethey will be used: Commerciallocks(hotel,office,shoppingcen ter,and so on) Residentiallocks(homeor apartment)Systemdesignconsiderationsare impactedbasedon whethera lock will be usedto securea residentialbuildingor a designedto be usedon the exteriorof a houseand are typicallylocatedon the residentialuse typicallyoperateon batterypowerand are expectedto last aleastone yearbeforethe batteriesmustbe distancebetweenthe doorand the in-homeroutercan vary,it is necessaryto choosea Wi-Fidevicewith robustconnectivityfor technologiesare typicallyusedto supportthe peer-to-peerconnectionbetweena key (fob or mobiledevice)

4 And a showsa diagramof the typicalwirelesslinksin a be placedon the exteriorof a buildingto preventinitialentryand on the interiorofthe buildingto controlaccessto areasrestrictedfor use by be line-powered,but manyoperateon ,commerciallocksface strictpowerconstraintsbecausethey are oftendeployedin largenumberof batterypoweredlocksacrossa buildingleadsto a largeamountof maintenanceeffortand cost whenbatteriesmustbe ,Wi-Fisolutionswith extremelylow-powermodesand fast wake-uptimesareessentialto Casesand Benefits5 SWAA169 December2017 SubmitDocumentationFeedbackCopyright 2017,TexasInstrumentsIncorporatedSimpleL ink Wi-Fi EnabledElectronicSmartLock4Wi-FiUse Casesand BenefitsIntegratingWi-Fiinto an electronicsmartlock designprovidesclearadvantagesoverotherlo w-powerRFtechnologiesthat do not providea directconnectionto the directWi-Ficonnectionto a homeaccesspoint(AP)makesit possibleto: Lockor unlockthe doorfromanywhereinternetconnectivityis available Knoweverytime the dooris lockedor unlocked Performfast Over-the-Air(OTA)

5 Updatesfromanywhere Easilyadd or removeauthorizedusersand authenticatethroughthe cloud Reducesystemcost and improveend-customereaseof use with a singledoor-locksolutionconnecteddirectly to the UnlockFromAnywhereConnectingan electronicdoorlock directlyto yourhomeaccessAP makesit possibleto accessthe lockfromanywherethroughthe lock connectsto the AP, the lock can createa connectionwith a usercan thencommunicateto the lock throughthe cloudserverwithanotherinternet-connected devicesuchas a smartphone,tablet,or cloudconnectivityby alwaysknowingwhetherthe lock is openor the lockis accidentallyleft open,a usercan quicklycheckthe statusof the lock and thensecureit fromthe mobiledevicewithouthavingto ,a homeownerwith remotecontrolof a lock can choosetolet someoneinto theirhouseat any especiallybeneficialif someonelosestheirkey or doesnot needpermanentaccessto the home(for example:repairman,postalworker,and so on). Lockis AccessedAnotherbenefitof integratingWi-Fiinto an electronicsmartlock is that a usercan get a notificationanytime the lock is stateof the lock is changed,the lock can publishthat informationtothe cloudserver,whichcan thenforwarda notificationmessageon to the ,the ownerof the lock has the convenienceof knowingwhensomeoneis at example,a notificationcan be generatedwhenchildrenget backfromschoolor whenahousekeeperarrivesto cleanthe ,a notificationcan be sent to the ownerif someoneattemptsto tamperwith the lock or breakinto the internet-connectedproductslike Wi-Fienablede- locks ,it is necessaryto havea methodfor updatingthe systemfiles and files that mustbe replacedovertime are devicecertificatesand keysthat are usedby the cloudto identifyand establishsecureconnectionsto the also be requiredto enablenew features,fix existingissues,or typicallyinstalledin doors.

6 It is impracticalfor a userto removethe lock fromthe doorand use a physicalconnectionto performthe wirelessupdatemechanism,knownas an over-the-air(OTA)update,providesa simpleway to keepthe implementedwith otherlow-powerRF technologies,but theseare example,usinga low-powerpeer-to-peertechnologyrequiresa userto be physicallypresentto enablethe this case,the updateis delivereddirectlyfromthe user'smobiledevicetothe lock usinga ,dependingon the throughputprovidedby the technology,a usermay haveto wait severalminutesfor the updateto ,an e-lockwith integratedWi-Fiand internetconnectivitycan be automaticallyupdatedthroughan AP with no needfor the userto be nearthe usercan also take advantageof higherthroughputto speedup the commerciale-lockapplications,Wi-Fiintegr ationcan leadto significantsavingsin cost and time by eliminatingthe needto manuallyupdatethe Casesand December2017 SubmitDocumentationFeedbackCopyright 2017,TexasInstrumentsIncorporatedSimpleL ink Wi-Fi RemoveUsersA majorlimitationwith traditionallocksis the amountof time it takesto createa new key for a copyof a physicalkey requiresspecialmachineryand can take a long can evenbeinconvenientfor a userto physicallyaccessthe lock to createa new pin or digitalkey whenthe lock isunlockedusinga keypador a addedto an e-lockdesign,the lock can storeauthenticationlists (whitelists)eitherlocallyor in the whitelist,or list of approvedusers,will be usedto determinewhetherornot to give a useraccessbasedon a digitalkey.

7 Wheneverthe ownerwantsto add or removea user,theprocessis simple the ownercreatesa new profilewith a uniquekey and accessrestrictions,thenthenew userinformationis pushedto the lock or to the cloudas an add Wi-Fibasedfeaturesto e-locksby creatinga devicethat can bridgethe linkbetweena non-Wi-Fibasede-lockand the homeAP. Thesedevices,knownasnetworkbridges, mustbedesignedto connectthe localWi-Finetworkto the e-lockby translatingpacketsto the protocoluseddirectlyby the e-lock,suchasBluetooth low energyor networkbridgeis not an idealsolutionbecauseit increasesthe complexityof the overallsystemdesignand also increasesthe entiresystemcost for the end undesirablebecauseit usuallyrequiresa plug in the wall and takesup contrastto usinga bridge,integratingWi-Fidirectlyinto the lock reducesthe cost for the end user,simplifiesthe userexperience,and makesit possibleto developnew featuresthat rely on high datathroughputto the PowerUse CasesThereare manydistinctwaysthat Wi-Ficonnectivitycan be usedin electronicsmartlocks(e- locks ).

8 Thenumberof featuresenabledand the powerbudgetrequireddependson how the mostcommonWi-Ficonnectivityuse cases(in orderof lowest-powerto highest-powerconsumption)are as follows: Wi-Fischeduledwake-upfor periodicupdates Wi-Fiwake-upon sensorevent Wi-FialwaysconnectedThe lowestpoweruse caseis whenthe Wi-Fiis turnedon only for use caseisgenerallychosenwhenWi-Fiis not the interfacecontrollingthe lock becauseit is not ,systemsthat wakeup only for periodicupdateswill use anothermechanismfor receivingaccesscredentials,suchas a example,updatingthe whitelistfor an officebuildingor hotelroommayonly needto occuronceor severaltimesa day. A wake-upthat is scheduledto occurperiodicallycan beusedto turn on the Wi-Fiand checkfor an ,scheduledwake-upscan be usedto delivernew softwareto e-locksin the formof caseis whenthe Wi-Fiis triggeredto wakeup on a sensorevent(suchas a buttonpress,aninterruptgeneratedfroma passiveinfraredsensor,or evenanotherconnectivitydevicelike a Bluetoothlow energynetworkprocessor).

9 A triggeredwakeupcan be usefulto optimizepowerconsumptionwhilealso enablingthe systemto respondto a userapproachesa doorlock that implementsthisschemefor Wi-Fiactivity,it can use a sensorto detectthe user,thenconnectto the cloudin ordertoauthenticatethe useror senda pushnotificationto the Wi-Fisolutionmusthavea shortwakeupand connectioncycleto providethe best userexperiencewith a Wi-Fihas multiplebuilt-inmechanismsto optimizewakeupandconnectiontimesincludin gFastConnect,FastDHCPR enew,and hardwareaccelerationof ,SimpleLinkWi-Fican wakeup froma A hibernatemode,establisha WPA2securedconnectionto an AP, and createa TLS/SSLconnectionto a serverin Driver (or Drivers)Audio Amp or codecAdditional SensorsSensorsMSimpleLinkWi-Fi CC32xxSPI FlashHost or Wireless12-Button KeypadBatteriesPower ManagementHMIB rushed DC or Stepper Motor DriverLow-power RF(RFID, BLE, Sub-1 GHz)Op Amp or Fuel GaugePower Converter (Buck)4 AAs 4s:1pPWM and GPIOADCUART or SPI3 V5 V to 6 VMotor drive runs directly off of VBAT7 GPIOsI2CI2S and 12 CLegendCopyright 2017, texas instruments SystemRequirements7 SWAA169 December2017 SubmitDocumentationFeedbackCopyright 2017,TexasInstrumentsIncorporatedSimpleL ink Wi-Fi EnabledElectronicSmartLock(1)Designersmu stmakesurecoexistencerequirementsare met whenusingmultipleRF transceiversin a use casefor Wi-Fithat enablesthe widestfeatureset is whenthe Wi-Fiis secureconnectionto the cloudallowson-demandaccessto the lock and the always-connecteduse case,a usercan quicklyaccessthe lockfromanywhere,at any biggestchallengefor devicesthat implementan always-connectedpolicyis maintainingthe connectionto peersthroughthe internetwhilein an problemwith the abilityto maintainsocketstateseventhroughlow-power deepsleep(LPDS) SystemRequirementsElectronicsmartlocks(e - locks )are usuallycomposedof the followingkey functionalblocks.

10 Humanmachineinterface(HMI) Wirelessconnectivity Hostmicrocontroller Motorsubsystem Sensors PowermanagementFigure2 showsa typicalblockdiagramfor an e-locksystemwith ExampleWi-FiEnabledE-LockSystemBlockDiag ramHMI The HMI providesa methodfor the userto interactwith the systemor to viewa HMI may includea keypad,backlight,LEDs,speaker,or evena designsimplementthe HMI on a PCBthat is physicallyseparatefromthe rest of the 's MSP430 microcontroller(MCU)with CapTIvate touchtechnologyis specificallydesignedfor addinga dedicatedHMI controllerand industrialcapacitivetouchsolutionto an of the HMI functionality,suchas the keypad,to be handledon a remotedevice(suchas a smartphoneor tablet).Wirelessconnectivity Wirelessconnectivity(1)(suchas Wi-Fi,Bluetoothlow energy,Sub-1 GHz,orRFID)addsan additionaldatainterfaceto the interfacecan be usedfor variouspurposesincludingwirelessauthenti cationof the user,remotecontroland monitoring,wirelesstransferofsoftwareupd ates,or communicationwith somecases,the additionof awirelessinterfaceallowsfor part of the HMI functionalityto be handledby a remotedevice(suchasa smartphoneor tablet).