building a home security system with raspberry piprophet/raspberrypi/building... · setting up your...

BuildingaHomeSecuritySystemwithRaspberryPi

TableofContents

Credits

AbouttheAuthor

AbouttheReviewers

www.PacktPub.com

Supportfiles,eBooks,discountoffers,andmore

Whysubscribe?

FreeaccessforPacktaccountholders

Preface

Whatthisbookcovers

Whatyouneedforthisbook

Whothisbookisfor

Conventions

Readerfeedback

Customersupport

Downloadingtheexamplecode

Errata

Piracy

Questions

1.SettingUpYourRaspberryPi

WhichflavorofPi?

RaspberryPiModelA

RaspberryPiModelB

RaspberryPiModelB+andModel2

Modelcomparisontable

Sowhichone?

PreparingtheSDcard

DownloadingtheRaspbianimage

UsingMicrosoftWindows

UsingLinux

BootingyourPi

Expandingthefilesystem

Usingtheraspi-configutility

SettingupyourPi

Gettinguptodate

Gettingtherighttime

fake-hwclock

Talkingofsecurity…

Whatisthissudothinganyway?

ConnectingviaWi-Fi

Summary

2.ConnectingThingstoYourPiwithGPIO

Prerequisites

SayhellototheGPIO

DigitalI/Opins

TheI2Cbus

TheSPIbus

TheUARTserialbus

USBports

Powerconnections

GettingacquaintedwiththeGPIO

Lettherebelight

Gettingflashy…

Addingaswitch

Pullingyourselftogether

Thedetectionscript

Themostelaboratelightswitchintheworld

Theilluminatingscript

Summary

3.ExtendingYourPitoConnectMoreThings

Prerequisites

TheI2Cbus

Just2wires

What’syouraddress?

Thereisaparalleluniverse

Serial-to-parallelconversion

Givemepower

BuildinganI2Cexpander

TheI2Cportexpandercircuit

Let’swalkthroughthecircuit

Buildingyourexpansionboard

Usingready-madeexpansionboards

HobbytronicsMCP23017expanderportkit

PiFaceDigitalI/Oexpansionboard

Gertboard

Summary

4.AddingaMagneticContactSensor

Prerequisites

Theworkingofmagneticcontactsensors

SettinguptheI2Cportexpander

EnablingtheI2CBus

InstallingtheI2Ctoolspackage

Findingourdevices

Settinguptheportexpander

Connectingourmagneticcontactsensor

Monitoringthesensor

Anti-tampercircuits

Gettingintothezone

Summary

5.AddingaPassiveInfraredMotionSensor

Prerequisites

Passiveinfraredsensorsexplained

SettingupyourPIRsensor

Givemepower(again)

ConnectingourPIRmotionsensor

12Valarmzonecircuits

Alarmcircuitprotection

Howitworks

WirelessPIRmotionsensors

433-MHzwirelessalarmsystems

Connectinga433-MHzreceiver

Thealternativeapproach(becausewehavenochoice)

Thereceiverwiringdiagram

Loggingdetectiondata

Summary

6.AddingCamerastoOurSecuritySystem

Prerequisites

TheRaspberryPicameramodule

Connectingthecameramodule

Settingupthecameramodule

Testingthecameramodule

Beavideostar

Caughtoncamera

Youhavenewmail

Settingupthee-mailsenderclient

Sendingattachments

Wherewasthattaken?

Nightvision

Anilluminatingexperience

TheElaboratelightswitchre-visited

Isthatabadger?

UsingUSBcameras

Installingthewebcam

Takingasnap

Snapsnapsnap

Themulticamerasetup

TheSlavedriver

Summary

7.BuildingaWeb-BasedControlPanel

Installingthewebserver

TestingthePHP5installation

Beingincontrol

Armingyourself

Themasterconfigurationfile

Creatingthewebpage

ThecontrolpanelHTMLtemplate

Givingitsomestyle

Makingitdynamic

Gettingabitofhelpfirst

ThemainPHPcode

I’msomeoneelse

Remoteaccesstoourcontrolpanel

SettingupadynamicDNSaccount

TheRaspberryPidynamicDNSclient

SettingupastaticIPonyourRaspberryPi

Port-forwarding

Summary

8.AMiscellanyofThings

Arminganddisarmingthesystem

Drivinginductiveloads

Beyondintrusion

Asimplewaterdetector

Howitworks

Asimpletemperaturesensor

Howitworks

Acarbonmonoxidedetector

RemoteadministrationforourRaspberryPi

GettingWebmin

Updatingtherepositorysources

Importingthesigningkey

AccessingWebminlocally

RemotelyaccessingWebmin

Summary

9.PuttingItAllTogether

Alarmsystemdiagram

Overviewofthesystemelements

A+12Vpowersupply

A+3.3Vpowersupply

Theopto-isolatorinputmodule

Theportexpander

Anarm/disarmswitch

Alarmoutputs

Designingthecontrolscripts

Buildingthecontrolscript

Exploringthescriptcode

Declarations

Updatingconfigsettings

SettinguptheGPIO

SettinguptheI2Cportexpander

Decodingthezoneinputsstatus

Initialization

Thesystemmonitoringloop

Armingthesystem

Monitoringthezones

Entrydelay

Soundingthemainalarm

Disarmingandresettingthesystem

We’redone(almost)…

Automaticallystartingthesystem

PreservingtheSDcard

CreatingaRAM-basedfilesystem

Conclusion

Tipsforbuildingsystems

Summary

Allrightsreserved.Nopartofthisbookmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans,withoutthepriorwrittenpermissionofthepublisher,exceptinthecaseofbriefquotationsembeddedincriticalarticlesorreviews.

Everyefforthasbeenmadeinthepreparationofthisbooktoensuretheaccuracyoftheinformationpresented.However,theinformationcontainedinthisbookissoldwithoutwarranty,eitherexpressorimplied.Neithertheauthor,norPacktPublishing,anditsdealersanddistributorswillbeheldliableforanydamagescausedorallegedtobecauseddirectlyorindirectlybythisbook.

PacktPublishinghasendeavoredtoprovidetrademarkinformationaboutallofthecompaniesandproductsmentionedinthisbookbytheappropriateuseofcapitals.However,PacktPublishingcannotguaranteetheaccuracyofthisinformation.

Firstpublished:December2015

Productionreference:1161215

PublishedbyPacktPublishingLtd.

LiveryPlace

35LiveryStreet

BirminghamB32PB,UK.

ISBN978-1-78217-527-8

www.packtpub.com

CreditsAuthor

MatthewPoole

Reviewers

LihangLi

CédricVerstraeten

CommissioningEditor

EdwardBowkett

AcquisitionEditors

VivekAnantharaman

VinayArgekar

ContentDevelopmentEditor

SumeetSawant

TechnicalEditor

NamrataPatil

CopyEditor

AngadSingh

ProjectCoordinator

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Proofreader

SafisEditing

Indexer

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ProductionCoordinator

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CoverWork

ManuJoseph

AbouttheAuthorMatthewPooleisasystemsengineerbasednearSouthamptononthesouthcoastofEnglandwithover20yearsofindustryexperience.Aftergraduatinginelectronicsandcommunicationsengineering,hewentontotrainasandtobecomeanairtrafficengineerfortheUKCivilAviationAuthority,workingonmicroprocessor-basedcontrolandcommunicationssystems.

Later,hebecameasoftwarearchitectandmobiletechnologyspecialist,andworkedforseveralconsultanciesandglobalorganizations.HeisnowapartneratUKMobileMedia,aboutiquesystemsconsultancyfocusedondesigningBluetoothandotherwirelesssystems,takingideasfromconcepttoprototype.HeisalsothedirectoroftechnologyforMobileOnboard,aleadingUK-basedtransporttechnologycompanythatspecializesinon-busconnectivityandmobileticketing.

AbouttheReviewersLihangLireceivedhisMSdegreeincomputervisionfromNationalLaboratoryofPatternRecognition(NLPR)atInstituteofAutomationoftheChineseAcademyofSciences(CAS).HisinterestsincludeLinux,opensource,cloudcomputing,virtualization,computervisionalgorithms,machinelearninganddatamining,andavarietyofprogramminglanguages.

Youcanfindhimathispersonalwebsiteathttp://hustcalm.me.

Ithasbeenagreatopportunitybeingapartofthisbook.Ihavealwaysbeenafanofembeddeddevicesandsystems.Thanksgotoourauthorandcoordinator.Hopethereaderswillfindthisbookhelpful.

CédricVerstraetenhasanMScinengineeringandisprimarilyactiveintheC++community.Heworksasasoftwareengineerandisahugeopensourceenthusiast.Hespendsmostofhistimeonsideprojects.He’sthefounderofKerberos.io,anopensourcevideosurveillancesystembuiltfortheRaspberryPi,andistheorganizeroftheRaspberryPiBelgiummeetupgroup.

IwouldliketothankPacktPublishingformakingmeareviewerofthisbook.Ireallythinktheirbookscangivepeopleanin-depthoverviewofaparticulartopic.

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PrefaceTheRaspberryPiisapowerful,low-cost,credit-cardsizedcomputer,whichlendsitselfperfectlyasthecontrollerofasophisticatedhomesecuritysystem.Usingtheavailableon-boardinterfaces,theRaspberryPicanbeexpandedtoallowtheconnectionofavirtuallyinfinitenumberofsecuritysensorsanddevices.TheRaspberryPihastheprocessingpowerandinterfacesavailabletobuildasophisticatedhomesecuritysystembutatafractionofthecostofcommerciallyavailablesystems.

BuildingaHomeSecuritySystemwithRaspberryPistartsoffbyshowingyoutheRaspberryPiandhowtosetuptheLinux-basedoperatingsystem.ThebookthenguidesyouthroughconnectingswitchsensorsandLEDstothenativeGPIOconnectorsafely,anditalsoshowsyouhowtoaccesstheseusingsimpleBashscripts.Asyoudivefurtherin,you’lllearnhowtobuildaninput/outputexpansionboardusingtheI2Cinterfaceandpowersupply,allowingtheconnectionofthelargenumberofsensorsneededforatypicalhomesecuritysetup.

Thebookfeaturescleardiagramsandcodelistingeverystepofthewaytoallowyoutobuildatrulysophisticatedandmodularhomesecuritysystem.

WhatthisbookcoversChapter1,SettingUpYourRaspberryPi,startsoutbytakingourRaspberryPioutofitsboxandpreparingitforbeingthecenterpieceofourhomesecuritysystem.Alongtheway,wewillinstallandsetuptheoperatingsystem,connectourPitothenetwork,andaccessitremotely.We’llalsosecureourPiandmakesureitcankeeptherighttime.

Chapter2,ConnectingThingstoYourPiwithGPIO,explorestheGPIOportandthevariousinterfacesitfeatures.We’lllookatthevariousthingswecanconnecttotheRaspberryPiusingtheGPIOincludingswitchesandsensorsaswestarttobuildourhomesecuritysystem.

Chapter3,ExtendingYourPitoConnectMoreThings,looksatwaysofexpandingthenumberofthingswecanconnecttoourRaspberryPi,overcomingthelimitationofhavingjusttheeightdigitalpinsavailabletousontheGPIObytappingintootherinterfacesontheGPIOandbuildingourowninput/outputexpansionboard.

Chapter4,AddingaMagneticContactSensor,startstoactuallyconnectthingstoourhomesecuritysystem,suchasmagneticsensorsandothertypesofcontactdevices.YouwilllearnhowtoprogramourI2CexpansionportusingBashscriptssothatwecanreadthestateofoursensorsandswitchonwarningLEDs.We’llalsostarttodevelopthecontrolscriptsforoursystemthatwillallowustoarmanddisarmthesystemandadddelaytimers.

Chapter5,AddingaPassiveInfraredMotionSensor,looksatpassiveinfra-redmotiondetectors,howtheywork,andhowwecanconnectwiredandwirelesstypestoourhomesecuritysystem.We’llalsolearnhowtocreatelogfilesbasedoneventsusingBashscriptssothatwecanmaintainahistoryofdetectorstatesastheychange.

Chapter6,AddingCamerastoOurSecuritySystem,teachesyouhowtoconnectbothRaspberryPicameramodulesandUSBcamerastoourPiboardinordertotakeimageandvideocaptureswhenrequiredbyourhomesecuritysystem.We’llalsolearnhowtooverlayourimageswithinformativetextandhavethefilesimmediatelyemailedtous.

Chapter7,BuildingaWeb-BasedControlPanel,getsdowntothebusinessofstartingtoputtogethermodulesbybuildingamobile-optimizedweb-basedcontrolpanelforourhomesecuritysystem.You’lllearnhowtosetupawebserveronourRaspberryPiandmanipulatefilesusingourwebcontrolpanel,meaningwe’llstarttoexplorehowalloftheelementssofarwillcometogetheraspartofourfinalsystem.

Chapter8,AMiscellanyofThings,looksafewotherbitsandpieces,suchasaddingothersensorstoourhomesecuritysystemthatarenotnecessarilyrelatedtointruderdetection.We’llalsolookathowwecanadministerourentireRaspberryPisystemremotelyusingawebbrowserinadditiontoaccessingourhomesecuritycontrolpanel.

Chapter9,PuttingItAllTogether,isthemomentwe’veallbeenwaitingfor;we’regoingtotakealloftheelementsandconceptsfromthepreviouschaptersandputtogetherourfullsystemcomprisingtheelementswewanttofeature.Thestaroftheshowwillbeour

Bashscripts,whichwillgluetogetheralloftheseelementsandprovidethecontrollogicfortheentiresystem.

WhatyouneedforthisbookYou’llneedthefollowingsoftware:

Gpartedddfake-hwclockWin32DiskImager0.9.5PuTTYi2c-tools

WhothisbookisforThisbookisforanyonewhoisinterestedinbuildingamodularhomesecuritysystemfromscratchusingaRaspberryPiboard,basicelectronics,sensors,andsimplescripts.Thisbookisidealforenthusiasticnoviceprogrammers,electronicshobbyists,andengineeringprofessionals.Itwouldbegreatifyouhavesomebasicsolderingskillsinordertobuildsomeoftheinterfacemodules.

ConventionsInthisbook,youwillfindanumberofstylesoftextthatdistinguishbetweendifferentkindsofinformation.Herearesomeexamplesofthesestyles,andanexplanationoftheirmeaning.

Codewordsintext,databasetablenames,foldernames,filenames,fileextensions,pathnames,dummyURLs,userinput,andTwitterhandlesareshownasfollows:“Extract2015-09-24-raspbian-jessie.imgtoyourHomefolder.”

Ablockofcodeissetasfollows:

#passwd

root@raspberrypi:/home/pi#passwd

EnternewUNIXpassword:

RetypenewUNIXpassword:

passwd:passwordupdatedsuccessfully

root@raspberrypi:/home/pi#

Anycommand-lineinputoroutputiswrittenasfollows:

$sudoapt-getinstallfake-hwclock

Newtermsandimportantwordsareshowninbold.Wordsthatyouseeonthescreen,inmenusordialogboxesforexample,appearinthetextlikethis:“TypetheIPaddressoftheRaspberryPiintotheHostNameboxandclickonOpen.”

NoteWarningsorimportantnotesappearinaboxlikethis.

TipTipsandtricksappearlikethis.

ReaderfeedbackFeedbackfromourreadersisalwayswelcome.Letusknowwhatyouthinkaboutthisbook—whatyoulikedormayhavedisliked.Readerfeedbackisimportantforustodeveloptitlesthatyoureallygetthemostoutof.

Tosendusgeneralfeedback,simplysendane-mailto<feedback@packtpub.com>,andmentionthebooktitleviathesubjectofyourmessage.

Ifthereisatopicthatyouhaveexpertiseinandyouareinterestedineitherwritingorcontributingtoabook,seeourauthorguideonwww.packtpub.com/authors.

CustomersupportNowthatyouaretheproudownerofaPacktbook,wehaveanumberofthingstohelpyoutogetthemostfromyourpurchase.

DownloadingtheexamplecodeYoucandownloadtheexamplecodefilesforallPacktbooksyouhavepurchasedfromyouraccountathttp://www.packtpub.com.Ifyoupurchasedthisbookelsewhere,youcanvisithttp://www.packtpub.com/supportandregistertohavethefilese-maileddirectlytoyou.

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Chapter1.SettingUpYourRaspberryPiBeforewecangetintotherealmsofbuildingourhomesecuritysystem,there’sabitofpreparationworkneededtogetourRaspberryPiupandrunning.So,we’regoingtogothroughtheinitialstepsneededtogetourPireadytobeworkedon.

Inthischapter,wewillcoverthefollowingtopics:

ExploringthedifferentversionsoftheRaspberryPithatareavailableChoosingtherightRaspberryPiversionforyoursystemPreparingtheSDCardwiththeRaspbianOperatingSystemLearninghowtoremotelyaccesstheRaspberryPioveryourhomenetworkUpdatingouroperatingsystemwiththelatestpackagesExploringthetime-keepingoptionsontheRaspberryPiSettingtheuserandrootpasswordstosecureourRaspberryPi

WhichflavorofPi?SincetheRaspberryPiwasreleasedin2012,therehavebeenseveralversionsofthemini-PCboardreleased.I’llgothougheachoftheversionsreleasedwiththeirrespectivefeaturessothatyoucanchoosewhichoneissuitableforyourparticularproject.

Thegoodnewsisthatitdoesn’treallymatterwhichversionyouuseintermsofpower,asourhomesecuritysystemdoesn’tnecessarilyneedloadsofprocessingpower,dependingonwhatyouwantyoursystemtodo,ofcourse).Youmighthaveanolderboardkickingaboutthatwillworkforyou.

TheotherpieceofgoodnewsisthattheGPIOinterfacepinlayoutsarethesameacrossalltheversions.Thelaterversionshavemorepins,buttheoriginal26pinsstillremaininthesameplace.

ThelatestRaspberryPiVersion2

RaspberryPiModelAThebabyofthefamilyistheModelA;itwasreleasedasalower-costversionoftheModelB,showninthefollowingsection.ItsmaindifferencesfromtheModelBarethatitfeaturesjust256MbofmemoryandhasnoEthernetport;soifyouwanttoconnectthisboardtoanetwork,youarelimitedtousingaUSBWi-Fidongle.

TheRaspberryPiModelABoardLayout

RaspberryPiModelBThiswasthefirstversionofRaspberryPitobereleased;anupdatedrevision,whichimprovedthepowersystemandUSBportprotection,camelater.Itfeatures512MbofmemoryandhasanEthernetportforconnectingtoyournetwork.Thisisprobablythemostcommonversionused,andhavingtheEthernetportisincrediblyuseful,especiallytogetupandrunquicklyinordertosetupandconfigureyourPiwithouttheneedforakeyboardandmonitor.

TheRaspberryPiModelBLayout

RaspberryPiModelB+andModel2In2014,theRaspberryPiFoundationreleasedanewversionoftheboardthathadsomefundamentalchangesascomparedtothepreviousversion.Themostfundamentalchangesweretheboardlayout,formfactor,andmountingpoints—muchtothedismayofthemanyenclosureandaccessorymanufacturersoutthere.

Infact,wewereinthemiddleofprototypinganenclosureforacommercialproductthatweweredevelopingbasedontheRaspberryPi—fortunatelywecaughtwindoftheboardchangeinthenickoftimeandwereabletochangeourenclosuretosupporttheupcomingmodelB+.

Themainelectronicchangestothisboardaretheadditionof2moreUSBportsthatcandelivermorepowertoperipherals,anexpandedGPIOinterface,andtheremovalofthecompositevideoportthatisnowconsolidatedintotheaudiojack.ItalsonowusesamicroSDcardwithabettercardslot.

InFebruary2015,amorepowerfulRaspberryPiwasreleased:theRaspberryPiModel2.It’ssimilartotheModelB+intermsofform-factorandinterfaces,butisnowreportedly6-timesfasterthantheModelB/B+withitsupgradedARMprocessorand1Gbofmemory.

Atthesamelowcostoflessthan£30,it’safantasticlittleboardandagreatpower-houseforembeddedsystems.

TheRaspberryPiModelB+andModel2Layout

Modelcomparisontable ModelA ModelB ModelB+ Version2

ProcessorARM1176JZF-S700MHzprocessor,

VideoCoreIVGPU

Quad-coreARMCortex-A7CPUandaVideoCoreIV

dual-coreGPU

Memory 256Kb 512Kb 512Kb 1Gb

USBPorts 2 2 4 4

Ethernet No Yes Yes Yes

No.GPIO

Pins26 26 40 40

Storage SDCard SDCard MicroSDCard MicroSDCard

Sowhichone?Essentially,anyversionoftheRaspberryPiwillworkwiththemodulespresentedinthisbook,butifyouwanttoexploitfeaturessuchasthecamera,whichmayrequiremoreprocessingpowerandmemory,orwanttohaveanEthernetconnection,you’llneedtousetheModelB.

IfyouwanttostartpluggingadditionalstuffintotheUSBport,suchasaGSMmodem,thenIrecommendthatyouusetheModelB+asitdeliversmorepowertothosekindsofdeviceswithouttheneedforadditionalUSBhubs.

Ifyouwanttodomoreprocessingwithvideoandimagesfromanattachedcamera,orwanttoconnectlotsofthings,thengoforthelatestModel2board.I’mgoingtoassumethat’stheoneyouhavechosenforthisproject,andthat’stheoneI’llbeusingthroughoutthisbook;justbeawareofanylimitationsifyouchoosetouseanearliermodel.

NoteTheRaspberryPiFoundationsitehasmoredetailedinformationabouteachmodel.Youcanvisititathttps://www.raspberrypi.org/products.

PreparingtheSDcardTheRaspberryPionlybootsfromanSDcard(ormicroSDcardfortheB+andv2models),andcannotbootfromanexternaldriveorUSBstick(wellthat’snotstrictlytrue,butisbeyondthescopeofthisbook).

It’srecommendedthatyouuseaClass10SDcardforperformance,butaClass4or6cardwillbefineforthisproject.You’llneedtohaveaminimumcardsizeof4Gb.

NowthatwehaveourRaspberryPiboardandSDcardtohand,weneedtopreparetheSDCardspecificallyforourhomesecuritysystem.We’regoingtousethestandardRaspbianoperatingsystemastherereallyisnoreasontouseanyotherdistribution;it’sthedefactochoicefortheRaspberryPi.

DownloadingtheRaspbianimageYou’llneedtograbthelatestRaspbianOSimagefromtheRaspberryPisiteathttps://www.raspberrypi.org/downloads.

DownloadtheRaspbianOSZIPfilecontainingtheimagetoyourPC.

NoteAtthetimeofwriting,thelatestversionwasRaspbianJessieversion4.1(2015-09-24-raspbian-jessie.zip).

Oncedownloaded,unzipthefileandyou’llhavethefile,2015-09-24-raspbian-jessie.img.

ThenextthingtodoisburnthisimagetoyourSDcard…

UsingMicrosoftWindowsOnaWindowsPC,thebestwaytoburntheimagetoyourSDcardistousetheWin32DiskImagerutility.Thiscanbedownloadedfromhttp://sourceforge.net/projects/win32diskimager.

NoteThecurrentversion,atthetimeofwriting,is0.9.5.

Itdoesn’thaveaninstaller,andlaunchesdirectlyfromtheEXEfile.

Now,it’stimetocreateyourSDcardimage:

1. InsertyourSDcardintothePCandlaunchtheWin32DiskImager.2. SelecttheSDcarddevicedriveletter(makesureit’sright!).3. ChoosetheRaspbianimagefileyou’vejustdownloaded.4. ClickontheWritebuttontocreatetheSDcardimage.

UsingLinuxOnaLinuxPC,you’llneedtousethegpartedandddutilitiestoburntheimageonyourSDcard.

CarryoutthefollowingstepstocreateyourSDcardimage:

1. Extract2015-09-24-raspbian-jessie.imgtoyourHomefolder.2. InsertyourSDcardintothePC.3. Ifyou’renotalreadyinashellterminalwindow,openone(youcanuseCtrl+Alt+T

onmostgraphical-baseddesktopsystems).4. Typethefollowingcommandintheshellterminal:

$sudofdisk-l

Inthelistcheck,yourSDcardappearsasadrivedevice(forexample,/dev/sdb).It’scrucialthatyouensureyouusetherightdeviceinthenextstep.We’llassumethatyourdeviceis/sdb.

5. ToburntheimagetotheSDcard,typethefollowingcommand:

$sudoddif=2015-09-24-raspbian-jessie.imgof=/dev/sdb

6. HitEnterandgomakeacupofteaorcoffeeasthiswilltakeawhile.You’llknowthatit’sfinishedwhenthecommand($)promptre-appears.

7. Whenthecommandpromptdoesre-appear,typethefollowingcommand:

$sudosync

8. Oncethatcommandhasfinished,youcanremovetheSDcardfromthePC.

BootingyourPiYou’renowreadytobootupyourRaspberryPi.PopyourshinynewSDcardintoitandpluginthepower.

AssumingthatyouhaveamonitorattachedtoyourPi,youshouldseeyoursystembootingupnicely.Althoughyoucouldwaitforittobootupandconnecttoitviaaterminalsession(we’lllookatthatlater),Irecommendthatyouconnectamonitortoit,atleastinthefirstinstance,justtomakesureeverythingisworkingcorrectly.

InthenewJessieversionofRaspbian,you’llbootstraightintoadesktopGUI,whichisamajorchangefrompreviousversions,whereyou’dbetakentotheraspi-configutility,thefirsttimethesystemisrun,whereyou’dsetupyourPi,andimportantly,expandthefilesystemtousetheentirespaceavailableonyourSDcard.

DebianJessiebootsintotheGUIbydefault

ExpandingthefilesystemWhenyoufirstcreateyourRaspbianSDcard,you’llonlybeleftwithabout200Mbofspaceinthefilesystem,regardlessofthesizeofyourSDcard.Thisisnotmuchuse,sowewanttoexpandthefilesystemsothatitusesalloftheavailablespaceonthecard.

Fortunately,thisisveryeasyontheRaspberryPinow,asthisfunctionisavailableintheRaspberryPiConfigurationToolonthedesktop.

Toaccessthenewconfigurationtool,gotoMenuandselectPreferences|RaspberryPiConfiguration.

ThenewRaspberryPiConfigurationTool

TipGoodbyeGUI

Mostofourworkisgoingtobedoneinthecommand-lineinterface(CLI).Therefore,beforewerebootthesysteminaminute,let’schangetheBootoptionbyselectingToCLI,asshowninthepreviousscreenshot,sobootintothecommandlinegoingforward.

Anyway,nowweclickontheExpandFilesystembutton,andinacoupleofseconds,you’llseeaconfirmationmessage.Thefilesystemwillbeexpandedwhenthesystemnextreboots.

Usingtheraspi-configutilityIfyouhaveanolderversionofRaspbian,oryou’renotusingthedesktopGUI,thenyou’llneedtousetheraspi-configutility(whichisstillbetterthantheolddayswhenwehadtodothismanuallyintheshell).Thefirsttimeyoubootup,you’llbetakenstraighttothe

raspi-configutility.

ThefirstoptionistheExpandFilesystemoption;selectthisandyou’llseevariouscommandsscrollingupthescreen.Onceit’sfinished,you’llseethefollowingmessage:

Rootpartitionhasbeenresized.

Thefilesystemwillbeenlargeduponthenextreboot

ClickonOK.

SelectFinishontheconfigscreenandrebootyourPiwhenprompted.

AfteryourPirebootswithitsfullerfilesystem,you’llbetakenstraighttotheshellpromptwhereyoucanloginwiththedefaultuserandpassword.

Login:pi

Password:raspberry

SettingupyourPiWhenyoubootintotheshellandhavetheEthernetconnected,hopefullythePiwillhaveconnectedtoyourhomenetworkandacquiredanIPaddressfromyourrouter.Ifthisisthecase,youshouldseetheIPaddressthathasbeenissuedjustbeforetheloginprompt,asshowninthefollowingscreenshot:

Asyoucanseefrommyscreenshot,it’sgivenmetheIPaddress,192.168.0.118.ThisisgoodbecauseIcannowaccessthePiremotely,usingasecureshell(SSH)clienttoconnecttoitfromthecomfortofmylaptop.ThisisparticularlyusefulwhenmyPiisintheofficeandIwanttositonmysofainfrontofthetellybutstillworkonit,whichIoftendowhenI’mfeelinglazy.

TipDownloadingtheexamplecode

Youcandownloadtheexamplecodefilesfromyouraccountathttp://www.packtpub.comforallthePacktPublishingbooksyouhavepurchased.Ifyoupurchasedthisbookelsewhere,youcanvisithttp://www.packtpub.com/supportandregistertohavethefilese-maileddirectlytoyou.

Todothis,downloadPuTTY:autilitythatallowsyoutoconnecttoshellterminalsremotelyoverthenetwork.Youcandownloaditfromhttp://www.putty.org.

InstallandlaunchPuTTYandyou’rereadytoconnecttoyourPiremotelyfromthecomfortofyoursofa.

TypetheIPaddressoftheRaspberryPiintotheHostNameboxandclickonOpen.You’llbeconnectedtoyourPiinaremoteterminalwindow.Onceyou’veloggedin,youcandoprettymucheverythingonyourPi,asifyouweresittinginfrontofit.

We’llassumefromnowonthatmostoftheworkwedowillbethrougharemoteshellsession,unlesshighlightedotherwise.

IfyouwanttousethecommandlinetolaunchtheRaspberryPiremoteshell—forexample,fromanotherLinuxsystem—usethefollowingcommandfromyourterminalwindow:

#sshpi@192.168.0.125

You’llthenbepromptedforthePi’spasswordandtakenintoashellsession.

ThePishellsessionlaunchedfromaDebiandesktopterminalwindow

GettinguptodateSomethingthatyoushouldgetintothehabitofdoingisupdatingtheoperatingsystemregularly;eventhoughyoumayhavethelatestimageinstalled,it’sverylikelythatthereareupdatedpackagesavailable.ToupdateyourOS,enterthefollowingcommand:

$sudoapt-getupdate

Afterthis,enterthefollowingone:

$sudoapt-getdist-upgrade

Thismaytakeawhile,dependingonthenumberofupdatesrequired.

GettingtherighttimeTheRaspberryPidoesn’thaveon-boardreal-timeclockhardware.Thisisoneofthedeliberateomissionstokeepthecostoftheboarddown.Instead,thePigetsitstimewhenitbootsupfromtimeserversontheInternetusingtheNetworkTimeProtocol(NTP).However,ifthereisnoInternetconnectionatthetimeofbootingup,thenthetimewillbewrong.

NoteInoursecuritysystem,it’simportantthatthetimeiskeptaccuratesothattimestampsonlogfilesandimagesarecorrect.

fake-hwclockThefake-hwclockpackageisincludedinthelatestRaspbiandistributions,butinotherpastversionsitwasn’t.Ifyouneedtoinstallit,usethecommandthatfollows:

$sudoapt-getinstallfake-hwclock

fake-hwclockisusedbytheRaspberryPitotryandkeeptimewhenthereisnonetworkconnection.Itwillregularlysavethecurrenttimeandrestoreitatboot-up.TheobviousproblemwiththisisthatifthePihasbeenswitchedoffafewdays,thenthetimewillbesettothelasttimethatitwason,usingfake-hwclock.

Ifyouwanttoseewhattimeitlastlogged,typethefollowingcommand:

$cat/etc/fake-hwclock.data

ntpTheNetworkTimeProtocol(NTP)isusedwhenthereisanInternetconnectionavailableanditcanrequestthelatestmostaccuratetimefromoneormoretimeserversontheInternet.

Bydefault,thentpserviceisenabledonthelatestRaspbiandistribution,butitwillinitiallygetitstimeatboot-upfromfake-hwclockifthereisnoInternetconnection.Theremaybetimeswhenit’snecessarytoforcethentpservicetoupdatefromtheInternet—forexample,iftheInternetconnectionisrestoredsometimeafterboot-up.

ToforcethentpservicetoupdatefromtheInternet,usethefollowingcommands:

$servicentpstop

$ntpd–gq

$servicentpstart

Talkingofsecurity…There’snopointinhavingasecuritysystemifthesystemitselfisnotsecure.So,nowwe’llchangethedefaultpasswordforthepiuser.

Fromtheprompt,typethefollowingcommand:

$sudopasswdpi

pi@raspberrypi~$sudopasswdpi

Whatisthissudothinganyway?You’dhavenoticedthatwe’vebeenputtingsudoatthestartofeachcommandthatwerunintheterminalwindow.Thisissothatcommandsarerunastherootuser—thehighestsecuritylevel.Thiselevatedsecurityisrequiredtoperformmanyoperations.sudoactuallymeanssuperdo.

Ifyoucan’tbebotheredtotypesudoeverytime,thenyoucanswitchtothesuperuserbytypingthefollowing:

$sudosu

You’llseethatthepromptchangedfroma$toa#,whichindicatesthatyouarenowrunningastherootuser.

So,thismightbeagoodtimetochangetherootuserpasswordtoo!Todothis,typethefollowing:

#passwd

root@raspberrypi:/home/pi#passwd

root@raspberrypi:/home/pi#

ConnectingviaWi-FiYoucanalsoconnectyourRaspberryPitoyournetworkusingWi-FibypluggingaUSBdongleintoit.Thereareadditionalconfigurationstepsrequiredtomakethiswork,whicharebeyondthescopeofthischapter,buttherearemanyresourcesavailablecoveringthissubject.

NoteYoucanfindrecipesforconnectingyourRaspberryPiusingWi-FiintheRaspberryPiNetworkingCookbookbyRickGolden,publishedbyPacktPublishing(https://www.packtpub.com/hardware-and-creative/raspberry-pi-networking-cookbook).

SummaryInthischapter,wetookourRaspberryPioutofitsboxandpreparedittobethecenterpieceofourhomesecuritysystem.Alongtheway,weinstalledandsetuptheoperatingsystem,connectedourPitothenetwork,andaccesseditremotely.WealsosecuredourPiandmadesureitcouldkeeptherighttime.

Inthenextchapter,we’regoingtoexploretheGPIOportandthevariousinterfacesitfeatures.We’lllookatthevariousthingswecanconnecttotheRaspberryPiusingtheGPIOport,includingswitchesandsensors,aswestarttobuildourhomesecuritysystem.

Chapter2.ConnectingThingstoYourPiwithGPIOTheRaspberryPihaslotsofwaystoconnectthingstoit,suchaspluggingthingsintotheUSBports,connectingdevicestotheon-boardcameraanddisplayports,andconnectingthingstothevariousinterfacesthatmakeuptheGPIOconnector.Aspartofourhomesecurityproject,we’llbefocusingmainlyonconnectingthingstotheGPIOconnector.

Inthischapter,wewillcoverthefollowingtopics:

ExaminingtheGPIOconnectorandwhateachofthepinsdoesLearningabouttheI2CandSPIbusesthatwillbeusedinlaterchaptersConnectinganLEDandaswitchsafelytothedatapins,andaccessingthesedatapinsusingsimplescriptsUnderstandingtheUSBportsandtheirlimitations

PrerequisitesAlongwithyourRaspberryPi,you’llneedthefollowingpartsfortheprojectsinthischapter:

AbreadboardAnLEDA220ohmresistor(red,red,black)A10Kohmresistor(brown,black,orange)ApushbuttonortoggleswitchAhook-upwire:

Ourlittlecollectionofparts

SayhellototheGPIOTheGPIOconnectoristhelargegroupofpinsontheedgeofyourRaspberryPiboard.Onearliermodels,therewere26pinsthatmadeupthisconnector.But,eversincetheModelB+,therehavebeen40pins,althoughthefirst26pinsareidenticaltothepreviousmodels,andit’sthese26pinswe’llbeworkingwith.Youwon’tneedtoworryabouttherestofthepins.

Essentially,theGPIOconnectorprovidesaccesstofollowing:

PowersuppliesDigitalI/OpinsI2CbusSPIbusUARTSerialbus

SomeofthepinsontheGPIOhavemorethanonepurpose,dependingonhowtheyareprogrammed.ThefollowingdiagramisareferenceguidetoallofthepinsontheGPIO.TheGPIOnumbersontheyellowlabelsrelatedirectlytothoseontheBroadcomchip,andarenumbersgenerallyusedwithinthescripts.

DigitalI/OpinsTheGPIOhas8digitalinput/outputpinsavailableforuse.Thesecanbeusedtoswitchthingsonandoff(inoutputmode),andalsotodetectwhenexternalthingsareswitchedonandoff(inputmode).Eachpincanbeconfiguredindependentlyforinputoroutputoperation,andIhavelabelledthemD0toD7intheprecedingdiagram.

Obviously,ifweweretouseeachofthesepinstodriveorsenseanindividualdevice,wewouldbelimitedtoamaximumof8devicesthatcouldbeconnectedtoourhomesecuritysystem.Inmanyscenarios,thisisprobablynotenough,sointhenextchapterwe’lllearnhowtousetheGPIOtoconnectmanymorethingstoourRaspberryPi.

TheI2CbusTheInter-IntegratedCircuit(I2C)busisalow-speedinterfacethatcanconnectmultipledevicesandsimplesensorsusinga2-wireinterfacewithouttheneedforaseparateclockordeviceselectline.Typically,thisbuscanoperateatspeedsupto100kbit/s.We’llbecoveringthisinthenextchaptertohelpusexpandourdigitalI/Oandconnectmorethings.

TheSPIbusTheSerialPeripheralInterface(SPI)busisasynchronoustwo-wayserialconnectionbetweenamasterandaslavedevice.Itcanbeusedtoaccessmorecomplexsensorsordrivedisplays.

Themasterdeviceprovidesthesynchronization,andeachtransmissionissynchronizedbyaclockpulseonSCLK(GPIO11/pin23).DataistransmittedontheMOSI(master-out-slave-in)andMISO(master-in-slave-out)(pins19and21respectively).

TheUARTserialbusTheUniversalAsynchronousReceiverandTransmitter(UART)busisawaytocommunicatewithexternaldevicesoveraserialdataconnection,andisacommonwayfortheRaspberryPitoaccessdatafromdevicessuchasGPSmodules,whichoftencomewithserialconnections.ItcanbealittlebitfiddlygettingthePisetuptocommunicatewithUART-connecteddevices,asit’salsotiedinwiththeoperatingsystem’sserialconsole.

USBportsWe’reprobablyallfamiliarwithUniversalSerialBus(USB)portsasweusethemtoconnectallsortsofthingstoourPCs,suchaskeyboards,mouses,andharddisks.OntheRaspberryPi,it’sjustthesame;wecanconnectkeyboards,mouses,anddonglestogiveusWi-FiandBluetoothconnectivity.

OfficialRaspberryPiUSBWi-FiDongle

OnearlierRaspberryPimodels,theamountofcurrentthattheportsdeliveredwasprettylowandcausedallsortsofproblemsiftoomuchcurrentwasdrawnbytheconnecteddevices.ThiswassignificantlyimprovedfromthemodelB+onwards,andit’snowpossibletoconnectGSM/LTEdongleswithoutanyproblems.

Therearestilllimitations,however,ifyouwanttoconnectthingssuchasharddiskdrives;thesecanstilldrawmorecurrentthanwhatcanbesuppliedbytheRaspberryPiUSBports,soit’srecommendedthatapoweredUSBhuborUSBpowerinjectorbeusedwhenconnectingthesetypesofdevicestoyourPi.

PowerconnectionsTheGPIOconnectoralsoprovidesaccesstotheon-boardpowersupplies.The+5Vconnection(pins2and4)isessentiallythe+5Vinputfromtheexternalpowersupplyconnectedtothemicro-USBpowerport.Thiscanbeusedtopowersmallexternalcircuitsifnecessary,althoughitisrecommendedthatanadditionalexternal+5Vsupplybeusedifsignificantcurrentisrequired.

The+3.3Vsupply(pins1and17)istheoutputfromtheon-board3.3Vregulatorandprovidesasmallamountofcurrentupto50mA.Ifyouneedtodrawmorethan50mAforyourexternalcircuits,thenyoushoulduseanexternalpowersupply.I’llshowyouhowtobuildonelaterinthisbook.

NoteTheI/OpinsontheRaspberryPioperateat3.3Vlevels.ConnectingvoltageshigherthanthistothepinscouldirreversiblydamageyourPi.Ifyoufollowtheinstructionsinthisbook,theneverythingshouldbefine,butrandomlyconnectingthingstoyourPithatuselotsofpowerwillbreakit!

GettingacquaintedwiththeGPIOBeforeweembarkonconnectinglotsofthingstoourPiboard,itmightbeagoodideatojustgetacquaintedwiththeGPIOthroughacoupleofsimpleprojectsthatwillhelpusunderstandhowtointeractwiththedigitalI/Opinsusingshellscripts.

LettherebelightThissimplelittleprojectshowshowtoconnectaGPIOoutputtoanLED,andswitchitonandoffusingshellcommands.

Thefollowingdiagramshowshowtoconnectupthecircuitusingabreadboard:

NoteTheprettydiagramthatyoujustsawwasproducedusingafreesoftwaretoolfromfritzing,whichisanopen-sourcehardwareinitiativetomakeelectronicsaccessibleascreativematerialforanyone.Downloaditfromfritzing.org.

TheLEDanode(thepositiveside)isconnectedtotheD0digitalI/O(pin11oftheconnectororGPIO17).Whenthispinisswitchedon,itwillprovidea3.3VsupplytotheLED.

TheLEDisconnectedtotheGroundpinviaa220Rresistoronthecathode(negativeside).TheresistorlimitsthevoltagetotheLEDandthecurrentthroughit,otherwiseitwouldburnout,asyoucanonlysupplyuptoabout2VtoLEDs.Withacurrentofaround10mAbeingdrawnbytheLEDona3.3Vsupply,a220RresistorworkswelltoprotectbothitandtheGPIO.

Here’sthecircuitdiagramforit:

NoteCalculatingLEDResistorValues…

Whilethisbookisnotreallyacourseonelectronicstheory,IthoughtitwouldbehandytoshowyouhowtoworkouttheresistorvaluesforLEDsusingOhmsLaw,aswe’llbecoveringthisagainlater.

AsImentioned,atypicalLEDwilldropabout2Vacrossit,althoughthisvariesaccordingtocolorandtype.ThisiscalledtheforwardvoltageofthedeviceorVLED.

ThecurrentrequiredbyanLEDisaround10mA,againdependingonitsspecification.We’llcallthiscurrentflowingthroughtheLED,ILED.

Essentially,thevoltageacrosstheresistorwillbethesupplyvoltageminusthevoltagedropacrosstheLED(forexample,.2V).So,ifwehavea12Vsupply(VS),thevoltageacrosstheresistorwillbe10V(VS–VLED).

AccordingtoOhmsLaw,theresistanceRisthevoltageacrossitdividedbythecurrentflowingthroughit:R=V/I.Aswerequire10mAflowingthroughit,withavoltageof10Vacrossit,theresistancerequiredis10Vdividedby0.01A,whichis1,000ohmsor1K.

Insummary,R=(VS-VLED)/ILED.

Now,toturntheLEDonandoff:theGPIOpinsareactuallymappedasdevicesintheLinuxfilesystem,sousingshellcommandsiseasy,althoughtherearemanylibrariesavailableouttherethatallowyoutocontroltheGPIOusingPython,forexample.However,sothatyoudon’thavetolearnanewlanguage,we’regoingtodoeverythingusingshellcommands.

TheD0pinthatweareconnectedtoisactuallyGPIO17asfarastheRaspberryPiisconcerned(takealookatthepreviousdiagramforreference).ThefirstthingweneedtodoiscreatefileaccesstothisGPIOpin.Wedothiswiththefollowingcommand:

$sudoecho17>/sys/class/gpio/export

Wethenhavetosetthepin’sdirectiontoout:

$sudoechoout>/sys/class/gpio/gpio17/direction

NextwecanswitchthepinontoturntheLEDon:

$sudoecho1>/sys/class/gpio/gpio17/value

ToswitchtheLEDoff,weusethiscommand:

$sudoecho0>/sys/class/gpio/gpio17/value

Oncewe’vefinishedwithaGPIOportwecanremoveitsfileaccess:

$sudoecho17>/sys/class/gpio/unexport

Gettingflashy…WecanputthesecommandstogetherinasingleBashscripttocreateaflashingLED.Tocreatetheflashyscript,createanewtextfileinnanoorsomeothertexteditor.Or,asIusuallydo(don’tforgetthatI’mquitelazy),createthetextfileonyourlaptop,andthencopyittotheremotePiusingWinSCP(although,readmynoteintheboxthatfollowsifyouwanttopreventsomeheartache).

Thefollowingisthecodelistingforled-flash.sh:

#!/bin/bash

sudoecho17>/sys/class/gpio/export

sudoechoout>/sys/class/gpio/gpio17/direction

#loopforever

whiletrue

sudoecho1>/sys/class/gpio/gpio17/value

sleep0.5

NoteIfyouuseWindowstocreateyourfiles,remembertosaveyourfileswiththeend-of-lineformatbeingLinux(asingle0x0aorLineFeedcharacter)ratherthanWindows(0x0a+0x0dorLineFeed+CarriageReturncharacters),otherwiseyoumightfindthatyourBashscriptdoesnotrunproperlyontheRaspberryPi.TexteditorsonWindows,suchastheexcellentNotepad++,willconvertyourscriptlineendsforyou.

Runthescriptbycallingled-flash.sh(assumingthat’swhatyou’vecalledit).Ifyou’reinthesamedirectoryasthescript,thiscanbedonebytypingthefollowing:

$sudobash./led-flash.sh

SincethisisanendlessloopwiththeLEDflashingonandoffathalfsecondintervals,you’llneedtobreakoutofitbyusingCTRL+Ctostopthescript.

Don’tforgettoremovetheGPIOpinfromfileaccessbyusingthefollowingcommand:

Otherwise,you’llseetheerror,echo:writeerror:Deviceorresourcebusy,ifyoure-runthescript,asthefirstlinetriestosetGPIO17forfileaccessagain.

AddingaswitchInthisproject,we’llseehowtoconnectaswitchtoaGPIOinputandwriteashellscripttoreadthestateoftheswitch—thatis,whetherit’sswitchedonoroff.

ConnectaswitchtoyourPi’sGPIO27pin,asshowninthefollowingdiagram:

PullingyourselftogetherAreallyimportantthingtorealizeaboutGPIOinputsisthattheyareinwhat’scalledafloatingstate.Thismeansthat,asfarastheoperatingsystemisconcerned,itdoesn’tknowwhatitsreferencestateisunlessitispresentedwithaknownvoltage.

Thisiswhereourresistorcomesintoplay—itpullsuptheGPIOpintoaknownvoltageof3.3V,whichgivesitadefaultstateofHIGH(orbinary1).

Whenthepushbuttonswitchispressed,thistakestheGPIOpinto0V,whichisaLOWstate(orbinary0).

Here’sthecircuitdiagramforourGPIOswitch:

ThedetectionscriptNowthatwe’veconnectedtheswitchtoourRaspberryPi,weneedtowritealittlescriptthatwilldetectwhentheswitchhasbeenpushed.

It’ssimilartothepreviousLEDscriptshown,butthistimewe’llsettheGPIOpinasaninputandreaditslogiclevel.

Inthisproject,we’veconnectedourswitchtoD2,whichisGPIO27(again,refertotheearlierGPIOpin-outdiagram).Asbefore,weneedtocreatefileaccessforthepinbyenteringthefollowingcommand:

$sudoecho27>/sys/class/gpio/export

Andnow,setitsdirectiontoin:

$sudoechoin>/sys/class/gpio/gpio27/direction

We’renowreadytoreaditsvalue,andwecandothiswiththefollowingcommand:

$sudocat/sys/class/gpio/gpio17/value

You’llnoticethatitwillhavereturned1,orahighstate.Thisisbecauseofthepull-upresistorweweretalkingaboutearlier.Thismeansthatitsdefaultstate,whentheswitchisn’tpushed,ishigh.

Whentheswitchispushed,thevalueshouldbereadas0orlow.Ifyouhavemorethantwohands,youcantrythisbypushingthebuttonandre-runningthecommand.Or,wecanjustcreateascripttopolltheswitchstate.

Thecodelistingforpoll-switch.shisasfollows:

#!/bin/bash

sudoechoin>/sys/class/gpio/gpio27/direction

#loopforever

whiletrue

#readtheswitchstate

SWITCH=$(sudocat/sys/class/gpio/gpio27/value)

if[$SWITCH==1];then

#switchnotpushedsowaitforasecond

sleep1

#switchwaspushed

echo"You'vepushedmybutton"

Whenyourunthescriptandthenpushthebutton,youshouldseeYou'vepushedmybuttonscrollinguptheconsolescreenuntilyoustoppressingit.

Don’tforgetthat,oncewe’vefinishedwiththeGPIOport,wecanremoveitsfileaccess:

We’venowseenhowtoeasilyreadaswitchinput,andthesamecircuitandscriptcanbeusedtoreadothersensors,suchasdoorcontactswitches,reedswitches,oranythingelsethathasanonandoffstate.

ThemostelaboratelightswitchintheworldBycombiningthetwolittleprojectsearlier,wecannowcreateasystemthatwilldosomethingusefulwhenthepushbuttonswitchispushed—forexample,switchingontheLEDthatwealsohaveconnected.Granted,wecouldjustconnecttheLEDdirectlytotheswitchandabattery,butnotonlywouldthatbeboring,itwoulddefeatthepointofwhatwe’retryingtodo,whichisprogrammaticallysensingandcontrollingthings.

Here’sthebreadboardlayoutforourelaboratelightswitch:

Andhere’sthecircuitdiagram:

TheilluminatingscriptOurfullBashscriptforourelaboratelightswitchisdemonstratednext.Thiswillloopendlessly,detectingthestateoftheswitchGPIOpin,andwillturnontheLEDGPIOpinwhentheswitchispushed.

Thecodelistingforlight-switch.shisasfollows:

#!/bin/bash

#setuptheLEDGPIOpin

#setuptheswitchGPIOpin

#loopforever

whiletrue

#readtheswitchstate

SWITCH=$(sudocat/sys/class/gpio/gpio27/value)

#0=Pushed1=NotPushed

if[$SWITCH="1"]

#switchnotpushedsoturnoffLEDpin

#switchwaspushedsoturnonLEDpin

#shortdelay

sleep0.5

So,hereweare—wehaveascriptthatwilldetectaninputstateanddosomethinginresponse;inthiscase,itwillswitchonanLED.We’renowformingthebasisofhowwearegoingtoputtogetherourhomesecuritysystem.

NoteRemember,don’tconnectanythingtoyourRaspberryPiinplaceoftheLED,suchasabuzzeroranyotherdevicethatconsumeslotsofcurrent.Thisislikelytoirreversiblyrenderyourboarddead.We’lllookatways,lateroninthisbook,tocontroldeviceswithhigherpowerrequirements.

SummaryInthischapter,weintroducedvariouswaystoconnectyourRaspberryPitotheoutsideworldbylookingatthevariousinterfacesavailableontheGPIO.We’veunderstoodhowtoconnectthingstothedigitalpinsonyourRaspberryPi’sGPIOconnector,andcontrolandreadthemusingsimpleBashscripts.Inparticular,we’vesafelyandproperlyconnectedaswitchtoadigitalinputpin,whichwillformthefoundationforourhomesecuritydetectioncircuits.

Inthenextchapter,we’lllookatwaystoexpandthenumberofthingswecanconnecttoourRaspberryPi,overcomingthelimitationofhavingjustthe8digitalpinsavailabletousontheGPIObytappingintootherinterfacesontheGPIOandbuildingourowninput/outputexpansionboard.

Chapter3.ExtendingYourPitoConnectMoreThingsWe’renowgoingtolookatwaystoexpandthenumberofthingswecanconnecttoourRaspberryPi,overcomingthelimitationofhavingjustthe8digitalpinsavailable.We’regoingtodothisbybuildingourownexpansionboardtogiveuswhatcouldintheorybeanunlimitednumberofdigitalinputsandoutputs.

We’realsogoingtoovercomethelimitationsofthe+3.3Vpoweravailabletousbybuildingourown+3.3VpowersupplythattapsofftheRaspberryPi’s+5Vsupply.

Inthischapter,wewillcoverthefollowing:

LookingattheI2CbusindetailLearningaboutserial-to-parallelandparallel-to-serialconversionsBuildinga+3.3VpowersupplyBuildinganI2C-basedportexpandertogiveusmoreinputsandoutputsLookingatalternativeready-madeexpansionboards

PrerequisitesAlongwithyourRaspberryPi,you’llneedthefollowingpartsfortheprojectsinthischapter:

Acopperstripboard(orVeroboard®)AnLD1117V33voltageregulatorA2x100nF,16VceramiccapacitorA10uF,16VelectrolyticcapacitorA1xMCP2301716-bitportexpanderICA4x10K-ohmresistorAhook-upwire

TheI2CbusInthepreviouschapter,webrieflytouchedontheI2Cbus(orInter-IntegratedCircuitbus),whichisawaytoconnectmultipledevicestogetherusingjusttwowires.I2Cwasinventedintheearly1980sbyPhilipsasawaytolinkcomputerperipheralstogetherusingacommonprotocol.YoucanthinkofI2CasakindofearlyformofUSB.

I2Ctypicallyoperatesatrelativelylowspeedsofupto100kbit/s,comparedtomuchfasterinterfacessuchasEthernet,whichtypicallyoperatesatupto1Gbit/s,orUSB,whichcanoperateatupto480Mbit/s.However,thisisfastenoughtoconnectbasicsensors,displaydevices,orotherperipheralssuchasreal-timeclocks—infact;therearefasterversionsoftheprotocolthatsomedeviceswillsupport.

Just2wiresI2Cisabi-directionalserialcommunicationprotocolthatoperatesovertwowires:

TheSerialDataLine(SDA)wiretransmitsthedatatoandfromthemasterdevice.ReferringbacktotheGPIOreferenceinChapter2,ConnectingThingstoYourPiwithGPIO,thisispin3oftheGPIOconnector.TheSerialClockLine(SCL)wirehandlesalltimingandflowcontrolforthedataonthebus.Thisispin5oftheGPIOconnector.

You’llrememberthatwespokeaboutpull-upresistors,inthepreviouschapter,whichensurethattheGPIOdigitalinputsarepulledtoaknownstate.Well,thisisrequiredforthetwolinesontheI2Cbus,andbydefaultthelinesshouldbepulledhighwithresistors.However,ontheRaspberryPi,thishasalreadybeendoneforus,sowedon’tneedtoworryaboutitinourcase.

What’syouraddress?So,ifwecanusejusttwowirestocommunicatewithmultipledevices,howdoesourRaspberryPiknowwhichdevicetotalkto?ThisiswheretheI2Cprotocolcomesintoitsown.EachdeviceconnectedtothebushasitsownuniqueID,oraddress,madeupof7-bitsor10-bits.Somedeviceswillallowyoutosettheaddresstoensurethatit’suniquewithinyoursystem,butotherdeviceshavetheiraddresseshardcodedbythemanufacturer.

Thetwoaddressingmethods(7-and10-bit)areinteroperableandyoucanhavedevicesonthesamebusthatuseeithermethod,sincetheRaspberryPiitselfsupportsbothmethods.So,witha10-bitaddressingscheme,youcanseethatwecanconnectalotofthingstoourRaspberryPiusingtheI2Cbus,ascomparedtothelimitednumberofdigitalpinsontheGPIO!

ThereisaparalleluniverseDataisnormallytransmittedinserialmodeorparallelmode,dependingonthingssuchastherequireddataspeed,cabledistance,andfunctionality.Mostdatacommunicationbetweensystemsistransmittedinserialmodeoveracoupleofwires,suchastheI2Cbusmentionedearlier,butthisalsoincludesthingssuchastheEthernet,RS232/422,andUSB.

Withinacomputersystem,dataistransmittedinparallelmodeusingbuseswhosewidthmatchesthewordsizeofthedigitalsystemcommunicatingbetweenchips.Inparallelmode,allbitsofthedatawordaretransmittedsimultaneouslyovertheirrespectivedatalineswithinthebus,ratherthanassequentialbitsalongasingleline.

ThedigitalI/Opinswe’vebeentalkingabout(includingtheonesontheRaspberryPi’sGPIOconnector)areusuallygroupedtogetherasaparallelbus.Onoursystem,we’llbeusingparallelbuses(groupsofdigitalI/Opins)thatare8-bitswide.Thatis,thebushas8wiresthatcanbesetorreadusing8-bitbinaryvalues(ourwordsize).

Arepresentationofan8-bitdatabus

So,intheprecedingdiagramwehavethe8digitalI/Owiresonourbus.Ifwewantedtomakethebits(orwires)0,1,and4highoron,withtherestloworoff,thenwe’daddressthebusandsetittothefollowingvalues:

Inbinary,thiswouldbe00010011Inhex,thiswouldbe0x13Indecimal,thiswouldbe19(representedby16+2+1)

So,inotherwords,toswitchondatalines0,1,and4,wesendthebytevalue,19,tothebus’saddress.

Serial-to-parallelconversion

So,nowthatweknowwhatnumberstosendtoourbustoswitchonorswitchoffcertaindigitaloutputs,orreadcertaindigitalinputs,howdowedothisusingourI2Cbus,whichisaserialinterface?

Fortunately,therearemanyintegratedcircuits(ICs)availablethatallowustodothissimplyandeasily.TheseICsarecalledshiftregistersandperformserial-to-parallelconversions,takingthedatafromtheserialI2Cbusandconvertingtheincomingbitstoaparallelrepresentationbysettingeachoftheparallelbusoutputs.

Whenreadingtheparallelbusdatalinesasinputs,thereversehappens,convertingthebitsintoaserialformontheI2Cbus;thisisknownasparallel-to-serialconversion.

Thisisquiteasimplisticoverviewandtherearemanyresourcesavailablethatexplaintheseoperations;we’llseethisinactionlaterinthechapter,butfirst…

GivemepowerYou’llrememberfromthepreviouschapterthatmostthingstodowiththeGPIOoperateona+3.3Vlevel,ratherthanthe+5Vlevelthatisoftenassociatedwithdigitalcircuits.ThisisthesamewithourI2C-basedshiftregisters—theyneedtooperateon+3.3Vlevelsaswell,inordertoworkwiththeRaspberryPi.

You’llalsorecall,however,thatthere’snotmuch+3.3VjuiceavailabledirectlyfromtheRaspberryPi—infact,just50mA.Thisisreallynotenoughforourinterface.So,beforewegoanyfurther,we’regoingtobuildourown+3.3Vpowersupply,whichissufficientforoursystem.

Forourpowersupply,we’regoingtouseabasic3.3Vvoltageregulator(typeLD1117V33)thatwilltakeourslightlymoreplentiful+5VsupplyfromtheRaspberryPiandregulateittoanicesmooth+3.3Vsupply.Weshouldbeabletodrawafewhundredmilliampsfromthissupply—enoughfortheI/Ocircuitryonoursecuritysystem.

Thepartsrequiredforourpowersupplyareasfollows:

ALD1117V33voltageregulatorA100nF,16VceramiccapacitorA10uF,16Velectrolyticcapacitor

Here’sthecircuitdiagramforour+3.3Vpowersupply:

Aswithallourcomponents,theLD1117V33regulatoriswidelyavailablefrommanyelectroniccomponentsuppliers.

Ourpowersupplycanbeeasilybuiltonasmallpieceofstripboardlikethis:

NoteThestripboardisshownfromthetopintheprecedinglayout.Thatis,thecoppertracksareontheundersideoftheboardandthecomponentsareinsertedfromtheplaintop-sideandsolderedtothestripsunderneath.Inthislayout,it’snotnecessarytocutanyofthetracksonthestripboard.

BuildinganI2CexpanderRight,nowthatwe’veworkedoutwhatweneedtodotogiveusmoredigitalI/Opins,andbuiltourpowersupplyforit,wecanbuildourexpansionport.

Todothis,we’regoingtouseachipdesignedexactlyforthejob:theMCP23017,manufacturedbyMicrochipandwidelyavailablefromelectronicsuppliers.

TheMCP23017isanintegratedcircuitthatconnectsdirectlytotheI2Cbus(theSDAandSCLpinswetalkedaboutearlier)andgivesus16bi-directionalinputandoutputpins.Ifrequired,wecanconnectupto8ofthesechipstothesamebus,givingusupto128inputsandoutputs(yes,IknowthatIsaid“virtuallyunlimited”previously,butI’llexplainlater).

AnMCP23017integratedcircuitpinout

NoteThefulldatasheetfortheMCP23017isavailableonMicrochip’ssite,whichcanbefoundatwww.microchip.com/MCP23017.

TheI2CportexpandercircuitThebasicpartsyouwillneedtobuildyourportexpanderareasfollows:

A1xMCP2301716-bitportexpanderICA4x10K-ohmresistorA1x100nF,16VceramiccapacitorAcopperstripboard(orVeroboard®)Ahook-upwire

Here’sthecircuitdiagramforourI2Cportexpandercircuit.Itlookscomplicated,butactuallymostofthelinesareforconnectionstotheoutsideworld:

Let’swalkthroughthecircuitOntheright-handside,theconnector,CN1,isourRaspberryPiGPIOconnector—notethatwe’reonlyusingfourofthepins:

The+5VOutput(Pin2)TheI2CSDA(Pin3)TheI2CSCL(Pin5)The0V/GND(Pin6)

You’llseemyfriend,the+3.3Vregulator(U1,C1,andC2),discussedearlier.Thistakesthe+5VoutputfromtheRaspberryPiandgivesusour+3.3Vforusebytherestofthecircuit.

ThemaincomponentisU2—ourMCP23017portexpanderchip.Pins9and10onthe

chipareconnectedtothe+3.3VsupplyandtheGND,respectively,andC3isusedasadiscouplingcapacitorclosetothechiptoreduceanynoiseonthepowersupply.

TheMCP23017canbeusedasa16-bitexpander,oras2x8-bitexpanders.Inourcircuit,wehavesplitthedevicetogiveus2x8-bitbusses:I/OBusAandI/OBusB.Eachpinonthebussescanbeprogrammedtoworkasaninputoroutput.

TipConnectingthingstotheinput/outputpins

Theinputandoutputpinsonourbussescan’tusuallybeconnectedtothingsdirectly—theyprovidelimitedcurrentandneedtobeinterfacedcorrectlytothingssuchasbuzzersandlights;theymustalsobeprotectedagainstdamaginginputsignals.Inthenextchapter,we’lllearnhowtoconnectsafelytoourI/Oports.

TheI2CSDA/SCLlinesfromtheRaspberryPiareconnectedtopins12and13ofthechip.You’llseethattherearealsoadditionalI2Coutputs(PL1toPL3)toillustratethatwecanconnectotherdevicestotheI2Cbus,suchasanotherMCP23017chiptogiveusafurther16digitalI/Os.

ResistorR1isusedtoholdtheRESETpin(18)high.Bybringingthispinlow,youcanresetthechip.

ResistorsR2toR4areusedtoholdtheaddresspinsA0toA2(pins15-17)low.

Highsandlows

Whenweusethetermshighandlowinrespecttodigitalpinsorinputs,wearesimplydescribingwhetherthelogiclevelofthepinisatabinary1or0,respectively.Digitalpinsdon’tliketobeleftfloating—wherebytheyareneitherhighnorlow—asthiscancauseunpredictableoperations.Therefore,wealwaysmakesuretheyareheldatadeterminedlogiclevel.Ingeneral,connectingthepinto0V(orground)ensuresthatit’sheldatlogiclevel0,andconnectingtothepositivesupply(e.g.3.3V)ensuresthatit’sheldatlogiclevel1.

RememberImentionedearlierthatyoucanconnectalargenumberofdevicestotheI2CbusinordertogiveusavirtuallyunlimitednumberofI/Opins?Well,actuallyinmanycases,thisisnotstrictlytrue.ThisisbecauseoftheaddressingschemeforI2Cdevices,whichmakesalldevicesidentifiablewhentheyareallconnectedtothesametwowires(theiruniqueaddress).Theaddressofeachdeviceisagreeduponinadvancebymanufacturerstomakesurethateveryone’sdeviceswillworktogetheronthesamebuswithoutcreatingconflicts.Assuch,theaddressispre-programmedintothedevice.

TheMCP23017hasbeengivenitsuniquebaseaddress,butcanbemodifiedbychangingtheaddresspinsA0-A2highorlow;thus,ineffect,itcanbeconfiguredtobeoneof8addresses.Thisiswhyyoucanonlyhaveamaximumof8ofthesechipsonthesameI2Cbus,givingusatheoreticalmaximumof128I/Opins(thatis,16I/Osx8chips).

BuildingyourexpansionboardThiscircuitcaneasilybebuiltonasmallpieceofstripboard.Thefollowingimageshowsanexampleofthelayout,whichlooksabitsimplerthanthecircuitdiagram.Inthenextchapter,we’lllearnhowtoconnectupourboardandprogramitsowecancheckthatitworks.

TipWhenusingstripboard,makesurethatyoucutthetracksbetweenthetworowsofpinsontheMCP23017sothattheyaren’tshortedtogether.Youcanbuytrackcutters,whichmakethistaskeasy,frommanyelectronicsuppliers.Again,ontheprecedinglayout,thecopperstripsareunderneaththeboardwiththecomponentsontheplainside.

Youmightwanttoaddthe+3.3Vpowersupplycircuittothesamepieceofstripboardtoo,tokeepeverythingcontainedtogether.

NoteInthenextchapter,wewilllearnhowtoprogramthedevicesothatwecanuseitinourhomesecuritysystem.

Usingready-madeexpansionboardsWhileit’smuchmoresatisfyingtobuildyourownstuff,youmightwanttolookatbuyingsomereadilyavailableexpansionboardsforyourhomesecuritysystemifyou’renotyetconfidentwithyoursolderingiron,orifyoujustsimplydon’thavethetime.

Followingaresomeready-madeexpansionboardsthatyoucanobtain;theyshouldworkaspartofourhomesecuritysystemwithabitofmodificationtoourscriptstosupportthelibrariesthatarerequiredbythehardware.

HobbytronicsMCP23017expanderportkitThiskitisalmostidenticaltoourowncircuitintheprevioussectionofthischapter.ThekitcomeswithanMCP23017,aPCB,andvariousconnectors.Theboardsaredesignedtobedaisy-chainedtogethersothatyoucanhavemultipleexpanderstogiveyoumoreinput/outputports.Notethatthiskitisnotpre-builtandrequiressoldering,butIthoughtI’dincludeitbecauseit’stheboardthatIusetobuildsuchsystemswhenprototyping.YoucangetitdirectlyfromHobbytronicsathttp://bit.ly/mcp23017.

PiFaceDigitalI/OexpansionboardThePiFaceDigitalI/Oexpansionboardisapre-builtversionofourboard,butitusestheMSP23S17chipvariantthatoperatesovertheSPIbusinsteadoftheI2Cbus.Theboardisdesignedwith8inputsand8outputs,aswellasseveraladditionalpiecesofhardwareincludingacoupleofrelays,someLEDs,andsomeswitches.Notethatthecodeinthisbookforoursystemwillneedtobemodifiedtoworkwiththisboard,sinceitusesadifferentinterfaceanddifferentlibraries.It’savailablefromFarnellelement14athttp://bit.ly/2434230.

ThePiFaceDigitalI/OExpansionBoard

GertboardTheGertboardisaRaspberryPiadd-onboarddesignedbyGertvanLoo—oneofthehardwareengineersinvolvedintheoriginaldesignoftheRaspberryPi.

It’saverycapableandreasonably-pricedboardthatcomesfullyassembledandfeatures12bufferedinput/outputlines,opencollectordriversforswitchingondevicesthatneedafairbitofcurrent(suchassoundersandlights),plusadigital-to-analogconverter.

YoucanonlyconnectoneoftheseboardstoyourRaspberryPi,soifyouneedmoreI/Olinesyou’llneedtousesomethingelseaswell.Butit’sagreatboardtoexperimentwith.Interestingly,itfeaturesanATmegamicrocontroller,whichisthesameastheonethattheArduinouses,andyoucan,infact,usetheArduinodevelopmentenvironmentforthedevice.

Onceagain,thecodeinthisbookforoursystemwillneedtobemodifiedtoworkwiththisboard.

TheGertboardisavailablefromFarnellelement14athttp://bit.ly/2250034.

AssembledGertboard

SummaryWe’venowlookedattheI2Cbusindetail,andlearnedhowtobuildanexpansionportusingthisinterfacesothatwecanconnectmanymorethingstoourRaspberryPi,ratherthanbeingrestrictedtojustthe8digitalI/OpinsofferedbytheRaspberryPi’sGPIOport.Inadditiontothat,weexploredotherready-madeboardsthatcanbeusedtoconnectlotsofthingstoourRaspberryPi.Wehavealsobuiltapowersupplythatwillgiveusmore+3.3VpowerthanwecanobtainfromtheRaspberryPidirectly.

Inthenextchapter,we’llstarttoactuallyconnectthingstoourhomesecuritysystem,suchasmagneticsensorsandothertypesofcontactdevices,andlearnhowtoprogramourI2CexpansionportusingBashscriptssothatwecanreadthestateofoursensorsandswitchonwarningLEDs.We’llalsostartdevelopingthecontrolscriptsforoursystem,whichwillallowustoarmanddisarmthesystemandadddelaytimers.

Chapter4.AddingaMagneticContactSensorNowthatwehavebuiltourportexpanderhardware,weneedtolearnhowtoprogramitsothatourRaspberryPicandetectthethingsthatweconnecttoitaspartofourhomesecuritysystem.Wewillbeginbyconnectingswitchestooursystemintheformofmagneticsensors—themostcommoncomponentusedinhomesecuritysystemstodetectintrusionsthroughdoorsandwindows.

Inthischapterwewillcoverthefollowingtopics:

LearningaboutreedswitchesandhowtheyworkasdoorsensorsEnablingandsettinguptheI2CbusontheRaspberryPiConnectingoursensortoaninputonourportexpanderLearninghowtoaccessourI2CportexpanderfromaBashscriptWritingascriptthatwilldetectthestateofourdoorsensorLookingatothertypesofcontactsensorsthatcanbeconnectedandprogrammedinthesameway

PrerequisitesYou’llneedthefollowingpartsfortheexercisesinthischapter:

OurRaspberryPiandPortExpanderboard8x10KohmresistorsAmagneticdoorsensorandmagnetAhook-upwireA4-corealarmwire

TheworkingofmagneticcontactsensorsAreedswitchisessentiallywhatmakesupourmagneticcontactsensor.Areedswitchcomprisestwometalcontactsmadeofmagneticmaterial(calledreeds)placedinsideaglassenvelope.Whenthecontactstouch,theswitchison,andwhentheyspringapart,theswitchisoffandthecircuitisbroken.Thewaytocontrolthesecontactsisbymeansofamagneticfieldthatmakesorbreaksthecircuitwhenitisneartotheswitch.

Anormallyopen(NO)typeofreedswitchisnormallyswitchedoffuntilamagnetcomesclosetotheswitch,whichthenpullsthecontactstogether.

Anormallyclosed(NC)varietyworkstheotherwaywiththeswitchbeingnormallyonuntilthemagnetcomesclosetotheswitch,pullingthetwocontactsapart.

Atypicaltypeofreedswitch

Youcannowseehowamagneticreedswitchcanbeausefulsensorinsecurityapplications,andinparticularforourhomesecuritysystem,todetectwhendoorsandwindowsareopenedandclosed.Wesimplyputareedswitchonthedoorframeandconnectittooursecuritysystem,withthemagnetplacedoppositetheswitchontheactualdoor.Whenthedooropensandcloses,itmakesorbreaksthecontactsinourreedswitch.

Reedswitchesandtheirmagnets,whicharedesignedforsecuritysystems,usuallycomeenclosedinlittleplastichousings,makingthemeasytoscrewontothedoorandframe.

Adoor-frame-mountedmagneticsensorcontainingareedswitch(Type:CherryMP201801)

Themagneticsensorismountedonthedoorframe(obviously,soitcanconnecttothealarmcircuitwires),whiletherespectivemagnetwillbeattachedtothedoor,closeenoughtotheedgesuchthatthesensorcontactsconnect(orbreak,dependingonthetype)whenthemagnetisdirectlyoppositeit.

Arespectivedoor-mountedmagneticactuator(Type:CherryAS201801)

SettinguptheI2CportexpanderNowthatwehavebuiltourportexpander,weneedtogetitreadytoconnectoursensorsto.First,weneedtoinstallthetoolsontheRaspberryPitoallowustousetheI2Cbusandprogramdevicesconnectedtoit,includingtheMCP23017chipthatmakesupourportexpander.

NoteDon’tconnectyourportexpandertotheRaspberryPiuntilafteryou’vesetuptheI2Cbusonyoursystem.

EnablingtheI2CBusIt’shighlylikelythatthemoduleforusingtheI2Cbushasn’tbeenloadedbydefault.Fortunately,doingthisisfairlystraightforwardandcanbedoneusingtheRaspberryPiconfigurationtool.Performthefollowingsteps:

1. LaunchtheRaspberryPiconfigurationtoolwiththefollowingcommand:

$sudoraspi-config

2. Selectoption8:AdvancedOptions.

3. SelectOptionA7:I2C.

4. Select<Yes>.5. RebootyourRaspberryPiforthesettingtotakeeffect.

NowthattheI2Cbushasbeenenabled,weneedtosetuptheoperatingsystemsothattherequiredmodulesareloadedeachtimethesystemboots.Todothis,performthefollowingsteps:

1. EdittheModulesfileusingthefollowingline:

$sudonano/etc/modules

2. Addthefollowinglinestothefile:

i2c-bcm2708

i2c-dev

3. SavethefileandexitNano.

InstallingtheI2CtoolspackageSothatwecaneasilyaccesstheI2CbususingBashscripts,weneedtoinstallthei2c-toolspackage:

$sudoapt-getinstalli2c-tools

Onceinstalled,weshouldshutdownoursystem:

sudoshutdown–hnow

Afteractivityhasstopped,switchoffyourRaspberryPi,connectyourportexpandertotheGPIOport,andpoweritbackupsothatwecanstartusingit.

Asaquicksanitycheck,youcanseeifI2Csupporthasbeenloadedbytyping:

$ls/dev/i2c-*

Thisshouldgiveyoualistofatleastonebus—forexample,/dev/i2c-1—ifthemoduleisloaded.Ifit’snot,you’llprobablygetthefollowingresponse:

ls:cannotaccess/dev/i2c-*:Nosuchfileordirectory

Inthiscase,you’llneedtocheckbackthroughthepreviousstepsassomethinghasn’thappenedproperly.

FindingourdevicesThei2c-toolspackageinstallsseveraldifferenttoolstohelpususeourportexpanderattachedtothebus.Thei2cdetecttoolallowsustofindI2Cbusesanddevicesattachedtothebusses.

TogetalistofI2Cbussesonoursystem,typethefollowing:

$sudoi2cdetect-l

Youshouldgetthefollowingresponse:

pi@raspberrypi~$sudoi2cdetect-l

i2c-1i2c20804000.i2cI2Cadapter

TheprecedingoutputshowsthatwehaveoneI2Cbus,andthiswillbetheoneconnectedtoourGPIO.NotethatearliermodelsoftheRaspberryPimayreturnthedeviceIDasbeingi2c-0.

Wecannowusethetooltoscanforallofthedevicesattachedtoourbus.WedothisbyspecifyingthebusID,asinthefollowingcommand:

$sudoi2cdetect1

WithnothingattachedtotheI2Cbus(thatis,withoutourportexpanderattached)we’dexpecttoseethefollowingoutput:

pi@raspberrypi~$sudoi2cdetect1

WARNING!ThisprogramcanconfuseyourI2Cbus,causedatalossandworse!

Iwillprobefile/dev/i2c-1.

Iwillprobeaddressrange0x03-0x77.

Continue?[Y/n]Y

0123456789abcdef

00:—--—--—--—--—--—----

10:—--—--—--—--—--—--—--—--

20:—--—--—--—--—--—--—--—--

30:—--—--—--—--—--—--—--—--

40:—--—--—--—--—--—--—--—--

50:—--—--—--—--—--—--—--—--

60:—--—--—--—--—--—--—--—--

70:—--—--—--—--

pi@raspberrypi~$

NothingfoundontheI2Cbus

Withourportexpanderattached,weshouldseethefollowingoutput:

pi@raspberrypi~$i2cdetect1

WARNING!ThisprogramcanconfuseyourI2Cbus,causedatalossandworse!

Iwillprobefile/dev/i2c-1.

Iwillprobeaddressrange0x03-0x77.

Continue?[Y/n]Y

0123456789abcdef

00:—--—--—--—--—--—----

10:—--—--—--—--—--—--—--—--

20:20—--—--—--—--—--—--—----

30:—--—--—--—--—--—--—--—--

40:—--—--—--—--—--—--—--—--

50:—--—--—--—--—--—--—--—--

60:—--—--—--—--—--—--—--—--

70:—--—--—--—--

pi@raspberrypi~$

OurI2Cportexpanderslavedevicecanbefoundattheaddress,0x20(32decimal).

NoteTheprecedingaddressisthelocationofourMCP23017chipconnectedtotheI2Cbus.Ifyoudon’tseethis,thenthere’sprobablyawiringissueandyou’llneedtogobackandcheck.

You’llrecallthatwecanaddupto8ofthesedevicestotheI2CbusbysettingtheA0-A2pinstoauniqueaddress.IfA0issettohigh,thentheaddressofthedevicewillbeshownas0x21(33decimal)—andupto0x27(39decimal),ifallpinsarehigh.

SettinguptheportexpanderAsdiscussedinthepreviouschapter,wecanhave2x8-bitbussesonourportexpander,witheachpinbeingdefinedasaninputoroutput.Ontheexpanderboardwebuilt,wecalledthemI/OBUSAandI/OBUSB.

ToconfiguretheMCP23017chipontheI2Cbus,wecansendittheappropriatecommandsusingthei2csettoolweinstalledearlier.

Onourhomesecuritysystem,wearegoingtoassignallofthepinsonBUSAasinputsforconnectingoursensorstoit.Todothis,weusethefollowingcommand:

$sudoi2cset–y10x200x000xFF

NoteWhatdoesthiscommandmean?

-y:Thisrunsthecommandwithoutuserinteraction.1:ThisistheIDofthebus(forexample,i2c-1).0x20:Thisistheaddressofthechip.0x00:Thisisthedataregisteronthechip(inthiscase,thePORTApinassignment).0xFF:ThisistheValueloadedintothedataregister(inthiscase,allpinsasinputs—binary%11111111).

Youcancheckthatthedataregisterhasbeensetcorrectlybyreadingitusingthefollowing:

$sudoi2cget–y10x200x00

Thisshouldreturnavalueof0xFF,whichisthevaluewesetearlier.

ConnectingourmagneticcontactsensorNowthatwe’vegotourportexpanderworkingwiththeRaspberryPi,wecanstartconnectingthingstoitandcreatethescriptsthatwillmonitorthesensorsontheinputpins.

Let’sgobacktoourportexpanderstripboardthatwasbuiltinthepreviouschapterandconnectourmagneticsensor.Butfirst,weneedtoensurethatallofourinputsarepulledlowbydefaultusing10Kohmresistors.Thispreventsthemfrombeinginafloatingstateandgivingusspuriousdatawhenwereadtheport’sdata.

NoteInthefollowingdiagram,I’veconnectedthepull-downresistorsexternally,butyoumaywanttoincludethemdirectlyonthestripboard.Towardtheendofthisbook,we’llhaveanewboardlayoutthatbringseverythingthatwe’vebeenprototypingsofartogetherinasinglesolution.

Tochecktheport’sinputvalue,weusethei2cgetcommand:

$sudoi2cget–y10x200x12

Thisshouldreturn0x00,whichmeansallinputsareoff(binary%00000000).

NoteWhatdoesthiscommandmean?

-y:Thisrunsthecommandwithoutuserinteraction.1:ThisistheIDofthebus(forexamplei2c-1).0x20:Thisistheaddressofthechip.0x12:Thisisthedataregisteronthechip(inthiscase,thePORTAreadvalue).

Nowlet’sconnectonesideofourmagneticsensor’sreedswitchtodatapin0ofBUSA(whichwe’llcallGPA0forreference),andtheothersidetoour+3.3Vline.Bydefault,theswitchisnormallyopen(NO),whichmeansthattheinputisstillpulledlowbytheresistor.

Butwhenyoumovetheaccompanyingmagnetneartothesensorswitch(forexample,ifthedoorisclosed),theswitchwillclose,pullingtheinputhightothe+3.3Vline.Ifyoureadtheport’sinputvaluenow,byrunningthesamecommand,youshouldseethatitreturns0x01,indicatingthatthefirstbitishigh(binary%00000001).

MonitoringthesensorNowthatwehaveeverythinginplaceandourmagneticsensorisdetectingwhetherthedoorisclosed,wecanmonitorthissensorwithasimpleBashscriptthatusestheI2Ctoolcommandsthatweinstalledearlier.

Thecodelistingforpoll-magnetic-switch.shisasfollows:

#!/bin/bash

sudoi2cset–y10x200x000xFF

#loopforever

whiletrue

#readthesensorstate

SWITCH=$(sudoi2cget–y10x200x12)

if[$SWITCH=="0x01"]

#contactclosedsowaitforasecond

echo"Thedoorisclosed!"

sleep1

#contactwasopened

echo"Thedoorisopen!"

Whenyourunthescriptandthenpushthebutton,youshouldsee“Thedoorisopen!”scrollinguptheconsolescreenuntilyoustoppressingit.

Bycombiningthiswithourelaboratelightswitchprojectinchapter2,wecanswitchontheLEDconnectedtoGPIO17whenthedoorisopened:

#!/bin/bash

#setuptheLEDGPIOpin

#setupportexpander

#loopforever

whiletrue

#readthesensorstate

if[$SWITCH=="0x01"]

#switchnotpushedsoturnoffLEDpin

#switchwaspushedsoturnonLEDpin

#shortdelay

sleep0.5

NoteLater,asweaddmoresensorstodifferentinputpins,wewillneedtobeabletodetectwhichonehasbeentriggered.We’lllookatwritingaBashfunctionlaterinthebook,whichwillparsethereturnedhexvaluefromthei2cgetcommand,andtellusexactlywhichofthe8inputsishigh.

Anti-tampercircuitsIfyoutakeacloserlookatoursystem,youmightrealizethatdependingonwhetheryouaredetectingnormallyopenornormallyclosedsensorswitches,itispossibletotamperwiththesensorchannelbysimplycuttingthewire.So,inthecaseofanormallyopenswitch,itwouldn’tactivatethemonitoringsystemifthewireswerecut,asitwouldalwaysappeartobeopen,eveniftheswitchwasclosed.

Tomitigatethis,mostalarmsystemsfeaturea4-corewiringsystemtoconnectthesensordevicestothemaincontrolboard—twocoresareusedtoconnectthesensorandtwoareusedtocreateananti-tamperloop,whichthenitselfformsasensorinputformonitoring.

4-corealarmcable

TakealookatthefollowingcircuitsothatyouseewhatImean:

Inthiscircuit,wehavetwosensors:oneformonitoringawindowandoneformonitoringadoor.TheseareconnectedtotheI/OBUSAinputs,0and1(orGPA0andGPA1,asweliketocallthem).Asbefore,theyarepulleddownto0Vbyresistorsbut,whenswitchesareclosed,thepositivevoltagerailtakestheinputshigh.

However,we’vealsoaddedananti-tamperloopthroughoutthewholesystem,whichisconnectedtoGPA7formonitoring.Theloopisdaisy-chainedthrougheachofthecablesconnectingthesensorstothecontrollerboard.Allthetimetheloopisintact,theinputGPA7iskepthigh,butifthecableiscutanywhere,thecurrentwillstopflowingthroughitandtheresistor,R3,willpulltheinputlow.Thiswillthenbedetectedbythemonitoringscript.

Manysecuritysensorproductsprovideafacilitytoterminateanti-tamperloopwireswithinthem.

So,inourhomesecuritysystem,we’regoingtoassignGPA7asouranti-tamperloop.

GettingintothezoneItmayhaveoccurredtoyoubynowthatevenamodest-sizedpropertycouldrequireplentyofdoorandwindowsensors;thus,ifweusedoneinputforeachsensor,we’dsoonrunoutunlessweputmoreandmoreportexpandersontothesystem.Thesameistrueforcommerciallyavailablesecuritysystems.

So,thewaythisisdealtwithisbycreatingzones,witheachzonecontainingagroupofsensors.Abedroom,forexample,maybedefinedasonezonewithawindowsensor,adoorsensor,andmovementdetectorformingthatzone.Inthisscenario,eachsensorisconnectedtothenextinaseries(ordaisy-chained);ifoneofthemtriggers,itwillalertthemonitoringsystemthattherewasatriggerinthezone.Obviously,though,itmaynotnecessarilybetheactualdetector,whichinmostapplicationsisn’treallyanissue.

However,thiscanintroducesomechallengeswhenwe’reconsideringmixingnormallyopenandnormallyclosedtypesensorswithinazone,butthisissomethingwewillexplorelateroninthisbook.

Theothersensorsyoucanusearelistedasfollows:

HallEffectSensor:Hall-effectsensorsaresimpleelectronicchipsthatareusedtodetectmagneticfieldsplacednearthem.Theyarenotdissimilartothereedswitchwe’vebeenusing;however,becausetheyareelectronicdevices,theyareabletomeasurethedegreeofproximityinrelationtothemagnet(orthestrengthofmagnetism),ratherthanbeingjustonoroff,asisthecasewiththereedswitch.Also,becausetheyaresolid-state,theycouldbeseenasbeingmorereliablethanmechanicalswitches.

Alow-costhalleffectsensor—AllegroMicrosystemsA1302KUA-T

PressureMatSensors:Pressurematsareusedtodetectapersonstandingorwalkingonthem,andcanbeplacedunderafloormattohidethemfromsight.Theycanevenbeusedinachairtodetectpeoplesittingonit.Essentially,theyareswitches,justlikethereedswitch,exceptthattheyareactivatedbythepressureofwalkingonthem,andso,canbewiredandusedinexactlythesamewayasforourmagneticsensorcircuits.

Apressureswitchcanbeusedunderafront-doormat

SummaryInthischapter,wegotourI2C-basedportexpanderconfiguredandworking,andweexperimentedwithitbyconnectingamagneticsensor—oneofthemostcommonlyusedsensorsinsecuritysystems.We’vealsolearnedhowtointeractwithI2CdevicesusingBashscripts,andhowtoreadandwritedatatoandfromthesedevices.

Inaddition,weshouldnowbebeginningtounderstandthevariouselementsandbuildingblocksofasecuritysystem,includinganti-tamperloopsandzones.Theseareconceptsthatwillprepareusforlateroninthebook,whenwestarttopieceallofthistogetherandbuildourfinal,all-encompassingsystem.

Inthenextchapter,wewilllookatpassiveinfra-redmotiondetectors,howtheywork,andhowwecanconnectthewiredandwirelesstypestoourhomesecuritysystem.We’llalsolearnhowtocreatelogfilesbasedoneventsusingBashscriptssothatwecanmaintainahistoryofdetectorstatesastheychange.

Chapter5.AddingaPassiveInfraredMotionSensorInthepreviouschapter,westartedaddingbasicbutcommonlyusedmagneticswitchsensorstoourhomesecuritysystemandreadingtheirstatustoprotectdoorsandwindowsfromintrusion.Wealsolookedathowwecandivideourhomeintozones,suchasbyindividualrooms,sothatwecangroupoursensorsintologicalcircuits,whichcanthenbeidentifiedaspartofthesezonesratherthanasindividualsensorinputs.

WewillnowaddmotionsensorstooursystemintheformofPassiveInfra-Red(PIR)detectors.Thesedetectorscomeinavarietyoftypes,andyoumayhaveseenthemlurkinginthecornersofrooms.Fundamentally,theyallworkinthesameway,whichisdetectingthepresenceofbodyheatwithinacertainrange;so,theyarecommonlyusedtotriggeralarmsystemswhensomebody(orsomething,suchasapetcat)entersaroom.

AtypicalPIRmotionsensor(typeGardScanQX-PIR)

Inthischapter,wewill:

LearnhowPIRdetectorsworkandhowtheyaresetupConnectawiredPIRdetectortoaninputonourportexpanderStartusinga12Vpowersupplyinsteadof3.3VinourzonecircuitsLearnhowtointerface12VcircuitssafelywithourGPIOportsLearnhowtoconnecta433MHzwirelessreceivertoourRaspberryPiConnectaremote-controlledswitchtooursystemusing433MHzradiosignalsWriteascriptthatwilldetectandlogthestateofourdetectorinputswhenitchanges

PrerequisitesYou’llneedthefollowingpartsforthischapter(apartfromthecomponentsusedinthepreviouschapter):

Apassiveinfrareddetector,thewiredtype(thisisavailablefromanyDIYstore)A4N25/4N35opto-isolatorA1N4148diodeA1-KohmresistorA10-KohmresistorA433MHzreceivermoduleandremotetransmitter(thisisoptional)A12VpowersupplyAhook-upwireA6corealarmwire

PassiveinfraredsensorsexplainedYoumightnotrealizeit,butallobjectsradiateheatenergy(includingyourcoffeetable);it’sjustthatyoucan’tseeitbecauseheatconsistsessentiallyofinfraredwaves,whichareinvisibletothehumaneye(exactlythesameasyourTVremotecontrol).Thesewavescan,however,bedetectedbyelectronicdevicesdesignedforsuchapurpose,suchastheinfraredreceiverinyourTVthatdetectstheenergyemittedbyyourremotecontrolwhenthebuttonsarepressed.

Youprobablydorealize,however,thatlivingthingssuchasus,ourcat,andthemouseunderthefloorboardsgeneratequiteabitofheat.Passiveinfraredmotionsensorsusedinsecuritysystemsandautomaticlightsaredesignedtodetectthislevelofheat.Thetermpassiveisusedbecausethesensorsthemselvesdonotradiateanyenergyfordetectionpurposes—instead,theyjustdetecttheinfraredradiationemittedbyobjects.Thisisnotablydifferentfromdevicessuchasultrasonicsensorsandradars,whichrelyondetectingreflectionsfromobjectsofthepulsesofenergythatthesensorssendout.

PIRsensorsneedtobealittlesmartbecausetheyeffectivelyhavetocopewithconstantlyvaryingtemperaturesintheroom.Theysettleonthebackgroundtemperatureoftheroomtheyarein,suchasthatofawallorfloorthattheypointto.Whenanobject,suchasoneofusorourcat,movesbetweenthedetectorunitandthebackgroundobject,thetemperatureinfrontofthesensorrisestothebodytemperaturequickly,andthisinturntriggersthesystem.

SettingupyourPIRsensorPIRsensordevicescomeinmanyformats,includingdifferentmaterialsinsensorchipsandthelensinfrontofthesensorviewwindowthatcanwidelyaffecttherange,fieldofview,andsensitivityofthedevice.Therefore,yourbestguidetosettingupasensorwillusuallybeinthatlittlebitofinstructionpaperthatcomeswithit.

However,regardlessofthetypeofPIRsensoryouhave,herearesomegeneralguidelineswhenconsideringwhereyoumountyoursensorinordertoavoidfalsetriggers:

EnsurethatthedeviceismountedonasolidfoundationandnotaffectedbyvibrationNevermountitinalocationwheredirectorreflectedsunlightcanbepickedupbythelensSimilarly,nevermountthedevicefacingoraboveheatsourcesDon’tmounttheunitindraughtylocationsasthiswillaffectitsbackgroundtemperaturecalibration

Thelocationoftheunitalsodependsontheareayouwanttoprotect.Youmaywanttodetectpeopleenteringyourlivingroomfromthehallway,soyourcoverageareacouldbedefinedasbeingfromthecorneroftheroomwherethedeviceismountedtothelivingroomdoor.

PIRsensorsusuallyofferafixedfieldofview(forexample90or110degrees)buthaveavaryingrange,dependingontheangleatwhichtheyarepointingdownandtheheightatwhichtheyarelocated.

Inmysystem,IwilluseaGardscanQXPIRDetectorformywiredunits,whichisaprettygood,low-costunitavailablefromRSComponents(theordercodeis493-1289).Thisunithasafieldviewof110degreesandarangeofupto12meters,dependingontheconfigurabledownanglethatit’smountedat.Thecoveragepatternsforthisparticularunit,astakenfromitsdatasheet,areshowninthefollowingfigure.Notethatfromthesepatternsnoteverypartoftheareainfrontofthedeviceiscovered,whichispossiblynotquitewhatyouexpect.Thisiswhypositioningtheunitsinaccordancewiththedevice’sdatasheetissoimportant.

GardScanQX-PIRcoveragepatternforits110degreefieldview(top/planview)

Hereisadiagramofthesideviewaswell:

GardScanQX-PIRcoveragepatterndependingontheangleconfiguredplusa“look-down”window(sideview)

Givemepower(again)Beforewecangoontoconnectoff-the-shelfsecuritydevicestoouralarmsystem,weneedtohaveapowersupplythat’scompatiblewithsuchdevices.Typically,alarmcircuitsandtheirdevicesusea12Vsupplywithenoughcurrenttodriveallthedevicesandthealarmcontrolsystemitself.

Fortunately,thisisnottoodifficulttosortout,butitissomethingweneedtodonow;otherwise,wewon’tbeabletoconnectandpowerourPIRsensors.Theeasiestwaytodothisistobuyahigh-quality12Vmainsadapterthatprovidesaniceregulatedsupply.Thesearereadilyavailablefromonlinestoresorelectronicssuppliers.Alternatively,youcanbuildyourown12VregulatedsupplyandaddittothepowersupplystripboardthatwebuiltinChapter3,ExtendingYourPitoConnectMoreThings.

NoteAnotheroptionistousebattery-poweredPIRsensors,whichmeansthatyouwouldn’thavetopowertheunitfromthesecuritysystem’spanelitself;however,itobviouslyalsomeansthatthebatterieswouldneedreplacingfromtimetotime.ThewirelessPIRwewilllookatlaterinthischapterisbattery-powered.

We’lltakealookathandlinghigher-voltagesensorcircuitslateroninthischaptersothatwedon’tblowupourhomesecuritycontrolcircuitsortheRaspberryPi.

ConnectingourPIRmotionsensorCommerciallyavailablealarmsystemsconnecttotheirdevicesusinga4coreor6corealarmcable.Inthepreviouschapter,weuseda4corecablebecausewewereconnectingaswitchthatneededtwowiresplusanantitamperloop,whichneededanothertwowires.

ForourPIRsensorcircuit,weneedthesamefourwires;however,wealsoneedtosendpowertothedevicefromthecontrolpanel,soanadditionaltwowiresareneededforthis—hencetherequirementfora6corecable.

ThefollowingdiagramshowsthewiringconnectionsformyGardScanPIRsensor,butthisisinfacttypicalformostoff-the-shelfsecuritysystemdevices:

Typicalconnectionsforsecuritysystemsensordevices

Similartothemagneticcontactsensorsthatwelookedatinthepreviouschapter,devicescancomewitheitheranormallyclosed(NC)oranormallyopen(NO)alarm.Thisparticulardevicehasanormallyclosedoutput,whichmeansthatthealarmcircuitwillbebrokenwhenthedetectoristriggered.Thisisthepreferredconfigurationforoursensordevicesasthismeansthattheycanbewiredinaserieswithineachofourzones.

Wecannowaddthissensordeviceintothealarmcircuitthatwestartedputtingtogetherinthepreviouschapter.Thefollowingdiagramshowsthecircuitforalloursensorssofarwiredintoasinglezone:

Aschematicforourzonewithallthreesensorsplustamperloopinthesamezone

Upuntilnow,weusedthe+3.3Vpowersupplytopassthroughthesensorswitchesandalarmcircuit.Infact,thisisnotagoodidea,andwe’vebeendoingthisonlyforconveniencetotestoutourGPIOinputs.

Inreality,andinourfinalsystem,wereallyshouldusea12Vsupplytopassthroughthesensorandantitampercircuits.Thisisbecauseahighervoltagetravelsbetterthroughthesystemandislesssusceptibletonoise,whichcouldpreventtriggeringorcausefalsetriggering.Thisalsomakesitcompatiblewithcommerciallyavailablesystemsandaccessories.

12ValarmzonecircuitsMakingourzonecircuitsuse12Vinsteadof3.3Visassimpleaschangingthepowersupply,andinfactallofsensorsweusedsofarcanhandle12Vpowerpassedthroughtheirswitches.

However,ifweweretopresentthe12VcircuittotheinputsonourGPIOportontheRaspberryPiorourportexpander,wewouldexpecttoseesomemagicsmokeandsmellsomethingburning.So,weneedtoaddsomecircuitrythatallowsustouse12Valarmcircuitsaswellasprotectourcontrolboardinputs.

AlarmcircuitprotectionAneffectivewaytoprotectourzoneinputsfrom12Valarminputsistousealittlelow-costdevicecalledanopto-isolator.Asthenamesuggests,thisisolatesthealarmcircuitfromthedigitalinputsofthecontrolboardusinglight.

Insideanopto-isolator(alsocalledanopto-coupler)isaninfraredLED,whichtransmitslighttoaphoto-transistorwhenacurrentispassedthroughit,thusswitchingiton.Thecircuitsareelectricallyisolatedastheyarecontrolledonlybylight.

The4N25(shownintheprecedingimage)and4N35arelow-cost,6-pinopto-couplerdevices,andmostmanufacturestendtousethepinlayoutshowninthefollowingdiagram:

Nowthatweknowhowwewillcoupleour12Valarmcircuitwiththeinputsonourcontrolpanel,let’sbuildtheentirecircuit,whichwe’lluseforeachofthezonesthatweaddtooursystem.

A12VzonecircuitopticallyisolatedfromtheGPIOinput

HowitworksAtthistime,we’reassumingthatourzonecircuitsarenormallyclosed—thatis,thealarmtriggerswhenthecircuitisbroken.

The12VsupplyispassedthroughtheLEDoftheopto-isolatorwiththecurrentbeinglimitedbythe1-Kohmresistor.The1N4148diode,inreverse,istheretoprotecttheopto-couplerfromreverse-polarityvoltages.

NoteThe1-Kohmresistoriscalculatedfromthefactthatwehavea12Vsupplyandaforwardvoltagedrop(Vf)of1.2VacrosstheLEDwithacurrent(If)ofabout10mA.

Whilethealarmcircuitisclosed,thecurrentflows,andtheLEDison.ThiskeepsthetransistoronandtheinputtotheGPIOportisheldlow.Ifthealarmcircuitisbroken,theopto-couplerLEDswitchesoff,andthisinturnswitchesoffthetransistor.TheGPIOinputisthenpulledhighbythe10-Kohmresistor.

Thisisquitesimplebuteffective,eh?

Theotheradvantageofthiscircuitisthatitshouldfailpositive—thatis,iftheopto-couplershouldfailforanyreason,thealarminputontheGPIOportshouldbepulledhigh,thustriggeringitratherthanitjustfailingsilently.

WirelessPIRmotionsensorsWirelessmotionsensorsarenowcommonlyavailableatalowcost,allowingthemtobeinstalledpracticallyanywherewithoutanywiringfromthealarmcontrolpanel.Someofthemstillrequireanexternalpowersupply,butmanyoperateonbatteries.Thealarmsystemmustcontainawirelessreceivercompatiblewiththewirelesssensor.

Inthissection,we’lltakealookathowwecanuseourRaspberryPi-basedsecuritysystemwithwirelessreceiverdevices.

433-MHzwirelessalarmsystemsWirelesssystemsuseanunlicensedradiofrequencytocommunicatebetweenthevariouscomponentsofanalarmsystem.IntheUK,thetwomostpopularfrequenciesusedare433MHzand868MHz.Whilethemorerecentsystemsnowusethe868-MHzfrequency,433MHzisstillinwidespreaduseasithasaslightlylongerrangethanan868-MHzsystem.However,the433-MHzbandisalsousedbymanyotherdevices,whichmakesitcongested,whereas868MHzisgenerallyusedonlyforalarmsystems.

Whilewirelesssecuritysystemscanbeconvenient,it’simportanttounderstandtheadvantagesanddisadvantagesofusingwirelessratherthanwiredsystems.

Theadvantagesareasfollows:

TheireaseandspeedofinstallationTheireaseofremoval,whichmeansthatyoucantakethemanywherewithyouExpandingthesysteminthefuturecanbeeasier,withmostsystemsautomaticallydetectingnewunits

Thedisadvantagesareasfollows:

Theyaremoreexpensivethanwiredsystems,sometimesthreeorfourtimesthecostTheyarenotassecureaswiredsystemsandcannotachieveasecuritygradinggreaterthantwoinaccordancewithEuropeanStandardBSEN50131(although,thisgradeissuitablefordomesticproperties)WirelessdevicesneedtohavetheirbatteriesreplacedatregularintervalsWirelesssystemsarelessreliableandsusceptibletointerferenceandevenradiojamming

Connectinga433-MHzreceiverInthepast,itwaspossibletorolloutyourown433-MHzreceiverfortheRaspberryPiusinganinexpensivereceiver,suchastheXY-MV-5Vmodulealongwiththe433-UtillibrarythatwasputtogetherbyaguycalledMarkWolfe,acontributoronGitHub.Essentially,hegatheredtogethercoderelatingto433-MHzcommunicationsandputitallintothislibrary.OriginallydevelopedforArduino,thishasnowbeenportedtotheRaspberryPi.

Youcanthenuseareadilyavailabletransmitter,suchasakeyfoboranyother433-MHztransmitter,andtakealookattheincomingcodeasyoupresseachbuttononthetransmitter.

AXY-MK-5VGeneric433-MHzreceivermodule

Findingasuitable433-MHzreceivershouldbeeasyaswebsitessuchasAmazonandeBayareawashwiththem,andtheycostaslittleasacoupleofpounds.

NoteNotethatthe433-MHzbandisafreeformanytypesofdevices.Assuch,therearevariousdifferenttypesofreceiver,andalthoughtheymayallstatethattheyare433-MHzreceivers,theycanoperateusingAMorFM,andsomeonlydetectcertaintypesofdata.Some,suchastheQuasarQAMrange,mayalsorequirespecialdecoderchipsinordertoreadtransmitteddataandmayonlyworkwithpairedtransmitters.

Thereceivermodulecanpickupsignalsfromakeyfobremotecontrol,suchastheoneshowninthefollowingimage(thiscanbepickedupfromthehomesecuritysectionofanylocalDIYstore),whichgetsanoutputasaseriesofsquarewaves.Thesesquarewavesarethendecodedbythe433-Utilsoftware.

ANovar/Blyss433MHzwirelessremotecontrol

IlikedthisparticularremotecontrolbecauseIthoughtitwouldbegoodasthearmanddisarmdeviceforourhomesecuritysystem.IwilltalkaboutarminganddisarminginChapter8,AMiscellanyofThings,wherewewilllookatthewaystoachievethis.

Thealternativeapproach(becausewehavenochoice)Istartedofftheprevioussectionwiththewords“Inthepast…”.Thisisbecauseinrecenttimes,I’venotbeenabletogetthe433-Utilsoftwareworkingwithreceivermodules,whichusedtoworkinthepast).I’mnotentirelysurewhythisisso;however,Icanonlyguessthatbecausethesoftwareuses“bitbanging”todecodeincomingdatasignals,thetimingisnolongercorrect,perhapsbecauselaterRaspberryPiboardsarefasterandthereforemessuptheroutines.

NoteWhatisbitbanging?

Bitbangingisawayofusingsoftwareforserialcommunicationinsteadofdedicatedhardware.Thesoftwareisresponsibleforalltheparametersofthesignal,includingtiming,levels,andsynchronization.Bitbangingcanbeseenasabitofahack,butitdoesallowtheimplementationofdifferentprotocolsataverylowcostwithoutanyhardwarechanges.

So,inordertomakeourliveseasier(andactuallymakethedeviceworkonallflavorsofPi),wewillresorttousingadedicatedreceivermodulethatyoucanpickupforlessthan

£5onAmazonanddoesn’trequireallthissoftwarebitbangingnonsense.You’llnoticefromthefollowingimagethatitstillusesasimilarXY-MK-5Vradioreceiver;it’sjustthatthehostboarddecodesthesignalsforusandswitchesarelayonoroffinresponsetoacommandfromtheremotecontrol.

NoteIfyou’restillinterestedinthe433-Utilsoftwareprojectandwanttotryandrolloutyourownreceiver,youcanfindtheoriginalprojectathttps://github.com/ninjablocks/433Utils.

AHielectransmitterfobandreceivermodule,availableonAmazon

Thefactthatitjustswitchesarelayonandoffmeansthatwecaneasilyimplementthisinourhomesecuritysystembecauseitsimplyactsasaswitch.Whenyoupressthebuttononthetransmitter,therelayswitchesthecontactson;pressitagain,andtherelayswitchesoff.Thescrewterminalsontheboardprovideuswithaccesstotherelayterminals.

ThereceiverwiringdiagramAswearejustdealingwithaswitchinput,wecanusethesamecircuitaswedidwiththezonecircuitearlierbutconnectedtoourarm/disarmGPIOinput,whichwe’lldetermineinChapter9,PuttingItAllTogether.

CircuittointerfacethereceivermodulewithaGPIOinput

Whenthereceivermoduleswitchestherelayon,thiswillcompletethe12Vcircuitthroughtheopto-coupler’sLEDbyturningiton.ThiswillmakethetransistorpulltheGPIOpindowntoground,givingitalowinput.

Youcanusethistypeofcircuitforanypairedreceiverforthewirelesssecuritydevicesthatyouwanttouseinyoursystem.

LoggingdetectiondataWithanysystem,it’susefultobeabletologdatawhensomethinghappens.Wecandothiswithourdetectorstoobywritingtoalogfileeverytimeadetectorinazoneistriggered.Thisway,youcankeepalogofeverytimesomeoneentersaroom,whichyoucanreviewatalaterdateevenifthesystemisn’tarmed.Youcanalsokeepalogofwhenthesystemisarmedanddisarmed.

Here’sasimplescriptthatshowsyouhowtodothiswheneveraneventhappensonourzonesconnectedtotheGPIOinputs:

#!/bin/bash

#setuptheI2Cexpansionport

#resetstatus

CURR_STATE="0x00"

LAST_STATE="0x00"

#pathtothelogfile

LOG_FILE="/etc/pi-alarm/zones.log"

#loopforever

whiletrue

#readthegpioinputs

CURR_STATE=$(sudoi2cget–y10x200x12)

#checkifstatehaschanged

if["$CURR_STATE"!="$LAST_STATE"]

#writechangetologfile

TIMESTAMP=`date"+%Y-%m-%d%H:%M:%S"`

echo"$TIMESTAMPZoneStatusChangedfrom$LAST_STATEto$CURR_STATE"

>$LOG_FILE

$LAST_STATE=$CURR_STATE

sleep1

Theprecedingexampleisquitesimple,butitcanbemademoreusefulbyactuallywritingoutthezoneorzonesthatchangebydecodingthehexvaluethat’sreturnedbythei2cgetcommandintheconstituentzones.

NoteInChapter9,PuttingItAllTogether,you’lllearnhowthisisdoneinordertodisplaytheindividualstatusofeachzoneonawebpage.Youcanuseexactlythesametechniquetodothisforyourlogfilesand,infact,outputtothelogfilebyexpandingonthesamescript.

SummaryInthischapter,westartedoffbylearninghowpassiveinfraredsensorsareusedtodetectmotiontoprotectapredefinedcoverageareafromintrusion.Wethenlookedatconnectingthesetotheinputsonourportexpanderviaopto-couplersaswewillnowuse12Vtopowerthealarmzonecircuits.

Wethenlookedatwirelessalarmsystemsthatoperateontheopen433-MHzband,whichiscommonlyusedforsecuritydevices.Afterexploringthepossibilityofusingthelegacy433-Utilbit-bangingsoftwareonourRaspberryPitodecodethesignalstransmittedbydevicesusingasimplereceiver,weoptedtouseapairedreceiverdevicethatwillinterfaceeasilywithouralarmcircuitinputs.

Finally,wecreatedasimplescriptthatwilllogthechangesinouralarminputstoatextfile,whichcanlaterbeexpandedtologexactlywhat’sgoingonwiththesystemindetail.

Chapter6.AddingCamerastoOurSecuritySystemUntilnow,we’vebeenputtingtogethertheelementsthatwillallowustoconnectsensorstoouralarmsystemtodetectintrusionsusingeitherswitchesorpassiveinfra-redmotiondetectors,whichinturnwilltellourRaspberryPithatsomethinghashappenedinaparticularzone.Theseelementswillallcometogetherasawholesystemlaterinthisbook.

Oursystemisnowgoingtobecomeawholelotmoresophisticatedwiththeadditionofcamerastotakepicturesandvideoclips,ande-mailthemtousstraightawaywhenitdetectssomething.

We’llalsousee-mailtosendusalertsonoursmartphonewhenwe’reoutandaboutwhenanyofthesensorsinthesystemaretriggered.

Inthischapterwewillcoverthefollowingtopics:

SettinguptheRaspberryPicameramoduleandlearninghowtocapturestillsandvideoimagesLearninghowtooverlaycapturedimageswithtextandtime-stampsTriggeringimagecaptureswithamotiondetectorE-mailingtheimageandvideofilestousinrealtimeUnderstandingthedifferencesbetweencapturingimagesduringthedayandduringthenightSwitchingonandoffsecuritylightingandotherhigh-currentdeviceswhenrequiredConnectingaUSBwebcaminsteadofthenativecameramodule

PrerequisitesYou’llneedthefollowingpartsforthischapter,ontopofthecomponentsusedinthepreviouschapter:

ARaspberryPistandardcameramoduleARaspberryPiNoIRcameramoduleAnInfra-RedLEDarrayand/orvisibleLEDarrayAUSBwebcam

TheRaspberryPicameramoduleTheRaspberryPiCameraModuleisanofficialRaspberryPiaccessorythatworkswithallmodelsofthePi,andcanbeusedtotakehigh-definitionstillsandvideoimages.ItconnectsdirectlytothePiboard’scameraserialinterface(CSI)port,whichisdedicatedtothesemodulestoenablehigh-speedoperation.

Thecameraitselfisa5megapixelfixed-focussensorsupporting1080p,720p,andVGAvideomodesandstillcaptures.

TheofficialRaspberryPiCameraModule

Youcanalsoobtainhousingsforthecameramodules,which,unlessyou’regoingtobuildyourownenclosureforthecamerasystem,Irecommendyouuse.

RaspberryPicamerahousingscomeinvariouscolorsandstyles

ConnectingthecameramoduleAspreviouslymentioned,themoduleconnectsdirectlytotheRaspberryPiboardviaitsdedicatedcamerainterfaces,asshowninthefollowingimage.Whenconnectingthecamera,thecontactsideoftheribboncableistowardtheHDMIconnectorandthebluesideofthecableistowardthenetworkconnector.

Connectthecameramoduletothededicatedinterface

Asyoucanseeinthefollowingimage,theribbonconnectorisnotthatlong,sothecameraneedstobelocatedclosetotheRaspberryPi.Byusingacameraenclosure,youcouldactuallymountthecameradirectlyontopoftheRaspberryPicaseitself,ifthatworksforyou.

Thecameramodule,housedwithinanenclosure

SettingupthecameramoduleBeforewecanusethecameramodule,weneedtoenablecamerasupportontheRaspberryPi.Todothis,weusetheraspi-configtool,aswedidwiththeI2Cbusearlierinourjourney.

1. ConnecttoyourRaspberryPithelazywayfromyoursofausingSSH,ordirectlyusingakeyboardandmonitor.

2. Onceyou’veloggedin,launchtheconfigtoolwiththefollowingcommand:

$sudoraspi-config

3. Andthen,select5EnableCamera.

4. You’llthenbeaskedtoconfirmwhetheryouwanttoenablecamerasupport.

5. Select<Enable>.6. Then,selectFinishandrebootyourPitoenablethecamerasettings.

TestingthecameramoduleOnceyourRaspberryPihasrebooted,yourcamerashouldbeenabled.Wecantestthisbytakingastillimageusingtheraspistillutility:

$raspistill–v-otest.img

Thiswilldelayfor5secondsthentakeapicture,whiledisplayingvariouspiecesofinformation,suchasthatshowninthefollowingscreenshot:

NoteThecameramoduleneedsatleast128MBofGPUmemorytooperateproperlyonRaspian.Ifyouexperienceanyissues,firstensurethatthethegpu_memsettinginthe/boot/config.txtconfigurationfileissettoatleast128.

Andifallgoeswell,youshouldfindthefile,test.jpg,inyourhomefolder.Asyou’reconnectedviatheshell,youwouldn’thaveseenthe5secondpreviewimagedisplayedwhenthecommandwasrunning.

IfyoudownloadtheimagefiletoyourPC,youshouldseeanicequalitysnaptakenbythecameramodule.

ThetestphototakenbytheRaspberryPiCameraModule

TipIfyoufindthatraspistilloutputserrorswhenyourunit,ensurethatitisconnectedproperlyatbothendsoftheribboncable.Oneothercatchisthatsometimestheribbonthatconnectstheactualcameralenscomponenttothetinyconnectoronthecameraboardcancomeloose.Justensurethatthisissecurelyconnectedtoo.I’vehadthisissueacoupletimesafterthecameramoduleshavebeentakenoutofmyboxofrandomtestbitstobeused.

Theraspistillutilityhasloadsofoptionsformanipulatingtheimagesitcaptures,andwe’llusesomeofthemabitlaterinourcapturescript.Inthemeantime,toseetheavailableoptions,runraspistillwithoutanyoptionsandtheywillbelisted:

$raspistill

BeavideostarNowthatweknowourcameramoduleisworking,wecantryandcapturesomevideo.Todothis,we’llusetheraspividutility.Thefollowingcommandwilltake5secondsofhigh-definitionvideoandsavethefiletoyourRaspberryPi:

$raspivid–otest.h264–t5000

You’llnoticethatfileiscalledtest.h264—thisisbecausethevideoiscapturedasarawH.264videostream.Unfortunately,notmanymediaplayerswillhandlethesefiles(althoughVLCplayerwill—itrocksandhandlespracticallyanythingyouthrowatit—getitonyourPCatwww.videolan.org).

Ifyouwanttoplaythefileonsmartphonesandconventionalmediaplayers,thenwewillneedtowrapitinacontainerformat,suchasMPEG-4,andgivethefilea.mp4extension.

Todothis,we’llusetheGPACpackage,whichisanopensourcemultimediaframework.ItcomeswithautilitycalledMP4Box,whichisatoolwe’llusetocreateanMP4containerforourvideofile:

1. First,installtheGPACpackage:

$sudoapt-getinstallgpac

2. Onceit’sinstalled,runthecommandtoconvertthetestvideowecreated:

$MP4Box-fps30-addtest.h264test.mp4

Youshouldnowhavethefile,test.mp4,whichyoucandownloadandplayonyourPCorsmartphone.

TipAnotherpopularconversiontoolisffmpeg,whichIusealotonWindowstoconvertvideofiles;however,itcanbequitecomplexandalthoughthereisapackagefortheRaspberryPi,Iactuallycouldn’tgetittoconvertproperlyonthePi.MP4Boxismuchmorestraightforwardandfittingforourneeds.

CaughtoncameraSo,wenowhaveamethodofcapturingstillimagesandvideo,whichwecanputtouseinoursecuritysystem.Ifwewanttohavethisrunningconstantly,wecouldwriteascripttotakevideoconstantly,butthiswouldsoonfillupourmemorycardandwouldn’tbeparticularlyefficient.So,we’llcombineourcamerasystemwiththemotiondetectorsweconnectedearlier.

Inthelastchapter,wecreatedanalarmzonewhichhadacoupleofsensorsandamotiondetectorconnectedtooursystemontheinputGPA0.So,let’swriteascriptthatwilltakeavideoclipwheneverthemotiondetectoristriggered:

#!/bin/bash

#setupportexpander

#loopforever

whiletrue

#readtheGPAinputs

GPA=$(sudoi2cget–y10x200x12)

#detectthezoneoninput0

if[$GPA=="0x01"]

#circuitnormallyclosedsozoneisOK

#shortdelay

sleep0.5

#zoneisactivatedsotakea20secvideoclip

#filenamewillbebasedoncurrenttimestamp

sDate='date+%d%m%y'

sTime='date+%T'

echo"Zone1Activateat$sDate$sTime"

#takevideoclip

raspivid–o$sDate$sTime.h264–t20000

#converttoMP4

MP4Box-fps30-add$sDate$sTime.h264$sDate$sTime.mp4

YouhavenewmailHavingtheimagesstoredonyourRaspberryPiisnotreallymuchuse—ideally,youwouldwanttheimagessenttoyoustraightaway,assoonastheyarecaptured,sothatyoucanviewthemonyoursmartphone.

Aneasy,quick,andreliablewaytodothisistosimplyhavetheme-mailedtoyou.Hencewe’regoingtoaddane-mailingfunctionalitytoourhomesecuritysystemsothatimagecapturesareattachedtoamessageandsenttoyoure-mailaddressstraightaway,whichyoucanaccessfromyoursmartphone.TheimagescanthenberemovedfromyourRaspberryPitopreventtheSDcardspacefrombeingcloggedupwiththesereasonablylargefiles.

Settingupthee-mailsenderclientFortunately,therearesomegoodpackagesavailablethatwillhelpuswiththis.Carryoutthefollowingstepstoinstalltheemailpackagesweneed:

1. Updatethepackageinstallerwiththefollowingcommand:

$sudoapt-getupdate

2. InstallandsetuptheSMTPclientwiththefollowingcommand:

$sudoapt-getinstallssmtp

You’llnowneedtosetuptheclienttosendemailsthroughyouremailaccount.Inthefollowingconfigurationfile,I’veassumedthatyouhaveaGmailaccount.Thesettingsmaybedifferentifyouuseanotheremailprovider.

3. OpenthessmtpconfigurationfileusingNanooranothertexteditor:

$sudonano/etc/ssmtp/ssmtp.conf

4. Replacetheentrieswiththefollowingconfiguration:

root=<your-username>@gmail.com

mailhub=smtp.gmail.com:587

rewriteDomain=gmail.com

AuthUser=<your-username>@gmail.com

AuthPass=<your-password>

FromLineOverride=YES

UseSTARTTLS=YES

5. ssmtpcanbeusedonitsownbutcanbeabitofafaffwhileautomaticallysendingemails(bydefault,youmanuallytypetheemailinwiththecommandline,orcreateatextfile),sowe’realsogoingtoinstallthemailutilspackage:

$sudoapt-getinstallmailutils

6. Onceit’sinstalled,wecanusethemailcommandtosendemailsmoreeasily.Sendatestemailthroughthe(G)mailaccountthatwesetupearlier,usingthefollowingcommandtomakesureyoursettingsareworking:

$echo"TestEmail"|mail–s"TestPi-Mail"me@mydomain.com

Ifallgoeswell,youshouldreceivethetestemailinyourmailboxwithinafewsecondsorso.

SendingattachmentsNowthatwecansendbasicemailsfromourhomesecuritysystem,let’strysendingthestillimagetakenfromourcameraearlier.Butfirst,weneedtoinstallyetanotherpackagetohelpuswiththis:

$sudoapt-getinstallmpack

Oncethat’sinstalled,youcansendthetestimagefilewetookpreviouslybyusingthefollowingcommand:

$sudompack–s"SecurityPhoto"test.jpgme@mydomain.com

Wenowhavealloftheelementsneededtosendalertsandimagesfromourhomesecuritysystemdirectlytooursmartphoneusingemail.

Wherewasthattaken?Ordinarily,youcouldjustannotatetheemailmessagewithwhereandwhentheattachedimagewastaken,butthatwouldn’tbeascoolasactuallyoverlayingtheimagewithsometext,wouldit?Solet’sdosomemagicwiththehelpofimagemagick,whichisapopularcommand-lineimagemanipulationtool.Installitwiththefollowingline:

$sudoapt-getinstallimagemagick

We’llnowusethecommandlinetotakethetestphotothatwetookearlier,overlaysometextusingoneoftheimagemagickutilities,andsaveittoanotherfile:

$converttest.jpg–fillred–pointsize48annotate+20+60'Camera1'

annotated.jpg

Afterafewseconds,thiswillhavegeneratedafilecalledannotated.jpgcontainingourimagewithCamera1writteninredinthetopcorner.Whenweputallofthistogetherinourfinalsystem,we’llalsooverlaytheimagewithatimestamp.

NoteAtthemoment,theimagesgeneratedbytheraspistilltoolareprettylarge,beinghighresolutionphotos.Thismakesmanipulatingandsendingthemabittime-consumingasfarasprocessingtimeisconcerned,sowhenwebuildourfinalsystem,we’llbeusingtheraspistilloptions,–w,–hand,–q,toreducethesizeandqualityoftheimagestomakethesystemmoreefficient.

Tocapturesmallerimagefiles,tryusingthefollowingcommand:

$raspistill-otest.img–h768–w1024–q25

NightvisionThestandardRaspberryPicameraisgreatfortakingdaytimesnapsofpeoplewalkingupthegardenpath,butwhenitcomestonighttimeshots,it’snotreallysuitable.Therearetwowaysofdealingwiththis:thefirstistoilluminatethecaptureareawithabrightlightwhenthePIRdetectoristriggered,andthesecondistousetheRaspberryPiNoIRcameramoduleandaninfra-redLEDarraytoletthecameraseeinthedark.Moreaboutthatinaminute.

TheRaspberryPiNoIRcameramodule;itlookssimilartothestandardmodel

AnilluminatingexperienceInordertoswitchonalightorLEDarrayfromtheRaspberryPiGPIOorourportexpandercircuit,weneedsomethingthatwillallowustodrivehighercurrentsandvoltagesthancanbeprovidedbytheGPIOportsalone.

AgoodcandidateforthisistheTIP120Darlingtontransistor,whichwillallowustoswitchonandoffloadsofupto80Vand5AfromourGPIOpins.Inourfullsystemlateron,we’regoingtousePortBofourMCP23017portexpandertocontroloutputs,buttheprinciplestandsforanyoftheGPIOoutputsavailabletous.

TIP120transistorscanbeboughtcheaplybutcandrivelargeloads

ThefollowingcircuitshowshowwecandrivebigloadsfromourGPIOportoutputs.

Inourexamplecircuit,we’reusingaGPIOoutputpintocontrolthebaseofourtransistorviaa220ohmresistor.WhentheGPIOpingoeshigh,thetransistorisswitchedonandallowsthe12VcircuittoflowthroughtheLEDarray.

Intheprecedingcircuit,thereisnocurrentlimitingfortheLEDsbecausetheyareconnectedinseries,andsowithnineofthem,eachdroppingabout1.5Vacross,thisisaboutrightfora12Vsupply(yesIknowI’veonlyincludedsixLEDsherebutit’sjustforillustration).Remembertoadjustforyourparticularneeds.Thiscircuitcouldeasilydriveotherloads,suchasbulbsorsounders.

NoteIfyouintendtodrivehighpowerloads,youwillprobablyneedtoattachtheTIP120toaheatsinkthatwilldissipateanyheatandpreventitfromover-heatingandburningout.Inourcircuitthatwasdemonstratedpreviously,however,youprobablywon’tneedoneaswe’reonlydrivingacoupleofhundredmilliwattsatmost.

TheElaboratelightswitchre-visitedExpandingonceagainonourelaboratelightswitchfrompreviouschapters,wecanonceagainwriteaBashscriptthatwillswitchonourcameralight,takeasnapwiththecamera,ande-mailittouswhenaPIRdetectoristriggered.

Forthefollowingscript,we’reassumingthattheoutputcontrollingtheTIP120transistoristheRaspberryPIGPIO17pin(D0orpin11ofourconnector),whichreplacestheLEDinourearlierset-up.TheinputfromthePIRtriggeris,again,connectedtotheGPA0(portA,datapin0)ofourMCP23017portexpander.Alltheotherinputsaretiedlow,asbefore,using10Kresistors:

#!/bin/bash

#setuptheHighLoadGPIOpin

#setupportexpanderPortAforinputs

#cleartheoutputbydefaulttoswitchlightoff

#loopforever

whiletrue

#readthesensorstate

#PIRisnormallyclosedsopinisheldhigh

if[$SWITCH!="0x01"]

#PIRwastriggered–pintakenlow

#switchonlampdriver

sleep0.5

#takeastillimage

sudoraspistill–o–image.jpg–h768–w1024–q25

#emailtheimage

mpack–s"SecurityAlertPhoto"test.jpgme@mydomain.com

#switchoffthelampdriver

#shortdelay

sleep0.5

pir-camera-trigger.sh

You’llnowseethatwe’vestarteddevelopingthefoundationsofthesoftwarethatwillcontrolourhomesecuritysystem.

Isthatabadger?Ifyoudon’twanttoilluminateanareabeforecapturinganimage,youcanuseinfra-redlightinginconjunctionwithacompatiblecamera.ThestandardRaspberryPicameramodulewon’tworkwithinfra-redlightingbecauseitcontainsaninfra-redfilter,butwecanusetheNoIRversionofthecameramoduleinstead.

TheRaspberryPiNoIRcameramoduleisexactlythesameasthestandardone,exceptthatitdoesn’thaveaninfra-redfilterbuiltin,whichmeansitwillseeinthedarkwiththeaidofinfra-redlighting.Thismakesitgoodforwatchingbadgersatnightaswellasforuseinourhomesecuritysystem.

Youwillneedaninfra-redLEDarrayorclustertoinvisiblyilluminatetheareayouwanttocapturewiththecamera.Thesearereadilyavailableinvariousformfactorsandintensities,oryoucanbuildyourownusingindividualinfra-redLEDspurchasedfromanelectronicsstore.

TheKingbrightinfra-redLEDclusterrunsfroma6Vsupply,whichmeansyoucanconnecttwoinseries—oneoneithersideofthecamera.

ConnectinganddrivingtheLEDclustermodulesworksexactlythesameasourilluminatinglightabove,usingtheTIP120drivercircuit.Theonlydifferenceisthatwehumanscan’tseewhentheLEDsareon.

UsingUSBcamerasInsteadofusingtheRaspberryPiCameraModule,it’salsopossibletouseastandardUSBwebcamtotakestillimages.YoushouldbeawarethoughthatthededicatedcameramoduleisfarsuperiortoaUSBwebcamintermsofimagequality.Although,youmayalreadyhaveawebcamknockingaboutinyourboxofbits,sowhynottryit?

InstallingthewebcamAfteryou’veconnectedyourwebcamtoaUSBportonyourPi,youcancheckwhetherit’sbeenrecognizedusingthelsusbcommand:

$lsusb

I’musingaLogitechwebcamthatgetsreportedasfollowswithlsusb(Device006):

pi@raspberrypi~$lsusb

Bus001Device002:ID0424:9514StandardMicrosystemsCorp.

Bus001Device001:ID1d6b:0002LinuxFoundation2.0roothub

Bus001Device003:ID0424:ec00StandardMicrosystemsCorp.

Bus001Device006:ID046d:08d8Logitech,Inc.QuickCamforNotebook

Deluxe

NoteNotallwebcamswillworkwiththeRaspberryPi.EventhoughitmayberecognizedasaUSBdevice,itmightnotactuallyworkproperlywiththeoperatingsystemandcreateavideodevice(forexample,/dev/video0).Forexample,anoldcheapTrustwebcamIhadappearedasaUSBdevicebutwouldn’tcaptureanyimages.

YoucancheckwhetheryourwebcamislikelytoworkwiththePibycheckingyourmakeandmodelathttp://elinux.org/RPi_USB_Webcams.

So,nowthatthePiknowsthatwehaveawebcamdeviceattached,wecanusethefswebcamutilitytocaptureimageframes.Youcanfindoutmoreaboutfswebcamfromthedeveloper’ssiteathttp://www.sanslogic.co.uk/fswebcam.

Installfswebcamwiththefollowing:

$sudoapt-getinstallfswebcam

TakingasnapYoucannowtestthewebcambycapturingastillimage,whichcanbedonebyrunningthefollowingcommand:

$fswebcamtest.jpg

Youshouldexpecttoseeoutputsimilartothefollowing:

Notefswebcamhaslotsofoptionsforthingsliketheresolutionandqualityoftheimage.Usethecommandfswebcam-?togetalistofalloptions.

Snapsnapsnapfswebcamdoesn’ttakevideostreams,butyoucansetituptotakeaseriesofframesatregularintervals.Forexample,totakeasnapevery10seconds,youcanusethefollowingcommand:

$fswebcamframe.jpg-l10

Anexampleofhowthiswouldbeusefulcanbedemonstratedbysettingthewebcamtotakeasnapeveryfewsecondsinthebackground(the–qswitchrunsfswebcaminthebackground).Whenoursecuritysystemistriggered,wecouldthentakethelatestimagesnappedwiththewebcamwhichcouldbelookingdownyourpathway.

Forthepurposeofputtingtogetherourentiresystemlaterinthisbook,we’llbefocusingontheRaspberryPiCameraModule,butyoucanalwaysreplacethecodewiththepreviousexamplesifyouwanttouseUSBwebcamsinstead.

You’llnoticethatfswebcam,unlikeraspistill,hastheabilitytooverlaytheimageswithtimestampinformation,soyoudon’tneedtoworryaboutoverlayingtextaswedidpreviously.Lookatthefswebcamcommandlineoptionsformoreinformation.

ThemulticamerasetupItmayhaveoccurredtoyouthattheRaspberryPihasonlyonecameramoduleinput.Now,thisisobviouslylimitingifyouwanttohavemultiplecamerasaroundyourpropertythataretriggeredbymotiondetectors.

However,thereisnothingstoppingusfrombuildingstandaloneunitsthathaveaseparateRaspberryPiboardwithaPIRdetector,CameraModule,andnetworkconnection,eitherusingaWi-FidongleorEthernet.

BecauseyouonlyneedasingleinputtotheRaspberryPitodetectwhenthePIRmotionsensoristriggered,youcanusetheon-boardGPIOporttoconnectthesensor,ratherthanusingaportexpander.TheRaspberryPiwillemailthealertoverthenetwork,andcouldalertthemaincontrollerPiifrequired—makingitaslavesensordevice.

YoucanreadilyobtainsmallPIRdetectors,suchastheParallaxoneshownnext,whichyoucanmountontoaRaspberryPiCasealongwiththecameramodule,creatingaself-containedunit.

AParallaxPIRmotionsensor(type555-28027)

TheSlavedriverWhileitmayseemquiteelaboratetohaveaRaspberryPiforeachcamera—thinkaboutit—youcanactuallybuildeachcameraunitwithallofthecomponentsforaround£50,whichissignificantlycheaperthanbuyingawirelesssmartcamera.Ifyoureallywanttobeclever,youcouldalsousethisasaslavedevicetoacceptfurthersensorinputslocaltotheunit.

ThereisnothingtostopyoufromconnectingaGPIOoutputpinontheslaveunittodriveaninputonthemaincontrollerandcontrolthepindependingonthestateofitslocalsensors.Byrunninga6-corecablebetweentheunits,youcouldevenpowertheslaveunitifyourpowersupplyismanenough(you’dneedtohaveasupplyof5V@1AfortheslavePirunningalongthewire).

I’mnotgoingtogointoanymoredetailaboutthisconfigurationatthistime,butyoucouldsetyourselfachallengetocreateafullydistributedhomesecuritysystemusingmultipleRaspberryPisandthebuildingblocksandconceptslearnedinthisbook.

SummaryInthischapter,welearnedhowtoconnectbothRaspberryPicameramodulesandUSBcamerastoourPiboardinordertotakeimageandvideocaptureswhenrequiredbyourhomesecuritysystem.Wealsolearnedhowtooverlayourimageswithinformativetextandhavethefilesimmediatelyemailedtous.

Inordertocaptureimagesfromourcameraatnight,wealsolookedatwaystoilluminatethecaptureareausingbothvisibleandinfra-redlighting,withtheabilitytoswitchthelightingonandoffasrequiredbyusingahigh-currentDarlingtontransistordriver.

Inthenextchapter,we’regoingtogetdowntothebusinessofputtingtogethermodulesbybuildingamobile-optimizedweb-basedcontrolpanelforourhomesecuritysystem.We’lllearnhowtosetupaWebserveronourRaspberryPiandmanipulatefilesusingourWebcontrolpanel,whichmeansthatwe’llstarttoexplorehowalloftheelementswe’veencounteredsofarcancometogetheraspartofourfinalsystem.

Chapter7.BuildingaWeb-BasedControlPanelWe’venowgotallofourhardwareelementstogetherforustocreateacompletehome-securitysystemfeaturingcontactswitchesforourdoorsandwindows,andmotiondetectorsandcamerastotakehappysnapsofwannabeintruders!I’vedeliberatelyguidedyouthroughthisinamodularfashionsothatyoucanpickandchooseandexpandonthehardwaresensorelementsthatsuityourrequirements.InChapter9,PuttingItAllTogetherwewillbewiringallofthistogethertoformthecompletesystembasedonzonesthatwelookedatearlier.

Onethingthatallhomesecuritysystemsrequireisacontrolpanelthatallowsustoarmanddisarmthesystemandmonitorthestatusofthezoneswithinoursystem.Wemightalsowanttodothingssuchasonlyarmcertainzones,orhavethesystemautomaticallyarmanddisarmatcertaintimesoftheday.

Thehardwarerequiredforthis,suchasswitches,LEDs,andLCDdisplays,canbequiteexpensiveandtime-consumingtoputtogether;theycanalsomakethesystemlessconfigurableandflexible.So,inoursystem,we’regoingtobuildaWeb-basedcontrolpanelthatwecanaccessfromourmobilephonebrowser.Thisalsomeansthatwecancontrolthesystemremotely,whenweareoutofthehouse.

Inthischapter,wewillcoverthefollowing:

DefiningthescopeofourhomesecurityintermsofthenumberofzoneswewillbemonitoringandtheI/OportswewilluseLearninghowtoinstallandconfigureawebserveronourRaspberryPiDevelopingabasicHTML5webpageforouralarmcontrolpanelLearninghowtousePHPscriptstodynamicallyconfigureoursystemfromthewebpage

InstallingthewebserverThereareseveralwebserversreadilyavailablethatwecouldinstallonourRaspberryPi,andtheywouldallbesuitableforoursystem.ButIlikethelighttpdwebserverasit’seasytouseandlightweight.lighttpdisoftenreferredto,andaffectionatelyknownas,“Lighty”—whichtobehonestislessofamouthfulthanlighttpd.

AswellastheWebserveritself,we’realsogoingtoinstallPHPsupport,whichwillallowustowritedynamicwebpagestointeractwiththeLinuxsystem.Now,tobehonest,I’mnotamassivefanofPHPforcommercialWeb-baseddeploymentsformanyreasons,butforasmallembedded-Linuxsystemsuchasourhomesecuritysystem,it’sperfectandworksreallywell.It’salsoquitestraightforwardtogetintoifyou’veneverdoneserver-sideWeb-scriptingaswell.

Toperformthefollowingsteps,you’llneedtobeloggedintoyourRaspberryPiviatheterminalconsole(forexample,PuTTY):

1. Updatethepackageinstaller:

$sudoapt-getupdate

2. InstallthelighttpdWebserver:

$sudoapt-getinstalllighttpd

Onceinstalled,itwillautomaticallystartupasabackgroundservice,andwilldosoeachtimeyourRaspberryPistartsup.

3. InstallPHP5support:

$sudoapt-getinstallphp5-cgi

4. Now,weneedtoenablethePHPFastCGImoduleinourwebserver:

$sudolighty-enable-modfastcgi-php

5. Andfinally,weneedtorestarttheWebserver:

$sudo/etc/init.d/lighttpd

That’sit!YoushouldnowhaveyourPHPWebserverinstalled.Bydefault,thewebcontentfilesgetinstalledinthelocation,/var/www,andLightyinstallsatestplaceholderpageinthislocation,whichyoucanaccessfromyourbrowserbysimplyenteringtheIPaddressofyourRaspberryPi,asshowninthefollowingscreenshot:

TheLighttpdplaceholderpage

TestingthePHP5installationWhilewe’reatit,weshouldalsotestourPHPinstallation,asthisisfundamentaltobuildingourconsole.ThiscanbedonebywritingasimplePHPscriptpagethat,ifPHPisinstalledcorrectly,willreturninformationaboutitsenvironmentandconfiguration:

1. First,gotothewebcontentfolder:

$cd/var/www

2. InNano,createafilecalledphpinfo.php:

$sudonanophpinfo.php

3. Intheeditor,enterjustthefollowingsingleline,thensaveandexitfromNano:

<?phpphpinfo();?>

Now,inyourbrowser,entertheIPaddressofyourRaspberryPifollowedby/phpinfo.php,forexample,http://192.168.0.110/phpinfo.php,andyoushouldbepresentedwiththefollowingpage:

ThePHPinfopagegeneratedbytheWebserver

Nowthatweknowourwebserverisworkingproperly,wecanstartcreatingourconsolewebpage.

BeingincontrolSothatweknowwhatcontrolswewantonouralarmcontrolpanel,weneedtomapoutoursystemwiththenumberofzoneinputsandcontrolinputsandoutputs.Asyou’llrememberfromChapter3,ExtendingYourPitoConnectMoreThingswecanessentiallyhaveupto16zonesinoursystemusingthetwoI/Oportsonourportexpander.WealsohavetheeightGPIOpinsatourdisposalontheRaspberryPiboarditself.So,let’snowallocatetheseoutputsanddocumenttheminthetablethatfollows.

I’mgoingtosetupan8-zonesystemformyalarminputsusingportAontheI/Oexpanderboard,usingthenativeGPIOpinsforthingssuchasbuttonsandalertoutputs.Onereasonfordoingitinthisconfigurationisthatthesystemcanalwaysfail-safe—soiftheexpanderboardfails,theRaspberryPicanstillcommunicatealertsandbuzzersconnectedtoit.

Port I/OPin Label/Purpose

ExpanderA 0(A0) Zone1Input(Entry/ExitChannel)

1(A1) Zone2Input

2(A2) Zone3Input

3(A3) Zone4Input

4(A4) Zone5Input

5(A5) Zone6Input

6(A6) Zone7Input

7(A7) Zone8–Anti-TamperLoopInput

ExpanderB 0(B0)

R-PiGPIO 0(GP0) Arm/DisarmSwitch(Input)

1(GP1)

2(GP2)

3(GP3)

4(GP4) ArmedLED(Output)

5(GP5) Arm/DisarmBuzzer(Output)

6(GP6) AlarmLED(Output)

7(GP7) AlarmBell(Output)

ArmingyourselfThetermsarmanddisarmarealarmsystem-speakforswitchingthealarmmonitoringon(armingthesystem)andoff(disarmingthesystem).Zone1ofoursystemisgoingtobelinkedtothearminganddisarmingpartofthesystemasitwillbeconnectedtothesensorsonthedoorthatweleaveorenterfrom;thiswillbeaspecialzoneforentryorexitpurposes.

Whenwesetthealarm,weneedabitoftimetogetoutofthehouse.Thewaythatthesystemknowswe’veleftthepropertyisbymonitoringtheexitzonetoseeifwe’veopenedandthenclosedthefrontdoorbehinduswithinthetimeallowed.

Similarly,whenwereturn,wewillopenthefrontdoor,butwedon’twantthealarmtogooffstraightaway—weneedachancetodisarmthesystemwithinagivenamountoftime.Wewillarmanddisarmthesystemviaourweb-basedcontrolpanel,orbyusingaswitchofsomesortontheinputGP0.

ThemasterconfigurationfileOursystemwilluseamasterconfigurationfilethatwilltellithoweverythingissetupandconnected.Thisconfigurationfilewillbeusedbyboththewebcontrolpanelandthemainalarmcontrolscriptssothatthetwosub-systemscan“talk”toeachother.Let’screatethefilewithourinitialsettings.

ThesettingsfilewillbestoredinthesamelocationaswherewewillcreateourcontrolscriptsinChapter9,PuttingItAllTogether,whichisinthefolder./etc/pi-alarm.So,let’screatethisfolder,andgiveitexecuterightssothatourscriptscanberun:

$cd/etc

$sudomkdirpi-alarm

$sudochmod777pi-alarm

We’llnowcreatethemasterconfigurationfile,tobeusedbyoursystem,inthisfolder:

$cdpi-alarm

$sudonanoalarm.cfg

TipAsbefore,youdon’thavetocreateyourfilesinNanoontheRaspberryPi—youcancreatethemonyourdesktopcomputer,andthentransferthemtoyourPiusingSCP.

#ALARMMASTERCONFIGFILE#

#Numberofzonesinthesystem

NUM_ZONES=8

#Displaylabelsforeachzone

ZONE_LABEL_1="Zone1-Entry/Exit"

ZONE_LABEL_2="Zone2"

#Zonesthatareenabled

#Setto0toDisableor1toEnable

ZONE_ENABLE_1=1

ZONE_ENABLE_2=1

ZONE_ENABLE_3=1

ZONE_ENABLE_4=1

ZONE_ENABLE_5=1

ZONE_ENABLE_6=1

ZONE_ENABLE_7=1

ZONE_ENABLE_8=1

SYSTEM_ARMED=0

#Zonestatus

#Setto1ifzoneistriggered

ZONE_STATUS_1=0

ZONE_STATUS_2=0

ZONE_STATUS_3=0

ZONE_STATUS_4=0

ZONE_STATUS_5=0

ZONE_STATUS_6=0

ZONE_STATUS_7=0

ZONE_STATUS_8=0

alarm.cfgfile

CreatingthewebpageOurWeb-basedcontrolpanelisgoingtobeasinglePHP-drivenHTML5webpagewhichwillbemobileoptimized.HTML5isthelatestmark-upstandardforwebpagesandissupportedbymostmodernsmartphonesandbrowsers.Wewillalsocreateacascadingstyle-sheet(CSS)thatwillmakeourpagelookhalfreasonableonmobiledevices.

Tocreatethewebfiles,IrecommendthatyouusesomethingliketheexcellentNotepad++onyourdesktopcomputer,ratherthandoingitdirectlyontheRaspberryPi.Alternatively,ifyouareaseasonedwebdeveloper,youmayalreadyhaveyourIDEofchoice.

ThecontrolpanelHTMLtemplateThefirstthingwe’lldoiscreateanHTMLfilethatwecanusetotestourlayoutbeforeweputtheHTMLintoaPHPfiletomakeitinteractwithoursystem.Thismakesiteasiertotweakthewaywewantittolookbeforehand,withoutthePHPscriptsgettingintheway.

NoteThisisnotatutorialonWebdevelopment—thereisaplethoraofbooksoutthereonthatsubject—butIhopethecodeisclearenoughforyoutoworkoutwhat’sgoingon.ThecodeI’mgoingtoshowyouisfullyfunctional,soyoucanjustusewhatIgiveyouwithouthavingtodoanymore.Hopefully,itmakesyourcontrolpanellookOKtoo!

Thefollowingmark-upgivesyouabasiccontrolpanelwithstatusforour8zones,amasterarmanddisarmswitch,andswitchestoenableordisableanyofourzones.

The<head>sectionofthecodecontainssome<meta>tagsthathelpmobiledevicesknowthatit’samobile-friendlysite.Inthemain<body>mark-up,wehaveasectionforeachzonethatcontainsthezone’snameandanon/offswitch.Eachzoneisinitscontainersothatwecanalsohighlightaparticularzonethatneedsourattention,forexample,ifit’striggered.

YoucanfindthefullHTML5markupforourcontrolpanelinthealarm-panel.htmlfilelocatedinsidethecodefolderofchapter7.

GivingitsomestyleAtthemoment,thispagedoesn’tlookthatgreat(infact,itlooksawful,likesomethingfromthe1990s);itisn’tparticularlygoodformobiledevicesandwouldmostcertainlyfailthesausagetest.So,we’regoingtoapplysomestylingtomakeitlooknothalfbad.Althoughtheprecedingmark-upcontainsareferencetoaCSSfile—wehaven’tcreatedthatfile—sothisiswhatourpagecurrentlylookslike(asIsaid:itlooksawful):

Thewebcontrolpanelwithoutanystyling

ThefollowingCSS3mark-upisdesignedspecificallyforourcontrolpanel,anditmakesitlookquitenicewhilealsomakingitusableontouch-screenmobiledevices.TheCSSisquitelongandseemsoverwhelming,butyoudon’tneedtodoanythingwithit,orunderstandit,ifyoudon’twantto—theonlythingyouneedtoknowisthatit’sbeendesignedformodernbrowsersandsmartphones,sodon’texpectittoworkonInternetExplorer7,orprobablyevenIE9!

Inessence,itcontainsthestylingforthefollowing:

PreparingthebrowserforourmobilelayoutOurtextandzoneareasCreatingcoolswitchesinsteadofboringcheckboxesMakinganareaflashonandoffwhenweneeditto

/*Clearbrowsermarginandpaddingdefaults*/

body,div,dl,dt,dd,ul,ol,li,h1,h2,h3,h4,h5,h6,pre,form,

fieldset,input,textarea,p{

margin:0;padding:0;-webkit-text-size-adjust:none;

background:#ffffff;

color:#4A5651;

font-family:"TrebuchetMS",Helvetica,sans-serif;

font-size:10px;

height:100%;

padding:0;

margin:0auto;

max-width:320px;

min-width:240px;

text-align:left;

width:100%;

-webkit-box-shadow:0px20px40px0pxrgba(0,0,0,0.50);

-moz-box-shadow:0px20px40px0pxrgba(0,0,0,0.50);

box-shadow:0px20px40px0pxrgba(0,0,0,0.50);

p,.zoneLabel{

font-size:16px;

margin:5px;

line-height:1.4;

color:#4A5651;

#headerh1{

font-size:20px;

line-height:40px;

margin:0;

padding:00015px;

text-align:center;

text-overflow:ellipsis;

font-weight:bold;

.zoneControl,.masterControl{

border-bottom:1pxsolid#dddddd;

margin-top:5px;

margin-bottom:0px;

padding:5px;

display:block;

width:100%;

.zoneLabel{

font-weight:bold;

text-overflow:ellipsis;

input[type="submit"]{

border:none;

background-color:#0b70cc;

color:white;

height:32px;

display:block;

padding:4px7px;

float:left;

border-radius:8px;

position:relative;

bottom:1px;

margin-left:4px;

text-align:center;

input[type="submit"]:hover{background-color:#b2ceec;color:

#0b70cc;border:none;border:1pxsolid#b2ceec;}

/*Flashinganimation*/

@-webkit-keyframesflash{0%,50%,100%{opacity:1;}25%,75%{opacity:

@keyframesflash{0%,50%,100%{opacity:1;}25%,75%{opacity:0;}}

.flash{

-webkit-animation-name:

flash;animation-name:

flash;color:#f00000;

.animated{

-webkit-animation-duration:1s;

animation-duration:1s;

-webkit-animation-fill-mode:both;

animation-fill-mode:both;

animation-iteration-count:infinite;

-webkit-animation-iteration-count:infinite;

ON/OFFSWITCHSTYLES

TherathercoolOn/Offswitchstylingwasgeneratedon

https://proto.io/freebies/onoff/

.onoffswitch{

position:relative;

width:90px;

-webkit-user-select:none;

-moz-user-select:none;

-ms-user-select:none;

.onoffswitch-checkbox{

display:none;

.onoffswitch-label{

display:block;

overflow:hidden;

cursor:pointer;

border:2pxsolid#FFFFFF;

border-radius:20px;

.onoffswitch-inner{

display:block;

width:200%;

margin-left:-100%;

transition:margin0.3sease-in0s;

.onoffswitch-inner:before,.onoffswitch-inner:after{

display:block;

float:left;

width:50%;

height:30px;

padding:0;

line-height:30px;

font-size:14px;

color:white;

font-family:Trebuchet,Arial,sans-serif;

font-weight:bold;

box-sizing:border-box;

.onoffswitch-inner:before{

content:"ON";

padding-left:10px;

background-color:#34C290;

color:#FFFFFF;

.onoffswitch-inner:after{

content:"OFF";

padding-right:10px;

background-color:#EEEEEE;

color:#999999;

text-align:right;

.onoffswitch-switch{

display:block;

width:18px;

margin:6px;

background:#FFFFFF;

position:absolute;

top:0;

bottom:0;

right:56px;

border-radius:20px;

transition:all0.3sease-in0s;

.onoffswitch-checkbox:checked+.onoffswitch-label.onoffswitch-inner{

margin-left:0;

.onoffswitch-checkbox:checked+.onoffswitch-label.onoffswitch-switch{

right:0px;

.masterswitch{

position:relative;

width:90px;

-webkit-user-select:none;

-moz-user-select:none;

-ms-user-select:none;

.masterswitch-checkbox{

display:none;

.masterswitch-label{

display:block;

overflow:hidden;

cursor:pointer;

border-radius:20px;

.masterswitch-inner{

display:block;

width:200%;

margin-left:-100%;

transition:margin0.3sease-in0s;

.masterswitch-inner:before,.masterswitch-inner:after{

display:block;

float:left;

width:50%;

height:30px;

padding:0;

line-height:30px;

font-size:12px;

color:white;

font-family:Trebuchet,Arial,sans-serif;

font-weight:bold;

box-sizing:border-box;

.masterswitch-inner:before{

content:"ARMED";

padding-left:10px;

background-color:#F00000;

color:#FFFFFF;

.masterswitch-inner:after{

content:"OFF";

padding-right:10px;

background-color:#EEEEEE;

color:#999999;

text-align:right;

.masterswitch-switch{

display:block;

width:18px;

margin:6px;

background:#FFFFFF;

position:absolute;

top:0;

bottom:0;

right:56px;

border-radius:20px;

transition:all0.3sease-in0s;

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Webcontrolpanelstylesheet–alarm-panel.css

Applythestylesheetandthisiswhatyouendupwith(alittlebitnicer,Ithinkyou’llagree):

Thewebcontrolpanelwithstyling

MakingitdynamicNowthatwehavethelayoutcodedefinedforourcontrolpanelpage,wecaninsertitinourPHPpagesothatitcanbemodifieddynamicallybythePHPscriptontheWebserver,dependingonthestatusofourhomesecuritysystem.

ThePHPscriptwillhelpusachievethefollowingbasicfunctions:

Updatingtheconfigurationfilewiththepositionoftheon/offswitchesforzonesArminganddisarmingthesystemTellinguswhichzonehasbeentriggeredwhenanintrusionhasbeendetected

Again,I’mnotgoingtogointodetailabouthowthePHPcodeworks,buthopefullythecommentswithinthecodewillhelpyoufollowwhat’sgoingon,andalsohelpyoumodifyitifyouwanttochangeitsbehavior.

GettingabitofhelpfirstUnlessyouchangesomeofthePHPconfiguration,itcanbeanightmaretryingtoworkoutwhat’sgonewrongifyouhaveasmallbuginyourcode,asbasicallyyouarepresentedwith…nothing!

So,beforewecreateandbuildourPHPpage,we’llchangeacoupleofsettingsinthePHPconfigurationfiletomakesureweknowifthereareanyissues:

1. OpentheconfigurationfilewithNano:

$sudonano/etc/php5/cgi/php.ini

2. Thefileisabitlargeandunwieldy,butbattleyourwaythroughit,findthesesettings,andchangethemasfollows:

error_reporting=E_ALL

display_errors=On

3. SavethefileandexitNano.4. Finally,restartLighty:

$sudo/etc/init.d/lighttpdrestart

ThemainPHPcodeAndhereitis…Butdon’trunityet—there’sstillabitmoretodo…

YoucanfindthefullmainPHPcodeintheindex.phpfilelocatedinsidethecodefolderofchapter7.InourWebservercontentfolder,weshouldnowhavethefollowingfiles:

pi@raspberrypi~$ls-1/var/www

alarm-panel.css

alarm-panel.html

index.lighttpd.html

index.php

phpinfo.php

I’msomeoneelseNow,beforewecanactuallyopenthisPHPwebpagesuccessfully,weneedtobeawareofthefactthattheWebserver,bydefault,actuallyrunsasadifferentusercalledwww-data.Thismeansthatitdoesn’tordinarilyhavetherighttoperformcertainoperations;inparticular,thosethatinteractwiththefilesystem.

IfyouworkedthroughthepreviousPHPscript,you’llseethatitactuallyexecutessomeLinuxcommandstoreadandupdateouralarm.cfgfile.

Inthesamewaythatwehavetoputsudoinfrontofmanycommandsbecausewe’renottherootuser,itistrueforotherusersaswell,includingwww-data.So,togivetheWebserverrightstoexecutecertaincommands,weneedtoadditasasudoer,usingthevisudoutility.

Runtheutilitytoopenthesudoerconfigurationfile:

$sudovisudo

Atthebottomofthefile,addthefollowingline:

www-dataALL=(ALL)NOPASSWD:/bin/cat,/etc/pi-alarm/update-alarm-setting.sh

Thensavethefileandexit.

ThefinalthingwehavetodoiscreateasmallBashscriptthatwillhandlethetaskofupdatingsettingsinouralarm.cfgfile.Thereasonwhyweneedtodothisisbecausewe’regoingtousetheLinuxsedcommandtoupdatethefile.Thewaythatweareinvokingthesedcommandmeansthatitneedstocreateatemporaryfile.UnlesswedoabitofworkwithconfiguringtheWebserverbecauseofitsfilelocationcontext,itwon’twork.So,it’seasiertocreateastubBashscriptthatiscalledbythePHPscript.Inthisway,theBashenvironmentdealswiththetemporaryfilecontext.

So,we’llcreatethefollowingBashscriptandsaveitinour/etc/pi-alarmfolder:

#!/bin/bash

#/etc/pi-alarm/update-alarm-setting.sh

############################################

#Providesaccesstothesedcommandfrom#

#PHPasitneedswriteaccesstoatemp#

#folder.#

#$1-SettingName#

#$2-SettingValue#

############################################

sed-i"s/^$$1\s*=*$.*/\1$2/"/etc/pi-alarm/alarm.cfg

update-alarm-setting.sh

Andthenweneedtogivethescriptexecutionrights:

$sudochmod777/etc/pi-alarm/update-alarm-setting.sh

Thisiswhatweshouldseeinour/etc/pi-alarmfolderatthistime:

pi@raspberrypi~$ls-1/etc/pi-alarm

alarm.cfg

Right,afterallthat,Ithinkwecannowlaunchthecontrolpanelpageinourbrowserat

http://<my-pi-ip>.

index.phpisconfiguredasadefaultpageinLighty’sconfig,soyoudon’tneedtoaddittotheendoftheURL;justtheIPaddresswillsuffice.

BychangingtheswitchpositionsandthenclickingontheUpdateSystembutton,youshouldfindthatthesettingvaluesgetupdatedaccordinglyinalarm.cfg.Youcannowseehowthisfilewillbethewayforthestatustobeexchangedbetweenourwebconsoleandthesecuritysystemscriptsthatwe’lldevelopinChapter9,PuttingItAllTogether.

Thefinaloperationalcontrolpanel

RemoteaccesstoourcontrolpanelWhilewecansetupoursystemtoreceiveemailalertswhenoursystemdetectsanintrusion,itwouldbereallyusefultobeabletoaccessourWeb-basedcontrolpanelwhereverwearesothatwecanperhapsarmanddisarmthesystemorswitchoffcertainzoneswhenwe’renotthere.

However,inordertomakethispossibleweneedtodoafewthings:

SettingupadynamicDNSaccountMostofuswon’thaveafixedIPaddressfortheInternetconnectioninourhome;itislikelytochangefromtimetotime,especiallywhenwerebootorunplugourrouter,wherebyourInternetserviceproviderassignsusanewonewhenwenextconnecttothem.Becauseofthis,wecan’trelyonusingtheIPaddresstogettoourhomenetworkwhenwe’reoutandabout.Tosolvethis,weneedtosetupadynamicDNSaccountthatwillallowustosetupadomainnameforourhomenetwork(forexample,myhomenetwork.com).

Itworksbyhavingaservicethatrunsinsideyournetwork,suchasonyourrouterorlaptop,thatupdatesthedynamicDNSservicehostingyourdomainnamewiththecurrentIPaddressofyourInternetconnection.Then,whenyouuseyourdomainnameinyourbrowser,itwilltakeyoutoaWebserveronyourhomenetwork.

PopulardynamicDNSprovidersoutthereincludeNo-IP(www.noip.com)andDynDNS(www.dyn.com).YoucanalsogetafreeDnsOMaticaccountwithOpenDNStomanageyourservices(www.dnsomatic.com).

MyNetgearNASdevicehasaDnsOMaticupdaterserviceadd-on

MyNetgearRouterhastheoptionofupdatingaDynamicDNSservice

TheRaspberryPidynamicDNSclientSinceyourRaspberryPi-basedhomesecuritysystemislikelytoalwaysbeon,youmightwanttoinstalltheddclientupdaterserviceonthereinstead:

$sudoapt-getinstallddclient

Onceinstalled,youcansetitupforyourparticularserviceandaccountdetailsusingthefollowingconfigfile:

$sudonano/etc/ddclient.conf

SettingupastaticIPonyourRaspberryPiSothatourhomenetworkalwaysknowswheretofindyourRaspberryPi,weneedtosetupastaticIPaddressonit,assumingthatitcurrentlyacquiresanIPaddressfromyourrouter’sDHCPservereachtimeitbootsup.

1. Todothis,weneedtoeditthenetworksettingsontheRaspberryPi.InNano,openthefollowingconfigurationfile:

$sudonano/etc/network/interfaces

2. You’llprobablyfindtheEthernetportconfigurationsettosomethinglikethis:

autoeth0

allow-hotplugeth0

ifaceeth0inetmanual

3. ChangethisconfigurationtobeanunusedstaticIPaddressonyournetwork.Inmycase,I’vesetitto192.168.0.99.ThegatewaysettingistheIPaddressofmyInternetrouter:

autoeth0

allow-hotplugeth0

ifaceeth0inetstatic

address192.168.0.99

netmask255.255.255.0

gateway192.168.0.1

4. Now,weneedtorestartthenetworkingservice—notethatyou’llbedisconnectedfromyourterminalsession.You’llneedtoreconnectusingthenewIPaddress:

$sudo/etc/init.d/networkingrestart

Ifyouhaveanyissues,simplyrestartthePiwithsudorebootandallshouldbegoodwhenitcomesbackup.

Port-forwardingThefinalpieceofthispuzzleistomakesurethatourInternetrouterwilldirectincomingtrafficonagivenporttoourRaspberryPi’sWebserver.Forthepurposeofthisexample,I’mgoingtoassumethatwearegoingtosticktothedefault,port80,onourWebserver.

TipAwordaboutsecurity

GiventhatourWebserverwillnowbeaccessiblefromtheoutsideworld,weneedtobemindfulaboutsecuringoursystemproperly.ThetwomainwaystodothisaretochangetheWebserverporttoarandomnumberotherthan80(forexample,8799)andaddpasswordprotectiontoyoursitebyapplyingbasicauthentication.Bothofthesecanbedoneinthelighttpdconfigurationfile.

Mostrouterswillallowyoutosetupport-forwardingaspartoftheirfirewallconfiguration.Essentially,settingthismeansthatanyincomingtrafficfromtheInternetonagivenTCPportwillbeallowedtopassthroughtherouterandwillbedirectedtothedevicewiththespecifiedIPaddress.OnmyNetgearrouter,it’ssetupasshowninthefollowingscreenshot:

Settingupport-forwardingonaNetgearrouter

Now,whenyouenteryourpersonaldomainnameinyourbrowser,whenyou’reawayfromhomeyoushouldbetakentoyouralarmcontrolpanel.

TipYoumightalsowanttoconsideropeningupport22sothatyoucanaccesstheRaspberryPidirectlyusingPuTTyandSSHfromoutsideyournetwork.

SummaryWe’venowstartedbuildingthesoftwarethatwillcontrolourhomesecuritysystembydeterminingtheformatofthemainconfigurationfile.We’vealsoinstalledaWebserverandbuiltabasicsingle-pagecontrolpanelwithPHP,HTML5,andCSS3,whichcanbeaccessednicelyonourmobilephone,allowingustoconfigureoursystemandviewthestatus.

Inaddition,we’velearnedhowtoconfigureourhomenetworkandRaspberryPisothatwecanaccessourcontrolpanelwhenwe’reawayfromhome.

InChapter9,PuttingItAllTogether,we’llputalloftheelectronicelementstogetherandwritethemainscriptsthatwillrunthehomesecuritysystem.Butbeforethat,inthenextchapter,we’regoingtolookatafewotherbitsandpieces,suchasaddingothersensors,notnecessarilyrelatedtointruderdetection,toourhomesecuritysystem.We’llalsolookathowwecanadministerourentireRaspberryPisystemremotelyusingaWebbrowser,inadditiontoaccessingourhomesecuritycontrolpanel.

Chapter8.AMiscellanyofThingsThepreviouschaptershaveprovideduswiththefoundationandelementstodesignandputtogetherourentirehomesecuritysystem,whichwewilldointhenextchapter.IhopethatI’veguidedyouthroughthisjourneyinafairlystructuredandlogicalwaysothatyouarereadytodothat.

Beforehand,though,I’mincludingthischapterdubbedaMiscellanyofThings,asthat’sexactlywhatitis.Itcomprisesafewoptional,butuseful,extrasthatweshouldconsiderforoursystem,butthatdon’treallywarrantawholechapterintheirownright.Iguessyoucouldrefertothemasfootnotestopreviouschapters.

Assuch,wewilltakealookatthefollowingtopics:

Waystoarmanddisarmthesystemwithouttheweb-basedpanelDrivinginductiveloadssafelyfromourGPIOoutputsAddinganescapedwatersensorinputtooursystemAddingatemperaturesensorinputtooursystemHowcarbonmonoxidedetectorscouldbeaddedtooursystemRemotelymanagingourRaspberryPiusingWebmin

ArminganddisarmingthesystemWe’veincludedaswitchonourWeb-basedcontrolpanelsothatyoucanarmanddisarmthesystemfromyoursmartphone.However,thisisprobablynotthemostconvenientwayofdoingit,especiallywhenyou’rerushingoutofthehouse,oryou’vereturnedhomewithaphonewhosebatteryisflat.So,weneedtofindanadditionalwayofarminganddisarmingoursystemattheentryandexitpointofourproperty.

Inthezonelisttableinthepreviouschapter,you’llnoticethatIassignedinputGP0ontheRaspberryPiGPIOasourarm/disarmswitchinput.Thisinputwillworkinconjunctionwithourcontrolpanelswitch.

Thisinputcanasbeasimpleasatoggleswitch,orabitmoresecure,suchasakeyswitchorelectronickeypad.Eitherway,itwillbewiredtogroundGP0(GPIO17)onourRaspberryPiwhenthesystemisarmed.

Thecircuitdiagramforourarm/disarmswitch

Ifyouhaveswitchesorothersuchdevicesthatwillbeoutsideandexposedtotheelements,you’llneedtoensurethattheyaresuitableforoutdoorusesothattheydon’tgetdamagedandcompromisetheintegrityofthesystem.

TheIP67-ratedkeyswitch,suitableforoutdooruse(typeLorlinWRL-5-E-S-2-B)

Byusingastandalonesecuritykeypad,youcanalloweachusertohavetheirowncodetoarmanddisarmthesystem.Forexample,theCDVIECO100isalow-costkeypadthatallowsuptoa100users.Whenthecorrectcodeisentered,itwillarmthesystembyclosinganinternalswitch.Whenthecodeisenteredagain,thekeypadwilldisarmthesystembyopeningtheswitch.

TheCDVIECO100programmablekeypad

DrivinginductiveloadsItalkedaboutdrivinglargeloadsinChapter6,AddingCamerastoOurSecuritySystem,butnowisprobablyagoodtimetoexpandonthisabitandtalkaboutdrivinginductiveloadssuchasbellsandincandescentlamps.Inthepreviouscircuitexample,IusedtheTIP120DarlingtontransistortodriveanLEDarraythatwasnotinductive.Withinductiveloads,youneedtoaddabitofdiodeprotectiontoprotectthecircuitagainstspikesgeneratedbythecoilswithinrelaysandbellsastheyswitchonandoff.

Here’sthemodifiedcircuitforourdigitalloaddriverwitha1N4007rectifierdiodeforprotection:

Thedigitalloaddriverwithdiodeprotection

BeyondintrusionHomesecurityisnotjustaboutprotectingourpropertyagainstintrusion,it’salsoaboutprotectingagainstotherriskstoo,suchasflood,fire,carbonmonoxideleaks,andsoon.So,itmakessensetoextendourhomesecuritysystemtodetecttheseotherriskstoo.

Youmaychoosetosetupthesystemsothatcertaintypesofalertsonlycometoyourphoneasemails,ratherthantriggeringalloftheoutsidebells,lights,andwhistles.Thiscanbedonebyadaptingthescriptsinthenextchaptersothattheyoperatehowyouwantthemto.

AsimplewaterdetectorThere’snothingworsethanbeingawayforafewdaysandcominghometoafloodedkitchenbecausealeakhasdevelopedunderthesink.Oursimplecircuitwilldetectthepresenceofwaterandtriggeraninputonourhomesecuritysystem,whichcanthenalertyou.Youcanalsobuykitsandready-builtmodulestodothis,butthefollowingcircuitischeapandfeaturesouropto-isolatoraswe’regoingtohaveadifferentvoltageforouractualdetector.

Thecircuitforasimplewaterdetector,isolatedfromourGPIOinput

HowitworksWhenwaterisplacedacrosstheprobes,currentflowsthroughthewater,andso,throughtheR3/R4potentialdivideronthebaseoftransistorQ1.Whenthecurrentatthebaseishighenoughtosaturateit,thetransistorwillswitchonfully,allowingtheLEDinsidetheopto-couplertoswitchon.Thisinturnwillpulldowntheinputpintooursystemto

groundviathephoto-transistorinsidetheoptocoupler.

Youcanusethetrimmer,R4,tocalibratethesensorbyadjustingitssensitivity.AnygenericNPNbipolartransistorshouldworkhere,butobviously,theyallhavedifferentoperatingparameters,sochooseasuitableone.

AsimpletemperaturesensorIfwewanttobealertedwhentheambienttemperaturereachesacertainthreshold,thenwecanbuildacircuitusingthecommonlyusedLM34/LM35temperaturesensors.It’sasimpledevicewithjustthreepins:power,ground,andoutput,providingavoltageproportionaltothetemperature.ThedifferencebetweentheLM34andLM35isthattheLM34producesanoutputof10mV/°F,whereastheLM35produces10mV/°C.ThereisalsoanLM335variantthatproducesanoutputof100mV/°K.

PinouttakenfromtheTexasInstrumentsLM35DZdatasheet

Itmayhaveoccurredtoyouatthispointthatthisisananaloguedevice—sohowdoweinterfacethatwithourwhollydigitalsystem?Onewayistoincorporateananalogue-to-digitalinterfaceontoourinputcontrolboardandreadthedatacominginfromthatsothatweknowtheexacttemperature,butthat’sprobablyabitbeyondthescopeofthisbook.So,we’regoingtoimplementacircuitthatwillalertuswhenthetemperatureexceedsapre-definedthreshold,whichisprobablyallweneedinthecontextofourhomesecuritysystem.

NoteIfyou’reinterestedinbuildingananalogue-to-digitalmoduletoextendyourhomesecurity,thentakealookatsomethingsuchasthePCF8591chipfromNXP,whichisanI2C-basedanalogue-to-digitalconverter.ThiswillconnecttotheI2Cbusthatwe’realreadyusing,andsoitiseffectivelyjustanadd-on.

http://bit.ly/NXPPCF8591T

Forourtemperaturedetectorcircuit,wewilluseanoperationalamplifierconfiguredasacomparatorthatwilltriggerouropto-couplerinputwhenthepre-settemperatureisreached.So,forfiredetection,wemightwanttodetectwhentheambienttemperaturehasexceeded50°C.

Thetemperaturethresholdsensortodriveourdigitalinput

HowitworksThereferencevoltageissetbythevariableresistor,R4,whichformsavoltagedividerbetweenthe12Vandtheground.Thisessentiallymeansthatthereferencevoltageonthe+veinputoftheop-ampcomparatorcanbebetween0and12V.Assumingthatwewanttodetectwhen50°isreached,wewillneedtheop-amptotriggerwhenthe–veis500mV(10mV/°C).

Inourcircuit,theoutputoftheop-ampishighinitsnormalstate,whichkeepstheopto-coupleron.However,whenthethresholdisreached,theoutputoftheop-ampisdrivenlow,switchingoffthetransistorQ1,andhence,theopto-coupler.ThispullsouralarminputhighviaresistorR2.

AcarbonmonoxidedetectorIt’sentirelypossibletobuildsmokeandcarbon-monoxidedetectorsthatwecanconnecttoourhomesecuritysysteminasimilarwaytotheprevioussensors,althoughtheyarealittlebitmorecomplexastheycanrequirespecialhandling.TheSparkFunMQ-7CarbonMonoxide(CO)detector(whichisactuallymadebyWinsenElectronics)canbeimplementedinasimilarwaytoourtemperaturesensor,triggeringanalarminputwhenaparticularthresholdisreached.

TheWinsenMQ-7carbonmonoxidegasdetector,availablefromSparkFun.

NoteThemaximumsafecontinuousexposuretocarbonmonoxide(CO)is9ppm(parts-per-million)accordingtoASHRAE(www.ashrae.org),andyoushouldcertainlynotbeexposedtoCOhigherthanthisforprolongedperiodsoftime,with35ppmbeingtheabsolutemaximumforanormal8-hourworkingday.

TheMQ-7detectorhasasensitivityofbetween10and500ppm,soinmymind,I’dwant

tobealertedassoonasitpicksupanything,thereforeweshouldsetourcomparator’sreferencevoltagetothelowerendofthescale,inaccordancewiththesensitivitycurvetakenfromthedatasheet,shownasfollows:

ThesensitivitycurvetakenfromtheWinsenMQ-7manufacturer’sdatasheet.

NoteWarning

I’veincludedthissectiononcarbonmonoxidedetectionmoreforinterestthananythingelse.It’snastystuff,andwhilerollingoutyourowndetectorisOKforinterest’ssake,pleasekeepitjustforthat.It’susefultohavethisinourhomesecuritysystemtoalertuswhenwe’reoutofthehouseasanaddition,butthisshouldnotbeareplacementforacommerciallyavailableonethatsitsnexttoyourboilerwithallofthecertifications,standards,andsoon,andmakesaveryloudnoisewhenwe’reinthehouse.

RemoteadministrationforourRaspberryPiInthepreviouschapter,welearnedhowtosetupoursystemandhomenetworksothatwecanremotelyaccessthealarmcontrolpanelfromwhereverweare.I’mnowgoingtoshowyouhowtoextendthistobeabletoadministerandmonitorourentireRaspberryPisystem.

GettingWebminWebminisaratherfineandwellestablishedweb-basedinterfaceforadministeringUnix/Linuxsystems.YoucanfindeverythingaboutWebminonitswebsiteatwww.webmin.com.I’massuming,asthroughoutthisbook,thatyouareusingtheRaspbiandistributiononourPiwhenitcomestoinstallingWebmin.

ThereareacoupleofwaystoinstallWebmin:eitherbymanuallydownloadingandunpackingit,orbyupdatingourrepositorysourcessothatwecanuseapt-get.I’mgoingtooptforthelatter,soanydependenciesareautomaticallyinstalledandupdatescanbemanagedmoreeasilyinthefuture.Thereareafewsteps,butit’sprettystraightforward:

Updatingtherepositorysources1. ThefirstthingweneedtodoisupdateourrepositorysourcestoincludetheWebmin

repositories:

$sudonano/etc/apt/sources.list

2. Addthefollowingtwolinestotheendofthefile:

debhttp://download.webmin.com/download/repositorysargecontrib

debhttp://webmin.mirror.somersettechsolutions.co.uk/repositorysarge

contrib

3. SaveandexitNano.

Importingthesigningkey1. Next,weneedtodownloadandimporttherepository’ssigningkey:

$sudowgethttp://www.webmin.com/jcameron-key.asc

$sudoapt-keyaddjcameron-key.asc

2. Nowthatwehaveeverythingweneed,wecanupdatethepackageinstallerandinstallWebmin.Itcantakeawhile,soyoumightwanttogoandmakeyourselfacupofteaorcoffee:

$sudoapt-getupdate

$sudoapt-getinstallwebmin

3. Onceit’sinstalled,youshouldseethefollowingmessageintheshellwindow:

Webmininstallation

AccessingWebminlocallyWebmin,bydefault,runsonport10000andusesthesecureHTTPSprotocol;so,toaccessit,youneedtoenterthefollowingURLinyourbrowser:https://<my-ip>:10000

Where<my-ip>istheIPaddressofyourRaspberryPi.

Inthepreviouschapter,wesetupastaticIPaddressonoursystem;inmycase,Isetuptheaddressas192.168.0.99.So,toaccessWebminonmysystem,Iwoulduse:https://192.168.0.99:10000

NoteHTTPSPrivacyErrors

Insomebrowsers,suchasGoogleChrome,youmightseeaprivacyerrorasyoutrytoaccesstheWebminWebpage.ThisisbecausetheSSLcertificatebehindtheHTTPSconnectionisnotsignedbyaknownauthority.Thisisfine—justtellyourbrowserthatyouwanttoacceptthisandproceed(inChrome,youneedtoclickontheAdvancedlinkfirsttoaccessthatoption).

YoucanlogintoWebminusingtherootorpiuseraccount,oranyotheraccountthathassudorights:

Webminlogin

Onceloggedin,you’llbepresentedwiththemainsysteminformationpage.Haveagoodpokearoundinitbecausethere’slotsofusefulstuffyoucanseeanddo.

Webminsysteminformationview

Webmincomeswithalotofmodules,andnotallofthemareinstalled;therefore,youmightwanttoexploretheUn-usedModulessectionofthepaneltoseeifthereisanythingyouwanttoaddtoWebmin.

RemotelyaccessingWebminInthesamewaythatwesetupremoteaccessforouralarmcontrolpanelinthepreviouschapter,youcandoitwithWebmin—justsetupport-forwardingonyourrouterforport10000.YoucanthenaccessWebminfromanywhereusinghttps://<my-public-ip>:10000.

SummaryWell,thishasbeenabitofamix-and-matchofvarioustopicstoendonbeforeweputtogetherourhomesecuritysystemframework.Ihopeyouenjoyedthesevariousfootnotestopreviouschapters,andthatit’sgivenyousomeideasonhowfaryoucantakeyourhomesecuritysystem.

WestartedbylookingatwayswecanarmanddisarmoursystemwithouthavingtoaccesstheWeb-basedcontrolpanel,byaddingamechanicalordigitalswitchtoanarm/disarminput.

Wethenlookedataddinganalogue-typesensorstooursystem,whichcanalertuswhenathresholdhasbeenreachedbyusingoperationalamplifierssetupasvoltagecomparators.Theideabehindthesecomparatorcircuitscanbeimplementedfordifferenttypesofsensorswhereyouwanttoknowwhenacertainvoltagethresholdhasbeenreachedattheanaloguesensoroutput.

Finally,welearnedhowtoinstallWebminonourRaspberryPisothatwecanmonitorandconfiguremanyaspectsoftheLinuxoperatingsystem.

Thenextchapteristhemomentwe’veallbeenwaitingfor;we’regoingtotakealloftheelementsandconceptsfromthepreviouschaptersandputtogetherourfullsystemcomprisingtheelementswewanttofeature.ThestaroftheshowwillbeourBashscripts,whichwillgluetogetheralloftheseelementsandprovidethecontrollogicfortheentiresystem.

Chapter9.PuttingItAllTogetherOverthepasteightchapters,we’veexploredtheelementsandconceptsofafull-featuredhomesecuritysystemthatyou’dexpecttohaveinstalledinyourproperty.It’sbeenpresentedinamodularfashionsothatyoucanchoosewhichfeaturesyouwantforyoursystem,toallowyoutomakeitascompactandbasicorlargeandcomplexasyourequire.

Fundamentally,theideabehindahomesecuritysystemistodetectwhetherparticularzoneinputsaretriggeredhighorlowbyanexternalsensor,bethataswitch,motiondetector,orwaterdetector.Attheendoftheday,asfarasthecontrolsoftwareisconcerned,thetypeofsensorisirrelevantandthesystemsoftware’sjobistosimplycheckthestateofitsinputsandalertaccordingly.

Inthisfinalchapter,we’regoingtoputalloftheconceptstogethertocomeupwithasecuritysystemframeworkandwritethecontrolscriptsaroundit.Thisiswhatwewillcover:

Definingahigh-leveloverviewofoursystem,detailingtheconnectedelementsBuildingtheentiremodularsecuritysystemframeworkcontrolscript,exploringthecodeindetailDelvingintosomedetailedshellscriptingtechniquestoperformcertaintasksLearninghowtomakeoursystemautomaticallystartatboot-timePreventingtheburningoutofourSDcardbycreatingaRAM-basedfilesystem

AlarmsystemdiagramSothatwedon’tgetlostinthisprocess,thefirstthingIrecommendistocomeupwithacompletesystemdiagramthatwecanfollow.IdothisforanysystemIdesignandputtogethersothatitcanbebuiltinastructuredway,andeasilydocumentedandmodified.

Forthehomesecuritysysteminthischapter,Ihavecomeupwiththefollowingsystemdiagramthatwewilllooktoasaframework.Thewholeconceptisdesignedtobemodular,soyoucancomeupwithyourownsystemtosuityourrequirementsandimplementitaccordingly,usingthescriptspresentedinthischapter.

Thefinalhomesecuritysystemdiagram

OverviewofthesystemelementsTheprecedingsystemdiagramcomprisestheelementsandmodulesthatwehavediscussedinpreviouschapters.Here’saquickrecapofthese:

A+12VpowersupplyThisistheprimarypowersupplytooursystem,whichwewillobtainfromanexternalmainsadapterthatcouldbebattery-backed.Thissupplyneedstobesmoothandregulatedtoensurethatitremainsstableforthesystemascurrentlydrawn.

Allofthealarmwiringandsensorswillbesuppliedwiththispower,aswillperipheralssuchassoundersandbells,whichusuallyoperatefroma12Vsupply.Chapter5,AddingaPassiveInfraredMotionSensordiscussedthemeritsofusinga12Vsupplyforthealarmcircuits.

A+3.3VpowersupplyThissupplyisaregulated+3.3Vsupplyforthedigitalportexpandercircuit;italsoprovidesthelogicalalarmzoneinputsviaanopto-coupler.The+3.3Vpowersupplycanbederivedfromeitherthe+12Vsupply(recommended),orthe+5VsupplyfromtheRaspberryPi’sGPIOconnector,usingavoltageregulatorchosenaccordingtohowmuchcurrentyouneed.

Chapter3,ExtendingYourPitoConnectMoreThings,showedyouhowtobuilda+3.3Vregulatedsupply.

Theopto-isolatorinputmoduleThiswillisolatethe+12VzoneinputpowerlinesfromtheportexpanderandGPIOdigitalinputs,whichshouldonlyhaveamaximumof+3.3Vpresentedtothemwhentriggeredhigh.

Thecircuitfortheseopto-isolatedinputmoduleswasdiscussedandshowninChapter5,AddingaPassiveInfraredMotionSensor.

TheportexpanderTheportexpanderisourmaindigitalinput/outputsystemthatwilltakethealarmzoneinputsandtransmitthemtotheRaspberryPiusingtheI2Cbus,orallowtheRaspberryPitoswitchoutputsonandoff.

WebuiltourMCP23017-basedportexpandercircuitinChapter3,ExtendingYourPitoConnectMoreThingsandconfiguredthesoftwareforitinChapter4,AddingaMagneticContactSensor.

Anarm/disarmswitchThearm/disarminputoverridesthearm/disarmsoft-switchfunctiononourweb-basedcontrolpanel,andisaswitch(key,digitalkeypad,orotherwise)connectedtoGP0directlyontheRaspberryPi’sGPIOconnector.

RemembertoconnectanyswitchcircuitappropriatelytotheGPIOpintoavoiddamagetoyourRaspberryPi.ThiswasdiscussedinChapter2,ConnectingThingstoYourPiwithGPIO.

AlarmoutputsInoursystem,wehaveseveraloutputdevicesthatarecontrolledbyourRaspberryPiviaoutputdrivercircuits.Wehaveanoutputforanentry/exitbuzzer,anarmedstatusLED,analarmbell,andanalarmLEDindicator.

TheseareswitchedonandoffbyourRaspberryPiGPIOconnectorviadrivercircuitsthatallowustodrivehighcurrentandinductiveloadsusingtheGPIOpins.Thesedrivercircuits,basedaroundTIP120Darlingtontransistors,werediscussedinChapter6,AddingCamerastoOurSecuritySystemandChapter8,AMiscellanyofThings.

DesigningthecontrolscriptsBeforewestartwritingthescriptstocontrolouralarmsystems,itisprobablyagoodideatooutlinethehigh-levelprocessforthesystem.Thefollowingflow-charthelpsuspicturehowoursystemshouldwork,andthevariouslogicaldecisionsourscriptneedstomake.

Theflowchartmightlookabitcomplicatedwithallitslinesindifferentdirections,butit’sactuallyprettylinearandinadownwarddirection.Referringtotheflowchart,itshowsthefollowingtasksthatthecontrolscriptwillbedoing:

Sittingquietlyuntilthesystemisarmedeitherbythehardwarekeyswitchortheweb-basedpanel’ssoftswitch.Whenthesystemisfirstarmed,itwillsoundtheexitbuzzerforapre-determinedamountoftimebeforeactuallyarmingthesystem.Thisgivesyouachancetoleavethepropertyordisarmthesystemagain,beforeitstartsmonitoringtheinputs.Oncethesystemisarmed,thearmedLEDwillbeswitchedonandthesystemwillwaittoseeifanyofthealarmzoneinputsaretriggered.Itwillalsowaittoseeifthealarmisdisarmedonyourreturntotheproperty.Wecanoptionallyputanentrytimerinhereontheentryzonetodelaybeforetriggeringthealarm.Ifthealarmisultimatelytriggered,thenthemainalarmbellwillbeswitchedon,aswellastheexitbuzzer.Themainbellshouldonlysoundforawhile,dependingonenvironmentalrestrictionsinyourneighborhood,andso,thiswillbeswitchedoffafterapre-definedperiod,buttheinternalbuzzerwillstayon.Whentriggered,thesystemwillthenwaitforyoutodisarmit,beforeresettingit.

Thecontrolscriptflowchart

BuildingthecontrolscriptNowthatwehavedesignedoursystemthewaywewantittowork,wecanstartwritingourBashcontrolscript.Asbefore,we’lllocateourscriptsinthefolder,/etc/pi-alarm,which,you’llrememberfromChapter7,BuildingaWeb-BasedControlPanel,isalsowhereourWeb-basedcontrolpanelwritesitsconfigurationstatusfile,alarm.cfgto.We’llbereferringtothatfileinourscriptstoo.

Inthisscript,wearegoingtousethebctool(theBashcommand-linecalculator)toconverthexvaluestobinary.It’snotinstalledbydefault,soyou’llneedtogetthepackage:

$sudoapt-getupdate

$sudoapt-getinstallbc

TipOurscriptfileisquitelongso,asbefore,youmightwanttositonthesofaandwriteitonyourlaptopusingsomethingsuchasNotepad++.Remember,however,ifyou’reusingaPC,ensurethattheend-of-line(EOL)formatisconvertedtotheUnixformat,otherwisetheBashscriptwon’trunonthePiwhenyoucopyitacross.Notepad++willdothisforyou.

ExploringthescriptcodeI’mnowgoingtowalkyouthroughthevarioussectionsofthecontrolscriptcodeI’vewritten,whichwillbeusedasaframeworkforoursystem.Isay“framework”because,whileitwillprovideyouwithafullyfunctionalcontrolscriptforthesystem,itcanbemodifiedandextendedtosuityourparticularrequirements.

Thefollowingcodelistingsareallpartofthesinglebashscript,alarm-control.sh,thatcanbedownloadedinfullwithcommentsfromthePacktPublishingwebsite.

DeclarationsWe’llstartoffbysettingupthevariouscontrolvariablesneededtotrackthesystem’sstate:

#!/bin/bash

#/etc/pi-alarm/alarm-control.sh

ALM_BELL_DURATION=600#durationinsecondsthealarmbellshouldsound

ALM_EXIT_DELAY=30#entry/exitzonedelayinseconds

ALM_KEY_ARMED=0#statusofthearm/disarmkeyswitch

ALM_SYS_ARMED=0#armedstatusofthesystem

ALM_ZONE_INPUT_READ=""#thiswillstorethevalueofthezoneinputs

ALM_ZONE_INPUT_STAT="00000000"#binaryrepresentationoftheinputs(b7-

ALM_ZONE_INPUT_PREV=""#previouszoneinputstatus

ALM_ZONE_TRIGGER=0#thiswillbesetto1ifoneormorezonesis

triggered

ALM_ZONES_STAT=(00000000)#dynamicarrayofnormalisedzone

status(z1toz8order)-1istriggered

STAT_RET_VAL=""#returnvaluefromfunctions

BecausewecouldfacethesituationwherebyaHIGHoraLOWinputcouldrepresentatriggeredzone,dependingonitsconfigurationandwiring,Ihaveintroducedanarrayofnormalizedstatusflagsinthevariable,ALM_ZONES_STAT,whichwillbethedefinitivestateasfarasthescriptisconcerned.We’lllookatthefunctionthatdealswiththislater.

UpdatingconfigsettingsInChapter7,BuildingaWeb-BasedControlPanel,weintroducedtheconfigurationfile,alarm.cfg,whichstoresthesystemstatusandconfigurationforthebenefitoftheWeb-basedcontrolpanel.Thisfilenotonlyneedstobereadbythemaincontrolscripttogetanysettingsmadeusingthecontrolpanel,butalsoneedstobeupdatedwithstatusvaluesfromthemaincontrolscriptsothattheycanbepresentedbacktothecontrolpanel,essentiallyexchangingdatabetweenthetwosub-systems.

Therefore,we’regoingtoincludeahelperfunctionthatcontainsthesamecodecalledbytheWebpagePHPscripttoupdatethisfilefromthecontrolpanel:

#Thishelperfunctionwillupdatethealarmconfig

#filewiththespecifiedvalue(alarm.cfg)sothat

#theWebpanelcanknowthelateststatus

functionalmUpdateConfigSetting()

#$1-SettingName

#$2-SettingValue

sudosed-i"s/^$$1\s*=*$.*/\1$2/"/etc/pi-alarm/alarm.cfg

SettinguptheGPIOWenowneedtosetuptheRaspberryPi’sGPIOpinsforourpurposes,asoutlinedbytheearliersystemdiagram.ThefollowingcommandswerefirstdiscussedinChapter2,ConnectingThingstoYourPiwithGPIO:

#GPIOSETUP###################################

#SetuptheRaspberryPiGPIOpins

#RefertoChapter2forinfo

#D0(GPIO17)Arm/DisarmKeyInput

#D4(GPIO23)ArmedLEDOutput

#D5(GPIO24)ExitBuzzerOutput

#D6(GPIO25)AlarmLEDOutput

#D7(GPIO4)AlarmBellOutput

NoteNotethatyoucanonlyexportaGPIOpinonce,unlessithasbeensubsequentlyunexported.Therefore,youmightseetheerror,echo:writeerror:Deviceorresourcebusy,ifyoure-runthescriptwhenittriestoexportthepinagain.Youcansafelyignorethis.

We’llalsothrowinafewhelperfunctionsthatwilleasilyallowustoswitchonoroffvariousoutputstosimplifythemaincode.I’mabigfanofimplementingfunctions,howeversimple,astheykeepthecodemodular,reusable,andsimplertoreadinmostcases:

#ThishelperfunctionwillswitchaspecifiedGPIOoutputonoroff

functionalmSetGPIOValue()

#$1-GPIOpinnumber

#$2-Value

sudoecho$2>/sys/class/gpio/gpio$1/value

#Helperfunctionstoswitchonandofftheoutputs

functionalmSetArmedLED()

#$1-0or1(OfforOn)

almSetGPIOValue23$1

echo"[ALM]ArmedLEDsetto$1"

functionalmSetExitBuzzer()

#$1-0or1(OfforOn)

almSetGPIOValue24$1

echo"[ALM]ExitBuzzersetto$1"

functionalmSetAlarmLED()

#$1-0or1(OfforOn)

almSetGPIOValue25$1

echo"[ALM]AlarmTriggerLEDsetto$1"

functionalmSetAlarmBell()

#$1-0or1(OfforOn)

almSetGPIOValue4$1

echo"[ALM]AlarmBellsetto$1"

And,we’lladdahelperfunctionthatwillreadtheARMswitchstatusfromtheD0(GPIO17)oftheRaspberryPiandfromtheweb-consoletoseeiftheARMsoftswitchhasbeenset:

#thisfunctionreturnswhetherthesystemisarmedvia

#eitherthewebconsoleorkeyswitch

functionalmGetArmedSwitchStatus()

STAT_RET_VAL="0"

#readarmkeyswitchinputfrom

localL_VAL=$(sudocat/sys/class/gpio/gpio17/value)

if[$L_VAL-eq1];then

#systemhasbeenarmedwithkeyswitch

echo"[ALM]SystemARMEDwithkeyswitch"

ALM_KEY_ARMED=1

almUpdateConfigSetting"SYSTEM_ARMED""1"#setsystemarmedconsole

STAT_RET_VAL="1"

#readsystemarmedvaluefromwebconsoleconfigfile

if[$SYSTEM_ARMED==1];then

echo"[ALM]SystemARMEDwithwebconsole"

STAT_RET_VAL="1"

SettinguptheI2CportexpanderThenextfewlinesofcodesetuptheI2Cportexpandertosetallofthepins,onbothPortAandPortB,asinputs.Inoursystemhere,we’reonlyusingPortA,butthisallowsustohaveanother8inputsifwewanttoexpandoursystem.WeoriginallylookedatthisinChapter4,AddingaMagneticContactSensor:

#PORTEXPANDERSETUP##########################

#RefertoChapter4formoreinformationabouttheI2Cbus

#WewillsetupI/OBUSAasallinputs

sudoi2cset-y10x200x000xFF

#Whilstwe'renotusingBUSBinoursystem,

#wecansetthatupasallinputstoo

sudoi2cset-y10x200x010xFF

NoteIfyoudon’thaveyourI2Cportexpanderattached,thenyou’llseethefollowingerrorwhenyoutrytorunthesecommands:Error:Writefailed

DecodingthezoneinputsstatusThenextfunctionisabigone—andkeytooursystem.ItwillreadthePortAvaluefromtheI2Cportexpander.It’llbereturnedasahexadecimalvalue,soweneedtoconvertthistoabinaryvaluewitha0or1flagrepresentingeachinputbit.We’llusethebctoolinstalledearliertodothis.

Oncewehavethestatusofeachinputbit,wethennormalizethestatusbydeterminingwhethera0ora1determinesapositivetrigger.Theresultingoutputisthearray,ALM_ZONES_STAT,whichcontainsthestatusofeachzone—witha1representingapositivetriggeredzonede-facto:

#Thisfunctionwillreadtheportinputsandsetthe

#statusofeachzone

functionalmReadZoneInputs()

#preservepreviouszonestatus

ALM_ZONE_INPUT_PREV=$ALM_ZONE_INPUT_STAT

#readthe8-bithexvalueofporta

ALM_ZONE_INPUT_READ=$(sudoi2cget-y10x200x12)

if[[$ALM_ZONE_INPUT_READ=*"Error"*]];then

#AnerroroccurredreadingtheI2Cbus-setdefaultvalue

ALM_ZONE_INPUT_READ="0x00"

#removethe0xatthestartofthevaluetogetthehexvalue

localL_HEX=${ALM_ZONE_INPUT_READ:2}

#convertthehexvaluetobinary

localL_BIN=$(echo"obase=2;ibase=16;$L_HEX"|bc)

#zeropadthebinarytorepresentall8bits(b7-b0)

ALM_ZONE_INPUT_STAT=$(printf"%08d"$L_BIN)

echo"[ALM]ZoneI/OStatus:$ALM_ZONE_INPUT_STAT($ALM_ZONE_INPUT_READ)"

#checkeachzoneinputtoseeifit'sinatriggeredstate

#atriggeredstatemaybeeither1or0dependingontheinput's

configuration

#you'llneedtosetthelogichereaccordinglyforeachinput

#theALM_ZONES_STATarraycontainsthedefinitivetriggervalueforeach

#zone1test(bit0)

localL_FLG=${ALM_ZONE_INPUT_STAT:7:1}

if[$L_FLG-eq0];thenALM_ZONES_STAT[0]=0;elseALM_ZONES_STAT[0]=1;

#zone2test(bit1)

#zone3test(bit2)

#zone4test(bit3)

#zone5test(bit4)

#zone6test(bit5)

#zone7test(bit6)

#zone8test(bit7)

echo"[ALM]ZoneTriggerStatus:$ALM_ZONES_STAT[*]"

Initialization

Nowthatwehavedeclaredourmodule-levelvariablesandhelperfunctions,wewillstartourmainroutine.First,we’llinitializethesystemthatclearstheSYSTEM_ARMEDstatusandreadsintheinitialsettingsfromtheconfigfile:

#initialisesystem#########

echo"[ALM]Initialisingsystem…"

almUpdateConfigSetting"SYSTEM_ARMED""0"#clearsystemarmedconsoleflag

sleep1

sudocat/etc/pi-alarm/alarm.cfg

sleep1

echo"[ALM]Initialisingdone"

#############################

ThesystemmonitoringloopThescriptthenjumpsintoanever-endingloopthatwillbethemaincontrolsystem,monitoringthearm/disarmstatusand,whenarmed,monitoringthezoneinputstatusandrespondingaccordingly:

#loopcontinuously###########

whiletrue

#waitforsystemtobearmed###############

echo"[ALM]AlarmnowinSTAND-BYstate-waitingtobearmed"

almSetArmedLED0#switchoffarmedLED

STAT_RET_VAL="0"

while[[$STAT_RET_VAL="0"]];do

sleep1

#readthecontrolpanelstatusfile

./etc/pi-alarm/alarm.cfg

almGetArmedSwitchStatus#resultisreturnedinSTAT_RET_VAL

echo-n"*"#indicatestandbymode

#############################################

ArmingthesystemWhenthesystemgoesintotheARMEDstate,itwillfirstswitchontheexitbuzzerandthenwaitforapre-determinedamountoftime.Thiswillgiveyoutimetoleavethepropertyordisarmthesystem:

#performexitdelay########################

echo"[ALM]AlarmnowinEXITDELAYstate"

almSetExitBuzzer1#switchonexitbuzzer

COUNTER=$ALM_EXIT_DELAY

while[[$STAT_RET_VAL="1"&&$COUNTER-gt0]];do

sleep1

COUNTER-=1

echo-n"X$COUNTER"#indicateexitmode

almSetExitBuzzer0#switchoffexitbuzzer

#############################################

#systemnowarmed-monitorinputs#########

ALM_SYS_ARMED=1

echo"[ALM]AlarmnowinARMEDstate"

almSetArmedLED1#switchonarmedLED

almReadZoneInputs#>ALM_ZONES_STAT[x]

MonitoringthezonesOncearmed,thesystemwillmonitorthezoneinputsinacontinuousloopuntileitherthesystemisdisarmed,orazoneinputistriggered.Whenazoneistriggered,itwillcheckagainsttheZONE_ENABLE_nconfigurationtoseeifthatzonehasbeendisabled(thisisdoneintheWeb-basedcontrolpanel).Ifthezoneisnotdisabled,thenthealarmsystemisdeemedtriggered.

TheZONE_STATUS_nsettingisalsoupdatedheresothattheweb-basedcontrolpanelindicateswhichzoneorzoneshavebeentriggered:

#checkeachzoneinputtosetifit'senable

#andhasbeentriggered

#NUM_ZONESsettingisstoredinalarm.cfg

while[[$ALM_SYS_ARMED-eq1]];do

echo-n"A"#indicatearmedmode

ALM_ZONE_TRIGGER=0

for((i=$NUM_ZONES;i>0;i--));do

if[[$ALM_ZONES_STAT[$i-1]-eq1]];then

#zonehasbeentriggered

echo"[ALM]Zone$iTRIGGERED"

E_VAR="ZONE_ENABLE_$i"

E_VAL=`echo"$E_VAR"`#getzoneenabledstatusloadedfrom

alarm.cfg

if[[$E_VAL-eq1]];then

#zoneisenabled

ALM_ZONE_TRIGGER=1#setalarmtriggeredflag

echo"[ALM]Zone$iENABLED-alarmwillbetriggered"

almUpdateConfigSetting"ZONE_STATUS_$i""1"

##YOUCANINSERTCODEHERETOTAKECAMERAIMAGEIFYOUWANT##

##REFERBACKTOCHAPTER6##

Entrydelay

Whenanalarmzoneistriggered,itwillfirstcheckwhetheritwastheentry/exitzonethatwastriggered.Ifitwas,thenthesystemwilldelaybeforesoundingthemainalarmtogiveyouachancetodisarmthesystem.Onlytheentrybuzzerwillsoundatthistime:

if[[$ALM_ZONE_TRIGGER-eq1]];then

#alarmhasbeentriggered

almSetAlarmLED1

echo"[ALM]Azonehasbeentriggered"

#####################################

#ZONE1istheENTRYzone-ifthat'striggeredthendelay

if[[$ALM_ZONES_STAT[0]-eq1]];then

#performentrydelay###########

echo"[ALM]AlarmnowinENTRYstate"

setExitBuzzer1#switchonentry/exitbuzzer

COUNTER=$ALM_EXIT_DELAY

STAT_RET_VAL="0"

while[[$STAT_RET_VAL="1"&&$COUNTER-gt0]];do

echo-n"E$COUNTER"#indicateentrymode

sleep1

COUNTER-=1

#####################################

SoundingthemainalarmIf,atthispoint,thesystemhasn’tbeendisarmed,thenweneedtosoundthemainbell.Wehaveadurationlimitforsoundingthebelltocatertoenvironmentalnoiserestrictions;wewouldn’twantthealarmsoundingforhours,annoyingtheneighborsuntilwegothome.Atthispoint,youcanalsoaddcodefromChapter6,AddingCamerastoOurSecuritySystem,ifyouwanttobesentanalertemailtoyourmobiledevice:

#####################################

#STAYinTRIGGEREDmodeuntilsystemhasbeendisarmed

if[[$STAT_RET_VAL="1"]];then

#alarmhasnotbeendisabled

almSetAlarmBell1#switchonalarmbell

echo"[ALM]AlarmnowinTRIGGEREDstate"

##YOUCANINSERTCODEHERETOSENDYOUANEMAILIFYOUWANT##

##REFERBACKTOCHAPTER6##

COUNTER=0

STAT_RET_VAL="0"

while[[$STAT_RET_VAL="1"]];do

echo-n"T$COUNTER"#indicatetriggeredmode

sleep1

COUNTER+=1

if[[$COUNTER-gt$ALM_BELL_DURATION]];then

almSetAlarmBell0#switchoffalarmbell

echo"[ALM]BellhasbeenswitchedOFF"

#####################################

DisarmingandresettingthesystemWhenwedisarmthesystem,weneedtoresetitsstatusandcompletethemonitoringloopsothatwecanstartalloveragainandwaitforittobere-armed:

#alarmhasbeendisarmed##########

echo"[ALM]AlarmhasbeenDISARMED"

ALM_SYS_ARMED=0

almSetAlarmBell0#switchoffalarmbell

almSetExitBuzzer0#switchoffexitbuzzer

almSetAlarmLED0

almSetArmedLED0#switchoffarmedLED

#####################################

#############################################

We’redone(almost)…Andtherewehaveit:aframeworkforanentirealarmcontrolscriptonourRaspberryPi.Additionalfeaturesthatyoumaywanttoimplementwithinyourscriptcouldincludethefollowing:

Sendingaphotoorvideoclipfromazone’scamerawhenit’striggeredSendinganemailalertwithstatusdetailswhenthealarmhasbeentriggeredWritingaregularlogfilerecordinghistoricalstatusinformationAddingadditionalenvironmentalsensorstoportB

TipEachofthescriptblocksistakenfromthesinglescriptfile,alarm-control.sh,soyoushouldbeabletoputallofthedescribedpiecestogetherintoonefiletohaveafullyfunctionalscript.

Asalways,beforewecanrunitweneedtogivethescriptexecuterights:

$sudochmod777/etc/pi-alarm/alarm-control.sh

AfterwecopythescripttoourRaspberryPi,thisiswhatweshouldseeinour/etc/pi-alarmfolder:

pi@raspberrypi~$ls-1/etc/pi-alarm

alarm.cfg

alarm-control.sh

AutomaticallystartingthesystemNow,obviously,wedon’twanttohavetomanuallystartthealarmcontrolscripteachtimetheRaspberryPibootsup,forexample,afterapowerfailure—forastart,wemaynotevenbethere.Therefore,weneedtosetupouroperatingsystemsothatitwillautomaticallystartupthealarm-control.shscriptatboottime.

Todothis,weneedtoedittherc.localfileusingNano:

$sudonano/etc/rc.local

Beforethelinecontainingexit0,insertthefollowingline:

sudo/etc/pi-alarm/alarm-control.sh&

NoteThe&symbolattheendofthelineisimportantbecauseitwillthenmakethescriptruninadifferentprocess,otherwisetherc.localscriptwouldneverexit.

Yourrc.localfileshouldnowlooksomethinglikethis:

#!/bin/sh-e

#rc.local

#Thisscriptisexecutedattheendofeachmultiuserrunlevel.

#Makesurethatthescriptwill"exit0"onsuccessoranyother

#valueonerror.

#Inordertoenableordisablethisscriptjustchangetheexecution

#bits.

#Bydefaultthisscriptdoesnothing.

#PrinttheIPaddress

_IP=$(hostname-I)||true

if["$_IP"];then

printf"MyIPaddressis%s\n""$_IP"

sudo/etc/pi-alarm/alarm-control.sh&

Theoperatingsystemrunstherc.localscriptafterthesystembootsup,soyoucanputanythingintherethatyouwanttohappenautomaticallyatthistime.

PreservingtheSDcardOnefinaltopicIwanttosharewithyouisthatofpreservingyourRaspberryPi’sSDcard.SDcardshaveafinitewritecycle,andcontinuouswritingtothecardwilleventuallyburnitout.Ifwe’regoingtobewritinglotsoflogfileentriesandtakinglotsofcameraimages,wewillwanttoprotectourSDcardinordertomaintaintheintegrityandreliabilityofoursystem;usingthesystemRAMinsteadcanhelpuswiththis.

CreatingaRAM-basedfilesystemOurRaspberryPihasplentyoffastsystemRAMavailabletous(1Gbonthelatestmodels)thatisn’tsusceptibletothiswriteburn-outissue.Therefore,I’mgoingtoshowyouhowtoallocatesomeofittocreateatemporarydiskinmemory,whichwecanwritefilestothatwedon’tneedkeptontheSDcard.Suchfileswouldincludethe,quitelarge,cameraimagefilesthatwillbeemailedoutofthesystem—which,therefore,don’tneedtobestoredpermanently.Youshouldalsoconsideranylogfilesthatareregularlywrittento,whichwouldthenbeshippedoffthesystematregularintervals.

NoteRememberthatthisisaRAM-basedfilesystem,socontentwillbelostwhentheRaspberryPishutsdownorreboots.So,don’tstoreanydataherethatyouwanttopersistafterarestart.

Let’screateaBashscriptfilecalledsetup-ramfs.sh,andcopyittoour/etc/pi-alarmfolder:

#!/bin/bash

#/etc/pi-alarm/setup-ramfs.sh

RAM_DISK="/ramfs"

RAM_DISK_SIZE=64M

#CreateRAMDisk##########################

if[!-z"$RAM_DISK"];then

echo"[INIT]CreatingRAMDisk…$RAM_DISK"

mkdir-p$RAM_DISK

chmod777$RAM_DISK

mount-ttmpfs-osize=$RAM_DISK_SIZEtmpts$RAM_DISK/

echo"[INIT]RAMDiskcreatedat$RAM_DISK"

############################################

setup-ramfs.shRAMdiskcreationscript

RunningtheprecedingscriptwillcreateaRAMdiskfolderat/ramfs—youcantreatitjustlikeanyotherfolder;it’sjustthatitresidesinthesystemmemoryratherthanontheSDcard:

$cd/ramfs

Youcancallthisscriptfromthealarm-control.shscriptaspartoftheinitializationprocessbyincludingtheline:

./etc/pi-alarm/setup-ramfs.sh

ConclusionTheRaspberryPiisapowerfullittlebeastandagreatplatformforbuildinglow-cost,buthighlycapable,embeddedsystems.TheinterfacesbuiltintoitsGPIOconnectormakeiteasytoboltonmodulesusingsimplelow-costelectronicsandabitofconfigurationtocreateveryfunctionalandflexiblesystems.TheinclusionofadedicatedcamerainterfaceandnetworkinginterfacesgiveyoueverythingyoucouldpossibleneedforanInternet-connectedhomesecuritysystem.

I’vecoveredalotoftopicsinthisbook,andIcouldhavegoneonandon,butIhopethatwhatIhavepresentedhasbeendoneinastructuredandmethodicalway,andhasgivenyouthetoolsandtechniquestocarryonthisjourneysothatyouareabletocreatetheperfecthomesecuritysystemforyourneeds.

TipsforbuildingsystemsAsasystemsguywhohastoworkwithmanydifferenttechnologiesanddisciplinesonaday-to-daybasis,Ijustwanttoleaveyouwiththefollowingthoughtstoconsider,ifyouchoosetobuilduponthesystemwe’veputtogetherinthisbook,which,ofcourse,Ihopeyouwill:

Createahigh-leveldiagramofyourproposedsystemfirst—abitliketheoneIproducedearlierinthischapter.Defineeverythinginamodularwaysothatyoucanbuildandtestyoursysteminsmallchunks.Thismakesitmucheasiertospotissuesearlyon.Buildingthesystemusingsmallermodulesmakesiteasiertore-useandreplacecircuitsandcode,anddon’tbeafraidtomix-and-matchtechnologiesusingwhat’sbestfortheindividualmodule.Don’ttrytore-inventthewheel—useexistingcodeandcircuitresourcesthatareproventowork.Thismakesitmuchquickertogetthingsworkingandminimizesthenumberoftimesyouhavetohityourheadagainstabrickwall.Icallitblagging.

SummaryWell,we’vereachedtheendofourjourneytobuildafullyfunctionalandextensiblehomesecuritysystemusingthemightyRaspberryPimini-PC.Inthisfinalchapter,weputtogetheralloftheelementsandconceptsfromthepreviouschapterstocreateahomesecurityframework,bothfromahardwareandsoftwareperspective.

Inparticular,thischapterguidedustowardbuildingamodularframeworkforourhomesecuritysystem,implementingfeaturesthatyouwouldfindinanycommerciallyavailablesystem,andalsothingsthatyoudon’tseeoutthere.Wewalkedthroughthecompletecontrolscript,exploringitsvarioussectionsandunderstandinghowtheyfitintooursystem.

Wealsolearnedhowtoautomaticallystart-upourhomesecuritysystemscriptwhenourRaspberryPibootsup,andhowdataissharedbetweenthePiandtheweb-basedcontrolpanelinreal-timeviatheconfigurationfile.Finally,welookedathowtopreventourSDcardfromburningoutbycreatingaratherusefulRAM-basedtemporaryfilesystem.

IndexA

alarmsystemabout/Alarmsystemdiagramdiagram/Alarmsystemdiagramelements/Overviewofthesystemelementsstartingautomatically/Automaticallystartingthesystembuilding,tips/Tipsforbuildingsystems

anti-tampercircuitsabout/Anti-tampercircuits

anti-tamperloop/Anti-tampercircuitsArduino/Gertboardarm

about/Armingyourselfdocumenting/Armingyourself

armdevice/Connectinga433-MHzreceiverASHRAE

URL/AcarbonmonoxidedetectorATmegamicrocontroller/Gertboardattachments

sending/Sendingattachments

BBashcommand-linecalculator(bctool)

usedforconvertinghxvaluestobinary/BuildingthecontrolscriptBashscript/I’msomeoneelsebattery-backed/A+12Vpowersupplybitbanging/Thealternativeapproach(becausewehavenochoice)

Ccamera,addingtosecuritysystems

prerequisites/PrerequisitesRaspberryPicameramodule/TheRaspberryPicameramodulePiNoIRcameramodule/NightvisionUSBwebcam/UsingUSBcameras

cameraserialinterface(CSI)/TheRaspberryPicameramodulecarbonmonoxide(CO)detector

about/Acarbonmonoxidedetectorcascadingstyle-sheet(CSS)/Creatingthewebpagecontrolpanel

remoteaccess,settingup/RemoteaccesstoourcontrolpanelcontrolpanelHTMLtemplate/ThecontrolpanelHTMLtemplatecontrolscripts

designing/Designingthecontrolscriptsbuilding/Buildingthecontrolscriptcode,exploring/Exploringthescriptcode

controlscriptscodeexploring/Exploringthescriptcodedeclarations/Declarationsconfigsettings,updating/UpdatingconfigsettingsGPIO,settingup/SettinguptheGPIOI2Cportexpander,settingup/SettinguptheI2Cportexpanderzoneinputsstatus,decoding/Decodingthezoneinputsstatusinitialization/Initializationsystemmonitoringloop/Thesystemmonitoringloopsystem,arming/Armingthesystemzones,monitoring/Monitoringthezonesentrydelay/Entrydelaymainalarm,sounding/Soundingthemainalarmsystem,disarming/Disarmingandresettingthesystemsystem,resetting/Disarmingandresettingthesystemfeatures,implementing/We’redone(almost)…

controlvariables/Declarations

Ddatalogging

detecting/Loggingdetectiondataddclientupdater/TheRaspberryPidynamicDNSclientdigitalI/Opins/DigitalI/Opinsdisarm

about/Armingyourselfdisarmdevice/Connectinga433-MHzreceiverDnsOMatic

URL/SettingupadynamicDNSaccountdoors/TheworkingofmagneticcontactsensorsdynamicDNSaccount

settingup/SettingupadynamicDNSaccountRaspberryPidynamicDNSclient/TheRaspberryPidynamicDNSclient

DynDNSURL/SettingupadynamicDNSaccount

Eelaboratelightswitch

about/Themostelaboratelightswitchintheworld,TheElaboratelightswitchre-visitedbreadboard/Themostelaboratelightswitchintheworldcircuitdiagram/Themostelaboratelightswitchintheworldilluminatingscript/Theilluminatingscript

electronickeypad/Arminganddisarmingthesystemelements,alarmsystem

overview/Overviewofthesystemelements+12Vpowersupply/A+12Vpowersupply+3.3Vpowersupply/A+3.3Vpowersupplyopto-isolatorinputmodule/Theopto-isolatorinputmoduleportexpander/Theportexpanderarm/disarmswitch/Anarm/disarmswitchoutputs/Alarmoutputs

emailnotification,setting/Youhavenewmailsenderclient,settingup/Settingupthee-mailsenderclientattachments,sending/Sendingattachmentsinformation,obtaining/Wherewasthattaken?

entry/exitpurposes/Armingyourself

Ffake-hwclockpackage/fake-hwclockffmpegtool/Beavideostarfilesystem,SDCard

raspi-configutility,using/BootingyourPi,Usingtheraspi-configutilityexpanding/Expandingthefilesystem

fixedIPaddress/SettingupadynamicDNSaccountflow-chart/Designingthecontrolscriptsfritzing

URL/Lettherebelightfswebcam

URL/Installingthewebcam

GGertboard

about/GertboardURL/Gertboard

GPACpackage/BeavideostarGPIOconnector

prerequisites,forconnectingto/Prerequisitesabout/SayhellototheGPIOaccess,providing/SayhellototheGPIOdigitalI/Opins/DigitalI/OpinsInter-IntegratedCircuit(I2C)bus/TheI2CbusSerialPeripheralInterface(SPI)bus/TheSPIbusUniversalAsynchronousReceiverandTransmitter(UART)bus/TheUARTserialbusUniversalSerialBus(USB)ports/USBportspowerconnections/Powerconnectionsusing/GettingacquaintedwiththeGPIOconnecting,toLED/Lettherebelight,Gettingflashy…switch,adding/Addingaswitchfloatingstate/Pullingyourselftogetherdetectionscript/Thedetectionscript

GPIOpinexport/SettinguptheGPIO

HH.264videostream/Beavideostarhall-effectsensors/Gettingintothezonehigh-levelprocess/DesigningthecontrolscriptsHobbytronicsMCP23017expanderportkit

about/HobbytronicsMCP23017expanderportkitURL/HobbytronicsMCP23017expanderportkit

II/Opins/PowerconnectionsI2Cbus

about/TheI2CbusSerialDataLine(SDA)wire/Just2wiresSerialClockLine(SCL)wire/Just2wiresaddress,identifying/What’syouraddress?data,transmitting/Thereisaparalleluniverseserial-to-parallelconversion/Serial-to-parallelconversionenabling/EnablingtheI2CBustoolspackage,installing/InstallingtheI2Ctoolspackage

I2Cportexpanderbuilding/BuildinganI2Cexpanderboard,building/Buildingyourexpansionboardsettingup/SettinguptheI2Cportexpander,SettinguptheportexpanderI2Cbus,enabling/EnablingtheI2CBusI2Ctoolspackage,installing/InstallingtheI2Ctoolspackagedevices,searching/Findingourdevices

I2Cportexpandercircuitabout/TheI2Cportexpandercircuit,Let’swalkthroughthecircuitcomponents/TheI2CportexpandercircuitMCP23017portexpanderchip/Let’swalkthroughthecircuithigh/Let’swalkthroughthecircuitlow/Let’swalkthroughthecircuitfloating/Let’swalkthroughthecircuit

i2csettool/Settinguptheportexpanderinductiveloads

driving/Drivinginductiveloadsbells/Drivinginductiveloadslamps/Drivinginductiveloads

infra-redlighting/Isthatabadger?integratedcircuits(ICs)/Serial-to-parallelconversionInter-IntegratedCircuit(I2C)bus/TheI2Cbusintrusion/BeyondintrusionIPaddress/SettingupyourPi

JJessieversion/BootingyourPi

Kkeyswitch/Arminganddisarmingthesystem

LLEDResistorValues

calculating/Lettherebelightlighttpdwebserver/InstallingthewebserverLinux

using/UsingLinux

M433-MHzreceiver

connecting/Connectinga433-MHzreceiverconnecting,alternativeapproach/Thealternativeapproach(becausewehavenochoice)

433-MHzwirelessalarmsystemsabout/433-MHzwirelessalarmsystemsadvantages/433-MHzwirelessalarmsystemsdisadvantages/433-MHzwirelessalarmsystems

magneticcontactsensoradding,prerequisites/Prerequisitesworking/Theworkingofmagneticcontactsensorsconnecting/Connectingourmagneticcontactsensormonitoring/Monitoringthesensor

magneticfield/Theworkingofmagneticcontactsensorsmasterconfigurationfile

using/ThemasterconfigurationfileMCP23017/BuildinganI2CexpanderMicrosoftWindows

using/UsingMicrosoftWindowsmobileoptimized/CreatingthewebpageModel2/RaspberryPiModelB+andModel2Model2board/Sowhichone?ModelA/RaspberryPiModelAModelB/RaspberryPiModelBModelB+/RaspberryPiModelB+andModel2Modulesfile/EnablingtheI2CBusMP4Box/Beavideostarmulticameraset-up

about/ThemulticamerasetupSlavedriver/TheSlavedriver

Nnano/Gettingflashy…Nano/GettingabitofhelpfirstNetworkTimeProtocol(NTP)/Gettingtherighttime,ntpnighttimeshots

capturing/NightvisionTIP120Darlingtontransistor,using/Anilluminatingexperienceelaboratelightswitch/TheElaboratelightswitchre-visitedinfra-redlighting,using/Isthatabadger?badger,watching/Isthatabadger?

No-IPURL/SettingupadynamicDNSaccount

NoIRcameramodule/Nightvisionnormallyclosed(NC)/ConnectingourPIRmotionsensornormallyopen(NO)/ConnectingourPIRmotionsensor

Oon-boardreal-timeclockhardware

obtaining/Gettingtherighttime,fake-hwclockfake-hwclockpackage/fake-hwclockNetworkTimeProtocol(NTP)/ntp

outputsallocating/Beingincontroldocumenting/Beingincontrol

Pparallel-to-serialconversion/Serial-to-parallelconversionPCF8591

URL/AsimpletemperaturesensorPHP5installation

testing/TestingthePHP5installationPHPsupport/InstallingthewebserverPi

types/WhichflavorofPi?ModelA/RaspberryPiModelAModelB/RaspberryPiModelBModelB+/RaspberryPiModelB+andModel2Model2/RaspberryPiModelB+andModel2models,comparing/Modelcomparisontableversion,selecting/Sowhichone?URL/Sowhichone?booting/BootingyourPifilesystem,expanding/Expandingthefilesystemsettingup/SettingupyourPioperatingsystem,updating/Gettinguptodateon-boardreal-timeclockhardware,obtaining/Gettingtherighttimesecurity/Talkingofsecurity…sudo/Whatisthissudothinganyway?

PiFaceDigitalI/Oexpansionboardabout/PiFaceDigitalI/OexpansionboardURL/PiFaceDigitalI/Oexpansionboard

PIRsensorsprerequisites/Prerequisitesabout/Passiveinfraredsensorsexplained,SettingupyourPIRsensorsettingup/SettingupyourPIRsensorguidelines/SettingupyourPIRsensorpowersupply/Givemepower(again)connecting/ConnectingourPIRmotionsensor

port-forwarding/Port-forwardingpowersupply

about/Givemepowerpartrequisites/Givemepower

prerequisites,expansionboard/Prerequisitesprerequisites,PIRsensors/Prerequisitespressurematsensors/GettingintothezonePuTTY

URL,fordownload/SettingupyourPi

RRAM-basedfilesystem

creating/CreatingaRAM-basedfilesystemRaspberryPi

staticIP,settingup/SettingupastaticIPonyourRaspberryPiremoteadministration/RemoteadministrationforourRaspberryPiabout/Conclusion

RaspberryPicameramoduleabout/TheRaspberryPicameramoduleconnecting/Connectingthecameramodulesettingup/Settingupthecameramoduletesting/Testingthecameramodule

RaspberryPiNetworkingCookbookURL/ConnectingviaWi-Fi

Raspbianimagedownloading,URL/DownloadingtheRaspbianimage

RaspbianOSURL/DownloadingtheRaspbianimage

raspistilloptions/Wherewasthattaken?ready-madeexpansionboards

about/Usingready-madeexpansionboardsusing/Usingready-madeexpansionboardsHobbytronicsMCP23017expanderportkit/HobbytronicsMCP23017expanderportkitPiFaceDigitalI/Oexpansionboard/PiFaceDigitalI/OexpansionboardGertboard/Gertboard

receiverwiringdiagram/Thereceiverwiringdiagram

rectifierdiode/Drivinginductiveloadsreedswitch

about/Theworkingofmagneticcontactsensorsnormallyopen(NO)/Theworkingofmagneticcontactsensorsnormallyclosed(NC)/Theworkingofmagneticcontactsensors

remoteaccess,grantingtocontrolpanelabout/RemoteaccesstoourcontrolpaneldynamicDNSaccount,settingup/SettingupadynamicDNSaccountstaticIP,settinguponRaspberryPi/SettingupastaticIPonyourRaspberryPiport-forwarding/Port-forwarding

remoteadministration,RaspberryPiabout/RemoteadministrationforourRaspberryPiWebmin/GettingWebmin

rootuser/Whatisthissudothinganyway?

SSDcard

preserving/PreservingtheSDcardRAM-basedfilesystem,creating/CreatingaRAM-basedfilesystem

SDCardpreparing/PreparingtheSDcardRaspbianOSimage,downloading/DownloadingtheRaspbianimageMicrosoftWindows,using/UsingMicrosoftWindowsLinux,using/UsingLinux

security/Port-forwardingsecuritykeypad/Arminganddisarmingthesystemsensors

hall-effectsensors/Gettingintothezonepressurematsensors/Gettingintothezone

serial-to-parallelconversions/Serial-to-parallelconversionSerialPeripheralInterface(SPI)bus/TheSPIbusshiftregisters/Serial-to-parallelconversionsimpletemperaturesensor

about/Asimpletemperaturesensorworking/Howitworks

simplewaterdetectorabout/Asimplewaterdetectorworking/Howitworks

soft-switchfunction/Anarm/disarmswitchstaticIPaddress

setting,onRaspberryPi/SettingupastaticIPonyourRaspberryPisudoer/I’msomeoneelsesudorights/AccessingWebminlocallysystem

arming/Arminganddisarmingthesystemdisarming/Arminganddisarmingthesystem

TTIP120Darlingtontransistor/Anilluminatingexperience

U433-Utilsoftwareproject

URL/Thealternativeapproach(becausewehavenochoice)Un-usedModulessection/AccessingWebminlocallyUniversalAsynchronousReceiverandTransmitter(UART)bus/TheUARTserialbusUniversalSerialBus(USB)ports/USBportsUSBwebcam

about/UsingUSBcamerasusing/UsingUSBcamerasinstalling/InstallingthewebcamURL/Installingthewebcamsnap,capturing/Takingasnapfswebcam,settingup/Snapsnapsnap

V3.3Vvoltageregulator/Givemepower12Valarmzonecircuits

using/12Valarmzonecircuitsprotecting/Alarmcircuitprotectionworking/Howitworks

videocapturing/Beavideostarusing,insecuritysystem/Caughtoncamera

VideoLANURL/Beavideostar

visudoutility/I’msomeoneelse

WWebmin

URL/GettingWebmin,RemotelyaccessingWebminabout/GettingWebminrepositorysources,updating/Updatingtherepositorysourcessigningkey,importing/Importingthesigningkeyaccessinglocally/AccessingWebminlocallyrootuseraccount/AccessingWebminlocallypiuser/AccessingWebminlocallyremotelyaccessing/RemotelyaccessingWebmin

webpagecreating/CreatingthewebpagecontrolpanelHTMLtemplate/ThecontrolpanelHTMLtemplatestyling/Givingitsomestylemodifyingdynamically/MakingitdynamicPHPconfigurationfilesetting,modifying/GettingabitofhelpfirstmainPHPcode/ThemainPHPcoderunning,asdifferentuser/I’msomeoneelse

webserverinstalling/InstallingthewebserverPHP5installation,testing/TestingthePHP5installation

Wi-Ficonnectingvia/ConnectingviaWi-Fi

Win32DiskImagerutilityURL/UsingMicrosoftWindows

windows/TheworkingofmagneticcontactsensorsWinSCP/Gettingflashy…wirelessPIRsensors

about/WirelessPIRmotionsensors433-MHzwirelessalarmsystems/433-MHzwirelessalarmsystems433-MHzreceiver,connecting/Connectinga433-MHzreceiverreceiverwiringdiagram/Thereceiverwiringdiagram

Zzones

creating/Gettingintothezone

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