Embedded computing and mechatronics with the PIC32 microcontroller

613 Pages·2015·26.404 MB·English

by  Elwin, Matthew, Lynch, Kevin M., Marchuk, Nicholas

Embedded Computing and Mechatronics
with the PIC32 Microcontroller
Embedded Computing and
Mechatronics with the PIC32
Microcontroller
Kevin M. Lynch
Nicholas Marchuk
Matthew L. Elwin
AMSTERDAM(cid:129)BOSTON(cid:129)HEIDELBERG(cid:129)LONDON
NEWYORK(cid:129)OXFORD(cid:129)PARIS(cid:129)SANDIEGO
SANFRANCISCO(cid:129)SINGAPORE(cid:129)SYDNEY(cid:129)TOKYO
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Notices
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ISBN:978-0-12-420165-1
PrintedandboundinUS
Dedication
To Yuko, Erin, and Patrick.
–Kevin M. Lynch
To Mark and Liz.
–Nicholas Marchuk
To Hannah.
–Matthew L. Elwin
Figure Credits
Theauthorsthankthefollowingcompaniesforpermissiontousetheircopyrightedimagesin
thisbook.
*MicrochipTechnology,Inc.www.microchip.com.
*DigiInternational,Inc.www.digi.com.
*PololuRoboticsandElectronics.www.pololu.com.
*Digi-KeyElectronics.www.digikey.com.
*AdvancedPhotonix,Inc.www.advancedphotonix.com.
*ContelecAG.www.contelec.ch/en.
*OmegaEngineering,Inc.,Stamford,CT06907USA.www.omega.com.
*AvagoTechnologies.www.avagotech.com.
*Micro-Measurements,abrandofVishayPrecisionGroup(VPG),Raleigh,NC,USA.
www.vpgsensors.com.
*MaxonPrecisionMotors.www.maxonmotorusa.com.
*CopleyControls.www.copleycontrols.com.
*H2WTechnologies.www.h2wtech.com.
*HitecRCDUSA.www.hitecrcd.com.
Preface
ThisbookisabouttheMicrochip32-bitPIC32microcontroller,itshardware,programmingit
inC,andinterfacingittosensorsandactuators.Thisbookalsocoversrelatedmechatronics
topicssuchasmotortheory,choosingmotorgearing,andpracticalintroductionstodigital
signalprocessingandfeedbackcontrol.Thisbookiswrittenfor:
• AnyonestartingoutwiththeMicrochipPIC3232-bitmicrocontroller.Microchip
documentationcanbehardtonavigate;thisisthebookwewishwehadwhenwestarted!
• ThehobbyistreadytoexplorebeyondArduino.Arduinosoftwareanditslargeuser
supportcommunityallowyoutobeupandrunningquicklywithAtmelmicrocontrollers.
ButrelianceonArduinosoftwarepreventsyoufromfullyexploitingorunderstandingthe
capabilityofthemicrocontroller.
• Teachersandstudentsinmechatronics.Theexercises,onlinematerial,andassociated
kitaredesignedtosupportintroductory,advanced,andflippedoronlinecoursesin
mechatronics.
• Anyoneinterestedinmechatronics,actuators,sensors,andpracticalembedded
control.
Contents
Thisbookwaswrittenbasedonthetwo-quartermechatronicssequenceatNorthwestern
University,ME333IntroductiontoMechatronicsandME433AdvancedMechatronics.In
ME333,studentslearnaboutPIC32hardware,fundamentalsofprogrammingthePIC32inC,
theuseofsomebasicperipherals,andinterfacingthePIC32withsensorsandactuators.In
ME433,materialfromtherestofthebookisusedasreferencebygroupsworkingon
projects.Studentstakingthesequencerangefromsophomorestograduatestudents.Theonly
prerequisiteisintroductorycircuitanalysisanddesign;experienceinCprogrammingisnot
required.WhileexperienceinCwouldallowfasterprogressionthroughthematerial,we
decidednottorequireit,tomakethecourseavailabletothebroadsetofstudentsinterestedin
thematerial.TopartiallycompensateforthewiderangeofexperienceinC(fromexpertto
none),webeginME333withanintensivetwo-weekintroductiontofundamentalCconcepts
andsyntaxusingthe“CrashCourseinC”inAppendixA.Wealsotakeadvantageofstudent
expertisebyfacilitatingpeermentoring.
xix
xx Preface
ThegoalsofthisbookmirrorthoseoftheNorthwesternmechatronicssequence:
• toprovidethebeginnerasoundintroductiontomicrocontrollersusingtheexampleofthe
PIC32,amodern32-bitarchitecture;
• todosobyfirstprovidinganoverviewofmicrocontrollerhardware,firminthebeliefthat
microcontrollerprogrammingismuchmoregroundedwhentightly connectedtothe
hardwarethatimplementsit;
• toprovideaclearunderstandingofthefundamentalsofprofessionalPIC32programming
inC,whichbuildsafoundationforfurtherexplorationofthePIC32’scapabilitiesusing
Microchipdocumentationandotheradvancedreferences;
• toprovidereferencematerialandsamplecodeonthemajorperipheralsandspecial
featuresofthePIC32;
• toinstillanunderstandingofthetheoryofmotoroperationandcontrol;and
• toteachhowmicrocontrollerperipheralscanbeusedtointerfacewithsensorsandmotors.
Toachievethesegoals,thebookisdividedintofivemainparts:
1. Quickstart.Thispart(Chapter1)allowsthestudenttogetupandrunningwiththePIC32
quickly.
2. Fundamentals.Afterachievingsomeearlysuccesswiththequickstart,thefivechapters
inFundamentals(Chapters2to6)examinethePIC32hardware,thebuildprocessinC
andtheconnectionofthecodetothehardware,theuseoflibraries,andtwoimportant
topicsforreal-timeembeddedcomputing:interruptsandthetimeandspaceefficiencyof
code.Thetimeinvestmentinthesechaptersprovidesthefoundationneededtomove
quicklythroughlaterchaptersandtoprofitfromotherreferencematerial,likeMicrochip’s
PIC32ReferenceManual,DataSheets,andXC32C/C++CompilerUser’sGuide.
3. PeripheralReference.Thispart(Chapters7to20)givesdetailsontheoperationofthe
variousperipheralsonthePIC32,aswellassamplecodeandapplications.Itisprimarily
referencematerialthatcanbereadinanyorder,thoughwerecommendthefirstfew
chapters(digitalI/O,counter/timers,outputcompare,andanaloginput)becoveredin
order.TheperipheralreferenceconcludeswithanintroductiontoHarmony,Microchip’s
recentframeworkforhigh-levelprogrammingofPIC32s.
4. Mechatronics.Thispart(Chapters21to29)focusesoninterfacingsensorstoa
microcontroller,digitalsignalprocessing,feedbackcontrol,brushedDCmotortheory,
motorsizingandgearing,controlbyamicrocontroller,andotheractuatorssuchas
brushlessmotors,steppermotors,andservomotors.
5. Appendixes.Theappendixescoverbackgroundtopicssuchasanalysisofsimplecircuits
andanintroductiontoprogramminginC.WehaveourstudentsfirstgetusedtowritingC
programsontheirlaptops,andcompilingwithgcc,beforemovingontoprogramminga
microcontroller.
Preface xxi
InME333,wecoverthecrashcourseinC;theQuickstart;theFundamentals;selecttopics
fromthePeripheralReference(digitalI/O,counter/timers,outputcompare/PWM,andanalog
input);andsimplesensorinterfacing,DCmotortheory,motorsizingandgearing,andcontrol
ofaDCmotorfromtheMechatronicspart.OtherchaptersareusedforreferenceinME433
andotherprojectsthatstudentsundertake.
Choicesmadeinthisbook
WemadeseveralchoicesabouthowtoteachmechatronicsinME333,andthosechoicesare
reflectedinthisbook.Ourchoicesarebasedonthedesiretoexposeourstudentstothetopics
theywillneedtointegratesensorsandactuatorsandmicrocontrollersprofessionally,subject
totheconstraintthatmoststudentswilltakeonlyoneortwocoursesinmechatronics.Our
choicesarebasedonwhatwebelievetobethesmallestbuildingblocksthatamechatronics
engineerneedstoknowabout.Forexample,wedonotattempttoteachmicrocontroller
architectureatthelevelthatacomputerengineermightlearnit,sinceamechatronicsengineer
isnotlikelytodesignamicrocontroller.Ontheotherhand,wealsodonotrelyonsoftware
andhardwareabstractionsthatkeepthebuddingmechatronicsengineeratarm’slengthfrom
conceptsneededtoprogressbeyondthelevelofahobbyist.Withthatphilosophyinmind,
herearesomeofthechoicesmadeforME333andthisbook:
• Microcontrollersvs.sensorsandactuators.Mechatronicsengineeringintegratessensors,
actuators,andmicrocontrollers.Handingastudentamicrocontrollerdevelopmentboard
andsamplecodepotentiallyallowsthecoursetofocusonthesensorsandactuatorspart.
InME333,however,weoptedtomakeunderstandingthehardwareandsoftwareofthe
microcontrollerapproximately50%ofthecourse.Thischoicerecognizesthefundamental
rolemicrocontrollersplayinmechatronics,andthatmechatronicsengineersmustbe
comfortablewithprogramming.
• Choiceofmicrocontrollermanufacturer.Therearemanymicrocontrollersonthemarket,
withawidevarietyoffeatures.ManufacturersincludeMicrochip,Atmel,Freescale,
TexasInstruments,STMicroelectronics,andmanyothers.Inparticular,Atmel
microcontrollersareusedinArduinoboards.Arduinosareheavilyusedbyhobbyistsand
inK-12anduniversitycoursesinlargepartduetothelargeonlineusersupport
communityandthewidevarietyofadd-onboardsanduser-developedsoftwarelibraries.
Inthisbook,weoptforthecommerciallypopularMicrochipPICmicrocontrollers,and
weavoidthehigh-levelsoftwareabstractionssynonymouswithArduino.(Arduinosare
usedinotherNorthwesterncourses,particularlythosefocusingonrapidproduct
prototypingwithlittle mechatronicsdesign.)
• Choiceofaparticularmicrocontrollermodel.Microchip’smicrocontrollerlineconsists
ofhundredsofdifferentmodels,including8-bit,16-bit,and32-bitarchitectures.Wehave
chosenamodern32-bitarchitecture.Andinsteadoftryingtowriteabookthatdealswith
allPIC32models,whichincludessixdifferentfamiliesofPIC32sasofthiswriting(see
xxii Preface
AppendixC),wefocusononeparticularmodel:thePIC32MX795F512H.Thereasons
forthischoiceare(a)itisapowerfulchipwithplentyofperipheralsandmemory
(128KBdataRAMand512KBprogramflash),and,moreimportantly,(b)focusingona
singlechipallowsustobeconcreteinthedetailsofitsoperation.Thisisespecially
importantwhenlearninghowthehardwarerelatestothesoftware.(Oneofthereasons
Microchip’sdocumentationisdifficulttoread,andissofullofexceptionsandspecial
cases,isthatitiswrittentobegeneraltoallPIC32sinthecaseoftheReferenceManual,
orallPIC32sinaspecificfamilyinthecaseoftheDataSheets.)Oncethereaderhas
learnedabouttheoperationofaspecificPIC32,itisnottoodifficulttolearnaboutthe
differencesforadifferentPIC32model.
• Programminglanguage:C++vs.Cvs.assembly.C++isarelativelyhigh-level
language,Cislowerlevel,andassemblyislowerstill. WechoosetoprograminC
becauseoftheportabilityofthelanguage,whilestayingrelativelyclosetotheassembly
languagelevelandminimizing abstractionsintroducedbyC++.
• IntegratedDevelopmentEnvironmentvs.commandline.MPLABXisMicrochip’s
IntegratedDevelopmentEnvironment(IDE)fordevelopingsoftwareforPICs.Sowhydo
weavoidusingitinthisbook?Becausewefeelthatithideskeystepsinunderstanding
howthecodeyouwriteturnsintoanexecutableforthePIC32.Inthisbook,codeis
writteninatexteditorandtheCcompilerisinvokedatthecommandline.Thereareno
hiddensteps.Oncethereaderhasmasteredthematerialinthefirstfewchaptersofthis
book,MPLABwillnolongerbemysterious.
• UseoftheHarmonysoftwarevs.ignoringit.Microchipprovidesanextensivelibraryof
middleware,devicedrivers,systemservices,andothersoftwaretosupportalloftheir
PIC32models.Onegoalofthissoftwareistoallowyoutowriteprogramsthatare
portableacrossdifferentPIC32models.Toachievethis,however,asignificantamountof
abstractionisintroduced,separatingthecodeyouwritefromtheactualhardware
implementation.ThisisbadpedagogicallyasyoulearnaboutthePIC32.Instead,weuse
low-levelsoftwarecommandstocontrolthePIC32’speripherals,reinforcingthehardware
documentationinthisbookandintheDataSheetandReferenceManual.Onlywiththe
morecomplicatedperipheralsdoweusetheHarmonysoftware,specificallyforUSB,in
Chapter20.
• Samplecodevs.writingityourself.TheusualwaytolearntoprogramPIC32sistotake
someworkingsamplecodeandtrytomodifyittodosomethingelse.Thisisnatural,
exceptthatifyourmodifiedcodefails,youareoftenleftwithnoideawhattodo.Inthis
bookweprovideplentyofsamplecode,butwealsofocusonthefundamentalsof
programmingthePIC32sothatyoulearntowritecodefromscratchaswellasstrategies
todebugifthingsgowrong(Figure0.1).
Thephilosophyrepresentedbythechoicesabovecanbesummedupsuccinctly:Thereshould
benomagicsteps!Youshouldknowhowandwhythecodeyouwriteworks,andhowit
Preface xxiii
This book
PIC32
programming
ability Usual
Copying
trajectory
code
Foundations
Quickstart
Time
Figure0.1
ThetrajectoryofPIC32programmingabilityvs.timefortheusual“copyandmodify”approachvs.
thefoundationalapproachinthisbook.Thecrossovershouldoccuratonlyafewweeks!
connectstothehardware.Youshouldnotbesimplymodifyingopaqueandabstractcode,
compilingwithamysteriousIDE,andhopingforthebest.
TheNU32developmentboard
TheNU32developmentboardwascreatedtosupportthisbook.Ifyoudonothavetheboard,
youcanstilllearnalotabouthowaPIC32worksfromreadingthisbook.Wehighly
recommendthatyougettheNU32boardandthekitofmechatronicsparts,however,toallow
youtoworkthroughtheexamplesinthebook.
Inkeepingwiththe“nomagic”philosophy,theprimaryfunctionoftheNU32istobreakout
thepinsofthePIC32MX795F512Htoasolderlessprototypingbreadboard,toalloweasy
wiringtothepins.Otherwisewetrytokeeptheboardasbarebonesandinexpensiveas
possible,leavingexternalcircuitstothereader.Toallowyoutogetupandrunningasquickly
aspossible,though,theboarddoesprovideafewdevicesexternaltothePIC32:twoLEDs
andtwobuttonsforsimpleuserinteraction;a3.3Vregulator(toprovidepowertothePIC32)
anda5Vregulator(toprovideacommonlyneededvoltage);aresonatortoprovideaclock
signal;andaUSB-to-UARTchipthatsimplifiescommunicationbetweentheuser’scomputer
andthePIC32.
ThePIC32ontheNU32comeswithabootloaderprogrampre-installed,allowingyouto
programthePIC32withjustaUSBcable.TheNU32canalsobeprogrammeddirectlyusinga
programmerdevice,likethePICkit3.ThisiscoveredinChapter3.6.