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HEWLETT-PACKARD EDUCATION SERVICES

EmbeddedSystems&Robotics

http://www.hpesindia.com

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Contents

Chapter1Basics............................................................................................... 6

1.1 WhatisaDigitalsystem?.................................................................................................... 6

1.2 AssigningStates.................................................................................................................. 6

1.3 NumberSystemsindigitalelectronics............................................................................... 6

1.4 TypesofDigitalCircuits....................................................................................................... 6

1.5 Clock:Buildingblockofasequentialcircuit....................................................................... 7

1.6 LogicGates:Buildingblockofacombinatorialcircuitry..................................................... 7

1.7 PracticalCircuitingElements.............................................................................................. 8

1.7.1 Resistor:...................................................................................................................... 8

1.7.2 Capacitor:.................................................................................................................... 8

1.7.3 Breadboard:................................................................................................................ 9

1.7.4 IntegratedCircuits(IC)................................................................................................ 9

1.7.5 LED............................................................................................................................ 10

Chapter2SomeIntegratedCircuitsandImplementation............................11

2.1 555.................................................................................................................................... 11

2.1.1 Monostablemode..................................................................................................... 11

2.1.2 Astablemode............................................................................................................ 12

2.2 4029counter..................................................................................................................... 13

2.2.1 PinDescription.......................................................................................................... 13

2.3 7447:BCDto7segmentdisplaydecoder......................................................................... 14

2.3.1 PinDescription.......................................................................................................... 14

2.4 LDR(LightDependentResistor)........................................................................................ 14

2.5 OperationalAmplifier(Opamp)........................................................................................ 15

2.5.1 Opampasacomparator........................................................................................... 16

2.6 7805VoltageRegulator.................................................................................................... 16

Chapter3IntroductiontoEmbeddedSystems.............................................18

3.1 Applications...................................................................................................................... 19

3.2 EmbeddedSystemTypes.................................................................................................. 19

Chapter4IntroductiontoMicrocontrollers..................................................20

4.1 WhatisMicrocontroller?.................................................................................................. 20

4.2 BasicArchitecturesofMicrocontrollers ........................................................................... 22

4.3 DigitalIntegratedCircuits(ICs)......................................................................................... 25

4.4 ProcessorType&MemoryStructures.............................................................................. 27

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4.5 OrganizationofDataMemory.......................................................................................... 30

4.6 Compiler/IDE(IntegratedDevelopmentEnvironment).................................................. 33

4.7 Programmer...................................................................................................................... 33

4.8 HowtouseSerialProgrammer'sCircuit(Hardware)........................................................ 34

4.9 USBProgrammer.............................................................................................................. 38

Chapter5CodeVisionAVR(CVAVR).............................................................38

5.1

CHIP:

..................................................................................................................................

40

5.2 PORT:................................................................................................................................ 40

Chapter6IntroductiontoAtmega16Microcontroller.................................43

6.1 Features............................................................................................................................ 43

6.2 PinConfiguration.............................................................................................................. 43

6.3 BlockDiagram................................................................................................................... 44

6.4 PinDescriptions................................................................................................................ 45

6.5 DigitalInputOutputPort.................................................................................................. 46

6.6 Registers............................................................................................................................ 46

Chapter7I/OPorts:....................................................................................... 47

7.1 DDRX(DataDirectionRegister)........................................................................................ 47

7.2 PORTX(PORTXDataRegister)........................................................................................... 48

7.3 PINX(DataReadRegister)................................................................................................ 48

7.4 ASMALLNOTEABOUTDELAY....................................................................................... 49

Chapter8LCDInterfacing.............................................................................. 50

8.1 OverviewofLCDDisplay................................................................................................... 50

8.2 CircuitConnection............................................................................................................ 52

8.3 SettingupinMicrocontroller............................................................................................ 52

8.4 PrintingFunctions............................................................................................................. 54

8.4.1 lcd_clear()................................................................................................................. 54

8.4.2 lcd_gotoxy(x,y).......................................................................................................... 54

8.4.3 lcd_putchar(charc)................................................................................................... 54

8.4.4 lcd_putsf(constantstring)......................................................................................... 54

8.4.5 lcd_puts(chararr)..................................................................................................... 54

8.4.6 itoa(intval,chararr[])............................................................................................... 55

8.4.7 ftoa(floatval,chardecimal_places,chararr[])......................................................... 55

Chapter9ADC:AnalogtoDigitalConverter.................................................56

9.1 Theoryofoperation.......................................................................................................... 57

9.2 SettingupMicrocontroller................................................................................................ 57

9.3 FunctionforgettingADC.................................................................................................. 58

Chapter10 Timers..................................................................................... 59

10.1 WhatisaTimer?........................................................................................................... 59

10.2 HowtoUseTimer......................................................................................................... 59

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10.3 Prescalar....................................................................................................................... 59

10.4 TimerMode.................................................................................................................. 60

10.5 NormalMode................................................................................................................ 60

10.6 CTCMode......................................................................................................................... 60

10.7 PulseWidthModulation(PWM)Mode........................................................................... 61

(A) PWM:PulseWidthModulation........................................................................................... 61

(B) PWMSignalGenerationUsingAvrTimers.......................................................................... 62

(C) PhaseCorrectPWMMode.................................................................................................. 64

10.8 SETTINGUPTIMERSINCODEVISIONAVR....................................................................... 66

10.9 FastPWMMode........................................................................................................... 70

10.10 CTCMode...................................................................................................................... 71

Chapter11 Communication...................................................................... 72

11.1 Data Transfer................................................................................................................ 72

11.2 Classification................................................................................................................. 72

11.3 BaudRate...................................................................................................................... 73

11.4 DifferentCommunicationTechniques.......................................................................... 74

Chapter12 SPI:SerialPeripheralInterface..............................................74

12.1 TheoryofOperation..................................................................................................... 75

12.2 SettingupSPIinMicrocontroller.................................................................................. 80

12.2.1 MasterMicrocontroller ........................................................................................ 80

12.2.2 SlaveMicrocontroller ............................................................................................ 80

12.3 DataFunctions.............................................................................................................. 80

12.3.1 TransmitData....................................................................................................... 81

12.3.2 ReceiveData......................................................................................................... 81

12.4 ConnectingMCUToAnotherMCU............................................................................... 81

Chapter13 USARTCommunication..........................................................82

13.1 USART........................................................................................................................... 82

13.2 HardwareAspectofUSART........................................................................................... 82

13.3 BaudRate...................................................................................................................... 82

13.4 DataTransmission......................................................................................................... 82

13.5 UART:TheoryofOperation.......................................................................................... 83

13.6 SerialPortofComputer................................................................................................ 84

13.7 SettingupUARTinmicrocontroller.............................................................................. 86

13.8 DockLight...................................................................................................................... 88

13.9 ImplementingUSARTinYourCode.............................................................................. 89

13.9.1 putchar()............................................................................................................... 89

13.9.2 getchar()................................................................................................................ 89

13.9.3 putsf().................................................................................................................... 89

Chapter14 Interrupt................................................................................. 91

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Example.................................................................................................................................. 92

14.1 Polling........................................................................................................................... 92

14.2 Hardwareinterrupt....................................................................................................... 92

14.3 HardwareInterruptorpolling?..................................................................................... 93

14.4 SettingupHardwareInterruptinMicrocontroller....................................................... 93

14.5 FunctionsofInterruptServiceRoutine......................................................................... 93

14.6 TimerInterrupt............................................................................................................. 94

14.7 OverflowInterrupt........................................................................................................ 94

14.8 CompareMatchInterrupt............................................................................................. 95

Chapter15 EEPROM................................................................................. 97

Chapter16 IntroductiontoRobots.........................................................100

16.1 WhatIsARobot?........................................................................................................ 102

16.2 RobotChassisDesigning............................................................................................. 103

16.2.1 Robotwithsteeringwheel:................................................................................. 104

16.2.2 Robotwithdifferentialdrive:............................................................................. 104

Chapter17 MotorsandMotorDrivers...................................................105

17.1 IntroductiontoMotors............................................................................................... 105

17.2 H Bridge:.................................................................................................................... 106

17.3 MotorDriverICs:L293/L293DandL298.................................................................... 107

17.3.1 DifferencebetweenL293andL298:................................................................... 109

17.3.2 SpeedControl:.................................................................................................... 109

Chapter18 Sensors................................................................................. 109

18.1 AnalogSensor............................................................................................................. 116

18.2 DigitalIRSensor TSOPSensor................................................................................... 117

Chapter19 ProjectWork........................................................................ 118

19.1 LinefollowingRobot................................................................................................... 118

Chapter20 DefinitionsofEmbeddedsystem............................................119

Chapter21 GLOSSARY................................................................................ 121

Chapter22 References.............................................................................. 126

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SectionADigitalElectronics

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Chapter1 Basics1.1 WhatisaDigitalsystem?

Inmostgeneralterms,thissystemsbehaviorissufficientlyexplainedbyusingonlytwoofits

statescanbeVoltage(morethanxvoltsorless?),distancecovered(morethan2.5kmorless?],true

falseorweightofanelephant(willmyweighingmachinewithstandit?))

Notethatalthoughineverycase,thealltheintermediatestatesAREPOSSIBLEANDDOEXIST,

ourpointofinterestaresuchthatwedontrequiretheirexplicitdescription.Inelectronicsystems

wemostlydealwithVoltagelevelsasdigitalentities.

1.2 AssigningStatesThereisnospecificfixeddefinitionoflogiclevelsinelectronics.Mostcommonlyusedlevel

designationistheoneusedinCMOSandTTL(transistortransistorlogic)families:

Logichigh>designatedas1

Logiclow>designatedas0

Where high and low are actually higher and lower with respect to a reference voltagelevel (ideally taken as 2.5V)

1.3 NumberSystemsindigitalelectronics1. Binary: Only 0 and 1.

2. Hexadecimal: 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F

1.4 TypesofDigitalCircuits

CombinatorialCircuits:Inthesecircuits,thepaststatesareimmaterial

andtheoutputdependsonlyuponthepresentstate.Examplelogicgates

Sequentialcircuits:Inthesecircuits,thenextstateiscompletely

determinedbythepaststates.Hencethesefollowapredictablestructure

andessentiallyrequireatimingdevice.Ex.counters,flipflops.

GOOGLY:Whyassign0and1andnotaandb,xandy,catanddog?

ANS:Computationalease!

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1.5 Clock:BuildingblockofasequentialcircuitAclockissimplyalternatehighandlowstatesofvoltagewithtimei.e.essentiallyasquarewave.

Importanttermsrelatedtoclockareitsdutycycleanditsfrequency:

Dutycycle:ItistheratioofThandTh+Tl

1.6Logic

Gates:

Building block of a combinatorial circuitry

TheseareessentiallycombinatorialcircuitsusedtoimplementlogicalBooleanoperationslikeAND,

NAND,OR,XORandNOT.NOTandNANDarecalleduniversalgatesasanyothergatecanbeformed

usingeitherofthem!

Figure1:TableofLogicGates

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1.7 PracticalCircuitingElements

1.7.1 Resistor:Acolorschemeisfollowedtogivethespecificationsofaresistor.Thetableforcolorcodeisshown

below:

The1st

twobandsspecifythe2digitsoftheresistorvaluewhereasthe3rdbandspecifiesthemultiplierintermsofthepowertowhich10is

raisedandmultipliedtothe2digits.

Thetolerancetellsthepossible%variationoftheresistorvalueabout

thevalueindicatedbybands.

1.7.2 Capacitor:The2typesofcapacitorswefrequentlyuseincircuitsareceramicandelectrolyticcapacitors.While

ceramiccapacitorsdonothaveafixedpolarity;electrolyticcapacitorsshouldbeconnectedintheir

specifiedpolaritiesonlyelsetheymightblowoff!Thispolarityisusuallyprovidedonthesideofthe

capacitorscorrespondingleg.

Figure4:Electrolyticcapwithvepolaritylegseen Figure3:Ceramiccapwithvalue15x104pF

Figure2:TableofResistance

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1.7.3 Breadboard:Thisisthebaseusedforsettingupthecircuit.Thishasembeddedmetalstripsinitthatformagrid

ofconnectionsinsideitsbody.Thisallowsustotakemultipleconnectionsfromasinglepoint

withoutanyneedofsoldering/disorderingasinPCBs.Itisalwaysagoodhabittotestthecircuiton

breadboardbeforemakingitonaPCB.

1.7.4 IntegratedCircuits(IC)ICsorIntegratedCircuitsarepackagedcircuitsdesignedforsome

fixedpurpose.AnIChasitsfixedICname/numberthatcanbeused

togetcatalogofitsfunctionsandpinconfiguration.ICscomein

varioussizesandpackagesdependinguponthepurpose.

NOTE:NumberingschemeofICpinswillbeexplainedinthelab

session.DifferentICsmayhavedifferentnumberofpins.

Figure5:Topviewshowingtheconnectingholes.Bottomviewshowsthecontactmetalstrips

Figure6:IC

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1.7.5 LEDLED(LightEmittingDiode)isfrequentlyusedtodisplaytheoutputsatvariousstagesofthecircuit.It

isessentiallyaDiodewith theenergyreleased in the formofphotonsdue toelectron transitions

fallinginthevisibleregion.Hencenormaldiodepropertiesapplytoit.

It glows only in fwd bias mode i.e. with pjunction connected to +ve voltage and njunction to

negative.

Diodes are essentially low power devices. The current through the LED should be less than

20mA.Hencealwaysputa220ohmresistorinserieswiththeLED.

Never forget that LEDs consume a significantamountof powerof theoutputs of the ICs (CMOS

based).Hence it isadvisabletoonlyusethemforcheckingthevoltage level(highor low)andthen

removethem.

Figure7:LEDs

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Chapter2 SomeIntegratedCircuitsandImplementation2.1 555555isanICusedtogenerateaclock.The

twoattributesofaclockare

Frequency Dutycycle.

BothofthesecanbechangedusingthisIC,

howeverthedutycycleisalways

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2.1.2 AstablemodeInthismode;theoutputisstableneitherinhighstatenorinlowstate.Henceitoscillatesfrom

onestatetoanothergivingusasquarewaveorclock.WecansettheclockfrequencyandDutycycle

Dbytheformulae:

F=.

D=

Figure10:555inastablemode

NOTE:CapacitorC2isjusttofilterthenoiseanditsvaluecanbesuitablychosentobe0.01F.Itcan

alsobeneglected.

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2.2 4029counterWiththeclockmade,wearereadytocountthenumberofpulsespassedintothecircuit.Notethat

anykindofcountingrequiresamemory(yougottoknowthatyouhavejustcounted3togoto

4!). Hence4029canalsobeusedasamemoryelementthatremembersitsimmediateprevious

state.

Figure11:4029pinconfiguration

2.2.1 PinDescriptionPINNo. Name Pinfunction Connectionreqd.

1 Parallelload Ifgivenhigh;loadsthevalueof

Parallelbitintotheo/pbits

Gnd

2 OutputBit 3 Mostsignificantbitofo/p Topin6of7447

3 Parallelinputbit3 Mostsignificantbitofparalleli/p Input

4 Parallelinputbit0 Leastsignificantbitofparalleli/p Input

5 Clockenablebar Lowonthispinenablescountingas

pertheclockreceived

Gnd

6 OutputBit 0 Leastsignificantbitofparallelo/p Topin7of7447

7 TCbar Outputbitthatgivesalowwhenthe

countiscomplete.Canbeusedtosignal

theendofcounting.

Noneifyoudont

wanttouseit

8 Gnd Neededforpowering Gnd

9 Binary/Hexbar Tochooseb/wbinaryand

hexadecimalmodes

lowforcount015

highforcount09

10 Up/Downbarcount Tochooseb/wupcountingand

downcountingmodes

Lowfordowncount

Highforupcount

11 Outputbit1 2ndbitofo/p Topin1of7447

12 Parallelinputbit1 2nd

bitofi/p Input

13 Parallelinputbit2 3rdbitofi/p Input

14 Outputbit2 3rdbitofo/p Topin2of7447

15 Clockpulse Clockpulseisgivenhere Clockfrom555

16 Vdd Neededforpowering +5V

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2.3 7447:BCD to 7 segment display decoderFor displaying the number in the counter output on a seven segment display (i.e. 7 LEDsmaking up a figure of 8 as in a general calculator. See fig. )we need to decode the 4 bits andmatch them to the 7 pins for lighting the LEDs corresponding to the number. This work isdone by 7447.

Figure12:7447pinconfiguration

2.3.1 PinDescription

PIN

no.

Name Function Connectionreqd.

1 i/pB 2ndbit(O1)of4029so/p ToO1of4029

2 i/pC 3rdbit(O2)of4029so/p ToO2of4029

3 LampTest

bar

UsedtocheckthatallLEDsof7seg

areworking.

Highfornormalfn

Lowtoglowall

LEDs

4 BI/RBI Kepthightoallownormalfunction Kepthigh5 RBI Blanks0frombeingdisplayed Kepthigh

6 i/pD Mostsignificantbit(O3)of4029s

o/p

ToO2of4029

7 i/pA 3rdbit(O2)of4029so/p ToO2of4029

8 Gnd Forpower Connectedtognd

915 agasperthe

fig

Theo/ppinsto7segmentdisplay To7segdisplay

16 Vcc Forpower Connectedto+5V

NOTE:

TheCOMpinsaretobeconnectedtoVccvia220ohmresistor.Whyresistorisrequired??

Thedotpinisjustfordisplayofdecimalpointandessentiallyonlymakestheupperand

lowersidesdistinguishablefromeachotherforasingledisplay.withouttheasymmetry

producedbydothowwillwebeabletoseewhichsideisupperandwhichislower?

2.4 LDR(LightDependentResistor)

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LightDependentResistor(LDR)orphotoresistorisadevicethatactslikearesistanceandits

resistancevarieswiththeintensityoflightincidentonit.Inthisdevice,ifphotonsofsufficient

energyfallonit,theresistancedropsdrasticallyastheelectronsinthesemiconductorareableto

jumpfromthevalencebandtotheconductionbandandareavailableforconduction.TheLDRsused

aremostlyresponsivetovisiblelight.Theresistancemightdropfromashighas1M inthedarkto1

k inbrightlight.

2.5 OperationalAmplifier(Opamp)Opampisaveryimportantdeviceusedineverydayelectronics.Itisessentiallyadifferential

amplifierwithaveryhighgainoftheorderof105!BydifferentialamplifierImeanthatitamplifies

thedifferenceof2signalsandgivestheoutput.

Opampequation:

Vout=A(V+ V) whereAisthegainoftheorder105.

Ironically,thishighgaininopenloopmakesitimpossibletouseitasageneralpurpose

differentialamplifierdirectly.

Figure13:LDRs.Thecoiledportionisresponsivetolight

GOOGLY: If(V+V)=0.005V;Vss=12Vwhatwillbetheoutput??

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2.5.1 OpampasacomparatorSimplestuseofOpampisasacomparator.Itcanbeusedtoconvertananalogsignaltoadigital

signaldefinedbyafixedthreshold.SetV asthethresholdvoltagesay2.5Vandapplytheanalog

signaltobedigitizedatV+.Whatwillbetheoutput?Wellifyouhaveworkedoutthegoogly;this

shouldbeapieceofcake!

2.6 7805VoltageRegulator7805voltageregulatorisusedtoget+5Voutputoutofahighervoltagesupply(7.5V20V).Weuse

adapterssupplytogenerate+5Vhere.Connectthegndand+12Vofadaptertothepinsasshown

andget+5Vdirectlyasanoutputoutofthe3rdpin.Currentupto0.5Acanbeobtainedfromthis

regulatorwithoutanysignificantfallinvoltagelevel.

NOTE:Use2capacitorsofvaluesay0.1Ftofilterthenoiseintheinputandoutputofregulators

supplyasshown.

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SectionBEmbeddedSystems

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Someimportantthingstonoteaboutembeddedsystems:

1. Onceanembeddedhardware isprogrammed foracertain task, it isused forever for the

sametask.Changingthefirmwareafterwardsisnotpossible.

2. Such systemsare limited in computational resources likememory,CPUprocessing speed,

I/Ofacilitiesbutarestillcapableofperformingthetaskgiventothemveryefficiently.

3. Embeddedsystemscanalsobehavingareducedfunctionalityversionofoperatingsystem

calledRTOS(RealTimeOperatingSystem)forhighlyspecializedapplications.

4. Is a system built to perform its duty, completely or partially independent of humanintervention?

5. Is specially designed to perform a few tasks in the most efficient way.6. Interacts with physical elements in our environment, viz. controlling and driving a

motor, sensing temperature, etc.

3.1 ApplicationsAn embedded system can be defined as a control system or computer system designed to

perform a specific task. Examples:

1. Pen drives (for controlling the communication between P.C. and Flash Chip and also the

small LED!)2. Hard disks( again for the same purpose)3. Mouse(Reads and Interprets the Sensors and send final result to P.C.),Keyboards4. Printers: Ever opened a printer for installing ink cartridge? Then you must have seen the

printed head. There are motors to control the print head and the paper movement. Your

P.C. is not directly connected to them but there is built in MCU of printer to control all

these. Your P.C. just sends the data (pixels) through the communication line (USB or

parallel).But the MCU used here is fairly fast and has lots of RAM.

5. Automobiles6. Calculators, Electronic wending machines, Electronic weighing scales, Phones(digital

with LCD and phonebook)

7. Cell phones8. SecuritySystem

9. Alarmsystem

10.Automobilesystem

11.DigitalCamera

12.Environmentmonitoringsystems(usingsensorsandactuators)

Embeddedsystemsareoftenrequiredtoperformrealtimeoperations.ByRealtimeoperations,we

meanthat,operationswheredelayofevenafewmillisecondscouldbedangerous.Somerealtime

systemsmaybe:

1. SensorsysteminNuclearPlants

2. Flightcontrolsystems

3. AutomobileBrakingsystemandenginecontrollingsystems

Thesearesituationswhereweneedveryaccuratetimingandcontrol.Failureinsuchsituationsmay

causegreatloss.

3.2 EmbeddedSystemTypes

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y NonRealtimeEmbeddedsystem isone inwhichthere isnodeadline,even if fast

responseorhighperformanceisdesiredorpreferred.

y RealtimeEmbeddedSystems:Wheredeadlineistobemet.

Softrealtimeembeddedsystems.

Hardrealtimeembeddedsystems.

y FollowingaresomeapplicationsofEmbeddedSys.butnotrealtime.

SecuritySystems. MobileandPDA.

AlarmSystem.

Automobilesystem.

DigitalCamera.

y ExamplesofRealtimeEmbeddedsystems.

SensorsysteminNuclearplants.

Missiledefencesystem.

Flightcontrolsystem.

AnticollisionsysteminAutomobiles.

Chapter4 IntroductiontoMicrocontrollers4.1 WhatisMicrocontroller?

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WhatisaMicrocontroller?

A Microcontroller is a programmable digital processor with necessary peripherals. Both

microcontrollers andmicroprocessorsarecomplexsequentialdigitalcircuitsmeanttocarryout

jobaccording to theprogram/ instructions.Sometimesanalog input/output interfacemakesa

part of microcontroller circuit of mixed mode(both analog and digital nature).

AmicrocontrollercanbecomparedtoaSwissknifewithmultiplefunctions incorporated in the

sameIC.

Fig.4.1 AMicrocontrollercomparedwithaSwissknife

MicrocontrollersVsMicroprocessors

1. A microprocessor requires an external memory for program/data storage. Instruction

executionrequiresmovementofdatafromtheexternalmemorytothemicroprocessoror

viceversa.Usually,microprocessorshavegoodcomputingpowerandtheyhavehigherclock

speedtofacilitatefastercomputation.

2. A microcontroller has required onchip memory with associated peripherals. A

microcontrollercanbethoughtofamicroprocessorwithinbuiltperipherals.

3. A microcontroller does not require much additional interfacing ICs for operation and it

functionsasastandalonesystem.Theoperationofamicrocontroller ismultipurpose,just

likeaSwissknife.

4. Microcontrollers are also called embedded controllers. A microcontroller clock speed is

limitedonly toa few tensofMHzMicrocontrollersarenumerousandmanyof themare

applicationspecific.

Development/Classificationofmicrocontrollers(Invisible)

Microcontrollers havegone througha silentevolution (invisible).Theevolutioncanbe rightly

termedassilentastheimpactorapplicationofamicrocontrollerisnotwellknowntoacommon

user,althoughmicrocontrollertechnologyhasundergonesignificantchangesinceearly1970's.

Developmentofsomepopularmicrocontrollersisgivenasfollows.

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Intel4004 4bit(2300PMOStrans,108kHz)197

1

Intel8048 8bit197

6

Intel8031 8bit(ROMless) .

Intel8051 8bit(MaskROM)198

0

Microchip

PIC16C64

8

bit

198

5

Motorola68HC11 8bit(onchipADC) .

Intel80C196 16bit198

2

AtmelAT89C51 8bit(Flashmemory) .

MicrochipPIC16F877 8bit(Flashmemory+ADC) .

Developmentofmicroprocessors(Visible)

Microprocessors have undergone significant evolution over the past four decades. This

developmentisclearlyperceptibletoacommonuser,especially,intermsofphenomenalgrowth

incapabilitiesofpersonalcomputers.Developmentofsomeofthemicroprocessorscanbegiven

asfollows.

Intel4004 4bit(2300PMOStransistors) 1971

Intel8080

8085

8bit(NMOS)

8bit1974

Intel8088

8086

16bit

16bit1978

Intel80186

80286

16bit

16bit1982

Intel80386 32bit(275000transistors) 1985

Intel80486 SX

DX

32bit

32bit(builtinfloatingpointunit)1989

Intel80586 I

MMX

CeleronII

III

IV

64bit

1993

1997

1999

2000

Z80(Zilog) 8bit 1976

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4.2 BasicArchitecturesofMicrocontrollersWe use more number of microcontrollers compared to microprocessors. Microprocessors are

primarilyusedforcomputationalpurpose,whereasmicrocontrollers findwideapplicationindevices

needingrealtimeprocessing/control.

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Similarlyall the Integratedcircuitshave their function tablesand inputandoutputpins fixed.You

cannotchangethefunctionandnoinputpinactasoutputandviceversa.Sowheneveryouwantto

designsomecircuityoufirsthavetogettheoutputasafunctionofinputsandthendesignitusing

gatesorwhatevertherequirementis.

Soonceacircuit isbuiltwecannotchange its function!Even ifyouwant tomake somechanges

again youhave to considerall thegatesand components involved.Now if youaredesigningany

circuit which involves change of the function table every now and then you are in trouble ! For

example if IwanttodesignanAutonomousRobotwhichshouldperformvarioustasksand Idont

justwanttofixthetask.SupposeImakeittomoveinapaththenIwanttochangethepath!Howtodothat?

HerecomestheuseofMicrocontrollers! NowifIgiveyouanIntegratedCircuitwith20pinsandtell

you that you can make any pin as output or input also you can change the function table by

programming the ICusingyourcomputer!Thenyour reactionswillbewow!Thatsnice :)Thats

whatthemostbasicfunctionofamicrocontroller is. IthassetofpinscalledasPORTandyoucan

make any pin either as output or input. After configuring pins you can program it to perform

accordingtoanyfunctiontableyouwant.Youcanchangetheconfigurationorthefunctiontableas

manytimesyouwants.

There are many Semiconductor Companies which manufactures

microcontrollers.Someofthemare:

Intel

Atmel

Microchip

Motorola

WewilldiscussaboutAtmelMicrocontrollers commonlyknownasAVRinthissection.

Question:Howamicrocontrollerworks?

Answer:WellIcannotgointolotofdetailsabouttheworkingbecauseitisavasttopicinitself.Ican

justgiveanoverview.

Microcontroller consists of an Microprocessor (CPU that is Central processing Unit) which is

interfacedtoRAM(RandomAccessMemory)andFlashMemory(oneyourpendrivehas!).Youfeed

your program in the Flash Memory on the microcontroller. Now when you turn on the

microcontroller, CPUaccessesthe instructionfromRAMwhichaccessyourcodefromFlash.Itsets

theconfigurationofpinsandstartperformingaccordingtoyourprogram.

Question:Howtomakethecode?

Answer:YoubasicallywritetheprogramonyourcomputerinanyofthehighlevellanguageslikeC,

C++,andJAVAetc.Thenyoucompilethecodetogeneratethemachinefile.Nowyouwillaskwhat

thismachinefile is.Allthemachinesunderstandonlyone language,0&1that isonandoff.Now

this0&1bothcorrespondsto2differentvoltagelevelsforexample0voltfor0logicand+5voltfor

1logic.Actuallythecodehastobewritteninthis0,1languageandthensavedinthememoryofthe

microcontroller. But this will be very difficult for us ! So we write the code in the language we

understand(C)andthencompileandmakethemachinefile(.hex).Afterwemakethismachinefile

wefeedthistothememoryofthemicrocontroller.

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Question:HowtofeedthecodeintheflashofMicrocontroller?

Answer:Assumingyouhavethemachinefile(.hex)readyandnowyouwanttofeedthattotheflash

of the microcontroller. Basically you want to make communication between your computer and

microcontroller.NowcomputerhasmanycommunicationportssuchasSerialPort,ParallelPortand

USB(UniversalSerialBus).

LetstakeSerialPort,ithasitsowndefinitionthatisvoltageleveltodefine0&1(yeahallthedata

communication is ajust collection of 0 &1 ) Serial Port's protocol is called as UART (Universal

AsynchronousReceiver&Transmitter) Itsvoltage levelsare :12voltfor0 logicand+12volt for1logic.

Now the voltage levels of our microcontroller are based on CMOS (Complementary Metal Oxide

Semiconductor)technologywhichhas0voltfor0logicand+5voltfor1logic.

Twodifferentmachineswith2differentwaystodefine0&1andwewanttoexchangeinformation

betweenthem.ConsidermicrocontrollerasFrenchandComputer'sSerialPortasanIndianperson

(obviouslynocommon language inbetween!) If theywant toexchange information theybasically

needamediatorwhoknowsboththelanguage.Hewilllistenonepersonandthentranslatetoother

person.SimilarlyweneedacircuitwhichconvertsCMOS(microcontroller)toUART(serialport)and

viceversa.Thiscircuit iscalledasprogrammer.Using thiscircuitwecanconnectcomputer to the

microcontrollerandfeedthemachinefiletotheflash.

TheAVR(AdvancedVirtualRisc)isaModifiedHarvardarchitecture8bitRISCsinglechip

microcontroller(C)whichwasdevelopedbyAtmelin1996.TheAVRwasoneofthefirst

microcontrollerfamiliestouseonchipflashmemoryforprogramstorage.

4.4 ProcessorType&MemoryStructures

Microcoded

and

hard

coded

processors:

Theimplementationofcomputerarchitecturecanbebroadlyachievedintwoways.Acomputerisa

complexsequentialdigitalcircuitwithbothcombinationalandsequentialcircuitcomponents. Ina

microcodedprocessor,eachinstructionisrealizedbyanumberofstepsthatareimplementedusing

small subroutines.These subroutinesarecalledmicrocodes storedwithin the instructiondecode

unit.Hence,amicrocodedprocessorcanbecalledaprocessorwithinaprocessor.

Microcodedprocessor:

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Letus

1.2.3.4.5.6.

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M

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Thefi

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are

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Aswealre

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4.6Atmel

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:

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Programmerbasicallyconsistsoftwoparts:

Software(toopen.hexfileonyourcomputer)

Hardware(toconnectmicrocontroller)

Hardwaredependson thecommunicationportyouareusingon thecomputer (Serial,Parallelor

USB). Isuggestbeginners touseSerialProgrammeras it isveryeasytobuild.Software forthat is

PonyProg.SomefamousWindows(XP,Vista)programmersare:

PonyProg(Serial,Parallel)

AVRdude(supportsmanyhardwares)

AVRStudio(supportsAtmel'shardware)

ATProg(Serial)

USBASP(USB)

4.8 HowtouseSerialProgrammer'sCircuit(Hardware)Thisistheeasiestprogrammercircuittomake.YoujusthavetogetSerialPortconnectorandthree

1Kresistorsandyouaredone!CircuitDiagramisattached.

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NowopenthedatasheetofAtmegayouareusing(IamusingAtmega16).Gotothepin

configurationandfindthefollowingpinsandconnecttheprogrammer.Programmingisdone

throughSPI(SerialPeripheralInterface)whichinvolvesMISO,MOSIandSCKpins.RESETisusedto

resetthechip.0voltonthispinwillresetthechipandfornormalrunningitshouldbepulledupto

+5V.

MOSI(MasterOutSlaveIn)

MISO(MasterInSlaveOut)

SCK(SerialClock)

RESET

GND(Ground)

NowconnectthepowersuppliesthatareVccandGNDtothemicrocontroller.

Vcc=+5VandGND=0V

DonotforgettoconnectResettoVccwitha1K/10Kresistorforpullingup.

Thatisitwearereadywiththehardware.

Note: TheTrainerBoardhasOnBoardSerialProgrammer.

Software

AsItoldyoutherearetwopartsofaprogrammer,hardwareandsoftware.Wecanbuildthis

hardwareasitisveryeasywithjust34components.Nowweneedsoftwarewhichsupportthishardwareandcancommunicatewithmicrocontrollerusingthiscircuit.Thereare2goodsoftwares

forWindows.Theyare,

PonyProg

AtProg

BothofthemsupportSerialaswellasParallelport,butIhavealwayspreferredserialportbecauseit

hasonly9pins,henceasmallerconnectorisrequired.

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Nowletusdiscussaboutthem.

AtProg

I consider it as simplest programmer ever. The circuit we discussed is actually basedon this

programmer.Downloadthefolderfromthewebsite,unzipit.Ithasanexecutablefilenamedat

prog.exedoubleclicktoexecuteit.

GotoPORTandselecttheaddressofserialport

(bydefaultCOM1).OnceyouclickthatSercon2

detectedshouldappearintheActivitytab.Thatis

thenameoftheprogrammercircuit.

Turnonthepowersupplyandconnectthecircuit

tothemicrocontroller.

ClickonCheck,itshouldshowOKintheActivity

tabanddevicename(ATMEGA16)will

automaticallycomeinthetabbelowcheck

option.Thisistheautodetectoptionofthis

programmerwhichautodetectsthedevicename

connectedbyitssignature.

NowjustopenthedevicefilefromFile>OpenandclickonWrite. Itwillwriteandverifythe

program.Done!Sosimpleisntit?:)

PonyProg

OneofthemostcommonlyusedprogrammersonWindows.Downloaditfromthewebsiteand

installit.Nowletssetitupforourhardware.

FirstselectAVRmicroandAVRAuto(youcanalsospecifydevicename,Atmega16)inthechip

options(lasttwodropdowntabs)

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GototheSetup>InterfaceSetup.Thendothesettingsasshown inthepicturebelow.Then

connect thecircuitto themicrocontroller,turnon thepowersupply.NowclickonProbe.You

shouldgetTestOKmessage.Ifnot,checkyourconnectionsagain.

Now lets read theMicrocontroller. Go toCommand>Read All. It should start reading the

signatureandtheflashmemory.YoushouldgetReadSuccessfulmessageafterthat.

Sowearedonewiththesettingsandtestings.Everythingisworkingfine:)Nowjustopenthe

hexfilefromFile>OpenDeviceFile

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Go to Command>WriteProgram (Flash). It will start writing and then verifying the code.

Congratulations:)youdidit!

4.9 USBProgrammerUSBaspisaUSBincircuitprogrammerforAtmelAVRcontrollers.ItsimplyconsistsofanATMega48

oranATMega8anda coupleofpassivecomponents.Theprogrammerusesa firmwareonlyUSBdriver;nospecialUSBcontrollerisneeded.

Chapter5 CodeVisionAVR(CVAVR)

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AnIDEhasfollowingfunctions:

Preprocessing

Compilation

Assembly

Linking

ObjectTranslation

TextEditor

Ifwejustusecompilerand linker independentlywe stillneed togeta texteditor.Socombiningeverythingwillactuallymess thingsup.So thebestway is togetSoftwarewhichhas itall.Thats

calledanIntegratedDevelopmentEnvironment,inshortIDE.

I consider CodeVisionAVR to be the best IDE for getting started with AVR programming on

WindowsXP,Vista.IthasaverygoodCodeWizardwhichgeneratecodesautomatically!Youneed

notmesswiththeassemblywords.So inallmytutorials IwillbeusingCVAVR.Youcandownload

evaluationversionforfreewhichhascodesizelimitationbutgoodenoughforourpurpose.

For all my examples I will be using Atmega16 as default microcontroller because it very easily

availableand ispowerfulenoughwith sufficientnumberofpinsandperipheralsweuse.Youcan

havealookonthedatasheetofAtmega16inthedatasheetsection.

Letstakealookonthesoftware.Themainwindowlookslikefollowing,

NowclickonFile >New >Project

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ApopupwindowwillcomeaskingwhetheryouwanttouseCodeWizardAVR,obviouslyselectyes

becausethatisthereasonweareusingCVAVR!

NowhavealookonthisWizard.IthasmanytabswherewecanconfigurePORTS,TIMERS,LCD,ADC

etc.Iamexplainingsomeofthem

5.1 CHIP:Select thechip forwhichyouaregoing towrite theprogram.Thenselect the frequencyatwhich

Chipisrunning.BydefaultallchipsaresetonInternalOscillatorof1MHzsoselect1MHzifthatis

thecase.Ifyouwanttochangetherunningclockfrequencyofthechipthenyouhavetochangeits

fusebits(Iwilltalkmoreaboutthisinfusebitssection).

5.2 PORT:

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PORTisusuallyacollectionof8pins.

From this tab you can select which pin you want to configure as output and which as input. It

basicallywritestheDDRandPORTregisterthroughthissetting.RegistersarebasicallyRAMlocations

whichconfigurevariousperipheralsofmicrocontrollerandbychangingvalueoftheseregisterswe

can change the function it isperforming. Iwill talkmoreabout registers later.All thedetailsare

providedinthedatasheet.

Soyoucanconfigureanypinasoutputorinputbyclickingthebox.

ForAtmega16whichhas4Portswecansee4tabseachcorrespondingtoonePort.Youcanalsoset

initial

value

of

the

Pins

you

want

to

assign.

or

if

you

are

using

a

pin

as

input

then

whether

you

want

tomakeitaspulluportristated,againIwilltalkindetailsaboutthesefunctionslater.

SimilarlyusingthiscodewizardyoucanveryeasilyconfigurealltheperipheralsontheAtmega.

NowforgeneratingcodejustgotoFile >Generate,SaveandExit(ofthecodewizard)

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Now itwillaskyounameand locationforsavingthreefiles.Twobeingprojectfilesandonebeing

the .C filewhich isyourprogram. try tokeepsamenamesofallthree files toavoidconfusion.By

defaultthesefilesaregeneratedinC:\CVAVR\bin

Thegeneratedprogramwillopeninthetexteditor.HavealookithassomedeclarationslikePORT,

DDR,TCCR0andmanymore.Theseareallregisterswhichconfiguresvarious functionsofAtmega

and by changing these value we make different functions. All the details about the registers are

commentedjustbelow them.Nowgodownand find following infinitewhile loop there.We can

startwritingourpartofprogramjustbeforethewhileloop.Andasformostoftheapplicationswe

wantmicrocontrollertoperformthesametaskforeverweputourpartofcodeintheinfinitewhileloopprovidedbythecodewizard!

While (1)

{

//Placeyourcodehere

};

}

Seehowfriendlythiscodewizardis,allthework(configuringregisters)automaticallydoneandwe

dontevenneedtounderstandandgotothedetailsaboutregisterstoo!

Nowwewanttogeneratethehexfile,sofirstcompiletheprogram.EitherpressF9orgotoProject

>Compile.

Itwillshowcompilationerrorsifany.Ifprogramiserrorfreewecanproceedtomakingofhexfile.

SoeitherpressShift+F9orgotoProject >Make.Apopupwindowwillcomewith information

aboutcodesizeandflashusageetc.

Sothemachinefileisreadynow!Itisinthesamefolderwherewesavedthose3files.

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Cha

6.1

6.2

ter6 InFeatures

Advanced

Upto16M

16KBytes

512BytesE

1KByteInt

32Progra

InSystem

8channel,

Two8bitT

One16bit

FourPWM

Programm

Master/Sla

Byteorient

Programm

Externalan

PinConfi

troducti

ISCArchitec

IPSThrough

fInSystem

EPROM

ernalSRAM

mableI/OLi

rogramming

10bitADC

imer/Counte

Timer/Count

Channels

bleSerialUS

veSPISerialI

edTwo

wire

bleWatchd

dInternalIn

uration

ntoAtm

ure

utat16MH

elfProgram

nes

byOnchip

rswithSepa

erwithSepa

ART

nterface

SerialInterf

gTimerwith

erruptSourc

ega16M

z

mableFlash

ootProgram

atePrescale

ratePrescale

ce

SeparateOn

es

icrocont

rsandComp

r,Compare

chipOscilla

oller

reModes

ode,andCa

or

pture

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6.3 BlockDiagram

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6.4 PinDescriptionsVCC:Digitalsupplyvoltage.(+5V)

GND:Ground.(0V)Notethereare2groundPins.

PortA(PA7 PA0)

PortAservesastheanaloginputstotheA/DConverter.PortAalsoservesasan8bitbidirectional

I/O

port,

if

the

A/D

Converter

is

not

used.

When

pins

PA0

to

PA7

are

used

as

inputs

and

are

externallypulledlow,theywillsourcecurrentiftheinternalpullupresistorsareactivated.ThePort

Apinsaretristatedwhenaresetconditionbecomesactive,eveniftheclockisnotrunning.

PortB(PB7 PB0)

PortBisan8bitbidirectionalI/Oportwithinternalpullupresistors(selectedforeachbit).PortB

also serves the functions of various special features of the ATmega16 as listed on page 58 of

datasheet.

PortC(PC7 PC0)

PortCisan8bitbidirectionalI/Oportwithinternalpullupresistors(selectedforeachbit).PortC

alsoservesthefunctionsoftheJTAGinterfaceandotherspecialfeaturesoftheATmega16aslisted

onpage61 ofdatasheet. If the JTAG interface is enabled, thepullup resistorson pinsPC5(TDI),

PC3(TMS)andPC2(TCK)willbeactivatedevenifaresetoccurs.

PortD(PD7 PD0)

PortDisan8bitbidirectionalI/Oportwithinternalpullupresistors(selectedforeachbit).PortD

also serves the functions of various special features of the ATmega16 as listed on page 63 of

datasheet.

RESET: ResetInput.Alowlevelonthispinforlongerthantheminimumpulselengthwillgeneratea

reset,eveniftheclockisnotrunning.

XTAL1:Externaloscillatorpin1

XTAL2:Externaloscillatorpin2

AVCC: AVCC is the supply voltage pin for Port A and the A/D Converter. It should be externally

connected toVCC,even if theADC isnotused. If theADC isused, itshouldbeconnected toVCC

throughalowpassfilter.

AREF:AREFistheanalogreferencepinfortheA/DConverter.

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6.5 DigitalInputOutputPortSoletsstartwithunderstandingthefunctioningofAVR.WewillfirstdiscussaboutI/OPorts.AgainI

remind you that I will be using and writing about Atmega16. Lets first have a look at the Pin

configurationofAtmega16.Imageisattached,clicktoenlarge.

Youcanseeithas32I/O(Input/Output)pinsgroupedasA,B,C&Dwith8pinsineachgroup.This

groupiscalledasPORT.

PA0 PA7(PORTA)

PB0 PB7(PORTB)

PC0 PC7(PORTC)

PD0 PD7(PORTD)

Noticethatallthesepinshavesomefunctionwritteninbracket.Theseareadditionalfunctionthat

pincanperformotherthanI/O.Someofthemare.

ADC(ADC0 ADC7onPORTA)

UART(Rx,TxonPORTD)

TIMERS(OC0 OC2)

SPI(MISO,MOSI,SCKonPORTB)

ExternalInterrupts(INT0 INT2)

6.6 RegistersAlltheconfigurationsinmicrocontrollerissetthrough8bit(1byte)locationsinRAM(RAMisabank

of memory bytes) of the microcontroller called as Registers.All the functions are mapped to its

locations in RAM and the value we set at that location that is at that Register configures the

functioningofmicrocontroller.Therearetotal32x8bitregisters inAtmega16.AsRegistersizeof

thismicrocontrolleris8bit,itcalledas8bitmicrocontroller.

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Chapter7 I/OPorts:InputOutputfunctionsaresetbyThreeRegistersforeachPORT.

DDRX >SetswhetherapinisInputorOutputofPORTX.

PORTX >SetstheOutputValueofPORTX.

PINX >ReadstheValueofPORTX.

Go

to

the

page

50

in

the

datasheet

or

you

can

also

see

the

I/O

Ports

tab

in

the

Bookmarks.

7.1 DDRX(DataDirectionRegister)Firstofallweneedtosetwhetherwewantapintoactasoutputorinput.DDRXregistersetsthis.

EverybitcorrespondstoonepinofPORTX.LetshavealookonDDRAregister.

Bit 7 6 5 4 3 2 1 0

PIN PA7 PA6 PA5 PA4 PA3 PA2 PA1 PA0

NowtomakeapinactasI/OwesetitscorrespondingbitinitsDDRregister.

TomakeInputsetbit0

TomakeOutputsetbit1

IfIwriteDDRA=0xFF(0xforHexadecimalnumbersystem)thatissettingallthebitsofDDRAtobe

1,willmakeallthepinsofPORTAasOutput.

SimilarlybywritingDDRD=0x00thatissettingallthebitsofDDRDtobe0,willmakeallthepinsof

PORTDasInput.

Nowletstakeanotherexample.ConsiderIwanttosetthepinsofPORTBasshownintable,

PORTB

PB7 PB6 PB5 PB4 PB3 PB2 PB1 PB0

Function Output Output Input Output Input Input Input Output

DDRB 1 1 0 1 0 0 0 1

ForthisconfigurationwehavetosetDDRBas11010001whichinhexadecimalisD1.Sowewillwrite

DDRB=0xD1

Summary

DDRX >tosetPORTXasinput/outputwithabyte.

DDRX.y >tosetythpinofPORTXasinput/outputwithabit(worksonlywithCVAVR).

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7.2 PORTX(PORTXDataRegister)ThisregistersetsthevaluetothecorrespondingPORT.NowapincanbeOutputorInput.Solets

discussboththecases.

OutputPin

Ifapinissettobeoutput,thenbysettingbit1wemakeoutputHighthatis+5Vandbysettingbit0

wemakeoutputLowthatis0V.

Letstakeanexample.ConsiderIhavesetDDRA=0xFF,thatisallthepinstobeOutput.NowIwant

tosetOutputsasshownintable,

PORTA PA7 PA6 PA5 PA4 PA3 PA2 PA1 PA0

Value High(+5V) High(+5V) Low(0V) Low(0V) Low(0V) High(+5V) High(+5V) Low(0V)

PORTA 1 1 0 0 0 1 1 0

For this configurationwe have to setPORTAas11000110which in hexadecimal isC6. Sowewill

writePORTA=0xC6;

InputPin

Ifapin is set tobe input, thenby setting its correspondingbit inPORTX registerwillmake itas

follows,Setbit0 >TriStatedSetbit1 >PullUp

Tristatedmeanstheinputwillhang(nospecificvalue)ifnoinputvoltageisspecifiedonthatpin.

PullUpmeansinputwillgoto+5Vifnoinputvoltageisgivenonthatpin.Itisbasicallyconnecting

PINto+5Vthrougha10KOhmresistance.

Summary

PORTX >tosetvalueofPORTXwithabyte.

PORTX.y >tosetvalueofyth

pinofPORTXwithabit(worksonlywithCVAVR)

7.3 PINX(DataReadRegister)ThisregisterisusedtoreadthevalueofaPORT.IfapinissetasinputthencorrespondingbitonPIN

registeris,

0forLowInputthatisV2.5V(Ideally,butactually0.8V 2.8Viserrorzone!)

ForanexampleconsiderIhaveconnectedasensoronPC4andconfigureditasaninputpinthrough

DDRregister.NowIwanttoreadthevalueofPC4whetheritisLoworHigh.SoIwilljustcheck4th

bitofPINCregister.

Wecanonly readbitsof thePINXregister;canneverwriteon thatas it ismeant forreading the

valueofPORT.

Summary

PINX >ReadcompletevalueofPORTXasabyte.

PINX.y >ReadythpinofPORTXasabit(worksonlywithCVAVR).

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7.4 ASMALLNOTEABOUTDELAYChasinbuiltlibrarieswhichcontainmanyprebuiltfunctions.OnesuchfunctionisDelay,which

introducesatimedelayataparticularstep.Toinvokeitinyourprogram,youneedtoaddthe

followinglineatthebeginningofyourcode:

#include;

Thereafter,

it

can

be

used

in

the

program

by

adding

the

following

line:

delay_ms(X);

WhereXisthetimedelayyouwishtointroduceatthatparticularstepinmilliseconds.

IhopeyoumusthavegotbasicideaaboutthefunctioningofI/OPorts.Fordetailedreadingyoucan

alwaysrefertodatasheetofAtmega.

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Chapter8 LCDInterfacingNowweneedtointerfaceanLCDtoourmicrocontrollersothatwecandisplaymessages,outputs,

etc.SometimesusinganLCDbecomesalmost inevitable fordebuggingandcalibrating thesensors

(discussed later).Wewilluse the16x2 LCD,whichmeans ithas two rowsof16characterseach.

Henceintotalwecandisplay32characters.

8.1Overview

of

LCD

Display

LCD displays are widely used in many applications like mobile phones, robotics, DVD players,

Measurement instrumentsetc. Intelligent LCDdisplaysareverycapablebecause theycandisplay

complete ASCII character set and even graphics. These displays are easily connected with micro

controllerandmicroprocessors. LCDdisplaysarecompleteembedded system in them,because it

includemicrocontroller,RAMandROM.

16X2LCDDISPLAY

LCDModulescanpresenttextualinformationtouser.Itslikeacheapmonitorthatyoucanhook

inallofyourgadgets.

Theycomeinvarioustypes.Themostpopularoneis16x2LCDmodule.Ithas2rows&16columns.

Theintelligentdisplaysaretwotypes:

a)TextDisplay

b)GraphicsDisplay

TextdisplaycandisplayallcharactersetandgraphicsdisplaycanshowanyGraphicsbecause theyareinterfacedpixelwise.

In recent year the LCD is finding widespread use replacing LEDs (seven segment LEDs or

multisegmentLEDs).

Thisisduetothefollowingreasons:

a)ThedecliningpricesofLCDs.

b)Theabilitytodisplaythenumbers,charactersandgraphics.ThisisnotpossibleinLEDs,whichcan

displaythenumbersandfewcharacters.

c)Incorporation of a refreshing controller into the LCD, Thereby reliving the CPU of the task of

refreshingtheLCD.Incontrast,theLEDmustberefreshedbytheCPU(orinsomeotherway)tokeep

displayingthedata.

TheinterfacingofLCDisquitedifficult.Butwewilltrytomakeitsimpleandletusexplainitforyou.

Wewill learnhow to interface the text intelligent LCDdisplay.Thesedisplaysareavailable in themarketof16columnandoneRowandmorethanonerowdisplays.

BlockDiagramofLCDDisplay

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MICROCONTROLLER:

ItisthebrainofLCDdisplay.ThisishandlingtheallworkingoftheLCD.

DATARAM:

ThisRAMisstoringtheASCIIvaluesofcorrespondingcharacterswhichwillbedisplayedontheLCD.

For each column there is one location in the RAM. When we will store the ASCII value at that

locationthanitscorrespondingcharacterwillbedisplayedonthescreen.

CODERAM:

ThisRAMstoresthebinarypatternaccordingtothecharacter.

ROM:

ThisROMstoresthebinarypatternwhichisaccordingtothePixelsofLCDandtherearepatternsof

everycharacter.

COMMANDREGISTER:

Itstoresvariouscommandsforproperfunctioning.

DATAREGISTER:

This register work as buffer for data lines and the internal buses of LCD. The ASCII values ofcharacterswillbegiventothedataregister.

BF(BUSYFLAG):

ItindicatestheinternalworkingoftheLCD.ItshowwhetherLCDisbusyinanyoperationornot.

IfBF=0(LCDisidlewecanproceedfornextoperation)

IfBF=1 (LCD isbusywecannotproceed fornextoperationandwehave towaitunlessoperation

completes).

DESCRIPTION

OF

PINS

IS

GIVEN

BELOW:

VCC,VSSandVO:

WhileVCCandVSSprovide+5Voltsandground,respectivelyVEEisusedforcontrollingLCDcontrast

RS(REGISTERSELECT):

TheRSpinisusedtoselectDataRegisterorCommandRegister.

Data

Register

Command

Register

Busy

Code

RAM

DataRAMMicro

controller

ROM

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IfRS=

theho

IfRS=

R/W(

When

When

EN(E

The E

suppli

prese

There

D7D0

This is

LCDsi

BKLE

These

LCDdi

8.2There

Thec

8.3When

figure.

,CRRegiste

meetc.

,DRRegiste

READ/WRITE

R/W=0,Writ

R/W=1Read

ABLE):

able pin is

ed to data p

tatthedata

shouldbepo

:

8bitdatap

internalregis

(LEDA,LED

pinsareuse

splaycanbe

CircuitC

are16pinsi

nnectionsha

Settingu

weconnect

ToenableL

isselected,

isselected,

):

eoperation..

Operation

used by the

ins, a negati

pins.Thispu

sitiveedgea

ins.D7D0a

ters.

K):

dtogivethe

viewedinth

nnection

anLCD;See

vetobema

inMicro

anLCDtoAt

Dinterfacin

allowingthe

allowingthe

LCD to latc

ve edge is a

lsemustbe

ENpinwhe

eusedtos

supplytot

dark.

reverseside

easshown

ontrolle

mega16,on

ginthemicr

Fig

usertosend

usertosend

h binary bits

pplied to thi

minimumo

nreadopera

nd informati

eback light

oftheLCDf

elow:

fullPORT is

ocontroller,j

re14:LCDcon

acommand

datatobedi

available o

s pin So tha

450nswid

ionisrequir

ontotheL

oftheLCDd

rthePINco

dedicatedt

ustclickont

ections

suchasclea

splayonthe

its data pi

t the LCD la

.

d.

Dorreadth

isplay.So,th

figuration.

it,denoted

heLCDtabi

rdisplay,cur

LCD.

ns. When d

tches in the

econtentso

atcontento

byPORTXi

theCodeW

erat

ta is

data

fthe

fthe

nthe

izard

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andselect thePORTatwhichyouwant toconnect theLCD.WewillselectPORTC.Alsoselectthe

numberofcharactersper line inyourLCD.This is16 inourcase.CodeWizardnowshowsyouthe

complete listofconnectionswhichyouwillhavetomake inorderto interfacetheLCD.Theseare

nothingbutthesameasintheabovefigureforgeneralPORTX.

Figure15:LCDsettingsonCVAVRwizardwindow.

Asyoucansee,therearesomespecialconnectionsotherthanthosetouC,Vccandgnd.Thesearegeneral LCD settings. Pin 3 (VO) is for the LCD contrast, ground it through a

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8.4 PrintingFunctionsNow once the connections have been made, we are ready to display something on our screen.

Displayingournamewouldbegreattostartwith.SomeofthegeneralLCDfunctionswhichyoumust

knoware:

8.4.1 lcd_clear()Clearsthe lcd.Remember!Callthisfunctionbeforethewhile(1) loop,otherwiseyouwontbeable

toseeanything!

8.4.2 lcd_gotoxy(x,y)Place the cursor at coordinates (x,y) and start writing from there. The first coordinate is (0,0).

Hence,xrangesfrom0to15andyfrom0to1inourLCD. Supposeyouwanttodisplaysomething

startingfromthe5thcharacterinsecondline,thenthefunctionwouldbe

lcd_gotoxy(5,1);

8.4.3 lcd_putchar(charc)Todisplayasinglecharacter.E.g.,

lcd_putchar(H);

8.4.4 lcd_putsf(constantstring)Todisplayaconstantstring.Eg,

lcd_putsf(IITKanpur);

8.4.5 lcd_puts(chararr)To display a variable string, which is nothing but an array of characters (data type char) in C

language . e.g., You have an array char c[10] which keeps on changing. Then to display it, the

functionwouldbecalledas

lcd_puts(c);

Nowwehaveseenthatonlycharactersorstrings(constantorvariable)canbedisplayedontheLCD.

Butquiteoftenwehavetodisplayvaluesofnumericvariables,whichisnotpossibledirectly.Hence

weneed to firstconvert thatnumericvalue toa stringand thendisplay it.Fore.g., ifwehavea

variableoftype integer,say intk,andweneedtodisplaythevalueofk(whichchangeseverynow

andthen,200nowand250afterasecond...andsoon).Forthis,weusetheCfunctionsitoa()and

ftoa(),butremembertoincludetheheaderfilestdlib.htousetheseCfunctions.

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8.4.6 itoa(intval,chararr[])Itstores thevalueof integerval in thecharacterarrayarr.E.g.,wehavealreadydefined int iand

charc[20],then

itoa(i,c);

lcd_puts(c);

Similarlywehave

8.4.7 ftoa(floatval,chardecimal_places,chararr[])Itstoresthevalueoffloatingvariablefinthecharacterarrayarrwiththenumberofdecimalplaces

asspecifiedbysecondparameter.E.g.,wehavealreadydefinedfloatfandcharc[20],then

ftoa(f,4,c); //till4decimalplaces

lcd_puts(c);

NowwearereadytodisplayanythingwewantonourLCD.Justtryoutsomethingwhichyouwould

like

to

see

glowing

on

it!

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Chapter9 ADC:Analog to Digital ConverterMost of the physical quantities around us are continuous. By continuous, we mean that the

quantitycantakeanyvaluebetweentwoextremes.Forexample,theatmospherictemperaturecan

take any value within a certain range. If an electrical quantity is made to vary directly in

proportiontothisvaluethenwhatwehaveisanAnalogueSignal.Nowwehave broughtaphysical

quantity into theelectricaldomain.Theelectricalquantity inmostcases isvoltage.Tobringthis

quantityintodigitaldomainwehavetoconvertthisintodigitalform.ForthisanADCoranalogue

todigitalconverterisneeded.MostmodernMCUincludingAVRshaveanADConchip.AnADCconvertsaninputvoltageintoanumber.AnADChasaresolution.A8bitADChasarange

of0255.(28=256)TheADCalsohasaReferenceVoltage(ARef).WhentheinputvoltageisGNDthe

outputis0andwhentheinputvoltageisequaltoAReftheoutputis255.Sotheinputrangeis0to

ARefandtheoutputrangeis0to255.

InputVoltage DigitalOutput

0V 0

2.5V 127

5V 255

You

can

see

that

any

analogue

signal

is

not

perfectly

converted

a

factor

that

affects

the

outputquality isthesamplingrate.The ADC cannot continuously read theinputsignal and

change its output it doesso incertain time intervals. The frequencyatwhich itsamplesthe

inputiscalleditssamplingrate.

Also, thevalue of the analoguesignal read is not stored perfectly for example, a voltage

of2.501 would be read as 2.5V i.e. 127 in digital format. Thus, the signal is quantized,or,

inotherterms,thereiscertaingraininesstothedigitalsignalthatyouobtain.Howaccurateyour

digitalsignal isdependsonyourresolutionhigher resolutionwillmakeyourdigitalsignalmore

accurate.

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9.1What

(logic

requirissuch

ADC is

voltag

value

isnot

Refer

and 1

Refer

used.

+5Vis

9.2

Theoryo

we havesee

).Butwhati

eatool

that

atool.

availableate and get co

rangesfrom

required.

ncevoltage

23 for 10 b

nce Voltage)

Forexample,

digitally102

Settingu

operatio

ntillnowth

fwehavean

convertsthis

PORTAofA

rresponding

to1023.Bu

isthevoltag

it). Hence, t

into 1024

iftherefere

and2.5Vis

Microco

ADC=Vi

ADC=Vi

atthe input

analoginpu

analog

volt

mega16.Th

digital value

twecanals

towhichth

e ADC of At

r 256 equal

ncevoltagei

approximate

troller

x255/Vref

x1023/Vr

giventouC

,i.e.,valuev

geto

discret

swehave8

s. The ADC r

useonly8b

eADCassign

mega16 divi

parts, depen

s5Vandwe

lyequalto5

(8

ef(10bit)

asdigital, i

ariesovera

evalues.

An

pinsavailab

egister is a

itoutofit(0

sthemaxim

des the inpu

ding upon

use10bitA

2.

bit)

.e.,either +5

range,say0

logto

Digita

lewherewe

0 bit regist

to255)ast

umvalue(2

t analog vol

hether 10 b

C,0Vhasdi

V(logic1)

to+5V?Th

lConverter

(

canapplya

r, i.e., the d

omuchpre

5incaseof

age range (

it or 8 bit A

gitalequival

r0V

nwe

ADC)

alogigital

ision

8bit

V to

DC is

nt0,

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ToenableADCinAtmega16,clickontheADCtabinCodeWizardandenablethecheckbox. Youcan

alsocheckuse8bitsasthatissufficientforourpurposeand10bitaccuracyisnotrequired.Ifthe

inputvoltagerangesfrom0tolessthan+5V,thenapplythatvoltageatAREF(pin32)andselectthe

Volt.Ref.asAREFpin.Butifitrangesfrom0to+5V,youcanselecttheVolt.Ref.asAVCCpinitself.

Keeptheclockat itsdefaultvalueof125kHzandselecttheAutoTriggerSourceasFreeRunning.

Youcanalsoenableaninterruptfunctionifyourequire.

9.3 FunctionforgettingADCNowwhenyougenerateandsavethecode,alltheregistervaluesaresetautomaticallyalongwitha

function:

unsignedcharread_adc(unsignedcharadc_input).

ThisfunctionreturnsthedigitalvalueofanaloginputatthatpinofPORTAwhosenumberispassedasparameter,e.g.,ifyouwanttoknowthedigitalvalueofvoltageappliedatPA3,andthenjustcall

thefunctionas,

read_adc(3);

IftheADCis8bit,itwillreturnavaluefrom0to255.MostprobablyyouwillneedtoprintitonLCD.

So,thecodewouldbesomewhatlike

inta;charc[10]; //declareinthesectionofglobalvariables

a=read_adc(3);

itoa(a,c);

lcd_puts(c);