Arduino uno User manual

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ARDUINOUNOREV3
Code:A000066
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TheUNOisthebestboardtogetstartedwithelectronicsand
coding.Ifthisisyourfirstexperiencetinkeringwiththeplatform,
theUNOisthemostrobustboardyoucanstartplayingwith.The
UNOisthemostusedanddocumentedboardofthewholeArduino
family.
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ArduinoUnoisamicrocontrollerboardbasedontheATmega328P(datasheet).It
has14digitalinput/outputpins(ofwhich6canbeusedasPWMoutputs),6analog
inputs,a16MHzquartzcrystal,aUSBconnection,apowerjack,anICSPheader
andaresetbutton.Itcontainseverythingneededtosupportthemicrocontroller;
simplyconnectittoacomputerwithaUSBcableorpoweritwithaAC‐to‐DC
adapterorbatterytogetstarted..YoucantinkerwithyourUNOwithoutworring
toomuchaboutdoingsomethingwrong,worstcasescenarioyoucanreplacethe
chipforafewdollarsandstartoveragain.

"Uno"meansoneinItalianandwaschosentomarkthereleaseofArduino
Software(IDE)1.0.TheUnoboardandversion1.0ofArduinoSoftware(IDE)were
thereferenceversionsofArduino,nowevolvedtonewerreleases.TheUnoboard
isthefirstinaseriesofUSBArduinoboards,andthereferencemodelforthe
Arduinoplatform;foranextensivelistofcurrent,pastoroutdatedboardsseethe
Arduinoindexofboards.
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Youcanfindhereyourboardwarrantyinformations.
https://www.arduino.cc/en/Main/warranty
GettingStarted
YoucanfindintheGettingStartedsectionalltheinformationyouneedto
configureyourboard,usetheArduinoSoftware(IDE),andstarttinkerwithcoding
andelectronics.
https://www.arduino.cc/en/Guide/HomePage
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TECHSPECS
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MicrocontrollerATmega328P
OperatingVoltage5V
InputVoltage(recommended)7‐12V
InputVoltage(limit)6‐20V
DigitalI/OPins14(ofwhich6providePWMoutput)
PWMDigitalI/OPins6
AnalogInputPins6
DCCurrentperI/OPin20mA
DCCurrentfor3.3VPin50mA

FlashMemory32KB(ATmega328P)ofwhich0.5KBusedbybootloader
SRAM2KB(ATmega328P)
EEPROM1KB(ATmega328P)
ClockSpeed16MHz
LED_BUILTIN13
Length68.6mm
Width53.4mm
Weight25g
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OSH:Schematics
ArduinoUnoisopen‐sourcehardware!Youcanbuildyourownboardusingthe
followingfiles:

EAGLEFILESIN.ZIP
https://www.arduino.cc/en/uploads/Main/arduino_Uno_Rev3‐02‐TH.zip
SCHEMATICSIN.PDF
https://www.arduino.cc/en/uploads/Main/Arduino_Uno_Rev3‐schematic.pdf
BOARDSIZEIN.DXF
http://arduino.cc/documents/ArduinoUno.dxf
Programming
TheArduinoUnocanbeprogrammedwiththe(ArduinoSoftware(IDE)).Select
"Arduino/GenuinoUnofromtheTools>Boardmenu(accordingtothe
microcontrolleronyourboard).Fordetails,seethereferenceandtutorials.
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TheATmega328ontheArduinoUnocomespreprogrammedwithabootloaderthat
allowsyoutouploadnewcodetoitwithouttheuseofanexternalhardware
programmer.ItcommunicatesusingtheoriginalSTK500protocol(reference,C
headerfiles).
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Youcanalsobypassthebootloaderandprogramthemicrocontrollerthroughthe
ICSP(In‐CircuitSerialProgramming)headerusingArduinoISPorsimilar;seethese
instructionsfordetails.

TheATmega16U2(or8U2intherev1andrev2boards)firmwaresourcecodeis
availableintheArduinorepository.TheATmega16U2/8U2isloadedwithaDFU
bootloader,whichcanbeactivatedby:
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OnRev1boards:connectingthesolderjumperonthebackoftheboard(nearthemapof
Italy)andthenreseingthe8U2.
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OnRev2orlaterboards:thereisaresistorthatpullingthe8U2/16U2HWBlineto
ground,makingiteasiertoputintoDFUmode.
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YoucanthenuseAtmel'sFLIPsoftware(Windows)ortheDFUprogrammer(Mac
OSXandLinux)toloadanewfirmware.OryoucanusetheISPheaderwithan
externalprogrammer(overwritingtheDFUbootloader).Seethisuser‐contributed
tutorialformoreinformation.
Warnings
TheArduinoUnohasaresettablepolyfusethatprotectsyourcomputer'sUSBports
fromshortsandovercurrent.Althoughmostcomputersprovidetheirowninternal
protection,thefuseprovidesanextralayerofprotection.Ifmorethan500mAis
appliedtotheUSBport,thefusewillautomaticallybreaktheconnectionuntilthe
shortoroverloadisremoved.
Differenceswithotherboards
TheUnodiffersfromallprecedingboardsinthatitdoesnotusetheFTDIUSB‐to‐
serialdriverchip.Instead,itfeaturestheAtmega16U2(Atmega8U2uptoversion
R2)programmedasaUSB‐to‐serialconverter.
Power
TheArduinoUnoboardcanbepoweredviatheUSBconnectionorwithanexternal
powersupply.Thepowersourceisselectedautomatically.
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External(non‐USB)powercancomeeitherfromanAC‐to‐DCadapter(wall‐wart)or
battery.Theadaptercanbeconnectedbyplugginga2.1mmcenter‐positiveplug
intotheboard'spowerjack.LeadsfromabatterycanbeinsertedintheGNDand
VinpinheadersofthePOWERconnector.
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Theboardcanoperateonanexternalsupplyfrom6to20volts.Ifsuppliedwith
lessthan7V,however,the5Vpinmaysupplylessthanfivevoltsandtheboard
maybecomeunstable.Ifusingmorethan12V,thevoltageregulatormayoverheat
anddamagetheboard.Therecommendedrangeis7to12volts.

Thepowerpinsareasfollows:
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Vin.TheinputvoltagetotheArduino/Genuinoboardwhenit'susinganexternalpower
source(asopposedto5voltsfromtheUSBconnectionorotherregulatedpowersource).
Youcansupplyvoltagethroughthispin,or,ifsupplyingvoltageviathepowerjack,
accessitthroughthispin.
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5V.Thispinoutputsaregulated5Vfromtheregulatorontheboard.Theboardcanbe
suppliedwithpowereitherfromtheDCpowerjack(7‐12V),theUSBconnector(5V),or
theVINpinoftheboard(7‐12V).Supplyingvoltageviathe5Vor3.3Vpinsbypassesthe
regulator,andcandamageyourboard.Wedon'tadviseit.

3V3.A3.3voltsupplygeneratedbytheon‐boardregulator.Maximumcurrentdrawis50
mA.
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GND.Groundpins.
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IOREF.ThispinontheArduino/Genuinoboardprovidesthevoltagereferencewithwhich
themicrocontrolleroperates.AproperlyconfiguredshieldcanreadtheIOREFpinvoltage
andselecttheappropriatepowersourceorenablevoltagetranslatorsontheoutputsto
workwiththe5Vor3.3V.
Memory
TheATmega328has32KB(with0.5KBoccupiedbythebootloader).Italsohas2
KBofSRAMand1KBofEEPROM(whichcanbereadandwrittenwiththeEEPROM
library).
https://www.arduino.cc/en/Reference/EEPROM
InputandOutput
SeethemappingbetweenArduinopinsandATmega328Pports.Themappingfor
theAtmega8,168,and328isidentical.

PINMAPPINGATmega328P
https://www.arduino.cc/en/Hacking/PinMapping168
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Eachofthe14digitalpinsontheUnocanbeusedasaninputoroutput,
usingpinMode()https://www.arduino.cc/en/Reference/PinMode,
digitalWrite()https://www.arduino.cc/en/Reference/DigitalWrite,
anddigitalRead()https://www.arduino.cc/en/Reference/DigitalReadfunctions.
Theyoperateat5volts.Eachpincanprovideorreceive20mAasrecommended
operatingconditionandhasaninternalpull‐upresistor(disconnectedbydefault)
of20‐50kohm.Amaximumof40mAisthevaluethatmustnotbeexceededonany
I/Opintoavoidpermanentdamagetothemicrocontroller.

Inaddition,somepinshavespecializedfunctions:
Serial:0(RX)and1(TX).Usedtoreceive(RX)andtransmit(TX)TTLserialdata.These
pinsareconnectedtothecorrespondingpinsoftheATmega8U2USB‐to‐TTLSerialchip.

ExternalInterrupts:2and3.Thesepinscanbeconfiguredtotriggeraninterruptonalow
value,arisingorfallingedge,orachangeinvalue.SeetheattachInterrupt()functionfor
details.

PWM:3,5,6,9,10,and11.Provide8‐bitPWMoutputwiththeanalogWrite()function.

SPI:10(SS),11(MOSI),12(MISO),13(SCK).ThesepinssupportSPIcommunicationusing
theSPIlibrary.

LED:13.Thereisabuilt‐inLEDdrivenbydigitalpin13.WhenthepinisHIGHvalue,the
LEDison,whenthepinisLOW,it'soff.

TWI:A4orSDApinandA5orSCLpin.SupportTWIcommunicationusingtheWirelibrary.

TheUnohas6analoginputs,labeledA0throughA5,eachofwhichprovide10bits
ofresolution(i.e.1024differentvalues).Bydefaulttheymeasurefromgroundto5
volts,thoughisitpossibletochangetheupperendoftheirrangeusingtheAREF
pinandtheanalogReference()function.Thereareacoupleofotherpinsonthe
board:

AREF.Referencevoltagefortheanaloginputs.UsedwithanalogReference().

Reset.BringthislineLOWtoresetthemicrocontroller.Typicallyusedtoaddareset
buttontoshieldswhichblocktheoneontheboard.
Communication
Arduino/GenuinoUnohasanumberoffacilitiesforcommunicatingwitha
computer,anotherArduino/Genuinoboard,orothermicrocontrollers.The
ATmega328providesUARTTTL(5V)serialcommunication,whichisavailableon
digitalpins0(RX)and1(TX).AnATmega16U2ontheboardchannelsthisserial
communicationoverUSBandappearsasavirtualcomporttosoftwareonthe
computer.The16U2firmwareusesthestandardUSBCOMdrivers,andnoexternal
driverisneeded.However,onWindows,a.inffileisrequired.TheArduino
Software(IDE)includesaserialmonitorwhichallowssimpletextualdatatobe
senttoandfromtheboard.TheRXandTXLEDsontheboardwillflashwhendata
isbeingtransmittedviatheUSB‐to‐serialchipandUSBconnectiontothecomputer
(butnotforserialcommunicationonpins0and1).


ASoftwareSeriallibraryallowsserialcommunicationonanyoftheUno'sdigital
pins.
https://www.arduino.cc/en/Reference/SoftwareSerial

TheATmega328alsosupportsI2C(TWI)andSPIcommunication.TheArduino
Software(IDE)includesaWirelibrarytosimplifyuseoftheI2Cbus;see
thedocumentationfordetails.ForSPIcommunication,usetheSPIlibrary.
https://www.arduino.cc/en/Reference/Wire
https://www.arduino.cc/en/Reference/SPI
Automatic(Software)Reset
Ratherthanrequiringaphysicalpressoftheresetbuttonbeforeanupload,the
Arduino/GenuinoUnoboardisdesignedinawaythatallowsittoberesetby
softwarerunningonaconnectedcomputer.Oneofthehardwareflowcontrollines
(DTR)oftheATmega8U2/16U2isconnectedtotheresetlineoftheATmega328via
a100nanofaradcapacitor.Whenthislineisasserted(takenlow),theresetline
dropslongenoughtoresetthechip.TheArduinoSoftware(IDE)usesthis
capabilitytoallowyoutouploadcodebysimplypressingtheuploadbuttoninthe
interfacetoolbar.Thismeansthatthebootloadercanhaveashortertimeout,as
theloweringofDTRcanbewell‐coordinatedwiththestartoftheupload.
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Thissetuphasotherimplications.WhentheUnoisconnectedtoeitheracomputer
runningMacOSXorLinux,itresetseachtimeaconnectionismadetoitfrom
software(viaUSB).Forthefollowinghalf‐secondorso,thebootloaderisrunning
ontheUno.Whileitisprogrammedtoignoremalformeddata(i.e.anything
besidesanuploadofnewcode),itwillinterceptthefirstfewbytesofdatasentto
theboardafteraconnectionisopened.Ifasketchrunningontheboardreceives
one‐timeconfigurationorotherdatawhenitfirststarts,makesurethatthe
softwarewithwhichitcommunicateswaitsasecondafteropeningtheconnection
andbeforesendingthisdata.
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TheUnoboardcontainsatracethatcanbecuttodisabletheauto‐reset.Thepads
oneithersideofthetracecanbesolderedtogethertore‐enableit.It'slabeled
"RESET‐EN".Youmayalsobeabletodisabletheauto‐resetbyconnectinga110
ohmresistorfrom5Vtotheresetline;seethisforumthreadfordetails.
Revisions
Revision3oftheboardhasthefollowingnewfeatures:
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1.0pinout:addedSDAandSCLpinsthatareneartotheAREFpinandtwoothernewpins
placedneartotheRESETpin,theIOREFthatallowtheshieldstoadapttothevoltage

providedfromtheboard.Infuture,shieldswillbecompatiblewithboththeboardthat
usestheAVR,whichoperateswith5VandwiththeArduinoDuethatoperateswith3.3V.
Thesecondoneisanotconnectedpin,thatisreservedforfuturepurposes.
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StrongerRESETcircuit.
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Atmega16U2replacethe8U2.
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https://store.arduino.cc/usa/arduino‐uno‐rev312‐8‐17