A000057 Datasheet A000057 | P4-P6

ExternalInterrupts:3(interrupt0),2(interrupt1),0(interrupt2),1(interrupt3) and7

(interrupt4).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.

https://www.arduino.cc/en/Reference/AttachInterrupt



PWM:3,5,6,9,10,11, and13.Provide8‐bitPWMoutputwiththe analogWrite()

function.

https://www.arduino.cc/en/Reference/AnalogWrite



SPI:ontheICSPheader.These pinssupportSPIcommunicationusingtheSPI library.Note

thattheSPI pins are notconnectedtoanyofthedigitalI/O pinsastheyareontheUno,

TheyareonlyavailableontheICSP connector.Thismeansthatifyouhaveashieldthat

usesSPI,but does NOThavea 6‐ pinICSP connectorthatconnectsto the Leonardo's6‐pin

ICSPheader, theshieldwillnot work.

https://www.arduino.cc/en/Reference/SPI



LED:13. Thereisa built‐ inLED connectedtodigitalpin13.WhenthepinisHIGHvalue,

theLEDison,when the pinisLOW,it'soff.



AnalogInputs:A0‐A5,A6‐A11 (ondigital pins4,6,8,9,10, and12).TheLeonardohas

12analoginputs,labeledA0throughA11,allofwhichcanalsobeusedasdigitali/o.Pins

A0‐A5appearin thesamelocationsasontheUno;inputsA6‐A11areon digital i/opins4,

6,8,9,10,and12respectively.Eachanaloginput provide10bitsofresolution(i.e.1024

differentvalues).Bydefaultthe analoginputs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.

https://www.arduino.cc/en/Reference/AnalogReference



Thereareacoupleofotherpinsontheboard:



AREF.Referencevoltagefortheanaloginputs.UsedwithanalogReference().

https://www.arduino.cc/en/Reference/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.



SeealsothemappingbetweenArduinopinsandATmega32u4ports.

https://www.arduino.cc/en/Hacking/PinMapping32u4

Communication

TheLeonardohasanumberoffacilitiesforcommunicatingwithacomputer,

anotherArduino,orothermicrocontrollers.TheATmega32U4providesUARTTTL

(5V)serialcommunication,whichisavailable ondigitalpins0(RX)and1(TX).The

32U4alsoallowsforserial(CDC)communicationoverUSBandappearsasavirtual

comporttosoftwareonthecomputer.ThechipalsoactsasafullspeedUSB2.0

device,usingstandardUSBCOMdrivers.OnWindows,a.inffileisrequired.The

Arduinosoftwareincludesaserialmonitorwhichallowssimpletextualdatatobe

senttoandfromtheArduinoboard.TheRXandTXLEDsontheboardwillflash

whendataisbeingtransmittedviatheUSBconnectiontothecomputer(butnot

forserialcommunicationonpins0and1).ASoftwareSeriallibraryallowsforserial

communicationonanyoftheLeonardo'sdigitalpins.TheATmega32U4also

supportsI2C(TWI)andSPIcommunication.TheArduinosoftwareincludesaWire

librarytosimplifyuseoftheI2Cbus;seethedocumentationfordetails.

http://www.arduino.cc/en/Reference/SoftwareSerial

https://www.arduino.cc/en/Reference/Wire



ForSPIcommunication,usetheSPIlibrary.TheLeonardoappearsasageneric

keyboardandmouse,andcanbeprogrammedtocontroltheseinputdevicesusing

theKeyboardandMouseclasses.

https://www.arduino.cc/en/Reference/SPI

Programming

TheLeonardocanbeprogrammedwiththeArduinosoftware(download). Select

"ArduinoLeonardofromtheTools>Boardmenu(accordingtothemicrocontroller

onyourboard).Fordetails,seethereferenceandtutorials.TheATmega32U4on

theArduinoLeonardocomespreburnedwithabootloaderthatallowsyouto

uploadnewcodetoitwithouttheuseofanexternalhardwareprogrammer.It

communicatesusingtheAVR109protocol.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.

https://www.arduino.cc/en/Main/Software

https://www.arduino.cc/en/Hacking/Programmer

Automatic(Software)ResetandBootloaderInitiation

Ratherthanrequiringaphysicalpressoftheresetbuttonbeforeanupload,the

Leonardoisdesignedina waythatallowsittoberesetbysoftwarerunningona

connectedcomputer.TheresetistriggeredwhentheLeonardo'svirtual(CDC)

serial/COMportisopenedat1200baudandthenclosed.Whenthishappens,the

processorwillreset,breakingtheUSBconnectiontothecomputer(meaningthat

thevirtualserial/COMportwilldisappear).Aftertheprocessorresets,the

bootloaderstarts,remainingactiveforabout8seconds.Thebootloadercanalso

beinitiatedbypressingtheresetbuttonontheLeonardo.Notethatwhenthe

boardfirstpowersup,itwilljumpstraighttotheusersketch,ifpresent,rather

thaninitiatingthebootloader.



BecauseofthewaytheLeonardohandlesresetit'sbesttolettheArduino

softwaretrytoinitiatetheresetbeforeuploading,especiallyifyouareinthe

habitofpressingtheresetbuttonbeforeuploadingonotherboards.Ifthe

softwarecan'tresettheboardyoucanalwaysstartthebootloaderbypressingthe

resetbuttonontheboard.

USBOvercurrentProtection

TheLeonardo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.

PhysicalCharacteristics

ThemaximumlengthandwidthoftheLeonardoPCBare2.7and2.1inches

respectively,withtheUSBconnectorandpowerjackextendingbeyondtheformer

dimension.Fourscrewholesallowtheboardtobeattachedtoasurfaceorcase.

Notethatthedistancebetweendigitalpins7and8is160mil(0.16"),notaneven

multipleofthe100milspacingoftheotherpins.



https://store.arduino.cc/usa/arduino‐leonardo‐with‐headers12‐7‐17

P1-P3 P4-P6

A000057

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