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ARDUINOUNOREV3SMD
Code:A000073
The board everybody gets started with, based on the
ATmega328 (SMD).
TheArduinoUnoSMDR3isamicrocontrollerboardbasedontheATmega328.Ithas
14digitalinput/outputpins(ofwhich6canbeusedasPWMoutputs),6analog
inputs,a16MHzcrystaloscillator,aUSBconnection,apowerjack,anICSPheader,
andaresetbutton.Itcontainseverythingneededtosupportthemicrocontroller;
simplyconnectittoacomputerwithaUSBcableorpoweritwithaACtoDCadapter
orbatterytogetstarted.
TheUnodiffersfromallprecedingboardsinthatitdoesnotusetheFTDIUSBto
serialdriverchip.
AdditionalfeaturescomingwiththeR3versionare:
‐ATmega16U2instead8U2asUSBtoSerialconverter.
‐1.0pinout:addedSDAandSCLpinsforTWIcommunicationplacedneartotheAREF
pinandtwoothernewpinsplacedneartotheRESETpin,theIOREFthatallowthe
shieldstoadapttothevoltageprovidedfromtheboardandthesecondoneisanot
connectedpin,thatisreservedforfuturepurposes.
‐strongerRESETcircuit.
"Uno"means"One"inItalianandisnamedtomarktheupcomingreleaseofArduino
1.0.TheUnoandversion1.0willbethereferenceversionsofArduino,moving
forward.TheUnoisthelatestinaseriesofUSBArduinoboards,andthereference
modelfortheArduinoplatform.
TECH SPECS
MicrocontrollerATmega328P
OperatingVoltage5V
InputVoltage(recommended)712V
InputVoltage(limit)620V
DigitalI/OPins14(ofwhich6providePWMoutput)
PWMDigitalI/OPins6
AnalogInputPins6
DCCurrentperI/OPin20mA
DCCurrentfor3.3VPin50mA
FlashMemory32KB(ATmega328P)ofwhich0.5KBusedbybootloader
SRAM2KB(ATmega328P)
EEPROM1KB(ATmega328P)
Arduino Uno is open-source hardware! You can build your own board using the
ClockSpeed16MHz
LED_BUILTIN13
Length68.6mm
Width53.4mm
Weight25g
OSH:Schematics
ArduinoUnoisopen‐sourcehardware!Youcanbuildyourownboardusingthe
follwingfiles:
EAGLE FILES IN .ZIP
https://www.arduino.cc/en/uploads/Main/arduinounosmdreferencedesign.zip
SCHEMATICSIN.PDF
https://www.arduino.cc/en/uploads/Main/arduinounosmdschematic.pdf
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.
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).
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:
OnRev1boards:connectingthesolderjumperonthebackoftheboard(nearthemapof
Italy)andthenreseingthe8U2.
OnRev2orlaterboards:thereisaresistorthatpullingthe8U2/16U2HWBlinetoground,
makingiteasiertoputintoDFUmode.
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.
Differenceswithotherboards
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.
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.
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:
Vin.TheinputvoltagetotheArduino/Genuinoboardwhenit'susinganexternalpower
source(asopposedto5voltsfromtheUSBconnectionorotherregulatedpowersource).
Youcansupplyvoltagethroughthispin,or,ifsupplyingvoltageviathepowerjack,access
itthroughthispin.
5V.Thispinoutputsaregulated5Vfromtheregulatorontheboard.Theboardcanbe
suppliedwithpowereitherfromtheDCpowerjack(7‐12V),theUSBconnector(5V),orthe
VINpinoftheboard(712V).Supplyingvoltageviathe5Vor3.3Vpinsbypassesthe
regulator,andcandamageyourboard.Wedon'tadviseit.
3V3.A3.3voltsupplygeneratedbytheonboardregulator.Maximumcurrentdrawis50
mA.
GND.Groundpins.
IOREF.ThispinontheArduino/Genuinoboardprovidesthevoltagereferencewithwhich
themicrocontrolleroperates.AproperlyconfiguredshieldcanreadtheIOREFpinvoltage
andselecttheappropriatepowersourceorenablevoltagetranslatorsontheoutputsto
workwiththe5Vor3.3V.
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).
InputandOutput
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
Each of the 14 digital pins on the Uno can be used as an input or output,
using pinMode(),digitalWrite(), and 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.
Inaddition,somepinshavespecializedfunctions:
Serial:0(RX)and1(TX).Usedtoreceive(RX)andtransmit(TX)TTLserialdata.Thesepins
areconnectedtothecorrespondingpinsoftheATmega8U2USBtoTTLSerialchip.
ExternalInterrupts:2and3.Thesepinscanbeconfiguredtotriggeraninterruptonalow
value,arisingorfallingedge,orachangeinvalue.SeetheattachInterrupt()functionfor
details.
PWM:3,5,6,9,10,and11.Provide8bitPWMoutputwiththeanalogWrite()function.
SPI:10(SS),11(MOSI),12(MISO),13(SCK).ThesepinssupportSPIcommunicationusing
theSPIlibrary.
LED:13.ThereisabuiltinLEDdrivenbydigitalpin13.WhenthepinisHIGHvalue,theLED
ison,whenthepinisLOW,it'soff.
TWI:A4orSDApinandA5orSCLpin.SupportTWIcommunicationusingtheWirelibrary.
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.Referencevoltagefortheanaloginputs.UsedwithanalogReference().
Reset.BringthislineLOWtoresetthemicrocontroller.Typicallyusedtoaddaresetbutton
toshieldswhichblocktheoneontheboard.
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.
Automatic(Software)Reset
Ratherthanrequiringaphysicalpressoftheresetbuttonbeforeanupload,the
Arduino/GenuinoUnoboardisdesignedinawaythatallowsittoberesetbysoftware
runningonaconnectedcomputer.Oneofthehardwareflowcontrollines(DTR)ofthe
ATmega8U2/16U2isconnectedtotheresetlineoftheATmega328viaa100nanofarad
capacitor.Whenthislineisasserted(takenlow),theresetlinedropslongenoughtoreset
thechip.TheArduinoSoftware(IDE)usesthiscapabilitytoallowyoutouploadcodeby
simplypressingtheuploadbuttonintheinterfacetoolbar.Thismeansthatthebootloader
canhaveashortertimeout,astheloweringofDTRcanbewellcoordinatedwiththestart
oftheupload.
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.
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:
1.0pinout:addedSDAandSCLpinsthatareneartotheAREFpinandtwoothernewpins
placedneartotheRESETpin,theIOREFthatallowtheshieldstoadapttothevoltage
providedfromtheboard.Infuture,shieldswillbecompatiblewithboththeboardthatuses
theAVR,whichoperateswith5VandwiththeArduinoDuethatoperateswith3.3V.The
secondoneisanotconnectedpin,thatisreservedforfuturepurposes.
StrongerRESETcircuit.
Atmega16U2replacethe8U2.
https://store.arduino.cc/usa/arduinounosmdrev312617

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