Main.ArduinoBoardUno History

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August 03, 2015, at 05:46 PM by Ramona Banfi -
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August 03, 2015, at 05:08 PM by Ramona Banfi -
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August 03, 2015, at 04:34 PM by Ramona Banfi -
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August 03, 2015, at 03:48 PM by Ramona Banfi -
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          You can find <a href="">here</a> your board warranty informations.
to:
          You can find <a href="/en/Main/warranty">here</a> your board warranty informations.
August 03, 2015, at 03:46 PM by Ramona Banfi -
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started with electronics and coding. If this is your first experience with Arduino, 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.

to:

started with electronics and coding. If this is your first experience with Arduino, 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.

August 03, 2015, at 03:46 PM by Ramona Banfi -
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started with electronics and coding. If this is your first experience with Arduino, 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.

to:

started with electronics and coding. If this is your first experience with Arduino, 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.

August 03, 2015, at 03:45 PM by Ramona Banfi -
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Arduino/Genuino UNO is the best board to get started with electronics and coding. If this is your first experience with Arduino, the UNO is the most robust board you can start playing with. The UNO is the most used and

to:

Arduino/Genuino UNO is the best board to get started with electronics and coding. If this is your first experience with Arduino, the UNO is the most robust board you can start playing with. The UNO is the most used and

August 03, 2015, at 03:44 PM by Ramona Banfi -
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to get started with electronics and coding. If this is your first experience with Arduino, 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.

to:

to get started with electronics and coding. If this is your first experience with Arduino, 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.

August 03, 2015, at 03:43 PM by Ramona Banfi -
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Arduino/Genuino UNO is the best board to get started with electronics and coding. If this is your first experience with Arduino, 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.

to:

Arduino/Genuino UNO is the best board to get started with electronics and coding. If this is your first experience with Arduino, 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.

August 03, 2015, at 03:41 PM by Ramona Banfi -
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<a href="http://store-usa.arduino.cc/products/a000066" rel="nofollow"><button class="button blue-button">BUY ON STORE</button></a>

to:

<div class="product-page">

  <div class="subHeader row">

    <div class="breadcrumb columns large-10 medium-10">
      <p>
        <a class="wikilink" href="/en/Main/Products">Arduino Products</a>
        > Arduino/Genuino UNO
      </p>
    </div>

  </div>

<div class="product-page-header">

  <img class="header-image" src="/en/uploads/Main/ArdGen_UNO.jpg">

  <div class="text-column">
    <div class="titolo">Arduino / Genuino UNO</div>
    <div class="description">

Arduino/Genuino UNO is the best board to get started with electronics and coding. If this is your first experience with Arduino, 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.

    </div>
  </div>

  <div class="buttons">
    <a href="/en/Guide/HomePage" rel="nofollow"><button class="button blue-button">GETTING STARTED</button></a>
    <a href="http://store-usa.arduino.cc/products/a000066" rel="nofollow"><button class="button orange-button">SHOP NOW</button></a>
  </div>

</div>

<div class="row">

  <div class="large-2 medium-2 columns menu">
    <ul class="product-page-nav">
      <li><a href="#overview">Overview</a></li>
      <li><a href="#techspecs">Technical Specs</a></li>
      <li><a href="#documentation">Documentation</a></li>
    </ul>
  </div>

  <div class="large-10 medium-10 columns">

    <div id="overview">
      <div class="title1margintop">Overview</div>

      <div class="box red">5V</div>
      <div class="box orange">8-bit</div>
      <div class="box brown">16 MHz</div>
      <div class="box blue">AVR</div>

      <div class="textsummary">

        <div>
          Arduino/Genuino Uno is a microcontroller board based on the ATmega328P (<a href="http://www.atmel.com/Images/doc8161.pdf">datasheet</a>). 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.
        </div>
        <div>
          "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.
        </div>
        <div>
          You can find <a href="">here</a> your board warranty informations.
        </div>
        <div>
          <div class="subtitle">Getting Started</div>
          You can find in the <a href="/en/Guide/HomePage">Getting Started section</a> all the information you need to configure your board,
          use the Arduino So ftware (IDE), and start tinker with coding and electronics.
        </div>
        <div>
          <div class="subtitle">Need Help?</div>
          <ul class="textindent">
              <li>On the Software <a href="https://forum.arduino.cc/index.php?board=63.0">on the Arduino Forum</a></li>
              <li>On Projects <a href="https://forum.arduino.cc/index.php?board=3.0">on the Arduino Forum</a></li>
              <li>On the Product itself through <a href="https://store.arduino.cc/index.php?main_page=contact_us&language=en">our Customer Support</a></li>
          </ul>
        </div>
       </div>
      </div>

    <div id="techspecs">
      <div class="title1margintop">Technical specs</div>
      <div class="textsummary">
        <table>
          <tbody>

            <tr>
              <td>Microcontroller</td>
              <td><a href="http://www.atmel.com/Images/doc8161.pdf">ATmega328P</a></td>
            </tr>

            <tr>
                <td>Operating Voltage</td>
                <td>5V</td>
              </tr>

              <tr>
                <td>Input Voltage (recommended)</td>
                <td>7-12V</td>
              </tr>

              <tr>
                <td>Input Voltage (limit)</td>
                <td>6-20V</td>
              </tr>

              <tr>
                <td>Digital I/O Pins</td>
                <td>14 (of which 6 provide PWM output)</td>
              </tr>

              <tr>
                <td>PWM Digital I/O Pins</td>
                <td>6</td>
              </tr>

              <tr>
                <td>Analog Input Pins</td>
                <td>6</td>
              </tr>

              <tr>
                <td>DC Current per I/O Pin</td>
                <td>20 mA</td>
              </tr>

              <tr>
                <td>DC Current for 3.3V Pin</td>
                <td>50 mA</td>
              </tr>

              <tr>
                <td>Flash Memory</td>
                <td>32 KB (ATmega328P)<br> of which 0.5 KB used by bootloader</td>
              </tr>

              <tr>
                <td>SRAM</td>
                <td>2 KB (ATmega328P)</td>
              </tr>

              <tr>
                <td>EEPROM</td>
                <td>1 KB (ATmega328P)</td>
              </tr>

              <tr>
                <td>Clock Speed</td>
                <td>16 MHz</td>
              </tr>

              <tr>
                <td>Length</td>
                <td>68.6 mm</td>
              </tr>

              <tr>
                <td>Width</td>
                <td>53.4 mm</td>
              </tr>

              <tr>
                <td>Weight</td>
                <td>25 g</td>
              </tr>

          </tbody>
        </table>

      </div>
    </div>

    <div id="documentation">
      <div class="title1margintop">Documentation</div>
      <div class="textsummary">

        <div>
        <div class="subtitle">OSH: Schematics, Reference Design, Board size</div>
        Arduino / Genuino Uno is open-source hardware! You can build your own board using the follwing files:
        </div>

        <a href="/en/uploads/Main/arduino_Uno_Rev3-02-TH.zip"><div class="rectdocumentation yellow"><div class="immrect"><img src="/en/uploads/Main/eaglefile.svg" alt="EAGLE" style="width:64px; height:47px;"></div><div class="textrect">EAGLE FILES<br> IN .ZIP</div> </div></a>
        <a href="/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf"><div class="rectdocumentation brown"><div class="immrect"><img src="/en/uploads/Main/schematicsfile.svg" alt="PDF" style="width:48px; height:48px;"></div><div class="textrect margin">SCHEMATICS<br> IN .PDF</div></div></a>
        <a href="http://arduino.cc/documents/Arduino%20Uno.dxf"><div class="rectdocumentation orange"><div class="immrect"><img src="/en/uploads/Main/boardsizefile.svg" alt="DXF" style="width:79px; height:48px;"></div><div class="textrect margintwo">BOARD SIZE<br> IN .DXF</div></div></a>

        <div>
        <div class="subtitle">Programming</div>
        The Arduino/Genuino Uno can be programmed with the (<a href="/en/Main/Software">Arduino Software</a> (IDE)). Select "Arduino/Genuino Uno from
        the Tools > Board menu (according to the microcontroller on your board). For details, see the <a href="/en/Reference/HomePage">reference</a> and <a href="/en/Tutorial/HomePage">tutorials</a>.
        </div>

        <div>
        The ATmega328 on the Arduino/Genuino Uno comes preprogrammed with a <a href="/en/Hacking/Bootloader?from=Tutorial.Bootloader">bootloader</a> that allows you to upload new code to it without
        the use of an external hardware programmer. It communicates using the original STK500 protocol (<a href="http://www.atmel.com/Images/doc2525.pdf">reference</a>, <a href="http://www.atmel.com/dyn/resources/prod_documents/avr061.zip">C header files</a>).
        </div>

        <div>
        You can also bypass the bootloader and program the microcontroller through the ICSP (In-Circuit Serial Programming) header using
        <a href="/en/Main/ArduinoISP">Arduino ISP</a> or similar; see <a href="/en/Hacking/Programmer">these instructions</a> for details.
        </div>

        <div>
        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:
        <ul class="textindent">
          <li>On Rev1 boards: connecting the solder jumper on the back of the board (near the map of Italy) and then rese ing the 8U2.</li>
          <li>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.</li>
        </ul>
        </div>

        <div>
        You can then use <a href="http://www.atmel.com/products/microcontrollers/default.aspx">Atmel's FLIP software </a>(Windows) or the <a href="http://dfu-programmer.github.io/">DFU programmer</a> (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 <a href="http://forum.arduino.cc/index.php/topic,111.0.html">this user-contributed tutorial</a> for more information.
        </div>

        <div>
        <div class="subtitle">Warnings</div>
        The Arduino/Genuino 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.
        </div>

        <div>
        <div class="subtitle">Differences with other boards</div>
        The Uno di ers 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.
        </div>

        <div>
        <div class="subtitle">Power</div>
        The Arduino/Genuino Uno board can be powered via the USB connection or with an external power supply. The power source is selected
        automatically.
        </div>
        <div>
        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.
        </div>
        <div>
        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.
        </div>

        <div>
        The power pins are as follows:<br>
        <ul class="textindent">
        <li> 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.</li>
        <li>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.</li>
        <li>3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.</li>
        <li>GND. Ground pins.</li>
        <li>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.</li>
        </ul>
        </div>

        <div>
        <div class="subtitle">Memory</div>
        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 <a href="/en/Reference/EEPROM">EEPROM library</a>).
        </div>

        <div>
        <div class="subtitle">Input and Output</div></div>
        <div>
        See the mapping between Arduino pins and ATmega328P ports. The mapping for the Atmega8, 168, and 328 is identical.</div>
        <a href="/en/Hacking/PinMapping168"><div class="rectdocumentation green"><div class="immrect"><img src="/en/uploads/Main/pin_mapping.svg" alt="PIN_MAPPING" style="width:55px; height:46px;"></div><div class="textrect">PIN MAPPING<br>ATmega328P</div> </div></a>
        <div>
        Each of the 14 digital pins on the Uno can be used as an input or output, using <a href="/en/Reference/PinMode">pinMode()</a>, <a href="/en/Reference/DigitalWrite">digitalWrite()</a>, and <a href="/en/Reference/DigitalRead">digitalRead()</a> 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.
        </div>

        <div>
        In addition, some pins have specialized functions:<br>
        <ul class="textindent">
        <li>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.</li>
        <li>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.</li>
        <li>PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output with the analogWrite() function.</li>
        <li>SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication using the SPI library.</li>
        <li>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.</li>
        <li>TWI: A4 or SDA pin and A5 or SCL pin. Support TWI communication using the Wire library.</li></ul></div>

        <div>
        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.<br>
        There are a couple of other pins on the board:<br>
        <ul class="textindent">
        <li>AREF. Reference voltage for the analog inputs. Used with analogReference().</li>
        <li>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.</li>
        </ul>
        </div>

        <div>
        <div class="subtitle">Communication</div>
        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, <a href="/en/Guide/Windows#toc4">on Windows, a .inf file is required</a>. 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).
        </div>

        <div>
        A <a href="/en/Reference/SoftwareSerial">SoftwareSerial library</a> allows serial communication on any of the Uno's digital pins.
        </div>

        <div>
        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 <a href="/en/Reference/Wire">documentation</a> for details. For SPI communication, use the <a href="/en/Reference/SPI">SPI library</a>.
        </div>

        <div>
        <div class="subtitle">Automatic (Software) Reset</div>
        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.
        </div>

        <div>
        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.
        </div>

        <div>
        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 <a href="http://forum.arduino.cc/index.php/topic,22974.0.html">this forum
        thread</a> for details.
        </div>

        <div>
          <div class="subtitle">Revisions</div>
          Revision 3 of the board has the following new features:<br>
          <ul class="textindent">
            <li>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.</li>
            <li>Stronger RESET circuit.</li>
            <li>Atmega 16U2 replace the 8U2.</li>
          </ul>
        </div>

      </div>
    </div>

  </div>

</div>

</div>

Deleted lines 381-520:
July 24, 2015, at 02:23 PM by Simone Maiocchi -
Changed line 136 from:

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:

to:

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:

July 24, 2015, at 01:44 PM by Simone Maiocchi -
Changed lines 91-92 from:

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).

to:

The ATmega328P 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).

Changed lines 97-98 from:
  • 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.
to:
  • 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/ATmega16U2 USB-to-TTL Serial chip.
Changed lines 122-123 from:

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).

to:

Arduino/Genuino Uno has a number of facilities for communicating with a computer, another Arduino/Genuino board, or other microcontrollers. The ATmega328P 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).

Changed lines 126-127 from:

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.

to:

The ATmega328P 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.

Changed lines 132-133 from:

The ATmega328 on the Arduino/Genuino 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).

to:

The ATmega328P on the Arduino/Genuino 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).

Changed lines 143-144 from:

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.

to:

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 ATmega328P 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.

July 24, 2015, at 01:41 PM by Simone Maiocchi -
Changed lines 52-54 from:
Flash Memory32 KB (ATmega328) of which 0.5 KB used by bootloader
SRAM2 KB (ATmega328)
EEPROM1 KB (ATmega328)
to:
Flash Memory32 KB (ATmega328P) of which 0.5 KB used by bootloader
SRAM2 KB (ATmega328P)
EEPROM1 KB (ATmega328P)
Changed lines 67-68 from:

Note: The Arduino reference design can use an Atmega8, 168, or 328, Current models use an ATmega328, but an Atmega8 is shown in the schematic for reference. The pin configuration is identical on all three processors.

to:

Note: The Arduino reference design can use an Atmega8, 168, or 328, Current models use an ATmega328P, but an Atmega8 is shown in the schematic for reference. The pin configuration is identical on all three processors.

July 24, 2015, at 11:21 AM by Simone Maiocchi -
Changed line 50 from:
DC Current per I/O Pin40 mA
to:
DC Current per I/O Pin20 mA
July 24, 2015, at 11:20 AM by Simone Maiocchi -
Changed lines 30-31 from:

Arduino/Genuino Uno is a microcontroller board based on the ATmega328 (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.

to:

Arduino/Genuino 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.

Changed line 44 from:
MicrocontrollerATmega328
to:
MicrocontrollerATmega328P
July 24, 2015, at 11:19 AM by Simone Maiocchi -
Changed lines 95-96 from:

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 40 mA as recommended operating condition and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. In addition, some pins have specialized functions:

to:

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. In addition, some pins have specialized functions:

July 23, 2015, at 03:49 PM by Simone Maiocchi -
Changed lines 39-40 from:

"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 past or outdated boards see the index of Arduino historic boards.

to:

"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.

July 23, 2015, at 03:47 PM by Simone Maiocchi -
Changed lines 39-40 from:

"Uno" means one in Italian and was chosen to mark the release of Arduino 1.0 Software (IDE). The Uno and version 1.0 were the reference versions of Arduino, now evolved to newer releases. The Uno is the first in a series of USB Arduino boards, and the reference model for the Arduino platform; for an extensive list of past or outdated boards see the index of Arduino historic boards.

to:

"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 past or outdated boards see the index of Arduino historic boards.

July 23, 2015, at 03:45 PM by Simone Maiocchi -
Changed lines 147-148 from:

The Uno 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.

to:

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.

Changed lines 151-152 from:

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.

to:

The Arduino/Genuino 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.

July 23, 2015, at 03:43 PM by Simone Maiocchi -
Changed lines 143-144 from:

Rather than requiring a physical press of the reset button before an upload, the Arduino Uno 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 uses this capability to allow you to upload code by simply pressing the upload button in the Arduino environment. 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.

to:

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.

July 23, 2015, at 03:41 PM by Simone Maiocchi -
Changed lines 130-133 from:

The Arduino/Genuino Uno can be programmed with the Arduino software (download). Select "Arduino 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 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 original STK500 protocol (reference, C header files).

to:

The Arduino/Genuino 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/Genuino 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).

Changed line 136 from:

The ATmega16U2 (or 8U2 in the rev1 and rev2 boards) firmware source code is available . The ATmega16U2/8U2 is loaded with a DFU bootloader, which can be activated by:

to:

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:

July 23, 2015, at 03:37 PM by Simone Maiocchi -
Changed lines 122-127 from:

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 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-to-serial chip and 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 Uno's digital pins.

The ATmega328 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. For SPI communication, use the SPI library.

to:

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.

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.

Changed lines 130-131 from:

The Arduino Uno can be programmed with the Arduino software (download). Select "Arduino Uno from the Tools > Board menu (according to the microcontroller on your board). For details, see the reference and tutorials.

to:

The Arduino/Genuino Uno can be programmed with the Arduino software (download). Select "Arduino Uno from the Tools > Board menu (according to the microcontroller on your board). For details, see the reference and tutorials.

July 23, 2015, at 03:34 PM by Simone Maiocchi -
Deleted lines 106-107:

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. Additionally, some pins have specialized functionality:

Added lines 109-111:

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.

Changed lines 122-123 from:

The Arduino Uno has a number of facilities for communicating with a computer, another Arduino, 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 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-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

to:

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 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-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

July 23, 2015, at 03:30 PM by Simone Maiocchi -
Changed lines 95-96 from:

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 a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. In addition, some pins have specialized functions:

to:

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 40 mA as recommended operating condition and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. In addition, some pins have specialized functions:

Changed lines 105-106 from:
  • 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.
to:
  • 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.
July 23, 2015, at 03:25 PM by Simone Maiocchi -
Changed lines 91-92 from:

The ATmega328 has 32 KB (with 0.5 KB used for the bootloader). It also has 2 KB of SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library).

to:

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).

July 23, 2015, at 03:22 PM by Simone Maiocchi -
July 23, 2015, at 03:19 PM by Simone Maiocchi -
Changed lines 79-80 from:
  • VIN. The input voltage to the Arduino 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.
to:
  • 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.
Changed lines 87-88 from:
  • IOREF. This pin on the Arduino 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 for working with the 5V or 3.3V.
to:
  • 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.
July 23, 2015, at 03:15 PM by Simone Maiocchi -
Changed lines 75-76 from:

The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

to:

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.

July 23, 2015, at 03:13 PM by Simone Maiocchi -
Changed lines 39-40 from:

"Uno" means one in Italian and was chosen to mark the release of Arduino 1.0 Software (IDE). The Uno and version 1.0 were the reference versions of Arduino, now evolved to newer releases. The Uno is the first in a series of USB Arduino boards, and the reference model for the Arduino platform; for an extensive list of past and outdated boards see the index of Arduino historic boards.

to:

"Uno" means one in Italian and was chosen to mark the release of Arduino 1.0 Software (IDE). The Uno and version 1.0 were the reference versions of Arduino, now evolved to newer releases. The Uno is the first in a series of USB Arduino boards, and the reference model for the Arduino platform; for an extensive list of past or outdated boards see the index of Arduino historic boards.

Changed lines 71-74 from:

The Arduino Uno 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.

to:

The Arduino/Genuino 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.

July 23, 2015, at 03:09 PM by Simone Maiocchi -
Changed lines 39-40 from:

"Uno" means one in Italian and was chosen to mark the release of Arduino 1.0 Software (IDE). The Uno and version 1.0 were the reference versions of Arduino, now evolved to newer releases. The Uno is the part of a series of USB Arduino boards, and the reference model for the Arduino platform; for an extensive list of past and outdated boards see the index of Arduino historic boards.

to:

"Uno" means one in Italian and was chosen to mark the release of Arduino 1.0 Software (IDE). The Uno and version 1.0 were the reference versions of Arduino, now evolved to newer releases. The Uno is the first in a series of USB Arduino boards, and the reference model for the Arduino platform; for an extensive list of past and outdated boards see the index of Arduino historic boards.

July 23, 2015, at 03:08 PM by Simone Maiocchi -
Changed lines 30-31 from:

The Arduino Uno is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator, 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.

to:

Arduino/Genuino Uno is a microcontroller board based on the ATmega328 (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.

Changed lines 39-40 from:

"Uno" means one in Italian and is named to mark the upcoming release of Arduino 1.0. The Uno and version 1.0 will be the reference versions of Arduino, moving forward. The Uno is the latest in a series of USB Arduino boards, and the reference model for the Arduino platform; for a comparison with previous versions, see the index of Arduino boards.

to:

"Uno" means one in Italian and was chosen to mark the release of Arduino 1.0 Software (IDE). The Uno and version 1.0 were the reference versions of Arduino, now evolved to newer releases. The Uno is the part of a series of USB Arduino boards, and the reference model for the Arduino platform; for an extensive list of past and outdated boards see the index of Arduino historic boards.

July 09, 2015, at 04:57 PM by Alice Pintus -
Changed line 25 from:

<a href="http://store.arduino.cc/index.php?main_page=product_info&cPath=11&products_id=195" rel="nofollow"><button class="button blue-button">BUY ON STORE</button></a>

to:

<a href="http://store-usa.arduino.cc/products/a000066" rel="nofollow"><button class="button blue-button">BUY ON STORE</button></a>

Changed lines 27-32 from:
to:
January 20, 2015, at 12:45 PM by Stefania Mellai -
Changed lines 25-27 from:

<a href="http://store.arduino.cc/index.php?main_page=product_info&cPath=11&products_id=195" rel="nofollow"><button class="button" style="

    text-transform: uppercase; background-color: #00979C; color: #ffffff; border: 0; box-shadow: 0 6px #005c5f; top: 0px; position: relative; font-size: 15px; -webkit-transition: all ease-out .1s; -moz-transition: all ease-out .1s; -o-transition: all ease-out .1s; transition: all ease-out .1s;

">BUY ON STORE</button></a>

to:

<a href="http://store.arduino.cc/index.php?main_page=product_info&cPath=11&products_id=195" rel="nofollow"><button class="button blue-button">BUY ON STORE</button></a>

Changed lines 29-30 from:

<a href="http://arduino.cc/en/Main/Buy" rel="nofollow"><button style="text-transform: uppercase; background-color: #00979C; color: #ffffff; border: 0; box-shadow: 0 6px #005c5f; top: 0px; position: relative; font-size: 15px; -webkit-transition: all ease-out .1s; -moz-transition: all ease-out .1s; -o-transition: all ease-out .1s; transition: all ease-out .1s; margin-left: -1em; " class="button">Buy From Distributors</button></a>

to:

<a href="http://arduino.cc/en/Main/Buy" rel="nofollow"><button class="button blue-button">BUY FROM DISTRIBUTORS</button></a>

January 19, 2015, at 11:05 AM by Stefania Mellai -
Changed line 25 from:

<button class="button" href="http://store.arduino.cc/index.php?main_page=product_info&cPath=11&products_id=195" rel="nofollow" style="

to:

<a href="http://store.arduino.cc/index.php?main_page=product_info&cPath=11&products_id=195" rel="nofollow"><button class="button" style="

Changed line 27 from:

">BUY ON STORE</button>

to:

">BUY ON STORE</button></a>

Changed lines 31-32 from:

<button style="text-transform: uppercase; background-color: #00979C; color: #ffffff; border: 0; box-shadow: 0 6px #005c5f; top: 0px; position: relative; font-size: 15px; -webkit-transition: all ease-out .1s; -moz-transition: all ease-out .1s; -o-transition: all ease-out .1s; transition: all ease-out .1s; margin-left: -1em; " class="button" href="http://arduino.cc/en/Main/Buy" rel="nofollow">Buy From Distributors</button>

to:

<a href="http://arduino.cc/en/Main/Buy" rel="nofollow"><button style="text-transform: uppercase; background-color: #00979C; color: #ffffff; border: 0; box-shadow: 0 6px #005c5f; top: 0px; position: relative; font-size: 15px; -webkit-transition: all ease-out .1s; -moz-transition: all ease-out .1s; -o-transition: all ease-out .1s; transition: all ease-out .1s; margin-left: -1em; " class="button">Buy From Distributors</button></a>

December 12, 2014, at 01:12 PM by Alice Pintus -
Changed lines 24-28 from:
to:
Changed lines 30-33 from:
to:
September 22, 2014, at 04:25 PM by Angelo Scialabba -
Changed lines 57-58 from:
to:
Length68.6 mm
Width53.4 mm
Weight25 g

September 04, 2014, at 04:15 PM by Arturo -
Changed lines 131-132 from:

You can also bypass the bootloader and program the microcontroller through the ICSP (In-Circuit Serial Programming) header; see these instructions for details.

to:

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.

August 19, 2014, at 02:14 PM by Roberto Guido - added crazyegg script
Added lines 154-162:
June 23, 2014, at 06:13 PM by Angelo Scialabba -
Deleted lines 22-23:
Added lines 24-25:
June 23, 2014, at 06:13 PM by Angelo Scialabba -
Changed line 23 from:
to:
June 23, 2014, at 06:13 PM by Angelo Scialabba -
Changed lines 23-26 from:
to:
June 23, 2014, at 06:11 PM by Angelo Scialabba -
Changed lines 23-24 from:
to:
June 25, 2013, at 12:18 PM by Roberto Guido - typo errors. Thanks Robin StrĂ¼big for the feedback
Changed line 34 from:
  • 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 both with the board that use the AVR, which operate with 5V and with the Arduino Due that operate with 3.3V. The second one is a not connected pin, that is reserved for future purposes.
to:
  • 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.
January 28, 2013, at 07:46 PM by Federico -
Added lines 83-84:
  • IOREF. This pin on the Arduino 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 for working with the 5V or 3.3V.
November 23, 2012, at 04:54 PM by Roberto Guido -
Changed lines 148-150 from:

The maximum length and width of the Uno 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.

to:
October 22, 2012, at 07:48 PM by Scott Fitzgerald - fixed reference to the external clock
Changed lines 29-30 from:

The Arduino Uno is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, 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.

to:

The Arduino Uno is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator, 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.

June 01, 2012, at 03:29 PM by Federico -
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April 16, 2012, at 07:36 PM by Scott Fitzgerald -
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  • 5V. The regulated power supply used to power the microcontroller and other components on the board. This can come either from VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.
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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.
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The maximum length and width of the Uno 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.

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The maximum length and width of the Uno 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.

February 20, 2012, at 10:39 AM by David Cuartielles -
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EAGLE files: arduino-uno-Rev3-reference-design.zip (NOTE: works with Eagle 6.0 and newer)

December 09, 2011, at 04:13 PM by Federico -
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December 07, 2011, at 03:40 PM by Federico -
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December 07, 2011, at 03:28 PM by Federico -
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December 07, 2011, at 03:19 PM by Federico -
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November 08, 2011, at 07:56 PM by Federico -
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November 07, 2011, at 03:50 PM by Federico -
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The ATmega16U2 (or 8U2 in the rev1 and rev2 boards) firmware source code is available . The ATmega8U2 is loaded with a DFU bootloader, which can be activated by:

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The ATmega16U2 (or 8U2 in the rev1 and rev2 boards) firmware source code is available . The ATmega16U2/8U2 is loaded with a DFU bootloader, which can be activated by:

November 03, 2011, at 04:27 PM by Federico -
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The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the Atmega8U2 programmed as a USB-to-serial converter. Revision 2 of the Uno board has a resistor pulling the 8U2 HWB line to ground, making it easier to put into DFU mode. Revision 3 of the board has the following new features:

  • 1.0 pinout (SDA and SCL near to the AREF pin) and two other new pins near the RESET pin, the IOREF that allow the shields to adapt to the voltage provided from the board. In future, shields will be compatible both with the board with use the AVR, which operate with 5V and with the Arduino Due that operate with 3.3V.
to:

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.
Revision 2 of the Uno board has a resistor pulling the 8U2 HWB line to ground, making it easier to put into DFU mode.
Revision 3 of the board has the following new features:

  • 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 both with the board that use the AVR, which operate with 5V and with the Arduino Due that operate with 3.3V. The second one is a not connected pin, that is reserved for future purposes.
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  • TWI: A4 (SDA) and A5 (SCL). Support TWI communication using the Wire library.
to:
  • TWI: A4 or SDA pin and A5 or SCL pin. Support TWI communication using the Wire library.
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The Arduino Uno has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega8U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The '8U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, 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-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

to:

The Arduino Uno has a number of facilities for communicating with a computer, another Arduino, 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 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-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

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The ATmega8U2 firmware source code is available . The ATmega8U2 is loaded with a DFU bootloader, which can be activated by connecting the solder jumper on the back of the board (near the map of Italy) and then resetting the 8U2. 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.

to:

The ATmega16U2 (or 8U2 in the rev1 and rev2 boards) firmware source code is available . The ATmega8U2 is loaded with a DFU bootloader, which can be activated by:

  • On Rev1 boards: connecting the solder jumper on the back of the board (near the map of Italy) and then resetting the 8U2.
  • 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.

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.

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Rather than requiring a physical press of the reset button before an upload, the Arduino Uno 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 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 uses this capability to allow you to upload code by simply pressing the upload button in the Arduino environment. 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.

to:

Rather than requiring a physical press of the reset button before an upload, the Arduino Uno 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 uses this capability to allow you to upload code by simply pressing the upload button in the Arduino environment. 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.

November 03, 2011, at 11:56 AM by Federico -
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The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the Atmega8U2 programmed as a USB-to-serial converter. Revision 2 of the Uno board has a resistor pulling the 8U2 HWB line to ground, making it easier to put into DFU mode.

to:

The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the Atmega8U2 programmed as a USB-to-serial converter. Revision 2 of the Uno board has a resistor pulling the 8U2 HWB line to ground, making it easier to put into DFU mode. Revision 3 of the board has the following new features:

  • 1.0 pinout (SDA and SCL near to the AREF pin) and two other new pins near the RESET pin, the IOREF that allow the shields to adapt to the voltage provided from the board. In future, shields will be compatible both with the board with use the AVR, which operate with 5V and with the Arduino Due that operate with 3.3V.
  • Stronger RESET circuit.
  • Atmega 16U2 replace the 8U2.
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November 03, 2011, at 11:28 AM by Federico -
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October 26, 2011, at 02:24 PM by Tom Igoe -
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See also the mapping between Arduino pins and ATmega328 ports. The mapping for the Atmega8, 168, and 328 is identical.

October 26, 2011, at 02:23 PM by Tom Igoe -
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Note: The Arduino reference design can use an Atmega8, 168, or 328, Current models use an ATmega328, but an Atmega8 is shown in the schematic for reference. The pin configuration is identical on all three processors.

October 03, 2011, at 02:48 PM by Federico -
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September 17, 2011, at 01:46 PM by Scott Fitzgerald - mirror dev
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Input Voltage (recommended)9V
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Input Voltage (recommended)7-12V
September 12, 2011, at 03:35 AM by Scott Fitzgerald -
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Input Voltage (recommended)7-12V
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Input Voltage (recommended)9V
July 11, 2011, at 02:35 PM by Scott Fitzgerald - changed I2C to TWI
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  • I2C: A4 (SDA) and A5 (SCL). Support I2C (TWI) communication using the Wire library.
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  • TWI: A4 (SDA) and A5 (SCL). Support TWI communication using the Wire library.
June 10, 2011, at 06:39 PM by Scott Fitzgerald - Added information about 8u2 resistor for ease of programming
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The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the Atmega8U2 programmed as a USB-to-serial converter.

to:

The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the Atmega8U2 programmed as a USB-to-serial converter. Revision 2 of the Uno board has a resistor pulling the 8U2 HWB line to ground, making it easier to put into DFU mode.

January 04, 2011, at 05:00 AM by David A. Mellis -
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  • I2C: 4 (SDA) and 5 (SCL). Support I2C (TWI) communication using the Wire library.
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  • I2C: A4 (SDA) and A5 (SCL). Support I2C (TWI) communication using the Wire library.
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The Arduino UNo has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega8U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The '8U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, 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-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

to:

The Arduino Uno has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega8U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The '8U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, 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-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

October 29, 2010, at 10:11 PM by Tom Igoe -
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"Uno" means one in Italian and is named to mark the upcoming release of Arduino 1.0. The Uno and version 1.0 will be the reference versions of Arduno, moving forward. The Uno is the latest in a series of USB Arduino boards, and the reference model for the Arduino platform; for a comparison with previous versions, see the index of Arduino boards.

to:

"Uno" means one in Italian and is named to mark the upcoming release of Arduino 1.0. The Uno and version 1.0 will be the reference versions of Arduino, moving forward. The Uno is the latest in a series of USB Arduino boards, and the reference model for the Arduino platform; for a comparison with previous versions, see the index of Arduino boards.

October 09, 2010, at 04:01 PM by David A. Mellis -
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The ATmega8U2 firmware source code is available . The ATmega8U2 is loaded with a DFU bootloader, which can be activated by connecting the solder jumper on the back of the board (near the map of Italy) and then resetting the 8U2. 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).

to:

The ATmega8U2 firmware source code is available . The ATmega8U2 is loaded with a DFU bootloader, which can be activated by connecting the solder jumper on the back of the board (near the map of Italy) and then resetting the 8U2. 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.

September 27, 2010, at 03:15 PM by Tom Igoe -
Changed lines 88-89 from:

The Arduino UNo has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega8U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The '8U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, on Windows, a .inf file is required. INSERT LINK TO INSTRUCTIONS HERE 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-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

to:

The Arduino UNo has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega8U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The '8U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, 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-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

September 26, 2010, at 06:08 PM by 78.65.214.64 -
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September 20, 2010, at 05:15 PM by David A. Mellis -
Changed lines 102-103 from:

The ATmega8U2 firmware source code is available . The ATmega8U2 is loaded with a DFU bootloader, which can be activated by connecting the solder jumper on the back of the board and then resetting the 8U2. 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).

to:

The ATmega8U2 firmware source code is available . The ATmega8U2 is loaded with a DFU bootloader, which can be activated by connecting the solder jumper on the back of the board (near the map of Italy) and then resetting the 8U2. 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).

September 20, 2010, at 05:14 PM by David A. Mellis - SPI library.
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  • SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication, which, although provided by the underlying hardware, is not currently included in the Arduino language.
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  • SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication using the SPI library.
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The ATmega328 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. To use the SPI communication, please see the ATmega328 datasheet.

to:

The ATmega328 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. For SPI communication, use the SPI library.

September 20, 2010, at 05:11 PM by David A. Mellis - Bootloader: 2 KB -> 0.5 KB
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Flash Memory32 KB (ATmega328) of which 2 KB used by bootloader
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Flash Memory32 KB (ATmega328) of which 0.5 KB used by bootloader
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The ATmega328 has 32 KB, (also with 2 KB used for the bootloader). It also has 2 KB of SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library).

to:

The ATmega328 has 32 KB (with 0.5 KB used for the bootloader). It also has 2 KB of SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library).

September 20, 2010, at 04:19 PM by Tom Igoe -
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  • 3V3. A 3.3 volt supply generated by the on-board FTDI chip. Maximum current draw is 50 mA.
to:
  • 3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.
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  • 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 FTDI USB-to-TTL Serial chip.
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  • 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.
Changed lines 88-89 from:

The Arduino UNo has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega8U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The '8U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, on Windows, a .inf file is required. INSERT LINK TO INSTRUCTIONS HERE 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 FTDI chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

to:

The Arduino UNo has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega8U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The '8U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, on Windows, a .inf file is required. INSERT LINK TO INSTRUCTIONS HERE 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-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

September 20, 2010, at 04:05 PM by Tom Igoe -
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Changed lines 13-14 from:

"Uno" means one in Italian and is named to signify WHAT? It doesn't correspond to 1.0 The UNo is the latest in a series of USB Arduino boards, and the reference model for the Arduino platform; for a comparison with previous versions, see the index of Arduino boards.

to:

"Uno" means one in Italian and is named to mark the upcoming release of Arduino 1.0. The Uno and version 1.0 will be the reference versions of Arduno, moving forward. The Uno is the latest in a series of USB Arduino boards, and the reference model for the Arduino platform; for a comparison with previous versions, see the index of Arduino boards.

September 19, 2010, at 11:22 PM by Tom Igoe -
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Rather then requiring a physical press of the reset button before an upload, the Arduino Uno 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 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 uses this capability to allow you to upload code by simply pressing the upload button in the Arduino environment. 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.

to:

Rather than requiring a physical press of the reset button before an upload, the Arduino Uno 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 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 uses this capability to allow you to upload code by simply pressing the upload button in the Arduino environment. 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.

September 19, 2010, at 11:10 PM by David A. Mellis -
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INSERT INSTRUCTIONS FOR REPROGRAMMING THE 8U2 HERE

to:

The ATmega8U2 firmware source code is available . The ATmega8U2 is loaded with a DFU bootloader, which can be activated by connecting the solder jumper on the back of the board and then resetting the 8U2. 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).

September 19, 2010, at 01:49 AM by Tom Igoe -
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Arduino Uno

Attach:ArduinoUno.jpg Δ

Overview

The Arduino Uno is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, 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.

The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the Atmega8U2 programmed as a USB-to-serial converter.

"Uno" means one in Italian and is named to signify WHAT? It doesn't correspond to 1.0 The UNo is the latest in a series of USB Arduino boards, and the reference model for the Arduino platform; for a comparison with previous versions, see the index of Arduino boards.

Summary

MicrocontrollerATmega328
Operating Voltage5V
Input Voltage (recommended)7-12V
Input Voltage (limits)6-20V
Digital I/O Pins14 (of which 6 provide PWM output)
Analog Input Pins6
DC Current per I/O Pin40 mA
DC Current for 3.3V Pin50 mA
Flash Memory32 KB (ATmega328) of which 2 KB used by bootloader
SRAM2 KB (ATmega328)
EEPROM1 KB (ATmega328)
Clock Speed16 MHz

Schematic & Reference Design

EAGLE files: arduino-duemilanove-uno-design.zip

Schematic: arduino-uno-schematic.pdf

Power

The Arduino Uno 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 of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be 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. The input voltage to the Arduino 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.

  • 5V. The regulated power supply used to power the microcontroller and other components on the board. This can come either from VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.

  • 3V3. A 3.3 volt supply generated by the on-board FTDI chip. Maximum current draw is 50 mA.

  • GND. Ground pins.

Memory

The ATmega328 has 32 KB, (also with 2 KB used for the bootloader). It also has 2 KB of SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library).

Input and Output

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 a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. 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 FTDI 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, which, although provided by the underlying hardware, is not currently included in the Arduino language.

  • 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.

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. Additionally, some pins have specialized functionality:

  • I2C: 4 (SDA) and 5 (SCL). Support I2C (TWI) communication using the Wire library.

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.

See also the mapping between Arduino pins and ATmega328 ports?.

Communication

The Arduino UNo has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega8U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The '8U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, on Windows, a .inf file is required. INSERT LINK TO INSTRUCTIONS HERE 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 FTDI chip and 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 Uno's digital pins.

The ATmega328 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. To use the SPI communication, please see the ATmega328 datasheet.

Programming

The Arduino Uno can be programmed with the Arduino software (download). Select "Arduino 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 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 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; see these instructions for details.

INSERT INSTRUCTIONS FOR REPROGRAMMING THE 8U2 HERE

Automatic (Software) Reset

Rather then requiring a physical press of the reset button before an upload, the Arduino Uno 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 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 uses this capability to allow you to upload code by simply pressing the upload button in the Arduino environment. 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.

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 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.

USB Overcurrent Protection

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.

Physical Characteristics

The maximum length and width of the Uno 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.

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