The Arduino Uno R3 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 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 recommended range of voltage is 7 volts to 12 volts, maximum of 2A.
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).
Input and Output :
Each of the 14 digital pins on the Uno can be used as an input or output, using commands. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA current and has an internal pull-up resistor (disconnected by default) of 20 kOhms to 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 ATmega8U2 USB-to-TTL Serial chip.
External Interrupts: 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value.
PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output with the commands.
SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication using the SPI library.
LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it’s off.
The Arduino Uno R3 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:
TWI: A4 or SDA pin and A5 or SCL pin. Support 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.
The Arduino Uno R3 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). 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 Uno R3 can be program with the Arduino software (download). Select “Arduino Uno from the Tools > Board menu (according to the micro-controller on your board). The ATmega328 on the Arduino Uno R3 comes pre burn 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). It can also be bypassed the bootloader and program the microcontroller through the ICSP (In-Circuit Serial Programming) header.
Automatic (Software) Reset :
Rather than requiring a physical press of the reset button before an upload, the Arduino Uno is design in a way that allows it to be reset by software running on a connect computer. One of the hardware flow control lines (DTR) of theATmega8U2/16U2 is connected to the reset line of the ATmega328 via a 100 nano-farad capacitor. When this line is assert (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 boot-loader can have a shorter timeout, as the lowering of DTR can be well-coordinate with the start of the upload. The Arduino Uno R3 contains a trace that can be cut to disable the auto-reset. The pads on either side of the trace can be soldere together to re-enable it. It’s label “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 apply to the USB port, the fuse will automatically break the connection until the short or overload is remove.
- Digital I/O Pins: 14 (of which 6 provide PWM output)
- Analog Input Pins: 6
- Flash Memory: 32 KB (ATmega328) of which 0.5 KB used by bootloader
- Micro-controller: ATmega328
- Operating Voltage: 5V
- Input Voltage (recommended): 7 V DC – 12 V DC
- DC Current per I/O Pin: 40 mA
- DC Current for 3.3V Pin: 50 mA
- SRAM: 2 KB
- EEPROM: 1 KB
- Clock Speed: 16 MHz
- DIY project prototyping
- Developing varied varieties of projects that require a code based control
- Automation System development
- Learning AVR programming
- Entry level circuit designing
- 1 X Arduino Uno R3
- 1 X USB Cable