Different types and Different works of Arduino

Arduino Uno

Most popular Arduino is Arduino uno R3. 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. 
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.

Arduino Uno R3

Summary

Microcontroller                       ATmega328Operating
Voltage                                 5VInput
Voltage (recommended)      7-12VInput
Voltage (limits)                     6-20V
Digital I/O Pins                     14 (of which 6 provide PWM output)
Analog Input Pins                 6
DC Current per I/O Pin         40 mA
DC Current for 3.3V Pin       50 mA
Flash Memory                      32 KB (ATmega328) of which 0.5 KB used by bootloader
SRAM                                   2 KB (ATmega328)
EEPROM                              1 KB (ATmega328)
Clock Speed                         16 MHz
Length                                  68.6 mm
Width                                    53.4 mm
Weight                                  25 g

Arduino Mega 2560

Overview

The Arduino Mega 2560 is a microcontroller board based on the ATmega2560 (datasheet). It has 54 digital input/output pins (of which 15 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), 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 Mega is compatible with most shields designed for the Arduino Duemilanove or Diecimila.The Mega 2560 is an update to the Arduino Mega, which it replaces.The Mega2560 differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the ATmega16U2 (ATmega8U2 in the revision 1 and revision 2 boards) programmed as a USB-to-serial converter.
Revision 2 of the Mega2560 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.
• Stronger RESET circuit.
• Atmega 16U2 replace the 8U2.

Summary

Microcontroller                            ATmega2560
Operating Voltage                       5V
Input Voltage (recommended)     7-12
VInput Voltage (limits)                  6-20V
Digital I/O Pins                             54 (of which 15 provide PWM output)
Analog Input Pins                        16
DC Current per I/O Pin                40 mA
DC Current for 3.3V Pin               50 mA
Flash Memory                             256 KB of which 8 KB used by bootloader
SRAM                                          8 KB
EEPROM                                    4 KB
Clock Speed                               16 MHz

Arduino Due

Overview

The Arduino Due is a microcontroller board based on the Atmel SAM3X8E ARM Cortex-M3 CPU (datasheet). It is the first Arduino board based on a 32-bit ARM core microcontroller. It has 54 digital input/output pins (of which 12 can be used as PWM outputs), 12 analog inputs, 4 UARTs (hardware serial ports), a 84 MHz clock, an USB OTG capable connection, 2 DAC (digital to analog), 2 TWI, a power jack, an SPI header, a JTAG header, a reset button and an erase button.Warning: Unlike other Arduino boards, the Arduino Due board runs at 3.3V. The maximum voltage that the I/O pins can tolerate is 3.3V. Providing higher voltages, like 5V to an I/O pin could damage the board.The board contains everything needed to support the microcontroller; simply connect it to a computer with a micro-USB cable or power it with a AC-to-DC adapter or battery to get started. The Due is compatible with all Arduino shields that work at 3.3V and are compliant with the 1.0 Arduino pinout.The Due follows the 1.0 pinout:

• TWI: SDA and SCL pins that are near to the AREF pin.
• The IOREF pin which allows an attached shield with the proper configuration to adapt to the voltage provided by the board. This enables shield compatibility with a 3.3V board like the Due and AVR-based boards which operate at 5V.
• An unconnected pin, reserved for future use.

The Due has a dedicated forum for discussing the board.

ARM Core benefits

The Due has a 32-bit ARM core that can outperform typical 8-bit microcontroller boards. The most significant differences are:

• A 32-bit core, that allows operations on 4 bytes wide data within a single CPU clock. (for more information look int type page).
• CPU Clock at 84Mhz.
• 96 KBytes of SRAM.
• 512 KBytes of Flash memory for code.
• a DMA controller, that can relieve the CPU from doing memory intensive tasks.

Summary