The Boarduino is an Arduino clone: when programmed with the Arduino bootloader, it can talk to the Arduino software and run sketches just like the original.

There are noticable differences between the Boarduino and the Arduino.

• Shields cannot be used as the form factor is so different
• There are two versions, a DC version and a USB version
• For the DC version there isn't an on-board USB chip. This means you need to use a USB-TTL cable or a MiniUSB (or any other FTDI breakout board) which is not included. There are also no rx/tx LEDs and no rx/tx 1K series resistors.
• For the USB version, there is an on-board USB chip but there isn't a DC jack or 5V regulator, you can power it through the USB jack.
• There is a rx 1K resistor so you can use this to talk to serial accessories.
• 16.00 MHz ceramic resonator is used instead of crystal, so cycle speed may be off by +- 0.3nS (0.5%). This isn't relevant for UART timing, servo drivers, PWM, etc. but could be an issue if you need nanosecond-precision timing. Note that the Arduino software only provides millisecond-precision timing for general sketches (1 second = 1000ms. 1ms = 1,000,000 ns)

The specifications for the DC boarduino include:

• Designed to plug into a breadboard for easy prototyping
• Petite size, only 3“ x 0.8” (75mm x 20mm)
• All 'standard' pins are brought out - Digital 0 thru 13, Analog 0 thru 5, ARef, 5V, Ground, Vin and Reset
• 2 LEDs, green power and red “pin 13” LED just like the Arduino Diecimila
• Standard Reset button
• ATmega328P, running at 16.00 MHz, just like the latest Arduino, the Duemilanove (note that the product photo above hasn't been updated)
• 6-pin standard ICSP header
• Standard 2.1mm DC jack (just like the original Arduino) with 5V regulator to run on 7V-17V power (DC)
• USB or External power, selectable with a jumper (just like original Arduino)
• 1N4001 diode protects against using incorrect wall adapter
• 6-pin header at the end for a USB-TTL cable
• Auto-reset capability when used with a USB-TTL cable
• Available as a low cost kit with standard parts, so its never out of stock
• All through-hole parts are easy to solder