If you’re involved in a DIY electronics project and need to combine multitasking application with real-time and analog features, RasPiO Duino is a simple add-on board that makes easy to add the power of Raspberry Pi and the Arduino’s abilities to communicate with hardware components to your projects.
People use Arduino and Raspberry Pi together because the Raspberry Pi can run an operating system, offer a wide range of connectivity options (HDMI, USB, Ethernet, Audio), large storage options, Internet connectivity, and it works generally better with software projects. Even if the Pi provides also analog GPIO pins, the Arduino microcontroller is preferred for precise real-time applications, analog inputs/outputs, instant boot, and in general the platform is better at talking to machine parts such as motors, sensors, etc.
The RasPiO Duino board is designed by Alex Eames to make the collaboration between Raspberry Pi and Arduino easier for regular users. The device is engineered as an add-on board for the Raspberry Pi and includes an ATmega328 chip with similar specifications to the Arduino board.
What is good for a developer that uses the Arduino and Raspberry Pi together, is that the board can run programs that use the both devices at once. The board is programmed via the SPI pins on the Pi and run a custom version of Arduino IDE called Gertboard.
The board runs on 3V3 and offers a compact prototyping area for small projects.