Multiwii is a quadrotor autopilot system (FC firmware) developed by many RC hobbyists around the world. This project uses an Arduino board as a the processor, however it’s been seen to run on other platforms. This project aims to make the fabrication of electronics easy.
Originally, it started with gyroscopes and accelerometers of the commercial off-the-shelf Wii motion controller from Nintendo, which needs less soldering (that’s why it’s called multi-wii). Multiwii laster on began to support many different brands and models of Gyro and Acc sensors, the list can be found in the config.h file in the multiwii source code. There is a GUI-based interface software provided (shown on the very top of this post). You can use it to adjust your PID setting values, and many other features.
At first it was a very basic flight controller system and it only supports simple flight control. Now it has been developed so much it even supports GPS modules, so you can have postition hold and return to home functions. The good thing about this is it’s totally opensource, all the development is carried out by the users and it’s amazing to see how it’s evolving over time too. Because of that, it’s a very flexible system, and you are open to much hardware, software, functions possibility. For example, someone has make it possible to integrate Bluetooth module into the code, so they can control their quadcopter from their mobile phone, and tune their PID values from the phone while flying.
Despite of all the flexibility of Multiwii, the performance of Multiwii is still not consistent, espeically with more advanced functions like altitude hold. Multiwii takes effort to setup, and to get it working you will have to work much harder than using other more expensive controller board, especially if you are planning only use a Arduino board and not a manufactured multiwii Flight controller.
If you are tight in budget, and don’t mind challenges on the way, you can have a go with Multiwii.
Apart from making your own multiwii flight controller using gyro, acc sensors and arduino board like I did, you can also buy the commercially available board. The most popular Multiwii flight controller out seems to be this one.