I am new to the world of Arduinos but have a new project going with a MultiWii Flight controller. With the MultiWii comes a software for showing all data that is measured from the sensors (acceleration, velocity, roll, pitch, etc) which is nice but I would like to have/extract this data (call raw data or something) from all sensors (i.e. the data plotting everything, in numbers). Maybe it is the simplest thing to do, and I guess I have to set up some serial connection between the controller and tell it to send this data somehow but I do not know where to start so any guidance and help is appreciated.
Since you're new to Arduino, I'd suggest beginning with a basic interfacing arduino activity. Once you understand reading and writing digital and analog signals it's pretty much plain sailing from there. You may want to invest some time and a bit of cash in a beginners course on Udemy (try PEter Dalmaris' course https://www.udemy.com/arduino-sbs/) it's a good start. From there, talking to the MultiWii should be a piece of cake. Also, check out http://www.multiwii.com/connecting-elements