Multirotors and Atmega

It came as a surprise to me that atmel processors are used in rc multicopters. There are purpose built boards for this kind of a hobby. There are mainly 3 different trees evolved in this scene

1st ardupilot (APM) a mega2560 based board, basically a arduino mega with barometric, acceleration and gyro sensors built in, as of 2.7 version boards lacking a magnetometer which is put in a GPS add on. Its regarded as a goto board for GPS functionality. It has a separate windows GUI mission planner. Board has special connectors builtin for connecting gps , power sensors speed sensors and almost everything else you can imagine to add to your flying apparatus. Its very easy to upgrade just go online in GUI and press a button. Downside is that its relatively expensive, bulky and fine tuning is a bit cumbersome. As of now it has evolved from 8bit Atmega controllers to 32bit St chipset, board is codenamed PixHawk or PIX for short.

2nd Multiwii. Basically its like a proprietary mega or 328 board. Everything applies except updating from mission planner. But for the price its a lot better. Coming from an arduino background you should go this route. You don't need to buy a multiwii board. A regular arduino will do. Go to eBay and acquire some sensors, Velcro tape or a glue gun and you're set. Code is open and developed on a daily basis. Also its much easier to add your own code to it. Code is all commented and easy to understand and modify.

3rd are proprietary 3rd party flight controllers for example-32bit CC3d, KK board series (latest 2,1), built-in types, where the board is a part of the frame. They arent that common but they have quite a following most of the time, for example there are some enthusiast who will bash whatever choice of FC(flightcontroller) you have as long as it isn't a KK board.

All of the ESC(Electronic speed controller)-s that i have come across have been controlled by Atmega8 series processors. They are used to make DC voltage into AC that controls the brushless motors on the multirotor. Atmega is used for getting the information from the FC and after that to control the RPM of the motor that it's connected to. All of the main calculations as to hoq fast every motor has to is done by the FC. ESC is just a dumb device that gets a signal and makes the propellers go zoom.

Today I disected a Ublox 6M Gps receiver, and it too had an Atmega chip as a supplementary communications platform.