Wow. Florian did his own motor controllers, RC (via Xbee) and everything else. From Hackaday:
We think [FlorianH] did a bang-up job of prototyping his Minima Quadcopter on the cheap. The total bill comes in right around $200 and we’re very happy with the quality of parts as well as the results.
Here you can see the top of the double-sided board which he etched to host all of the components. At each corner there is a power MOSFET which drives the brushless motor. At first glance we thought that the Xbee module was acting as the radio control and processer as well. But on the underside you’ll find an ATmega32 which is responsible for reading the Gyroscope sensor and Accelerometer, processing these signals and driving each MOSFET via PWM lines to provide stability.
You can see some flight tests after the break. [FlorianH] mentions that there is some oscillation in the feedback loop when both the gyro and accelerometer are used. But cut the accelerometer out of the equation and the platform is rock-solid.
This build uses carbon tubes to mount the motors, which we think will be a little more robust than the all-PCB designs are.