As main CPU we used a powerfull Cortex M3 ARM CPU, that has been clocked with 50MHz.


The IMU, or better to say the AHRS that has been used was a VN100 from the US company Vectornav. We decided to use this sensor, because it already does the sensor fusion and Kalman filtering. The sensor module includes:

  • Magnetometer (3 axis)
  • Accelerometer (3 axis)
  • Gyroscope (3 axis)
  • Kalmanfilter
  • Autotuning and callibration
  • Temperature calibration​


One of the trickiest and most time consuming parts of the entire project were the drivers for the 4 BLDC motors. BLDC motors need an extensive effort to work properly. The problem with this implementation of a brushless controller is the space limitied environment. The only space that was left, was underneath the motors (for the driving stage) and between the motors on the outer ring (for the control stage). The brushless controllers are based on a ATmega168 combined with a powerfull 2A driving stage.

The BL-CPUs communicate with the main CPU using the SPI bus. This is done at very fast speed to achive mimimim dead time when controlling the motors from them main CPU.

Some key facts:

  • 200Hz update rate
  • digital SPI interface
  • RPM monitoring
  • 2 Status LEDs

Brushless Motors

The brusless motors that have been used were the Hobbyking "AP03" motors in the 4000RPM/V edition. This motors provide with the used propellers a thrust of ~55g at a maximum current of 2A per motor. Everything a weight of 3.1g. 


To be able to communicate with the Joystick or even a smartphone a bluetooth 2.1 module has been implemented. This bluetooth module allowed us to do high bandwidth communication with the PC software and Matlab and also control only communication with Joystick. The range of bluetooth was enough for our application, as squadrone is designed for indoor flight only.


PCB Design

The PCB has been designed from ground up using the programm Cadsoft Eagle. It was assembled using reflow soldering combined with hand soldering.

PCB as main body

All parts of the helicopter are mounted on the PCB to achieve

Motors directly mounted to the PCB

No additonal mechanic required

Expansion board mount

Simply expandable