Free IMU another component for inertial measurement

Technology
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I was told about a new Attitude and Heading Reference System (AHRS) named freeIMU. See the link below :

http://www.varesano.net/projects/hardware/FreeIMU

To compare with Razor, the main differences are :

  • freeIMU adds an high resolution altimeter (I don’t think it is very useful for Poppy except flying Poppy :wink: )
  • The communication bus is I²C for freeIMU whereas it is UART for the Razor (for Poppy, it can be useful to have all sensors centralized on one Arduino to avoid the multiplicity of COM ports)
  • Razor and freeIMU have the same compass component (this is the only common component)
  • freeIMU uses the integrated MPU-6050 gyro+accelerometer device which does all the integration of compass and altimeter (it is adapted to drones) whereas Razor has an Arduino onboard which integrates all the sensors to export it on UART.
  • freeIMU uses a mysterious “Motion Processor” of MPU-6050 to integrate the sensors to have all attitude angles whereas Razor uses “Direction Cosine Matrix”
  • The measurement ranges seem to be configurable on freeIMU. On Razor, it is not configurable if you do not program the Arduino, but by default, it is very large (2000deg/s for the gyrometer). (it is important because for drone control, the range is narrow, as for Naveol unit)
  • freeIMU costs 45€ whereas 81€ for Razor

To sum up, here we have 4 AHRS units we can use for Poppy:

  • Razor : open source but 81€

  • FreeIMU : open hardware, 45€ but needs an Arduino to get I²C (with the foot contact sensors ?)

  • Naveol : measurement range too limited (300deg/s), not open source and 149€

  • MM7150 (Microchip) : not yet available, I²C interface and 20€

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