* https://www.digikey.de/de/datasheets/honeywellmicroelectronicsprecisionsensors/honeywell-microelectronics-precision-sensors-hmc5883l
  * https://github.com/adafruit/Adafruit_HMC5883_Unified/blob/master/examples/magsensor/magsensor.ino
  * http://www.holybro.com/product/m8n-gps/
  * https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_Compass
  * https://wiki.seeedstudio.com/Arduino_Software_I2C_user_guide/