The corresponding get functions return the internal data value.

When starting, changed the mode before starting the thread.

Solved a bug: the finish thread signal was not reset after stopping the thread, and it made the thread finish immediatelly after the first time.

Solved a bug in the load_calibration function: the mutex was unlocked without a previous lock if the file didn't exist.

Changed the communications timeout to 500 ms.
the set_operation_mode() function only does it function if the new mode is different from the current one.

  - all power modes
  - all operation modes
  - individual sensor calibration
  - get fusion and non-fusion data
  - calibration save to and load from file.