Controller composed of 2 inputs 2 servo and 1 output:
  
                 -------
     INPUT 1 >---|PID 1|---|
                 -------   |
                           |-----> OUTPUT
                 -------   |
     INPUT 2 >---|PID 2|---|
                 -------
  
  Usage:
  - copy files of servo_commmon directory to STM32 discovery board.
  - copy 'servo2to1_core.py' file to STM32 discovery board.
  - copy 'servo2to1_INPUT_OUTPUT' file (with respect to INPUT and OUTPUT device) to STM32 discovery board.
  - update content of 'boot.py' file to 'servo2to1_INPUT_OUTPUT', e.g.:
  -> pyb.main('servo2to1_adc_vnh.py')