Fail to get logs if we restart the script

[AlexisTM]

Bug explanation:

The logging system seems unreliable when trying to reconnect to the Crazyflie (Roadrunner) after it was soft disconnected.

Expected behaviour:

• Run basiclog.py
• Have data printed
• basiclog.py stops after 5 seconds
• Run basiclog.py directly after
• Have data printed
• basiclog.py stops after 5 seconds

Experienced behaviour:

• Run basiclog.py
• Have data printed
• basiclog.py stops after 5 seconds
• Run basiclog.py directly after
• *Nothing is printed and *
• basiclog.py stops after 5 seconds
• OR
• basiclog.py hangs on 'Connecting to usb://0'

[AlexisTM]

Second run of basiclog.py with 3 variables

Scanning interfaces for Crazyflies...
Crazyflies found:
usb://0
Connecting to usb://0
Connected to usb://0
Disconnected from usb://0

Second run of basiclog.py with 6 variables, it freezes.

Scanning interfaces for Crazyflies...
Crazyflies found:
usb://0
Connecting to usb://0

The 6 Variables:

        self._lg_stab.add_variable('kalman.stateX', 'float')
        self._lg_stab.add_variable('kalman.stateY', 'float')
        self._lg_stab.add_variable('kalman.stateZ', 'float')
        self._lg_stab.add_variable('kalman.varPX', 'float')
        self._lg_stab.add_variable('kalman.varPY', 'float')
        self._lg_stab.add_variable('kalman.varPZ', 'float')

[krichardsson]

I can reproduce this using USB. Seems to work with a radio.
This is most likely a firmware problem, I created an issue for it bitcraze/crazyflie-firmware#394

[AlexisTM]

Very likely to be due to the STM USB library: bitcraze/crazyflie-firmware#393