I cannot install pip since the space on the device is very limited. I have no more than 8mb available and it seems not to be enough.

To check if you have pyusb 1.0, just run the python interpreter and try an

import usb.core

If it is not throwing an error, it should be the 1.0.

How did you succeed to install pip with such a limited space ? I am using Gl-Mifi. Any suggestions ?