The Doodlebug does nothing on it's own, that is, it is not recognized as
a device by the computer. It is locked at USB full speed and will not
work with devices at USB low speed or USB high speed.
If you have a mouse that runs at USB full speed, it should work, but
I think most mice are USB low speed devices.
The 5.25 volts shows the power supply is working properly.
New devices (ones that have not been connected to your computer
before), may need to be plugged in...