Q:

USB Drive detection circuit

I am building a simple portable speaker using a DFPlayer Mini, but I think that's not entirely relevant to my question.
I am looking for a way to detect when an USB Drive is plugged in, so the player can start reading data from it. I haven't found anything on this issue on the internet, so what i came up with is this circuit:

I expect the USB to drain enough current to switch on the transistor, so the HIGH IF USB CONNECTED line is driven high. I'm not sure whether the resistor values are appropriate, but I didn't want to waste too much current.
In my mind, this should work, as the USB should be able to work up to as low as 3.3 V. 
It just came to my mind that I don't actually need the voltage regulator, but where do I connect the 4.3 V on the Arduino board? To 5V or 3V3?
If you see any other flaws with my design, please let me know.

A:

The Arduino library for DFPlayer includes a status for CardInserted and CardRemoved.
I assume they simply poll the USB key for presence.
Just read the code in the link above or at Github

