Electronic – Microcontroller acting as USB host for an audio device

There is nothing in the USB spec that forces a host to identify itself, and there is no standard way a device can request such information. Without a cooperating driver in the operating system, there is no way for a ordinary device to know details about the host, like what operating system it is running, what processor it is using, etc.

I have, however, noticed that different operating systems tend to have their own quirks about what they request in what order during enumeration. You might be able to do some testing and find a way to distinguish a few of the major operating systems. However, that would not be guaranteed, could easily change at minor revisions, and can certainly be deliberately spoofed.

If you want a device to know it is connected to a trusted host, you will have to previously load software on that host. The device could, for example, send out a randomly generated string of bits when asked the right way by your software on the host. The host must then respond with a reply that is hashed from the original bits in a particular way envolving a password. Only a host with the right algorithm and password could reply correctly.

Of course that is just simple scheme. It can get a lot more complicated depending on what level of attacker you want to protect youself from. For example, the simple scheme I described above would be no good against a man in the middle attack.

There are enough ways available to provide host mode with a microcontroller that trying to do it with something not intended for the role is "doing it the hard way".

Look for devices with USB OTG" = "On the Go" capability.
These can provide either host of slave capability as required.

If "... something like Atmel ATmega32U2 ... " includes an Atmel AT90USB64 , then yes.

ie using one of the available parts that DO have this capability is the "easy way" to go. There are enough ways available to provide host mode with a microcontroller that trying to do it with something not intended for the role is "doing it the hard way". Look for devices with USB OTG" = "On the Go" capability. These can provide either host of slave capability as required.

ICs with OTG capability of some sort

Cheapest in 1's in stock at Digikey:

AVR microcontroller with USB OTG capability $8.43/1 Digikey in stock.

PIC OTG & Host capable microcontroller $4.22/1 in stock Digikey

The PIC device is also the cheapest host / OTG microcontroller of any sort available in stock in 1's from Digikey.