Android NFC with USB-NFC-Reader

Question

I have an Android tablet with Android 4.2. This tablet does not have NFC hardware. However I have an external USB reader: ACR 1252U, that came with an Android library. This

Answer 1

Is it somehow possible, to use the built-in NFC-functions from Android with the external USB reader?

No, that's not possible. If your Android devices did not ship with NFC, there simply is no built-in NFC functionality (not even on the software side). The Android NFC API is essentially an empty stub implementation that does nothing on such a device.

Is there another library for this reader, that supports peer-to-peer communication with other NFC-devices?

The library from ACS does not prevent you from accessing the reader's peer-to-peer capabilities, so I don't see why you would want to use a different library. See section 5.9 of the API specification on how to use the reader's peer-to-peer capabilities.

I need to transfer files from my Android 4.2 tablet to other Android NFC devices

Based on that request I assume that you want to use something like Android Beam to establish some fast out-of-band channel over NFC and then transfer the (large?) files over that out-of-band channel (e.g. WiFi or Bluetooth).

In that case, you would need to re-implement the Android Beam stack (NFC peer-to-peer mode + LLCP + Simple NDEF Exchange Protocol + establishing out-of-band communication channel + transfering file over that channel)