Can an Android NFC phone act as an NFC tag?

Question

From what I have understood so far, an NFC phone will act as an NFC reader which will read data from an NFC tag. Now my question is, can we switch this around? Can we make a

Answer 1

At this time, I would answer "no" or "with difficulty", but that could change over time as the android NFC API evolves.

There are three modes of NFC interaction:

1. Reader-Writer: The phone reads tags and writes to them. It's not emulating a card instead an NFC reader/writer device. Hence, you can't emulate a tag in this mode.

2. Peer-to-peer: the phone can read and pass back ndef messages. If the tag reader supports peer-to-peer mode, then the phone could possibly act as a tag. However, I'm not sure if android uses its own protocol on top of the LLCP protocol (NFC logical link protocol), which would then prevent most readers from treating the phone as an nfc tag.

3. Card-emulation mode: the phone uses a secure element to emulate a smart card or other contactless device. I am not sure if this is launched yet, but could provide promising. However, using the secure element might require the hardware vendor or some other person to verify your app / give it permissions to access the secure element. It's not as simple as creating a regular NFC android app.

More details here: http://www.mail-archive.com/android-developers@googlegroups.com/msg152222.html

A real question would be: why are you trying to emulate a simple old nfc tag? Is there some application I'm not thinking of? Usually, you'd want to emulate something like a transit card, access key, or credit card which would require a secure element (I think, but not sure).

Answer 2

Can we make an Android NFC as the tag which an NFC reader will get data from?

The Nexus S supports peer-to-peer mode, which as its name implies, causes one phone to act as a tag which another phone can read. There was a really good Google I/O session on NFC this year. I would recommended watching it if you're at all interested in NFC.