How NFC works ?
– Card emulation mode
In card emulation mode, the “NFC Device” behaves like a contactless smart card. It is functioning as a target in a passive mode (cf. definitions in §1.2.2).
While a contactless card is powered by the magnetic field generated by the interrogator, an “NFC Device” may require more energy to operate. Indeed, an NFC application on a mobile phone, a tablet or a consumer device may benefit from other features than just NFC (screen, applications, security, internal communications, etc.). Access to these features requires an internal power source, a battery or power supply.
– Reader mode
The “NFC Device” in reader mode behaves like a simple contactless card reader. It initiates communication by generating a magnetic field and then sending a command to the target. The target responds to the interrogator by retro-reflecting the incident wave as described in the definitions in §1.2.2).
The specificity of NFC operating modes is that the target can be not only a tag or a contactless card, but also an “NFC Device" that behaves like a contactless card (in card emulation mode).
Usages of reader mode are principally information reading, when “NFC Devices” is used to read data by waving it in front of electronic labels available on streets, bus stops, sightseeing monuments, ad banners, parcels, products or on business cards (vCard).
– Peer-to-Peer mode
This mode allows two “NFC Devices” with the same NFC performance to exchange the data with each other alternately. Each of these devices supports both interrogator and target communication modes, sending or receiving by turns the data.
Communication in peer-to-peer mode is slower than in conventional reader / card emulation mode, because of the management of a heavier protocol, which is necessary for the repartition of roles between the two “NFC Devices.”
As of use cases:
This mode can be used to initiate gateways (pairing) with other technologies for data transfer at higher than NFC (Bluetooth, Wi-Fi or Wi-Fi Direct) data rates.