NFC Shield is a Near Field Communication interface for Arduino build around the popular NXP PN532 integrated circuit. NFC is a short-distance radio technology that enables communication between devices that are held close together. NFC traces its roots in RFID technology and is an open platform technology standardized in ECMA-340 and ISO/IEC 18092.

NFC is widely used like RFID to recognize cards/tags (NXP Mifare Cards / Tags). NFC can be used as an alternative to travel card using the read/write memory provided by cards/tags. Few mobile phones comes with NFC inbuilt - they are used as readers of cards, tags, smart posters with a Web URL(like a Mobile QR-Code reader). This technology is also being applied for smart cashless purchases.

Like many other standards, NFC technology is regulated by Near Field Communication Forum which standardizes NFC communication -- how they devices pair, share data and allow a secure transaction to happen.NFC Forum develops and certifies devices compliant with NFC standards.

NFC operates on unlicensed ISM(Industry Scientific Medical) band of 13.56 MHz Frequency. NFC communication range is up to 10 cm. But, this is limited by the antenna and power radiation design. Most devices work within a range of 10mm. NFC Shield antenna is designed to work within a range of 1cm. NFC Shield provides all necessary circuitry for PN532 like 27.12Mhz crystal, power supply.It also beaks-out the I/O pins of PN532 for easy access.

The communication between Arduino and NFC Shield is via SPI.