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NFC
What is RFID?
RFID (Radio Frequency Identification) is a generic term for contactless technology, usually used for application related to tagging of goods and items. It ranges from few cm to several m, is based on various technologies: LF (120 to 150 KHz), HF (13.56 MHz), UHF (433 to 900 MHz), and standardized in ISO 18000.
What is Contactless Proximity technology?
It is a subset of RFID, limited to a frequency range: 13.56 MHz. It is associated to people where an active action is required (e.g. put a card in front of a reader). Traditional applications are Access Control, eGovernment (Passport), Payment, and Transport. It is short range (up to 10 cm) and standardized in ISO/IEC 14443.
What is NFC?
· “Near Field Communication”: short-range (up to 10 cm) communication, based on the 13.56 MHz contactless proximity technology.
· 13.56 MHz technology is already present in our everyday life in various applications, like Physical Access Control, Transportation, and Payment.
· Objective of NFC: extend the use of this 13.56 MHz technology to new Consumer and Industrial applications by integrating this technology.
· It is standardized in the NFC Forum:http://nfc-forum.org/http://nfc-forum.org/
· NFC enabled mobile phones can be used in traditional smart card applications. NFC enabled devices can interact with each other (e.g. Pairing, Control) by a simple touch.
Which modes are available with NFC?
· Reader Mode - Read data from smart card or smart objects
One example of the reader mode is implemented in the Polling Project, see Quick Startup Guide, chapter 6. 'How does the Polling software work'.
· Peer-to-Peer - Exchange data between NFC devices One example of the P2P mode is implemented in the exchange of a picture to a mobile phone, see Quick Startup Guide, chapter 8. 'P2P SNEP client project'
· Card Emulation Mode - Use your device as a Card
One example of the card emulation mode is implemented in the Paperchase example, see Quick Startup Guide, chapter 7. 'Card Emulation project'
EXPLORE-NFC
Does the EXPLORE-NFC and the example projects only work on Raspbian Linux?
In general the projects should work on other Linux distributions too. However, we only tested it on Raspbian Linux. Please follow the instructions of the quickstartup, where the example projects are downloaded to your PC (x86 based system, either Windows or Linux) and installed there. Afterwards, you can copy the files to the Raspberry PI. For more information, please follow the quickstartup guide or watch the quickstartup-movie.
What are the default credentials of the Raspbian system image?
Username: pi
Password: raspberry
Can I use the I”C interface instead of the SPI interface?
Although the support of the I”C interface on the Raspberry Pi is not implemented into the NXP Reader Library, the EXPLORE-NFC board is prepared to be used in I”C mode. However, you will have to change some soldering bridges on the EXPLORE-NFC board.
Where can I get updates of the software projects described in the Quick Start Guide?
Updates of the example projects can be found either at
http://www.nxp.com/demoboard/PNEV512R.html or http://www.element14.com/exploreNFC
PN512
Where can I find documentation for PN512?
Almost all docs for this IC are public and can be found here: http://www.nxp.com/products/interface_and_connectivity/nfc_contactless_reader_ics/series/PN512.html#documentation
Does the PN512 support TR0 lower than TR0min ? Is the TR1 fixed or is it dynamicß If fixed, what is the value, and if dynamic, what is the range?
Yes. TR0min is about 300µs, but depending on the RxWait (RxSelReg) you can set values <300µs, if needed. TR1 is the time given to ensure that the PLL can lock on the subcarrier. Typically the PN512 is much faster than required by EMVCo. However, the exact timing varies and depends on antenna design parameters, the card etc.
NFC Forum Compliance
Can a system build on the EXPLORE NFC be NFC Forum certified?
Yes. The PN512 is a full NFC forum compliant IC that can be used to build NFC Forum compliant solutions.
I want to build a different antenna, therefore I need to define a different matching circuit:
What impedance should I tune to for PN512 with no booster?
Typically 50 ohms @ 13.56 MHz, but if maximum power is needed can go down to 35 ohms, or if less power is required can go as high as 80-100 ohms.
What tools do I need for antenna tuning and verification?
VNA, soldering station, oscilloscope with low capacitance probe, capacitor/resistor/inductor kits, calibrated ISO Reference PICCs, test cards, test phones/tablets if communication with NFC devices is desired.
Optional but very useful: full ISO test bench, if doing POS: EMV test bench, if NFC Forum certification is desired: NFC Forum test bench.
Where do I measure this impedance?
For designs with no booster do an S11 measurement using a VNA directly on the TX1 and TX2 pins. Typically we probe the pads of the L0 inductors which are connected to the TX pins. For designs with our standard booster design the impedance should be measured on the collectors of the BJTs, again you can probe the pads of the L0 inductors.
What EMC filter components should I use and what should be the cutoff frequency?
This depends on the size of your reader antenna, the size of the tags you are trying to read, and several other factors. Typically using 560 nH and 180 pF is a good starting point.
What are the requirements of the L0 inductors?
Must have current rating which is higher than the current flowing through TVDD (max for RC663 200 mA, max for PN512 100 mA). DC resistance should be as low as possible.