USB-NFC INTERFACE

V diplomskem delu je predstavljen razvoj čitalnika kartic, ki deluje v frekvenčnem območju 13,56 MHz in pridobljene informacije posreduje preko USB komunikacije na osebni računalnik. Naprave, ki delujejo v tem frekvenčnem območju morajo ustrezati standardom tehnologije NFC (ang. Near Field Communication). Standard, s katerim mora biti čitalec skladen, je ISO/IEC 14443, saj definira večino NFC komunikacije, od fizičnih karakteristik, moči radio frekvenčnega polja do inicializacij in protokolov za prenos. Za vso komunikacijo skrbi mikroprocesor, ki na eni strani komunicira z računalnikom preko vodila USB (ang. Universal Serial Bus) in na drugi strani z integriranim vezjem, ki podpira NFC tehnologijo. USB povezavo smo realizirali tako, da se mikrokrmilnik računalniku predstavi kot HID naprava, natančneje kot tipkovnica. S tem dosežemo, da ni potrebno razviti programske opreme za osebni računalnik, ampak lahko za izpis uporabimo le npr. Beležnico (ang. Notepad). NFC komunikacijo smo realizirali z uporabo integriranega vezja MFRC531, ki je skladen s standardom. Njegova naloga je, da prebere identifikacijo oznako kartice in jo po SPI vodilu pošlje na mikrokrmilnik. Diplomsko delo vsebuje tudi načrtovanje in prilagajanje antene, ter meritve kakovosti signalov, pri brezkontaktnem komuniciranju.Design and development of card reader which is working in frequency range of 13,56 MHz and obtained information send over USB port to personal computer is presented. Devices that are operating in this frequency range must comply with valid standards of NFC technology. The card reader must be coherent with standard ISO/IEC 14443, since it defines most of NFC communication, like physical characteristics, radio frequency power and signal interface, initialization and transmission protocol. The communication is handled by a microcontroller, which on one side communicates with a personal computer over the USB port and on the other side with integrated circuit which supports the NFC technology. We implemented the USB connection with computer by that the microcontroller enumerates itself as a HID device, namely as a keyboard. Since the keyboard driver is readily available on a PC, additional design of custom driver can be avoided. Instead, a simple text editor (e.g. Notepad) can be used to display received characters. NFC communication was programmed using standardized integrated circuit MFRC531. Its functionality includes reading the ID of card tag and sending it via SPI bus to the microcontroller. Design and matching of antenna with measurement and assessment of its Q-factor is also presented