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.
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