RFID

RFID

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  • Milosch Meriac
    Milosch Meriac
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    Open RFID Reader Design and RFID Protocol Firmware Stack
    The OpenPCD Project ( http://www.openpcd.org ) published a free hardware & software design for accessing Proximity Coupling Devices (PCD) based on 13,56MHz communication. The device is able to screen informations from Proximity Integrated Circuit Cards (PICC) conforming to vendor-independent standards such as ISO 14443, ISO 15693 as well as proprietary protocols such as Mifare Classic.

    The intention of the OpenPCD project is to offer the users full hardware and software control of the RFID signal and to provide different output signals for screening the communication. The embedded low cost 32 bit ARM processors allows intelligent standalone reader design with self-contained RFID firmware with a full RFID protocol stack implemented. This allows applications like door locks etc. The external interfaces allow access to bus system like RS485. With already existing Free Software from the OpenMRTD ( http://openmrtd.org ) project for implementing the PCD side protocol stack of various RFID protocols, this project will happily extend the free toolchain around RFID verification. Our software is based on a free GNU ARM toolchain. The firmware can be updated over USB - no special programming devices are needed.

    Hardware

    The OpenPCD hardware design is based on the CL RC632 Multiple Protocol Contactless Reader IC from Philips, which supports ISO 14443 A&B, ISO 15693, Mifare and ICODE protocols. This reader IC is connected via SPI to an ARM Microcontroller. We chose the AT91SAM7S128 with a 32-bit RISC processor architecture, 128 kbytes Flash and 32 kbytes SRAM. The Microcontroller is accessible via USB-B-MINI plug and optionally via a 20-pin JTAG header. The design provides several interesting interfaces for monitoring and studying the RFID signal:

    * serial RS232/TTL interface on 1x5 header
    * two-wire I2C interface on 1x4 header
    * SAM-BA reset control on 1x4 header
    * 4 analog inputs on a 1x5 header
    * bootloader reset via push-button
    * HF output of the trigger signal on U.FL connector
    * HF output of the AUX signal (intermediate demodulated steps) on U.FL connector
    * HF output of the MFOUT signal (demodulated digital signals) on U.FL connector
    * optional 1x3 header for an external antenna

    This reader design is particularly interesting for everyone interested in RFID protocols and security, because of its many interfaces. You can modulate arbitrary waveforms onto the 13.56MHz carrier by bypassing the RC632 modulator/encoder and using the PWM (Pulse Width Modulation) or SSC (Synchronous Serial Controller) of the AT91SAM7 micro-controller. On the RX side, you can also bypass the RC632 decoder and use the SSC to sample arbitrary data, provided it is on a ISO-ocnformant sub-carrier frequency.

    Many of the internal signals can be routed to U.FL connectors on the PCB, e.g. if you want to look at certain intermediate signals on an oscilloscope, spectrum analyzer or even sample it with some high-speed ADC like the USRP SDR ( http://www.gnu.org/software/gnuradio ).
    • 19 Sep 2006, 12:40 pm