ST AN2399 Application note

AN2399

Application note

RFID library for SR176 tag management with STR71x

Introduction

This document describes a software and hardware RFID interface using the STR71x I2C peripheral and the CRX14 RFID transceiver.

The main purpose of this software and hardware package is to provide resources to assist the development of an application using an RFID tag.

The software interface is composed of library source files, include files and some application template source files.

January 2008

Rev 1

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www.st.com

Contents	AN2399

Contents

1	File organization of the RFID library . . . . . . . . . . . . . . . . . . . . . . . . . . .		. 3
2	Overview of radio frequency identification . . . . . . . . . . . . . . . . . . . . . . .		4
3	Operating ranges and applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		5
	3.1	Close coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
	3.2	Short range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
	3.3	Long range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
	3.4	Extended or very long range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
4	ISO standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		6
	4.1	ISO compatibility for ST devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
5	ST short-range contactless memories . . . . . . . . . . . . . . . . . . . . . . . . . .		7
	5.1	SR176 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7
	5.2	SRIX4K . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7
	5.3	SRIX512 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7
6	ST short range coupler: CRX14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		8
7	Overview of RFID reader using STR710 . . . . . . . . . . . . . . . . . . . . . . . . .		9
	7.1	CRX14 demonstration kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	9
	7.2	Interfacing with STR7xx using I2C peripheral . . . . . . . . . . . . . . . . . . . . .	12
8	RFID library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		14
	8.1	RFID reader/writer: the application layer . . . . . . . . . . . . . . . . . . . . . . . . .	14
	8.2	SR176 commands layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
	8.3	CRX14 commands layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
	8.4	I2C commands layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	20
9	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		21

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AN2399			File organization of the RFID library
1	File organization of the RFID library
	The following table presents the library modules:
	Table 1. RFID library modules
	File		Description
	Device_RFID.h	RFID definitions, type definitions and function prototypes
	Device_RFID.c	Protocol management to interface the CRX14 transceiver

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Overview of radio frequency identification	AN2399

2 Overview of radio frequency identification

Countless business applications, from product manufacturing to end-customer sales, can benefit from radio frequency identification (RFID). With RFID, logistics becomes more effective, stock handling is easier, traceability is guaranteed, cloning and counterfeiting can be avoided, antitheft protection is enabled, and warranty problems can be easily eliminated.

What is radio frequency identification (RFID)?

RFID technology uses radio communications to uniquely identify items, such as goods, people, or animals. It enables automated collection of information on identified items independently from their position, without the need of a direct optical link or human intervention. RFID also liberates the user from harsh or dirty environment concerns that restrict other automatic identification solutions such as barcodes. On top of that, RFID is used as a bi-directional data carrier since it allows information attached to the item to be written and updated on the fly.

What does a RFID system consist of?

An RFID system consists of several components including one or multiple contactless memory tags (or transponders), attached to the items to be labeled, identified, and traced, and handheld or fixed contactless read/write reader station units or coupling devices exchanging data with the transponder(s) by means of RF signals.

Contactless memory tags

Contactless memory tags (transponders) are the backbone of the RFID system since they contain data that allow the items to be identified. A contactless memory tag is made of a non-volatile memory associated with a radio frequency communication block, performing RF signal modulation, demodulation, power supply regulation, and an antenna. A transponder can be read-only (ROM), one-time-programmable (OTP), or read/write (EEPROM), and it can be embedded in various package formats (inlays, cards, etc.).

The reader

The reader (or reader station unit) is connected to an antenna that transmits and receives the radio frequency signal from and to the transponder(s). The reader sends an RF signal to the transponder’s antenna. This signal generates a voltage that is rectified and provides a power source to the transponder. The power transfer from the reader to the transponder is performed through an inductive coupling between the two coils in 125 kHz and 13.56 MHz systems. For ultra-high frequencies (UHF), the electric field generated by the reader is used to power the tag. In other words, the transponder does not need a dedicated power supply.

Passive and active tags

Two main families of transponders exist: Passive (battery-less) and Active. Adding a battery can bring several advantages, such as improvement of the reading range or continuous monitoring of temperature and pressure etc., but adds an extra cost. During the readertransponder communication, the RF signal generated by the reader is modulated according to the data to be sent. In the transponder-reader direction, no modulation is applied on the reader RF signal and the communication is done through load modulation in inductive coupling systems. The reader interfaces with the RFID system control host through a serial interface such as RS232, RS422/485, or USB.

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AN2399	Operating ranges and applications

3 Operating ranges and applications

The RFID operating ranges are defined by the distance between the transponder(s) and the reader.

3.1Close coupling

The close-coupling range includes the transponder-reader distances up to 5 cm. Brand protection, anti-counterfeiting of electronic goods and food consumables, as well as electronic purchases at vending machines operate in the close-coupling range. These applications employ low-cost readers operating with a limited number of transponders and require security features such as password, anti-clone, or cryptographic capabilities.

3.2Short range

In addition, RF technology systems are a universal solution for various ticketing applications, regardless of the means of transport used (public transportation or private car). Contactless systems can also be used in a wide range of access-control applications, including entrance systems to and within public buildings (in offices, for example), time and attendance systems, room logistics at hotels, locking systems, and amusement parks. These shortrange or proximity-range applications use low-cost transponders embedded in plastic cards or paper tickets and operate in the range up to 20 cm. Readers and transponders from different suppliers must be fully interoperable. Required security levels are satisfied through password, anti-clone, or cryptographic capabilities.

3.3Long range

RF transponders are a low-cost universal solution for tracking a wide variety of valuable assets (e.g. package delivery, animal tracking) and improving the product supply chain management from manufacturing to stock handling to distribution. Capable of storing traceability history, transponders provide accurate real-time information on each tagged item. Similarly, they can be used for anti-theft applications (using Electric Article Surveillance) or access control from a longer distance.

These long-range or vicinity-range applications operate within 1 m from the reader and typically involve a large number of low-cost transponders (100+), requiring reliable anticollision mechanisms and transponder-reader interoperability.

3.4Extended or very long range

Extended or very long-range (up to 10 meters) RFID systems will be instrumental in creating low-cost contactless solutions for new supply chains, logistics, and tracking applications that can offer improved efficiency, accuracy, and security standards to major manufacturers, retailers, and their customers.

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ISO standards	AN2399

4 ISO standards

The ISO organization devotes itself to definition and promotion of worldwide-recognized standards in the contactless area. 3 standards for objects operating in the 13.56 MHz frequency range have already been approved (ISO SC17 on identification cards and related devices):

●ISO10536 identification cards and contactless integrated circuits cards:

–Close-coupling cards (reading range below 2 cm).

●ISO 14443 identification cards and contactless integrated circuits cards:

–Proximity cards (reading range up to 20 cm).

●ISO 15693 identification cards and contactless integrated circuits cards:

–Vicinity cards (reading range up to 1 m).

This standard is part of the future SC31/ISO18000 standard, currently under discussion.

ISO standards are recognized worldwide and guarantee the full interoperability of transponders and readers from different suppliers.

4.1ISO compatibility for ST devices

ST contactless memories are ISO-compatible:

●ISO 14443 type B for short-range devices

●ISO 15693 or ISO18000-3 Mode 1 for long-range devices.

This application note refers to ST ISO 14443B short range RFID.

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AN2399	ST short-range contactless memories

5 ST short-range contactless memories

5.1SR176

ST’s SR176 is an ISO14443 Type B device. It offers 176 bits of EEPROM organized in eleven 16-bit blocks, a 64-bit UID and an 8-bit Chip_ID. Targeted markets are cost-sensitive applications such as industrial identification, access control, and low-value tickets that do not need to be modified more than a few times.

5.2SRIX4K

ST’s SRIX4K includes 4096 bits of non-volatile memory organized in three areas: the first area is an OTP (One Time Programmable) bit zone, in which bits can only be switched from 1 to 0; the second area provides two 32-bit binary down counters; and the last area which is a non-volatile memory split into 32-bit blocks (9 blocks are lockable). The SRIX4K supports France Telecom’s proprietary anti-clone function and anti-collision mechanism based on an 8-bit Chip_ID.

The SRI4K is based on the SRIX4K, excluding the support of France Telecom’s proprietary anti-clone function.

5.3SRIX512

The SRIX512 is a light version of the SRIX4K with 512 bits of non-volatile memory. All three devices (SRIX4K, SRI4K, SRIX512) are designed for short-range applications such as consumable products identification, anti-counterfeiting, or high-end ticketing solutions.

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