Based on ALE standard embedded RFID middleware design

Summary: in the EPC technology and radio frequency identification (RFID) technology is developing rapidly and widely applied, RFID middleware is the spiritual center of the RFID system.

This article describes how EPC RFID middleware system, and on this basis to design a standard based on EPCglobal ALE embedded RFID middleware that enables standard RFID middleware can be integrated in the reader's thoughts on that achieve integration.

Keywords: electronic product code; the application-tier event interfaces; RFID; middleware; embedded systems

1 Introduction

In the rapid development of RFID technology and increasingly broad should, also accompanied by two issues: first, in a such a large market, the existence of numerous protocols, there are various use and operation of different kinds of readers, which seriously impedes the large-scale application of RFID technology; second, how to consolidate, filtering and transmit these data so that enterprises will not be a large amount of data covered, from obtaining the benefits of RFID technology is another pressing and important issues.

In this scenario, the RFID middleware migration and health, and fast development, RFID middleware can shield the various specifications of the reader and the various protocol standard labels, so that the upper application software be unified, unchanging interface; in addition, it is also responsible for integration and filtering data, generate reports, make massive data transfers and applications.

At present, domestic and international volume of RFID middleware, the design is only applicable to the PC, you cannot directly ported to embedded reader, this article implements a portable, can be directly run on embedded reader device, based on ALE standard embedded RFID middleware.

2. EPCglobal standard ALE

EPC [1] is the Electronic Product Code (electronic product code), is a United States MIT Auto-ID Center of (Auto-ID Centre), the main idea is to each participating in networked product distribution of an electronic tag, which stores a world unique EPC code, when the product through the reader, RFID technology to read data, get the corresponding EPC code, concluded with the adoption of Internet-connected server to complete the corresponding EPC code analysis.

EPC system is mainly composed of EPC encoding, EPC tag, EPC reader, EPC Middleware, PML (physical markup language) server, ONS (object name resolution service) server.

System Protocol is used primarily by RFID communication protocol, application event management (ALE) Protocol, etc.

EPC ALE [2] Protocol is EPC Middleware and reader module and client application interface protocol. The Protocol defines how a client can unnecessary worry and consolidation from multiple readers of EPC labels, and for different enterprise applications and reader defines a unified interface, so even if the backend application increase or replaced by other software, or the types of RFID reader has changed, the increase occurs, other components do not need to be modified.

ALE contains processing: received from one or more data sources of EPC tags codes; According to the client (Enterprise applications) to a certain time interval for the consolidated data, filtering duplicate and are not interested in EPC codes; according to client requirements to different forms of packaging to send the report. ALE Protocol is based on the event, the work can be synchronous or asynchronous mode, the real-time have higher requirements, and received the EPC data storage time does not require a long, when notified of EPC data has been associated with all event handling and sent, the data can be deleted. Send a packet file format is an XML format, all you want to send to customers or other reader data package as an XML file, the client will receive the data file after the provisions under the corresponding XML parsing out the corresponding data information. ALE in EPCglobal's position as in Figure 1, is located in the original EPC test event layer (RFID tags reading layer) and applications between the business logic layer.

　　

Figure 1 ALE in the EPCglobal network structure of location

3 based on EPCglobal ALE standard embedded RFID middleware solution

3.1 this article designed RFID middleware main features

The middleware frameworks for embedded systems, it is different from running in the General computer middleware, in embedded systems implement RFID middleware, enabling middleware can be integrated in the reader.

This enhances performance, enabling the reader to traditional "dumb" readers become truly "intelligent" reader, on the other hand, RFID middleware and reader to form a whole, and embodies the "All in a box" thinking, and this facilitates the installation of the RFID system, and reduce costs. This middleware while supporting EPCglobal ALE standard, the standard widely used, can be applied to different types of readers support multiple label standard for upper application provides a uniform interface to the same standard, with strong interoperability and compatibility. This middleware also has network capabilities, with a normal web server and database functionality, which enables readers and reader, the reader and the client network traffic and data buffer, and the network data is encapsulated into a standard XML format for transmission.

3.2 embedded RFID reader hardware platform

The embedded RFID reader has three basic hardware module: antenna and RF module, DSP baseband

Plate module, master system modules. Antenna and RF module responsible for RF signal transmitting and receiving, DSP baseband module responsible for the radio frequency module of the received signal is converted to a digital signal, CRC, and put the data passed via the HPI interface control system modules, also responsible for the main control system modules of control commands for resolution and realization. Master system modules are mainly responsible for the entire system of control and label processing, and customer service response.

Master system module mainly by ARM (AT91RM9200) and peripheral devices, the operating system as arm-linux2.4.19.

Middleware will run on the module.

3.3 embedded RFID middleware software architecture

This system uses a hierarchical architecture of software, the lower is the Linux operating system and the peripheral interface driver modules, including DSP driver, driver and serial ports.

The middle layer is the GoAhead Web server and the SQLite embedded database, the upper management of the reader, the ALE layer ReadProtocol and, as shown in Figure 2.

　　

Figure 2 software architecture

The operating system is the foundation of middleware, using embedded Linux as the embedded RFID middleware, operating systems, Linux supports TCP/IP, HTTP and other protocols, eliminates the complex work agreement transplantation, reduces the difficulty of developing middleware, shortened the developing time.

DSP-driven, ports, serial driver, the driver is for RFID reader development driver modules, support on linux for some changes. Linux transfer technology is mature, this article does not explain in detail.

GoAhead Web server is primarily intended for embedded systems with the Web server, the main function module has a security module, GoForm module, the CGI module, SSL (Secure Sockets Layer) module.

Which security module also contains the main memory database module, is responsible for storing user information, as well as provide confidential security mechanisms. GoForm module is primarily responsible for handling the customer submits the form data, and web page returns the appropriate result. CGI module mainly handle customer CGI requests. SSL modules enable the GoAhead SSL protocol. It is this design for embedded middleware basic software architecture, systems of all Web development is in this framework, GoAhead web server as the middleware a data forwarding platform and module loading platform, readers and clients between the reader and the reader data communication between the GoAhead Web server to complete, ALE Protocol implementation module (ALE module), database management module, the reader management module, Server module, ReaderProtocol development is established on the basis of the GoAhead.

The database uses SQLite, SQLite is a small, free, open-source embedded database application software, which provides a standard SQL language, and because their work faster to meet the requirements of real-time data.

It can be integrated in the application software, or can be run as stand-alone, the system selects it mainly on original data smoothing, filtering, and according to the client's command to filter data.

Reader Management is Reader Management module, is responsible for setting the reader work status and operating mode.

Reader is a Reader Protocol Server Protocol, it is responsible for managing all the middleware reader connected reader, is the Reader Protocol Agreement on realization of middleware.

ALE ALE Protocol Server is a server that is the core of the system, is responsible for the up-tier application provides a standard interface for all ALE ALE interface.

3.4 ALE standard in the embedded middleware system

How RFID middleware software system for EPCglobal ALE specification, is the core of the system development.

In the system, we have developed a module for ALE EPCglobal ALE standard, due to the use of basic middleware software architecture is the GoAhead Web server, it made a module loading platform, in the above works well embedded ALE module. ALE module in the location in the GoAhead and ALE module handling process as shown in Figure 3.

　　

Figure 3 ALE module in the location and its in GoAhead processes

Clients using the HTTP protocol to send a command in the XML file ALE to server-side, server-side in the GoAhead process receives the xml file, and then the file is packaged as a message, depending on the specific interface functions fill the message type, and then use the command message queue to process, in ALE ALE processes from the command Message Queuing message, depending on the type of message to an XML file to the corresponding function to resolve and do the appropriate action.

In the ALE module, for each user-defined ECSpec [2] (it is a complex data structure types, provides how to process and complete an event cycle), the system has realized the four States: Undefine, Unrequested, Requested, Active.

Undefine the ECSpec now is no longer in use, is about to be released; Unrequested represents the ECSpec now in no user setRead status; Requested the ECSpec is now in the user subscription status; Active means the ECSpec now about to trigger thread to create and send reports of the State. Each is not in the ECSpec will correspond to Undefine a proprietary child threads (in the process of creating ALE), threading the ECSpec specific required, making data extraction and send the report. All the child threads ECSpec will not interfere with the child thread with the main thread (ALE processes the original thread), through the condition variable mechanisms of the main thread to child thread to trigger and control.

System in according to the requirements of the corresponding ECSpec data extraction, filtration, consolidation, and database system modules together.

Database system module first read from the reader of the original data to filter out duplicate superfluous EPC codes and shielding various reader data formatting differences, uniform data format will enter data into the database, SQLite, become a source of data for the database operation. System for data extraction, and so is in the data source, these operations through the application of the standard SQL language SQLite itself. In the corresponding data operation has finished, you must put the data in a data source to delete outdated data.

In the completed data extraction and integration, the system will treat the data according to the specific requirements of the corresponding ECSpec encapsulated into XML format, and to send TCP to subscribe to the user.

　　

4 closing

The writer is an innovative idea is based on EPCglobal standards, how to design ALE architecture for embedded system RFID middleware area, made more clear, and in accordance with the idea of implementing a standards based on EPCglobal ALE embedded RFID middleware, compile to run tests, the system volume is small, stable and reliable, real-time, and parallel processing speed is high, it can be widely used in embedded RFID reader system.

　　

　　

Reference documents:

[1] AUTO-ID Center, The EPCglobal Architecture Framework, [EB/OL].

http://www.epcglobalinc.org/standards_technology/ Final-epcglobal-arch-20050701 pdf

[2] AUTO-ID Center,The Application Level Events (ALE) Specification Version 1.0 [EB/OL].

[3] Wang Lung-embedded Linux system design and applications-Tsinghua University Press, 2001

[4] Klaus Finkenzeller s, Chen Tai is compile. radio frequency identification (RFID) technology for Beijing: electronic industrial press, 2001

[5] Lu Dong Xin, Li Qiang, Liu Chang. Based on the ARM of RFID readers design [J]. a micro-computer information, 2006, 10-2: 286-288