Abstract: In the EPC technology and the radio frequency recognition (RFID) in the technical rapidly expand and the widespread application, the RFID middleware already was the RFID system’s energetic main center. This article narrated the EPC system, the RFID middleware, and has designed one in this foundation based on EPCglobal ALE the standard embedded RFID middleware, enables the standard the RFID middleware to be possible to integrate on the microreader, realizes the integrated thought.
Key word: Product electron code; Application layer event connection; Radio frequency recognition; Middleware; Embedded system
1 Introduction
While the RFID technology rapidly expand and obtains more and more widely should, also followed was having two problems: First, in a so big market, has the numerous agreements, but also has each kind of use and the operation different microreader of all forms, this has hindered the RFID technology large-scale application seriously; Second, how will the conformity, filter and transmits these data to enable the enterprise not to can obtain by the massive data submergence the advantage which the RFID technology will bring will be the another urgently needing solution important question.
In this case, the RFID middleware transports, thus lives, and obtained the fast development, the RFID middleware has been possible to shield each kind of different specification model the microreader and each kind of different protocol standard label, let the upper formation application software obtain the unification, the invariable connection; Moreover, its also responsible conformity and the filtration data, produce the report form, causes the mass data the transmission and possibly applies into.
At present, the domestic and foreign RFID middleware volume is big, designs is only suitable for PC machine, cannot transplant directly to the embedded microreader, this article realized one kind to be possible to transplant, might move directly on the embedded microreader equipment, based on ALE standard embedded RFID middleware.
2 EPCglobal ALE standard
EPC[1] is Electronic Product Code (product electron code) the abbreviation, is the American Massachusetts Institute of Technology’s automatic diagnosis center (the Auto-ID center) proposed that its main idea is participates in a networking goods distribution electronic tag for each, this label saved a world only EPC code, when product through microreader, reads the data by the RFID technology, obtains the corresponding EPC code, finally through completes the corresponding EPC code with the Internet connected server the analysis.
The EPC system mainly by the EPC code, the EPC label, the EPC reader-writer, the EPC middleware, PML (physical mark language) the server, ONS (object analysis service) the server and so on is composed. The system agreement mainly by the RFID communication protocol, the application event manages the (ALE) agreement and so on to be composed.
EPC the ALE[2] agreement is between the EPC middleware and the microreader module and the customer application procedure connection agreement. How did this agreement define the customer to be possible to be overanxious with the conformity from many microreader’s EPC labels, and faced the different enterprise application procedure and the microreader has defined the unified connection, even if like this rear end the application procedure increased or changes by other software substitution, or the RFID reader-writer’s type changed, increases when and so on situations occurred, other parts do not need to make the revision. ALE contains the treating processes include: Receive from or many data pool EPC label codes; (Enterprise application procedure) requests according to the client side by certain time-gap conformity data, filtration redundant and is not interested the EPC code; According to client side request by different form pack transmission report. The ALE agreement is based on the event, the working may for the synchronized pattern or the asynchronous pattern, has the high request to timeliness, but docks the EPC data storage time which receives not to request to be very long, when receives after the EPC data was been already related all event processing and transmits, this data might delete. The transmission data packet’s document format is the XML form, must transmit for the customer or other microreader’s data encapsulation into XML document, the data file which, after the client side will receive analyzes the corresponding data message according to the corresponding stipulation’s XML form. ALE in EPCglobal position like chart 1, located at primitive EPC examination event level (RFID label reading level) and between application commercial logic level.
Figure 1 ALE in EPCglobal network architecture position
3 middleware realize the plan based on EPCglobal ALE the standard embedded RFID
3.1 this article designs the RFID middleware mainly realizes the characteristic
This middleware skeleton in the embedded system, it is different with the movement on the common computer’s middleware, realizes the RFID middleware function on the embedded system, enables the middleware to be possible to integrate on the microreader. This strengthened microreader’s performance at the same time, causes the tradition ” mute ” the microreader to become is worthy of the reputation ” intelligently ” the microreader, on the other hand, causes the RFID middleware and the microreader forms a whole, has manifested ” All in a box ” the thought that like this both has facilitated the RFID system’s installment, and reduced the cost. This middleware simultaneously supports EPCglobal the ALE standard, this standard application is widespread, may apply in the different specification model microreader, supports many kinds of labelling standards, provides the unification invariable standard interface for the upper formation application, has the very strong versatility and the compatibility. This middleware also has the network function, has the ordinary web server and the database function, this has realized the microreader and the microreader, the microreader and the client side network service and the data buffering, and between the network data is seals into the standard the XML form transmission.
3.2 embedded RFID microreader hardware system platform
This embedded RFID microreader has three basic hardware modules: Antenna and radio frequency module, DSP baseband board module, controlling system module. The antenna and the radio frequency module is responsible for the radio-frequency signal the launch and the receive, the DSP baseband module is responsible for the signal conversion which receives to the radio frequency module for the digital signal, carries on the CRC verification, and passes to the data through the HPI connection the controlling system module, simultaneously is also responsible for the control command which sends out to the controlling system module carries on analyzes and realizes. Controlling system module primary cognizance overall system’s control and label’s processing, with customer service response.
The controlling system module is mainly composed of ARM(AT91RM9200) and the peripheral component, the operating system is arm-linux2.4.19. The middleware will move in this module.
3.3 embedded RFID middleware software architecture
This system uses the lamination the software architecture, the underlying bed is the Linux operating system and various peripheral devices connection actuation module, including the DSP actuation, net mouth actuation and serial port actuation. The intermediate level is GoAhead the Web server and embedded database SQLite, the upper formation is the microreader management, ReadProtocol and the ALE level, as shown in Figure 2.
Figure 2 software architecture
The operating system is the middleware foundation, uses embedded Linux to take this embedded RFID middleware the operating system, Linux supports TCP/IP, HTTP and so on many kinds of agreements, has omitted the agreement transplant and so on complex work, reduced the middleware development difficulty, reduced the development cycle. The DSP actuation, the net mouth actuation, the serial port actuation, are the RFID microreader development actuation modules, only need make a revision in the linux support. The Linux transplant technology was already mature, this article does not make the detailed elaboration.
GoAhead the Web server is one section mainly faces embedded system’s Web server, the major function module has the security module, the GoForm module, the CGI module, SSL (Secure Sockets Layer) the module. And in the security module contains the memory database module, the primary cognizance memory user information, as well as provides the security safety mechanism. GoForm module primary cognizance processing customer submission form data, and by web page’s form returns corresponding processing result. CGI module main processing customer CGI request. The SSL module has realized the SSL agreement in GoAhead. It is this article designs the embedded middleware the basic software construction, system’s all network development is carries in this construction, GoAhead the web server retransmits the platform and the module load bearing platform as a middleware data, between the microreader and the client side, between the microreader and microreader’s data communication is server completes by GoAhead the Web, the ALE agreement realizes the module (the ALE module), the data bank administration module, the microreader administration module, ReaderProtocol the Server module and so on development is also the establishment in the GoAhead foundation.
The database uses SQLite, SQLite is one kind exquisite, free, opens the source the embedded database application software, it has provided the standard SQL language, because and its working speed is quick, has satisfied the data real-time request. It may integrate in the application software, may also move independently, this system selects it is mainly carries on smooth, the filtration as well as to the primary data screens the data according to the client side order.
Reader Management is the microreader administration module, is responsible to establish this microreader’s active status and the working pattern.
Reader Protocol is the microreader agreement server, it is responsible to manage possesses with this middleware microreader connected microreader, is Reader the Protocol agreement on middleware realization.
ALE Server is the ALE agreement server, it is this system’s core, is responsible to provide the standard to the upper formation application procedure the ALE connection, realizes each ALE connection.
3.4 ALE standards in this embedded middleware system’s realization
How to realize EPCglobal in the RFID middleware’s software system the ALE standard, is this system development core. In the system, we developed the ALE module to use to realize EPCglobal the ALE standard, because the middleware used the basic software construction was GoAhead the Web server, it has made a module load bearing platform, might insert the ALE module well in above. The ALE module in the GoAhead position as well as ALE module’s processing flow as shown in Figure 3.
Figure 3 ALE module in GoAhead position as well as its processing flow
The client side transmits ALE with the http agreement the order the XML document for the server end, the server end receives this xml document in the GoAhead advancement, then seals this document the news, fills on the concrete message type according to the different connection function, then passes to the ALE advancement with the order news formation, takes out in the ALE advancement from the order news formation the news, gives according to the news type the XML document the corresponding function to analyze and to do the corresponding operation.
In the ALE module, regarding each user definition’s ECSpec[2] (it is a complex construction of data type, had stipulated how to process and complete an event cycle), the system has realized four conditions: Undefine, Unrequested, Requested, Active. Undefine expressed that this ECSpec has not been able to use again now, soon is released; Unrequested expressed that this ECSpec is at now does not have the user subscription condition; Requested expressed that this ECSpec is at now has the user to subscribe the condition; Active expressed that this ECSpec is just about to the triggering thread to manufacture and the transmission report form condition now. Each will not be in Undefine ECSpec to correspond an appropriation sub-thread (in the ALE advancement foundation), this sub-thread will process the concrete data takeoff which this ECSpec stipulated that the report form manufacture and the transmission. Each ECSpec correspondence’s sub-thread will not disturb mutually, the sub-thread only (ALE advancement original thread) has the relation with the main thread, realizes main thread antithetical couplet thread triggering and the control through the condition variable mechanism.
The system when requests according to corresponding ECSpec carries on the data takeoff, the filtration, the conformity, with the database system module mutually will unify. The database system module the first primary data which reads from the microreader carries on the filtration redundant unnecessary EPC code, and shields each kind of different microreader data format the difference, after unified data format, sends in database SQLite the data, becomes the database operation the data pool. System’s operations and so on data takeoff are carry on this data pool, these operations are through language realize using SQLite own standard SQL. After the corresponding data manipulation completes, must carry on the data pool in expired data the deletion.
After having completed the data extraction and the conformity, the system will correspond the data basis ECSpec the specific request to seal into the XML form, and by the TCP way transmission for the user who subscribes.
4 Concluding remark
This article author studies the innovation spot is in based on EPCglobal the ALE standard, how to design in skeleton’s in embedded system RFID middleware aspect, proposed the quite clear mentality, and deferred to this mentality to realize based on EPCglobal ALE the standard embedded RFID middleware, after the compilation run test, this system volume small, stable reliable, timeliness good, the parallel processing speed was high, but widely applied in the embedded RFID microreader system.
Reference:
[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].
http://www.epcglobalinc.org/standards_technology/EPCglobal_Application_Level_Events(ALE)_Specification_v1. df
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