Radio frequency identification (rfid) technology smoothly into our many aspects of everyday life.
Inventory management from the supermarket to the quick collection, this technology is changing with many existing applications and support new applications. In the rfid front end, "signal chain" from effective appliance small label, pass information to one or more rfid reader, when the label to appear in a specific area, the reader detection. In the rfid back-end, server-based system to maintain and update the label of the database. Rfid system block diagram shown in Figure 1.Today, most rfid reader using multiple processors to meet application requirements.
Usually one is connected (ADCs) and digital-to-analog converter (dac) of the signal processor. The other is a local or remote server communication network processor, used for information storage and recovery. But the blackfin processor series, etc. to manage these different features — signal conversion and network connections.
Figure 1 rfid system block diagram
This article first introduces rfid technology and how it can support current and future applications.
Then, the functionality of RFID readers, this article will examine run in rfid reader and server connection needed basic software components.Rfid system overview
Rfid is a radio frequency (rf) transport identification code, classification code and (or) tracking target communication system.
Each destination has its own RFID tags (also called a transponder). Total system with a label reader receives each label of rf signals. Reader's embedded software management query and receive the label information for decoding and processing, and storage-system communication, collection label database and other related information.Application of rfid
Rfid technology allows simultaneous monitoring of multiple items, not people who go to "contact" for each item (for example, using a handheld bar code scanner), so it can support many new applications.
To use this automatic identification technology of application covers many different areas, such as control management, logistics management, security monitoring and toll charges, etc. The following is now the use of RFID systems some common applications.● In supermarket food shelves and boxes, ability to write using tags (you can include additional information, such as the date of sale) for food, and on the shelf goods for better management.
In addition, you can automatically rearrange to maintain correct stock on shelves.● In library automatically manage information of lending and restitution.
In the past, these items are identified with a label to, each time you must use the barcode scanner to read.• Clothing brand identification on their goods.
Use the label identification number (id) that can be identified this product is genuine or counterfeit goods.● In the pharmaceutical industry against counterfeit drugs.
● In sports competitions, accurately track the marathon runners of the process.
Rfid reader
Rfid reader provides the labels and Terminal tracking and management system.
Although it may take a variety of different sizes of packaging, but is usually very small for installation on a tripod or wall. In addition, depending on the application and conditions of work, you can use multiple reader in order to fully cover the area. For example, in a warehouse, there may be an overlay network to ensure that when goods move from point a to point b, all goods are able to have 100% of the queries and records.In short, the reader function has three main components.
The first part is to send and receive functionality to the label and the separation of individual items to keep in touch; the second part is initialized to receive information; the third part is a linked server that is used to pass information to the management bodies.Rfid system reader must be able to handle in the effective area at the same time there are multiple labels, which in the space of the zone memory limit in multiple tags are very important in applications.
In the presence of multiple readers and tags, the main problem is a conflict, because multiple reader issues a query, you can have multiple labels at the same answer.
There are many ways you can avoid this problem. The most common method is to use a time division multiplexing algorithm. Readers can be set at different times, and labels can be set to a random interval after responses. If the embedded software has the ability to implement this functionality, you can increase your flexibility.Rfid transponder
A rfid tag includes a IC chip (used to save the label is located on the individual information items), an antenna (usually printed circuit antenna for receiving information from the reader's rf and sent information) and contains a shell of the label.
Use rfid tags can be many different things, from all types of goods to the animals, including humans.
Tags to readers of distance is a very important system variables, it directly affected by the impact of the technology. Commonly used various label technology include the following.1 passive tags
The simplest type of label is passive tags.
It is designed to take advantage of the reader's rf energy sent to power supply, it has no integrated battery size and cost. Passive tags are very cheap, good mechanical robustness and overall size is very small (about the size of a fingernail). However, because the passive labels receive power and it to the RFID reader is proportional to the physical distance, so the class label of disadvantage is its reading range is limited.When it comes to the scope, frequency and the selection of the rf link of actual scope.
Low frequency (lf) label usually 125 ~135khz band, because their scope is limited, so its main purpose is to access control and animal label. High frequency (hf) tag primarily work in 13.56mhz band, the range of allowed work about a foot or two feet. The primary purpose of the hf tags are simple one-to-one object read, such as access control, billing, and track the library books and other items.Ultra-high frequency (uhf) tag primarily work in 850 ~ 950mhz band, allow 10 feet even farther.
In addition, readers can also query many uhf labels, and one-to-one hf tags read process. This feature also helps meet in limited areas within more than one reader's needs. Because of this feature, uhf tags in industrial applications, it is common for inventory tracking and control. But a uhf tag primarily the disadvantage is that you cannot effectively penetrating liquids. This makes them cannot be used to filled with liquids, such as drinks and the human body. In tracking those objects, typically using hf tags instead.2 semi active tag
Like passive tags, half of the active tab is RF energy returns to the tag reader to send identity information.
However, it also contains a battery to labels powered ic part so that it can support some interesting applications, such as in each place the sensor in the label. This approach, each transponder not only can send static identity data, you can send some live properties, such as temperature, humidity and the time and date. Through the use of only for ic and sensor power supply by battery, half-active tags can be realized in cost, size and scope of the compromise between.3 active tag
Active tags with integrated battery for label ic (and all sensors) and rf transmitter power, it is better than half active label goes further.
Active tags extend the work of a large (100 meters), this means that the cargo in the reader's speed can be better than passive and semi active label system speed. In addition, active tags can carry more product information, not just a simple product ID code.Rfid reader software architecture
The above describes the basic functionality of rfid readers, the following will explore how to use a processor to implement these features.
Rfid reader software architecture of the three modules is: back-end server interface, middleware and front end tag reader algorithm. Although the software architecture of the unit, they can be run simultaneously in a blackfin processor.Back-end server and connection
Typically, RFID readers including one network cell to an rfid reader events connected to the hub server.
This back-end network interface may be wired Ethernet (ieee802.3), wireless Ethernet (ieee802.11a/b/g) or such as zigbee (ieee802.15.5) Ethernet. The central server running a database system, its features include matching, tracking and storage. In many applications, there will be an "alert" feature. For supply chain and inventory management system, this could be the reorder reminders; for security applications is one of the security police.When you communicate with the back-end servers, the use of running uclinux OS's high-performance embedded processor to build reader has a great advantage.
The TCP/IP protocol stack of robustness and availability of the sql database engine and other key factors in reducing the development process can be a huge burden for the development and integration.Middleware
In the session, rfid middleware is between the front-end rfid reader and back-end enterprise systems software translation layer.
Middleware filter reader data, thereby ensuring no more than once read or invalid data. In the early days of rfid systems, middleware running on the server. However, in reader complete rfid data filtering and more generally, in the send data through the corporate network. This enhanced functionality is embedded processor brings this application of an additional benefits.Front-end reader
Signal processing is placed in front of the reader system.
This kind of signal processing are usually contains a large number of filtering and transformation operations, that is why it is necessary to adopt a very strong signal processing performance of the processor.Processor for RFID readers
Blackfin processor provides wired and wireless network connections.
Adsp-bf536/7, processor chips have a 10/100baset Ethernet mac sublayer. In a wireless connection, available through spi and sport peripheral interface directly connected to the ieee 802.15.4 zigbee and without consumption 802.11 chipset for all of the processor bandwidth can achieve transmission rates.Processor parallel peripheral interface (ppi) can directly connect the adc/dac.
Some processors including two ppi, you can further extend the functionality of the system.Additionally, the processor of the feature makes it a two-dimensional barcode application particularly attractive because it can be done on the same device system control, network connections, and image processing.
From the perspective of the processor software, rfid Reader products including connection to the mixed-signal front-end to the required driver.
In addition, a dma transfer data through the drive in the system is also very useful. There are also based on uclinux OS network protocol stack as well as the SQL database engine. From a systems point of view, additional features, such as 802.11 wifi card, usb thumb drive and compactflash card interface, and so on, canTo rapidly integrate with blackfin devices together.Conclusions of the
As we have seen, rfid applications no longer require a dedicated signal processors for adc and dac connections, as well as micro-controller for network connections.
Blackfin processor series, etc. can complete network connectivity and control function, in order to complete the dongle and pattern matching algorithm to leave enough room for performance. This also reduces the next generation of rfid applications in material costs and accelerates time-to-market.
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