“The RFID control system consists of two parts: a reader and an Electronic transceiver. The reader sends electromagnetic pulses through an antenna, and the transceiver receives the pulses and sends the stored information to the reader as a response.
Radio frequency identification de-vice RFID (RFID) uses radio frequency force to read data and identify the target object. Compared with technologies such as bar codes or magnetic strips, the use of RFID technology to identify electronic tags, based on the wireless link between the reader and the transceiver, can obtain faster) (1J stable data reading ability um if the reader reads There are multiple tags in the write range, which will cause the reader to decode the received signal incorrectly. This requires the use of anti-collision algorithms to prevent collisions of data. I (IJ-induced reduction in system efficiency) is designed and implemented. An electronic tag reader based on the XScale processor Intel PXA270, which can identify batches of tags at a long distance, analyzes the original prisoners generated by the tag collision of the radio frequency identification system, and introduces the anti-collision algorithm to solve the tag collision. This is a high The case of automatic identification of low-performance electronic tags.
1 RFID system
The RFID control system consists of two parts: a reader and an electronic transceiver. The reader sends electromagnetic pulses through an antenna, and the transceiver receives the pulses and sends the stored information to the reader as a response.
1.1 Hardware system
The hardware system structure of the electronic tag reader is shown in Figure 1. The hardware system uses Intel’s PXA270 industrial-grade embedded processor based on the XScale core as the processor of the electronic tag reader. The PXA270 chip integrates Intel Wire-less MMX wireless module, 32KB instruction Cache, 32KB data Cache, MMU , External memory controller, LCD controller, NOR Flash controller, 4 DMA channels, 3 channel UART, 2 I2C bus controllers, 1 IIS bus controller, 4 channels PWM timer and an internal timer, GPIO Interface, touch screen interface, USB Host and II USB Device controller, SD Card/MMC controller, etc. The wireless sending and receiving data module of the reader is composed of Intel 81000 chip, crystal oscillator and antenna.
1.2 Software system
The software system of the reader includes system initialization module, electronic tag and reader communication module, LCD touch screen Display T module and other functions. The software development environment uses RT-Linux operating system. The software architecture of the electronic tag reader is shown in Figure 2.
1.3 Device driver
The device driver is the interface between the operating system kernel and the machine hardware.
The interrupt handler scans the special keyboard, confirms the keystrokes, and obtains the scan code. The flowchart of the keyboard driver is shown in Figure 4.
2 Electronic tag anti-collision strategy
In the communication process between the electronic tag and the reader, if there are multiple tags sending data at the same time, there will be conflicts, resulting in data transmission errors. In order to improve the stability of the reader system, an anti-collision strategy must be adopted to avoid tag data conflicts.
2.1 ALOHA dynamic frame algorithm
ALOHA algorithm is an effective anti-collision algorithm.During the execution of the ALOHA algorithm, each tag has an ID number. If the tag enters the effective recognition range of the reader, it will automatically send its own ID to the reader, and the reader will transfer data to the reader. 10. The recognition time of each tag is Tmo reader
It can be seen from formula (5) that when the number of tags is equal to the number of slots in the frame, the efficiency of the reader system is close to the maximum. The flow of the dynamic frame length algorithm is shown in Figure 5.
2.2 Experimental data analysis
Wood text uses the dynamic frame length ALOHA algorithm to prevent label data conflicts.Experimental data shows that when the number of tags reaches more than 85, the number of frame time slots of the ALOHA algorithm begins to increase sharply, which indicates that the number of tag collisions increases.
3 concluding remarks
Wood has implemented an embedded electronic tag reader system based on XScale processor. The RFID reader of the system encapsulates the underlying hardware driver, and the function module expands easily, and realizes the identification function of the electronic label. In order to avoid tag data conflicts, the system adopts the base-10 dynamic frame time slot ALOHA anti-collision algorithm, which reduces the probability of tag collisions in the RFID system and improves the identification efficiency and stability of the electronic tag system. Experimental results show that the system can quickly and accurately detect goods in the logistics system, suitable for use in harsh environments such as wet and dirty, and has good practical value.
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