| With the development of modern science and technology, radio frequency identification(RFID), as a branch of wireless communication technology, plays a decisive role in the fields of security system, traffic control, archives management, parking service, logistics and transportation, etc. Meanwhile, UHF RFID technology is moving beyond the LF and HF and becoming a hotspot of the current RFID technology. A complete RFID system usually consists of RFID tag, RFID reader and computer or other control unit.Based on this, the purpose of this thesis was to design a handheld UHF RFID reader which is in line with ISO 18000-6C standard. As a handheld portable embedded device, the selection of hardware and the design of software framework were the most important parts in the development process, so how to reduce the volume and power consumption while ensuring functionality and performance were always insisted on in this thesis.First, after the access to relevant historical development and theoretical foundation, and analyzation of the radio working principles of RFID theory, PR9200 chip produced by PHYCHIPS was chosen as the core chip with the consideration of the balance of performance and power consumption. This thesis also made a detailed analysis of peripheral RF circuit design, and designed a small-scale UHF band resonant quadrifilar spiral antenna. The antenna consisted of a feed network which contains a power devider and microstrip lines for power distribution and phase delay. Four feeding ports output equal power with phase descending 90 degrees and four inverted-F antenna arranged in a ring to form a left-handed helix quadrifilar helical structure.ST’s micro controller unit STM32F103RET6 was selected to be the main controller chip, and 8Mbit FLASH, font chip supporting GB18030 standard, Bluetooth module, monochrome OLED display module with 128×64 resolution to be the peripherals of the RFID reader. RT-Thread, as known as a domestic open source real-time operating system was ported on STM32 platform in order to achieve more extensions.According to the hierarchical thinking of RT-Thread, a proposal was made that the whole system was divided into four layers including hardware layer, driver layer, system layer and application layer. The driver layer contained UART, SPI, I2 C and other bus drivers and OLED displays, touch buttons, buzzer, FLASH, font chip and other device drivers; the application layer contained RTGUI graphical interface and threads working on cards reading, display, voltage and key monitoring. It is able to meet the performance and time requirement when dividing the tasks reasonably and executing in parallel correctly.The exprimental results showed the UHF RFID reader hardware running well, the driver working properly, the user programs scheduling and operating normally. The reader was able to read and write RFID tags in line with ISO 18000-6C standard, conveniently transmit tag data to a computer or cell phone for subsequent processing via Bluetooth or USB interface, and add functions by further user application development. In summary, the reader designed in this thesis archived the goal of low cost, small size and full functionality. |
