Short distance wireless communication in the design of RFID system for automobile applications
source: 21IC time: 2012-05-15
The wireless identification system is digital communication principle, UHF transceiver based on single chip based on narrowband integrated. Describes the basic working principle and hardware design of the radio frequency identification system, and the flow chart of program design is given. Radio frequency identification label from the low power consumption, efficient recognition and practical angle design is suitable for vehicle. The test results show that, this system in complex road conditions (busy road) to realize the effective identification of 300m within the scope of conditions, line-of-sight conditions can reach 500 m range of effective recognition.
IOT refers to the various information sensing equipment, such as sensors, radio frequency identification (RFID) technology, global positioning system, infrared sensors, laser scanner, gas sensors, etc. various kinds of equipment and technology, object or process real-time acquisition of any monitoring, connection, interaction, collecting their sound, light, electricity, biological, position etc. all the required information, combined with a huge network formation and the internet. The aim is to achieve the objects and objects, objects and people, all the goods and network connection, easy identification, management and control. Research on key issues, this project according to the vehicle network in data acquisition, transmission and application, design of short distance wireless radio frequency communication technology of a new generation of vehicle radio frequency identification system based on. The system is composed of short distance wireless communication vehicle unit (On-Board Unit, OBU) and a base station system (Base Station System, BSS) consists of a point to multipoint wireless identification system (Wireless identification system, WIS), can be used in the base station coverage vehicle identification and intelligent range guidance.
1 system hardware design of
The hardware of the system mainly consists of a control part, RF part and external expansion of application components. With low power MCU as the control unit, the integrated single-chip narrowband UHF transceiver, optimized antenna. Using photovoltaic battery powered advanced, real reason of high integration of short distance wireless RFID terminal (OBU). The terminal has the advantages of small volume, low power consumption, suitable for a wide range of rejection, and set up and the open standard protocol interface, convenient and existing systems or other systems docking.
System schematic as shown in figure 1.
The 1.1 control circuit design of
The control unit uses the low power application of mature TI company's MSP430 series, the series is TI1996 years began to market a 16 ultra low-power mixed signal processor (Mired Signal Proessor), its practical application for the demand of many analog circuits, digital circuits and microprocessors are integrated in one chip, &ldquo monolithic ” solution. Work in the WIS system of OBU and BSS in the same principle, so the OBU part of the design, the control part of the principle of Figure 2 is shown in figure.
MSP430F2274 input voltage is 1.8 ~ 3.6V voltage. Run at 1 MHz clock condition, chip power consumption during 200 ~ 400μ about A, the lowest power consumption clock shutdown mode only 0.1μ A. Due to open the system runtime modules with different functions, the standby, run and dormant for 3 different working modes, effectively reducing the power consumption of the system.
The system uses two clock system; basic clock system and digital oscillator clock system (Digitally Controlled Oscillator, DCO), the use of an external crystal oscillator (32 768Hz). During reset, first started by DCOCLK MCU (Microprogrammed Control Unit microcontroller), to ensure that the program started in the correct position, ensure the crystal oscillator has enough vibration and stability time. Then the software can be provided with the appropriate amount of register control bits to determine the system clock frequency of the final. If the crystal oscillator malfunction in as MCU clock MCLK, DCO will start automatically, so as to ensure the normal operation of the system; if the program runs away, usable watchdog reset it. This design uses the on-chip peripheral module watchdog (WDT), A analog comparator, timer, timer A (Timer_A) B (Timer_B), serial USART, hardware multiplier, 10 / 12 ADC, SPI bus.