基于MSP430控制的射频识别读写器设计_英文_(顾赟)

第28卷　第2期　吉首大学学报(自然科学版)V ol.28　N o.2 2007年3月Journal of Jishou University (Natural Science Edition )M ar.2007 Article I D :1007-2985(2007)02-0059-04Design of RFID R eader B ased on MCUMSP 430ΞGE NG Shu 2qin ,H OU Li 2gang ,G UO Y ue ,W ANG X iu 2ling ,W U Wu 2chen(V LSI and System Lab ,Beijing University of T echnology ,Beijing 100022,China )Abstract :Saving power is an im portant problem in portable device.This paper presents a S OC (System on a Chip )sys 2tem for radio frequency identification (RFI D )reader to sim plify the com plex traditional circuits.It puts the peripheral circuits into S OCand uses s oftware to execute the decoding ,checking ,identifying and real 2time calculating and display 2ing of digital signals.The proposed system has advantages such as sim ple structure ,low cost ,and low power consum p 2tion.K ey w ords :RFI D ;reader ;low power consum ptionC LC number :T N47 Document code :B1　I ntroductionRFI D is one of automatic technology to identify and collect object data quickly through RF digital signals.RFI D increases productivity and convenience.RFI D is used for hundreds ,if not thousands ,of applications such as preventing theft of autom obiles and merchandise ,gaining entrance to buildings ,automating parking [1],and s o on.The thoughts ofRFI D occurred on the heels of the development of radar.An early ,if not the first ,w ork exploring RFI D is the landmark paper by Harry Stockman ,“C ommunication by Means of Reflected P ower ”published in 1948[2].RFI D has advantages over bar code [3]:RFI D does not require line 2of 2sight access to read the tag ;the read range of RFI D is larger than that of a bar code reader ;readers can simultaneously communicate with multiple RFI D tags ;be 2cause of this capability ,a RFI D reader can capture the contents of an entire shipment as it is loaded into a warehouse or shipping container ;a reader collects detail in formation in one pass ,without having to scan each product ;tags can store m ore data than bar codes.Fig .1　B lock Diagram of a G eneral P assive RFI D SystemIn general ,RFI D system com prises a reader (or in 2terrogator ),its ass ociated antenna and the transponder (ortag )that carries data (see fig.1).Depending on theirs ource of electrical power ,there are active and passive tw ogeneral categ ories.Active RFI D tags contain an on 2b oardbattery.Passive tags obtain power from the signal of reader.This paper deals with the passive 2tag reader of 125kH z.The reader is usually controlled by micro controller of MCS51or arm.The former has high v oltage ,and much pow 2ΞR eceived d ate :2007-01-20Found ation item :The National Reform C ommittee of Development Next Internet Dem onstrative Subproject (C NGI -04-10-1D )Biography :GE NG Shu 2qin (1970-),female ,was born in Y uncheng City ,Shaanxi Province ,a doctor student in Beijing University of T echnology ;the major research areas are the field of system integration ,sens or and RFI D.er consum ption ,with many peripheral circuits in the control system of RFI D reader.It is not convenient to adjust the system and the area of PC B is big.The latter has high price ,and the control system is com plex.This paper presents a RFI D reader system based on MSP430,which puts much peripheral circuits into a chip.It uses s oftware to execute the decoding ,checking ,identifying and real 2time calculating and displaying of digital signals.The proposed system has ad 2vantages such as sim ple structure ,low cost ,and low power consum ption.2　Functions of System2.1The P assive 2T ag R eaderThe reader is com posed of RF.2M odule and micro controller (see fig.1).The reader transmits a low 2power radio signal through its antenna of RF.2M odule.When a tag comes within the reader ’s range ,it receives an electromagnetic signal from the reader through the tag ’s antenna.The tag then stores the energy from the signal ,a process called induc 2tive coupling [3].When the tag has built up enough charge ,it can power a back 2end integrated circuit (chip )of the tag ,which transmits a m odulated signal to the reader.That return signal contains the in formation stored in the tag.Once the RF.2M odule received the data it can be sent to amicro controller (or com puter )for processing and management.At the same time ,the processed data will be sent to LC D for display.2.2Communication B etw een R eader and T agBiot 2Savart laws establish the relationship between the current I 1flowing in an electrical circuit having length l and the intensity of the magnetic induction B as function of the distance x between the measurement P point (of unitvector z ,shown in fig.2)and the element dl producing the field according to the formula [4]:d B =μ0(I 1・d l )×e z 4πx 2.Fig .2　Magnetic Field Strength Fig .3　E lectric Equivalent Circuits for Magnetic(the Axis of the Coil )Coupling of R eader and T agz is the axis of the coil.The total intensity of the magnetic induction of reader antenna is :B z (d ,r )=μ0N 1I 1r 22(r 2+d 2)3/2.The electric equivalent circuit for MagneticC oupling of Reader and tag is depicted in fig.3.As the previous sec 2tion has shown ,this system w orks on the principle of Magnetic C oupling.The reader antenna res onant circuit is con 2structed by a capacitor C 1with an inductance L 1and the resistance R 1.The circuit of tag antenna is sim plified as L 2,R 2,with the capacitance C 2,and the data load R L [4].Where parameter I shows the current of antenna ;U 1is the s ource of ac signal v oltage ;U 2is the load v oltage.The subscript 1indicates the side of reader ;the subscript 2denotes the side of tag.The v oltage of reader antenna is U 1=ωL 1I 1=ω<1.When tag enters the field of reader ,such as P point ,the flux that g oes through tag antenna is <2=B Z S 2N 2.According to Faraday ’s Law ,if <2(t )=B Z S 2N 2=<2sin (ωt ),then u 20(t )=-d <2(t )/d t =ω<2cos (ωt ).Value of the coupling coefficient is M =k L 1L 2.The relation of signal v olt 206吉首大学学报(自然科学版)第28卷age between reader and tag antenna is :U 20/U 1=k L 2/L 1.3　System Architecture3.1R eader SystemFig .4　R eader System Frame of MSP 430F 435Reader system frame is consisted of RF.2M odule ,LC D ,keys ,MC UMSP430and power.Reader system frameof MSP430is shown as in fig. 4.This system uses low 2power consum ption MC UMSP430that is a system on chipas the controller.The v oltage is at 1.8～3.6V.3V ischosen by this system.The MSP430ultra low 2power archi 2tecture extends battery life.Current of RAM retention is0.1μA ;a real 2time clock m ode current is 0.8μA ;currentof active state is 250μA Π1MlPS.The clock system is de 2signed specifically for battery 2powered applications.A low 2frequency auxiliary clock (AC LK )is driven directly from a comm on 32kH z watch crystal.The AC LK can be used for a background real 2time clock self wake 2up function.This low 2frequency auxiliary clock makes stand 2by m ode ultra low 2power.An integrated high 2speed digitally controlled oscil 2lator (DC O )can s ource the master clock (MC LK )used by the CPU and high 2speed peripherals.By design ,the DC O is active and stable in less than 6μs.This high 2speed master clock achieves high performance signal processing.MSP4302based s olutions effectively use the high 2performance 162bit RISC CPU in very short bursts.MSP430has LC D controller ,which can directly drive LC D displays.It sim plifies the com plex circuits of traditional electrical LC D display system and s olves the additional error problems.It puts the peripheral circuits into S OC.This can reduce the area and power consum ption of PC B and minify the portable RFI D system.Fig.3shows RF.2M odule communicating with MC UMSP430.It can be seen that LC D m odule is linked with MSP430by I ΠO in fig. 3.LC D gets data from I ΠO of MC UMSP430and then displays them.When there is tag in the reader radio field ,RF.2M odule will receive signals.At the same time ,the interrupt will wake up CPU in less than 6μs.Then CPU processes data and LC D displays them.When CPU has operated the interrupt ,it will be set in the ultra low 2power stand 2by m ode by the s oftware.I f there is not tag for a long time ,LC D display is set to low power state.There are 20keys in this system ,which are linked with CPU.RF.2M odule and K eys are connected with the interrupt pins.I f there is no interrupt signals ,system are in low 2powerstate.The s oft frame is shown in fig.5and fig. 6.Fig .5　R eader System Softw are Frame Fig .6　Identification Subprogram of I nterruption3.2Communication B etw een RF .2Module and MCUThe communication between RF.2M odule and MC U is as in fig.7:There is one byte as the start data and one16第2期 耿淑琴,等:基于MSP430控制的射频识别读写器设计byte as the end data.The middle part is the ciphered data and longitudinal redundancy check (LRC )[5]data.RF.2M odule data and LRC data are sent together to the MC U.When their X OR result is zero ,the data is right.Then data are sent to LC D for display ,decoding and processing them.F or exam ple ,one tag I D number is 51E2066CE D.Their ci 2phered codes are 35H ,31H ,45H ,32H ,30H ,36H ,36H ,43H ,45H ,and 44H.Longitudinal redundancy checksum is (51H )X OR (E2H )X OR (06H )X OR (6CH )X OR (E DH ),and the checksum equals 34H.T ogether with the start bit 01,ciphered data ,checksum and stop bit 02,the total number is 01353145323036364345443402.I f MC U MSP430gets the data ,it must take out the ciphered data with the checksum data ,and execute the longitudinal redun 2dancy check.I f the checksum of MC U is zero ,it will decode the ciphered data.Identifying ,real 2time calculating and displaying of digital signals must be carried out.I f the checksum of MC U is not zero ,this means that there are s ome er 2rors in the data.Then MC UMSP430will ask the RF.2M odule to send the data again.start bit Ciphered data Checksum stop bitFig .7　Data Form B etw een RF .2Module and MCUFig .8　Data Timing I f MC U wants to get data correctly ,it must applywith the data timing as fig.8.Clock frequency must beset seriously ,and the time of instructors must be calculat 2ed correctly.Or else ,experiment data may be wrong.Itwill take a lot of time to adjust and do experiments.4　ExperimentsT able 1shows power consum ption of CPU and system at different state.When CPU is at stand 2by state ,current is the active state ’s 39.2%.P ower consum ption of the stand 2by state can be reduced to 61%of the active state.T able 1　CPU Pow er Consumption of 125kH z RFI D SystemCPU S tateCPU I ΠmA P ower C onsumption ΠmW Active0.0280.61600S tand 2by LP30.0110.02420S leeping 0.0100.000225　SummaryThis paper presents a RFI D reader system for 125kH z to sim plify the com plex circuits of traditional system and to s olve the additional error problems.It puts the peripheral circuits into S OC and uses s oftware to execute the decoding ,checking ,identifying and real 2time calculating and displaying of digital signals.The proposed system has advantages such as sim ple structure ,low cost ,and low power consum ption.This system is success fully used in 125kH z RFI D.R eferences :[1]　LANDT J.POTE NTI A LS.IEEE.History of RFI D [J ].P otentials ,IEEE ,2005,24(4):8-11.[2]　H ARRY ST OCK M AN.C ommunication by Means of Reflected P ower [J ].Proceeding of the I.R.E ,1948,36:1196-1204.[3]　RAO K V S.An Overview of Backscattered Radio Frequency Identification System (RFI D )[J ].IEEE Microwave C on ference ,AsiaPacific ,1999,3:746-749.[4]　DOMI NI QUE PARET.T ranslated by R oderick Riesco ,RFI D and C ontactless Smart Card Applications [M].England :John Wiley &S ons Ltd.,2005.[5]　C ORR P.A S tatistical Evaluation of Error Detection Cyclic C odes for Data T ransmission [J ].T ransactions on C ommunications Sys 2tems ,1964,49:211-216.(下转第74页)Teleportation of Tw o2P artite Arbitrary States Via G enuineFour2P artite E ntangled StatesK ONG Y ong2hong,W ANG X in2wen(Department of E lectronic Engineering and Physics,Hunan University of Science and Engineering,Y ongzhou425100,Hunan China)Abstract:A scheme for teleportation of tw o2partite arbitrary states via genuine four2partite entangled states is proposed. In the scheme,16orthog onal and com plete bases are constructed.All the bases are genuine four2partite entangled states,none of which is reducible.The scheme reveals s ome particular properties of the related four2partite entangled state,and indicates that in s ome sense the am ount of entanglement of tw o Bell states can be abstracted from any one of the four2partite states.K ey w ords:four2partite entangled states;tw o2partite arbitrary states;orthog onal and com plete bases;teleportation(责任编辑　陈炳权) (上接第62页)基于MSP430控制的射频识别读写器设计耿淑琴,侯立刚,郭　跃,王秀玲,吴武臣(北京工业大学集成电路与系统实验室,北京　100022)摘　要:设计了一种基于单片机处理器的射频识别(RFI D)便携式读写器的系统.采用当前先进的片上系统(System on Chip,S OC),将外围电路尽可能地放置于S OC芯片内,利用软件实现了对射频标签信号的数字实时采集和控制功能,从而简化了传统的微控制器控制的RFI D读写器所需的庞大硬件电路及其引入的额外误差,具有重要的实用价值,并且功耗和成本很低.关键词:射频识别;读写器;低功耗中图分类号:T N47文献标识码:B(责任编辑　陈炳权)。