基于虚拟仪器的信号发生器的设计与实现_翻译设计.doc

1、合肥学院题目：基于虚拟仪器的信号发生器的设计与实现Virtual Instruments Based on Reconfigurable LogicAbstract. A virtual instrument results from the combination of a general purpose computer with a generic data acquisition system in order to emulate a traditional measurement instrument. The data acquisition hardware of the vi

2、rtual instruments provides computers with input/output capability and is usually based on the integration of standard circuits with fixed architecture. Meanwhile the software defines the analysis and processing of the acquired data that is the function of the generated virtual instrument. As a conse

3、quence, the virtual instruments are characterized by their versatility and low cost but they lack of performance of the application oriented hardware architectures. In this paper, we present a virtual instrument system based on reconfigurable hardware that improves the features of virtual instrument

4、s preserving their versatility and low cost.1. IntroductionThe emergence of virtual instrumentation is a revolution in the history of the development of measuring instruments. It fully utilizes the latest computer technology to implement and extend the instrument function. Using the image of a compu

5、ter screen can be easily simulate a variety of equipment control panels to the needs expressed in the form of the output of test results. Using computer software to achieve most of the signal of the analysis and processing to complete a variety of control and test function. The user through the appl

6、ication of general-purpose computer program modules and features of the hardware together. Through friendly graphical interface to operate this computer. As in operating their own definition of individual instruments of their own design can be measured to complete the acquisition, analysis, determin

7、e, control, display, data storage and so on.Virtual Instruments advantages of more traditional instruments: (1)A strong integration of computer hardware resources. Breaking the traditional instruments in data processing, display, storage and other limitations, and greatly enhanced the capabilities o

8、f traditional instruments. (2)The use of computer software resources to achieve some part of the software of instrument hardware, saving material resources, increase system flexibility. Through software technology and the corresponding numerical algorithm. Directly on the test data for various analy

9、sis and processing in time. Through the graphical user interface technology, truly user-friendly, human-computer interaction. (3)Hardware and software of virtual instrument is an open, modular, reusable and interchangeability characteristics. Therefore, the user can according to their own needs and

10、use different manufacturers products. The development of the instrument system is more flexible, efficient and shorten the formation time of the systemThe traditional instruments are application specific systems based on fixed hardware and software resources so their function and applications are de

11、fined by the manufacturer. These instruments are complex systems and therefore they become expensive and difficult to manage.The widespread usage of personal computers in many scientific and technological fields make them an ideal hardware and software platform for the implementation of measurement

12、instruments. By adding a simple data acquisition system, a personal computer can emulate any instrument. The instruments generated in this way are called virtual instruments because they do not have exclusive access to hardware and software resources. Different instruments can be implemented over th

13、e same hardware by only reprogramming the software. The virtual instruments offer plenty of advantages the most important of which is the low cost due to the reusability of hardware and software resources. The above characteristics and the continuous evolution and cheapening of the personal computer

14、s make the virtual instruments a valuable alternative to traditional ones.Nevertheless, there are two main factors which limits the application of virtual instruments. By one hand, the data capture is reduce to slow rates because of the more common operating systems of the general purpose computers

15、are not oriented to realtime applications. By other hand, the data acquisition system is not an application oriented system but a generic one. Therefore, our proposal is focused on the enhancement of virtual instruments by the replacement of the generic hardware with a reconfigurable data acquisitio

16、n system, as it is shown in Figure 1. By this way, some data process can be implemented by hardware reducing the data flow to/from the computer and rising the maximum sample rate.The benefits of virtual instruments based on reconfigurable logic are the following:-The bandwidth of the instruments can

17、 be increased implementing the more time critical algorithms by hardware.-The input/output capacity can be reconfigured according to the application. In special, FPGAs devices are characterized by a great number of input/output pins providing virtual instrument with the capacity to observe and contr

18、ol a wide number of signals.-The computer interface can be reconfigured according to the available resources (Plug&Play peripherals).-Different instruments can share software and hardware design modules increasing their reusability.2. The composition and classification of virtual instruments Virtual

19、 instrument system mainly consists of computers, hardware board,software and accessories. Users can request the flexibility to build their own testing equipment.The core of virtual instrument is software, which is mainly provided by the hardware driver, application programming software etc. It can c

20、omplete all the test requirements. The current development environment mainly into two categories:(1) text language; (2) graphics language. As the graphic language developed by convenience welcomed by the majority of engineers. There are not many trained in computer language engineers able to master

21、 the development of virtual instrument technology and applied to engineering practice in a relatively short period of time. Virtual instrument is essentially an open structure which to provide signal processing, storage and display functions by general-purpose computer, digital signal processors, or

22、 other CPU. To achieve instrument functions from data acquisition boards, GP IB or VXI bus interface board for signal acquisition and control. According to its different ways of using the bus can be divided into the following types: (1) PC Bus - plug-in card-based virtual instrument(2) parallel port

23、 virtual instruments (3) the way of GB IB bus virtual machines (4) VXI bus mode Virtual Instrument (5) PXI bus mode virtual instruments3. Reconfigurable Data Acquisitions SystemsWe propose the implementation of a reconfigurable data acquisition system using FPGAs. This system operates like a reconfi

24、gurable coprocessor oriented to the capture, generation and analysis of digital signals. The combination of this hardware with a general purpose computer results in a reconfigurable virtual instrumentation system where the end user determines the software and hardware resources required for each par

25、ticular application.3.1 General DescriptionThe more essential blocks of a data acquisition system are represented in Figure 2. As an application oriented system, most of these modules must be scalable (increasing or decreasing the number of input/output pins) according to different applications. For

26、 example, the capacity of the acquisition memory varies with the requirements of the instrument.At the same time, if the device provides with enough resources, several instruments can be active simultaneously. In this case, some blocks of the structure shown in Figure 2 must be multiplied accordingl

27、y while others can be shared among instruments. For example, an unique computer interface block multiplexed in time is generally more efficient because less input/output pins are dedicated to the communication tasks.In the computer side, the software is dedicated to the storage and visualization of

28、data, and also to the configuration and control of the hardware. The first tasks are implemented at application level and take advantage of multitask operating systems and their advanced graphic interfaces. The second tasks are mainly implemented as extensions of the operative systems and in this wa

29、y they are closely linked to the hardware.The blocks represented in Figure 2 are briefly described in the next sections. Also, the characteristics of the configurable devices (SRAM FPGAs) required for the implementation of these blocks are indicated.3.2 Input/Output ModulesThe input/outputs modules

30、conform the interface with the real world. The input/output blocks of the reconfigurable device must be bidirectional, with tri-state capability and internal registers for faster capture rates.3.3 Acquisition Control BlockThe data capture is usually synchronized with some external or internal events

31、 and this task is developed by the acquisition control module. As a consequence, the routing of this control signals to the input/output blocks and to the internal logic becomes very important. An architecture with several low skew and great fan-out distribution networks is mandatory for this purpos

32、es.At the same time, several inputs and outputs usually share common control signal so a device with a peripheral bus carrying control signals is suitable for this application.3.4 Timing BlocksThe timing blocks (oscilator, timers and counters) provides internal control signals to the data acquisitio

33、n system. Special attention was dedicated to the design of counters in order to reach maximum operating frequencies.3.5 Memory BlocksThe memory blocks operate as a temporary storage of the acquired/generated data. This memory blocks isolate the data acquisition process from the transference through

34、the computer interface. Therefore these storage devices are implemented as dual-port FIFOs with different clocks for push/pop operations.The memory blocks can be implemented like internal or external units to the FPGA. The first case is more desirable because the design offers best performance, cons

35、umes less power and is less error prone. Therefore, the FPGAs with embedded dual port memory blocks are more suitable for these purposes.3.6 Data Processing UnitThe data processing unit performs a real-time pre-processing of the acquired data. This unit implements the more critical algorithms that d

36、etermine the data throughput while the others can relay over software control (in the computer side). An exhaustive analysis of which algorithms must be implemented in hardware and which must be implemented in software was made for each different instrument. For example in a logic analyzer, the dete

37、ction logic of the trigger patterns must be implemented in hardware for better performance meanwhile the data conversion formats of data (assembling, disassembling) can be done in the computer.3.7 Computer InterfaceThere are two different options for the interconnection of the reconfigurable data ac

38、quisition board with the computer, one using of a direct expansion/local bus connection and the other using of a serial/parallel communications interface. In the first case, instruments with a great data throughput can be obtained but this kind of interface consumes many resources of the FPGA (logic

39、 and input/output pins) and limits the physical distance between the interconnected systems. On the opposite side, serial/parallel communications interfaces limit the binary rate of the transference but consume less logical and input/output resources and permit the physical isolation between devices

40、. This last characteristic is important for the implementation of portable instrumentation and also isolate the acquisition hardware from the noisy environment of general purpose computers. By this reason, the developed system actually implements the standard IEEE-488 (ECP mode) as the communication

41、 interface with the computer.4. ConclusionsSeveral prototype boards using Xilinx (XC400E) and Altera (FLEX10K) were developed for the implementation of a virtual logic (state and timing) analyzer. A performance of more than five was obtained over virtual instruments implemented using a commercial da

42、ta acquisition board.1、The generation background of virtual instrumentTodaywearein ahighly developedinformation society, which require a limited time and space to achieve a largeamount of informationexchange, inevitably bring aboutthe rapidincrease ofinformation density，required the electronic syste

43、ms have a faster speed and more powerful function for information processing. On the one hand the development of electronic technologyand marketrequirements objectively make the testinstrument develop tothe direction ofautomation andflexible, On the other hand, the electronic technology andmarket de

44、velopmentalsomake virtual instrument possible. In this situation, the virtual instruments based on micro-computer gradually become a reality, its appearance and extensively use provide an excellent model for the design of test system and allows engineers more powerful and flexible in measure and con

45、trol.2、The concept ofvirtual instrumentVirtual Instruments (Virtual Instrument, referred to as VI) concept is first proposed by the National Instruments (NI) in 1980s . The virtual instrument is a kind of Computer equipment system which based on the general purpose computer as the core hardware plat

46、form, defined by the user with a virtual front panel, the test function is performed by a computer testing software. The core idea is to use a powerful computer resources that would otherwise require hardware to software of the technology in order to minimize system cost, enhance system functionalit

47、y and flexibility. The virtual instrument represents the fundamental changes from traditional hardware-based test system to Software-centric test system. The emergence of virtual instrument is a revolution in the history of instruments, it represents the latest development direction and trend of ins

48、trument, produced an immeasurable influence on the development of science and technology and industrial production progress. Virtual instrument have many advantages, such as high performance, scalability, strong, development time is short and seamless integration.3、graphicalvirtual instrument develo

49、pment platform-LABVIEW introduction and its advantages LABVIEW is short for Laboratory Virtual Instrument Engineering Workbench, it is a powerful and flexible instrumentation and analysis of application development tool created by National Instruments (National instruments, IN) 。Labview is a graphical programming language, mainly used to develop data acquisition, instrument control and data processing and analysis software. Currently, the development of s