Design and Research of Virtual Instrument Development Board Lin Zhang 1, Taizhou Li 2, and Zhuo Chen 2 1 School of Mechanical and Engineering, Huazhong University of Science and Technology 2 School of Electronic Information, Wuhan University 776396043@qq.com Abstract. At present, the technology of virtual instrument has been developed very quickly in the field of electronic measurement and automatic control. The virtual instrument is a kind of functional instrument combining of software and hardware.this article is from the perspective of exploration and research, and as a reference when encounter hardware problems in the research and development of virtual instrument. Virtual Instrument Development board, based on LabVIEW development platform, can achieve virtual oscilloscope, virtual signal generator, virtual spectrum analyzer and so on. And the use of virtual reality on the oscilloscope signal testing and analysis, while the virtual signal generator's output signal also had a measured and analysis, the results are satisfactory, the virtual spectrum analyzer at the request of the software is relatively high, in this paper did not achieve this feature, but the hardware has been tested successfully. Keywords: Virtual Instrument Development board, DSP, FPGA(CPLD), SCM, LabVIEW,Quartus II. 1 The Conception of Virtual Instrument As traditional instruments, virtual instruments contain the same data acquisition and control, data analysis, which resulted in the expression of three function modules. Virtual instrument in a transparent way combines the computer resources and equipment hardware testing capabilities to achieve functional operation of the instrument. Virtual instrument with a variety of icons or controls simulates a variety of conventional devices on the virtual instrument panel. By kinds of icons to achieve instrument power switch-off; The button icons from a variety of test signals to set the "magnification", "channel" and parameters; A variety of display controls use values or waveforms to display measurement or analysis results; Using computer mouse and keyboards operation to simulate the traditional practice on the instrument panel; Using a flow chart of the graphical programming software to achieve a variety of signals measurement and data analysis. Electrical parameters based on virtual instrument by the tester hardware and software, most of the structure percent. Virtual instrument hardware usually consists of general-purpose computer and peripheral hardware devices. General-purpose computer can be a notebook computer, desktop computers or workstations. GPIB peripheral hardware devices can choose the S. Lin and X. Huang (Eds.): CSEE 2011, Part I, CCIS 214, pp. 231 238, 2011. Springer-Verlag Berlin Heidelberg 2011
232 L. Zhang, T. Li, and Z. Chen system, vxl system, PXI systems, data mining collection system or other systems, and you can also choose from two or more systems consisting of hybrid systems. One of the most simple and cheapest form of ISA or PCI bus based data acquisition card, or based on RS - 232 or USB bus portable data acquisition module. Virtual instrument software, including operating systems, instrument drivers and application software at three levels. Operating system can be WindowSgx/NT/2000/XP, SUN05, Linux and so on. Instrument driver software is the direct control made a variety of hardware interface drivers, and application software and peripheral equipment drive hardware modules to achieve a communication link. Functional applications include software programs to achieve equipment and implement virtual instrument panel. The user through the virtual surface Interact communicates with the virtual instrument panel. 2 The Choice of Virtual Instrument's Development Environment Currently, the test system used for virtual instrument development, and relatively mature software platform, there are two main categories: one category is common visualization software programming environment, and there are Microsoft's Visual C + + and Visual Basic, inprise company's Delphi and C + + Builder, etc.; the other is the introduction of a number of companies dedicated to the development of software programming virtual instruments Environment, mainly Agilent Company (former HP company, a separate company) Agilent graphical programming environment VEE, NI's Lab VIEW graphical programming environment, and text programming environment Lab Windows / CVI. Common visualization software VB, VC, Delphi, are based on the text of a certain graphical features of the programming language. They are just text language graphical environments Or as support visual environments, not the graphical languages. Development of virtual instrument application softwares based on these platforms, require a lot of text programming languages,therefore the difficulty was increased, difficult to upgrade, and the efficiency is not high. A dedicated virtual instrument software, instrument-oriented interactive C language development platform Lab Windows / CVI has programming simple and intuitive that they have to provide automatic code generation and a large number of standardized instruments meet VPP driver source code available for reference and use, etc., is a virtual instrument system integrators to use more of the software programming environment for the formation of large multi-based test systems or complex virtual instrument. Agilent VEE and Lab VIEW is a graphical programming environment or as G programming environment and programming language used is different from the text of the flowchart programming method, suitable for professionals formed small test systems and simple virtual instrument. 3 Design of Virtual Instrument Development Board 3.1 Design of MCU and PC- 3.1.1 RS232 Computer Interface with the PC Because PC-232 logic level is different from MCU interface level, so you need level conversion, PC machines only can communicate with the microcontroller.
Design and Research of Virtual Instrument Development Board 233 Fig. 1. MAX232 chip design for applications with PC computer interface 3.1.2 PS / 2 Interface 1: data line (DATA); Figure. 1 MCU and PC computer interface circuits Figure. 2 SP / 2 wins 0 figure cited 2: Not used: 3: Power ground (GND); 4: Power (+5 V); 5: Clock (CL K); 6: not used Now widely used PC, PS / 2 interface is miniodin6pin connector, and PS / 2 devices are the main from the points, female socket with the master device from the vice device using Male plug. Now widely used PS / 2 keyboard and mouse are working under the vice device. PS / 2 interface clock and data lines are open collector structure, must be an external pull-up resistor (generally Pull-up resistor to set the main device 1.Data communication between master and slave synchronous serial bidirectional transmission, the clock signal from the Generated from the device). Fig. 2. PS/2 pin 3.2 CPLD Application Circuit Design 3.2.1 CPLD Hardware Design Because many of the virtual instrument development equipment, instruments, need to work on high speed, so I use CPLD chip to achieve. One chip manufacturer, is used as
234 L. Zhang, T. Li, and Z. Chen the mainstream-altera CPLD, mainly due to the cost-effective feature of ALTER, and because the free build environment, the company's chips in many instruments devices have applications, such as with the 7000S series EPM7128SLC84-6 chip. This development board with CPLD is to achieve a special selection of waveform and high-speed transformation, meanwhile, CPLD and DSP-left interface, can achieve spectral analysis, high-speed oscilloscopes and other functions. Fig. 3. CPLD(EPM7128SLC84 15) 3.2.2 Design of CPLD Interface with AD As a result of CPLD interface with the AD, through the CPLD to achieve Data buffer and primary treatment, AD in 12 bit AD1674, AD1674 minimum conversion time l0us, Fig. 4. AD circuit
Design and Research of Virtual Instrument Development Board 235 can choose the less precision of speed 8-bit AD to make higher conversion. Then, higher in accuracy can be used 12-bit, general requirements for precision can be achieved in the virtual instrument development board. Consequently, this chip can complete the application needs, different requirements for the development of virtual instruments. 3.2.3 CPLD Interface Design and DA Fig. 5. DA circuit 3.2.4 JTAG Interface JTAG is the FPGA (CPLD) program download interface, using ByteBlasterMV parallel download cable, ByteBlasterMV parallel download cable has standard parallel port connector with the PC's 25-pin, support 3.3V Vcc voltage Or 5.OV,allowing PC users from the MAX + PLUS II or Quartus II development software to download the data. Fig. 6. JTAG Interface 3.3 Low Pass Filter Design Figure 7 for the 30MHz-pass filter design parameters and circuit diagram.
236 L. Zhang, T. Li, and Z. Chen Fig. 7. 30MHz low-pass filter 3.4 Single Chip Design Figure 8 is the minimum external circuit of single chip ATM89S52.the microcontroller bidirectional data bus as port PO which connected with the CPLD's 10.one-way read-write control output control bus including the Rd and Wr, address latch signal ALE (AddressLockEnable). 232 serial access microcontroller achieve Serial Port Communication, and Pl connect with DDS chip complete data transfer, register the command bus. The relationship of the DDS output frequency f0,the reference clock fr, the phase accumulator length N and the frequency control word FSW is: fo = fr.fsw/2n DDS frequency resolution is: AfO = fr/2n Because the maximum DDS output frequency by the Nyquist sampling theorem limit, so: fmax = fr / 2 [1 1] Currently, DDS products have Qualcomm's Q2334, Q2368; AD's AD7008, AD9850, AD9851, etc., This development board uses the company's AD9851 AD design. Meanwhile, SCM needs to do data type conversion. Fig. 8. Basic circuit microcontroller
Design and Research of Virtual Instrument Development Board 237 3.5 Reservation and DSP Interface Fig. 9. Interface with DSP 4 Verilog HDL Language Design Triangular Wave Generator 4.1 Keil C Compiler Environment Cx51 compiler and expansion of the 8051 traditional microprocessor optimized C compiler and library reference. Fig. 10. Keil C interface 4.2 Build Successful Window Fig. 11. Build successful window
238 L. Zhang, T. Li, and Z. Chen 5 The Test of Signal Generator Serial debugging assistantis an indispensable tool in the research of the microcontroller serial PC with SCM communication, and virtual instrument development board uses serial communication, so I applied to serial debugging assistant for testing the development board. Figure 12 for the test signal generator waveform. Fig. 12. signal generator waveform References [1] IEEE1451.2 A Smart Transducer Interface for Sensors and Actuators-Transducer to Microprocessor Communication Protocols and Transducer Electronic Data Sheet (TEDS) Formats. IEEE Standards Department [2] Andrade, H.A., Kovner, S.: Software synthesis from dataflow models for G and LabVIEW TM. In: IEEE (ed.) Proceedings of the IEEE Conference Record of the 32nd Asilomar Conference on Signals, Systems and Computers, vol. 2. IEEE, Pacific Grove (1998) [3] Goldberg, H.: What is Virtual Instrumentation? IEEE Instrumentation and Measurement Magazine 3(4) (2000)