Research And Development Of Class-VXI-Bus Based On VIETS

Virtual instrument technology being more widely applied, automatic test system bus technology being more mature, and computer software and hardware platforms upgrading faster,all these make the instruments developing towards multi-function, high-precision, highly integrated. The instrument bus system based on computer bus technology provides a general development platform, and it is used for equipment testing tasks, which is highly integrated, modularized, distributed and so on. Virtual instrument software technology has changed the traditional concept of the design of equipment, and the software-based algorithms takes the place of the traditional complex hardware-based technique with the development of digital signal processing. Virtual instrument technology is introduced into the laboratory, and constructs the experiment system integrated by signal generating, data acquisition, analyzing and processing. This system could realize the user-defined instrument function, and it can realize not only the purpose that one system replaces a variety of equipment, but also the function that the traditional teaching equipment do not have, improving the teaching efficiency and quality.VIETS is Virtual Instrument Education Test System which is independently researched by Jilin University and used for the experimental teaching in colleges. The modularized design, the reconfigurable hardware and the low-cost user-defined bus provide the cost-effective experimental testing platform for the engineering colleges and universities. This paper based on the system's software and hardware platform researches the VXI bus and develops its corresponding functions.Constructing low-cost and high-efficiency VXI bus system is the driving force of this study, the starting point is to solve the shortages of VIETS, and the focus is to study the VXI bus transform technology and functional board instability. Using VIETS platform, with reference to its developmental experience, the specifications of VXI and VME bus, and USBTMC transfer protocol specification, the specification of class VXI bus is set down. The specification lists mechanism, bus systems and communications three aspects, and it provides the basis for the design and realization of the bus interface and bus transmission protocol. The transitional specification for studying the standard VXI bus focuses on VXI bus basic data transmission (DTB) function combined with VIETS single controller design features without limiting performance, which is the simplified specification of VXI bus features. Thus, the specification of class VXI bus and the VIETS platform are based on for studying the design and implementation of bus interface and transmission protocol.Bus interface focuses on the external VXI-bus controller and board bus interface and designs related modules depending on MCU and FPGA. The design contains host module, slave module, timing module and triggering module related to the bus specification, including subsidiary functional modules such as MCU signal conditioning, signal registers of the class VXI bus, the local overall clock module and so on. Design of special registers control makes the bus get full address addressability, and the multi-layer logic structure hardware is more conducive to system upgrading.During the study of the bus-transmission protocol, what are focused on are the design and implementation of the backplane bus-transmission protocol and the message-base transmission. Backplane transmission protocol is to study coordination and dependence on the design of the VME, VXI, and the transformation of control protocol, and to achieve the DTB transmission capabilities about D8, D16 and A16, including a single reading and writing operation, block reading and writing operations and only addressing operational capacity. Shaking hand methods with asynchronous communication solves the possible data loss problem between high and low speed devices. Message-base transmission protocol presents the design of the long and short transmission of information capability in detail, through adding accessing endpoint information function, which solves the issue of the system waiting until death. Briefly introduce the design and implementation about modularized instrument drivers, taking the triggering source control of oscilloscope as an example.Compare VIETS personal bus, VXI bus and class VXI bus on mechanical structure, bus system and communication protocol. The class-VXI-bus is transplanted into the oscilloscope board and the control board to complete the development of the class-VXI-bus. SignalTap technology could complete the transmission performance testing tasks between VIETS and the class-VXI-bus and gets utmost transmission capacity, about 15MBps~20MBps, of the class-VXI-bus based on VIETS. The current bus transmission rate of VIETS is 570kBps, while the speed of class-VXI-bus is only 140kBps~710kBps, proving VIETS is faster than class-VXI-bus on average. Therefore, registers, MCU performances and the control process need continually improving to elevate the VXI bus transmission capacity.To the problems of function boards in the process of experiments, the paper has given the corresponding solutions. For example, the problems about oscilloscope triggering instability and DC signals having no triggering have been solved by digital hysteretic comparator and soft triggering program in the paper, which is characterized by no hardware replacement. To issues of difficult correction about the oscilloscope mass production, this paper presents the hardware embedded calibration tables, which is characterized by using FPGA technology to make calibration curve polynomial algorithm hardware. To the issue on the system improvement, this paper supplies an additional frequency signal generator and improves the arbitrary ware emission control function. After 18 times, more than three hours of instrument's multi-operation at the same time is spent each time, finding that the improved VIETS no longer waits until death and the triggering is stability, so the equipment meets the design requirements.This paper is divided into seven chapters. Here are major elements:Chapter 1 introduction: Summary of virtual instrument technology, leading VIETS out. Analyze thesis research significance and determine the main research.Chapter 2 class-VXI-bus specification-setting: Defines the class-VXI-bus specification from three categories of mechanism, bus systems and communication protocols, referring to VIETS, VXI bus system and specifications.Chapter 3 the design and implementation of class-VXI-bus interface functions: Details the design and realization of external class-VXI-bus controller and the bus interface of equipment board after introduction of the total interface design.Chapter 4 design and implementation of class-VXI-bus transmission protocol: Details the design and realization of backplane bus and message-base transmission protocol and briefly explains the design and implementation of the modularized instrument drivers after introduction of the whole transmission protocol.Chapter 5 the comparative study and performance tests of instrument bus: Focuses on VIETS and class-VXI-bus's VME transmission performance measurement from mechanism, bus systems and communication protocols three aspects, compares VIETS, VXI and class-VXI-bus, and completes the test transmission utmost capacity.Chapter 6 improved design and implementation of modularized instruments: The digital hysteretic comparator solves the oscilloscope triggering instability problem and the soft triggering method solves the DC signals having no triggering. It puts forward correction methods and hardware data corrections design, designs and achieves frequency and arbitrary wave control modules, which gives improved equipment experimental results.Chapter 7 the summary of this paper: Sums up the results of studying the class-VXI-bus, and lists the recommendations about bus researching and system updating.Inheriting the reconfigurable design concept of VIETS, this paper introduces improving the performance of the user-defined bus systems, developing and maintaining 15 sets of education system, which work stably for a long time, and completing undergraduate education mission. The research of the class-VXI-bus specification and the design of related modules not only lays the foundation for further study, and makes VIETS user-defined instrument bus more standard, but also provides students with cost-effective learning platform.