Design Of Parallel Multi-channel Frequency Instrument Based On USB

Since frequency signal has advantages of strong anti-interference capability, high accuracy in electronic measurement, frequency tester is widely used. Due to large system with multi-channel, parallel, large-scale dynamic frequency signals measurement, it presents a design based on USB to parallel multi-channel frequency tester. The tester is mainly composed of several parts: CPU module with USB interface, counting module, signal conditioning modules, keyboard and display module, and its supporting software.Firstly, the paper presents the method of researching frequency measurement; secondly, it introduces the frequency tester hardware circuit design, CPU firmware development in details by sub-chapter and FPGA core measurement module design, finally, debugging is induced through combining hardware with software and experiment indicates frequency tester design is correct.The paper is mainly studying in serval aspects as followings:1. Considering the working principle of classical frequency measurement and frequency test cycle method's merits, it introduces frequency measurement method which can achieve parallel, multi-channel signals measurement. It has great advantages of wide range measurement, less occupation of hardware interrupted resources, easy to expand channels. It can meet transition process of frequency signals broad width change in the testing process.2. Based on the synthetic measurement methods, it presents a design based on USB parallel multi-channel frequency tester. The tester can realize programmable control instrument debugging and off-line control. The plant is strongly practical.3. This paper further proposes the parallel, multi-channel frequency tester's specific hardware design based on USB bus technology, including the CPU board hardware, the keyboard and display module circuit theory, signal conditioning circuit design. It makes frequency tester more intelligent and small.4. FPGA is used to shorten development time and improve integration. Using EDA technology, Verilog HDL as design language, FPGA as a carrier, frequency integrated application of principles of measurement methods; it realizes the core measuring module design and gives simulation waveform. It realizes larges range, dynamic frequency signal continuous measurement.5. USB controller's firmware program adopts C language under Keil uVision2 development environment. Controller design achieves two different working mode's setting, it's tested in different working conditions and different working frequency. The result proves the method is very effective.