Abstract
The reach paper mainly discussed the design process of multi-function cymometer that uses FPGA to count the frequency measurement and cymometer is also controlled by single chip computer. The cymometer makes use of equal-accuracy design that can overcome the disadvantage of traditional measuring principle, which precision declines as measured signal frequency does. The equal-accuracy measurement not only has higher measuring precision, but also can keep invariable measuring precision in whole area of frequency.
This cymometer uses FPGA to realize the measuring count of frequency、period、pulse width and occupy-empty ratio. Single chip computer completes the rest control、data processing and display output of the system.
This essay discusses the compose of hardware circuit and software control flow of single chip computer in detail. Hardware circuit includes key input module、display module、plastic module of input signal、single chip computer control module and FPGA main control module.
The cymometer adopts single chip computer AT89C51 of Atmel company and EPF10K20TC144-3 of Altera company. Key input module has 5 function key. Display module uses eight 74LS164 to realize the serial display of LED. First, the measuring signal amplitude is limited. Second, the signal is amplified by two class direct coupling amplifier. Finally, the signal inputs FPGA after it is trimmed by Smitter trigger. Standard frequency is 50MHz.
Key words: Cymometer; Frequency measurement; Equal-precision; Single chip computer; FPGA