Design And Realization Of Raster With USB Interface

Along with the development of USB (Universal Serial Bus), USB is used on many external devices because of the effective transmission and the convenience of USB device. USB has been a standard configuration on PC. If the transmission distance allows, USB is used widely because of its good characteristic.Grating is the main sensor in precision measure field. The raster introduced in this paper is based on grating sensor, designed to meet the user's demand at the present time, it has USB interface, and has many practicably factions for measuring length.The hardware of raster is made up of 89C51 as main processor, PDIUSBD12 as USB interface, grating signal-processing circuit, ispLSI1016 as counter and signal subdivision circuit, BC7281A as data display and keyboard control circuit, X25045 as watchdog circuit.The software of raster has two portions. The first portion is firmware, including USB interface control, displayer and keyboard control and watchdog etc; the second is USB driver, which is the channels between the firmware and PC application, in additional, test program is designed to test the cooperation between hardware and USB driver.This paper adopts a subdivision principle, in which interaction with hardware and software, in grating square wave signal subdivision: four subdivision and subdivision principle based on computer clock pulse. The subdivision principle based on computer clock pulse is improved, curve fitting method is used to estimate the width of signal wave, thus the raster can dynamic measure the signal cycle, and the subdivision precision is improved.The raster introduced in this paper adopts USB interface, it has good application foreground, the subdivision principle is practicably, and the raster has practical fuction, it i convenient for use.