Multi-Channels Data Acquisition Equipment Based On USB

The main job of this thesis is to design a high accuracyportable examination instrument of vibration signals.Examination instrument is composed of threesections:the first part, high accuracy vibration signal'sexamination circuits for sampling and adjustment;the secondpart, USB host partition for transference and storage; thethird part, the visual screen playing the vibration signalswhich is programmed in the Visual C++ language at the PCterminal.The usage of signal examination circuits for highaccurate vibration collection and adjustment is as thefollowing.We improve the high frequency vibration sensorsto monitor the input signals,and its type is CA-YZ-123C(A)-100,that means it's a water density three stalksvibration sensor. We use this sensor just because it isdesigned for military usage and there are signal modulatorsinside . The sensor has the advantages of high sensitivity,small temperature excursion,stable zero output and widefrequency band,etc.The vibration sensitive component is asilicon quantity hunch which is supported by silicon framewith several beams.When the silicon frame is suffered by thevibrate pressure, the beams'resistor value is changedsince the dint's function of inertia. And then the changeis turned to voltage value and put out by the electricbridges'conversion. The sensor can quantitatively measurevibration information of oscillating objects from X stalk,Y stalk and Z stalk.Three exportations of the electric bridges are reachedto 12 bits analogue/digital converter -ADS7864 eachother.ADS7864 can proceed analogue/ digital conversionunder the control of Microcomputer AT89C52. For the purposeof using the system in various conditions, we add anadjustment circuit of sampling signals between sensors andanalogue/digital converters,which is controlled bysimulation switch-CC4051.If we connect CC4051 withdifferent feedback resistors, then the input voltageranges of sampling signal can be turned from-2.5V～+2.5 Vto -5 V～+5V and -10 V～+10V,this method improves the usingscopes of the equipment.At the same time, there link three8253 counters in the signal sampling part ,which can examinewhether the car's output pulse is meeting with thepractical requestion.In order to locate the systems'sfunctions at the beginning of the operation, we build akeyboard with 8*8 keys ( which is under the control of aserial interface chip zlg7289)and a show screen ofLCD(240*64). USB host part.We adopt the USB host/equipmentcontroller SL811HS that is produced by Cypress company torealize the data transference and then store the largequantity of real time data to the Usb disk.In this part,author has designed a lot of programs to realize thecommunication process by making the abstract principle toa specific procedure in C language. In the USB host,we mustwrite programs with the following criterions:1)USB 1.1criterion;2)Mass Storage Class criterion;3)Bulk-Onlytransmission protocol;4)FAT16 file system criterion.Thefirst three criterions are the basement of USB HOSTcommunication,and the last one is requested by the Usbstorage device. Usb storage device requests the file storedin it is stored with the pattern of FAT16 criterion.In orderthat the host can read and write the file correctly to theUsb disk,we must make the criterion programmed. By the waythe author has added the mistake examination, rectify andthe mistake manifestation etc. to the communication process,to make the whole transmission process stable anddependable.Since the SL811HS host/equipment controller isjust an USB host interface chip and there is no microcomputerinside.So we must add a microcomputer at the peripheralcircuits as its process controlling. In the considerationof capacity of ROM and the speed of RAM, we adopt themicrocomputer-AT89C52 of ATMEL company to realize the datahandling and controlling. The two microcomputers,one insignal sampling circuits and the other in USB host part,areconnected by the FIFO-IDT7130 which is equal to SRAM for thedata transmission.The capacity of the FIFO is 1K Bytes,thetransmission process is:when the ADC has finished itsconversion,it transfers its data to the first microcomputerthrough the IO port.Then the MCU delivers the data to theFIFO with the pins A0L~A7L.After the data count to 1K Bytes(from 000H to 3FEH),the channels on the FIFO right way openand send the data to the second MCU.Since the MCU 2 isconnected with both USB interface and storage device,so wecan make the data transfer from the MCU's RAM to the Usbdisk directly.Till now,the transmission of data iscompleted.The majority of the whole development is theexploitation of USB host,and the center of USB host iswriting programs of communication's process.In thedebugging course,there are many questions we can not findany advice.For example,when the Usb disk is responsing tothe WHITE instruction of USB host,we must transmit 8times ,since every time we only can send 64 bytes and thewhole duty is 512 bytes.And after the transmission thedevice must return CSW packet to the host.But in thedebugging course,it took place that when the 7th transferencehas finished,the host no longer sends the 8th datasegment.And at that time if the device sends a CSW packetto the Host,the Host will send the last framecontinuously.This phenomena is not identical with theprotocol.But the problem is not serious and may be solvedwith the following method:in all the process of datatransmission,if only the last frame has not beendelivered ,the device sends the CSW packet to the Host,andthen the device may receive the last frame of data.By wayof testing,we can be convinced of that method. The third part is the vibration signal showing part.Aswe have realized the development of USB host, and have stored...