【導(dǎo)讀】本論文主要是應(yīng)用AVR單片機(jī)進(jìn)行數(shù)據(jù)采集系統(tǒng)的設(shè)計(jì)，數(shù)據(jù)采集系統(tǒng)是將傳感器輸出的模擬信號進(jìn)行采集轉(zhuǎn)換成數(shù)字信號，然后送入計(jì)算機(jī)進(jìn)行處理，或進(jìn)行數(shù)據(jù)儲存和顯示，并按需要的形式輸出處理結(jié)果。隨著計(jì)算機(jī)技術(shù)和電子信息技術(shù)的高速發(fā)展，數(shù)據(jù)采集結(jié)合先進(jìn)的電子技術(shù)，已經(jīng)能利用軟件來處理大量測量數(shù)據(jù)。特別是嵌入系統(tǒng)的投入，高性能的單片的大量應(yīng)用，使采集系統(tǒng)更加智能化和綜合化。本設(shè)計(jì)采用AVR系列單片機(jī)的ATMEGA16單片機(jī)，AD620放大器，AD7853數(shù)模轉(zhuǎn)換器,6N137隔離芯片等芯片的連接來實(shí)現(xiàn)溫室的溫度,濕度,光度三路信號的采集。使用ATMEGA16實(shí)現(xiàn)其控制，采用ISP通信方式進(jìn)行數(shù)據(jù)傳輸。作為一個(gè)整體而言，數(shù)據(jù)采集系統(tǒng)的發(fā)展將受到多方面方面的影響。模擬輸入信號經(jīng)過模擬多路開關(guān)，程控放大器，進(jìn)入模擬數(shù)字轉(zhuǎn)換器轉(zhuǎn)換為計(jì)算機(jī)可以接受的數(shù)字信號，計(jì)算機(jī)對數(shù)字信號進(jìn)行存儲和處理，并對

　　

【正文】 lot and the port contradiction formulates, has declared a position since 1995 on Comdex widely has supported until now for each PC factory. Now produces PC has nearly all provided the USB connection, Microsft Windows98, NT as well as MacOS, Linux, FreeBSD and so on the popular operating system all increased to USB the support. USB the system constitution USB system mainly by the master control regulator (Host Controller), USB Hub and the USB peripheral (Peripherals Node) is posed the system topology, as shown in Figure 1. USB main merit 　　(1) speed of USB highspeed and lowspeed two ways, the main mode of highspeed mode, rate of 12 Mbps, and does not need to adapt to some very high throughput and realtime equipment, If the mouse, USB also provides lowspeed, rate of Mb / s. (2) equipment installation and configuration easy to install USB devices without reopen chassis, Modified installation of the equipment do not need to shut down the puter. All USB devices support hot pluggable, the system automatically on its configuration, discard the previous dialup jumper and switch installed.(3) easy to expand through the use of Hub Dialup can be extended up to 127 peripherals. Standard USB cable length of 3 m (5m lowspeed). Hub or through the repeater can enable peripherals reach 30 m distance. (4) to use USB bus power supply provides maximum voltage up to 5 V, 500mA current.(5) Use of a total of four USB flexible transmission mode : Transmission control (control), ATM (Synchronization) interruption of transmission (interrupt), the bulk transmission (bulk), to meet the needs of different2. uses the USB transmission the data acquisition equipment. hardware position　A practical USB data acquisition system including the A / D converters, microcontroller and USB munication interface. To expand its uses, can also add more analog switches and digital I / O ports. System of A / D and digital I / O is designed to be able to follow the traditional design methods, According to the acquisition accuracy rate, channel, as well as in several elements to choose a suitable chip, the design should give full attention to the antijamming performance, In particular, the A/D Acquisition especially. In microcontroller and the USB interface, there are two choices, A microcontroller is used with an ordinary USB dedicated munications chips. ASIC is now the more popular of National Semiconductor Corporation USB N9602, the SL11 ScanLogic other. The author has adopted the 89 panies Atmel microcontroller and USBN9602 decoder chip and system, achieved good results. This program design and debugging more trouble, the cost is relatively high. Another option is using USB munication with the MCU. With USB application of the increasingly widespread, Intel, SGS Tomson, Cypress, Philips, and other chip manufacturers have introduced a USB munication interface with the MCU. These microprocessing capability, and some have their own on multiple A / D, constitute a system of circuit is simple, convenient debugging. Electromagnetic patibility, and thus, using USB interface with the MCU constitute USB data acquisition system better solution. However, as with the USB interface, these chips past the development system is usually not patible, need to buy a new development system, the higher investment. software constitutionWindows98 providing a wide variety of USB device drivers, But it seems no one is specific data acquisition system, we must address specific equipment to prepare the driver. Although the system has a lot of standard interfaces function, However, it remains Driver USB development of a most difficult things, Windows DDK is usually used to achieve. There are many thirdparty software vendors to provide a variety of tools for generating, Compuware, as the driver works, Blue Waters, the Driver Wizard. They can easily within a few minutes of generating highquality USB driver. Equipment SCM Program for the same difficulties, but no one manufacturers to provide the automatic generation tool. Establishment of a stable, wellSCM process is directly related to equipment performance and must be given full attention. These two procedures are of concern to developers, users of much concern. Users concerned about how efficiently through the click of the mouse to operate the equipment and how to handle the collection and analysis of large amounts of data ing in, it also must have highquality software users. Software must be user friendly interface, powerful data analysis and processing capabilities and to provide users with redevelopment of the interface .3. realizes the USB longdistance range gathering data transmissionTransmission distance is limited USB application in the industrial scene of an obstacle, the increase in the relay or Hub, USB transmission distance is usually more than a dozen meters, which run on the industrial scene is obviously too short. Now there is a lot of industrial use RS485 transmission of data acquisition equipment. RS485 has its inherent advantages that its transmission distance can reach 1,200 meters, and a number of equipment can be articulated. Deficiencies lies in the slow speed of transmission, the use of bus, equipment mutual influence between the low reliability, Card needs the support the high cost of installing such trouble. RS485 of these shortings can be just as USB cover, USB and the transmission distance is limited precisely RS48539。s superiority lies. If it can integrate the two, plementary strengths, we will be able to produce a fast, reliable, lowcost remote data acquisition system. This system is the basic idea : the acquisition scene and sensor acquisition of the analog to digital, RS485 agreement will upload data. PC terminal in a twoway RS485USB conversion interfaces, use this interface to receive the data and 485 through the USB transmission to the PC for processing. And mainframe data sent equipment to the process is the opposite