【正文】 began to replace vacuum tubes. This change presented a formidable challenge to the engineers of the day. They had to forget what they knew about circuits and start again. It can only be said that they measured up superbly well to the challenge and that the change could not have gone more smoothly. Soon it was found possible to put more than one transistor on the same bit of silicon, and this was the beginning of integrated circuits. As time went on, a sufficient level of integration was reached for one chip to acmodate enough transistors for a small number of gates or flip flops. This led to a range of chips known as the 7400 series. The gates and flip flops were independent of one another and each had its own pins. They could be connected by offchip wiring to make a puter or anything else.These chips made a new kind of puter possible. It was called a miniputer. It was something less that a mainframe, but still very powerful, and much more affordable. Instead of having one expensive mainframe for the whole organisation, a business or a university was able to have a miniputer for each major department.Before long miniputers began to spread and bee more powerful. The world was hungry for puting power and it had been very frustrating for industry not to be able to supply it on the scale required and at a reasonable cost. Miniputers transformed the situation.The fall in the cost of puting did not start with the miniputer。 although it is not obvious, on the surface, a modern x86 processor chip contains hidden within it a RISCstyle processor with its own internal RISC coding. The ining x86 code is, after suitable massaging, converted into this internal code and handed over to the RISC processor where the critical execution is performed. In this summing up of the RISC movement, I rely heavily on the latest edition of Hennessy and Patterson’s books on puter design as my supporting authority。這樣在轉(zhuǎn)換期間可以允許單總線上進(jìn)行其他數(shù)據(jù)往來。當(dāng)此口變?yōu)榈碗娖綍r(shí)就停止計(jì)時(shí)并讀出定時(shí)器的值，此值就為此次測(cè)距的時(shí)間，再根據(jù)溫度和超聲波傳播速度即可算出障礙物的距離。附件二：蘇州大學(xué)本科生畢業(yè)設(shè)計(jì)（論文）中期進(jìn)展情況檢查表學(xué)院（部）：電子信息學(xué)院 學(xué)生姓名吳紅亮年級(jí)08專業(yè)電子信息工程填表日期設(shè)計(jì)（論文）題目超聲波測(cè)距儀已完成的任務(wù)1. 根據(jù)需要實(shí)現(xiàn)的功能設(shè)計(jì)電路圖；2. 焊接電路板，并對(duì)各個(gè)模塊進(jìn)行硬件調(diào)試。 設(shè)計(jì)（論文）的主要內(nèi)容(1) 設(shè)計(jì)制作超聲波發(fā)射和接收電路。在這次畢業(yè)設(shè)計(jì)的過程中，周老師給我了很大的幫助，首先要對(duì)他表示感謝。可以選擇加驅(qū)動(dòng)芯片，也可以考慮用三極管驅(qū)動(dòng)。主要完成的設(shè)計(jì)有：，此模塊已將發(fā)射電路和接收電路集成好了，使用時(shí)只要在控制端Trig發(fā)大于10us寬度的高電平，就可以在接收端Echo等待高電平輸出。 //讀取溫度寄存器(共可讀9個(gè)寄存器)前兩個(gè)是溫度a=ReadOneChar()。unsigned char b=0。DQ = 1。}return(dat)。DQ = 1。 //單片機(jī)將DQ拉低delay(250)。而每次命令和數(shù)據(jù)的傳輸都是從主機(jī)主動(dòng)啟動(dòng)寫時(shí)序開始，如果要去單總線器件回送數(shù)據(jù)，在進(jìn)行寫命令后，主機(jī)需啟動(dòng)讀時(shí)序完成數(shù)據(jù)接收。單片機(jī)一旦檢測(cè)到有輸出就打開定時(shí)器開始計(jì)時(shí)。每個(gè)I/O口驅(qū)動(dòng)能力均可到20mA，整個(gè)芯片最大不得超過55mA；l ISP(在系統(tǒng)可編程)/IAP（在應(yīng)用可編程），無需專用編程器，可通過串口（）直接下載用戶程序；l EEPROM功能；l 看門狗；l 內(nèi)部集成MAX810專用復(fù)位電路(外部晶體為20MHz時(shí)，可省略外部復(fù)位電路)；l 時(shí)鐘源：外部高精度晶體/時(shí)鐘，內(nèi)部R/C振蕩器。缺點(diǎn)是穩(wěn)定度不高，占用CPU較多時(shí)間。七段數(shù)碼管的顯示方法可分為靜態(tài)顯示和動(dòng)態(tài)顯示：（1）靜態(tài)顯示靜態(tài)顯示就是顯示驅(qū)動(dòng)電路具有輸出鎖存功能，單片機(jī)將所要顯示的數(shù)據(jù)送出后，數(shù)碼管始終顯示該數(shù)據(jù)，處理器不在控制。計(jì)數(shù)器1對(duì)低溫度系數(shù)晶振產(chǎn)生的脈沖信號(hào)進(jìn)行減法計(jì)數(shù)，當(dāng)計(jì)數(shù)器1的預(yù)置值減到0時(shí)，溫度寄存器的值將加1，計(jì)數(shù)器1的預(yù)置將重新被裝入，計(jì)數(shù)器1重新開始對(duì)低溫度系數(shù)晶振產(chǎn)生的脈沖信號(hào)進(jìn)行計(jì)數(shù)，如此循環(huán)直到計(jì)數(shù)器2計(jì)數(shù)到0時(shí)，停止溫度寄存器值的累加，此時(shí)溫度寄存器中的數(shù)值即為所測(cè)溫度。放大后的交流信號(hào)送入比較器后輸出一個(gè)方波信號(hào)，并使觸發(fā)器觸發(fā)，向CPU發(fā)出中斷請(qǐng)求。l 高精度：可達(dá)3mm。因?yàn)轱@示只需要將距離顯示出來就可以了，所以顯示部分選擇了四只共陽數(shù)碼管。(2) 設(shè)計(jì)制作單片機(jī)系統(tǒng)，帶有數(shù)碼管顯示電路。因此，研制開發(fā)一種穩(wěn)定性好、靈敏度高、具有一定精度，且使用簡(jiǎn)單、成本低廉、易于大批量生產(chǎn)的超聲波測(cè)距儀對(duì)于滿足現(xiàn)階段的大量需求和未來這一領(lǐng)域的研究都具有重要的現(xiàn)實(shí)意義。第四章，本設(shè)計(jì)的軟件部分，包括系統(tǒng)軟件的設(shè)計(jì)流程圖、DS18B20驅(qū)動(dòng)模塊、數(shù)碼管顯示和聲速的計(jì)算。 DS18B20.前言實(shí)際生產(chǎn)生活中，人們往往需要對(duì)物體間的距離進(jìn)行精確測(cè)量。超聲波測(cè)距主要應(yīng)用于倒車提醒、建筑工地、工業(yè)現(xiàn)場(chǎng)等的距離測(cè)量。本設(shè)計(jì)利用超聲波傳感器HCSR04發(fā)射超聲波并接收回波的方式統(tǒng)計(jì)超聲波傳輸?shù)臅r(shí)間，采用STC89C51單片機(jī)作為控制核心，結(jié)合溫度傳感器DS18B20采集的溫度信息將聲速做相應(yīng)的補(bǔ)償，并計(jì)算出距離，最后通過4位數(shù)碼管將所測(cè)距離信息顯示出來。超聲波傳感器中的發(fā)射電路模塊發(fā)出超聲波，遇到障礙物返回，并被接收電路模塊接收到，單片機(jī)統(tǒng)計(jì)出聲波傳輸所用時(shí)間，結(jié)合溫度傳感器所測(cè)溫度，計(jì)算出實(shí)時(shí)的聲速并得到正確的待測(cè)距離。而且超聲波傳播速度在很大范圍內(nèi)與頻率無關(guān)。近十年來，國內(nèi)外科研人員在超聲波回波信號(hào)處理方法、新型超聲波換能器研發(fā)、超聲波發(fā)射脈沖選取等方面進(jìn)行了大量理論分析和研究，并針對(duì)超聲測(cè)距的常見影響因素提出了溫度補(bǔ)償，接收回來串入自動(dòng)增益調(diào)節(jié)環(huán)節(jié)等提高超聲波測(cè)距精度的措施。超聲波傳感器HCSR04中集成的發(fā)射電路模塊發(fā)出超聲波，遇到障礙物返回，最后被接收電路模塊接收，STC89C51單片機(jī)統(tǒng)計(jì)出聲波傳輸所用時(shí)間，結(jié)合溫度傳感器DS18B20所測(cè)溫度，計(jì)算出實(shí)時(shí)的聲速并得到正確的待測(cè)距離。 HCSR04實(shí)物圖 HCSR04超聲波模塊實(shí)物圖 HCSR04的主要技術(shù)參數(shù)l 所用工作電壓：直流5V電壓。v是超聲波在空氣中傳播的速度。用于讀寫和溫度轉(zhuǎn)換的電源可以從數(shù)據(jù)線本身獲得，無需外部電源?？刂葡鄳?yīng)的二極管導(dǎo)通，就能顯示出各種字符，其控制簡(jiǎn)單，使用非常方便。缺點(diǎn)是由于數(shù)碼管始終發(fā)光，功耗比較大。它的的最小系統(tǒng)由時(shí)鐘電路、復(fù)位電路、電源電路及單片機(jī)構(gòu)成。精度要求不高時(shí)，可選擇使用內(nèi)部時(shí)鐘，因?yàn)橛袉柶?，可以選擇4MHz~8MHz；l 有2個(gè)16位定時(shí)器/計(jì)數(shù)器；l 有2個(gè)外部中斷；中斷觸發(fā)方式為下降沿觸發(fā)和低電平觸發(fā)，Power Down模式可由外部中斷低電平觸發(fā)中斷方式喚醒；l PWM（4路）/PCA（可編程計(jì)數(shù)器陣列），也可用來再實(shí)現(xiàn)4個(gè)定時(shí)器或4個(gè)外部中斷（上升沿中斷/下降沿中斷均可支持）；l STC8951具有ADC功能。 超聲波時(shí)序圖開始給Trig端20us的高電平進(jìn)行觸發(fā)Echo是高電平嗎？開始計(jì)時(shí)YNEcho是低電平嗎？NY停止計(jì)時(shí)，計(jì)算出傳播時(shí)間 傳播時(shí)間獲取流程圖 DS18B20對(duì)溫度的補(bǔ)償由于DS18B20采用的是1－Wire總線協(xié)議方式，即在一根數(shù)據(jù)線實(shí)現(xiàn)數(shù)據(jù)的雙向傳輸，而對(duì)本次設(shè)計(jì)所使用的單片機(jī)來說，硬件上并不支持單總線協(xié)議，因此必須采用軟件的方法來模擬單總線的協(xié)議時(shí)序來完成對(duì)DS18B20的訪問。 初始化時(shí)序圖。uchar dat=0。_nop_()。 i8。當(dāng)聲波受到尺寸大于其波長(zhǎng)的目標(biāo)物體阻擋時(shí)就會(huì)發(fā)生反射，反射波稱為回波。WriteOneChar(0xCC)。t=8。4. 顯示部分采用4只共陽數(shù)碼管，通過74LS47譯碼器，將距離信息實(shí)時(shí)顯示出來。這次設(shè)計(jì)沒有考慮到這些誤差和影響，以后應(yīng)該改進(jìn)，使超聲波測(cè)距儀的測(cè)距更精確。在老師的指導(dǎo)幫助與嚴(yán)格要求下，我獨(dú)立地查閱資料、設(shè)計(jì)電路、編寫程序，極大地提高了我的實(shí)踐能力。設(shè)計(jì)（論文）的基本要求(1)在查閱文獻(xiàn)資料的基礎(chǔ)上，提出設(shè)計(jì)方案。本設(shè)計(jì)采用超聲波傳感器模塊HCSR04和STC89C51單片機(jī)來實(shí)現(xiàn)測(cè)距。為了減小I/O口開銷，通過配置共陽數(shù)碼管譯碼器74LS47實(shí)現(xiàn)數(shù)碼管的動(dòng)態(tài)顯示。在設(shè)計(jì)過程中的大部分問題我都通過閱讀參考的文獻(xiàn)解決了。A cyclist sets out on a circular cycling tour. Derive an equation giving the direction of the wind at any time. The singlechip puter At each shrinkage the number of chips was reduced and there were fewer wires going from one chip to another. This led to an additional increment in overall speed, since the transmission of signals from one chip to another takes a long time. Eventually, shrinkage proceeded to the point at which the whole processor except for the caches could be put on one chip. This enabled a workstation to be built that outperformed the fastest miniputer of the day, and the result was to kill the miniputer stone dead. As we all know, this had severe consequences for the puter industry and for the people working in it. From the above time the high density CMOS silicon chip was Cock of the Roost. Shrinkage went on until millions of transistors could be put on a single chip and the speed went up in proportion. Processor designers began to experiment with new architectural