【正文】 數(shù)碼管顯示子程序框圖 鍵盤子程序設(shè)計(jì)本設(shè)計(jì)采用獨(dú)立鍵盤，三個(gè)鍵盤裝在P2口，單片機(jī)不斷的檢測P2口并將P2口與0x07相與，若最終所得的值不等于0x07，則有鍵被按下。判斷出被按下的鍵，不同的鍵執(zhí)行不同的功能，K1按下時(shí)整個(gè)模塊停止工作，這時(shí)按下K2或K3可以分別加減最小的報(bào)警距離，提醒汽車駕駛員停止倒車，當(dāng)設(shè)置完成后，再次按下K1鍵模塊重新開始工作。定時(shí)器0的高八位和低八位分別被賦予0，當(dāng)定時(shí)器計(jì)時(shí)完成后，就可以根據(jù)16位定時(shí)器的值得到超聲波所經(jīng)過的時(shí)間，利用標(biāo)志位flag_time0計(jì)算定時(shí)時(shí)間，flag_time0=TH0*256+TL0,可以計(jì)算出高電平持續(xù)時(shí)間。定時(shí)器啟動(dòng)后，它便在原來的數(shù)值上開始進(jìn)行加1計(jì)數(shù)，若程序開始時(shí)，沒有設(shè)置TH1和TL1，則系統(tǒng)默認(rèn)它們的值都是0，因?yàn)榫д襁x擇的頻率為12MHZ，又因?yàn)?2個(gè)時(shí)鐘周期為一個(gè)機(jī)器周期，那么此時(shí)系統(tǒng)的機(jī)器周期為1us，計(jì)滿TH1和TL1需要65536個(gè)數(shù)，再來一個(gè)脈沖計(jì)數(shù)定時(shí)器就會(huì)產(chǎn)生溢出，這時(shí)定時(shí)器申請中斷。 要計(jì)2000個(gè)數(shù)，TH1和TL1中應(yīng)該裝入的總數(shù)為655362000=63536,把63536對256求模：63536/256=248，用十六進(jìn)制表示為0xf8,把63536對256求余：63536%256=96，用十六進(jìn)制表示為0x30 。 定時(shí)器子程序框圖 EEPROM子程序設(shè)計(jì) STC89C52單片機(jī)內(nèi)部自帶有2KB的EEPROM，STC單片機(jī)是利用IAP技術(shù)實(shí)現(xiàn)的EEPROM，內(nèi)部Flash擦寫次數(shù)可達(dá)100 000次以上。 根據(jù)對EEPROM的操作，將需要的數(shù)據(jù)存入EEPROM中，在需要使用時(shí)，將數(shù)據(jù)從EEPROM中讀取出來，這都是基于EEPROM優(yōu)良的讀寫、擦除性能。所以本設(shè)計(jì)的數(shù)據(jù)部分只采用了EEPROM的第一扇區(qū)，將設(shè)置的最小報(bào)警距離存放進(jìn)第一扇區(qū)，每次將超聲波測距測到的距離與EEPROM中存放的距離進(jìn)行比較，標(biāo)志部分則放在另外的扇區(qū)內(nèi)。 STC89C52單片機(jī)內(nèi)部EEPROM地址表扇區(qū)起始地址結(jié)束地址第一扇區(qū)2000H21FFH第二扇區(qū)2200H23FFH第三扇區(qū)2400H25FFH第四扇區(qū)2600H27FFH第五扇區(qū)2800H29FFH第六扇區(qū)2A00H2BFFH第七扇區(qū)2C00H2DFFH第八扇區(qū)2E00H2FFFH5 硬件調(diào)試與分析 硬件調(diào)試 在用焊錫和電烙鐵焊接完硬件電路后，利用STCISP將編譯好的程序下載到單片機(jī)中，（RXD）,(TXD)口作為下載數(shù)據(jù)口，也可以直接將單片機(jī)放進(jìn)單片機(jī)開發(fā)板中下載，這樣可以減少實(shí)物的焊接，本設(shè)計(jì)就是直接利用單片機(jī)開發(fā)板下載的。在實(shí)物焊接完成后，給單片機(jī)載入程序，單片機(jī)可能會(huì)出現(xiàn)各種運(yùn)行不正常，但是如果之前已經(jīng)在面包板上成功驗(yàn)證過，則只需要檢查整個(gè)實(shí)驗(yàn)板是否焊接好就可以很容易的判斷實(shí)物是否正確。 結(jié)果分析完成實(shí)物的調(diào)試后，接下來就是對實(shí)物的精確性進(jìn)行驗(yàn)證了，通過對實(shí)際距離和該設(shè)計(jì)測量出來的距離進(jìn)行比較，分析比較本設(shè)計(jì)的可利用性。15048492808081+1160161160+1240240243+3320316320440040139644804784812 本設(shè)計(jì)在設(shè)計(jì)時(shí)，其范圍為2cm到500cm。4cm之內(nèi)，當(dāng)距離較小時(shí)，其測量值較準(zhǔn)確；隨著測量距離的增大，測量的準(zhǔn)確性降低，誤差越來越大。、焊接的，可能在設(shè)計(jì)方面有不利于該器件穩(wěn)定的因素，在焊接時(shí)也可能出現(xiàn)很多漏洞，所以造成結(jié)果不夠準(zhǔn)確。，所以對于汽車倒車防撞系統(tǒng)來說，隨著一年四季室內(nèi)外溫度變化，本設(shè)計(jì)可能造成測量結(jié)果存在較大誤差。致謝歷時(shí)將近五個(gè)月的時(shí)間，終于完成了畢業(yè)設(shè)計(jì)，從畢業(yè)設(shè)計(jì)選題，設(shè)計(jì)準(zhǔn)備到完成實(shí)物的設(shè)計(jì)，再到最終論文的寫作過程中,遇到了很多的困惑，都在老師和同學(xué)的指導(dǎo)下度過了。在大四結(jié)束時(shí)，我們每個(gè)人都會(huì)踏上自己的工作崗位，或者繼續(xù)自己的學(xué)業(yè)，但無論走什么樣的道路，學(xué)習(xí)仍然是最重要的事情。由于在大學(xué)的四年中，我一心一意準(zhǔn)備考研從來沒有接觸過項(xiàng)目。在這短短的幾個(gè)月我學(xué)習(xí)了單片機(jī)、C語言，還買了單片機(jī)開發(fā)板自己寫程序進(jìn)行調(diào)試，雖然都沒有很全面的學(xué)習(xí)，但是通過與實(shí)際相結(jié)合的方法學(xué)習(xí)，取得了非常不錯(cuò)的效果。在制作畢業(yè)設(shè)計(jì)的時(shí)候，由于涉及到各方面的知識，我不可避免的去接觸各個(gè)方面，我們班幾位曾經(jīng)參加過電賽、“飛思卡爾”智能車賽的同學(xué)幫助了我很多，從他們的經(jīng)驗(yàn)中，我學(xué)習(xí)到了很多也給了我很大的啟發(fā)，我很感謝他們?！　∽詈螅谖壹磳厴I(yè)之際，我由衷的感謝陜西理工學(xué)院物理與電信工學(xué)院給了我一個(gè)美好的大學(xué)生活，為我提供了良好的教育環(huán)境和學(xué)習(xí)資源，希望陜西理工學(xué)院以后發(fā)展的越來越好，培育出能多人才。 感謝那些自己也同樣被畢業(yè)設(shè)計(jì)忙的焦頭爛額的同學(xué)，雖然自己很忙，但卻仍然指導(dǎo)幫助我。張齊，杜群貴.《單片機(jī)應(yīng)用系統(tǒng)設(shè)計(jì)技術(shù)》[M].,2035. 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Russian Journal of Nondestructive Testing,2009,456:.附錄A：外文翻譯1． 外文原文Ultrasonic distance meterDocument Type and Number: United States Patent :An ultrasonic distance meter cancels out the effects of temperature and humidity variations by including a measuring unit and a reference unit. In each of the units, a repetitive series of pulses is generated, each having a repetition rate directly related to the respective distance between an electroacoustic transmitter and an electroacoustic receiver. The pulse trains are provided to respective counters, and the ratio of the counter output is utilized to determine the distance being measured.Publication Date:08/15/1995Primary Examiner: Lobo, Ian, J.A. BACKGROUND OF THE INVENTION This invention relates to apparatus for the measurement of distance and, more particularly, to such apparatus which transmits ultrasonic waves between two points.Precision machine tools must be calibrated. In the past, this has been acplished utilizing mechanical devices such as calipers, micrometers, and the like. However, the use of such devices does not readily lend itself to automation techniques. It is known that the distance between two points can be determined by measuring the propagation time of a wave travelling between two points. One such type of wave is an ultrasonic, or acoustic, wave. When an ultrasonic wave travels between two points, the distance between the two points can be measured by multiplying the transit time of the wave by the wave velocity in the medium separating the two points. It is therefore an object of the present invention to provide apparatus utilizing ultrasonic waves to accurately measure the distance between two points.When the medium between the two points whose spacing is being measured is air, the sound velocity is dependent upon the temperature and humidity of the air. It is therefore a further object of the, present invention to provide apparatus of the type described which is independent of temperature and humidity variations.B. SUMMARY OF THE INVENTIONThe foregoing and additional objects are attained in accordance with the principles of this invention by providing distance measuring apparatus which includes a reference unit and a measuring unit. The reference and measuring units are the same and each includes an electroacoustic transmitter and an electroacoustic receiver, The spacing between the transmitter and receiver of the measuring unit is the distance to be measured. In each of the units, the transmitter and receiver are coupled by a feedback loop which causes the transmitter to generate an acoustic pulse which is then fed back to the transmitter, so that a repetitive series of pulses results. The repetition rate of the units, the pulses are provided to a counter. Since both counter output is utilized to determine the describe d