一、基于單片機的信號發生器設計方案
信號(hao)發(fa)生器用于(yu)調節射頻(pin)匹配電(dian)路，可以(yi)自行設計，一(yi)般普通的(de)(de)信號(hao)發(fa)生器需要輸出正弦波(bo)、方波(bo)、三角波(bo)以(yi)及鋸(ju)齒(chi)波(bo)等信號(hao)，可通過(guo)按鍵調節信號(hao)的(de)(de)頻(pin)率(lv)以(yi)及信號(hao)的(de)(de)幅(fu)度，其具(ju)體的(de)(de)設計方案(an)如下：
1、總體方案設計
信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)發(fa)(fa)生器(qi)發(fa)(fa)送出(chu)(chu)去的(de)(de)(de)(de)是模(mo)(mo)(mo)擬(ni)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)，而單(dan)片(pian)(pian)機輸(shu)出(chu)(chu)的(de)(de)(de)(de)是數(shu)(shu)字(zi)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)，因(yin)此在(zai)(zai)(zai)設(she)計信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)發(fa)(fa)生器(qi)系統(tong)時(shi)，需(xu)要使用到(dao)(dao)數(shu)(shu)模(mo)(mo)(mo)轉換芯(xin)片(pian)(pian)，可(ke)(ke)選擇數(shu)(shu)模(mo)(mo)(mo)轉換芯(xin)片(pian)(pian)DAC0832，然(ran)后再(zai)利用運(yun)算放(fang)大器(qi)將DAC0832輸(shu)出(chu)(chu)的(de)(de)(de)(de)電流信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)轉換成電壓(ya)(ya)(ya)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)。這樣信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)發(fa)(fa)生器(qi)便(bian)輸(shu)出(chu)(chu)了(le)(le)模(mo)(mo)(mo)擬(ni)電壓(ya)(ya)(ya)。系統(tong)要輸(shu)出(chu)(chu)各種波(bo)形(xing)(xing)(xing)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)，則(ze)(ze)要求DAC0832在(zai)(zai)(zai)運(yun)放(fang)的(de)(de)(de)(de)作(zuo)用下，在(zai)(zai)(zai)不(bu)同(tong)時(shi)間點輸(shu)出(chu)(chu)不(bu)同(tong)的(de)(de)(de)(de)電壓(ya)(ya)(ya)值(zhi)(zhi)，再(zai)將這些電壓(ya)(ya)(ya)值(zhi)(zhi)連接起來，便(bian)構成了(le)(le)相應(ying)的(de)(de)(de)(de)波(bo)形(xing)(xing)(xing)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)。而要得到(dao)(dao)不(bu)同(tong)的(de)(de)(de)(de)電壓(ya)(ya)(ya)值(zhi)(zhi)，則(ze)(ze)單(dan)片(pian)(pian)機需(xu)要將8位(wei)(wei)(wei)I/O口接到(dao)(dao)DAC0832芯(xin)片(pian)(pian)的(de)(de)(de)(de)8位(wei)(wei)(wei)數(shu)(shu)據信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)輸(shu)入端，單(dan)片(pian)(pian)機通過改變(bian)(bian)8位(wei)(wei)(wei)I/O口的(de)(de)(de)(de)數(shu)(shu)字(zi)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)，便(bian)可(ke)(ke)以(yi)在(zai)(zai)(zai)DAC0832以(yi)及運(yun)放(fang)的(de)(de)(de)(de)作(zuo)用下，得到(dao)(dao)不(bu)同(tong)的(de)(de)(de)(de)電壓(ya)(ya)(ya)值(zhi)(zhi)，再(zai)在(zai)(zai)(zai)時(shi)間的(de)(de)(de)(de)作(zuo)用下形(xing)(xing)(xing)成不(bu)同(tong)的(de)(de)(de)(de)波(bo)形(xing)(xing)(xing)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)。波(bo)形(xing)(xing)(xing)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)頻率的(de)(de)(de)(de)的(de)(de)(de)(de)變(bian)(bian)化(hua)可(ke)(ke)通過改變(bian)(bian)單(dan)片(pian)(pian)機8位(wei)(wei)(wei)I/O輸(shu)出(chu)(chu)口的(de)(de)(de)(de)數(shu)(shu)據變(bian)(bian)化(hua)率來實現。
波(bo)形信(xin)(xin)號的(de)幅度由DAC0832的(de)參考電(dian)壓VREF來決定，為了確保VREF的(de)大小可變(bian)(bian)，本系統使用到了芯片(pian)PCF8591，將(jiang)PCF8591芯片(pian)的(de)模擬(ni)電(dian)壓輸出端接(jie)在DAC0832的(de)VREF上，通過改變(bian)(bian)PCF8591模擬(ni)電(dian)壓輸出值(zhi)便可改變(bian)(bian)VREF值(zhi)，從而(er)改變(bian)(bian)波(bo)形信(xin)(xin)號的(de)幅度值(zhi)。而(er)PCF8591的(de)模擬(ni)電(dian)壓輸出值(zhi)則(ze)是尤其I2C總行上的(de)數(shu)據所決定，利用單(dan)片(pian)機的(de)I/O口(kou)模擬(ni)I2C與PCF8591進行通信(xin)(xin)，那(nei)么單(dan)片(pian)機便可通過I/O口(kou)控制(zhi)VREF電(dian)壓的(de)變(bian)(bian)化(hua)，從而(er)控制(zhi)波(bo)形的(de)幅度變(bian)(bian)化(hua)。
2、系統硬件設計
（1）晶振電路設計
單片機(ji)(ji)穩定(ding)工作則需要(yao)穩定(ding)的(de)(de)(de)(de)時(shi)(shi)鐘信號，而時(shi)(shi)鐘信號則是由(you)晶振(zhen)電路(lu)(lu)產生，因(yin)此晶振(zhen)電路(lu)(lu)設(she)計的(de)(de)(de)(de)好(hao)壞直(zhi)接(jie)影響到(dao)最小(xiao)系(xi)統(tong)的(de)(de)(de)(de)穩定(ding)性。單片機(ji)(ji)的(de)(de)(de)(de)18腳(jiao)(jiao)和19腳(jiao)(jiao)為晶振(zhen)連接(jie)輸(shu)入腳(jiao)(jiao)，將晶振(zhen)X1的(de)(de)(de)(de)兩(liang)端連接(jie)到(dao)單片機(ji)(ji)18和19腳(jiao)(jiao)之(zhi)(zhi)后(hou)便會(hui)產生時(shi)(shi)鐘信號，此時(shi)(shi)的(de)(de)(de)(de)信號會(hui)存在不穩定(ding)的(de)(de)(de)(de)問題，需要(yao)在晶振(zhen)Y1的(de)(de)(de)(de)兩(liang)端分別外接(jie)一(yi)個22PF電容(rong)C1、C2到(dao)GND，該電容(rong)為晶振(zhen)的(de)(de)(de)(de)匹配電容(rong)，晶振(zhen)匹配了電容(rong)之(zhi)(zhi)后(hou)，那么產生的(de)(de)(de)(de)時(shi)(shi)鐘信號就(jiu)比較穩定(ding)。出現的(de)(de)(de)(de)頻偏也(ye)是在20PPM的(de)(de)(de)(de)范(fan)圍內。這(zhe)樣(yang)才能(neng)確保系(xi)統(tong)時(shi)(shi)鐘穩定(ding)可靠。
（2）復位電路設計
最小系統(tong)(tong)除(chu)了晶(jing)振電路(lu)之外，還需要(yao)具備復位(wei)電路(lu)，單片機上電后，啟動的(de)時候，需要(yao)復位(wei)電路(lu)先進行復位(wei)，確保(bao)系統(tong)(tong)運(yun)行的(de)起始地(di)址(zhi)一致(zhi) ，保(bao)證系統(tong)(tong)工(gong)作的(de)穩定性，復位(wei)是利用(yong)電容C3與R1來實現的(de)。
（3）波形幅度調節電路設計
為改變系(xi)(xi)統輸(shu)出(chu)的(de)波(bo)(bo)形幅度值，本系(xi)(xi)統使用(yong)到了PCF8591芯片(pian)，該芯片(pian)是一(yi)個8位CMOS數(shu)據(ju)采集器(qi)，該芯片(pian)可(ke)以將(jiang)(jiang)模(mo)擬(ni)(ni)信(xin)號(hao)轉換成(cheng)數(shu)字信(xin)號(hao)，再(zai)通過(guo)I2C數(shu)據(ju)總線(xian)將(jiang)(jiang)該數(shu)字信(xin)號(hao)發送(song)給單(dan)(dan)片(pian)機(ji)；也(ye)可(ke)以反過(guo)來，單(dan)(dan)片(pian)機(ji)通過(guo)I2C總線(xian)將(jiang)(jiang)數(shu)字信(xin)號(hao)發送(song)給PCF8591芯片(pian)，再(zai)由(you)該芯片(pian)進(jin)行數(shu)模(mo)轉換后，變成(cheng)模(mo)擬(ni)(ni)電壓(ya)(ya)再(zai)由(you)AOUT腳輸(shu)出(chu)。利用(yong)這一(yi)原理，本系(xi)(xi)統為了調節(jie)信(xin)號(hao)發生器(qi)的(de)幅度值，將(jiang)(jiang)單(dan)(dan)片(pian)機(ji)P2.0和P2.1模(mo)擬(ni)(ni)I2C與(yu)PCF8591通信(xin)，這樣(yang)單(dan)(dan)片(pian)機(ji)便(bian)可(ke)以控制PCF8591的(de)AOUT輸(shu)出(chu)端模(mo)擬(ni)(ni)電壓(ya)(ya)的(de)大小，再(zai)將(jiang)(jiang)其接入(ru)到DAC0832的(de)VREF腳上，便(bian)可(ke)以控制波(bo)(bo)形的(de)幅度。
（4）數模轉換電路設計
信(xin)(xin)號(hao)(hao)發生器(qi)產生各種波(bo)形(xing)(xing)信(xin)(xin)號(hao)(hao)使(shi)(shi)用(yong)(yong)到了DAC0832數模轉(zhuan)換芯片，該芯片內(nei)部(bu)集(ji)成(cheng)了一個8位D/A轉(zhuan)換器(qi)，一個8為DAC寄存器(qi)，一個8位輸入寄存器(qi)以及一個控制(zhi)電路，其(qi)(qi)內(nei)部(bu)采用(yong)(yong)的(de)是(shi)倒T型R-2R電阻網絡，將該數模轉(zhuan)換芯片與運(yun)算放大器(qi)LM358一起使(shi)(shi)用(yong)(yong)，便可以使(shi)(shi)運(yun)放輸出(chu)端有28 =256個電壓值輸出(chu)。在不(bu)同(tong)時間內(nei)變換輸出(chu)不(bu)同(tong)的(de)電壓值，使(shi)(shi)其(qi)(qi)產生周(zhou)期性的(de)變化便能形(xing)(xing)成(cheng)相應的(de)波(bo)形(xing)(xing)信(xin)(xin)號(hao)(hao)。
（5）按鍵中斷控制電路設計
基(ji)于單(dan)片(pian)(pian)機(ji)(ji)(ji)的(de)信(xin)號(hao)發生器(qi)要求輸出方波、三角波、鋸齒(chi)波以(yi)及正弦波信(xin)號(hao)，信(xin)號(hao)的(de)幅度(du)和頻率可(ke)(ke)調，用(yong)(yong)戶可(ke)(ke)通過(guo)系(xi)統(tong)按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)來對信(xin)號(hao)發生器(qi)進行(xing)(xing)設(she)置。在系(xi)統(tong)中，設(she)計了8個按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)，其功(gong)能分(fen)別為(wei)100HZ頻率加按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)、1hz頻率加按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)、-1hz頻率減(jian)按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)、1V電壓(ya)幅度(du)加按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)、0.1V電壓(ya)幅度(du)加按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)、-0.1V電壓(ya)幅度(du)減(jian)按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)、波形切換按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)、掃頻開(kai)關按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)。為(wei)了方便(bian)系(xi)統(tong)設(she)計，采用(yong)(yong)獨立按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)設(she)計方法，利用(yong)(yong)單(dan)片(pian)(pian)機(ji)(ji)(ji)P1口(kou)將(jiang)各按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)連接，通過(guo)軟件(jian)將(jiang)P1口(kou)設(she)置成上(shang)拉狀態。當沒(mei)有(you)(you)按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)按(an)(an)(an)(an)(an)(an)下(xia)時，單(dan)片(pian)(pian)機(ji)(ji)(ji)P1口(kou)中的(de)所(suo)有(you)(you)I/O口(kou)檢測的(de)到時高電平；當有(you)(you)按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)按(an)(an)(an)(an)(an)(an)下(xia)時，則該(gai)按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)對應單(dan)片(pian)(pian)機(ji)(ji)(ji)的(de)I/O口(kou)會被拉低，變成低電平。單(dan)片(pian)(pian)機(ji)(ji)(ji)便(bian)能檢測到，從(cong)而(er)調用(yong)(yong)該(gai)按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)程序執行(xing)(xing)相應的(de)功(gong)能。
（6）電源電路設計
本(ben)系(xi)統(tong)(tong)電路設計是在Proteus仿真(zhen)軟(ruan)(ruan)件(jian)上(shang)設計，該(gai)仿真(zhen)軟(ruan)(ruan)件(jian)有(you)各(ge)種電源(yuan)，可(ke)直(zhi)接(jie)調(diao)用。無需(xu)使用電壓(ya)(ya)轉換芯片。在本(ben)系(xi)統(tong)(tong)單片機使用5V電壓(ya)(ya)供電，而為(wei)了使輸出波形幅度(du)為(wei)10V，則PCF8591采(cai)用10V電壓(ya)(ya)供電，而運算放大(da)器采(cai)用±15V供電，直(zhi)接(jie)從仿真(zhen)軟(ruan)(ruan)件(jian)上(shang)取電源(yuan)即可(ke)。
3、系統軟件設計
完成proteus軟件(jian)(jian)(jian)電(dian)路圖(tu)設計之后(hou)，接下來需要(yao)對單片(pian)機編寫(xie)(xie)驅動(dong)程(cheng)序，系統驅動(dong)程(cheng)序的編寫(xie)(xie)是在(zai)keil軟件(jian)(jian)(jian)平臺上(shang)完成的，Keil軟件(jian)(jian)(jian)打開后(hou)，要(yao)先建立工(gong)程(cheng)，然后(hou)在(zai)工(gong)程(cheng)當中建立一個.c文件(jian)(jian)(jian)，在(zai)此文件(jian)(jian)(jian)中編寫(xie)(xie)代碼驅動(dong)程(cheng)序：
（1）系統主程序設計
主(zhu)(zhu)(zhu)程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)是(shi)(shi)(shi)軟件系(xi)(xi)(xi)統(tong)(tong)中(zhong)最為重(zhong)要的(de)程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)，因(yin)為系(xi)(xi)(xi)統(tong)(tong)程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)是(shi)(shi)(shi)由各個(ge)子程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)所(suo)構成，而子程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)的(de)調用(yong)全部是(shi)(shi)(shi)在(zai)主(zhu)(zhu)(zhu)程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)中(zhong)來(lai)實現的(de)，主(zhu)(zhu)(zhu)程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)設(she)計的(de)好壞直接能影響到(dao)(dao)系(xi)(xi)(xi)統(tong)(tong)的(de)邏輯結構，影響到(dao)(dao)系(xi)(xi)(xi)統(tong)(tong)工作的(de)穩定性。在(zai)本系(xi)(xi)(xi)統(tong)(tong)中(zhong)，系(xi)(xi)(xi)統(tong)(tong)開始運行(xing)(xing)后，先會(hui)執(zhi)行(xing)(xing)主(zhu)(zhu)(zhu)程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)，在(zai)主(zhu)(zhu)(zhu)程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)中(zhong)對(dui)單片機及其外圍元件進行(xing)(xing)初始化設(she)置，完成初始化設(she)置之(zhi)后，系(xi)(xi)(xi)統(tong)(tong)就會(hui)執(zhi)行(xing)(xing)正弦波程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)，讓(rang)信(xin)號發生器(qi)(qi)輸(shu)出(chu)(chu)正弦波信(xin)號，然后再去(qu)檢測是(shi)(shi)(shi)否有(you)(you)按(an)(an)鍵(jian)按(an)(an)下(xia)，如(ru)果(guo)(guo)有(you)(you)按(an)(an)鍵(jian)按(an)(an)下(xia)，系(xi)(xi)(xi)統(tong)(tong)檢測到(dao)(dao)后，便會(hui)執(zhi)行(xing)(xing)相應按(an)(an)鍵(jian)的(de)程(cheng)(cheng)(cheng)(cheng)序(xu)(xu)(xu)，從而改(gai)變信(xin)號發生器(qi)(qi)輸(shu)出(chu)(chu)的(de)波形。如(ru)果(guo)(guo)沒(mei)有(you)(you)按(an)(an)鍵(jian)產生，則系(xi)(xi)(xi)統(tong)(tong)繼續保持當(dang)前波形輸(shu)出(chu)(chu)，然后再繼續去(qu)訪問是(shi)(shi)(shi)否有(you)(you)按(an)(an)鍵(jian)按(an)(an)下(xia)，如(ru)此循環下(xia)去(qu)。
（2）按鍵掃描程序設計
本(ben)系(xi)統(tong)是通過按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)來改變信號(hao)發(fa)生器的(de)波(bo)(bo)形，系(xi)統(tong)一共(gong)有八個(ge)按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)，按(an)(an)(an)(an)(an)(an)下(xia)不同按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)時(shi)，系(xi)統(tong)需要輸(shu)出(chu)(chu)不同的(de)波(bo)(bo)形。定義按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)6為(wei)波(bo)(bo)形切換(huan)按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)，按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)0為(wei)100HZ頻率(lv)增(zeng)加按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)，按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)1為(wei)1HZ頻率(lv)增(zeng)加按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)，按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)2為(wei)1HZ頻率(lv)減按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)，按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)3位1V幅度(du)增(zeng)加按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)，按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)4為(wei)0.1V幅度(du)增(zeng)加按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)，按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)5為(wei)0.1V幅度(du)減小按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)，按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)7位掃頻按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)，flang為(wei)標志位，用于判斷按(an)(an)(an)(an)(an)(an)鍵(jian)(jian)(jian)(jian)(jian)(jian)(jian)6按(an)(an)(an)(an)(an)(an)下(xia)的(de)次數當(dang)(dang)flang為(wei)1是默認輸(shu)出(chu)(chu)正弦波(bo)(bo)；當(dang)(dang)flang為(wei)2時(shi)，輸(shu)出(chu)(chu)三角波(bo)(bo)；當(dang)(dang)flang為(wei)3時(shi)輸(shu)出(chu)(chu)鋸齒波(bo)(bo)；當(dang)(dang)flang為(wei)4時(shi)，輸(shu)出(chu)(chu)方波(bo)(bo)；當(dang)(dang)flang為(wei)5時(shi)，則(ze)會令(ling)flang=1，輸(shu)出(chu)(chu)正弦波(bo)(bo)。
因(yin)此，當(dang)(dang)有(you)按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)按(an)(an)(an)(an)(an)(an)(an)下時(shi)，系(xi)(xi)統(tong)調用(yong)按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)程序會去判斷是(shi)(shi)哪個按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)按(an)(an)(an)(an)(an)(an)(an)下，如果是(shi)(shi)按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)6按(an)(an)(an)(an)(an)(an)(an)下，表示需(xu)要(yao)切換(huan)信號(hao)發生(sheng)器的(de)輸出(chu)(chu)波形(xing)(xing)，令flang+1，然后判斷flang的(de)值(zhi)，再輸出(chu)(chu)相應的(de)波形(xing)(xing)信號(hao)。當(dang)(dang)是(shi)(shi)0按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)按(an)(an)(an)(an)(an)(an)(an)下時(shi)，則(ze)系(xi)(xi)統(tong)會在原(yuan)有(you)的(de)波形(xing)(xing)上(shang)，改(gai)變其輸出(chu)(chu)頻(pin)率，使(shi)頻(pin)率增(zeng)加(jia)(jia)(jia)100HZ；當(dang)(dang)按(an)(an)(an)(an)(an)(an)(an)下的(de)是(shi)(shi)1按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)，則(ze)將頻(pin)率增(zeng)加(jia)(jia)(jia)1HZ；當(dang)(dang)2按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)按(an)(an)(an)(an)(an)(an)(an)下，則(ze)將頻(pin)率減小1HZ；當(dang)(dang)按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)3按(an)(an)(an)(an)(an)(an)(an)下時(shi)，表示要(yao)在原(yuan)有(you)波形(xing)(xing)的(de)基(ji)礎上(shang)增(zeng)加(jia)(jia)(jia)1V的(de)波形(xing)(xing)幅(fu)度(du)(du)；當(dang)(dang)4按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)按(an)(an)(an)(an)(an)(an)(an)下，則(ze)幅(fu)度(du)(du)增(zeng)加(jia)(jia)(jia)0.1V；當(dang)(dang)5按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)按(an)(an)(an)(an)(an)(an)(an)下，則(ze)幅(fu)度(du)(du)減小0.1V；當(dang)(dang)7按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)按(an)(an)(an)(an)(an)(an)(an)下，則(ze)進行掃頻(pin)。當(dang)(dang)執行完按(an)(an)(an)(an)(an)(an)(an)鍵(jian)(jian)程序后，返(fan)回系(xi)(xi)統(tong)主程序。
二、信號發生器的設計要求有哪些
基于單片機設計的信號發生器屬于簡易信號發生器，主要能產生方波、三角波和正弦波并進行仿真，這類信號發生器設(she)計好后，應滿足以下(xia)要求：
1、基本性能指標要求
（1）頻率范圍(wei)：100Hz~1kHz。
（2）輸出電壓(ya)：方波(bo)(bo) Up-p≤24V，三角波(bo)(bo) Up-p=6V，正(zheng)弦(xian)波(bo)(bo) Up-p>1V。
2、擴展性能指標要求
頻率范圍分段設(she)置10Hz~100Hz，100Hz~1kHz，1kHz~10kHz；波(bo)(bo)(bo)形特性(xing)方波(bo)(bo)(bo)t r<30us（1kHz，最大輸出(chu)時(shi)），三角(jiao)波(bo)(bo)(bo)r△<2%，正(zheng)弦(xian)波(bo)(bo)(bo)r～<5%。
