[毕业论文]51系列单片机实现ad9850_dds信号源的研制

a1a0a2a3a4a5a6a8a7a7a9a11a10a12a13a14a4a15a16a17a181目录摘要3第一章方案论证41.1系统框图41.2系统模块41.2.1主控制器41.2.2正弦信号的产生71.2.3电压放大10第二章系统硬件设计102.1硬件系统总体框图102.2硬件模块设计112.2.1正弦信号产生模块112.2.2带负载输出132.2.3DDS技术的实现142.2.4键盘显示15第三章系统软件设计163.1初始化9850173.2初始化LCD183.3初始化PIC16F877程序193.4AD9850控制字的写入.20a19a20a21a22a23a24a25a26a27a27a28a29a30a31a32a33a23a34a35a36a3723.5键盘扫描显示213.6LCD显示.24总结26参考文献27致谢28a19a20a21a22a23a24a25a26a27a27a28a29a30a31a32a33a23a34a35a36a373摘要a30系统设计一个正弦信号发生器。，使用PIC16F877单片机作为中央控制器，PIC（PeripheralInterfaceController）是一种用来开发的去控制外围设备的集成电路（IC）。一种具有分散作用（多任务）功能的CPU。它的最高操作频率大约都在20MHz左右，存储器容量用做写程序的大约1K4K字节。传统的频率合成器，通常从一排晶振荡器产生的各种频率通过开关进行频率混合。也有的采用众所周知的锁相环g11Pg47g47g12g1935g3308g3244g3747频率合成。g3387g4482g3316字g1935g3308的g1478g3374发g4282，用g3316字控制g1466g1445从一个g1013g2217频率g4183产生多种频率，g1927g4368g2052g3316字合成g1935g3308g11g39g39g54g12g4051g2187g3532g2927。g903设计使用g3255g2072g2464行的g2597g1715g36g39Ig1636g3347生产的g36g39g288g240频率合成器正是g4075用g4323种g39g39g54g1935g3308的g1317g3832g3075g2602产g2870g4365一，g36g39g288g240采用g3733g1305g1853CMg50g54g1629g4028，g2915功g1755在g22g17g22g57g1634电g3240g2087为1g24g24g80g58，g2292g4282g1629g3996g1929g3633g1383g1459围为g1640g10880g167，采用28g2038g54g54g50Pg950g2635g1503g4461g3833g3252，g2066合g39g39g54g3817片g36g39g288g240，产生0g1081g24MHz频率g2230g1336的正弦信号g290g1336制信号为1KHz的正弦g975，g1336制信号的产生采用g39g39g54g1935g3308g290系统采用g3046中g3635g1010单操作g1466g3252，操作g1989单，g2265g2062，g2991系统的g2106g1383g1764g3639g1351g3839高。关键字：正弦信号PIC16F877g36g39g288g240g39g39g54g1935g3308ABSTRACTThesystemdesignasinesignalgenerator.UsingPIC16F877microchipasacentralcontroller,PIC(PeripheralInterfaceController)isthemethodwhichusedtocontrolperipheralsdevelopmentofIntegratedCircuits(IC).ACPUwithscattered(multi-task)function.Itsmaximumoperatingfrequencyis20MHzapproximatelyabout.Thememorycapacityoftheproceduresusedtowriteabout1K-4Kbytes.Thetraditionalfrequencysynthesizers,usuallyformarowofcrystaloscillatorfrequencybyswitchingfromavarietyoffrequencymixed.Someusedthewell-knownPLLtechnologytoachievefrequencysynthetic.Withtherapiddevelopmentofdigitaltechnology,usingdigitalcontrolmethodsformavarietyofsourcesinafrequencyreferencefrequency,directdigitalsynthesistechniques(DDS)suddenappearanceasanewway.ThedesignusethepopularAmericanADIcmopanysproductionAD9850frequencysynthesizers.DDStechnologyistheapplicationofthispopularproductstypically.AD9850usedtocontrolCMOSfirst,thepowerlossisonly155mWat3.3Vsupply,theexpansionofindustrialgradetemperaturerangefor-4080degrees,28feetSSOPsurfacepackagingusedformofDDSchipAD9850,a015MHzfrequencycommunicationssignalstotheneighboringletter;preparationofthesinusoidalwave1KHz,amodemsignalsusedDDStechnology;Chinesemenusystemusedthroughouttheoperation,theoperationsimple,fastandhighsystemaccuracyandstabilityKeywords:Sinesignal；PIC16F877；AD9850；DDStechnologya38a39a40a41a42a43a44a45a46a46a47a48a49a50a51a52a42a53a54a55a564第一章方案论证1.1系统框图根据题目要求，本系统主要由主控制器模块、正弦信号发生模块、输出电压放大模块、人机界面模块构成如图:a57a58a59a58a60a61a62a571.2系统模块1.2.1主控制器方案一：采用通用的51单片机AT89S52作为主控制器，完成数据处理，DDS的频率输出控制，键盘的扫描及液晶显示器的显示控制等。由于51单片机内部的RAM和ROM都比较小，考虑到实现本系统需要大量的数据处理及液晶显示需占用大量的ROM资源等，用51单片机实现本系统就需外扩RAM和ROM，实现起来比较麻烦。而且本系统需要用A/D转换器采样调制信号实现调频信号的输出，使用51单片机就需外扩一片A/D转换芯片，实现也比较麻烦。而且基于整个系统的速度要求，51单片机也不能满足要求。方案二：g51g44g38g708g51g72g85g76g83g75g72g85g68g79g44g81g87g72g85g73g68g70g72g38g82g81g87g85g82g79g79g72g85g709g7171一g12193用来g5332发的g2447控制外g3272g16786a63a64a65a66a67a68a69a70a71a72PIC16F877a73a74a64a75a76a77a78a79a80a71a72a81a82a83a84a85a86a71a72AD9850a75a87015MHZa81a82a88a89a90a91a92a93a94a95a96a97a97a98a99a100a101a86a102a93a103a104a105a1065g3803的g19610成电g17347g708g44g38g709g17g4439g1216的g7380g20652g6817作频率大g13434都g33242g19Mg43g93g5050g2503，g4396g1660器g4493量用g1582g1901g12255g5219的大g134341g46g252g23g46g4395g14422。g5647g13459g7171g20652g5627能g4628部g5647g13459，g5049作频率g19g794g22g22Mg43g93，g2499g2528g7114g6915g6357g3822g13464外g3272g16786g3803。g51g44g381g25g418g26g26g7171一g8466基于g40g51ROM的8g1313g20652g5627能g5506控制器。g994g1866g4439g1227g7696g11468g5415的g5506控制器g11468比，g4439g3324g6203g15904速度和g1207g11733压g13565方面都g7389g5468大的g6925g17839。g51g44g381g25g418g26g26g5506控制器g6164g1867g7389的g1260g17246g5627能主要g5414g2163于g4439的g12946g12628g6363g1208g19610g708Rg44Sg38g709和g6164采用的g2716g1327g708g43g68g85g89g68g85g71g709g13479构，g4439g1867g7389g2010g12175的g12255g5219g1660器g12366g19400g70812g1313g4497g6363g1208g709和数据g4396g1660器g12366g19400g7088g1313g4497数据g709。g2528g7114g2499g17828用g1016g13435g8981g8712g13459g6363g1208g17839g15904g2474数和g6203g15904，g19512g1114g17351转g6363g1208需要g1016个g2620g7411外，g1866g1325g6164g7389的g6363g1208都g2499g3324单g2620g7411内g6203g15904g17g1866g1260g2195为：1g12g51g44g38g7380大的g10317g9869g7171不g6642单g13443的g2163能g3546g12227，而g7171从实际出发，重视产品的g5627能g994g1227g7696比，靠发展g3822g12193型号来满足不g2528层次的应用要求。就实际而言，不g2528的应用对单片机g2163能和资源的需求也g7171不g2528的。g51g44g38系列从低到g20652g7389几十个型号，按照g6363g1208的g1313数g2499以g2010为g22类：初g13435产品，中极产品，g20652g13435产品。g2499以满足各g12193需要。g51g44g381g25g418g26g26g7389g23g19个引脚，g1866内部资源为ROM共g23g46、192g4395g14422RAM、8g17347A/D、g22个8g1313定g7114器、2个g38g38g51模块、三个串g15904口、1个并g15904口、11个中断源、g22g22个g44/O脚。2g12g12946g12628g6363g1208使g1866g6203g15904效率大为提g20652。g51g44g38系列8g1313g38MOS单片机g1867g7389独g10317的Rg44Sg38g13479构，数据g5647g13459和g6363g1208g5647g13459g2010g12175的g2716g1327g5647g13459g708g43g68g85g89g68g85g71g709g13479构，使g6363g1208g1867g7389单g4395长的g10317g5627，且允许g6363g1208g11733的g1313数g2499g3822于8g1313的数据g1313数，这g994传统的采用g38g44Sg38g13479构的8g1313单片机g11468比，g2499以达到2:1的g1207g11733压g13565，速度提g20652g23倍。g22g12产品上市零等待g708Zg72g85g82g87g76mg72g87g82mg68g85kg72g87g709。采用g51g44g38的低g1227OTg51型芯片，g2499使单片机g3324g1866应用g12255g5219g5332发完成后立刻使该产品上市。g23g12g51g44g38g7389g1260g17246g5332发环境。OTg51单片机g5332发系统的实g7114g5627g7171一个重要的g6363标，象普通51单片机的g5332发系统大都采用g20652档型号仿真低档型号，g1866实g7114g5627不尽理想。g51g44g38g3324推出一g8466新型号的g2528g7114推出g11468应的仿真芯片，g6164g7389的g5332发系统由专用的仿真芯片g6915g6357，实g7114g5627非常好。就我个人的经验看，还没g7389出现过仿真g13479果g994实际g17828g15904g13479果不g2528的情况。5g12g1866引脚g1867g7389防瞬态能力,通过限g8981电阻g2499以接至22g19V交g8981电源,g2499直接g994继电器控制电g17347g11468连,无须光电耦合器隔g12175，给应用带来极大方便。a89a90a91a92a93a94a95a96a97a97a98a99a100a101a86a102a93a103a104a105a1066g25g12彻底的保密g5627。g51g44g38以保密熔丝来保护g1207g11733，用户g3324烧入g1207g11733后熔断熔丝，别人再也无法读出，g19512非恢复熔丝。目前，g51g44g38采用熔丝深埋g5049艺，恢复熔丝的g2499能g5627极小。g26g12自带看门g10411定g7114器，g2499以用来提g20652g12255g5219g17828g15904的g2499靠g5627。8g12g11573g11508和低g2163g13803模g5347。g15441g9994g51g44g38g3324这方面g5062不能g994新型的Tg44g713MSg51g23g22g19g11468比，g1306g3324大g3822数应用g3342合还g7171能满足需要的。Mg76g70g85g82g70g75g76g83g1856g2508生产的g51g44g381g25g418g26g26g7171一g8466基于g40g51ROM的8g1313g20652g5627能g5506控制器。g994g1866g4439g1227g7696g11468g5415的g5506控制器g11468比，g4439g3324g6203g15904速度和g1207g11733压g13565方面都g7389g5468大的g6925g17839。由于g19555g7114g2499以g1092到需要的Og51Tg708一次g5627g13546g12255g709产品，g3252而g13565g11713g1114g2045用g51g44g381g25g418g26g26g17839g15904产品g16786g16757g5332发的g2620g7411。g51g44g381g25g418g26g26g5506控制器g6164g1867g7389的g1260g17246g5627能主要g5414g2163于g4439的g12946g12628g6363g1208g19610g708Rg44Sg38g709和g6164采用的g2716g1327g708g43g68g85g89g68g85g71g709g13479构，g4439g1867g7389g2010g12175的g12255g5219g1660器g12366g19400g70812g1313g4497g6363g1208g709和数据g4396g1660器g12366g19400g7088g1313g4497数据g709。g2528g7114g2499g17828用g1016g13435g8981g8712g13459g6363g1208g17839g15904g2474数和g6203g15904，g19512g1114g17351转g6363g1208需要g1016个g2620g7411外，g1866g1325g6164g7389的g6363g1208都g2499g3324单g2620g7411内g6203g15904。a57a58a59a96a107a108a109a58a98a110a111a112a112a113a114a57本g16786g16757采用方案二，作为主控制器。a89a90a91a92a93a94a95a96a97a97a98a99a100a101a86a102a93a103a104a105a10671.2.2正弦信号产生方案一：采用g2465g20316型g47g38g6403g14645g2419理，g17885g6333合g17878的电g4493、电g5875就能产生g11468应的正弦信号。g8504方案器g1226比较g12628单，g1306g7171g19602以达到g20652g12946度的g12255控调g14422，而且g12295定度不g20652，g6937不采用。方案二：采用DDSg6228g7427的基本g2419理。DDSg6228g7427g7171基于g49g92g84g88g76g86g87采样定理，g4570模g6323信号g17839g15904采g19610，经量g2282后g4396入g4396g1660器中g708g7609g6226g15932g709，通过g38g51g47Dg6122g13785g41g51g42Ag17839g15904g4559g3348g7609g15932输出g8886g5430的数据，再经D/A转换g9400g8886g2375g2499恢复g2419g8886g5430。根据g49g92g84g88g76g86g87采样定理g11705，要使信号能g3827恢复，g5529须满足采样频率大于g15999采样信号g7380g20652频率的2倍，g2554g2029g4570产生g9163g2484，经D/A不能恢复g2419信号。g8504方案产生的g8886g5430比较g12295定，g3324g20652频输出g7114g1262产生g3845真，而且电g17347比较复g7446，g6937不采用。方案三：直接采用DDSg19610成芯片。AD985g19g7171ADg1856g2508生产的DDS芯片，带并g15904和串g15904g2164g17745方g5347，AD985g19内g2559g2499g13546g12255DDS系统和g20652速比较器,能实现g1852数g4395g13546g12255控制的频率合成。采用g1820g17839的DDSg6228g7427g3324内部g19610成g1114g222g1313g11468g1313g13059g2164器，1g23g1313正/g17139g1325弦和g20652g5627g5627能的1g19g1313D/A转换器以及g20652速比较器。g4439通过并口和串口的频率控制g4395来g16786定g11468应的g13059g2164器的g8505长大小，g11468g1313g13059g2164器的输出数g4395g11468g1313通过g7609g15932g5483到g6164需的频率信号的采样g1552。g9994后通过转换，输出g6164需频率的正弦输出信号的频率。由于DDSg19610成芯片能达到要求，而且g14422g11477g11840g1226电g17347，g12255控调g14422能g3827方便实现。AD985g19的g5049作g2419理为:a57a58a59a115a116a117a92a118a119a120串g15904输入方g5347如图g23g6164示，g3324g58g38g47g46的上g2331g8851，g23g19g1313数据由低g1313到g20652g1313g1393次从引脚25g11Dg26g12g12239入到输入g4504g4396器，并g3324g41g52g66g56D的g14045g1926作用g991，一次g5627g6183入到数据g4504g4396器，以g7368新的输出频率g11g6122g11468g1313g12。a57a58a59a121a122a117a92a118a119a120a89a90a91a92a93a94a95a96a97a97a98a99a100a101a86a102a93a103a104a105a1068AD985g19主要g5049作g5627能g111g12单电源g5049作：g14g22g17g22Vg6122g145V。g112g12接口g12628单，g2499用8g1313并g15904口g6122串g15904口直接g16025g17745频率和g11468g1313调制数据。g11g22g12片内g7389g20652g5627能D/A转换器和g20652速比较器，g2499输出正弦g8886和方g8886。g11g23g12g7380g20652g5049作g7114g19059125Mg43g93，g222g1313频率控制g4395保g16789g3324125Mg43g93的g5049作g7114g19059g991频率g2010g17788率达g19g17g19291g43g93。g115g125g1313调g11468控制g4395，g2499实现g11468g1313调制g2163能。g11g25g12频率转换速率极g5567，g2499达2g17g22g1041g19g26次/g12198。g11g26g12低g2163g13803：g3324125Mg43g93g7114g19059频率、g145V电源g5049作g7114，g2163g13803为g228g19mg58；11g19Mg43g93g7114g19059、g14g22g17g22g89g5049作g7114，g2163g13803为155mg58。g118g12g5049作g9213度g14551g3272g4497：g16g23g19g263g794g1485g263。图1g16g25引脚g2163能Dg19g252Dg26：8g1313数据输入口，g2499g2010次并g15904转g17745g23g19g1313控制数据，Dg26g708g1254425g19脚g709也g2499以作为串g15904数据输入g12483使用；a89a90a91a92a93a94a95a96a97a97a98a99a100a101a86a102a93a103a104a105a1069Dg40g49D：数g4395g3332；DVDD：数g4395电源；g58g38g44g46：数g4395g1901入g14045g1926；g41g52g16g56D：频率g2059新g2163能信号；g38g47g46g44g49：外部g2454考g7114g19059输入，g2499以g7171g38MOS电g4388的g14045g1926g5219列g30Ag42g49D：模g6323电源；Rg40ST：DA输出电g8981的g1114控制电阻连接g12483，通常接一g2494g22g179g46g8443的电阻到g3332；g52Og56T：内部比较器输出g12483；g52Og56Tg37：内部比较器g1126g15929输出g12483；Vg44g49g49：内部比较器的g17139g11468输入g12483；Vg44g49g51：内部比较器的正g11468输入g12483；DAg38g37g47：内部的g7061g17347g12483，通常g5760g12366；g44Og56Tg37：DA的g1126g15929输出g12483；本g16786g16757采用方案三，作为g19g7941g19Mg43g93正弦信号发生。123输出电压放大方案一：采用g20652频三极g12661g1582g2163率放大。g17885g6333g5700g5415的电阻和电g4493来实现g12538合题目要求的放大倍数。g1306g7171使用三极g12661放大g7114，信号放大的g12295定g5627不g20652，g5468g19602满足题目的要求。g6937不采用。方案二：采用g4497频g17828g12651放大器g1582前g13435电压放大，AD8g195g25g2499以达到g22g19g19M的带g4497，而且频率g12295定g5627好。g6164以g3324本g16786g16757中采用g1114方案二。a89a90a91a92a93a94a95a96a97a97a98a99a100a101a86a102a93a103a104a105a10610第二章硬件设计2.1系统的总体框图如图根据上面的g16782g16789，本系统以g51g44g381g25g418g26g26单片机为g7692心，配合DDS专用芯片AD985g19，完成正弦信号的产生，并辅以各个g2163能模块完成题目的g16786g16757要求。a123a124a125a126a127a128a129a130a131a123D31D22D13D04V+6WLCK7FQ_UD8CLKIN9GND10V+11RSET12QOUT13QOUTB14IN-15IN+16DACBL17V+18IOUTB20IOUT21RST22V+23GND5D7/LOAD25D626D527D428GND19GND24U?AD9850VCCR?Res23K98714Y?66MVCCP3.4P3.2P1.4RD019RD120RD221RD322RD427RD528RD629RD730MCLR/Vpp1RB033RB134RB235RB336RB437RB538RB639RB740RA02RA13U?PIC16F877VDD1VSS2V03RES4E15E26R/W7A08D09D110D211D312D413D514D615D716SLA17SLK18LCDVCCR?2KR?250OC1C111D31Q22D42Q53D73Q64D84Q95D135Q126D146Q157D177Q168D188Q19U?74LS373R?4K7VCCa123a124a132a124a127a128a133a134a1231x5a135a136LCDa137a138a13916F877PICa140a141a142DDSAD98501K15KHza143a144a145a146a147a148a145a149a150a151a152a153a154a155a156a157a158a159a124a160a160a161a162a163a164a165a166a157a167a168a169a170112.2硬件模块设计2.2.1正弦信号产生模块正弦信号产生模块的主要部g2010g7171AD985g19。AD985g19采用g1820g17839的g38MOSg5049艺,g1866g2163g13803g3324g22g17g22V供电g7114仅为155mg58,g9213度g14551g3272为g16g23g19g7948g19g263,采用28脚SSOg51g15932面封g16025g5430g5347。图2g17g22为g1866g13464成框图。图中层虚g13459内g7171一个完整的g2499g13546g12255DDS系统,外层虚g13459内包g2559g1114AD985g19的主要g13464成部g2010。AD985g19内g2559g2499g13546g12255DDS系统和g20652速比较器,能实现g1852数g4395g13546g12255控制的频率合成。g2499g13546g12255DDS系统的g7692心g7171g11468g1313g13059g2164器,g4439由一个g2164法器和一个g49g1313g11468g1313g4504g4396器g13464成，g49为g222；每来一个外部g2454考g7114g19059,g11468g1313g4504g4396器便以g8505长M递g2164；g11468g1313g4504g4396器的输出g994g11468g1313控制g4395g11468g2164后g2499输入到正弦g7609询g15932g3332g3348上；正弦g7609询g15932包g2559一个正弦g8886g2620g7411的数g4395幅度信息,每一个g3332g3348对应正弦g8886中g19g794g22g25g19g14551g3272的一个g11468g1313g9869；g7609询g15932把输入g3332g3348的g11468g1313信息映射成正弦g8886幅度信号,g9994后驱动DAg38以输出模g6323量。a123a124a125a171a172a173a174a175a176a160a177a178a131a123g11468g1313g4504g4396器每过2g49/M个外部g2454考g7114g19059后返回到初始状态一次,g11468应g3332正弦g7609询g15932每经过一个循环也回到初始g1313置,从而使整个DDS系统输出一个正弦g8886。输出的正弦g8886g2620g7411TO=Tg702g49/M，频率g73g82g88g87=Mg73g70/2g49，Tg70、g73g70g2010别为外部g2454考g7114g19059的g2620g7411和频率。AD985g19采用g222g1313的g11468g1313g13059g2164器g4570信号截断成1g23g1313输入到正弦g7609询g15932,g7609询g15932的输出再g15999截断成1g19g1313后输入到DAg38，DAg38输出g1016个g1126g15929的电g8981。DAg38满量g12255输出电g8981通过一个外接电阻RSg40T调g14422,AD985g19g12946密g7114g19059源和g1901入频率g11468g1313控制g4395之后就g2499产生一个频率和g11468g1313都g2499a153a154a155a156a157a158a159a124a160a160a161a162a163a164a165a166a157a167a168a169a17012g13546g12255控制的模g6323正弦g8886输出,g8504正弦g8886g2499直接用作频率信号源g6122经内部的g20652速比较器转换为方g8886输出。g3324125Mg43g93的g7114g19059g991,g222g1313的频率控制g4395g2499使AD985g19的输出频率g2010g17788率达g19g17g19291g43g93；并g1867g73895g1313g11468g1313控制g1313,而且允许g11468g1313按增量18g19、9g19,g235,22g175,11g1725g6122这些g4395的g13464合g17839g15904调整。a123a124a125a179a172a173a174a175a176a160a180a181a1232-5AD9850a182a183a123a153a154a155a156a157a158a159a124a160a160a161a162a163a164a165a166a157a167a168a169a17013D04D13D22D31D428D527D626D725RSET12FQ-UD8WCLK7RD019RD120RD221RD322RD427RD528RD629RD730MCLR/VPP1RA02RA13a1232-6AD9850a184PIC16F877a133a134a182a1832.2.2带负载输出要达到g25V1V的带g17139g17745输出，我g1216g1820使用g4497频g17828放AD8g195g25g1582前g13435放大，为g1114达到合g17878的电压增益，我g1216使用g1114g1016g13435放大切换，g6925变放大的g13435数以便g17878应增益要求；经g17828放输出的电压电g8981较弱，带g17139g17745能力不强，g6164以输出g12483接上g11145g19电阻，输出幅度能达到g16786g16757的要求。a123a124a125a185a186a187a188a189a153a154a155a156a157a158a159a124a160a160a161a162a163a164a165a166a157a167a168a169a170142.2.3正弦调制信号的产生1k正弦调制信号的产生采用DDSg6228g7427。DDSg6228g7427采用g1852数g4395g6228g7427实现频率合成，和g1866g4439一般的频率合成g6228g7427g11468比，g7389一些突出的g1260g9869和独g10317的g5627能：DDSg3324g11468对带g4497、频率转换g7114g19400、频率g2010g17788率、g11468g1313连续g5627、正交输出以及g19610成g2282等一系列g5627能g6363标方面远远超过g1114传统频率合成g6228g7427g6164能达到的g8712平。DDS的实现g2419理如g991图g6164示:a123a124a125a175a173a173a190a191a192a193a194a195DDSg6228g7427的实现g1393赖于g20652速、g20652g5627能的数g4395器g1226。g2499g13546g12255逻辑器g1226以g1866速度g20652、规模大、g2499g13546g12255，以及g7389强大g40DA软g1226g6915g6357等g10317g5627，十g2010g17878合实现频率的合成。由于本系统要求产生1g46g43g93的正弦调制信号,g3845真度要求要小,而且g12295定g5627要好,DDS的g3845真度g19512受D/A转换器本身的噪声影响外，还g994g4396g1660深度M和D/Ag4395长g7389密切关系g17系采用Ag79g87g72g85g68g1856g2508的g38g51g47D器g1226g40g51Mg26128，g1866g7380g20652g5049作频率为12g19Mg43g93，典型g2499用门5g19g19g19门，DDSg16786g16757电g17347产生的g8886g5430g4396g3324g20652次谐g8886，须g17839g15904低通g9400g8886使g8886g5430平滑，为使通带内的起伏g7380小，我g1216采用g1114巴g10317沃斯二阶低通g9400g8886器，如g991图，巴g10317沃思二阶低通g9400g8886器的截止频率为g73g70=1/2Rg38。由于g2494需产生1g46g43g93的正弦信号,本系统g16786g16757的g9400g8886器的截至频率为2g46g43g93。a153a154a155a156a157a158a159a124a160a160a161a162a163a164a165a166a157a167a168a169a17015a123a124a125a174a196a197a198a199a200a2012.2.4LCD液晶显示g3324各g12193智能仪器和便携产品中，g19512g1114能显示g4395g12538，数g4395之外，通常还能显示各g12193突图g5430，曲g13459，和屏幕的上g991滚动，动画，闪烁，g2375文本显示g2163能，数据显示模块的首g17885应该g7171液晶显示器，g3252为g4439能g3827方便、明g1114g3332g16789明传输数据的正确g5627。由于本系统重g9869g3324g994无g13459传输，如果采用不g2559g4395库的液晶显示器，那么大部g2010g7114g19400g1262花g3324g1582g4395库上面。g3252g8504，数据显示模块采用带g4395库的液晶显示器。采用g1114Tg42128g25g23A液晶显示器，该显示器g7171128g104g25g23g9869阵g5347液晶，g1866g13479构见g991图g17a123a124a125a126a160a202a203a126a124a175a161a179a172a204a205a206a207a208a180a181a123a153a154a155a156a157a158a159a124a160a160a161a162a163a164a165a166a157a167a168a169a17016RB033TA35RE08RE19RB019RB120RB221RB322RB427RB528RB629RB730U2PIC16F877123456789101112131415161718LCD250VCCGND2KVCCGNDVCCGNDVDDVSS/RESV0E1E2R/WA0D0D1D2D3D4D5D6D7SLASLKa123a124a125a126a126a126a209a210a173a184a211a212a210a126a161a213a175a185a185a193a182a1832.2.5键盘扫描输入通常情况g991,需要用键盘输入数据，g6122对g12255g5219g17839g15904g12661理，g3252g8504g3324单片机的应用和调试中，键盘g7171一个g5529不g2499少的部g2010，键盘的扩展g2499以通过一些g1867g7389g10317殊g2163能的g10317殊芯片，如各g12193g12239g1313g4504g4396器实现，g15441g9994接口复g7446，g1306g7171用到的单片机的接口较少，g2499直接用单片机的引脚作为键盘的g15904和列，g1306对单片机g7389g10317殊的较g20652的要求，尽g12661扩展键盘数量受引脚数量的限制，g1306g13546g12255g12628单，而且g4493易扩展。a214a215a216a217a218a219a220a221a222a222a223a224a225a226a227a228a218a229a230a231a23217a233a234a235a236a234a237a238a239a240a241a242第三章系统软件设计软g1226部g2010主要包括g1114g1867g7389友好界面的g6817作菜单，各g12193信号的g16786置和控制。正弦g8886产生过g12255为：频率g16786置，数据处理，g9994后控制DDS芯片完成各g12193频率的正弦g8886产生；调频信号产生过g12255：通过A/D转换器采g19610调制信号，g9994后根据调制信号的幅度g16757g12651出频偏，把频偏数据g991g17745到DDSg2375g2499实现调频信号的产生。a243a244a245a239a240a246a247F0=1?a245a239a240a248a249a250a251a252a237a253a254a255a103a0a79a1a246a247F0=1?a123a123a2a3a4a5a6a7a8a234a9a9a10a11a12a13a14a15a6a16a17a18a1918软件流程图：a233a60a235a236a124a20a21a103a233a1263.1初始化A/D9850g89g82g76g71g76g81g76g87g66985g19g1