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1、CHAPTER2SerialCommunicationsSerialcommunicationisoneoftheoldestmechanismsfordevicestocommunicatewitheachother.StartingwiththeIBMPCandcompatiblecomputers,almostallcomputersareequippedwithoneormoreserialportsandoneparallelport.Asthenameimplies,aserialportsendsandreceivesda
2、taserially,onebitatatime.Incontrast,aparallelportsendsandreceivesdataeightbitsatatime,usingeightseparatewires.■TipForserialcommunicationtowork,youjustneedaminimumofthreewires—onetosend,onetoreceive,andonesignalground.Forparallelcommunication,youneedeightwires.Despitethec
3、omparativelyslowertransferspeedofserialportsoverparallelports,serialcommunicationremainsapopularconnectivityoptionfordevicesbecauseofitssimplicityandcost-effectiveness.Figure2-1showssomeofthedevicesthatuseaserialporttoconnecttothecomputer.Usingaserialport,youcanconnectto
4、amodem,amouse,oradevicesuchasabridge/routerforconfigurationpurposes.Figure2-1.Somecommonserialdevices—modem,mouse,androuter6768CHAPTER2■SERIALCOMMUNICATIONSAlthoughconsumerproductstodayareusingUSBconnectionsinplaceofserialconnec-tions,stillalotofdevicesuseserialportsasth
5、eirsoleconnectionstotheoutsideworld.Inthischapter,youwilllearnhowtocommunicatewithotherserialdevicesusingthenewSerialPortclassavailableinthe.NETFramework2.0andthe.NETCompactFramework2.0.Inparticular,youwillbuildthreeprojectsthatillustratehowtouseserialcommunications.Thef
6、irstprojectisachatapplicationthatallowstwocomputers(connectedusingeitheraserialcableoraBluetoothconnection)tocommunicate.Andusingthefoundationofthisapplication,youcanextendittocommunicatewithotherexternalserialdevicessuchascellularphones.YouwilllearnhowtousetheATcommands
7、toprogrammaticallycontrolyourmobilephonesthroughaserialBluetoothconnection.ThesecondprojectisaPocketPCchatapplication,whichissimilartothefirstproject.ThethirdapplicationshowshowtocommunicatewithaGPSreceiverandthenextracttheusefuldatafordisplayingthecurrentlocationonamap.
8、SomeSerialCommunicationBasicsAsmentioned,aserialdevicesendsandreceivesdataonebitatatime.Somedevicescans
