microchip pic系列单片机rs232通讯应用

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1、SensorInterfaceDigitempJunior–AnRS-232Port-PoweredDigitalThermometerDdigitisthetenthsdigitofthetemperaturereading.Author:MichaelKirkhartSincetheDS1620hasaresolutionof0.5°C,thetenthsGSE.Inc.digitwilleitherbea‘0’ora‘5’.FarmingtonHillsMIEmail:kirkhart@r

2、ust.netTheCRandLFcharactersaretheASCIIcarriagereturn(ASCIIcode0x0d)andlinefeed(ASCIIcode0x0a)characters.ThesecharactersareusedtoforceOVERVIEWtheterminalprogramtoprintthenexttemperaturereadingonthenextlineonthescreen.TheyalsoserveDigitempJr.isadevicet

3、hatisdesignedtomeasureasdelimitingcharactersbetweentemperatureread-andreportambienttemperature.Whenconnectedtoings,allowingeasyimportingofacaptureddataintoaanRS-232portonanyPC,itwillperiodicallymeasurespreadsheetprogram.andreportinASCIIformtheambient

4、temperatureinExamples:degreesCelsius.Thesetemperaturereadingscanbemonitoredwithanyterminalprogram.Iftheterminal0°Cwillbetransmittedas0.0(CR)(LF)programsupportscapturetodisk,thetemperature27.5°Cwillbetransmittedas27.5(CR)(LF)-9.5°Cwillbetransmittedas-

5、9.5(CR)(LF)readingscanbesavedtodiskforfurtheranalysiswith-15.5°Cwillbetransmittedas-15.5(CR)(LF)aspreadsheetprogramorotherdataanalysistool.ThesimpleASCIIoutputformatofDigitempJr.makesitrel-Thedataistransmittedinasynchronous,NRZformatatativelyeasytowr

6、itecustomsoftwareforreceiving,9600bpswithonestartbit,onestopbit,eightdatabits,recording,andanalyzingambienttemperaturedata.andnoparity.WhileneitherhardwareorsoftwareflowBestofall,DigitempJr.requiresnoexternalpowersup-controlisused,theRTSsignalfromtheP

7、Cmustbepliesorbatteries.ItispowereddirectlybytheRS-232assertedbecauseDigitempJr.derivesitsV+supplyport.fromthePC’sRTSoutput.DATATRANSMISSIONSPECIFICATIONSWhenconnectedtoaPCRS-232port,DigitempJr.willobtainanambienttemperaturereadingandtransmitthereadi

8、ngindegreesCelsiusapproximatelyoncepersecond.Thisreadingistransmittedinthefollowingfor-mat:(-/H)(T)O.D(CR)(LF)The(-/H)charactercaneitherbeanegativesignorthehundredsdigitofthetemperaturereading.Ifthetem-peraturereadingisbetween0°Cand99.5°C,thischar-ac