基于IA4421分布式温度和湿度采集系统英语原文及翻译.docx
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基于IA4421分布式温度和湿度采集系统英语原文及翻译.docx
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基于IA4421分布式温度和湿度采集系统英语原文及翻译
DistributedTemperatureandHumidityAcquisitionSystemBasedonIA4421
Abstract-Nurseryshedshavethecharacteristicsofstayingclosely,quantity,parameterchangingslowly,asmallamountofdata,sothearticlepresentsadistributedcentralizedmonitoringsystembasedonashort-rangeradiotransceiverIA4421chip.Thefront-endsystemcircuitchoosesingle-chipSTC89LE52RCasthecontrolofthecore,completeahumiditysensorHSl101,thetemperaturesensorDS18B20circuitandIA4421peripheralcircuitdesign,methodofCRC,aftercompletingfront-endsystemsandhardwaredesignofdatacenter,designgivesthesoftwaredesign,thecorrespondingflowchartandsomeinstances.
Keywords-IA4421;DS18B20;HSllOl;CRC;wirelesstransmission;distributed
I.INTRODUCTION
Theshort-rangewirelesstransmissiontechnologycangetmorethanonenurseryshedparametersoftemperatureandhumidityandpooledcentralizedmonitoring,thistypeofscenetemperatureandhumidityparameterschangesslowly,ittakesmoreintervaltimeindataacquisition,andtheamountofdatavalueforeachsampleissmall;fromatechnicalperspective,withthemonitoringsystemofthistypewithmanymonitoringpoints,itismoresuitabletousetheadvancedzigbeewirelessnetwork.However,examinefromaneconomicpointofview,suchprogramsaretoomuchexpensive.InthispaperaprogramcameupwithadistributedcentralizedmonitoringbasedonthewirelesschipIA4421,theprogramissuitablefortheabove-mentionedtypeofscene,andithasobviousadvantagesincost.
II.SYSTEMANDHARDWAREDESIGN
A.Systemcomponents
Withtoomanydistributedmulti-monitoringpointswhichthedistanceisshort(d<100m)anddistribution,systemdecidetoadoptashort-rangewirelesscommunicationchiptoformadistributedwirelessmonitoringsystem,showninFigure1.Therearemfrontendmonitorsandawirelessmonitoringsystemcenter,eachfront-endmonitorhasamicrocontrollercore,collectedbythetemperatureandhumiditysensorstogettemperatureandhumidityparameters,themicrocontrollersendtheparameterstothewirelessmonitoringcenterthroughfrontendwirelesscommunicationschips.
Figure1.Distributedwirelessacquisitionsystem
Wirelessmonitoringcenteristhecenterofthewholesystem,ithastakentothepollingwork,andgiveinstructionswhichwereissuedtothevariousfront-endmonitoringunits,thefront-endmonitoringunitsonlyreceiveditsownpollingcommandandthendecidedtolaunchoutoftheunitdata.Thesystemisdesignedevery3secondspollingprogram,everyminutecanbepolledto20monitoringunitsanditisbettertoextendthepollingcycleordecreasethepollmgintervaltosolvethelarger-scalemonitoringsite.
B.Front-endmonitoringunits
Front-endmonitoringunitisresponsibleforthecollectionsiteofthetemperatureandhumidityparameters,andsendthecollectedtothewirelessmonitoringcenter,thecircuitschematicshowninFigure2.DesignusesSTC89LE52RCasthecontrollercore,thecontrollerhastheadvantageofdownloadingtheprogramthroughserialport.Theinstructionsandthecodesarefullycompatiblewiththe51MCUwithinsixinterruptsources,fourmterruptprioritylevels,awatchdogtimer(WDT),theclockfrequencyupto40MHz[1].ThesystemissuppliedwithDC6V,using3.3VvoltageregulatorchipASM1117-3.3tosupplymicrocontrollerandwirelesschip.
Dallascompany'sI-WirebusdigitaltemperaturesensorDS18B20isusedintemperaturemeasurementcircuit.Thedesignusesa3-pinTO-92small-sizepackage,thetemperaturemeasurementrangeof-55to125°C,programmablefor9-12bitA/Dconversionandtheprecisiontemperatureresolutionupto0.0625°C,Thedigitalformatoftemperaturewithconvertedof12bittakesthemaximumtimeof750ms[2].Thedesignuses9bitdigitalformat,thedefaultconversionaccuracyis0.5°C,theconversiontimeisabout100ms[3].
Figure2.Circuitoffront-endmonitoringunits
HumidityacquisitionuseshumiditysensorHS1101andNE555inthecircuit,HS1101canaffecttheoscillationfrequencyoftheNE555circuitwhentheoutsidehumiditychangesandthecapacitorvalueofbothendoftheHS1101ischanged,therebychangingtheoutputfrequencyofthetimingcircuit.TheMCUsystemcalculatethehumidityfieldthroughthemeasurementofthefrequencyofitsoutput.Thesitehumidityandtheoutputfrequencycorrespondingrelationship[4]isshowninTable1.
TABLEIHUMIDITYANDTHEOUTPUTFREQUENCYCORRESPONDINGRELATIONSHIP
RF
10
20
30
40
50
60
70
80
90
Fr
7224
7100
6976
6853
6728
6600
6468
6330
6186
C.Wirelesstransceiverportionandthewirelessmonitoringcentercircuit
IntegrationAssociatesproductionofshort-rangewirelesstransceiverchipIA4421isusedinthisdesign.Thisisafullyintegrated,lowpowerconsumptionandrequiresveryfewexternalcomponents,multi-channel,programmable,lowcost,high-performancewirelesscommunicationschip[5].
ChiphasaprogrammablePLLfrequencysynthesizerwithhigh-precision,andthesendingletterfrequencyoffsetandreceiverbandwidthisalsoprogrammable,ithasgreatflexibilityinapplications.ThechipusesFSKmodulationmode,theoperatingbandisoptionalforthe433M,868Mand915M,thelargestsendingletterpowerupto8dBm,whenthereceiversensitivityis-109dBmandthebiterrorrateis10-3,theairrateupto115.2kbpS,sendinglettercurrentlessthan24mA,receivingcurrentislessthan10mA.standbycurrentisonly0.3uAthemaximumcommunicationdistanceis100metersto200meters[6].
InadditiontothecrystaloscillatorandtheantennatheIA4421peripheralcircuithasonlytwoinductorsandtwocapacitors,andtheirspecificparametersdependonthesystemofcommunicationfrequencyselecting.ThespecificparametersshowninTable2.OtherconnectionwiththeMCUpinnamesareshowninTable3,pin8ofIA4421outputsclocksignal,thereisnouse.
WhenIA4421chipisintransmittingmode,theNFFSpinoftheMCUissettinghigh,thenthemicrocontrollersendsinitializationcommandstothetransmittertosetinitializationsettings,whichsetthepreambleofAAH,synchronousformatissettingof2004,thebaudrateis9600bps,theoperatingfrequencyis915MHz,andthensendthecommand8238Htotumonthetransmitter.PinnSELsetslowwhensendingdata,andthenwritedatathroughtheSDI,eachclockcyclewriteonebit.WhenreadingoutthestatusflagbitSDOis1,thatmeanstransmitterhassentabyte,themicrocontrollerwillwritethenextbyteofdata.Whenthechipisinreceivingmode,theNFFSpinissettinglow,theoutputbufferofFIFOconnecteddirectlytotheSDOpin.Setofsynchronousformat,baudrate,operatingfrequencywiththetransmitmode.TheIA4421hasaninternal16RXdataFIFOandreceiverhasFFITreceivinginterrupt,whenthereceiveddatabitsreachesapresetnumber,FFITpinoutputshighlevel,andinstructthemicrocontrollertoreadoutthedatafromtheSDOpin.Wirelessmonitoringofthecentralpartofthecircuitusingthesamemicroprocessorandwirelesstransceiverchipasthefront-endmonitoringunit,RS232interfacecircuitisincreasedinthiscircuit.
TABLEIIIA4421CIRCUITPARAMETERSANDFREQUENCY
Freq(MHz)
C6、C7(pF)
L2(nH)
L1(nH)
433
4.7
27
390
868
3
6.8
100
915
3
6.8
100
TABLE3IA4421PINS
Pin
Name
Type
Function
Pin1
SDI
DI
Datainputoftheserialcontrolinterface
Pin2
SCK
DI
Clockinputoftheserialcontrolinterface
Pin3
nSEL
DI
Chipselectinputoftheserialcontrolinterface(activelow)
Pin4
SDO
DO
Serialdataoutputwithbushold
Pin5
NIRQ
DO
Interruptrequestoutput(activelow)
Pin6
NFFS
DI
FIFOselectinput(activelow)
Pin7
FFIT
DO
FIFOinterrupt(activehigh)
Pin8
CLK
DO
Microcontrollerclockoutput
III.SYSTEMSOFTWAREOESIGN
A.Softwaredesignoffront-endmonitoringunit
Themainfunctionofthefront-endmonitoringunitistocollecttemperatureandhumidityparameters,andsendtotheinformationcenter,soitsMCUsoftwareinadditiontothemainprogram,includingtemperaturedataacquisitionandhumiditydataacquisition,thecontrollingofthewirelesssendingletterlogic.Inordertoreducepowerconsumption,themicrocontrollerisalwaysworkinsleepmode[7],itwon'tgointothecollectionandsendingletterstatesuntilthewirelesschipiswokenupbytheinterrupt.
Inthesystemaftertheinitializationiscompleted,theMCUdirectlygointothesleepmode,thensetflagB=0.Whenthewirelesschipreceivesawake-upsignal,whenexternalinterrupthappenstheinterruptrequestflagNIRQoutputlowtowakeuptheMCV.TheexternalinterruptwillsetflagB=1,andthenthesystemwillcollectdata.ThesystemflowchartisshowninFigure3.
Figure3.Microcontrollercontrollingprogramflowchart
Partofthemainprogramofthefront-endmonitoringunitisshownbelow.
voidmain()
{ZHU_Init();
IA_Init();
While
(1)
{if(B==1)
{WEN();
SHI();
CRC();
FA();
B=0;}}}
Inordertoensurethereliabilityofdatatransmission,designaddsan8-bitCRC(cyclicredundancycheck)character,theCRCgeneratorpolynomialis:
ThegeneratorpolynomialofthelogiccircuitisshowninFigure4.AtthereceivingendusingthesameCRCcalculationinthedatareceiving,iftheremainderiszero,thenthechecksumresultiscorrect,orelseitisthewrongdata.
Input
MSBLSB
Figure4.
logiccircuit
Front-endmonitoringunitssendfivebyteseachtimetothemonitoringcente
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