DSP28335教程7專業(yè)知識講座

Analog-to-DigitalConverterModule6TMS320C28x?MCUWorkshopCopyright?2023TexasInstruments.Allrightsreserved.

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TO第1頁LearningObjectivesUnderstandtheoperationoftheAnalog-to-Digitalconverter(ADC)UsetheADCtoperformdataacquisition第2頁ADCModuleBlockDiagram(CascadedMode)12-bitA/DConverterSOCEOCSoftwareADCINA0ADCINA1ADCINA7ADCINB0ADCINB1ADCINB7S/HAS/HBMUXMUXARESULT0RESULT1RESULT2RESULT15ResultMUXExternalPin(GPIO/XINT2_ADCSOC)ePWM_SOC_AePWM_SOC_BMUXBChSel(CONV00)ChSel(CONV01)ChSel(CONV02)ChSel(CONV03)ChSel(CONV15)MAX_CONV1AutosequencerStartSequenceTriggerSEQ1ADCfull-scaleinputrangeis0to3V第3頁ADCModuleBlockDiagram(Dual-Sequencermode)RESULT8RESULT9RESULT15ResultMUXRESULT0RESULT1RESULT7ResultMUX12-bitA/DConverterS/HAS/HBMUXSoftwareePWM_SOC_AExternalPinSOC1/EOC1SequencerArbiterSOC2/EOC2SoftwareePWM_SOC_BADCINA0ADCINA1ADCINA7ADCINB0ADCINB1ADCINB7MUXAMUXBMUXMUXChSel(CONV00)ChSel(CONV01)ChSel(CONV07)MAX_CONV1AutosequencerStartSequenceTriggerSEQ1(GPIO/XINT2_ADCSOC)ChSel(CONV08)ChSel(CONV09)ChSel(CONV15)MAX_CONV2AutosequencerStartSequenceTriggerSEQ2ADCfull-scaleinputrangeis0to3V第4頁ADCOperatingModeChoicesTheusercanmakeonechoicefromeachcategorybelowChoicesarecompletelyindependent*SequencerModeCascadedDualSamplingModeSequentialSimultaneousRunModeStart/StopContinuous* NotethatusingContinuousRunmodewithDualSequencergenerallydoesn’tmakesensesincesequencer#2willnotgettodoanyconversions!第5頁ADCClockingFlowCLKIN(30MHz)HSPCLK(150MHz)ADCCLKPSbitsADCTRL30110bFCLK(12.5MHz)FCLK=HSPCLK/(2*ADCCLKPS)ADCCLK=FCLK/(CPS+1)ADCCLK(12.5MHz)CPSbitADCTRL10bToADCpipelinesamplingwindowACQ_PSbitsADCTRL10111bNote: MaximumF2833xADCCLKis25MHz,butINL(integralnonlinearityerror)isgreater above12.5MHz.Seethedevicedatasheetformoreinformation.SYSCLKOUT(150MHz)PLLSTSDIVSELbits10b

(/2)ToCPUsamplingwindow=(ACQ_PS+1)*(1/ADCCLK)PCLKCR0.ADCENCLK=1HISPCPHSPCLKbits000b(/1)PLLCRDIVbits1010b

(x10)第6頁Analog-to-DigitalConverterRegisters

AdcRegs.register(labfile:Adc.c)ADCTRL1 ADCControlRegister1ADCTRL2 ADCControlRegister2ADCTRL3 ADCControlRegister3ADCMAXCONV ADCMaximumConversionChannelsRegisterADCCHSELSEQ1 ADCChannelSelectSequencingControlRegister1ADCCHSELSEQ2 ADCChannelSelectSequencingControlRegister2ADCCHSELSEQ3 ADCChannelSelectSequencingControlRegister3ADCCHSELSEQ4 ADCChannelSelectSequencingControlRegister4ADCASEQSR ADCAutosequenceStatusRegisterADCRESULT0 ADCConversionResultBufferRegister0ADCRESULT1 ADCConversionResultBufferRegister1ADCRESULT2 ADCConversionResultBufferRegister2

ADCRESULT14 ADCConversionResultBufferRegister14ADCRESULT15 ADCConversionResultBufferRegister15ADCREFSEL ADCReferenceSelectRegisterADCOFFTRIM ADCOffsetTrimRegisterADCST ADCStatusandFlagRegisterRegister Description第7頁ADCControlRegister1

AdcRegs.ADCTRL1EmulationSuspendMode00=freerun(donotstop)01=stopaftercurrentsequence10=stopaftercurrentconversion11=stopimmediatelyADCModuleReset0=noeffect1=reset(setbackto0byADClogic)AcquisitionTimePrescale(S/H)ACQWindow=(ACQ_PS+1)*(1/ADCCLK)SUSMODACQ_PSCPS7RESET15reserved11-813-1214ConversionPrescale0:ADCCLK=FCLK/11:ADCCLK=FCLK/2UpperRegister:第8頁ADCControlRegister1

AdcRegs.ADCTRL1SequencerMode0=dualmode1=cascadedmodeContinuousRun0=stopsafterreachingendofsequence1=continuous(startsalloveragainfrom“initialstate”)SequencerOverride(functionsonlyifCONT_RUN=1)0=sequencerpointerresetsto“initialstate”atendofMAX_CONVn1=sequencerpointerresetsto“initialstate”after“endstate”SEQ_OVRDSEQ_CASC3-0CONT_RUNreserved456LowerRegister:第9頁ADCControlRegister2

AdcRegs.ADCTRL2InterruptEnable(SEQ1)0=interruptdisable1=interruptenableePWMSOCB(cascadedmodeonly)0=noaction1=startbyePWMsignalResetSEQ10=noaction1=immediateresetSEQ1to“initialstate”StartConversion(SEQ1)0=clearpendingSOCtrigger1=softwaretrigger-startSEQ1ePWMSOCASEQ1MaskBit0=cannotbestartedbyePWMtrigger1=canbestartedbyePWMtriggerInterruptMode(SEQ1)0=interrupteveryEOS1=interrupteveryotherEOSRST_SEQ19ePWM_SOCB_SEQ12reserved1115SOC_SEQ1INT_ENA_SEQ1INT_MOD_SEQ1reservedePWM_SOCA_SEQ18141310UpperRegister:第10頁ADCControlRegister2

AdcRegs.ADCTRL2InterruptEnable(SEQ2)0=interruptdisable1=interruptenableExternalSOC(SEQ1)0=noaction1=startbysignalfromADCSOCpinStartConversion(SEQ2)(dual-sequencermodeonly)0=clearpendingSOCtrigger1=softwaretrigger-startSEQ2ePWMSOCBSEQ2MaskBit0=cannotbestartedbyePWMtrigger1=canbestartedbyePWMtriggerInterruptMode(SEQ2)0=interrupteveryEOS1=interrupteveryotherEOSRST_SEQ21EXT_SOC_SEQ14reserved37SOC_SEQ2INT_ENA_SEQ2INT_MOD_SEQ2reservedePWM_SOCB_SEQ20652LowerRegister:ResetSEQ20=noaction1=immediateresetSEQ2to“initialstate”第11頁ADCControlRegister3

AdcRegs.ADCTRL3SamplingModeSelect0=sequentialsamplingmode1=simultaneoussamplingmodeADCClockPrescale0 :FCLK=HSPCLK1toF :FCLK=HSPCLK/(2*ADCCLKPS)ADCBandgapandReferencePowerDown00=powereddown11=poweredupADCPowerDown(exceptBandgap&Ref.)0=powereddown1=poweredupADCBGRFDNADCCLKPSSMODE_SEL015-8reserved4-17-6ADCPWDN5第12頁MaximumConversionChannelsRegister

AdcRegs.ADCMAXCONVMAX_CONV2_2MAX_CONV2_1MAX_CONV2_0MAX_CONV1_3MAX_CONV1_2MAX_CONV1_1MAX_CONV1_0reservedCascadedModeDualModeSEQ2SEQ1Bitfieldsdefinethenumberofconversionspertrigger(binary+1)Eachsequencerstartsatthe“initialstate”andadvancessequentiallyEachwillwrapatthe“endstate”unlesssoftwareresetsitsooner SEQ1 SEQ2 CascadedInitialstate CONV00 CONV08 CONV00Endstate CONV07 CONV15 CON7第13頁ADCInputChannelSelectSequencingControlRegisters

AdcRegs.ADCCHSELSEQxADCCHSELSEQ115-1211-87-43-0CONV03CONV02CONV01CONV00ADCCHSELSEQ2CONV07CONV06CONV05CONV04ADCCHSELSEQ3CONV11CONV10CONV09CONV08ADCCHSELSEQ4CONV15CONV14CONV13CONV12Forpurposesoftheseregisters,channelnumbersare:0=ADCINA0 8=ADCINB07=ADCINA7 15=ADCINB7第14頁Example-SequencerConfiguration(1of2)ConfigurationRequirements:ePWMtriggerstheADCThreeautoconversions(V1,V2,V3)offtrigger1(CTR=0)Threeautoconversions(I1,I2,I3)offtrigger2(CTR=PRD)ADCincascadedsequencerandsequentialsamplingmodesV1,V2,V3I1,I2,I3V1,V2,V3I1,I2,I3ePWMTimeBaseCounter

ePWMOutput第15頁Example-SequencerConfiguration(2of2)

Bits

15-1211-87-43-0 I1V3V2V1 ADCCHSELSEQ1 xxI3I2 ADCCHSELSEQ2RESULT0V1RESULT1V2RESULT2V3RESULT3I1RESULT4I2RESULT5I3MAX_CONV1issetto2andChannelSelectSequencingControlRegistersaresetto:Onceresetandinitialized,SEQ1waitsforatriggerFirsttrigger,threeconversionsperformed:CONV00(V1),CONV01(V2),CONV02(V3)MAX_CONV1valueisresetto2(unlesschangedbysoftware)SEQ1waitsforsecondtriggerSecondtrigger,threeconversionsperformed:CONV03(I1),CONV04(I2),CONV05(I3)Endofsecondsequence,ADCResultsregistershavethefollowingvalues:SEQ1waitsatcurrentstateforanothertriggerUsercanresetSEQ1bysoftwaretostateCONV00andrepeatsametrigger1,2session第16頁ADCConversionResultRegistersLSBMSB15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0LSBMSB15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0AdcRegs.ADCRESULTx,x=0-15 (2wait-stateread)Input Digital AdcRegs. AdcMirror.Voltage Result ADCRESULTx ADCRESULTx3.0 FFFh 1111|1111|1111|0000 0000|1111|1111|11111.5 7FFh 0111|1111|1111|0000 0000|0111|1111|11110.00073 1h 0000|0000|0001|0000 0000|0000|0000|00010 0h 0000|0000|0000|0000 0000|0000|0000|0000AdcMirror.ADCRESULTx,x=0-15 (1wait-stateread)第17頁HowCanWeHandleSignedInputVoltages?Example:-1.5V

Vin

+1.5V1)Add1.5voltstotheanaloginputVin1.5VADCINxGNDADCLO-+RRR-+RRC28x#include“DSP2833x_Device.h”#defineoffset0x07FFvoidmain(void){

int16value; //signedvalue=AdcMirror.ADCRESULT0–offset;}2)Subtract“1.5”fromthedigitalresult第18頁Built-InADCCalibrationTIreservedOTPcontainsdevicespecificADCcalibrationdata(2words)TheBootROMcontainsanADC_cal()routine(6words)thatcopiesthecalibrationdatatotheADCREFSELandADCOFFTRIMregistersADC_cal()mustberuntomeettheADCspecsinthedatasheetTheBootloaderautomaticallycallsADC_cal()suchthatnoactionisnormallyrequiredbytheuserIfthebootloaderisbypassed(e.g.,duringdevelopment)ADC_cal()shouldbecalledbytheapplication:#defineADC_cal_func_ptr(void(*)(void))0x380080voidmain(void){(*ADC_cal_func_ptr)();//callADC_cal()}第19頁Iftheoffsetandgainerrorsinthedatasheet*areunacceptableforyourapplication,oryouwanttoalsocompensateforboardlevelerrors(e.g.,sensororamplifieroffset),youcanmanuallycalibrateOffseterrorCompensatedinanalogwiththeADCOFFTRIMregisterNoreductioninfull-scalerangeGroundaninputpin,setADCOFFTRIMtomaximumoffseterror,andtakeareadingRe-adjustADCOFFTRIMtomakeresultzeroGainerrorCompensatedinsoftwareSomelossinfull-scalerangeRequiresuseofasecondADCinputpinandanupper-rangereferencevoltageonthatpin;see“TMS320280xandTMS320F2801xADCCalibration”appnote#SPRAAD8formoreinformationTip:Tominimizemux-to-muxvariationeffects,putyourmostcriticalsignalsonasinglemuxandusethatmuxforcalibrationinputsManualADCCalibrationADCOFFTRIMCHCH12-bitA/DConverterMUX*+/-15LSBoffset,+/-30LSBgain.Seedevicedatasheetforexactspecifications第20頁ADCReferenceSelection

AdcRegs.ADCREFSELTheF28335ADChasaninternalreferencewithtemperaturestabilityof~50PPM/°C*Ifthisisnotsufficientforyourapplication,thereistheoptiontouseanexternalreference*Externalreferencechoices:2.048V,1.5V,1.024VThereferencevalueDOESNOTchangethe0-3Vfull-scal