單片機(jī)微控制器07

1、數(shù)字信號(hào)處理的數(shù)字信號(hào)處理的采樣問題采樣問題 采樣定理采樣定理 采樣率大于信號(hào)最高頻率的采樣率大于信號(hào)最高頻率的2倍。倍。 通常取最高頻率的通常取最高頻率的2.5-4倍。倍。 采樣采樣/保持保持 給定時(shí)間段采樣。給定時(shí)間段采樣。 保持期間進(jìn)行保持期間進(jìn)行A/D轉(zhuǎn)換。轉(zhuǎn)換。采樣采樣/保持保持信號(hào)信號(hào)接通：采樣接通：采樣關(guān)斷：保持關(guān)斷：保持A/D轉(zhuǎn)換轉(zhuǎn)換數(shù)值量化數(shù)值量化3FF0001LSB1/2LSBVrefVref/2輸入電壓輸入電壓量化值量化值R/2R模式模式A/D轉(zhuǎn)換器轉(zhuǎn)換器V/F轉(zhuǎn)換器實(shí)現(xiàn)轉(zhuǎn)換器實(shí)現(xiàn)A/D轉(zhuǎn)換轉(zhuǎn)換V/F轉(zhuǎn)換器轉(zhuǎn)換器V計(jì)數(shù)器計(jì)數(shù)器DAVR 10位位A/D的特點(diǎn)的特點(diǎn) 10-b

2、it Resolution 2 LSB Accuracy 0.5 LSB Integral Non-Linearity 65 - 260 s Conversion Time Up to 15 kSPS 8 Multiplexed Input Channels Rail-to-Rail Input Range Free Run or Single Conversion Mode Interrupt on ADC Conversion Complete Sleep Mode Noise CancelerAVR A/D轉(zhuǎn)換器（轉(zhuǎn)換器（1）AVR A/D轉(zhuǎn)換器（轉(zhuǎn)換器（2）A/D轉(zhuǎn)換時(shí)鐘轉(zhuǎn)換時(shí)鐘A/D

3、轉(zhuǎn)換器參數(shù)轉(zhuǎn)換器參數(shù)8選選1寄存器寄存器ADMUX Bits 2.0 - MUX2.MUX0: Analog Channel Select Bits 2-0 選擇模擬通道選擇模擬通道0-7 PA0-PA7設(shè)置為高阻。設(shè)置為高阻。A/D控制及狀態(tài)寄存器控制及狀態(tài)寄存器Bit 7 - ADEN: ADC EnableBit 6 - ADSC: ADC Start ConversionBit 5 - ADFR: ADC Free Run SelectBit 4 -ADIF: ADC Interrupt FlagBit 3 - ADIE: ADC Interrupt EnableBits 2.0 -

4、ADPS2.ADPS0: ADC Prescaler Select BitsA/D噪聲消除功能噪聲消除功能 AVR A/D能在能在CPU空閑模式下，降低空閑模式下，降低CPU內(nèi)核產(chǎn)生的模擬噪聲。內(nèi)核產(chǎn)生的模擬噪聲。 按下列步驟操作：按下列步驟操作： ADEN = 1，ADSC = 0，ADFR = 0，ADIE = 1 CPU進(jìn)入空閑模式，進(jìn)入空閑模式，A/D轉(zhuǎn)換開始。轉(zhuǎn)換開始。 A/D轉(zhuǎn)換完成，轉(zhuǎn)換完成，CPU啟動(dòng)進(jìn)入啟動(dòng)進(jìn)入A/D中斷服務(wù)程序。中斷服務(wù)程序。模擬電源提供模擬電源提供實(shí)驗(yàn)板實(shí)驗(yàn)板A/D電路電路差分輸入電路差分輸入電路啟動(dòng)定時(shí)采樣啟動(dòng)定時(shí)采樣void StartAcquirin

5、g()DataCnt=0; memAddrLB=0; memAddrHB=0; memPage=0; WrPgReg();UCR=0 x18; /Disable UART interruptsTCCR0=0 x00; /Stop timer0TIMSK=0 x10; /Enable timer1s CompATCNT1H=0; TCNT1L=0;OCR1AH=Tm1HB; OCR1AL=Tm1LB;TCCR1B=0 x09; /Start timer1 with CTC1SPCR=0 x58; /SPI clk=fclk/4InAcquiringF=1; /End of StartAcquir

6、ing/ ADC initialization/ch0, 460.800 kHzADMUX=0; ADCSR=0 x84; ADCSR.6=1;定時(shí)中斷采集定時(shí)中斷采集interrupt TIM1_COMPA void timer1_compa_isr(void)Ad.Data=ADCW; /Get Last resultsADCSR.4=1; /Clear ADC interrupt flag DataCnt+;if (DataCnt=RecItemMax) InAcquiringF=0; AcquiringUpdatedF=1; /finished acquiringelse ADCSR.6=1; /Start conversion /End of timer1_ovf_isrstruct ByteDefunsign