單片機ADC模塊-文檔資料

1、吉林大學通信工程學院吉林大學通信工程學院 10.3 A/D轉(zhuǎn)換模塊本節(jié)提要本節(jié)提要一、一、A/D轉(zhuǎn)換基礎(chǔ)知識轉(zhuǎn)換基礎(chǔ)知識二、二、ATD模塊簡介模塊簡介三、三、ATD模塊寄存器模塊寄存器四、四、ATD模塊編程范例模塊編程范例本節(jié)提要本節(jié)提要一、一、A/D轉(zhuǎn)換基礎(chǔ)知識轉(zhuǎn)換基礎(chǔ)知識二、二、ATD模塊簡介模塊簡介三、三、ATD模塊寄存器模塊寄存器四、四、ATD模塊編程范例模塊編程范例ADC概述n微控制器處理的是離散量 (數(shù)字量) ，而現(xiàn)實中往往是連續(xù)量 (模擬量)物理量如：溫度, 壓力,濕度以及速度等等n傳感器 將物理量轉(zhuǎn)換為電信號 (電壓, 電流)n需要模擬-數(shù)字轉(zhuǎn)換器將電信號轉(zhuǎn)換為數(shù)字量以供微控制

2、器處理基本概念 傳感器傳感器 控制器控制器執(zhí)行器執(zhí)行器ADC 工作原理n將輸入電壓與若干等間距的參考電壓進行比較n因此需要比較器比較器Uin Uref Uout=V+ 1Uin Uref Uout=0V 0UinUrefUout1位ADCADC 工作原理n3 個比較器可將電壓分成4 級 (以 2位來表示)Uref1Uref2Uref3Rank0Rank1Rank2Rank3Uref1Uref2Uref3Uout1Uout2Uout3Quiz1: For voltage in rank2, Uout1 = ? Uout2 = ? Uout3 = ?UmaxUminUinADC工作原理n2位ADC

3、UinUrefRRRRD0D1編碼器8位 ADC, 需要多少個比較器?ADC工作原理nFlash Converter ADC優(yōu)點: 速度極快缺點: 非常復(fù)雜n逐次逼近式A/D轉(zhuǎn)換器Uin逐次逼近寄存器D/A 轉(zhuǎn)換器結(jié)果UrefADC工作原理逐次逼近式轉(zhuǎn)換器轉(zhuǎn)換過程 ( 4位 )SA-ADC 完成一次轉(zhuǎn)換至少需要 n 個時鐘周期ADC工作原理n必須進行采樣保持以避免輸入電壓在轉(zhuǎn)換期間發(fā)生變化UinADC工作原理n 逐次逼近式轉(zhuǎn)換器（ SA-ADC ）非?？毂容^復(fù)雜n SA-ADC在單片機中較為常見單片機中常見典型為8-12位具有多個多路復(fù)用的模擬通道SA-ADC通道選擇寄存器ADC 參數(shù)n轉(zhuǎn)換位

4、數(shù)（Bits）分辨率 = 2-n (8bits = 0.39%)n轉(zhuǎn)換速度（Speed）由工作時鐘頻率和轉(zhuǎn)換位數(shù)確定n轉(zhuǎn)換范圍（Range）05V, 010V, -5V+5V. Etc.n轉(zhuǎn)換通道數(shù)（Channels）Distinguish the channel and converter本節(jié)提要本節(jié)提要一、一、A/D轉(zhuǎn)換基礎(chǔ)知識轉(zhuǎn)換基礎(chǔ)知識二、二、ATD模塊簡介模塊簡介三、三、ATD模塊寄存器模塊寄存器四、四、ATD模塊編程范例模塊編程范例 8/10/12位可選 轉(zhuǎn)換速度較高，10位精度，單次轉(zhuǎn)換時間為7usec 采樣時間可編程設(shè)置 多種轉(zhuǎn)換模式：數(shù)據(jù)對齊方式、單次/連續(xù)轉(zhuǎn)換、 轉(zhuǎn)換結(jié)果比

5、較 外觸發(fā)控制 轉(zhuǎn)換結(jié)束可產(chǎn)生中斷 可用于8個模擬輸入通道的模擬輸入多路轉(zhuǎn)換器. 模擬/數(shù)字輸入引腳復(fù)用 18 轉(zhuǎn)換序列長度. 多通道掃描S12單片機ADC特性2, 4, 8, 16 ClocksAlways2 Clocks轉(zhuǎn)換時間計算舉例: (假設(shè)A/D 時鐘為2MHz，10位精度 )轉(zhuǎn)換時間 = Initial Sample Time + Programmed Sample Time + Resolution Period = 2 + 2 + 10 = 14 A/D Clocks = 7uSecS12單片機ADC轉(zhuǎn)換時間S12單片機ADC模塊框圖ADC 引腳可用于數(shù)字輸入ADC 結(jié)果寄存器

6、模擬輸入通道參考電壓本節(jié)提要本節(jié)提要一、一、A/D轉(zhuǎn)換基礎(chǔ)知識轉(zhuǎn)換基礎(chǔ)知識二、二、ATD模塊簡介模塊簡介三、三、ATD模塊寄存器模塊寄存器四、四、ATD模塊編程范例模塊編程范例ATD 模塊寄存器n 共27個寄存器控制寄存器（ATDCTL0ATDCTL5，6個）狀態(tài)寄存器（ATDSTAT0ATDSTAT1，2個 ）比較使能寄存器（ATDCMPE， 1個）比較方式寄存器（ATDCMPHT ， 1個,）轉(zhuǎn)換輸入使能寄存器（ATDDIEN ， 1個）轉(zhuǎn)換結(jié)果寄存器（ATDDR0ATDDR15，16個）其中: 8位寄存器： ATDCTL0ATDCTL5, ATDSTAT0 16位寄存器：其余ATD Re

7、gisters 1/12ATD Control Register 0 (ATDCTL0)WRAP3-0 - Wrap Around Channel Select 0 = ReservedX = 多通道轉(zhuǎn)換模式 從ANx回繞到AN0 1x 15 僅在ATDCTL5的MULT=1時有效ATD Registers 2/12SRES1:0 - A/D Resolution SelectATD Control Register 1 (ATDCTL1)ETRIGSEL - External Trigger Source Select S12XS此位無效ETRIGCH3:0 - External Trigg

8、er Channel SelectSMP_DIS - Discharge Before Sampling Bit 0=No discharge 1 = discharge 注：寫ATDCTL1會終止當前轉(zhuǎn)換序列ATD Registers 3/12ATD Control Register 2 (ATDCTL2)AFFC - ATD Fast Flag Clear All0 = 向CCFn 標志位寫1則清零1 =讀ATD轉(zhuǎn)換結(jié)果寄存器則CCFn 標志位清零（當比較功能被禁止） 寫ATD轉(zhuǎn)換結(jié)果寄存器則CCFn 標志位清零（當比較功能被使能）ICLKSTP - Internal Clock in S

9、top Mode Bit0 = 停止模式下，停止當前轉(zhuǎn)換，退出停止模式后ATD轉(zhuǎn)換自動重新開始1 = 停止模式下，可繼續(xù)使用內(nèi)部時鐘進行ATD轉(zhuǎn)換ETRIGLE - External Trigger Level/Edge ControlETRIGP - External Trigger PolarityETRIGE - External Trigger Mode Enable0 = 禁止外部觸發(fā)信號1 = 使能外部觸發(fā)信號ASCIE- ATD Sequence Complete Interrupt Enable0 = 禁止ATD轉(zhuǎn)換序列結(jié)束中斷1 = 使能ATD轉(zhuǎn)換序列結(jié)束中斷ACMPIE -

10、 Internal Clock in Stop Mode Bit0 = 禁止比較中斷1 = 使能比較中斷注：寫ATDCTL2會終止當前轉(zhuǎn)換序列ATD Registers 4/12ATD Control Register 3 (ATDCTL3)DJM - Result Register Data Justification0=Left justified data in the result registers1=Right justified data in the result registersS8C, S4C,S2C, S1C - Conversion Sequence LengthFI

11、FO - Result Register FIFO Mode0=Conversion results are placed in the corresponding result register up to the selected sequence length.1=Conversion results are placed in consecutive result registers (wrap around at end).FRZ1:0 - Background Debug Freeze Enable注：寫ATDCTL3會終止當前轉(zhuǎn)換序列ATD Registers 5/12設(shè)置預(yù)分頻

12、因子時，0.25MHzAEDCLK 8.3MHzATD Control Register 4 (ATDCTL4)SMP2:0 - Sample Time SelectPRS4:0 - ATD Clock PrescalerDivide By 25-Bit Modulus Counter PrescalerPRS0-PRS4SYSTEM CLOCKA/D Clock采樣時間長，采樣點電平更準確的逼近外部信號電平注：寫ATDCTL4會終止當前轉(zhuǎn)換序列ATD啟動：啟動：寫ATDCTL5會終止當前轉(zhuǎn)換序列，并開始新一次轉(zhuǎn)換此后，若外部觸發(fā)信號每次滿足觸發(fā)條件都會開始一次ATD轉(zhuǎn)換 ATD Regist

13、ers 6/12ATD Control Register 5 (ATDCTL5)SC - Special Channel Conversion0=Special channel conversions disabled1=Special channel conversions enabledSCAN - Continuous Conversion Sequence Mode 0=Single conversion sequence1=Continuous conversion sequences (scan mode)MULT - Multi-Channel Sample 0=Sample o

14、nly one channel1=Sample across several channelsCD,CC,CB,CA - Analog Input Channel Select Code單通道，單次轉(zhuǎn)換單通道，單次轉(zhuǎn)換多通道，單次轉(zhuǎn)換多通道，單次轉(zhuǎn)換單通道，序列轉(zhuǎn)換模式單通道，序列轉(zhuǎn)換模式多通道，序列轉(zhuǎn)換模式多通道，序列轉(zhuǎn)換模式特殊通道測試模式特殊通道測試模式ADC 工作方式ATD Registers 7/12ATD Status Register 0 (ATDSTAT0)SCF - Sequence Complete Flag0=Conversion sequence not complet

15、ed1=Conversion sequence has completedETORF - External Trigger Overrun Flag0=No External trigger over run error has occurred1=External trigger over run error has occurredFIFOR- Result Register Over Run Flag0=No over run has occurred1=Overrun condition exists (result register has been written while as

16、sociated CCFx flag was still set)CC3:0 - Conversion Counter 當前轉(zhuǎn)換結(jié)果將寫入的結(jié)果寄存器編號 例如： CC3:0=0110， 轉(zhuǎn)換結(jié)果寫入第6個結(jié)果寄存器先入先出模式下，不被初始化，當計數(shù)到最大值回最小值非先入先出模式下，轉(zhuǎn)換開始和結(jié)束時被初始化為0兩種模式下終止ATD轉(zhuǎn)換或開始新ATD轉(zhuǎn)換均被清零ATD Registers 8/12ATD Compare Enable Register (ATDCMPE)CMPE15:0 - Compare Enable for Conversion Number n (n= 15, 14, 13

17、, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0) of a Sequence0=No automatic compare1= Automatic compare of results for conversion n of a sequence is enabled對一個序列中第n次ATD轉(zhuǎn)換結(jié)果進行比較，除CMPEn=1，還要完成如下設(shè)置：將比較閾值寫入ATDDRn寫ATDCPMHT的CMPHTn位選擇比較方法注：寫ATDCMPE會終止當前轉(zhuǎn)換序列ATD Registers 9/12ATD Status Register 2 (ATDSTAT2)CCF1

18、5:0 - Conversion Complete Flag n (n= 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)0=Conversion number n not completed or successfully compared1=If (CMPEn=0): Conversion number n has completed. Result is ready in ATDDRn. If (CMPEn=1): Compare for conversion result number n with compare value

19、in ATDDRn, using compare operator CMPGTn is true. (No result available in ATDDRn)出現(xiàn)以下任一情況，CCFn被清零：寫ATDCTL5當AFFC=0，向CCFn寫1當AFFC=1，且CMPEn=1，寫ATDDRnATD Registers 10/12ATD Input Enable Register (ATDDIEN)IEN15:0 - ATD Digital Input Enable on channel x (x= 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1

20、, 0)0=Disable digital input buffer to ANx pin1=Enable digital input buffer on ANx pin通用I/O口AD口與ATD模塊的模擬輸入引腳復(fù)用將某個模擬輸入引腳作為通用輸入引腳使用時，必須將對應(yīng)IEN位置位ATD Registers 11/12ATD Compare Higher Than Register (ATDCMPHT)CMPHT15:0 - Compare Operation Higher Than Enable for conversion number n (n= 15, 14, , 2, 1, 0) o

21、f a Sequence0= If result of conversion n is lower or same than compare value in ATDDRn, this is flagged in ATDSTAT21= If result of conversion n is higher than compare value in ATDDRn, this is flagged in ATDSTAT2注：寫ATDCMPHT會終止當前轉(zhuǎn)換序列ATD Registers 12/12- data formatATD Conversion Result Registers (ATDD

22、Rn)ATDDR0ATDDR15關(guān)閉比較操作時，ATD轉(zhuǎn)換結(jié)果寫入ATDDRn 要寫入的ATDDRn的編號由ATDSTAT0的CC3CC0轉(zhuǎn)換計數(shù)給出 轉(zhuǎn)換結(jié)果在ATDDRn中的放置位置與轉(zhuǎn)換精度和結(jié)果對齊方式有關(guān)使能比較功能時，ATD轉(zhuǎn)換結(jié)果和比較閾值都總是12位，與SRES1:0(ATDCTL1)無關(guān)DJM=0 左對齊DJM=1 右對齊轉(zhuǎn)換結(jié)果不放入結(jié)果寄存器，比較完成后丟失本節(jié)提要本節(jié)提要一、一、A/D轉(zhuǎn)換基礎(chǔ)知識轉(zhuǎn)換基礎(chǔ)知識二、二、ATD模塊簡介模塊簡介三、三、ATD模塊寄存器模塊寄存器四、四、ATD模塊編程范例模塊編程范例ATD模塊編程范例 ATD模塊編程方法 ATD模塊編程范例AT

23、D初始化：先寫除ATD0CTL5外的控制寄存器，再寫ATD0CTL5完成初始化，并啟動轉(zhuǎn)換；ATD結(jié)果讀?。和ㄟ^查詢ATD0STAT0中的SCF位或采用中斷方式，確定轉(zhuǎn)換完成，讀取相關(guān)結(jié)果寄存器取得ATD轉(zhuǎn)換結(jié)果。 任務(wù)：分別對特殊通道VRH、VRL和(VRH+VRL)/2進行 ATD轉(zhuǎn)換ATD模塊編程范例(續(xù)1)/*/ *S12X128 ATD模塊范例程序*/*#include /* common defines and macros */#include /SCI相關(guān)函數(shù)/SCI初始化函數(shù)void SCI_init(void);void SCISendChar(char c1);void

24、SCISendString(char * pc2);void SCISendHex(char c1);unsigned char dtoa(char c1);/ATD相關(guān)函數(shù)/ATD初始化函數(shù)void ATD_init(void) ;ATD模塊編程范例(續(xù)2)/*主程序*/void main(void) SCI_init();ATD_init();ATD0CTL5=0 x45; /單次轉(zhuǎn)換，單通道，選擇特殊通道VRLwhile(!(ATD0STAT0&0 x80); /查詢ATD是否完成SCISendString(VRL=);SCISendHex(ATD0DR0H);SCISendString(rn);ATD0CTL5=0 x44; /單次轉(zhuǎn)換，單通道，選擇特殊通道VRHwhile(!(ATD0STAT0&0 x80);/查詢A