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輸入捕捉模式和PWM輸入模式的區(qū)別
Stm32的通用定時(shí)器具備基本的輸入捕捉功能。所謂輸入捕捉功能，是指通用定時(shí)器可以通過檢測(cè)輸入信號(hào)的跳變沿，檢測(cè)到跳變沿的同時(shí)將計(jì)數(shù)器的當(dāng)前值寫入相應(yīng)的寄存器。我們可以利用定制器的輸入捕捉模式可以測(cè)量輸入信號(hào)的高電平時(shí)間、占空比和頻率。
1、輸入捕捉模式
Stm32的通用TIM2、3、4、5 都具有輸入捕捉的功能，每個(gè)定時(shí)器具有四個(gè)通道，并且每一個(gè)通道都可以單獨(dú)配置為輸入捕捉模式，主要用于測(cè)量輸入信號(hào)的高電平時(shí)間，也可測(cè)量信號(hào)的頻率（可能不太精確，尤其對(duì)于頻率很高的信號(hào)），如果用于測(cè)量信號(hào)的高電平時(shí)間，配置時(shí)需要注意定時(shí)器的時(shí)基頻率，下面的程序中有所說明。
下面是具體的程序，配置TIM2的四個(gè)通道為基本輸入捕捉模式，定時(shí)器的時(shí)基頻率為1M，用于測(cè)量輸入信號(hào)的高電平時(shí)間。
void TIM_Configuration(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
TIM_TimeBaseStructure.TIM_Period =0xFFFF;
TIM_TimeBaseStructure.TIM_Prescaler = 0;
TIM_TimeBaseStructure.TIM_ClockDivision =0;
TIM_TimeBaseStructure.TIM_CounterMode =TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM2 ,&TIM_TimeBaseStructure);
TIM_PrescalerConfig(TIM2 , 71 ,TIM_PSCReloadMode_Immediate); //即Ft=72M/72=1M
TIM2->CCMR1 &=(u16)0x0000; //清零
TIM2->CCMR1 |=(u16)0x0101; //TIM輸入2與IC2相連1與IC1相連
TIM2->CCMR2 &=(u16)0x0000; //清零
TIM2->CCMR2 |=(u16)0x0101; //TIM輸入3與IC3相連 4與IC4相連
TIM2->CCER = (u16)0x1111; //上升沿捕捉 捕捉使能
//開啟 CC中斷
//使能 Time
TIM2->DIER =(u16)0x001E; //TIM_IT_CC1 TIM_IT_CC2 TIM_IT_CC3 TIM_IT_CC4
//TIM2->DIER = (u16)0x0002;
TIM2->CR1 =((u16)0x0001); //CR1_CEN_Set
u16 IC_Dat[9] = {0,0,0,0,0,0,0,0,0};
u16 CaptureNumber1 = 0,CaptureNumber2 = 0,CaptureNumber3 =0,CaptureNumber4 = 0;
vu32 Capture1 = 0,Capture2 = 0,Capture3 = 0,Capture4 = 0;
void TIM2_IRQHandler(void)
{
if(TIM_GetITStatus(TIM2, TIM_IT_CC1) == SET) //判斷CH1是否出現(xiàn)跳變沿
{
if(CaptureNumber1 ==0) //出現(xiàn)上升沿
{
IC_Dat[1] =TIM_GetCapture1(TIM2); //得到CH1捕捉值1
CaptureNumber1 = 1;
TIM2->CCER &=(u16)0xFFFD; //改變跳變沿
TIM2->CCER |= (u16)0x0002;
}
elseif(CaptureNumber1 ==1) //出現(xiàn)下降沿
{
IC_Dat[2] = TIM_GetCapture1(TIM2); //得到CH1捕捉值2
TIM2->CCER &=(u16)0xFFFD; //改變跳變沿
TIM2->CCER |= (u16)0x0000;
if (IC_Dat[2] > IC_Dat[1])
{
Capture1 = (IC_Dat[2] - IC_Dat[1]);
}
else
{
Capture1 = ((0xFFFF - IC_Dat[1]) + IC_Dat[2]);
}
CaptureNumber1 = 0;
//printf("\r\n TheIC12 of input pulse is %d \r\n" ,IC_Dat[2]);
//printf("\r\n TheIC11 of input pulse is %d \r\n" ,IC_Dat[1]);
printf("\r\n TheCapture1 of input pulse is %d \r\n" ,Capture1);
}
TIM_ClearITPendingBit(TIM2, TIM_IT_CC1);
}
else if(TIM_GetITStatus(TIM2, TIM_IT_CC2) ==SET) //判斷CH2是否出現(xiàn)跳變沿
{
if(CaptureNumber2 ==0) //出現(xiàn)上升沿
{
IC_Dat[3] =TIM_GetCapture2(TIM2); //得到CH2捕捉值1
CaptureNumber2 = 1;
TIM2->CCER &=(u16)0xFFDF; //改變跳變沿
TIM2->CCER |= (u16)0x0020;
}
elseif(CaptureNumber2 ==1) //出現(xiàn)下降沿
{
IC_Dat[4] = TIM_GetCapture2(TIM2); //得到CH2捕捉值2
TIM2->CCER &=(u16)0xFFDF; //改變跳變沿
TIM2->CCER |= (u16)0x0000;
if (IC_Dat[4] > IC_Dat[3])
{
Capture2 = (IC_Dat[4] - IC_Dat[3]);
}
else
{
Capture2 = ((0xFFFF - IC_Dat[3]) + IC_Dat[4]);
}
CaptureNumber2 = 0;
//printf("\r\n TheIC22 of input pulse is %d \r\n" ,IC_Dat[4]);
// printf("\r\n The IC21 ofinput pulse is %d \r\n" , IC_Dat[3]);
printf("\r\n TheCapture2 of input pulse is %d \r\n" ,Capture2);
}
TIM_ClearITPendingBit(TIM2, TIM_IT_CC2);
}
else if(TIM_GetITStatus(TIM2, TIM_IT_CC3) ==SET) //判斷CH3是否出現(xiàn)跳變沿
{
if(CaptureNumber3 ==0) //出現(xiàn)上升沿
{
IC_Dat[5] =TIM_GetCapture3(TIM2); //得到CH3捕捉值1
CaptureNumber3 = 1;
TIM2->CCER &=(u16)0xFDFF; //改變跳變沿
TIM2->CCER |= (u16)0x0200;
}
elseif(CaptureNumber3 ==1) //出現(xiàn)下降沿
{
IC_Dat[6] = TIM_GetCapture3(TIM2); //得到CH3捕捉值2
TIM2->CCER &=(u16)0xFDFF; //改變跳變沿
TIM2->CCER |= (u16)0x0000;
if (IC_Dat[6] > IC_Dat[5])
{
Capture3 = (IC_Dat[6] - IC_Dat[5]);
}
else
{
Capture3 = ((0xFFFF - IC_Dat[5]) + IC_Dat[6]);
}
CaptureNumber3 = 0;
//printf("\r\n TheIC32 of input pulse is %d \r\n" ,IC_Dat[6]);
//printf("\r\n TheIC31 of input pulse is %d \r\n" ,IC_Dat[5]);
printf("\r\n TheCapture3 of input pulse is %d \r\n" ,Capture3);
}
TIM_ClearITPendingBit(TIM2, TIM_IT_CC3);
}
else if(TIM_GetITStatus(TIM2, TIM_IT_CC4) ==SET) //判斷CH3是否出現(xiàn)跳變沿
{
if(CaptureNumber4 ==0) //出現(xiàn)上升沿
{
IC_Dat[7] =TIM_GetCapture4(TIM2); //得到CH3捕捉值1
CaptureNumber4 = 1;
TIM2->CCER &=(u16)0xDFFF; //改變跳變沿
TIM2->CCER |= (u16)0x2000;
}
elseif(CaptureNumber4 ==1) //出現(xiàn)下降沿
{
IC_Dat[8] = TIM_GetCapture4(TIM2); //得到CH3捕捉值2
TIM2->CCER &=(u16)0xDFFF; //改變跳變沿
TIM2->CCER |= (u16)0x0000;
if (IC_Dat[8] > IC_Dat[7])
{
Capture4 = (IC_Dat[8] - IC_Dat[7]);
}
else
{
Capture4 = ((0xFFFF - IC_Dat[7]) + IC_Dat[8]);
}
CaptureNumber4 = 0;
// printf("\r\n The IC42 ofinput pulse is %d \r\n" , IC_Dat[8]);
// printf("\r\n The IC41 ofinput pulse is %d \r\n" , IC_Dat[6]);
printf("\r\n TheCapture4 of input pulse is %d \r\n" ,Capture4);
}
TIM_ClearITPendingBit(TIM2, TIM_IT_CC4);
}
}
需要注意的問題：
定時(shí)器的時(shí)基頻率不能太高，如果定時(shí)器工作于36M，采集50Hz的信號(hào)就會(huì)出現(xiàn)偏差（實(shí)測(cè)），所以程序中將定時(shí)器的時(shí)基頻率配置為了1M；
如果存在兩個(gè)以上中斷，需要設(shè)置中斷優(yōu)先級(jí)，否則容易出問題。
2、PWM輸入模式
PWM輸入模式是輸入捕捉模式的高級(jí)應(yīng)用，對(duì)于測(cè)量頻率較高的輸入信號(hào)的頻率特別精確，當(dāng)然，為了實(shí)現(xiàn)這個(gè)模式，也得做出一點(diǎn)犧牲。相比于基本輸入捕捉功能的實(shí)現(xiàn)來說，PWM輸入模式中，一路輸入信號(hào)同時(shí)映射到兩個(gè)引腳，而且只有第一和第二通道可以配置為這種模式，換句話說，每個(gè)通用定時(shí)器只能測(cè)量一路輸入信號(hào)，具體配置過程，詳見程序說明。
下面是TIM2的第二通道工作于PWM輸入捕捉模式時(shí)的模塊配置程序：
void TIM_Configuration(void)
{
TIM_ICInitTypeDef TIM_ICInitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
TIM_ICInitStructure.TIM_Channel =TIM_Channel_2;
TIM_ICInitStructure.TIM_ICPolarity =TIM_ICPolarity_Rising;
TIM_ICInitStructure.TIM_ICSelection =TIM_ICSelection_DirectTI;
TIM_ICInitStructure.TIM_ICPrescaler =TIM_ICPSC_DIV1;
TIM_ICInitStructure.TIM_ICFilter =0x00;
TIM_PWMIConfig(TIM2,&TIM_ICInitStructure);
TIM_SelectInputTrigger(TIM2,TIM_TS_TI2FP2);
TIM_SelectSlaveMode(TIM2,TIM_SlaveMode_Reset);
TIM_SelectMasterSlaveMode(TIM2,TIM_MasterSlaveMode_Enable);
TIM_ITConfig(TIM2, TIM_IT_CC2, ENABLE);
TIM_Cmd(TIM2, ENABLE);
voidTIM2_IRQHandler(void)
{
static float IC2Value =0;
static float DutyCycle =0;
static float Frequency =0;
static float Paulse = 0;
IC2Value = TIM_GetCapture2(TIM2);
Paulse = TIM_GetCapture1(TIM2);
DutyCycle = Paulse /IC2Value;
Frequency = 72000000 / IC2Value;
printf("\r\n The DutyCycle ofinput pulse is %%%d \r\n" , (u32)(DutyCycle * 100));
printf("\r\n The Frequency ofinput pulse is %.2fKHz\r\n" , (Frequency / 1000));
TIM_ClearITPendingBit(TIM2, TIM_IT_CC2);
}
關(guān)于PWM輸入模式工作過程的詳細(xì)說明：（打字麻煩，所以直接截圖過來）
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