STM32採集頻率低頻用捕獲精度很高,測量高頻誤差有點大,可能是這種方法我掌握的不夠好,決定採用外部計數的方法來測量比較高的頻率。用一個定時器定時,另一個定時器計數再根據f=n/t算出頻率,這種方法原理上是定時時間越長求出的頻率越高,但是STM32的定時器是16位的,要考慮到計時溢出的情況。關於誤差的產生,測量的信號源的精度也是關鍵,在進入中斷的時候,定時器獲取計數值都會延時幾個微秒,可能會丟失脈衝。我現在這種測量方法測量100K-130k誤差大概8-10hz左右。下圖為通用定時器框圖:
先從main函數開始介紹:
int main(void)
{
int i;
SystemInit();
COMInit(COM2, 115200);
RCC_Configuration(); /* System Clocks Configuration*/
GPIO_Configuration(); /* Configure the GPIO ports */
Time_Configuration(); /* Time configuration */
Tim2_Timer();
while(1)
{
//Delayms(10);
for(i=0;i<1000000;i++)
{
}
}
}
下面是時鐘配置函數:
/*******************************************************************************
* Function Name : RCC_Configuration
* Description : System Clocks Configuration
* Input : None
* Output : None
* Return : None
*******************************************************************************/
void RCC_Configuration(void)
{
/* TIM2 clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
/* TIM3 clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE);
#if 0
/* TIM4 clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOE, ENABLE);
#endif
}
I/O配置函數:
/********************************************************************************
* Function Name : GPIO_Configuration
* Description : The I/O configuration function
* Input : None
* Output : None
* Return : None
*******************************************************************************/
void GPIO_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOD, &GPIO_InitStructure);
#if 0
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOE, &GPIO_InitStructure);
#endif
}
定時器初始化函數:
/********************************************************************************
* Function Name : Time_Configuration
* Description : 定時器3配置函數
* Input : None
* Output : None
* Return : None
*******************************************************************************/
void Time_Configuration()
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_TimeBaseStructure.TIM_Prescaler = 0x00;
TIM_TimeBaseStructure.TIM_Period = 0xFFFF;
TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); // Time base configuration
TIM_ETRClockMode2Config(TIM3, TIM_ExtTRGPSC_OFF, TIM_ExtTRGPolarity_NonInverted, 0);
//TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE);
TIM_SetCounter(TIM3, 0);
TIM_Cmd(TIM3, ENABLE);
}
定時器定時函數定時250ms
void Tim2_Timer(void)
{
TIM_TimeBaseInitTypeDef TIM2_TimeBaseStructure;
NVIC_InitTypeDef NVIC_InitStructure;
TIM_DeInit(TIM2);
TIM2_TimeBaseStructure.TIM_Period =2499;
TIM2_TimeBaseStructure.TIM_Prescaler = (7200-1);
TIM2_TimeBaseStructure.TIM_ClockDivision = 0x0;
TIM2_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM2, &TIM2_TimeBaseStructure); // Time base configuration
TIM_ClearFlag(TIM2,TIM_FLAG_Update);
TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE );
TIM_Cmd(TIM2, ENABLE);
NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
}
中斷服務函數:
#if 1
void TIM2_IRQHandler(void)
{
if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
{
TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
CAPTURE1=(u32)TIM_GetCounter(TIM3);
//CAPTURE2=(u32)TIM_GetCounter(TIM4);
}
sum+=CAPTURE1;
count++;
if(count==4)
{
Frequency1=sum/4/0.25;
sum=0;
count=0;
}
TIM_SetCounter(TIM3,0);
}
#endif
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關鍵字: TimeBaseStructure InitStructure ENABLE