Posted on May 15, 2014 at 17:06 Hi, I am using uvision4 with stm32f1xx to meansure frequency counting the time of the falling edge pulse. I need a high precision to meansure frequency from 0Hz to 240Hz. The first thing that I do was to set the prescaler to mensure 240Hz. That is ok, the problem is that I cant get when the timer count overflow to mensure frequency from 61 to 0. The program enter in theTIM_IT_Update all the time, what am I doing wrong? void RCC_Configuration(void){
/* TIM2 clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE); TIM_TimeBaseStructure.TIM_Period = 65535; //20 mS
TIM_TimeBaseStructure.TIM_Prescaler = Prescaler_Pickup - 1; //1 uS 1 MHz
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
} void TIM2_IRQHandler (void) {
if(TIM_GetITStatus(TIM2, TIM_IT_CC1) == SET){
/* Clear TIM3 Capture compare interrupt pending bit */
TIM_ClearITPendingBit(TIM2, TIM_IT_CC1);
if(CaptureNumber == 0){
/* Get the Input Capture value */
IC3ReadValue1 = TIM_GetCapture1(TIM2);
CaptureNumber = 1;
estourou_timer = 0;
}
else if(CaptureNumber == 1){
/* Get the Input Capture value */
IC3ReadValue2 = TIM_GetCapture1(TIM2);
/* Capture computation */
if (IC3ReadValue2 > IC3ReadValue1){
Capture = (estourou_timer * 65535) + (IC3ReadValue2 - IC3ReadValue1);
}
else{
Capture = (estourou_timer * 65535) + ((0xFFFF - IC3ReadValue1) + IC3ReadValue2);
}
/* Frequency computation */
Pickup_1_FLOAT = (float) (72000000/Prescaler_Pickup) / Capture;
if(Pickup_1_FLOAT < Menor_Med) Menor_Med = Pickup_1_FLOAT;
CaptureNumber = 0;
}
}
if((TIM_GetITStatus(TIM2, TIM_IT_Update) == SET )){ //overflow
TIM_ClearITPendingBit(TIM2, TIM_FLAG_Update);
estourou_timer++;
}
} void TIM2_Configuration(){
TIM_ICInitStructure.TIM_Channel = TIM_Channel_1;
TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Falling;
TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
TIM_ICInitStructure.TIM_ICFilter = 0x0;
TIM_ICInit(TIM2, &TIM_ICInitStructure); /* TIM enable counter */
TIM_Cmd(TIM2, ENABLE);
/* Enable the CC1 Interrupt Request */
TIM_ITConfig(TIM2, TIM_IT_CC1 | TIM_IT_Update, ENABLE);
TIM_ICInit(TIM2, &TIM_ICInitStructure); /* TIM enable counter */
TIM_Cmd(TIM2, ENABLE); /* Enable the TIM3 global Interrupt */ NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQChannel; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); }
