Posted on April 25, 2017 at 19:09Hello:
I'm using an STM32F4 to capture low frequency pulses below 50Hz. The source is sending exactly 20 pulses, with a DC of about 25%. The input pin to the STM32F4 confirms 20 pulses. However, the STM32F4 seems to capture only half of them -10. (i.e., I printf the T2_TIM2Freq value and see only 10 statements) If I set the source to burst 16 pulses, it captures (prints) 8. Here's the setup and the interrupt. Can someone see something that would cause this?
Thanks,
Gary
void TIM2configurationPA5(void)
{
NVIC_InitTypeDef NVIC_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
/* TIM2 Periph clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
/* TIM2 channel 1 pin (PA.5) configuration */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_High_Speed;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* Connect TIM pins to AF2 */
GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_TIM2);
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Prescaler = 0;
TIM_TimeBaseStructure.TIM_Period = (uint32_t)0xFFFFFFFF;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Down;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
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);
TIM_ICInitStructure.TIM_Channel = TIM_Channel_1;
TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising | 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 CC2 Interrupt Request */
TIM_ITConfig(TIM2, TIM_IT_CC1, ENABLE);
}
void TIM2_IRQHandler(void)
{
if(TIM_GetITStatus(TIM2, TIM_IT_CC1) == SET)
{
/* Clear TIM2 Capture compare interrupt pending bit */
TIM_ClearITPendingBit(TIM2, TIM_IT_CC1);
if(T2_captureNumber == 0)
{
T2_readValue1 = TIM_GetCapture1(TIM2);
T2_captureNumber = 1;
}
else if(T2_captureNumber == 1)
{
T2_readValue2 = TIM_GetCapture1(TIM2);
if (T2_readValue2 > T2_readValue1)
{
T2_uwCapture = (T2_readValue1 - T2_readValue2);
}
else if (T2_readValue2 < T2_readValue1)
{
T2_uwCapture = ((0xFFFFFFFF - T2_readValue2) + T2_readValue1);
}
else
{
T2_uwCapture = 0;
}
T2_TIM2Freq = (float32_t) (((SystemCoreClock / 2)/1.0) / (T2_uwCapture/1.0));
T2_captureNumber = 0;
}
}
}
