Posted on December 18, 2013 at 17:59Hi,
I'm trying to read a 5kHz square wave dc=50%. I'm using thw pwm input capture.
The problem is that the program gives me a dc=100% and strange frequencies, but i cannot figure out why it happens.. can someone help me?
/******************main****************/
/* Init TIMER 1 */
CLK_PeripheralClockConfig(CLK_Peripheral_TIM1, ENABLE);
// configure TIM1 channel 1 to capture a PWM signal
TIM1_PWMIConfig(TIM1_Channel_2, TIM1_ICPolarity_Rising, TIM1_ICSelection_DirectTI,
TIM1_ICPSC_DIV1, TIM1_ICFilter);
// Select the TIM1 Input Trigger: TI1FP1
TIM1_SelectInputTrigger(TIM1_TRGSelection_TI1FP1);
TIM1_SelectSlaveMode(TIM1_SlaveMode_Reset);
// Enable CC1 interrupt request
TIM1_ITConfig(TIM1_IT_CC2, ENABLE);
// Enable TIM1
TIM1_Cmd(ENABLE);
enableInterrupts();
/**********interrupt
INTERRUPT_HANDLER(TIM1_CAP_IRQHandler, 24)
{
disableInterrupts();
/* Get the Input Capture value by reading CCR1 register */
/* CCR1 regsiter contains signal frequency value */
IC1Value = TIM1_GetCapture2();
if (IC1Value != 0)
{
/* Get the Input Capture value by reading CCR2 register */
/* CCR2 regsiter contains how much time the signal remained at high level */
IC2Value = TIM1_GetCapture2();
clock_frequency = CLK_GetClockFreq();
/* Duty cycle computation */
SignalDutyCycle = ((uint32_t) IC2Value * 100) / IC1Value;
/* Frequency computation */
SignalFrequency = (uint32_t) (CLK_GetClockFreq() / IC1Value);
if(SignalFrequency>4999){
GPIO_ToggleBits(GPIOE,GPIO_Pin_7);}
}
else
{
SignalDutyCycle = 0;
SignalFrequency = 0;
}
/* Clear TIM1 Capture compare interrupt pending bit */
TIM1_ClearITPendingBit(TIM1_IT_CC2);
TIM1_ClearFlag(TIM1_FLAG_CC1);
TIM1->CNTRH = 0;
TIM1->CNTRL = 0;
enableInterrupts();
}
One last question: what should be the correct value in the IC filter?
Thanks,
Gilberto
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