Measure duration of the signal - c

Question

I have old programmable timer/ counter (PD71054 - count rate is set to 3Mhz), and now I would like to program a timer in STM32 (STM32F103RET6) to replace PD71054. I need to measure the duration of the square wave (PA0 pin), I found information about on of timer function - capture, but I do not know how to use it. And unfortunately I did't find good examples how to use it (SPL library). I tried to checking the edges of the signal. If a rising edge is detected, TIM5 will be started, if a falling edge is detected TIM5 will be stopped and the counted value will be saved. But I don’t know if this solution is good and how to set an interrupt for both edges of signal and have two different functions to handle for each of the slopes. signal example
int main(void)
{
TIM5_Config();
NVIC_Config ();
//IWDG_ReloadCounter();
RCC_Config();
RCC_APB1PeriphClockCmd(RCC_APB1PeriphClockCmd, ENABLE);
while(1){
}
}
RCC_Config()
{
BKP_DeInit();
// Reset RCC
RCC_DeInit ();
// HSI ON
RCC_HSICmd(ENABLE);
// Wait for HSI
while(RCC_GetFlagStatus(RCC_FLAG_HSIRDY) == RESET){};
FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
FLASH_SetLatency(FLASH_Latency_2);
RCC_HCLKConfig(RCC_SYSCLK_Div1);
RCC_PCLK2Config(RCC_HCLK_Div1);
RCC_PCLK1Config(RCC_HCLK_Div1);
RCC_HCLKConfig(RCC_SYSCLK_Div1);
RCC_SYSCLKConfig(RCC_SYSCLKSource_HSI);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
}
void IWDG_Config (void) {
// watchdoga IWGD
IWDG_WriteAccessCmd (IWDG_WriteAccess_Enable);
IWDG_SetPrescaler(IWDG_Prescaler_4); // 40kHz/4 = 10kHz
IWDG_SetReload(0x28A); // 65ms
IWDG_Enable(); // Start IWDG oraz LSI
}
void TIM5_IRQHandler(void)
{
TIM_Cmd(TIM5, ENABLE);
}
void TIM5_Config (void)
{
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM5, ENABLE);
// Ustawienia podstawy czasu TIM5
TIM_TimeBaseStructure.TIM_Period= 0xFFFF; //65535
TIM_TimeBaseStructure.TIM_Prescaler = 23; // fclk = 72MHz/24 =okolo 3MHz
TIM_TimeBaseStructure.TIM_ClockDivision = 1;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM5, &TIM_TimeBaseStructure);
// Zrodlo przerwania kanal 1
TIM_ITConfig(TIM5,TIM_IT_Update|TIM_IT_CC1,ENABLE);
TIM_Cmd(TIM5,ENABLE);
// TIM5_CH1, Rising edge, no filter
TIM_TIxExternalClockConfig(TIM5, TIM_TIxExternalCLK1Source_TI1, TIM_ICPolarity_Rising, 0x00);
TIM5_ICInitStructure.TIM_Channel=TIM_Channel_1;
TIM5_ICInitStructure.TIM_ICFilter=0;
TIM5_ICInitStructure.TIM_ICPolarity=TIM_ICPolarity_Rising;
TIM5_ICInitStructure.TIM_ICPrescaler=TIM_ICPSC_DIV1;
TIM5_ICInitStructure.TIM_ICSelection=TIM_ICSelection_DirectTI;
TIM_ICInit(TIM5, &TIM5_ICInitStructure);
}
void NVIC_Config (void)
{
NVIC_InitStructure.NVIC_IRQChannel=TIM5_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority= 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
}

Answer 1

Sorry I dont have time to go into details about TIMER capture methods.I can offer easer way to do this, at least you can try. Set PA0 pin as EXTI on rising, falling edges. So IRQ will be generated on rising and falling edges. Also setup TIM1 or TIM2 , basically 32bit timer with needed precision, just start timer and its counter. So at rising edge, you can easily reset timer TIM1->CNT = 0 it will be your start time when SIGNAL rise. And then when falling edge appear fetch TIM->CNT . Thats all. Just don't forget to control extra flags (own created variables) wich will help to separate rising and falling edges. Also you could even count those pulses in those events, but its not reliable way.
This is only a snippet, abstract, it should help to understand an idea.
void enable_timer(void){
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);
TIM_TimeBaseInitTypeDef timerInitStructure;
timerInitStructure.TIM_Prescaler = 48;
timerInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
timerInitStructure.TIM_Period = 0xFFFFFFFF; //32 bit timer , precision 1us
timerInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseInit(TIM1, &timerInitStructure);
TIM_Cmd(TIM1, ENABLE);
}
EXTI handler:
void EXTI0_1_IRQHandler (void)
{
if (EXTI_GetITStatus(EXTI_LINE0) != RESET){
EXTI_ClearITPendingBit(EXTI_LINE0); //clear the irq flag
if(rising_edge)
TIM1->CNT = 0;
if(falling_edge)
fetcher = TIM1->CNT; // here you get your pulse duration time in us
}
}