官方的例程
/**
\brief configure the GPIO ports
\param[in] none
\param[out] none
\retval none
*/
void gpio_configuration(void)
{
rcu_periph_clock_enable(RCU_GPIOA);
rcu_periph_clock_enable(RCU_AF);
/*configure PA6 (TIMER2 CH0) as alternate function*/
gpio_init(GPIOA, GPIO_MODE_IN_FLOATING, GPIO_OSPEED_50MHZ, GPIO_PIN_6);
}
/**
\brief configure the nested vectored interrupt controller
\param[in] none
\param[out] none
\retval none
*/
void nvic_configuration(void)
{
nvic_priority_group_set(NVIC_PRIGROUP_PRE1_SUB3);
nvic_irq_enable(TIMER2_IRQn, 1, 1);
}
/**
\brief configure the TIMER peripheral
\param[in] none
\param[out] none
\retval none
*/
void timer_configuration(void)
{
/* TIMER2 configuration: input capture mode -------------------
the external signal is connected to TIMER2 CH0 pin (PA6)
the rising edge is used as active edge
the TIMER2 CH0CV is used to compute the frequency value
------------------------------------------------------------ */
timer_ic_parameter_struct timer_icinitpara;
timer_parameter_struct timer_initpara;
rcu_periph_clock_enable(RCU_TIMER2);
timer_deinit(TIMER2);
/* TIMER2 configuration */
timer_initpara.prescaler = 107;
timer_initpara.alignedmode = TIMER_COUNTER_EDGE;
timer_initpara.counterdirection = TIMER_COUNTER_UP;
timer_initpara.period = 65535;
timer_initpara.clockdivision = TIMER_CKDIV_DIV1;
timer_initpara.repetitioncounter = 0;
timer_init(TIMER2,&timer_initpara);
/* TIMER2 configuration */
/* TIMER2 CH0 input capture configuration */
timer_icinitpara.icpolarity = TIMER_IC_POLARITY_RISING; //上升沿觸發
timer_icinitpara.icselection = TIMER_IC_SELECTION_DIRECTTI;
timer_icinitpara.icprescaler = TIMER_IC_PSC_DIV1;
timer_icinitpara.icfilter = 0x0;
timer_input_capture_config(TIMER2,TIMER_CH_0,&timer_icinitpara);
/* auto-reload preload enable */
timer_auto_reload_shadow_enable(TIMER2);
/* clear channel 0 interrupt bit */
timer_interrupt_flag_clear(TIMER2,TIMER_INT_CH0);
/* channel 0 interrupt enable */
timer_interrupt_enable(TIMER2,TIMER_INT_CH0);
/* TIMER2 counter enable */
timer_enable(TIMER2);
}
/*!
\brief main function
\param[in] none
\param[out] none
\retval none
*/
int main(void)
{
gpio_configuration();
gd_eval_com_init(EVAL_COM1);
nvic_configuration();
timer_configuration();
while (1);
}
/**
* @brief This function handles TIMER2 interrupt request.
* @param None
* @retval None
*/
void TIMER2_IRQHandler(void)
{
if(SET == timer_interrupt_flag_get(TIMER2,TIMER_INT_CH0)){
/* clear channel 0 interrupt bit */
timer_interrupt_flag_clear(TIMER2,TIMER_INT_CH0);
if(0 == ccnumber){
/* read channel 0 capture value */
readvalue1 = timer_channel_capture_value_register_read(TIMER2,TIMER_CH_0);
ccnumber = 1;
}else if(1 == ccnumber){
/* read channel 0 capture value */
readvalue2 = timer_channel_capture_value_register_read(TIMER2,TIMER_CH_0);
if(readvalue2 > readvalue1){
count = (readvalue2 - readvalue1);
}else{
count = ((0xFFFF - readvalue1) + readvalue2);
}
fre = (float)1000000 / count;
printf("the value1 is %d,the value2 is %d\n",readvalue1,readvalue2);
printf("the count is %d\n",count);
printf("the frequence is %f\n",fre);
ccnumber = 0;
}
}
}
自己修改使用的
void ACSig_In_Capture_Init(void) //TIM2_CH0 AC_SIG-PB4
{
timer_ic_parameter_struct timer_icinitpara;
timer_parameter_struct timer_initpara;
rcu_periph_clock_enable(RCU_TIMER2);
rcu_periph_clock_enable(RCU_GPIOB);
rcu_periph_clock_enable(RCU_AF);
//重映射
gpio_pin_remap_config(GPIO_TIMER2_PARTIAL_REMAP, ENABLE);
gpio_init(GPIOB, GPIO_MODE_IN_FLOATING, GPIO_OSPEED_50MHZ, GPIO_PIN_4);
nvic_priority_group_set(NVIC_PRIGROUP_PRE1_SUB3);
nvic_irq_enable(TIMER2_IRQn, 1, 1);
/* TIMER2 configuration: input capture mode -------------------
the external signal is connected to TIMER2 CH0 pin (PB4)
the rising edge is used as active edge
the TIMER2 CH0CV is used to compute the frequency value
------------------------------------------------------------ */
timer_deinit(TIMER2);
/* TIMER2 configuration */
timer_initpara.prescaler = 215;
timer_initpara.alignedmode = TIMER_COUNTER_EDGE;
timer_initpara.counterdirection = TIMER_COUNTER_UP;
timer_initpara.period = 65535;
timer_initpara.clockdivision = TIMER_CKDIV_DIV1;
timer_initpara.repetitioncounter = 0;
timer_init(TIMER2,&timer_initpara);
/* TIMER2 configuration */
/* TIMER2 CH0 input capture configuration */
timer_icinitpara.icpolarity = TIMER_IC_POLARITY_FALLING; //下降沿
timer_icinitpara.icselection = TIMER_IC_SELECTION_DIRECTTI;
timer_icinitpara.icprescaler = TIMER_IC_PSC_DIV1;
timer_icinitpara.icfilter = 0x4; //使能濾波功能
timer_input_capture_config(TIMER2,TIMER_CH_0,&timer_icinitpara);
/* auto-reload preload enable */
timer_auto_reload_shadow_enable(TIMER2);
/* clear channel 0 interrupt bit */
timer_interrupt_flag_clear(TIMER2,TIMER_INT_CH0);
/* channel 0 interrupt enable */
timer_interrupt_enable(TIMER2,TIMER_INT_CH0);
/* TIMER2 counter enable */
timer_enable(TIMER2);
}
可以看到上面的例程使能了濾波功能，下面對濾波功能做一下介紹，并說明為什麼要用。
輸入捕獲1濾波器CH0CAPFLT[3:0]， 這個用來設定輸入采樣頻率和數字濾波器長度。 其中，fPCLK是定時器的輸入頻率（TIMxCLK） ，一般為 108Mhz，而 fDTS則是根據 TIMERx_CTL0 的 CKDIV[1:0]的設定來确定的，如果 CKD[1:0]設定為 00，那麼fDTS=fTIMER_CK=fPCLK。
N 值就是濾波長度，舉個簡單的例子：假設 CH0CAPFLT[3:0]=0011，并設定 IC1 映射到通道 1 上，且為上升沿觸發，那麼在捕獲到上升沿的時候，再以fPCLK的頻率，連續采樣到 8 次通道 1 的電平，如果都是高電平，則說明确實是一個有效的觸發，就會觸發輸入捕獲中斷（如果開啟了的話） 。這樣可以濾除那些高電平脈寬低于 8 個采樣周期的脈沖信号，進而達到濾波的效果。
此處我是用來采集下降沿信号，但是信号下降的比較慢。當我把濾波關掉，情況如下圖，藍色是采集信号，黃色是測試信号，進一次觸發中斷就翻轉一次黃色信号的電平。可以看到因為藍色信号下降太慢，在臨界處觸發了多次中斷。
當我把濾波打開後，定時器就會采集多次才會觸發，這樣就可以解決信号邊沿慢的問題了。