5 RTT NANO 使用定时器外部计数时会丢失脉冲

发布于 2022-02-23 10:51:15 浏览：1093 订阅该版

用的定时器3的通道检测外部脉冲个数，每隔一秒读取一次CNT寄存器的值，标准库下脉冲数量正常，但是RTT里读取就会少一个脉冲
![QQ截图20220223104624.png](https://oss-club.rt-thread.org/uploads/20220223/5048ae3c7338180af469ee20547ac0d5.png)

上面打印的是标准库，下面打印的是RTT
RTT NANO 使用定时器ETR外部计数时会丢失脉冲

定时器代码：定时器3外部计数，定时器2产生脉冲
```c
#include "led.h"
#include "rtthread.h"

static int LED_Init(void)
{
	GPIO_InitTypeDef  GPIO_InitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;				
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; 		
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;		
	GPIO_Init(GPIOD, &GPIO_InitStructure);	  				
	GPIO_SetBits(GPIOD,GPIO_Pin_2); 	
	return 0;
}
INIT_BOARD_EXPORT(LED_Init);

static int bsp_timer3_init(void)
{
    TIM_TimeBaseInitTypeDef  	TIM_TimeBaseStructure;
    GPIO_InitTypeDef  			GPIO_InitStructure;
	
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
    TIM_TimeBaseStructure.TIM_Period = 65535;
    TIM_TimeBaseStructure.TIM_Prescaler = 0;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
	
	TIM_TIxExternalClockConfig(TIM3,TIM_TIxExternalCLK1Source_TI1,TIM_ICPolarity_Rising,0);
    TIM_SetCounter(TIM3, 0);
    TIM_Cmd(TIM3, ENABLE);
	return 0;
}
INIT_BOARD_EXPORT(bsp_timer3_init);

static int  bsp_timer2_init(void)
{

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    NVIC_InitTypeDef NVIC_InitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

TIM_TimeBaseStructure.TIM_Period = 100-1;
    TIM_TimeBaseStructure.TIM_Prescaler = 72-1;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE );

NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

TIM_SetCounter( TIM2, 0 );
    TIM_Cmd(TIM2, ENABLE);
	return 0;
}
INIT_BOARD_EXPORT(bsp_timer2_init);

void TIM2_IRQHandler(void)
{

if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
    {
		LED1=!LED1;
		LED1=!LED1;
    }

TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
}

```

主函数：
```c
rt_thread_t USART_tid;

static void USART_thread_entry(void* params)
{
    while(1)
    {
        rt_kprintf("Count=%d\r\n",TIM_GetCounter(TIM3));
		TIM_SetCounter(TIM3, 0);
        rt_thread_mdelay(1000);
    }
}

int USART_thread(void)
{
    USART_tid = rt_thread_create("USART", USART_thread_entry, RT_NULL, 256, 10, 5);

if(USART_tid != RT_NULL)
        rt_thread_startup(USART_tid);

return 0;
}

int main(void)
{	
	USART_thread();
}
```