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根据上述原理图  从而写清

#include "counter.h"
#include "stdio.h"TIM_HandleTypeDef counter_handle ={0};
uint16_t new_count =0;
uint16_t old_count =0;void counter_init(uint16_t arr,uint16_t psc )
{TIM_SlaveConfigTypeDef slave_config ={0};counter_handle.Instance =TIM2;counter_handle.Init.Prescaler=psc;counter_handle.Init.Period =arr;counter_handle.Init.CounterMode = TIM_COUNTERMODE_UP;HAL_TIM_IC_Init(&counter_handle);slave_config.SlaveMode = TIM_SLAVEMODE_EXTERNAL1;    //选择外部时钟模式1slave_config.InputTrigger =TIM_TS_TI2FP2;            //选择通道2slave_config.TriggerFilter =TIM_TRIGGERPOLARITY_FALLING ;     //默认选择下降沿检测slave_config.TriggerPolarity =0;                            //滤波器为0HAL_TIM_SlaveConfigSynchro(&counter_handle,&slave_config);HAL_TIM_IC_Start(&counter_handle,TIM_CHANNEL_2);}void HAL_TIM_IC_MspInit(TIM_HandleTypeDef *htim)
{if(htim->Instance == TIM2){ //①定义初始化结构体GPIO_InitTypeDef gpio_initstruct;//打开时钟__HAL_RCC_GPIOA_CLK_ENABLE();   //注意看硬件原理图中LED灯的引脚在哪一个组__HAL_RCC_TIM2_CLK_ENABLE();    //开启定时器时钟//调用GPIO初始化函数gpio_initstruct.Pin = GPIO_PIN_0;                         //LED1、LED2对应的引脚gpio_initstruct.Pull = GPIO_MODE_AF_PP;                       //复用推挽输出gpio_initstruct.Mode =GPIO_MODE_OUTPUT_PP;                //上拉gpio_initstruct.Speed =GPIO_SPEED_FREQ_HIGH;              //高速HAL_GPIO_Init(GPIOA,&gpio_initstruct);}
}void count_get(void)
{new_count=__HAL_TIM_GET_COUNTER(&counter_handle);               if(old_count!=new_count)                                  //设置新老比较的原因是 __HAL_TIM_GET_COUNTER（）会把未按键的当前值一直在while中循环  使得持续输出{old_count =new_count;printf("CNT: %d\r\n",new_count);}
}

只需注意新老的值比较  这是因为避免未按键时一直循环   

最终结果