说明：  STM32采用定时器管脚的输入捕获功能进行外部脉冲个数的采集，此代码仅采集脉冲个数，准确无误，用到的朋友下来看看，可检测编码器等PWM脉冲个数
(STM32 timer pin input capture function for the acquisition of the external pulse number, this code is only collected the number of pulses, accurate, friend came down to see used to detect the number of encoder and PWM pulse)