用TIM3定时器在PA6、PA7、PB0、PB1输出四种频率相同占空比分别是50 、37.5 、25 、12.5 的信号。 用TIM2的PWM_Input功能，从PA1口捕获PWM信号的频率及占空比，并用USART1输出测量信息。-At TIM3 timer with PA6, PA7, PB0, PB1 output frequency of the same four are 50 duty cycle, respectively, 37.5 , 25 , 12.5 of the

用寄存器直接配置STM32，里面有DA、AD、PWM、定时器-Register directly configure the STM32, which the DA, AD, PWM, timers, etc.

学习PWM必备，STM32定时器彻底研究-based general-purpose timer-STM32-based general-purpose timer