说明：  STM8处理器，因项目需要8路PWM转DA通道输出，故写了模拟类型的PWM输出，频率由定时器统一调节，占空比可以独立调节与关断。
(STM8 processor, because the project needs to turn DA 8 PWM output channels, so write simulate the type of PWM output frequency is adjusted by the timer unity, the duty cycle can be adjusted independently and off.)