说明：  自己编的基于2812的交流电机SPWM开环调速 以下代码为SPWM开环控制的核心代码，在50HZ交流异步电机调试通过。
(Its own series of 2812 of the AC motor SPWM-based open-loop speed control the following code to the open-loop SPWM control for the core code, 50HZ AC induction motor to debug through.)