DSPF2812学习程序： 利用GP定时器4的比较器在产生PWM波，控制LCD背光亮度,系统时钟150M，高速外设时钟25M，128分频后定时器为5.12us,适于初学者学习-DSPF2812 learning process: the use of GP timer 4 comparison of PWM wave generating device to control the LCD backlight brightness, the system clock 150M, high-spe