Resolved! A Mistake Found in HAL Library
Function "PWM Generation CH2N" can not work, channel CH2N don't output PWM signal. But after I changed "tmpccer &= ~TIM_CCER_CC2NE;" to "tmpccer |= TIM_CCER_CC2NE;" (in file stm32h7xx_hal_tim.c), it works well.Hoping developers of HAL library will fi...