ʾʹõԴ
TIM3 CH1     --   PB4
TIM3 CH2     --   PB5
TIM3 CH3     --   PC7
TIM3 CH4     --   PC8

ʾḶ́
1ϵʱӣPLL 48MHz
2TIM3ͨ1~4ֱΪPWM
3TIM3ĸ¼DMA䣻
5ѭִ²ʵָıռձȹܣ
   a磬¼ʱDMA Burst䣻
   bDMAʱg_src_bufferеݷֱ䵽CC1~CC4ĴС