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

ʾḶ́
1ϵʱӣPLL 48MHz
2TIM3ΪPWMģʽ4ͨ;
3ͨ1εռձΪ50%
       ͨ2εռձΪ37.5%
       ͨ3εռձΪ25%
       ͨ4εռձΪ12.5%