ʾʹõԴ
TIM3 CH1     --   PA5
TIM3 CH2     --   PA4
TIM3 CH3     --   PA3
TIM3 CH4     --   PB4

ʾḶ́
1ϵʱӣRCH 48MHz
2TIM3ΪPWMģʽ4ͨΪģʽ1Ϊ8bit;
3ͨ1εռձΪ50%
       ͨ2εռձΪ37.5%
       ͨ3εռձΪ25%
       ͨ4εռձΪ12.5%