3. 数据手册中有写 AFR0和AFR1不能同时使用，但他们的IO并不冲突呀？而且我目前就这样用了，而且调试正常。
但刚才翻资料看到这句就懵了。

AFR1 Alternate function remapping option 1 (2)
0: AFR1 remapping option inactive: default alternate function(1)
1: Port A3 alternate function = SPI_NSS; port D2 alternate function =TIM2_CH3.

AFR0 Alternate function remapping option 0(2)
0: AFR0 remapping option inactive: Default alternate functions(1)
1: Port C5 alternate function = TIM2_CH1; port C6 alternate function =TIM1_CH1; port C7 alternate function = TIM1_CH2.

1. Refer to the pinout description.
2. Do not use more than one remapping option in the same port. It is forbidden to enable both AFR1 and
AFR0.

这个暂时还没得到答案！为保险起见，决定不使能AFR1，还是修改电路，把 PD2 [TIM2_CH3] 还是换成PA3 TIM2_CH3。