STM32F3 - diffrence between PWM1 and PWM2
It is documented in the Reference Manual, at the register descriptions.


  TIMx capture/compare mode register 1 (TIMx_CCMR1)
  
  [...]
  
  0110: PWM mode 1 - In upcounting, channel 1 is active as long as TIMx_CNT&lt;TIMx_CCR1
  else inactive. In downcounting, channel 1 is inactive (OC1REF='0) as long as
  TIMx_CNT&gt;TIMx_CCR1 else active (OC1REF=1).
  
  0111: PWM mode 2 - In upcounting, channel 1 is inactive as long as
  TIMx_CNT&lt;TIMx_CCR1 else active. In downcounting, channel 1 is active as long as
  TIMx_CNT&gt;TIMx_CCR1 else inactive.


In other words, the output signal is inverted in mode 2.