STM32 generates out-of-phase square waves

I have been working on the past questions of the Blue Bridge Cup Embedded Development these days. In the mock test of the seventh final, there is a requirement that PA6 and PA7 generate two square waves with different phases and adjustable frequency. Later, I studied the Output comare mode of STM32.

Because I want to adjust the frequency, I choose the toggle mode to make the square wave out of phase. Just set it in the interrupt. First, the diagram in the manual

That's an old picture.

Let's take a look at the interrupt function in the OCToggle mode of the official StdLib3.5

void TIM1_BRK_TIM9_IRQHandler(void)

{

  /* TIM9_CH1 toggling with frequency = 366.2 Hz */

  if (TIM_GetITStatus(TIM9, TIM_IT_CC1) != RESET)

  {

    TIM_ClearITPendingBit(TIM9, TIM_IT_CC1 );

    capture = TIM_GetCapture1(TIM9);

    TIM_SetCompare1(TIM9, capture + CCR1Val );

  }

  /* TIM9_CH2 toggling with frequency = 732.4 Hz */

  if (TIM_GetITStatus(TIM9, TIM_IT_CC2) != RESET)

  {

    TIM_ClearITPendingBit(TIM9, TIM_IT_CC2);

    capture = TIM_GetCapture2(TIM9);

    TIM_SetCompare2(TIM9, capture + CCR2Val);

  }

}

OCToggle basically works like this:

If TIMx_CNT = TIM_CCR1, then the above interrupt will occur. In the interrupt, it will add the value of CCR1 to the CCR1Val value you set and assign it to CCR1. Each time an interrupt occurs, the level will be flipped (toggle)

Because the frequencies of the two channels are the same, the interruptions of the two channels should also occur close together. 

So in order to maintain the phase difference between the two channels, when channel 1 is interrupted, add the corresponding value based on your CCR2Val value and assign it to CCR2. This is equivalent to delaying the timing of channel 2 for a while when channel 1 is in the middle.

Like this

void TIM3_IRQHandler(void)

{

  if (TIM_GetITStatus(TIM3, TIM_IT_CC1) != RESET)

  {

    TIM_ClearITPendingBit(TIM3, TIM_IT_CC1 );

    capture = TIM_GetCapture1(TIM3);

    TIM_SetCompare1(TIM3, capture + CCR1Val );

TIM_SetCompare2(TIM3, capture +200);

  }

  if (TIM_GetITStatus(TIM3, TIM_IT_CC2) != RESET)

  {

    TIM_ClearITPendingBit(TIM3, TIM_IT_CC2);

    capture = TIM_GetCapture2(TIM3);

    TIM_SetCompare2(TIM3, capture + CCR2Val);

  }

}

I set CCR1Val and CCR2Val to 1000, and after adding 200, CH2 has a phase shift

The principle is that different initial values ​​can be assigned during initialization, so there is no need to open an interrupt for toggle