STM32 PWM 可变脉宽控制的疑问？

只看该作者 · 2020-8-3 13:28

看了规格书，STM32的PWM的CCRx值在TIM_IT_Update中断发生时，从CCRx影子寄存器读取到真实寄存器。
现在的疑问是，比如TIM2CH1需要连续两个脉冲输出（CCR值分别为20，50），首次初始化时如果设定好CCR1=20，然后TIM_Cmd(TIM2, ENABLE);
此时，初始化时的CCR1值20已经读取到真实寄存器并生效执行，但是，我应该在哪里设置CCR1的第二次值50呢？如果在计时器溢出中断 TIM_IT_Update 中更新，岂不来不及？因为中断发生后，已经开始执行下次循环？

只看该作者 · 2020-8-3 20:04

直接用GPIO去翻转更方便吧

只看该作者 · 2020-8-3 20:18

本帖最后由 ipman 于 2020-8-3 20:26 编辑

我把要发送的10组PWM周期和占空比放到数组里面，然后再计数器更新中断里读取下一组赋值，很奇怪，第一组脉冲丢失了！！！
uint16_t pwmOutWave[10][2] = {{100,10}, {100,30},{100,30},{100,40},{100,40},{100,50},{100,50},{100,60},{100,60},{100,80}};
uint16_t SendIndex = 0;
void Tim16_Config(uint16_t period, uint16_t pulse)
{
      TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
      TIM_OCInitTypeDef  TIM_OCInitStructure;
      TIM_DeInit(TIM16);
      RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM16,ENABLE);
      TIM_ARRPreloadConfig(TIM16, DISABLE);
      TIM_TimeBaseStructure.TIM_Prescaler = 48-1;             //1us per count
      TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
      TIM_TimeBaseStructure.TIM_Period = period;
      TIM_TimeBaseStructure.TIM_ClockDivision = 0;
      TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
      TIM_TimeBaseInit(TIM16, &TIM_TimeBaseStructure);

      TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
      TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
      TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Disable;
      TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
      TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_Low;
      TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
      TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Set;
      TIM_OCInitStructure.TIM_Pulse =  pulse;
      TIM_OC1Init(TIM16, &TIM_OCInitStructure);
      TIM_OC1PreloadConfig(TIM16, TIM_OCPreload_Disable);
      //TIM_ARRPreloadConfig(TIM16, ENABLE);// DISABLE立即更新  ENABLE 影子
      TIM_CtrlPWMOutputs(TIM16, ENABLE);
      TIM_Cmd(TIM16, ENABLE);
      TIM_ITConfig(TIM16,TIM_IT_Update|TIM_IT_CC1, ENABLE);
}
void TIM16_IRQHandler(void)
{
      //匹配时
      if(TIM_GetITStatus(TIM16, TIM_IT_CC1) != RESET)
      {
            TIM_ClearITPendingBit (TIM16, TIM_IT_CC1);       //必须要清除中断标志位
      }
   //溢出时更新计数和匹配
      if (TIM_GetITStatus(TIM16, TIM_IT_Update) != RESET)       //TIM_IT_Update
      {
            if(SendIndex<9)
            {
                     SendIndex++; // 数组0在初始化时候已经执行
                     //重新赋值影子寄存器
                     TIM_SetAutoreload(TIM16, pwmOutWave[SendIndex][0]);
                     TIM_SetCompare1(TIM16, pwmOutWave[SendIndex][1]);

            }else{
                     //发送完成10组，关闭
                     TIM_Cmd(TIM16, DISABLE);
                     //确保输出电平为空闲设置
                     TIM_ForcedOC1Config(TIM16, TIM_ForcedAction_InActive);
            }
            TIM_ClearITPendingBit (TIM16, TIM_IT_Update);       //必须要清除中断标志位
      }

void testSend(void)
{
   SendIndex = 0;
   Tim16_Config(pwmOutWave[SendIndex][0],pwmOutWave[SendIndex][1]);
}