使用 STM32 HAL 定时器和调整 PWM 信号的占空比

Question

我使用STM32Cube初始化代码生成器生成了一个初始化的Timer函数。为了生成固定占空比的 PWM 信号，我在 Timer 初始化函数中添加了 HAL_TIM_Base_Start(&htim1); //Starts the TIM Base generation 和 HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_1)//Starts the PWM signal generation，如下所示。

/* Private variables ---------------------------------------------------------*/
int pulse_width=0;

/* TIM1 init function */
static void MX_TIM1_Init(void)
{

  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;
  TIM_OC_InitTypeDef sConfigOC;
  TIM_BreakDeadTimeConfigTypeDef sBreakDeadTimeConfig;

  htim1.Instance = TIM1;
  htim1.Init.Prescaler = 0;//we want a max frequency for timer, so we set prescaller to 0         
  //And our timer will have tick frequency
  htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim1.Init.Period = 1066;//max value for timer is 16bit = 65535, TIM_Period = timer_tick_frequency / PWM_frequency - 1  
  //In our case, for 15Khz PWM_frequency, set Period to TIM_Period = 16MHz / 15KHz - 1 = 1066
  htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim1.Init.RepetitionCounter = 0;
  if (HAL_TIM_Base_Init(&htim1) != HAL_OK)/* to use the Timer to generate a simple time base for TIM1 */
  {
    Error_Handler();
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;//the default clock is the internal clock from the APBx, using this function
  if (HAL_TIM_ConfigClockSource(&htim1, &sClockSourceConfig) != HAL_OK)//Initializes the TIM PWM Time Base according to the specified
//parameters in the TIM_HandleTypeDef and create the associated handle.
  {
    Error_Handler();
  }

  if (HAL_TIM_PWM_Init(&htim1) != HAL_OK)
  {
    Error_Handler();
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }

  //sConfig: TIM PWM configuration structure
  //set duty cycle: pulse_length = ((1066 + 1) * duty_cycle) / (100 - 1)
    sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = pulse_width;/* 50% duty cycle is 538, set to 0 initially*///
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCNPolarity = TIM_OCNPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  sConfigOC.OCIdleState = TIM_OCIDLESTATE_RESET;
  sConfigOC.OCNIdleState = TIM_OCNIDLESTATE_RESET;
  if (HAL_TIM_PWM_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    Error_Handler();
  }

  if (HAL_TIM_PWM_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_2) != HAL_OK)
  {
    Error_Handler();
  }

  sBreakDeadTimeConfig.OffStateRunMode = TIM_OSSR_ENABLE;
  sBreakDeadTimeConfig.OffStateIDLEMode = TIM_OSSI_ENABLE;
  sBreakDeadTimeConfig.LockLevel = TIM_LOCKLEVEL_1;
  sBreakDeadTimeConfig.DeadTime = 0;
  sBreakDeadTimeConfig.BreakState = TIM_BREAK_ENABLE;
  sBreakDeadTimeConfig.BreakPolarity = TIM_BREAKPOLARITY_HIGH;
  sBreakDeadTimeConfig.AutomaticOutput = TIM_AUTOMATICOUTPUT_ENABLE;
  if (HAL_TIMEx_ConfigBreakDeadTime(&htim1, &sBreakDeadTimeConfig) != HAL_OK)
  {
    Error_Handler();
  }

  HAL_TIM_MspPostInit(&htim1);//output pin assignment
    HAL_TIM_Base_Start(&htim1); //Starts the TIM Base generation
  if (HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_1) != HAL_OK)//Starts the PWM signal generation
  {
    /* PWM Generation Error */
    Error_Handler();
  }

  /* Start channel 2 */
  if (HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_2) != HAL_OK)
  {
    /* PWM Generation Error */
    Error_Handler();
  }

}

当我硬编码正确的值以替换sConfigOC.Pulse = pulse_width 中的pulse_width 值时，这足以以上述 cmets 中指定的固定占空比运行 PWM。 在另一个函数中，我有一个算法可以更新pulse_width 全局变量。该函数被调用：adjust_PWM();。该算法计算从 ADC 测量的值并存储为全局变量。该函数称为：Data_Update();。在main()，在所有函数都初始化之后。我没完没了地调用这三个函数

Data_Update();
adjust_PWM();   
MX_TIM1_Init(); 

我尝试过，并在示波器上获得了奇怪的波形，但这可能是因为 ADC 引脚浮动，导致浮动测量干扰算法的占空比。连续调用定时器的初始化也会中断 PWM 信号。有没有更好的方法在运行代码时更改占空比而不使用全局变量，或者每次我想更新占空比时都不初始化计时器。任何链接将不胜感激。

Answer 1

编写您自己的函数来更新控制占空比的寄存器。您必须手动更新相应的 CCRx 寄存器（x 是您正在使用的 PWM 通道，在您的情况下为 CCR1）。

ARR 寄存器是您在根据所需占空比计算 CCR 寄存器的新值时将引用的寄存器。

void adjust_PWM_DC(TIM_HandleTypeDef* const pwmHandle, const float DC)
{
    assert(pwmHandle != NULL);
    assert((DC >= 0.0F) && (DC <= 100.0F));

    /* The duty cycle value is a percentage of the reload register value (ARR). Rounding is used.*/
    uint32_t newRegVal = (uint32_t)roundf((float32_t)(pwmHandle->Instance->ARR) * (DC * 0.01F));

    /*In case of the DC being calculated as higher than the reload register, cap it to the reload register*/
    if(newRegVal > pwmHandle->Instance->ARR){
        newRegVal = pwmHandle->Instance->ARR);
    }

    /*Assign the new DC count to the capture compare register.*/
    pwmHandle->Instance->CCR1 = (uint32_t)(roundf(newRegVal));  /*Change CCR1 to appropriate channel, or pass it in with function.*/ 
}

Answer 2

当您想更改设置时不要重新初始化计时器，HAL 有一个专用宏用于此目的，称为：

/**
  * @brief  Sets the TIM Capture Compare Register value on runtime without
  *         calling another time ConfigChannel function.
  * @param  __HANDLE__: TIM handle.
  * @param  __CHANNEL__ : TIM Channels to be configured.
  *          This parameter can be one of the following values:
  *            @arg TIM_CHANNEL_1: TIM Channel 1 selected
  *            @arg TIM_CHANNEL_2: TIM Channel 2 selected
  *            @arg TIM_CHANNEL_3: TIM Channel 3 selected
  *            @arg TIM_CHANNEL_4: TIM Channel 4 selected
  * @param  __COMPARE__: specifies the Capture Compare register new value.
  * @retval None
  */
#define __HAL_TIM_SET_COMPARE(__HANDLE__, __CHANNEL__, __COMPARE__) \
(*(__IO uint32_t *)(&((__HANDLE__)->Instance->CCR1) + ((__CHANNEL__) >> 2)) = (__COMPARE__))

对于 Timer 1 - Channel 1 和 Timer 1 - Channel 2，它应该如下所示：

Data_Update();
adjust_PWM();

__HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_1, pulse_width);
__HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_2, pulse_width);