Need help to get PWM running with NUCLEO-H743ZI2 board

[Mick P. F.]

Hello,

I am trying to generate a PWM signal with the help of several guides from internet that ultimately contain the same thing, but it does not work, I'm doing something wrong, but I cannot see what. As a result, I only see a zero line in the display of a digital analyzer.

I have included the most important settings in the appendix below.

With the values for Prescaler = 2399 I would like to achieve a timer clock of 100 kHz and for Period = 1999 a PWM frequency of 50 Hz. However, it is not entirely clear to me what the change in Pulse does. Is it the duty cycle?

The code is very simple:

...
int main(void)
{
  /* USER CODE BEGIN 1 */
    uint32_t    br;
 
  /* USER CODE END 1 */
...
  MX_TIM3_Init();
...
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */
 
    /* USER CODE BEGIN 3 */
      br = 1000;
      pwm_setValue(br);
      HAL_Delay(100);
  }
  /* USER CODE END 3 */
}
...
static void MX_TIM3_Init(void)
{
 
  /* USER CODE BEGIN TIM3_Init 0 */
 
  /* USER CODE END TIM3_Init 0 */
 
  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};
  TIM_OC_InitTypeDef sConfigOC = {0};
 
  /* USER CODE BEGIN TIM3_Init 1 */
 
  /* USER CODE END TIM3_Init 1 */
  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 2399;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 1999;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
  if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
  {
    Error_Handler();
  }
  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_TIM_PWM_Init(&htim3) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = 0;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  if (HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_3) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN TIM3_Init 2 */
 
  /* USER CODE END TIM3_Init 2 */
  HAL_TIM_MspPostInit(&htim3);
 
}
...
/* USER CODE BEGIN 4 */
void pwm_setValue(uint32_t br)
{
    TIM_OC_InitTypeDef sConfigOC;
 
    bzero(&sConfigOC, sizeof(TIM_OC_InitTypeDef));
    sConfigOC.OCMode = TIM_OCMODE_PWM1;
    sConfigOC.Pulse = br;
    sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
    sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
    if (HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_3) == HAL_OK)
        HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_3);
}
 
/* USER CODE END 4 */

Can someone help me get PWM working? Where is my mistake?

Thanks in Advance,

Michael

[DavidAlfa · Accepted solution]

First, try setting the pulse fom the beginning (In the init function).

Then run PWM_START and do nothing else. No updating, no changes.

That should work.

No need to run again HAL_TIM_PWM_ConfigChannel and HAL_TIM_PWM_Start.

If you already started PWM, just update the CCRx value:

__HAL_TIM_SET_COMPARE(&htim3, TIM_CHANNEL_3, br);

If you want to update the timer period:

__HAL_TIM_SET_AUTORELOAD(&htim3,period);

Also, ensure that the PWM output is CHx type, not CHxN.

If its's CHxN then the PWM should be started with:

HAL_TIMEx_PWMN_Start(&htim3, TIM_CHANNEL_3);

[Mick P. F.]

Hello David,

Many thanks for your help, it works now!