Unable to set two PWMs to a fixed phase difference

[gfxfloro]

Hi,

I am trying to set up two timers so that they generate a PWM with the second timer being 1/4 phase past the first one. I am using an STM32F446.

I have the second set up as slave and triggered by the OCREF2 of timer 1, this should then generate a reset of timer 2. Below is my timer init by cube mx and I'll also post the registers.

static void MX_TIM1_Init(void)
{
 
  /* USER CODE BEGIN TIM1_Init 0 */
 
  /* USER CODE END TIM1_Init 0 */
 
  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};
  TIM_OC_InitTypeDef sConfigOC = {0};
  TIM_BreakDeadTimeConfigTypeDef sBreakDeadTimeConfig = {0};
 
  /* USER CODE BEGIN TIM1_Init 1 */
 
  /* USER CODE END TIM1_Init 1 */
  htim1.Instance = TIM1;
  htim1.Init.Prescaler = 99;
  htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim1.Init.Period = 63999;
  htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim1.Init.RepetitionCounter = 0;
  htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_Base_Init(&htim1) != HAL_OK)
  {
    Error_Handler();
  }
  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim1, &sClockSourceConfig) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_TIM_PWM_Init(&htim1) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_TIM_OC_Init(&htim1) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_OC2REF;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = 31999;
  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();
  }
  __HAL_TIM_DISABLE_OCxPRELOAD(&htim1, TIM_CHANNEL_1);
  sConfigOC.OCMode = TIM_OCMODE_TOGGLE;
  sConfigOC.Pulse = 15999;
  if (HAL_TIM_OC_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_2) != HAL_OK)
  {
    Error_Handler();
  }
  sBreakDeadTimeConfig.OffStateRunMode = TIM_OSSR_DISABLE;
  sBreakDeadTimeConfig.OffStateIDLEMode = TIM_OSSI_DISABLE;
  sBreakDeadTimeConfig.LockLevel = TIM_LOCKLEVEL_OFF;
  sBreakDeadTimeConfig.DeadTime = 0;
  sBreakDeadTimeConfig.BreakState = TIM_BREAK_DISABLE;
  sBreakDeadTimeConfig.BreakPolarity = TIM_BREAKPOLARITY_HIGH;
  sBreakDeadTimeConfig.AutomaticOutput = TIM_AUTOMATICOUTPUT_DISABLE;
  if (HAL_TIMEx_ConfigBreakDeadTime(&htim1, &sBreakDeadTimeConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN TIM1_Init 2 */
 
  /* USER CODE END TIM1_Init 2 */
  HAL_TIM_MspPostInit(&htim1);
 
}
 
/**
  * @brief TIM3 Initialization Function
  * @param None
  * @retval None
  */
static void MX_TIM3_Init(void)
{
 
  /* USER CODE BEGIN TIM3_Init 0 */
 
  /* USER CODE END TIM3_Init 0 */
 
  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_SlaveConfigTypeDef sSlaveConfig = {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 = 99;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 63999;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  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();
  }
  sSlaveConfig.SlaveMode = TIM_SLAVEMODE_TRIGGER;
  sSlaveConfig.InputTrigger = TIM_TS_ITR0;
  if (HAL_TIM_SlaveConfigSynchro(&htim3, &sSlaveConfig) != 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 = 31999;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  if (HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_4) != HAL_OK)
  {
    Error_Handler();
  }
  __HAL_TIM_DISABLE_OCxPRELOAD(&htim3, TIM_CHANNEL_4);
  /* USER CODE BEGIN TIM3_Init 2 */
 
  /* USER CODE END TIM3_Init 2 */
  HAL_TIM_MspPostInit(&htim3);
 
}

The registers after initialization look as follows:

TIM1

TIM3

 

With this setup my signals are just in phase, with the second one just 40us behind, which you cannot see in this snap

[waclawek.jan]

You want them both to be set up completely, except for enabling the counter, i.e. you want both TIMx_CR.CEN=0. After that, enable only the master timer's counter.

I have no idea how to pull this out with Cube/HAL, I don't use it. It's way simpler to do it in registers.

JW

[gfxfloro]

I worded that badly, the registers look like that after starting the counters, before that they are completely set up. The timers are then started with a call to HAL_TIM_PWM_Start(...) which does exactly what you described (omitting the enable for the triggerd counter). Still the waveforms are in phase

[waclawek.jan]

> I worded that badly, the registers look like that after starting the counters, before that they are completely set up.

Show.

JW

[gfxfloro]

TIM1 after call to MX init

TIM3 after call to MX init

[gfxfloro]

Add-on question:

My goal after getting the timers working is to adjust the period on the fly:

Will something like this work or is it not recommended to set the register values while the counter is working?

adc_val = ADC1->DR;
 
if(adc_val > 0x7ff)
   {
       arr = (adc_val - 0x800) << 5;
       TIM1->ARR = arr;
       TIM2->ARR = arr;
       TIM1->CCR1 = arr / 2u;
       TIM1->CCR3 = arr / 4u;
       TIM2->CCR2 = arr / 2u;
   }else
   {
       arr = (0x800 - adc_val) << 5;
      TIM1->ARR = arr;
      TIM2->ARR = arr;
      TIM1->CCR1 = arr / 2u;
      TIM1->CCR3 = 3u * arr / 4u;
      TIM2->CCR2 = arr / 2u;
   }

[waclawek.jan · Accepted solution]

Try to use PWM mode rather than toggle in the channel which is set as TRGO from master.

You should set TIMx_CR1.ARPE (i.e. enable ARR preload) if you are going to change ARR on the fly.

JW

[gfxfloro]

I accidentally set active high instead of PWM which seems to work as well. Also it seems to be important to first call HAL_TIM_PWM_Start(...) for the slave timer, before the master timer