TIM2 freeze on ARR register value changed STM32H743ZI2

[Ilya Suvorov]

Hi. I'm working on project where I need short pulses with precise periods generated in audio ranges (10 - 20kHz). So I decided to choose TIM2 and using it in PWM mode. I'm using HAL library and configuration code generated by CubeMX:

void MX_TIM2_Init(void)
{
  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};
  TIM_OC_InitTypeDef sConfigOC = {0};
 
  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 2;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 24000;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
  {
    Error_Handler();
  }
  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_TIM_PWM_Init(&htim2) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = 150;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  if (HAL_TIM_PWM_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    Error_Handler();
  }
  HAL_TIM_MspPostInit(&htim2);
 
}

The ARR is changing by TIM4 interrupt which is configured in encoder mode

void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *htim) {
	if (htim->Instance == TIM4) {
	        long value = 24000 + TIM4->CNT * 8;
		TIM2->ARR = value;
	}
}

So. The freeze occurs when I quickly decreasing TIM4->CNT it takes about 50 seconds after that it starts operating. And it never happened on increasing. For quick test I used this code:

int click = 0;
 
int main(void) {
  HAL_Init();
 
  SystemClock_Config();
  
  MX_GPIO_Init();
  MX_TIM2_Init();
  MX_TIM4_Init();
 
  HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_1);
  HAL_TIM_Encoder_Start_IT(&htim4, htim4.Channel);
  
  while (1) {
	HAL_Delay(2000);
	click++;
	if (click % 2 == 0) {
		TIM2->ARR = 548280;
	} else {
		TIM2->ARR = 24000;
	}
  }
}

Could you explain me why is it happens and maybe could point me out to some solution.

[waclawek.jan · Accepted solution]

> htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;

If you change ARR below current CNT, CNT keeps incrementing until it overflows over its maximum value to 0, which in case of TIM2 - a 32-bit timer - is cca 4e9 counts (cca 40 seconds if timer's clock is around 100MHz).

The most straighforward solution is to enable ARR preload - this problem is exactly why ARR preload is for.

JW

[Ilya Suvorov]

Thank you for clear answer!