It's 3 times slower - my one microsecond timer configured by CubeMX running on NUCLEO-C031C6 (STM32C031C6)

[RongShengWang]

Hi, 

     My one microsecond timer configured by CubeMx running on NUCLEO-C031C6 (STM32C031C6) is 3 times slower than it should be. The code is attached below.

      the call "delay_us(60000000);" takes 3+ minutes to complete - it should be done in one minute.

      The LL timer (TIM3) init and interrupt code is generated by CubeMx..The system clock is 48 MHZ in CubeMx.

       How to fix it?

       Thanks,

      Rong

void MX_TIM3_Init(void)
{

  LL_TIM_InitTypeDef TIM_InitStruct = {0};

  /* Peripheral clock enable */
  LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_TIM3);

  /* TIM3 interrupt Init */
  NVIC_SetPriority(TIM3_IRQn, 0);
  NVIC_EnableIRQ(TIM3_IRQn);

  /* USER CODE BEGIN TIM3_Init 1 */

  /* USER CODE END TIM3_Init 1 */
  TIM_InitStruct.Prescaler = 0;
  TIM_InitStruct.CounterMode = LL_TIM_COUNTERMODE_UP;
  TIM_InitStruct.Autoreload = 48;
  TIM_InitStruct.ClockDivision = LL_TIM_CLOCKDIVISION_DIV1;
  LL_TIM_Init(TIM3, &TIM_InitStruct);
  LL_TIM_EnableARRPreload(TIM3);
  LL_TIM_SetClockSource(TIM3, LL_TIM_CLOCKSOURCE_INTERNAL);
  LL_TIM_SetTriggerOutput(TIM3, LL_TIM_TRGO_RESET);
  LL_TIM_DisableMasterSlaveMode(TIM3);
  /* TIM3 interrupt Init */
}

/* USER CODE BEGIN 1 */
unsigned long u_Count = 0;
/* USER CODE END 1 */
/**
  * @brief This function handles TIM3 global interrupt.
  */
void TIM3_IRQHandler(void)
{
  /* USER CODE BEGIN TIM3_IRQn 0 */

  if (u_Count)
  {
	  u_Count--;
  }
  if (LL_TIM_IsActiveFlag_UPDATE(TIM3))
 	LL_TIM_ClearFlag_UPDATE(TIM3);
  /* USER CODE END TIM3_IRQn 0 */
}

void delay_us(const unsigned long us_Count)
{
	u_Count = us_Count;
	LL_TIM_EnableIT_UPDATE(TIM3);
	LL_TIM_EnableCounter(TIM3);
	while (u_Count !=0) 
        {
        }
	LL_TIM_DisableIT_UPDATE(TIM3);
	LL_TIM_DisableCounter(TIM3);
}

int main(void)
{
  static unsigned int i = 0;
  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_TIM3_Init();
  MX_SPI1_Init();
  MX_USART2_UART_Init();

  delay_us(60000000);
}

[TDK]

The chip cannot process interrupts at 1 MHz. It will fall behind. Set your interrupt frequency to a max of about 10 kHz so one interrupt can finish before the next one is triggered.

Also note that if you have a timer frequency of 48 MHz, you want ARR=47 in order to have an update interval of 1 us. So for 10 kHz, it should be 4799.

[Tesla DeLorean]

As repeatedly covered on this forum, you can't sustain 1 MHz interrupt rate, it will saturated the processor just trying to do that. So don't do it that way.

Configure the TIM in maximal mode, say 0xFFFF or 0xFFFFFFFF with a prescaler that clocks the count at 1 MHz, and then delta the entry and exit points.

uint16_t start =TIM3->CNT;

while((TIM3->CNT - start) < usdelay);

For finer resolution clock faster. For longer delays with 16-bit counters, decompose into 60 ms (60000 us) intervals

[RongShengWang]

Hi, Guru,

    So I can not have a 1 us timer， which I need，in STM32C031C6?, 

    What is the fastest timer I can have in this micro ?

Thanks

Rong

[RongShengWang]

Hi, Tesla,

     Could you give me the detail code for having 1 us timers? 

     I used CubeMx to generate the code. 

     "Configure the TIM in maximal mode," - How to do this?

    Thanks,

Rong

void MX_TIM3_Init(void)
{

  /* USER CODE BEGIN TIM3_Init 0 */

  /* USER CODE END TIM3_Init 0 */

  LL_TIM_InitTypeDef TIM_InitStruct = {0};

  /* Peripheral clock enable */
  LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_TIM3);

  /* TIM3 interrupt Init */
  NVIC_SetPriority(TIM3_IRQn, 0);
  NVIC_EnableIRQ(TIM3_IRQn);

  /* USER CODE BEGIN TIM3_Init 1 */

  /* USER CODE END TIM3_Init 1 */
  TIM_InitStruct.Prescaler = 0;
  TIM_InitStruct.CounterMode = LL_TIM_COUNTERMODE_UP;
  TIM_InitStruct.Autoreload = 48;
  TIM_InitStruct.ClockDivision = LL_TIM_CLOCKDIVISION_DIV1;
  LL_TIM_Init(TIM3, &TIM_InitStruct);
  LL_TIM_EnableARRPreload(TIM3);
  LL_TIM_SetClockSource(TIM3, LL_TIM_CLOCKSOURCE_INTERNAL);
  LL_TIM_SetTriggerOutput(TIM3, LL_TIM_TRGO_RESET);
  LL_TIM_DisableMasterSlaveMode(TIM3);
  /* USER CODE BEGIN TIM3_Init 2 */
  /* TIM3 interrupt Init */

  /* USER CODE END TIM3_Init 2 */

}

[Tesla DeLorean]

Not using interrupts

  TIM_InitStruct.Prescaler = 48 - 1; // Divider 48 MHz to 1 MHz (1 us ticks)
  TIM_InitStruct.CounterMode = LL_TIM_COUNTERMODE_UP;
  TIM_InitStruct.Autoreload = 0xFFFF; // Maximal Count 0..65535
  TIM_InitStruct.ClockDivision = LL_TIM_CLOCKDIVISION_DIV1;

You're using it to count elapsed time, up to 65.535 ms per update period

[BarryWhit]

[rewritten for neutrality]

Measuring 1 minute with 1us resolution means 1ppm accuracy. That seems odd, considering that your typical crystal is spec'd for only about 20ppm accuracy. It means at the very least you'll have to calibrate your parameters against a more accurate timebase for each specific board at a specific temperature. 

As TDK and tesla have said, you can setup a tick timer to run faster than the standard system tick event (which runs at 1ms), but it's not reasonable to use one that runs 1000x faster. If you need higher resolution and a longer period, using a while loop to delay is almost certainly the wrong approach. You should consider using a timer's update ("overflow") event to trigger an interrupt, instead.

[RongShengWang]

Hi, Tesla,

     Understand. I will try.

     Thank you very much. 

Rong