I am using stm32f103 for project and keil ide for the compilation. I have configured timer 2 having 16 MHz clk frequency. I need to generate interrupt at 100 ms so I have configured Prescaler val as 24 and period val as 63999. but getting at 95 or 112 ms

[Peter BENSCH]

Welcome, @PGare.1​, to the community!

do you use HSI as clock source?

Regards

/Peter

[PGare.1]

Thanks for reply. No We are using HSE as clock source

[Peter BENSCH]

OK.

Did you check the frequency coming from HSE using e.g. the pin MCO?

How did you measure the duration of TIM2?

Regards

/Peter

[PGare.1]

//**********************************In main.c********************************//
 
int main(void)
{
  HAL_Init();
 
  /* Configure the system clock */
  SystemClock_Config();
 
  /* Initialize all configured peripherals */
  MX_USART1_UART_Init();
  MX_TIM2_Init();
	while(1)
	{
		if (TimerOut == 1)
		{
			TimerOut = 0;
			printf("A\n");
		}
		fflush(stdout);
	}
}
 
 
/**
  * @brief TIM2 Initialization Function
  * @param None
  * @retval None
  */
void MX_TIM2_Init(void)
{
  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};
 
  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 24;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 63999;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim2.Init.RepetitionCounter = 0;
	
  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();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
		
   if (HAL_TIM_Base_Start_IT(&htim2) != HAL_OK)
  {
    Error_Handler();
  }
}
 
 
/**
  * @brief USART1 Initialization Function
  * @param None
  * @retval None
  */
static void MX_USART1_UART_Init(void)
{
 
  /* USER CODE BEGIN USART1_Init 0 */
 
  /* USER CODE END USART1_Init 0 */
 
  /* USER CODE BEGIN USART1_Init 1 */
 
  /* USER CODE END USART1_Init 1 */
  huart1.Instance = USART1;
  huart1.Init.BaudRate = 460800; //19200
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART1_Init 2 */
 
  /* USER CODE END USART1_Init 2 */
}
 
 
//*************************************In stm32f1xx_it.c******************//
volatile OUint8 TimerOut = 0;
void TIM2_IRQHandler(void)
{
	__HAL_TIM_CLEAR_IT(&htim2, TIM_IT_UPDATE);
	TimerOut = 1;
}
 
//************************************In stm32f1xx_hal_msp.c*******************//
void HAL_TIM_Base_MspInit(TIM_HandleTypeDef* htim_base)
{
  if(htim_base->Instance==TIM2)
  {
    __HAL_RCC_TIM2_CLK_ENABLE();
    HAL_NVIC_SetPriority(TIM2_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(TIM2_IRQn);
  }
}

with help of USART1. Printing A on serial terminal when interrupt get generated. timestamp is logged in minicom utility on linux

[Peter BENSCH · Accepted solution]

The duration of the timer should be measured as directly as possible, e.g. by switching and measuring on a GPIO.

printf is not suitable for this use case, especially if its output is sent to Linux, which is not an RTOS with a predictable response time.

Regards

/Peter

[PGare.1]

Thank you