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Wrong value of Duty Cycle value of PWM Input Capture

Question asked by kumar.nitin.002 on Jul 28, 2016
Latest reply on Jul 28, 2016 by kumar.nitin.002
Hi All,

I was trying to measure duty cycle and frequency of a pwm signal by using a timer with pwm output to generate pwm signal and another timer in reset mode to measure pwm using one of the example. The logic analyzer shows 49.97 % to 50 % for duty cycle and 14400 hz for frequency but the measured value using reset mode, the duty cycle is always 49.0 % and frequency comes out 14403 hz to 14405 hz.

What is the mistake? Code is attached.
/**
  ******************************************************************************
  * File Name          : main.c
  * Description        : Main program body
  ******************************************************************************
  *
  * COPYRIGHT(c) 2016 STMicroelectronics
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *   1. Redistributions of source code must retain the above copyright notice,
  *      this list of conditions and the following disclaimer.
  *   2. Redistributions in binary form must reproduce the above copyright notice,
  *      this list of conditions and the following disclaimer in the documentation
  *      and/or other materials provided with the distribution.
  *   3. Neither the name of STMicroelectronics nor the names of its contributors
  *      may be used to endorse or promote products derived from this software
  *      without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  */
/* Includes ------------------------------------------------------------------*/
#include "stm32f1xx_hal.h"
 
/* USER CODE BEGIN Includes */
 
/* USER CODE END Includes */
 
/* Private variables ---------------------------------------------------------*/
TIM_HandleTypeDef htim3;
TIM_HandleTypeDef htim4;
 
/* USER CODE BEGIN PV */
/* Private variables ---------------------------------------------------------*/
__IO float sigDuty = 0;
__IO uint32_t sigFreq = 0;
__IO uint32_t sigICRValue = 0;
__IO uint32_t errFlag = 0;
 
/* USER CODE END PV */
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM4_Init(void);
static void MX_TIM3_Init(void);
                     
void HAL_TIM_MspPostInit(TIM_HandleTypeDef *htim);
                 
 
/* USER CODE BEGIN PFP */
/* Private function prototypes -----------------------------------------------*/
void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *htim);
/* USER CODE END PFP */
 
/* USER CODE BEGIN 0 */
 
/* USER CODE END 0 */
 
int main(void)
{
 
  /* USER CODE BEGIN 1 */
 
  /* USER CODE END 1 */
 
  /* MCU Configuration----------------------------------------------------------*/
 
  /* 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_TIM4_Init();
  MX_TIM3_Init();
 
  /* USER CODE BEGIN 2 */
 
 
  // timer 3
 
  HAL_TIM_PWM_Start(&htim3,TIM_CHANNEL_4);
  HAL_TIM_Base_Start(&htim3);
 
  // timer 4
 
  if(HAL_TIM_IC_Start_IT(&htim4, TIM_CHANNEL_2)!=HAL_OK)
      errFlag = 1;
 
  if(HAL_TIM_IC_Start_IT(&htim4, TIM_CHANNEL_1)!=HAL_OK)
      errFlag = 2;
 
  /* USER CODE END 2 */
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
  /* USER CODE END WHILE */
 
  /* USER CODE BEGIN 3 */
 
  }
  /* USER CODE END 3 */
 
}
 
/** System Clock Configuration
*/
void SystemClock_Config(void)
{
 
  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;
 
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  HAL_RCC_OscConfig(&RCC_OscInitStruct);
 
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
  HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2);
 
  HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
 
  HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
 
  /* SysTick_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}
 
/* TIM3 init function */
void MX_TIM3_Init(void)
{
 
  TIM_MasterConfigTypeDef sMasterConfig;
  TIM_OC_InitTypeDef sConfigOC;
 
  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 499;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 9;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  HAL_TIM_PWM_Init(&htim3);
 
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig);
 
  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = 5;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_ENABLE;
  HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_4);
 
  HAL_TIM_MspPostInit(&htim3);
 
}
 
/* TIM4 init function */
void MX_TIM4_Init(void)
{
 
  TIM_SlaveConfigTypeDef sSlaveConfig;
  TIM_MasterConfigTypeDef sMasterConfig;
  TIM_IC_InitTypeDef sConfigIC;
 
  htim4.Instance = TIM4;
  htim4.Init.Prescaler = 0;
  htim4.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim4.Init.Period = 65535;
  htim4.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  HAL_TIM_Base_Init(&htim4);
 
  HAL_TIM_IC_Init(&htim4);
 
  sSlaveConfig.SlaveMode = TIM_SLAVEMODE_RESET;
  sSlaveConfig.InputTrigger = TIM_TS_TI2FP2;
  sSlaveConfig.TriggerPolarity = TIM_TRIGGERPOLARITY_BOTHEDGE;
  sSlaveConfig.TriggerFilter = 0;
  HAL_TIM_SlaveConfigSynchronization(&htim4, &sSlaveConfig);
 
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  HAL_TIMEx_MasterConfigSynchronization(&htim4, &sMasterConfig);
 
  sConfigIC.ICPolarity = TIM_INPUTCHANNELPOLARITY_FALLING;
  sConfigIC.ICSelection = TIM_ICSELECTION_INDIRECTTI;
  sConfigIC.ICPrescaler = TIM_ICPSC_DIV1;
  sConfigIC.ICFilter = 0;
  HAL_TIM_IC_ConfigChannel(&htim4, &sConfigIC, TIM_CHANNEL_1);
 
  sConfigIC.ICPolarity = TIM_INPUTCHANNELPOLARITY_RISING;
  sConfigIC.ICSelection = TIM_ICSELECTION_DIRECTTI;
  HAL_TIM_IC_ConfigChannel(&htim4, &sConfigIC, TIM_CHANNEL_2);
 
}
 
/** Configure pins as
        * Analog
        * Input
        * Output
        * EVENT_OUT
        * EXTI
*/
void MX_GPIO_Init(void)
{
 
  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
 
}
 
/* USER CODE BEGIN 4 */
 
void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *htim)
{
    if(htim->Channel == HAL_TIM_ACTIVE_CHANNEL_2)
    {
        sigICRValue = HAL_TIM_ReadCapturedValue(htim, TIM_CHANNEL_2);
 
        if(sigICRValue != 0)
        {
            sigDuty = ((HAL_TIM_ReadCapturedValue(htim, TIM_CHANNEL_1))* 100 ) / sigICRValue;
            sigFreq = (HAL_RCC_GetHCLKFreq())  / sigICRValue;
        }
        else
        {
            sigDuty = 0;
            sigFreq = 0;
        }
    }
    else
    {
        errFlag = 3;
    }
}
 
/* USER CODE END 4 */
 
#ifdef USE_FULL_ASSERT
 
/**
   * @brief Reports the name of the source file and the source line number
   * where the assert_param error has occurred.
   * @param file: pointer to the source file name
   * @param line: assert_param error line source number
   * @retval None
   */
void assert_failed(uint8_t* file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
    ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
 
}
 
#endif
 
/**
  * @}
  */
 
/**
  * @}
*/
 
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

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