Overview

In this tutorial, we will see how to use IWDG (Independent Monitor) and WWDG (Window Monitor) in STM32. Both monitors are used for a similar purpose, but the difference is in their implementation. The main difference between the two is that a standalone watcher can be reset at any time before it times out, but the Window Watchdog can only be reset in a certain time window.

let’s start with the first now.

Independent Watchdog (IWDG)

  • An independent monitoring body is used to detect and resolve malfunctions resulting from software failures. It triggers a restart sequence when it is not refreshed within the expected time window.
  • Since its clock is an internal 32 kHz (LSI) low speed RC oscillator, it remains active even if the master clock fails.
  • Once enabled, it forces the internal low-speed oscillator to run, and can only be disabled through a reset.
  • One of the main benefits of apps is their ability to operate independently of the master clock.

Steps

Translation results

The CubeIDE configuration is shown below

RCC Mode and Configuration

SYS Mode and Configuration

IWDG Mode and Configuration with 20ms Delay

Pin Configuration

LSI RC 40Khz

As you can see above, there are two parameters that we need to enter i.e. Prescaler and Counter values. These values will determine when to reload our app. To determine these values, there is a formula provided by ST as follows

  • The above formula is shown below.
  • RLD is the value of the counter, which we must put in the configuration
  • Time is the timeout value (in milliseconds) of the watch mechanism. If the counter is not updated before this time, the system will restart
  • PR is the pre-scaler value and the values are as shown below
  1. Let’s take an example if I want to set the timeout to 20ms.
  2. I decided to choose Prescalar as 8. So PR = 1
  3. If we substitute these values into the previous formula, we get RLD = 100.
  4. So we need to substitute the counter value = 100 into our configuration.
  5. If the RLD value exceeds 4095, you must increase the pre-gauge.

Modified code

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();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

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

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();

  HAL_Delay(500);
  HAL_GPIO_WritePin(GPIOC, GPIO_PIN_9, 1);


  MX_IWDG_Init();
  /* USER CODE BEGIN 2 */

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

	  HAL_Delay(10);
	  HAL_IWDG_Refresh(&hiwdg);

    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

Final code

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; Copyright (c) 2022 STMicroelectronics.
  * All rights reserved.</center></h2>
  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                        opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/
IWDG_HandleTypeDef hiwdg;

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_IWDG_Init(void);
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
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();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

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

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();

  HAL_Delay(500);
  HAL_GPIO_WritePin(GPIOC, GPIO_PIN_9, 1);


  MX_IWDG_Init();
  /* USER CODE BEGIN 2 */

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

	  HAL_Delay(10);
	  HAL_IWDG_Refresh(&hiwdg);

    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Initializes the CPU, AHB and APB busses clocks 
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_LSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.LSIState = RCC_LSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL12;
  RCC_OscInitStruct.PLL.PREDIV = RCC_PREDIV_DIV1;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  /** Initializes the CPU, AHB and APB busses clocks 
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
  {
    Error_Handler();
  }
}

/**
  * @brief IWDG Initialization Function
  * @param None
  * @retval None
  */
static void MX_IWDG_Init(void)
{

  /* USER CODE BEGIN IWDG_Init 0 */

  /* USER CODE END IWDG_Init 0 */

  /* USER CODE BEGIN IWDG_Init 1 */

  /* USER CODE END IWDG_Init 1 */
  hiwdg.Instance = IWDG;
  hiwdg.Init.Prescaler = IWDG_PRESCALER_4;
  hiwdg.Init.Window = 4095;
  hiwdg.Init.Reload = 200;
  if (HAL_IWDG_Init(&hiwdg) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN IWDG_Init 2 */

  /* USER CODE END IWDG_Init 2 */

}

/**
  * @brief GPIO Initialization Function
  * @param None
  * @retval None
  */
static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOF_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOC, GPIO_PIN_9, GPIO_PIN_RESET);

  /*Configure GPIO pin : PC9 */
  GPIO_InitStruct.Pin = GPIO_PIN_9;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */

  /* USER CODE END Error_Handler_Debug */
}

#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,
     tex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

output waveforms

20ms watchdog timer delay

hiwdg.Init.Reload = 100;

Off time

40ms delay watchdog timer

hiwdg.Init.Reload = 200;

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