IWDG - Not able to write Prescaler & Reload register

[KVenk.1]

Hi,

I am trying to check IWDG functionality on Nucleo-L4R5ZI board.

Referring to the example code available for NUCLEO-L496ZG, i created new project for L4R5ZI nucleo.

I was trying to go step by step in debug mode. When the debugger is inside HAL_IWDG_Init(&hiwdg), it was able to successfully enable IWDG using __HAL_IWDG_START(hiwdg);

But when do step into IWDG_ENABLE_WRITE_ACCESS(hiwdg); the debugger enters into system memory. I confirmed this by PAUSEing the debug, and it stopped at 0x1FFFxxxx address. At the same time, LD3 led is glowing. Nowhere in the code I control the LD3. What is happening ? Pls help.

Code is as below:

/* 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;
 
UART_HandleTypeDef hlpuart1;
UART_HandleTypeDef huart1;
UART_HandleTypeDef huart3;
 
PCD_HandleTypeDef hpcd_USB_OTG_FS;
 
/* USER CODE BEGIN PV */
 
/* USER CODE END PV */
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_LPUART1_UART_Init(void);
static void MX_USART3_UART_Init(void);
static void MX_USB_OTG_FS_PCD_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();
  MX_LPUART1_UART_Init();
  MX_USART3_UART_Init();
  MX_USB_OTG_FS_PCD_Init();
  MX_IWDG_Init();
  /* USER CODE BEGIN 2 */
 
  if(HAL_IWDG_Init(&hiwdg) != HAL_OK)
  {
    /* Initialization Error */
    Error_Handler();
  }
 
  /* USER CODE END 2 */
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */
 
	/* Refresh IWDG: reload counter */
	if(HAL_IWDG_Refresh(&hiwdg) != HAL_OK)
	{
	  /* Refresh Error */
	  Error_Handler();
	}
 
	HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0, GPIO_PIN_RESET);
	while(1);
 
    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}
 
 
/**
  * @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_32;
  hiwdg.Init.Window = IWDG_WINDOW_DISABLE;
  hiwdg.Init.Reload = 4095;
  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_GPIOH_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOG_CLK_ENABLE();
  HAL_PWREx_EnableVddIO2();
 
  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0, GPIO_PIN_SET);
 
  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOB, LD3_Pin|LD2_Pin, GPIO_PIN_RESET);
 
  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(USB_PowerSwitchOn_GPIO_Port, USB_PowerSwitchOn_Pin, GPIO_PIN_RESET);
 
  /*Configure GPIO pin : B1_Pin */
  GPIO_InitStruct.Pin = B1_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(B1_GPIO_Port, &GPIO_InitStruct);
 
  /*Configure GPIO pin : PA0 */
  GPIO_InitStruct.Pin = GPIO_PIN_0;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 
  /*Configure GPIO pins : LD3_Pin LD2_Pin */
  GPIO_InitStruct.Pin = LD3_Pin|LD2_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
 
  /*Configure GPIO pin : USB_PowerSwitchOn_Pin */
  GPIO_InitStruct.Pin = USB_PowerSwitchOn_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(USB_PowerSwitchOn_GPIO_Port, &GPIO_InitStruct);
 
  /*Configure GPIO pin : USB_OverCurrent_Pin */
  GPIO_InitStruct.Pin = USB_OverCurrent_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(USB_OverCurrent_GPIO_Port, &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****/

[waclawek.jan]

Unless you have set DBG_IWDG_STOP in DBG module, after you enable the watchdog, it promptly expires and resets your mcu.

JW

[KVenk.1]

I have not even configured the Prescaler and Reload register. How come the WDG start before that ? Even assuming it did start, what is the default reload & prescaler value which it takes to reset the controller ?

[KVenk.1 · Accepted solution]

I found th eproblem. I was testing in debug mode. Thats the reason. Datasheet says "When the device enters Debug mode (core halted), the IWDG counter either continues to work normally or stops, depending on the configuration of the corresponding bit in DBGMCU freeze register."

So when I quit debug mode and do a power recycle, i could see expected behaviour.