/**
@page IWDG_Example Independent Watchdog example
@verbatim
******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
* @file IWDG/IWDG_Example/readme.txt
* @author MCD Application Team
* @brief Description of the Independent Watchdog example.
******************************************************************************
* @attention
*
* Copyright (c) 2017 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
@endverbatim
@par Example Description
How to handle the IWDG reload counter and simulate a software fault that generates
an MCU IWDG reset after a preset laps of time.
At the beginning of the main program the HAL_Init() function is called to reset
all the peripherals, initialize the Flash interface and the systick.
Then the SystemClock_Config() function is used to configure the system
clock (SYSCLK) to run at 180 MHz.
The IWDG timeout is set to 250 ms (the timeout may vary due to LSI frequency
dispersion).
First, the TIM5 timer is configured to measure the LSI frequency as the
LSI is internally connected to TIM5 CH4, in order to adjust the IWDG clock.
The LSI measurement using the TIM5 is described below:
- Configure the TIM5 to remap internally the TIM5 CH4 Input Capture to the LSI
clock output.
- Enable the TIM5 Input Capture interrupt: after one cycle of LSI clock, the
period value is stored in a variable and compared to the HCLK clock to get
its real value.
Then, the IWDG reload counter is configured as below to obtain 250 ms according
to the measured LSI frequency after setting the prescaler value:
IWDG counter clock Frequency = LSI Frequency / Prescaler value
The IWDG reload counter is refreshed each 240 ms in the main program infinite
loop to prevent a IWDG reset.
LED2 is also toggled each 240 ms indicating that the program is running.
An EXTI Line is connected to a GPIO pin, and configured to generate an interrupt
on the rising edge of the signal.
The EXTI Line is used to simulate a software failure: once the EXTI Line event
occurs, by pressing the User push-button (PC.13), the corresponding interrupt
is served.
In the ISR, a write to invalid address generates a Hardfault exception
containing an infinite loop and preventing to return to main program (the IWDG
reload counter is not refreshed).
As a result, when the IWDG counter reaches 00h, the IWDG reset occurs.
If the IWDG reset is generated, after the system resumes from reset, LED1 is turned ON.
If the EXTI Line event does not occur, the IWDG counter is indefinitely refreshed in the main
program infinite loop, and there is no IWDG reset.
LED3 is turned ON and remains ON if any error occurs.
@note This example must be tested in standalone mode (not in debug).
@note Care must be taken when using HAL_Delay(), this function provides accurate
delay (in milliseconds) based on variable incremented in SysTick ISR. This
implies that if HAL_Delay() is called from a peripheral ISR process, then
the SysTick interrupt must have higher priority (numerically lower)
than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
@note The application need to ensure that the SysTick time base is always set to 1 millisecond
to have correct HAL operation.
@par Keywords
System, IWDG, Timeout, Reload Counter, MCU Reset, Downcounter, LSI, Timer, Measure Frequency
@par Directory contents
- IWDG/IWDG_Example/Inc/stm32f4xx_hal_conf.h HAL configuration file
- IWDG/IWDG_Example/Inc/stm32f4xx_it.h Interrupt handlers header file
- IWDG/IWDG_Example/Inc/main.h Header for main.c module
- IWDG/IWDG_Example/Src/stm32f4xx_it.c Interrupt handlers
- IWDG/IWDG_Example/Src/main.c Main program
- IWDG/IWDG_Example/Src/stm32f4xx_hal_msp.c HAL MSP file
- IWDG/IWDG_Example/Src/system_stm32f4xx.c STM32F4xx system source file
@par Hardware and Software environment
- This example runs on STM32F429xx devices.
- This example has been tested with NUCLEO-F429ZI Rev.B board and can be
easily tailored to any other supported device and development board.
@par How to use it ?
In order to make the program work, you must do the following :
- Open your preferred toolchain
- Rebuild all files: Project->Rebuild all
- Load project image: Project->Download and Debug
- Run program: Debug->Go(F5)
*/
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