121 lines
5.0 KiB
Plaintext
121 lines
5.0 KiB
Plaintext
/**
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@page IWDG_Example Independent Watchdog example
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@verbatim
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******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
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* @file IWDG/IWDG_Example/readme.txt
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* @author MCD Application Team
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* @brief Description of the Independent Watchdog example.
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******************************************************************************
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* @attention
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*
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* Copyright (c) 2017 STMicroelectronics.
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* All rights reserved.
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*
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* This software is licensed under terms that can be found in the LICENSE file
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* in the root directory of this software component.
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* If no LICENSE file comes with this software, it is provided AS-IS.
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*
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******************************************************************************
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@endverbatim
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@par Example Description
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How to handle the IWDG reload counter and simulate a software fault that generates
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an MCU IWDG reset after a preset laps of time.
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At the beginning of the main program the HAL_Init() function is called to reset
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all the peripherals, initialize the Flash interface and the systick.
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Then the SystemClock_Config() function is used to configure the system
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clock (SYSCLK) to run at 180 MHz.
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The IWDG timeout is set to 250 ms (the timeout may vary due to LSI frequency
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dispersion).
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First, the TIM5 timer is configured to measure the LSI frequency as the
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LSI is internally connected to TIM5 CH4, in order to adjust the IWDG clock.
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The LSI measurement using the TIM5 is described below:
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- Configure the TIM5 to remap internally the TIM5 CH4 Input Capture to the LSI
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clock output.
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- Enable the TIM5 Input Capture interrupt: after one cycle of LSI clock, the
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period value is stored in a variable and compared to the HCLK clock to get
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its real value.
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Then, the IWDG reload counter is configured as below to obtain 250 ms according
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to the measured LSI frequency after setting the prescaler value:
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IWDG counter clock Frequency = LSI Frequency / Prescaler value
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The IWDG reload counter is refreshed each 240 ms in the main program infinite
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loop to prevent a IWDG reset.
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LED2 toggles every 240 ms, indicating that the program is running.
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An EXTI Line is connected to a GPIO pin, and configured to generate an interrupt
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on the rising edge of the signal.
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The EXTI Line is used to simulate a software failure: once the EXTI Line event
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occurs, by pressing the User push-button (PA.00), the corresponding interrupt
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is served.
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In the ISR, a write to invalid address generates a Hardfault exception
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containing an infinite loop and preventing to return to main program (the IWDG
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reload counter is not refreshed).
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As a result, when the IWDG counter reaches 00h, the IWDG reset occurs.
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If the IWDG reset is generated, after the system resumes from reset, LED1 is turned ON.
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If the EXTI Line event does not occur, the IWDG counter is indefinitely refreshed in the main
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program infinite loop, and there is no IWDG reset.
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LED3 is turned ON and remains ON if any error occurs.
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@note This example must be tested in standalone mode (not in debug mode)
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@note Care must be taken when using HAL_Delay(), this function provides accurate
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delay (in milliseconds) based on variable incremented in SysTick ISR. This
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implies that if HAL_Delay() is called from a peripheral ISR process, then
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the SysTick interrupt must have higher priority (numerically lower)
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than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
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To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.
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@note The application need to ensure that the SysTick time base is always set to 1 millisecond
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to have correct HAL operation.
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@note The connection of the LCD reset pin to a dedicated GPIO PH7 instead of the STM32F469 NRST pin may cause residual display on LCD with applications/examples that do not require display.
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The LCD clear can be ensured by hardware through the boards power off/power on or by software calling the BSP_LCD_Reset() function.
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@par Keywords
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System, IWDG, Timeout, Reload Counter, MCU Reset, Downcounter, LSI, Timer, Measure Frequency
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@par Directory contents
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- IWDG/IWDG_Example/Inc/stm32f4xx_hal_conf.h HAL configuration file
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- IWDG/IWDG_Example/Inc/stm32f4xx_it.h Interrupt handlers header file
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- IWDG/IWDG_Example/Inc/main.h Header for main.c module
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- IWDG/IWDG_Example/Src/stm32f4xx_it.c Interrupt handlers
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- IWDG/IWDG_Example/Src/main.c Main program
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- IWDG/IWDG_Example/Src/stm32f4xx_hal_msp.c HAL MSP file
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- IWDG/IWDG_Example/Src/system_stm32f4xx.c STM32F4xx system source file
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@par Hardware and Software environment
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- This example runs on STM32F469xx devices.
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- This example has been tested with STM32469I-DISCOVERY board and can be
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easily tailored to any other supported device and development board.
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@par How to use it ?
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In order to make the program work, you must do the following :
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- Open your preferred toolchain
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- Rebuild all files: Project->Rebuild all
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- Load project image: Project->Download and Debug
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- Run program: Debug->Go(F5)
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*/
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