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Example description

  
IWDG_Example IWDG_Example
  
Example Description 

This example shows how to update at regular period the IWDG reload counter and 
how to simulate a software fault generating an MCU IWDG reset on expiry of a 
programmed time period.

The IWDG timeout is set to 250 ms (the timeout may varies 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 to obtain 250 ms according to the 
measured LSI frequency.

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 Key push-button, 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 turns 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.

Directory contents 

  - IWDG_Example/system_stm32f2xx.c   STM32F2xx system clock configuration file 
  - IWDG_Example/stm32f2xx_conf.h     Library Configuration file
  - IWDG_Example/stm32f2xx_it.c       Interrupt handlers
  - IWDG_Example/stm32f2xx_it.h       Header for stm32f2xx_it.c
  - IWDG_Example/main.c               Main program

	  The "system_stm32f2xx.c" is generated by an automatic clock configuration 
      tool and can be easily customized to your own configuration. 
      To select different clock setup, use the "STM32F2xx_Clock_Configuration_V1.0.0.xls" tool. 

Hardware and Software environment 

  - This example runs on STM32F2xx Devices.
  
  - This example has been tested with STM322xG-EVAL RevB and can be easily tailored
    to any other development board

  - STM322xG-EVAL Set-up  
    - Use LD1 and LD2 leds connected respectively to PG.06 and PG.08 pins
    - Use the KEY push button connected to PG.15 pin (EXTI Line15).