STM32 introductory study notes: watchdog experiment (Part 2)

14.4.2 Window watchdog experiment

Function: As soon as the program is run, LED1 connected to PB5 lights up for 300ms and then turns off, entering an infinite loop. Wait for the WWDG interrupt to arrive. In the interrupt, feed the dog and flip LED2 on PE5. You can see that LED2 flashes continuously, and LED1 only flashes once when it is first started.

(1) Add the following code in the function list area of ​​the wdg.h file in the previous experiment.

void WWDG_Init( u8 tr, u8 wr, u8 fprer ); //Window watchdog initialization

(2) Add the following code at the end of the wdg.c file of the previous experiment.

/****************************************************** **

Name:WWDG_IRQHandler

Function: Window watchdog interrupt service routine

Paramater:None

Return :None

*************************************************** */

void WWDG_IRQHandler()

{

  WWDG->CR = 0x7F; //Reset the 7-bit counter

  WWDG->SR = 0x00; //Clear the early wake-up interrupt flag bit

  LED2 != LED2 ;

}

/****************************************************** **

Name:WWDG_Init

Function: Window watchdog initialization

Paramater:

      tr: counter value

      wr: window value

      fprer: frequency division coefficient

Return :None

*************************************************** */

void WWDG_Init( u8 tr, u8 wr, u8 fprer )

{

  RCC->APB1ENR |= 1<<11; //Enable wwdg clock

  WWDG->CFR |= fprer<<7; //PCLK1/4096 divided by 2^fprer

  WWDG->CFR &= 0xFF80;

  WWDG->CFR |= wr; //Set window value

  WWDG->CR |= tr&0x7F; //Set counter value

  WWDG->CR |= 1<<7; //Enable watchdog

  NVIC_Init(2, 3, WWDG_IRQn, 2); //Preemption 2, sub-priority 3, group 2

  WWDG->SR = 0x00; //Clear the early wake-up interrupt flag bit

  WWDG->CFR |= 1<<9; //Enable early wake-up interrupt

}

Note: Since LED2 is referenced in the interrupt service function, the header file #include "led.h" needs to be added.

(3) Create the led.h file and enter the following code.

#ifndef _LED_H_

#define _LED_H_

#include "sys.h"

/****************************************************** *************************************************** ******

                  Hardware port

*************************************************** *************************************************** *****/

#define LED1 PBout(5) //Define LED1 port

#define LED2 PEout(5) //Define LED2 port

/****************************************************** *************************************************** ******

                  function list

*************************************************** *************************************************** *****/

void LED_Init( void ); //LED initialization

#endif

(4) Create the led.c file and enter the following code.

#include "led.h"

/****************************************************** **

Name:LED_Init

Function:LED initialization

Paramater:None

Return :None

*************************************************** */

void LED_Init()

{

  RCC->APB2ENR |= 1<<3;

  GPIOB->CRL &= 0xFF0FFFFF;

  GPIOB->CRL |= 0x00300000;

  RCC->APB2ENR |= 1<<6;

  GPIOE->CRL &= 0xFF0FFFFF;

  GPIOE->CRL |= 0x00300000;

  LED1 = 1;

  LED2 = 1;

}

(5) Enter the following code in file 1.c.

#include "sys.h"

#include "delay.h"

#include "usart1.h"

#include "led.h"

#include "wdg.h"

/****************************************************** **

Name: main

Function: main function

Parameter:None

Return :None

*************************************************** */

int main()

{

  STM32_Clock_Init( 9 ); //STM32 clock initialization

  SysTick_Init( 72 ); //SysTick initialization

  USART1_Init( 72, 115200 ); //Initialize serial port 1 baud rate 115200

  LED_Init(); //LED initialization

  LED1 = 0; //Light up DS0

  delay_ms(300); //Delay 300ms so that people can see the status of DS0 on

   WWDG_Init(0x7F, 0x5F, 3); //The counter value is 7f, the window register is 5f, and the frequency division number is 8

  while(1)

  {

    LED1 = 1; //Turn off LED1

  }

}

14.5 Why does STM32 have both window watchdog and independent watchdog?

14.5.1 Conditions for using independent watchdog

(1) The program runs away

(2) An infinite loop occurs

(3) Sleep and hibernation are unreasonable

(4) The external main crystal oscillator is damaged

(5) Need to be reset again and no data will be retained.

14.5.2 Window watchdog usage conditions

(1) There is an error in the software logic

(2) Crash or infinite loop

(3) Software execution does not perform as expected

(4) The software needs to be reset again, but all data will be retained

14.5.3 The difference between the two

(1) The independent watchdog uses an internal dedicated 40kHz low-speed clock

The window watchdog uses the clock of PCLK1

(2) The independent watchdog has no interruption and is directly reset when timeout occurs.

The window watchdog has an interrupt. The timeout can be operated in the interrupt service function or fed to the dog.

(3) Independent watchdogs are generally used to avoid program runaways or infinite loops

The window watchdog is to prevent the program from not executing according to the preset logic.

(4) The independent watchdog is a 12-bit decrement operation

The window watchdog is a 6-bit decrement operation