Function independent watchdog (iwdg) experiment based on stm32f103zet6 Library

STM32 Inside I brought it with me 2 A watchdog ： Independent watchdog （IWDG） And the window watchdog （WWDG）, Here we only introduce the independent watchdog , We will press the button WK_UP Feed the dog , Then pass too DS0 Prompt reset status .

STM32 Introduction to independent watchdog

STM32 The independent watchdog consists of an internal specialized 40Khz Low speed clock drive , Even if the master clock fails , It's still It works . It should be noted here that the clock of the independent watchdog is an internal RC The clock , So it's not accurate 40Khz, It is stay 30~60Khz A variable clock between , It's just that when we estimate , With 40Khz To calculate the frequency of , see The door dog is not very precise about the time , therefore , The clock is a little off , All are acceptable .

Single chip microcomputer system in the external interference will appear under the phenomenon of program running, leading to the emergence of dead cycle , The watchdog circuit is designed to avoid This happens . The role of a watchdog is to （ Through the timer counter ） No dog feed signal received （ Express MCU It's gone ）, The processor can reset and restart automatically （ Send a reset signal ）.

Independent watchdog related library functions and definitions are distributed in the file stm32f10x_iwdg.h and stm32f10x_iwdg.c in
1. Cancel register write protection （ towards IWDG_KR write in 0X5555）
Through this step , We cancel IWDG_PR and IWDG_RLR Write protection for , So that the two registers can be operated later , Set up IWDG_PR and IWDG_RLR Value . The implementation function in the library function is ：

IWDG_WriteAccessCmd(IWDG_WriteAccess_Enable); 

2. Set the prescaler factor and reload value of the independent watchdog
The function of setting the frequency division coefficient of the watchdog is ：

void IWDG_SetPrescaler(uint8_t IWDG_Prescaler);  // Set up  IWDG  Prescaled value  

The function to set the watchdog reload value is ：

void IWDG_SetReload(uint16_t Reload); // Set up  IWDG  Reload value  

Set the frequency division coefficient of the good looking dog prer And reload load value can be used to know the feeding time of the watchdog （ That is, the watchdog overflow Out time ）, The time is calculated as ：

Tout=((4×2^prer) ×rlr) /40 

among Tout Overflow time for watchdog （ Unit is ms）;prer Pre frequency the watchdog clock （IWDG_PR value ）, The scope is 0~7;rlr Load value for the watchdog （IWDG_RLR Value ）
For example, we set prer The value is 4,rlr The value is 625, Then you can get Tout=64×625/40=1000ms, such , The watchdog's overflow time is 1s, As long as you're in a second , Once I wrote 0XAAAA To IWDG_KR, No Will cause the watchdog to reset （ Of course, writing multiple times is OK ）. What we need to remind you of here is , The watchdog clock is not accurate Yes 40Khz, So when you feed the dog , It's better not to be too late , otherwise , There is a possibility of watchdog reset .

3. Load count value feed dog （ towards IWDG_KR write in 0XAAAA）
The function in the library function that overloads the count value is ：

IWDG_ReloadCounter();  // according to  IWDG  Reload the value of the load register  IWDG  Counter  

Through this sentence , Will make STM32 Reload IWDG_RLR To the watchdog counter . That is to realize the feeding operation of the independent watchdog .

4. Start the watchdog ( towards IWDG_KR write in 0XCCCC)
The function to start the independent watchdog in the library function is ：

IWDG_Enable();  // Can make  IWDG 

Through this sentence , To start up STM32 The watchdog . Be careful IWDG Once enabled , It can't be shut down again ！ Want to close close , Can only restart , And it can't be turned on after restart IWDG, Otherwise, the problem remains , So I'm here to remind you , If you don't use IWDG Words , Just don't open it , Avoid trouble .

After configuring the watchdog ,DS0 Will always be bright , If WK_UP Press the key , Just feed the dog , as long as WK_UP Keep pressing , The watchdog will never reset , keep DS0 Chang liang of , Once the watchdog set overflow time is exceeded （Tout） Not yet , Then it will cause the program to restart , This will lead to DS0 Put it out once .

Hardware design

1） Indicator light DS0
2） WK_UP Key
3） Independent watchdog

software design

wdg.c

#include "wdg.h"

// Initialize the independent watchdog 
//prer: Frequency division number :0~7( Only low 3 Bit effective !)
// Division factor =4*2^prer. But the maximum can only be 256!
//rlr: Reload register values : low 11 Bit effective .
// Time calculation ( Probably ):Tout=((4*2^prer)*rlr)/40 (ms).
void IWDG_Init(u8 prer,u16 rlr) 
{
    	
 	IWDG_WriteAccessCmd(IWDG_WriteAccess_Enable);  					// Enable on register IWDG_PR and IWDG_RLR Write operations for 
	IWDG_SetPrescaler(prer);  										// Set up IWDG Prescaled value : Set up IWDG The prescaled value is 64
	IWDG_SetReload(rlr);  											// Set up IWDG Reload value 
	IWDG_ReloadCounter();  											// according to IWDG Reload the value of the load register IWDG Counter 
	IWDG_Enable();  												// Can make IWDG
}

// Hello, the independent watchdog 
void IWDG_Feed(void)
{
       
 	IWDG_ReloadCounter();											//reload 
}

because STM32 To feed a dog, you only need to write... To the key value register Enter into 0XAAAA that will do , That is to call IWDG_ReloadCounter() function

wdg.h

#ifndef __WDG_H
#define __WDG_H
#include "sys.h"

void IWDG_Init(u8 prer,u16 rlr);
void IWDG_Feed(void);

#endif

main.c

#include "led.h"
#include "delay.h"
#include "key.h"
#include "sys.h"
#include "usart.h"
#include "wdg.h"

int main(void)
{
    		
	delay_init();	    	 								// Delay function initialization  
	NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); 	    // Set up NVIC Interrupt grouping 2:2 Bit preemption priority ,2 Bit response priority 
	uart_init(115200);	 									// The serial port is initialized to 115200
 	LED_Init();		  	 									// Initialization and LED Connected hardware interface 
	KEY_Init();          									// Key initialization  
	delay_ms(500);   	 									// Let people see 
	IWDG_Init(4,625);    									// And the frequency division number is 64, The overload value is 625, The overflow time is 1s 
	LED0=0;				 									// Lighten up LED0
	while(1)
	{
    
		if(KEY_Scan(0)==WKUP_PRES)
		{
    
			IWDG_Feed();									// If WK_UP Press down , Then feed the dog 
		}
		delay_ms(10);
	};	 
}