Solution to the problem of closing the watchdog of STM32 in the sleep mode (stop/standby)

It has long been believed that Stm32 To enable the IWDG After the watchdog , You can no longer use sleep to enter low power mode . Since the watchdog cannot stop after it is started , It has brought trouble to many people . There are many people who have given up using the watchdog , So as to bring certain uncertainty to the product .

In fact, there is a simple way to achieve reliable sleep with a watchdog . I named it “ two-step ”. seeing the name of a thing one thinks of its function ：

First step ： stay flash Or anywhere you can save it , Write an identifier , such as 1; Then execute the single-chip microcomputer restart , such as NVIC_SystemReset（）

The second step ： After restart main In the entrance , Before using the watchdog , Check the above marks first , If it is 1, Clear this first 1, Change it to 0, preservation , Then enter the real sleep process, such as Sys_Standby（）{...}; If not 1, So clearly , This is the process of awakening . Just go straight to the next program .

//standby  by flash A certain address in 
// Perform identity setting and restart before hibernation 
void Pre_Standby(void){
	standby=1;
	WriteParam2Flash();
	NVIC_SystemReset();
}
// Perform a real sleep 
void Sys_StandbyReal(void){
	RCC_APB2PeriphResetCmd(0x01fc, DISABLE);// Close all pins 
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR, ENABLE);	// Can make PWR Peripheral clock 
	PWR_WakeUpPinCmd(ENABLE);  // Enable to wake up the pin function 
	PWR_EnterSTANDBYMode();	  // On standby （STANDBY） Pattern  		 
}

// entrance 
void  main(void){
// Various initializations 

...
ReadParamFlash();// Read flash part 
    if(standby==1){// Really go into sleep   Otherwise, it is the real boot 
		standby=0;
		WriteParam2Flash();// Save again 
		Sys_StandbyReal();		
	}
IWDG_Config();// Set up a watchdog   Put it behind the identification test 
// The following is the main program 
...
    while(1){
        ...
        IWDG_FEED();
    }
}

// When calling sleep , perform Pre_Standby();

Although I have to read and write 2 Time flash, But it is more cost-effective than the life of the product itself and the reliability of the program , Of course, it can also be saved externally eprom in , In this way, the life span is greatly increased . In addition, I think it can also be saved in a register that can still be saved after hibernation , I haven't studied yet , You can reply me if you know .