Please ask senior programmers to help look at this problem

一沙一世

Please ask senior programmers to help look at this problem [Copy link]

邀请：@maychang   @damiaa   @vincentc543   @RichSJ   参与回复

Please look at the following two functions. When the program executes to (1), if an RTC interrupt occurs suddenly, will it cause dyjc not to be equal to 1190 after the close function is executed?

The reasons are as follows: for example, the sentence dyjc = 1190 needs to be completed by 4 machine instructions at the low level. When the second of these 4 instructions is just executed, the RTC interrupt occurs. At this time, the MCU turns to execute multiple machine instructions corresponding to dyjc++. After executing multiple machine instructions corresponding to dyjc++, the third and fourth machine instructions corresponding to dyjc = 1190 are executed. Therefore, after the close() function is executed, the final value of dyjc may not be 1190. Is this analysis correct?

If this is correct, how can we avoid this situation? Thank you.

one,

void close( void)
{
.......

cs_low_fm = 0;
dyjc = 1190; // (1)
...

}

two,

void RTC_IRQHandler(void) // RTC interrupt is executed once per second
{
.......
dyjc++; // (2)
...

}

maychang

"So maybe after the close() function is executed, the final value of dyjc is not 1190. Is this analysis correct?"

Yes. That is possible.

maychang

This is possible as long as the dyjc variable is used in multiple places (in multiple functions).

一沙一世

maychang posted on 2022-6-4 16:22 As long as the dyjc variable is used in multiple places (in multiple functions), this is possible.

Thank you very much. Our leader's heart must have stopped beating.

maychang

Yishayishi published on 2022-6-4 16:26 Thank you very much. Then our leader's little heart must have stopped suddenly.

The probability of this error is very small. Your timer interrupt occurs once a second. When the timer interrupt modifies a variable, and the error occurs when the variable is assigned a value, the error will occur. Therefore, this error may not occur even if the program is run several times, dozens of times, hundreds of times, or thousands of times, and it is difficult to detect. But it is indeed an error.

damiaa

void close( void)
{

.......

//Turn off the rtc interrupt here,

dyjc = 1190;

//Here rtc interrupt is turned on.

.......

}

Or dyjc with a flag dyjc_write_flag

Main program:

void close( void)
{

.......

dyjc_write_flag =0；

dyjc = 1190;

if(dyjc_write_flag ==1) //If an RTC interrupt occurs at this time, reassign the value.

{

dyjc = 1190;

dyjc_write_flag =0；

}

.......

}

RTC interrupt

void RTC_IRQHandler(void) //RTC interrupt is executed once per second
{
.......

dyjc_write_flag =1;

dyjc++;

.......

}

RichSJ

damiaa 发表于 2022-6-4 19:33 void close( void) { ....... ...

These are good solutions, but the first one has a problem. If an RTC interrupt occurs, turning off the interrupt will cause the interrupt to be lost.

RichSJ

I don't know which chip you are talking about. In the ST chip, I can use assembly language to directly set it to that address, avoiding this problem. Of course, it will bring difficulties to the software update because it is necessary to find the absolute address.

vincentc543

要改善這問題,用close函數發出dyjc 歸位的旗標.

只在RTC中斷內做dyjc的賦值,應該就沒這問題了

vincentc543

bool flag=0;

void close( void)
{
.......

cs_low_fm = 0;
flag=1; //dyjc set value
.......

}

two,

void RTC_IRQHandler(void) // RTC interrupt is executed once per second
{
.......
dyjc++; // (2)

if(flag){

dyjc = 1190; // (1)

flag=0;

}
.......

}