How to transform date and time received to timestamp

[FPicc.1]

Hi all,

I am receiving date and time by CAN for my application, and not using the RTC functionality because I couldn't get it to work with LoRa.

Basically I receive day and month separately, and declare the year as a int. Same thing for the time, I receive hour, minutes and seconds separately.

Is there a way that I can join them into a timestamp variable?

[Tesla DeLorean]

>>Is there a way that I can join them into a timestamp variable?

Surely a relatively common math problem? Depends on the epoch you want to use and the resolution of time. You could look in the functions provided in time.h ?

mktime() ?

https://cplusplus.com/reference/ctime/mktime/

[Andrew Neil]

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@FPicc.1 wrote:

Is there a way that I can join them into a timestamp variable?

---

That gets complicated with having to cope with leap years, DST, etc - are you sure you really want to do that?

If you really must, look at mktime

https://en.cppreference.com/w/c/chrono/mktime

[Tesla DeLorean]

Time in seconds could then be counted off in Systick_Handler() after counting 1000 milli-seconds in the 1 KHz ticker.

[FPicc.1]

Saw this code at: https://os.mbed.com/questions/79859/How-can-I-convert-input-Date-Time-to-Uni/

time_t asUnixTime(int year, int mon, int mday, int hour, int min, int sec) {
    struct tm   t;
    t.tm_year = year - 1900;
    t.tm_mon =  mon - 1;        // convert to 0 based month
    t.tm_mday = mday;
    t.tm_hour = hour;
    t.tm_min = min;
    t.tm_sec = sec;
    t.tm_isdst = -1;            // Is Daylight saving time on? 1 = yes, 0 = no, -1 = unknown
 
    return mktime(&t);          // returns seconds elapsed since January 1, 1970 (begin of the Epoch)
}

 Could it work? Will test it later

[Andrew Neil]

Sure. That's using mktime - as I mentioned.

You'll have to check if it's implemented in the standard STM32 GCC release.

You'll still have to beware of DST ...

[Pavel A.]

> in the standard STM32 GCC release

That's in the newlib library for ARM & ST toolchains and proprietary libraries for IAR, Keil etc.