Problem with calling function once every x minutes

[setup: arduino uno ide 1.8.0, ethernet shield 2 poe, time sync router (which on sync external time provider), included libraries time.h , timelib.h]

hi all,

i trying figure out how have function being called once every 5 minutes, far result have been able achieve far cry need.

the code tinkering follows:

code: [select]

void loop()
{
 if (minute() - minute(t) >= 5)  //doesn't work: keeps running endlessly and
                                              //     not once every 5 minutes
{
 for(int = 0; < 1; i++)          //for should run once when condition
                     //within if met
{
 syncedtime();     // function testing with

/*alternative testing code
 serial.print(minute());     // returns current minute correctly
 serial.println();
 serial.print(minute(t));     // returns zeroes, , hence not the
                                           // minute 1 expects now();
serial.println();
*/

}
time_t t = now();

}

}

with call function syncedtime() enabled, result:

waiting sync fritz!box...

transmit ntp request
received ntp response

fritz!box has set system time!

 [22:02:00 / 05-01-2017]

[22:02:00 / 05-01-2017]

[22:02:00 / 05-01-2017]

[22:02:00 / 05-01-2017]

[22:02:01 / 05-01-2017]

[22:02:01 / 05-01-2017]

[22:02:01 / 05-01-2017]

[22:02:01 / 05-01-2017]

etc. etc.

instead of once every 2 minutes, specified, seeing numerous timestamps per second. when function call commented out, , serial.print lines activated, getting this:

waiting sync fritz!box...

transmit ntp request
received ntp response

fritz!box has set system time!

6
0
6
0
6
0
6

etc. etc.

where serial.print(minute()) correctly returns current minute, serial.print(minute(t)) returns zeroes. obviously, instruction time_t t = now(); doesn't expected do. stuck on one, appreciate leads me getting further.

thanking in advance time,

simon

can share minute() , now() functions?

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