1. Sync time

The problem is to synchronize time on bbb. My device, after power on, querry time from server and set up linux time:

system( "date 061621252015.42" );

But time(NULL) results UTC time (i think). Well, the answer is set TZ variable to UTC before setup time:

setenv("TZ", "UTC", 1);
system( dateCommand.c_str() );

Well, this is working propertly.

2. Drift? time

Almost ;)

This time lags about 10 min for 1 hour.

Experiment:

1. set hwclock from sysclock 
2. wait 30 minutes

Result: diff = 11 +- 2 sec

root@beaglebone:~# hwclock -u
Tue Jun 16 21:33:15 2015  0.000000 seconds
root@beaglebone:~# date
Tue Jun 16 21:33:04 UTC 2015

3. wait 55 min

Result: diff = 2:30 !!

root@beaglebone:~# date
Tue Jun 16 22:02:48 UTC 2015
root@beaglebone:~# hwclock -u
Tue Jun 16 22:05:32 2015  0.000000 seconds
root@beaglebone:~# date
Tue Jun 16 22:02:53 UTC 2015

Second question, Is hwclock show correct time?

I hope yes.

Experiment:

22:08:00

root@beaglebone:~# hwclock -u
Tue Jun 16 22:08:09 2015  0.000000 seconds

 

 

(My device is not use my time to sync, then 9sec is ok )

23:11:00

root@beaglebone:~# hwclock -u
Tue Jun 16 23:11:09 2015  0.000000 seconds