Hi
Using USRP N210, UHD 3.2.1, windows7 (VC++ 9), GPSDO (Jackson Labs)
I first use :
get_mboard_sensor("gps_time")
set_time_next_pps(0, 1, 54000000)
Since gps time returns soon after pps edge occurs, I know that time is set
to 0 at a known GPS time called gps_t_0 (which is gps time returned by
sensor + 1)
(this is based on previous comments of Nick
http://lists.gnu.org/archive/html/discuss-gnuradio/2011-08/msg00097.html)
Then, I want to check that gps_t_0 is really my starting point, then I
discovered the bug
Here is pseudo code (in real code I use get_full_secs())
loop(){
//Sleep(3000)
gps_now = get_mboard_sensor("gps_time")
time_now = get_time_now()
if ((gps_now - gps_t_0) != time_now){
//NOT OK
std::cout << (gps_now - gps_t_0) - time_now
}
}
If there is no Sleep(3000), results are OK
If I enable the Sleep(3000), it prints at every loop iteration either -2 or
-3
If I change the sleep into Sleep(6000), it prints at every loop iteration -5
or -6
This means that query of gps_time is proportionally to Sleep(x) in the past
So I guess there is a problem of data flushing, the sensor query returning
first gps phrase generated by GPSDO since last gps_time query
A way to solve this bug may be to flush previous gps_time phrase generated
by GPSDO prior to get current time ??
Trying to dig into code (so far searching around get_nmea(...) in
gps_ctrl.cpp l.148), but not sure this can be solved in host code ??
Regards
Bastien
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