On Wed, 21 Mar 2012 21:23:39 +0800 (CST), Fengzhu FengzhuYe wrote:


> Hi, 
> I have bought two gpsdos and install them to my usrp n210.
Then I congfiured them step by step according to the following link
provided by ettus LLC
http://files.ettus.com/uhd_docs/manual/html/gpsdo.html. 
> After all the
things had done, I tried to retrieve the current GPS time by the
"gps_time" sensor using the codes : "
usrp->get_mboard_sensor("gps_time") ". The 
> compilation is ok and I
executived the program. Then an unexpected LookupError occured : 
> 
>
Error: LookupError: Path not found in tree: /mboards/0/sensors/gps_time

> 
> I printed all sensor list and there are only two sensor
"mimo_locked", "ref_locked". So I thought that means The gpsdo was not
properly set so that the usrp didn't find any "gps_time" sensors. But
when I executived the program "test_pps_input" at
/usr/local/share/uhd/example. The pps seens all right. That means the
gpsdo is ok. What's more, when I used the reference sources provided by
an external GPSDO by the code : 
> usrp->set_clock_source("external");

> usrp->set_time_source("external"); 
> It work well too. 
> 
> Now I
am confused . why is that happen? Was my gpsdo broken? All the two
gpsdos have the same LookupError. 
> 
> Thanks for your help.

Did you
do the post-installation task:


http://files.ettus.com/uhd_docs/manual/html/gpsdo.html#post-installation-task-n-series-only


Also, the "gps_time" is only available once the GPSDO is locked to a
GPS satellite constellation--that's where it gets the time from (and the
phase reference!). 

  
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