[USRP-users] gps_locked sensor throwing exception in latestmaster

Perelman Nathan (Nathan) nperelman at LGSInnovations.com
Thu Feb 7 10:54:09 EST 2013


Yes, I was querying the gps_servo (and gps_gpgga and gps_gprmc) sensors
as well. From my reading of the uhd code it looks like "SERV:TRAC 1" is
sent to the firefly on init though, not on the gps_servo sensor being
requested.
-Nathan


-----Original Message-----
From: USRP-users [mailto:usrp-users-bounces at lists.ettus.com] On Behalf
Of Josh Blum
Sent: Thursday, February 07, 2013 12:07 AM
To: usrp-users at lists.ettus.com
Subject: Re: [USRP-users] gps_locked sensor throwing exception in
latestmaster



On 02/06/2013 04:37 PM, Perelman Nathan (Nathan) wrote:
> In experimenting with the latest master and the addition of the 
> gps_servo sensor, I noticed some anomalies in the gps_locked sensor. 
> In my application I am asking for it every second or so to provide a 
> status output. Every so often it will print a warning three times and 
> then throw an exception similar to:
> 
> UHD Warning:
> 
>     locked: ValueError: Invalid response "$GPGGA,2113-02-06 5104 
> 108872
> 189.29 5"70E-12 15 15 6 0x0
> 
> terminate called after throwing an instance of 'uhd::value_error'
> 
>   what():  ValueError: Timeout after no valid message found
> 
>  
> 
> This will usually happen within 10 minutes of the gps locking. In 
> addition, the gps_locked sensor appears to sometimes return false even

> when the gps is locked (from looking at the nmea strings I can see 
> that it is actually locked). I can usually observe this at least once 
> within a minute of the gps locking the first time.
> 
>  
> 
> All testing was done with a USRP N210 r3 with a Jackson Labs GPSDO 
> installed.
> 

Are you also actually querying the gps_servo sensor? I just want to
confirm if enabling that was the cause of the error.

The gps_servo sensor is off until it queried (I believe). When its on it
tends to add a lot of extra serial traffic. Which isnt actually a lot
for the baud rate, but I think the micro inside the GPSDO might end up
overflowing a uart buffer, and causing the parser on the host to slip
up. Something like that...

-josh

> -Nathan
> 
> 
> 
> 
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> USRP-users at lists.ettus.com
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> 

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