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Re: [Discuss-gnuradio] How to get time from GPSDO


From: Josh Blum
Subject: Re: [Discuss-gnuradio] How to get time from GPSDO
Date: Fri, 17 Feb 2012 10:22:32 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20111229 Thunderbird/9.0


On 02/17/2012 09:58 AM, Nowlan, Sean wrote:
> Just to enhance my (and everyone's) knowledge, does that call give
> you information substantially different from get_time_now()? Other
> than you get a UHD Time Spec with seconds and fractional seconds?
> 

Well, there is a time in the GPSDO in seconds that increments once a
PPS. Then there is a time in the FPGA that increments on each clock cycle.

Supposing you make a new uhd device object and a GPSDO is detected, the
time programmed into the FPGA registers is initialized to march in
lock-step with the GPSDO. This is done automatically, but its as simple
as ->set_time_next_pps(gpsdo_time + 1);

I wanted Wu to know that all the GPSDO sensors are available for access
in python. As in "gps_gpgsa", "gps_gprmc", and "gps_gpgga"

-Josh

> Sean
> 
> -----Original Message----- From:
> address@hidden
> [mailto:address@hidden
> On Behalf Of Josh Blum Sent: Friday, February 17, 2012 12:55 PM To:
> address@hidden Subject: Re: [Discuss-gnuradio] How to get
> time from GPSDO
> 
> 
>> 
>> and thought usrp->get_mboard_sensor is the function that I need.
>> But I don't know how to use this function in GNURadio. It seems
>> that the code is written in C++. So can I use it directly in
>> GNURadio?
>> 
>> 
> 
> All the functions are brought into python via swig, so: 
> http://gnuradio.org/cgit/gnuradio.git/tree/gr-uhd/include/gr_uhd_usrp_sink.h#n279
>
>  you would do this python: secs =
> the_usrp_block.get_mboard_sensor("gps_time").to_int()
> 
> -Josh
> 
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