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Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples
From: |
Josh Blum |
Subject: |
Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time? |
Date: |
Mon, 07 Jan 2013 17:08:34 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 |
On 01/07/2013 04:46 PM, LD Zhang wrote:
> Thanks to Josh and Marcus for their comments. The set_time_now command
> works! After I put it in, the earlier observed 0.5 sec offset between the 2
> USRP became ~0.1 second. So there is still work to do. I guess my options
> are:
>
> 1. Make the set_start_time command to work. My question is how I can make it
> work in python. I hand edited the set_time_now command to embed in the
> initialization part of the top_block.py code generated from GRC (which has
> worked). Do I just hand edit the set_start_time just following that command?
> Now the problem is that after set_time_now, the USRP time is sync'd to the
> system time. But what is the argument I should give to set_start_time?
>
Just a time in the near future that you can reasonably schedule in
advance of starting the flow graph. Like:
uhd.time_spec(time.time() + 0.5))
> 2. The other option is to get the metadata out for the samples collected.
> From what I read, it looks like one cannot do it in GRC, but have to edit
> the cpp source code. Is there an example somewhere of how this is done?
>
you can write a custom block in c++ or python to deal with tags
The most complete guide is here, but it requires installing grextras. I
think you can do this w/ more recent native gnuradio, but there isnt a
guide yet
https://github.com/guruofquality/grextras/wiki/Blocks-Coding-Guide#wiki-stream-tags
-josh
> Thanks very much,
>
> LD
>
> -----Original Message-----
> From: LD Zhang [mailto:address@hidden
> Sent: Friday, January 04, 2013 5:38 PM
> To: 'Marcus D. Leech'; 'address@hidden'
> Subject: RE: [Discuss-gnuradio] How do I capture of the time of USRP N210
> samples with host computer system time?
>
> Great! Thanks. I tried to import time and it works. Now I just have to see
> if this is sufficient for my sample gather timing or I still have to get the
> timestamp of the first sample using metadata and such.
>
> LD
>
> -----Original Message-----
> From: Marcus D. Leech [mailto:address@hidden
> Sent: Friday, January 04, 2013 4:15 PM
> To: LD Zhang; address@hidden
> Subject: Re: [Discuss-gnuradio] How do I capture of the time of USRP N210
> samples with host computer system time?
>
> On 01/04/2013 07:03 PM, LD Zhang wrote:
>> Hello,
>>
>> I tried the following command in python:
>>
>>> python:
>>> usrp_source.set_time_now(uhd.time_spec_t(time.time())
>>>
>> It doesn't seem to work. Looks like the "time.time()" is wrong? Looked
>> up an earlier example:
>>
>> set_time_now(uhd::time_spec_t(0.0), 0)
>>
>> The syntax looks different. But this may be doing something different
>> from my intention which is to sync the USRP time to the host system
>> time. I am still searching for the right syntax for this command. Any
>> help is appreciated.
>>
>> LD
>>
>>
>>
>> _______________________________________________
>> Discuss-gnuradio mailing list
>> address@hidden
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>>
> You'll have to put an:
>
> import time
>
> In your python
>
>
>
> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
>
>
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, (continued)
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, Josh Blum, 2013/01/04
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/04
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, Josh Blum, 2013/01/04
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/04
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, Josh Blum, 2013/01/04
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/04
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/04
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, Marcus D. Leech, 2013/01/04
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/04
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/07
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?,
Josh Blum <=
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, Marcus D. Leech, 2013/01/07
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/16
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, Josh Blum, 2013/01/16
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/16
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, Josh Blum, 2013/01/16
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/16
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, Josh Blum, 2013/01/16
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/17
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, Marcus D. Leech, 2013/01/16
- Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?, LD Zhang, 2013/01/17