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:[email protected]] > Sent: Friday, January 04, 2013 5:38 PM > To: 'Marcus D. Leech'; '[email protected]' > 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:[email protected]] > Sent: Friday, January 04, 2013 4:15 PM > To: LD Zhang; [email protected] > 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 >> [email protected] >> 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 > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
