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Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples


From: LD Zhang
Subject: Re: [Discuss-gnuradio] How do I capture of the time of USRP N210 samples with host computer system time?
Date: Wed, 16 Jan 2013 23:05:00 -0800

Hi,

 

This is a very useful input and it may very well explain the situation (some one has also suggested that NTP is not the right protocol for 1-2 ms accuracy. This is a separate problem from what we are discussing here) and the variability. There has been a growing dissatisfaction with the GRC generated python approach and I would like to move to the rx_sample_to_file command approach and start modifying the associated cpp files. Would you say that the performance will be more stable with the latter approach?

 

However, I don’t how to do the command line method. I suppose there would be many arguments given to the “rx_sample_to_file” command to make it do what I want. But the help menu info on this command is very limited, does not touch on needs with set_time_now and set_start_time parameters in the data gathering process. Basically I suppose if I can do the rx_sample_to_file command and correctly impose the set_time_now and set_start_time option,  there should be much less variability than the python approach. Does this look right?

 

Thanks,

 

LD

 
 

There's a profoundly-variable and "jittery" amount of time that it takes to start a Python interpreter and "get things going" between any two
  serial invocations on the *same machine*, let alone on two different machines.  They may well agree on what time it is (to a first order
  approximations) when they both say "go", but after that, I can easily imagine the behaviour to be not entirely deterministic.




-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

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