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Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010
From: |
Zohair |
Subject: |
Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010 |
Date: |
Tue, 27 Jul 2010 10:24:29 -0700 (PDT) |
Hi Josh,
Just a quick note. I don't use ctrl+c to kill the graph. Instead I use the
kill button ( or F7).. Thanks again for the info provided.
Regards,
Zohair
Josh Blum-2 wrote:
>
>
>> It's working now! I changed it to 50ms instead of 10 and added the lines
>> in
>> the synchronisation for loop in mimo_usrp.cpp to see the amount of
>> deviation
>> between usrps if they are synchronised:
>>
>> float diff=(time_i.get_real_secs() - time_0.get_real_secs())*1000;
>> std::cerr<< boost::format("Time was reset successfully for board %d with
>> deviation: %f ms relative to board 0")
>> % i %diff<< std::endl;
>> The output is:
>> Set time with unknown pps edge:
>> 1) set times next pps (race condition)
>> 2) catch seconds rollover at pps edge
>> 3) set times next pps (synchronously)
>> Time was reset successfully for board 1 with deviation: 1.095390 ms
>> relative
>> to board 0
>> Time was reset successfully for board 2 with deviation: 1.093340 ms
>> relative
>> to board 0
>> Time was reset successfully for board 3 with deviation: 1.096530 ms
>> relative
>> to board 0
>>
>
> Your seeing the RTT between requests for the timestamp, since it is
> working, the actual deviation is 0 and your boards are synced.
>
> Thats why the test above is really just a sanity check to ensure that
> the boards are not too far off (which otherwise implies that the
> synchronization failed).
>
>> However, I still have a few questions:
>> 1-Can't we make the deviation exactly zero? What factors affect this?
>>
>> 2- In my tries to run the flowgraphs, sometimes I receive these errors:
>> OError (usrp2 recv pirate loop): assertion failed: if_packet_info.has_tsi
>> and if_packet_info.has_tsf
>> in void
>> usrp2_impl::io_impl::recv_pirate_loop(boost::shared_ptr<uhd::transport::zero_copy_if>,
>> boost::shared_ptr<usrp2_mboard_impl>, size_t)
>> at /home/dave/uhd/host/lib/usrp/usrp2/io_impl.cpp:106
>>
>> you told me before it's save to neglect these errors but when i neglect
>> them
>> I receive rubbish data not what I am expecting, despite the fact that
>> boards
>> indeed synchronised. These errors disappear when I power cycle the USRPs.
>> Is
>> there anything I can do about this?
>>
>
> If the setup does not shut down properly, some boards may be left
> streaming. When a board begins to receive again, it may get partial
> packets and recognize them as junk. You can ignore the warnings.
>
> When you close the flowgraph does the application exit nicely or do you
> have to control+C?
>
> personal todo list: clean out the udp recv buffer chain on initialization
>
>> 3- Also, sometimes a number of "O" characters get printed on the screen,
>> what does this mean?
>>
>
> overflow, in the case of the usrp2, there is overflow in the socket
> buffer, packets are dropped, and the uhd driver noticed a discrepancy in
> the progression of sequence numbers and prints "O"
>
>> 4- What is the least sampling freq that I can use?
>>
>
> actual sample rates achievable by the hardware are 100e6 divided by
> //_USRP2_RATES = range(4, 128+1, 1) + range(130, 256+1, 2) + range(260,
> 512+1, 4)
>
> so the smallest rate is 100e6/512 = 195312.5 Hz
>
>> I am so glad that we have got something working now and Thank you very
>> much
>> indeed.
>>
>
> glad to hear it too, i will fix the mimo source with a timeout
> proportional to the number of channels
>
> -Josh
>
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>
>
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- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010, (continued)
- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010, Josh Blum, 2010/07/09
- RE: [Discuss-gnuradio] UHD Announcement - July 6th 2010, Zohair M. Abu Shaban, 2010/07/12
- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010, Josh Blum, 2010/07/12
- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010, Zohair, 2010/07/21
- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010, Josh Blum, 2010/07/21
- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010, Zohair, 2010/07/26
- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010, Zohair, 2010/07/26
- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010, Josh Blum, 2010/07/27
- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010, Zohair, 2010/07/27
- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010, Josh Blum, 2010/07/27
- Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010,
Zohair <=