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List:       gnuradio-discuss
Subject:    RE: [Discuss-gnuradio] RE: Timestamp value
From:       Ulrika Uppman <ulrika.uppman () foi ! se>
Date:       2010-02-25 12:18:49
Message-ID: 2353D840E7D6904EB79324A7B7EE71F6A5938BD834 () EMS ! win ! foi ! se
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 Hello again, 
Just want to clear this out for anyone else who bumps in to this:
The solution is simple. The reason that the timestamps behaved strange in the 3.2 \
version is because of the byte reverse order of the timestamp when they are fetched \
from the pkt->hdrs.fixed.timestamp (I can't believe I didn't see this sooner ;) ). \
Running the timestamp through the ntohx-function made the values much clearer! If I \
take the difference between two received packets and divide by the decimation rate \
this will now always result in 371 as expected.

Best regards,
Ulrika

> -----Original Message-----
> From: discuss-gnuradio-bounces+ulrika.uppman=foi.se@gnu.org 
> [mailto:discuss-gnuradio-bounces+ulrika.uppman=foi.se@gnu.org]
> On Behalf Of Ulrika Uppman
> Sent: Tuesday, February 23, 2010 3:54 PM
> To: discuss-gnuradio@gnu.org
> Subject: RE: [Discuss-gnuradio] RE: Timestamp value
> 
> I have now finally managed to get the vrt code, the problem 
> was that I got the wrong address... Sorry :P
> 
> So lets get back to the main issue:
> 
> I now ran the vrt version and when I take the difference in 
> ticks between the packets and divide by the decimation rate, 
> the result is always 365. Seems more reasonable than the 
> results by the other versions, but I would still expect the 
> value to be 371 since samples_per_frame is set by default to 
> this value in rx_samples. Where does the value 365 come from?
> 
> This also brings me back to the question on the 3.2 stable 
> release which is the version of gnuradio that I am currently 
> using. In 3.2 the timestamps don't behave like the time ticks 
> (fractional time part) in the vrt version. (The behavior in 
> version 3.2 is described earlier in this thread 
> http://lists.gnu.org/archive/html/discuss-gnuradio/2010-02/msg
00343.html ) What is the difference else than the size (32 vs 64 > bits)?
> 
> What else could I do wrong to get such different behavior? 
> I use the firmware and fpga image from 
> http://gnuradio.org/releases/usrp2-bin/trunk/ and 
> http://www.ettus.com/usrp2_vrt for the two versions, and the 
> code is not touched except from the printouts.
> 
> Thanks for any hints.
> Regards,
> Ulrika
> 


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