RE: [Discuss-gnuradio] RE: Timestamp value

[Ulrika Uppman]

 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: address@hidden 
> [mailto:address@hidden
>  On Behalf Of Ulrika Uppman
> Sent: Tuesday, February 23, 2010 3:54 PM
> To: address@hidden
> 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
>