[USRP-users] Latency Through RF NoC on X310

Martin Braun martin.braun at ettus.com
Tue Apr 21 12:28:30 EDT 2015


On 21.04.2015 06:35, Johnathan Rodgers wrote:
> Hi,
> Is there an alternative solution to measure the minimum loopback latency
> in the fpga ?
> I tried to do as follow (radio0 --> radio1) with RFnoc in grc without
> any success : radio0 stays connected.

This is currently a known deficiency, we're on it.

Cheers,
Martin

> Thanks in advance.
> Johnathan
> 
> Le 19 mars 2015 23:28, "Martin Braun" <martin.braun at ettus.com
> <mailto:martin.braun at ettus.com>> a écrit :
> 
>     FG == flow graph (what GRC produces).
> 
>     What I mean is a flow graph such as this: http://imgur.com/LuBHfxp
> 
>     However, we just yesterday realized that if you do this, the Rx
>     radio won't be kicked off. We'll have a fix for that soon.
> 
>     Cheers,
>     M
> 
>     On 19.03.2015 14:53, Johnathan Rodgers wrote:
> 
>         Hi,
>         Martin, what do you mean by :
>         "To measure loopback latency, you'd need a simple GRC FG that
>         connects
>         the rx radio to the tx directly on the FPGA".
>         Is it a simple radio0 --> radio1 connection in Gnuradio with a
>         src/sink ?
>         What does FG mean ?
>         Thanks in advance.
>         Johnathan
> 
>         Nevermind again.
> 
>         On Wed, Mar 18, 2015 at 4:14 PM, John Malsbury
>         <jmalsbury.personal at gmail.com
>         <mailto:jmalsbury.personal at gmail.com>
>         <mailto:jmalsbury.personal at gmail.com
>         <mailto:jmalsbury.personal at gmail.com>>> wrote:
> 
>             "Traceback (most recent call last):
>                File "/home/jmalsbury/src/gr-ettus/build/top_block.py",
>         line 122,
>             in <module>
>                  tb = top_block()
>                File "/home/jmalsbury/src/gr-ettus/build/top_block.py",
>         line 63,
>             in __init__
>                  self.device3,
>                File
>            
>         "/usr/local/lib/python2.7/dist-packages/gnuradio/gr/hier_block2.py",
>             line 93, in __getattr__
>                  return getattr(self._impl, name)
>             AttributeError: 'top_block_sptr' object has no attribute
>         'device3'"
> 
>             Am I missing some device args?
> 
>             On Wed, Mar 18, 2015 at 4:07 PM, John Malsbury
>             <jmalsbury.personal at gmail.com
>         <mailto:jmalsbury.personal at gmail.com>
>         <mailto:jmalsbury.personal at gmail.com
>         <mailto:jmalsbury.personal at gmail.com>>>
>             wrote:
> 
>                 I'm blind.  disregard
> 
>                 On Wed, Mar 18, 2015 at 4:00 PM, John Malsbury
>                 <jmalsbury.personal at gmail.com
>         <mailto:jmalsbury.personal at gmail.com>
>                 <mailto:jmalsbury.personal at gmail.com
>         <mailto:jmalsbury.personal at gmail.com>>> wrote:
> 
>                     So... is there an RF NoC 101?  I've used the UHD
>         src/sink in
>                     the UHD->RF NoC category.  is there anything I need to
>                     specify to route from Rx/Radio0 to RxRadio1?
> 
>                     -John
> 
> 
> 
>                     On Fri, Mar 13, 2015 at 2:21 PM, Martin Braun via
>         USRP-users
>                     <usrp-users at lists.ettus.com
>         <mailto:usrp-users at lists.ettus.com>
>                     <mailto:usrp-users at lists.ettus.com
>         <mailto:usrp-users at lists.ettus.com>>> wrote:
> 
>                         Yes, you can reduce the 'spp' value. It defaults
>         to 364,
>                         because that's what fits into a standard MTU.
> 
>                         To measure loopback latency, you'd need a simple
>         GRC FG
>                         that connects the rx radio to the tx directly on the
>                         FPGA, and a scope or something to see the delay.
>         In GNU
>                         Radio, give the rx radio a stream arg value
>         'spp=20' or
>                         whatever. There may be limits to the size, and
>                         non-multiples of 64-bits won't do you any good
>         (2 sc16
>                         samples per line).
> 
>                         M
> 
> 
>                         On 13.03.2015 11:32, John Malsbury via
>         USRP-users wrote:
> 
>                             Are there any UHD tricks I might use to
>         stream the
>                             output of a radio
>                             block through RF NoC, directly to the other
>         radio
>                             block for re
>                             transmission, without any FPGA mods?  I
>         would like
>                             to test/measure the
>                             lowest delay possible across the rx
>         frontend, ADCs,
>                             RF NoC, DACs and tx
>                             frontend...
> 
>                             Are there knobs to tweak to reduce latency
>         across RF
>                             NoC (samples/frame
>                             or equivalent)?
> 
>                             -John
> 
> 
>                            
>         _________________________________________________
>                             USRP-users mailing list
>                             USRP-users at lists.ettus.com
>         <mailto:USRP-users at lists.ettus.com>
>                             <mailto:USRP-users at lists.ettus.com
>         <mailto:USRP-users at lists.ettus.com>>
>                            
>         http://lists.ettus.com/__mailman/listinfo/usrp-users___lists.ettus.com
>                            
>         <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com>
> 
> 
> 
>                         _________________________________________________
>                         USRP-users mailing list
>                         USRP-users at lists.ettus.com
>         <mailto:USRP-users at lists.ettus.com>
>                         <mailto:USRP-users at lists.ettus.com
>         <mailto:USRP-users at lists.ettus.com>>
>                        
>         http://lists.ettus.com/__mailman/listinfo/usrp-users___lists.ettus.com
>                        
>         <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com>
> 
> 
> 
> 
> 
> 
>         _______________________________________________
>         USRP-users mailing list
>         USRP-users at lists.ettus.com <mailto:USRP-users at lists.ettus.com>
>         <mailto:USRP-users at lists.ettus.com
>         <mailto:USRP-users at lists.ettus.com>>
>         http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
> 
> 





More information about the USRP-users mailing list