[USRP-users] Receive two channels on the B210 with different sample rates

Marcus D. Leech mleech at ripnet.com
Wed Apr 22 14:05:35 EDT 2015


On 03/17/2015 01:55 PM, Hunter DeJarnette wrote:
> Marcus,
>
> Thanks for your quick reply.  Is this supported on other USRP models?  
> Are there any plans for this to be supported on the B210?
>
> Hunter
No, there's no support for this in other models, either.  While it's 
conceptually possible, it isn't actually implemented, partially because 
there's
   no way to setup the master clock (on, for example, the X310) in cases 
where there's no common master-clock rate that can produce both
   sample rates.

The best approach is to bring both streams in at the same rate, and 
resample the lower-rate stream.  If you use Gnu Radio, there are various
   resamplers, including a rational and fractional resampler.


>
> On Tue, Mar 17, 2015 at 12:51 PM, <mleech at ripnet.com 
> <mailto:mleech at ripnet.com>> wrote:
>
>     This is not a supported configuration on the B210.
>
>     If you need different sample-rates on the two streams, you'll have
>     to re-sample in software.
>
>     On 2015-03-17 12:12, Hunter DeJarnette via USRP-users wrote:
>
>>     I'm working on an application with the B210 where I would like to
>>     use both rx dsp's, but at different sample rates. I understand
>>     that each of the channels attached to a single rx_streamer must
>>     have the same sample rate. So to get around this issue I tried
>>     instantiating two usrp sources each with a different channel like
>>     so:
>>
>>             self.uhd_usrp_source_0 = uhd.usrp_source(
>>                 ",".join(("type=b200", "")),
>>                 uhd.stream_args(
>>                     cpu_format="fc32",
>>                     channels=[0],
>>                 ),
>>             )
>>             self.uhd_usrp_source_1 = uhd.usrp_source(
>>                 ",".join(("type=b200", "")),
>>                 uhd.stream_args(
>>                     cpu_format="fc32",
>>                     channels=[1],
>>                 ),
>>             )
>>     self.uhd_usrp_source_0.set_subdev_spec("A:A A:B", 0)
>>     self.uhd_usrp_source_0.set_samp_rate(samp_rate_0)
>>     self.uhd_usrp_source_1.set_samp_rate(samp_rate_1)
>>
>>     I found that when the sample rates for the two sources are the
>>     same I get similar performance to the using two channels on a
>>     single usrp_source. However, when I try to use different sample
>>     rates I start dropping samples. Am I setting this up right?
>>
>>     Thanks,
>>
>>     Hunter
>>
>>     _______________________________________________
>>     USRP-users mailing list
>>     USRP-users at lists.ettus.com  <mailto:USRP-users at lists.ettus.com>
>>     http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>

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