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

Marcus D. Leech mleech at ripnet.com
Wed Apr 22 14:46:20 EDT 2015


On 04/22/2015 02:05 PM, Marcus D. Leech via USRP-users wrote:
> 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.
>
>
I was mis-lead by R&D, and have now been re-lead :)

On the *X310 in particular*, you can have two different sample rates 
from the two "sides" but those streams *must* be packaged inside
   separate multi_usrp objects,  and they both must, of course, satisfy 
the integer fraction rules with respect to the master clock rate.

The streams inside a multi-usrp object are required to be at the same 
sample-rate, because a multi-usrp "object" does sample time
   synchronization which is maximally awkward if the streams are running 
at two different rates....


>>
>> 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
>>
>>
>
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/attachments/20150422/2ea3d310/attachment-0002.html>


More information about the USRP-users mailing list