[USRP-users] Rx/Tx Loopback

Marcus D. Leech mleech at ripnet.com
Wed Apr 1 23:38:07 EDT 2015


On 04/01/2015 11:35 PM, Rob Kossler wrote:
> ok.  I'll try that.  Thanks.
>
>
> Yes, the streams are going to the same physical device. But no 1 PPS 
> input.  My intention is to use X310 internal PPS.  I think the GRC UHD 
> sink/source setting for clock source is "default".  I'm assuming that 
> means internal PPS.
>
>
> On Wed, Apr 1, 2015 at 11:04 PM, Marcus D. Leech <mleech at ripnet.com 
> <mailto:mleech at ripnet.com>> wrote:
>
>     On 04/01/2015 11:00 PM, Rob Kossler wrote:
>>     I don't recall any error message with the low sample rate.  But,
>>     I was also using higher rates like 1 MS/s and 10 MS/s also.
>>     Rob
>>
>     May just be a buffering elasticity issue.
>
>     Try putting something like a multiply-const block between them,
>     with a constant of 1.0.  Just to put some buffering in place.
>
>     These streams are going to the same physical device, yes? And it
>     has a 1PPS input?
>
>
>
>>     On Wed, Apr 1, 2015 at 10:58 PM, Marcus D. Leech via USRP-users
>>     <usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>>
>>     wrote:
>>
>>         On 04/01/2015 05:57 PM, Rob Kossler via USRP-users wrote:
>>>         I would like to run a simple Rx to Tx loopback using
>>>         gnuradio companion with my X310.  The attached flowgraph
>>>         contains two blocks, a UHD source and UHD sink, which are
>>>         directly connected to each other on each of the 2 channels.
>>>
>>>         When I run it, I get numerous "L" indications.  To me, this
>>>         indicates that I'm not delivering the samples to the Tx
>>>         Streamer when it wants them.  Perhaps the start times for RX
>>>         streaming and TX streaming need to be specified?  If so, can
>>>         this be done from GRC?
>>>
>>>         Thanks.
>>>         Rob
>>>
>>>
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>>         The only thing I notice is that you've specified a really-low
>>         sample rate, one which I'm thinking the X310 cannot support,
>>         did you get any error messages
>>           to that effect when it's running.
>>
>>
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>>
>>
>
>
YOu have "don't sync" on the sink, and "unknown PPS" on the source.


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