[USRP-users] Time of arrival of first sample in a 2 Rx setup

Marcus Müller marcus.mueller at ettus.com
Thu Apr 23 06:55:10 EDT 2015

Hello Siva,
recv() will do an aligned reception, i.e. the first samples of both
streams were received at the same time.

Often, you don't want to /know/ /afterwards/ the time of reception, you
want to /define/ it beforehand. You can do that by using a stream_cmd
with a stream_now = false and a timespec to allow you to define when the
reception is going to take place.


On 04/23/2015 12:28 PM, siva sankar via USRP-users wrote:
> Hello List,
> I am using USRP B210 and the UHD version is 003.008.000. We are
> transmitting on one channel and receiving simultaneously on both the
> channels and what we want is the time of arrival of the first sample
> in both the receive buffers. 
> We have used the "time_spec_t" to get the time of the first sample but
> we don't know if the time that we are getting is for both the channels
> or for one of the receiver buffers.
> We have tried using two "recv" commands one for each buffer hoping we
> could calculate the time from each metadata parameter passed to the
> "recv" command in one thread  but it throws "multi channel alignment"
> error and stops running.
> We also tried to create individual threads for both the rx channels
> and pass different metadata parameters and hence know the time of
> first sample for each buffer. However, this throws segmentation fault. 
> Any help on how to calculate the time of first sample for each receive
> buffer will be appreciated.
> Thanks
> Siva.
> _______________________________________________
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> USRP-users at lists.ettus.com
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