[USRP-users] Synchronised Recording across different systems (OpenMPI)

Matt Ettus matt at ettus.com
Thu Dec 11 02:05:42 EST 2014


Carel,

I don't have any experience with OpenMPI, but it sounds like that version
is slower and is thus sending the commands late.  Does it work if you don't
use timed commands?

Matt

On Wed, Dec 10, 2014 at 8:15 AM, Carel Combrink via USRP-users <
usrp-users at lists.ettus.com> wrote:

> Hi,
>
> I am trying to synchronise recording over different systems from different
> B210 devices. I have connected and set up the B210 devices to different
> NVIDIA Jetson TK1 boards.
>
> So to synchronise the recording I am trying to use OpenMPI, which I have
> set up and is working in principle.
>
> When I run the application distributed using OpenMPI I get the following
> error when starting to stream:
> ERROR_CODE_LATE_COMMAND
>
> My code flows as follow (extracts of relevant parts):
> -------------------
> usrp1 = uhd::usrp::multi_usrp::make(deviceArgs);
> usrp1->set_clock_source(std::string("internal"));
> /* ... more setup like freq and gain */
> usrp1->set_time_now(uhd::time_spec_t(0.0));
> hd::rx_streamer::sptr rxStream = usrp1->get_rx_stream(streamArgs);
> -------------------
>
> and then in a different thread:
> -------------------
> uhd::stream_cmd_t
> streamCommand(uhd::stream_cmd_t::STREAM_MODE_START_CONTINUOUS);
> streamCommand.stream_now = false;
> streamCommand.time_spec = uhd::time_spec_t(10);
> rxStream->issue_stream_cmd(streamCommand);
> rxStream->recv(buffPtrs, buffers.numberSamples, md, 10.1);
> --------------------
>
> If I print out the time of the metadata it is: 15.0048. This is almost
> always 5 seconds after the stream command that I set up.
> After the initial error I get ERROR_CODE_TIMEOUT without ever receiving
> data.
>
> As mentioned I am using OpenMPI, but when I run the same code on my device
> (TK1, not through OpenMPI but same executable) it goes through fine and I
> record perfectly.
>
> Are there anything that I am missing that would cause this to happen?
>
> PS: I am only using basic OpenMPI to start the apps remotely and to
> synchronise at some points, like before issuing the stream command. There
> are no synchronising between the apps after issuing the stream command. I
> have even removed all OpenMPI code from the application but the same
> problem exists.
>
> Regards,
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
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