Re: [Discuss-gnuradio] timed dual channel B210 capture gives error "UHD source block got error code 0x2" (ERROR_CODE_LATE_COMMAND)

Small addition.
I just want to start capturing on both channels of a B210 at the exact
same time. I do not mind which time that is, as long as the samples are
aligned.

I have read a discussion on this mailinglist which made it clear that
you do need to set a start_time (timed_capturing) with dual-channel
capturing with a B210 to have both channels synchronized.
You should not set the internal B210 clock with set_time_now, since this
would set a slightly different time in the two different channels.
This would then result in a random clock misalignment betwen the
channels of up to 250 usec.

it was advised to use set_time_unknown_PPS or leave the time at the
default internal initiated time. This way both channels should have an
aligned internal clock.

Then using a start_time in the near future should result in perfectly
aligned captures. But as I said in my previous mail, this results (for
me) in the UHD error.
"UHD source block got error code 0x2"


Martin


On 22-02-15 21:53, Martin wrote:
> When you start a dual channel timed capture in the near future with a
> B210, the work method of usrp_source_impl.cc prints out
>
> "UHD source block got error code 0x2"
>
> error codes are defined in:
> metadata.hpp line 99:
> //! A stream command was issued in the past.
> ERROR_CODE_LATE_COMMAND = 0x2,
>
> No matter what starttime (in the future) was chosen, UHD always thinks a
> command is scheduled to be run in the past (too late)
>
> When I do the same with a single-channel script on the same B210
> everything works fine without errors.
>
>
> The dual channel always prints out the error, and the single channel
> always seems to work fine.
> I have tried different settings for the delay, which sets how long in
> the future the capture is set to start.
> But 0.1 0.2 1.0 2.0 5.0 seconds all seem to fail.
>
> I also tried with or without using 1 PPS to set the clock time, but that
> did not help either.
>
> code snippet:
>
> usrp_source_impl.cc
> line 663:
> switch(_metadata.error_code) {
> ...
> line 692:
> default:
> std::cout << boost::format("UHD source block got error code 0x%x")
> % _metadata.error_code << std::endl;
> return num_samps;
>
>
> I created an issue on gnuradio.org and attached example python scripts
> there to demonstrate the error. Dual channel script fails, single
> channel works.
> http://gnuradio.org/redmine/issues/769
> The defaults are fine for demonstrating the behaviour so you do not need
> to give any arguments.
> Note that I used a B210 with an embedded GPSDO, which might be important.
>
> It is also very possible that I am doing something very wrong.
> Please let me know.
>
>
> With best regards,
>
> Martin Dudok van Heel
>
> _______________________________________________
> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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