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
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