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

[Martin]

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