[USRP-users] FW: x310 2 twinrx sync channels issue

[Ilay Nissim via USRP-users]

Hi
We have a Setup with single x310 and 2 twinrx
We use Ubuntu 16.04
linux; GNU C++ version 5.4.0 20160609; Boost_105800; UHD_3.11.0.1-0-ga1b5c4ae
We have an Rx application
We sync all channels(ch0-3) to ch0 lo.
We use internal clock 1pps
We are trying to sample 4 channels,
each time for  a defined period of time,
Each time on a different frequency.
We have issues syncing the channels and get strange results calculating phase 
difference

Case 1:
We zero the time on each sample (not what we would ilke to do)
We than get the same phase difference  for a fixed frequency entered using a 
signal genrator


gDevice->usrp()->set_time_unknown_pps(uhd::time_spec_t(0.0));

uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_NUM_SAMPS_AND_DONE);

stream_cmd.num_samps   = streamLength;

stream_cmd.stream_now  = false;

stream_cmd.time_spec   =  uhd::time_spec_t(0.2);

rx_stream->issue_stream_cmd(stream_cmd);
case 2:

uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_NUM_SAMPS_AND_DONE);

stream_cmd.num_samps   = streamLength;

stream_cmd.stream_now  = false;

stream_cmd.time_spec   =  gDevice->usrp()->get_time_now() + 
uhd::time_spec_t(0.2);

rx_stream->issue_stream_cmd(stream_cmd);

on case 2 we get different phase phase difference  on each recording,
the phase difference is changing each time in +-(90/180/270)

can you explain ?
why does gDevice->usrp()->set_time_unknown_pps(uhd::time_spec_t(0.0))
need to get a fixed offset?

Why if we don't do it we get +-(90/180/270) degrees ?
This happens also if we wait for the next pps.


What we would like to d0
As soon as we get a command - try and sample a define times for all channels
This is done in a loop
Can this be done differently?  We tried continuous start stop with no success 
and also

Thanks
Ilay
Software Team Leader


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[USRP-users] RFNOC blocks with multiple inputs?

[Andrew Danowitz via USRP-users]

Hi all,

I'm trying to create an rfnoc divide block. I have the RTL and testbench
set up and working, but every time I try to put it in a grc flow, I get:

RuntimeError: Invalid stream args.

I'm assuming this has to do with the grc xml file for my block. Is there
any documentation on how to make an rfnoc block with multiple inputs or
outputs? For the make args, should I use the same ettus.rfnoc_generic call
that the built-in addsub block uses?

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