Some time back, I had an exchange on this list regarding how to configure an X300 to stream data from a TwinRX and LFRX daughterboard simultaneously. The previous thread is archived here:

http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2017-February/051672.html

Specifically, I would like to synchronously stream both TwinRX channels at 100 MSPS complex, while streaming both LFRX channels as a single 100 MSPS complex stream as well. To do that, I am:

- Creating three multi_usrp objects initialized with identical arguments, with the subdev specification "A:0 A:1 B:AB".

- Obtaining one rx_streamer object from each multi_usrp (passing a different channel number 0, 1, or 2 to each), then calling issue_stream_cmd() with stream_now = false and time_spec some time in the future (say 2 seconds away to ensure much more than enough time to finish setting up the stream). This should ensure that they all start streaming simultaneously so I get time-coincident samples

- Using the rx_streamer objects to receive data on each channel, use recv() to stream data in.

I have run this setup for over a year with no issues under UHD v3.10.3.0. I updated my application to use UHD v3.14.0.0 in order to get access to TwinRX bugfixes and more Ettus hardware support.

After the UHD upgrade, the above setup does not work. I do get data streaming from the 2 TwinRX channels at the desired rate, but I never get data from the LFRX. Instead, the first call to recv() in the thread that is reading the LFRX data returns ERROR_CODE_LATE_COMMAND, then the subsequent calls time out (I have the timeout set to 5 seconds).

Notably, if I set stream_now = true in the stream command, then I get data from all of the channels as expected at the desired rate. However, this method is incompatible with time alignment across channels, so it is not an option.

How can I get time-aligned streaming from TwinRX/LFRX working under UHD v3.14?

Thank you.

Jason


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