[USRP-users] API change in UHD 3.9.1 for MIMO recv?

Dario Fertonani dario.fertonani at gmail.com
Thu Oct 1 14:05:06 EDT 2015

I'm upgrading to UHD 3.9.1 now that the B210 CODEC loopback bug is under

Did anything change in the API that initializes a two-antenna receive
stream? All our MIMO code stopped working.

I'm attaching a toy C++ code that does nothing but streaming and writing if
errors occurred while streaming. This code has worked since the 3.8.0 days
and now all of a sudden doesn't when the stream has two antennas. It dies
for ERROR_CODE_LATE_COMMAND even with a full second of margin (attached
version). It I raise that margin to 5 seconds, then it dies
for ERROR_CODE_TIMEOUT even if the timeout is raised to something
unrealistic like 10 seconds.

For anyone that can help, the compile/run instructions are in the first few
lines of the attached code. This version works on all our PCs that still
have UHD 3.8.5:

$ ./rxTest 739 4 2 1000 256

while it doesn't on the one that I just updated to UHD 3.9.1. On this one
though the single antenna version

$ ./rxTest 739 4 1 1000 256


I'm suspecting a subtle change in UHD. Maybe an init command that now is no
longer optional?

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