UHD: tx - sync via MIMO cable, rx - "We're marking it DONE"


Setup: Two USRP2 + WBX boards, one PC with Ubuntu 10.04, the latest
gnruadio/next and uhd from the github. The PC hosts two PCI express
GigEthernet cards, which are connected to the two USRP2s.

I’m using UHD to tx/tr with two boards simultaneously. I’m working
with Multi USRP source and sink from the GRC. I have two problems in
my examples:

  1. The tx part works except for the synchronization. I have a MIMO
    cable and I though about using it for that. However, it seems that
    Multi USRP sink does not see the cable. Is it possible to use this
    cable for sync purposes? Alternatively, is there a way to get rid of
    the one of the GigE cards and get the data through the mimo cable to
    the other device (I know that this is the original MIMO cable idea,
    it’s just that I haven’t heard about any successful attempts).

  2. The receiver gives me this nasty “We’re marking it DONE” error
    message, that a few people reported earlier. Before trying out some of
    the posted solutions, are there any solutions to the problem that do
    not require changing C code and recompiling the whole thing?



The mimo cable has not been addressed in UHD ATM. To receive from
multiple usrps in a synchronized manner, you will need to feed each PPS
and reference input appropriately according to the following docs:

In the flow graph, one of the blocks should be set to “sync on unknown
pps”. If the times across the usrps are not synchronized, then the
stream request will probably fail and the usrps will not stream in