I pushed some changes to the uhd master that will check the deviation on
the times between boards. This should help you to debug your setup. If
you see an error message like the following, then you may have an issue
with the configuration. In the following example, I disconnected the PPS
on one of the boards. This is the result:
Set time with unknown pps edge:
1) set times next pps (race condition)
2) catch seconds rollover at pps edge
3) set times next pps (synchronously)
Error: time deviation between board 1 and board 0.
Board 0 time is 0.008782 seconds.
Board 1 time is 65.009945 seconds.
gr_block_executor: source <gr_block uhd mimo source (3)> produced no
output. We're marking it DONE.
-Josh
On 07/12/2010 07:14 AM, Zohair M. Abu Shaban wrote:
Dear Josh,
Thanks for the info provided and the help.
I
have 4 USRP2 boards, 2 separate function generators and 2 splitters to
supply PPS and REF clock with specs as in the FAQ page. For testing
only, I used a VRT version of the firmware that my colleague modified
to send the REF clock to the debug pins, and I was able to see that the
ref clocks are synchronized.
I tried to work with 2 channels, 3 channels and 4 channels and wasn't lucky
enough to get something working.
I am also interested to know if anybody has tried the MIMO block and got it
working/not working.
Best regards,
zohair
Date: Fri, 9 Jul 2010 09:18:24 -0700
From: j...@joshknows.com
To: zohair...@hotmail.com
CC: discuss-gnuradio@gnu.org
Subject: Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010
3) set times next pps (synchronously)
gr_block_executor: source<gr_block uhd mimo source (1)> produced no
output. We're marking it DONE.
This tells me that the alignment buffer is not finding a common
timestamp among the 4 channels or one or more channels is not streaming
(perhaps a timestamp/setup issue). What does your setup look like, is
there a common pps and common reference split 4X to each usrp2? I forgot
to add it to the notes but each device should have a common ref and pps
attached to its front panel. Also, can you try to run with just two
usrp2 to simplify the problem, does it work with 2 but not 3, 3 but not
4...?
Sometimes I also receive these errors that disappear when I power cycle
the USRP2's:
Error (usrp2 recv pirate loop): bad vrt header or unsupported packet type
Error (usrp2 recv pirate loop): assertion failed: if_packet_info.has_tsi
and if_packet_info.has_tsf
in void
usrp2_impl::io_impl::recv_pirate_loop(boost::shared_ptr<uhd::transport::zero_copy_if>,
boost::shared_ptr<usrp2_mboard_impl>, size_t)
at /home/dave/uhd/host/lib/usrp/usrp2/io_impl.cpp:97
Because the previous run did not exit cleanly and stop streaming, the
recv loop is catching the middle of a packet from the previous run. This
is safe to ignore.
-Josh
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