Re: [Discuss-gnuradio] UHD Announcement - July 6th 2010

[Josh Blum]

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: address@hidden
> > To: address@hidden
> > CC: address@hidden
> > 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
>                                         
> _________________________________________________________________
> http://clk.atdmt.com/UKM/go/197222280/direct/01/
> We want to hear all your funny, exciting and crazy Hotmail stories. Tell us now