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Re: [Discuss-gnuradio] UHD: trouble configuring multiple RX channels rel

From: Michael Dev
Subject: Re: [Discuss-gnuradio] UHD: trouble configuring multiple RX channels reliably
Date: Wed, 27 Apr 2011 22:10:23 -0700

Thanks for the fix.  I tested it on my USRP1 + 2 DBSRX system and it seems to work.
There are couple of remaining issue though.
1. The instability problem is still there.  If I keep restarting my app, USRP1 seems to come up in a state where I get either corrupted IQ signal (in what way, I don't know. Sometime lower SNR, sometimes flat garbage) or one of the initialization UHD calls (multi_usrp::make, set_rx_freq, etc) just hang and require device power cycle.  It doesn't take many trials to hit this state.  I don't have this issue when I use the gnuradio framework.  Note that I've been having this issue with E100 (w/ a RFX dboard) as well so I don't think it's a motherboard or DBSRX specific problem.
2. The latest UHD repository master (4/27) seems to have a serious regression for E100.  I get data samples coming in but expected signal is not there (or corrupted in serious way).  As I replied to you in another thread, I saw this happen also with the "usrp_e100_frame_size2" branch you posted for me on 4/26 and merged to the master today. In any case, my E100-friendly UHD git version is from 4/19, so it looks like the regression happened at some point between then and now.
For now I will use the latest master for my USRP1 and keep the old one for E100. :)

On Wed, Apr 27, 2011 at 1:25 PM, Josh Blum <address@hidden> wrote:

> It feels as though the subdev config in general is quite unstable
> for my multi-channel setup or my code is missing something very basic.  When
> I double check the freq and gain settings with the get functions, they all
> look fine though.
> Any insights?

It turns out that the RX mux was calculated in reverse. Effectively, the
channels were swapped. This would have been hard to notice on a pair of
boards with frac-N synthesizers, but with DBSRX, the DDC offset made it
noticeable. I pushed a fix to the master:



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