[Discuss-gnuradio] test_usrp_standard_tx, tx_underrun

[Mattias Kjellsson]

Hi list,

I have recently begun to see a lot of tx_underrun in my applications. At 
first I thought it was due to me not setting realtime- scheduling 
properly (which I did), then I thought it might have something to do 
with recent fusb_* updates from gnuradio (which it didn't, since I 
downgraded to  svn10527 (I did use svn10537) which used to did work). 
Then I thought it had something to do with me running to many other 
processes on the host computer, but that turned out to not make any 
changes either, since I closed all "unnecessary" processes (including 
gdm, Xorg and so forth). Then I thought it might have something to do 
with Dell cheeping out on the usb-2.0 ports, so I tried switching 
between the four of them between tests, but no luck there either...

To check for the underruns I use
"~/gnuradio/usrp/host/apps/test_usrp_standard_tx" (I tried it several 
times both as root and as user)
which is reporting ~40 underruns, and a throughput of about  29-30mb/s.

On the other hand, when I'm trying "test_usrp_standard_rx" it reports 0 
underruns and 32Mb/s throughput.

The peculiar thing is that code that is running fine on a Dell latitude 
e6400 with Ubuntu 8.10  and gnuradio svn10527 isn't running fine on a 
Dell latitude D630 running Ubuntu 8.10 and gnuradio svn10527. I know the 
Latitude e6400 should be a more "manly machine", but I think the D630 
should be able to handle "test_usrp_standard_tx" should it not? It has 
done so before at least...

I guess my question is, -"Is there anyone who has any clue why I see 
these underruns, and/or what I can try to make them go away?"


Best regards
//Mattias Kjellsson