# Uhd problem

**URL:** <https://www.ruby-forum.com/t/uhd-problem/190151>\
**Category:** GNU Radio\
**Created:** [June 17, 2010, 10:38am UTC](https://www.ruby-forum.com/t/uhd-problem/190151 "2010-06-17T10:38:36Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![dynamic](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dynamic](https://www.ruby-forum.com/u/dynamic)\
**Post date:** [June 17, 2010, 10:38am UTC](https://www.ruby-forum.com/t/uhd-problem/190151/1 "2010-06-17T10:38:36Z")

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Hi,

I’m a french student. I am working on UHD for the time-stamping on USRP2  
with a WBX dboard for my final project.  
I try to implement a specification on a usrp2.

I got a problem.

if someone can help me please:

when I use a switch with my usrp2 the system work but my bursts are  
wrong.  
(I tuned tx\_timed\_samples with a while loop to repeat burst with a tuned  
delay between 2 bursts )

When I use my usrp2 directly on my host pc the burst are good but I can  
send packet of 4449 samples max. if I send more samples, it give me an  
error after 1 or 2 burst(Error: no usrp2 controle response) and with  
burst under 4449 samples if I tune seconde or nseconde in the future, I  
got the same problem. it can work with a delay of 100000000 ns in the  
future.

I think I have a problem with my host Pc configuration (Ethernet or  
somethink like that.)

Can someone help me to fixe this or explain me what i’m doing wrong.

( Sorry for my approximate english )

many thanks!

Mourad

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**Author:** ![dynamic](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dynamic](https://www.ruby-forum.com/u/dynamic)\
**Post date:** [December 14, 2011, 11:26am UTC](https://www.ruby-forum.com/t/uhd-problem/190151/2 "2011-12-14T11:26:03Z")

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hi nick,  
thanks for your reply  
i tried the same command line arguments you gave me but the problem  
that there is always an under run error even if i change the args i  
tried several combinations but none of them worked  
any suggestions about that underrun problem

thanks,

osama

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**Author:** ![dynamic](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dynamic](https://www.ruby-forum.com/u/dynamic)\
**Post date:** [December 14, 2011, 11:32am UTC](https://www.ruby-forum.com/t/uhd-problem/190151/3 "2011-12-14T11:32:51Z")

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On 12/13/2011 09:02 AM, osama mohamed wrote:

> hi nick, thanks for your reply i tried the same command line  
> arguments you gave me but the problem that there is always an under  
> run error even if i change the args i tried several combinations but  
> none of them worked any suggestions about that underrun problem

So, its entirely possible that you are seeing the result of the CPU  
ramping up, or the kernel/usb drivers optimizing interrupts. Which means  
that you may get some initial underflow with USRP1.

Some initial underflow is not an issue if you plan to use USRP1 for  
continuous transmission. The problem would be continuous underflow,  
which means your computer + application cannot produce data fast enough.

-Josh

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<div class="post-metadata">

**Author:** ![dynamic](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dynamic](https://www.ruby-forum.com/u/dynamic)\
**Post date:** [December 14, 2011, 12:38pm UTC](https://www.ruby-forum.com/t/uhd-problem/190151/4 "2011-12-14T12:38:35Z")

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Try dropping the sample rate even lower–1Msps?

Is it perhaps  
possible that the device is plugged in to a USB-1.1 port, rather than a  
USB-2.0 port?

On Tue, 13 Dec 2011 10:30:03 -0800, Nick F. wrote:

> Like Josh said, one or two "U"s isn’t a big deal, but is it

underflowing constantly? That would be strange.

> Are you looking at  
> the output on an oscilloscope?

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<div class="post-metadata">

**Author:** ![dynamic](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dynamic](https://www.ruby-forum.com/u/dynamic)\
**Post date:** [December 14, 2011, 12:33pm UTC](https://www.ruby-forum.com/t/uhd-problem/190151/5 "2011-12-14T12:33:38Z")

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Like Josh said, one or two "U"s isn’t a big deal, but is it  
underflowing constantly? That would be strange.

Are you looking at the output on an oscilloscope?