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RE: [Discuss-gnuradio] UHD problem

From: Per Zetterberg
Subject: RE: [Discuss-gnuradio] UHD problem
Date: Thu, 15 Jul 2010 20:03:43 +0000

Two questions:

How large is the fpga buffer ?

Does this imply that it would be fairly straightforward for a FPGA-skilled 
person (i.e. not myself) to implement decimation=1 ?
I mean, not continous streaming, but using the FPGA to store short bursts.


From: address@hidden address@hidden on behalf of Josh Blum address@hidden
Sent: Thursday, July 15, 2010 9:40 PM
To: address@hidden
Subject: Re: [Discuss-gnuradio] UHD problem

You have done nothing wrong. This is a result of the transmit SM in the
FPGA using ethernet pause frames to flow control the transmit. The pause
frame is blocking the transaction from the issue stream command, and
causing the timeout error (no response).

Sending a large packet (greater than the fpga buffering) several seconds
in the future will cause the FPGA to issue these pause frames and it
will last for several seconds (until the transmit packets are processed).

Understanding that, it may be possible for you to work around this by
making the sends in the future sooner (within 100 ms). Or issue the
stream command before any sending occurs. In the long run, we are
working on a host based flow control to avoid using the pause frames.

Hope that helps,

On 07/15/2010 12:16 PM, Per Zetterberg wrote:
> Hi Josh and List,
> I am trying to send two frames and then receive a frame. The two transmit 
> frames are transmitted several seconds in advance using  d_dev->send. They 
> arrive nicely at the receiver as they should. However, then I try to receive 
> a frame  using "d_sdev->issue_stream_cmd(stream_cmd)" followed by 
> d_dev->recv. However, the command "d_sdev->issue_stream_cmd" gives the error 
> "usrp2 no control response".
> Could it be that when I do the command d_sdev->issue_stream_cmd the USPR2 is 
> busy waiting to transmit the two transmit frames ?
> BR/
> Per
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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