Re: [Discuss-gnuradio] UHD problem

[Josh Blum]

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,
-Josh

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
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