Re: [Discuss-gnuradio] UHD - Tx still transmitting

[Marcus D. Leech]

> I believe you have to make sure that "end-of-burst" is set and wait for an ACK 
> from the USRP. This allows the FPGA buffers to clear, at which point you should be able 
> to start RX. Someone please correct me if I'm wrong :)
>
> Sean
Yup.  In .../uhd/examples/tx_burst.cpp

Shows how this is done using the raw UHD interface (not mediated by Gnu 
Radio).

There are latencies involved in many parts of the "stack", so if you 
want to know that it's safe to
  start receiving, you have to wait for the End-Of-Burst ACK.  When you 
"->send()" a lump of data
  in UHD, when that send completes, it only means that the OS kernel 
has accepted the data.  It doesn't
  mean that the ethernet interface has transmitted, or that the other 
end has finished receiving it, or that
  the FPGA is finished with it and the last sample has left the DAC. 
 That's what the EOB-ACK protocol is
  about.


--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org