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From: | Marcus D. Leech |
Subject: | Re: [Discuss-gnuradio] UHD - Tx still transmitting |
Date: | Wed, 30 Nov 2011 21:49:10 -0500 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.24) Gecko/20111108 Fedora/3.1.16-1.fc14 Thunderbird/3.1.16 |
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.cppShows 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
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