[Discuss-gnuradio] USRP2 VRT support

[Josh Blum]

Folks,

There has been much work in the past few months to get the VITA Radio
Transport (VRT) protocol working with the USRP2. You can read more about
the protocol here: http://www.digitalif.org/

The branch containing this work can be found on my usrp2_vrt branch:
http://gnuradio.org/cgit/jblum.git/log/?h=usrp2_vrt

These changes will break the current usrp2 api. If you are just using
the gr-usrp blocks in your python apps, there should be no difference.
However, users making C++ calls to the usrp2 should expect to see some
changes:

The channel numbers and metadata for the transmit and receive methods
have been replaced with the vrt::expanded header. Documentation for this
can be found in vrt/include/vrt/expanded_header.h Examples of how to use
the expanded header w/ api can be found in the usrp2/apps directory.
This new api should give users greater control over timestamped data. We
apologize for breaking the api, but this is an important step in the
right direction.

Note: The usrp2 is still using raw ethernet frames. Hence, the vita
packets are going over raw ethernet. udp support for the usrp2 is coming
soon.

It would be greatly appreciated if usrp2 users out there would try out
the branch and send us your bug reports and feedback. The usrp2 vita
code should be merged into the mainline within a few weeks, and your
feedback will help us greatly.

To use this branch with the usrp2, users must burn new firmware and fpga
images to their usrps2's sd card. The images can be found here:
http://www.ettus.com/usrp2_vrt

Thanks,
-Josh