Re: [Discuss-gnuradio] Re: Simultaneously transmitting on two transmitters

[George Nychis]

Sanmi wrote:

> 1) Using the m-block/inband timestamps: Using M-blocks, you can define
> timestamps that allow you to control when data is transmitted and
> appropriately synchronize RX. The m-block/inband code is still in
> development but is sufficiently stable to start some experiments. The
> m-block code is all in c++ and does not use gr-flowgraphs so you might have
> to build your application around it, or find some way to integrate m-blocks
> into your flowgraphs (hint: SWIG). The m-block code can also be used for
> many other functions (search the list for more details). Most of the code is
> available in the trunk.

The m-blocks will allow you to toy with everything you want at the host 
level, but the in-band code is what you need to get this information to 
the USRP.  The m-blocks are stable and in the trunk, the in-band code is 
still in development and we are NOT supporting it (please read on).

The host level in-band code is stable, I've been using it for several 
months now without a problem.  The FPGA in-band code is just wrapping 
up, I have two outstanding issues to fix: timestamp insertion and making 
the TX code a little more modular.  It will have support for dual RX and 
TX channels for which you can use a timestamp to synchronize.

The biggest missing piece in this architecture is the standard GR block 
to m-block connection, this is severely limiting and would force you to 
use an abundance of nasty SWIG hacks to use the standard GR library with 
your code.  When I say nasty, I mean it.  I believe Eric is scheduled to 
work on this while he works on the multi-threaded scheduler within the 
next week or two (I hope!).

Until then, I'd strongly advise waiting the extra time so I can wrap up 
the FPGA in-band code and Eric can wrap up the block connections.  It 
will save you tons of headaches, and we are not supporting the in-band 
code until then.  AKA, you can't come to us with your problems and we 
won't help you use it ;)

So in summary, GNU Radio will support exactly what you need to do 
through m-blocks and the in-band code, its just not quite there yet.

- George