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

From: George Nychis
Subject: Re: [Discuss-gnuradio] Re: Simultaneously transmitting on two transmitters
Date: Fri, 07 Mar 2008 15:54:13 -0500
User-agent: Thunderbird (X11/20080227)

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

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