Re: [Discuss-gnuradio] selecting modulation dynamically

[Eric Blossom]

On Sat, Nov 18, 2006 at 03:34:25PM -0600, Shravan Rayanchu wrote:
> Hi all,
> 
> Is it possible to change the modulation scheme dynamically ? .. my
> understanding is that once the flow graph is built, it cannot be
> changed for the particular run of the program (correct me if I am
> wrong) .. so for example in transmit_path.py, once we select a
> modulation scheme, we are tied to it (although, it seems center
> frequency etc can be changed dynamically by calling usrp.tune ..)
> 
> So one way to change modulation scheme might be to have two parallel
> blocks in the flow graph (say one gmsk block and one dbpsk block) and
> select each one of them based on some parameter. Is this possible? I
> am not sure how to synchronize and decode correspondingly on the RX
> side though ...
> 
> Thanks much for the help,
> 
> --Shravan

Hi Shravan,

Right now changing the configuration of the flow graph is possible,
but because of how the existing hierarchical block code works, it is
broken for hierarchical blocks (which means most code).

The good news is that Johnathan Corgan is rewriting the hierarchical
block code so that hierarchical blocks are first class objects, and
that connecting and disconnecting pieces of the graph will _really_
work at runtime.  He's been making good progress on it, and I expect
to see it in the trunk in the not too distant future.

Eric