Re: [Discuss-gnuradio] time to reconfigure a block in flowgraph

[Martin Braun]

On Thu, Dec 16, 2010 at 05:32:23PM -0800, Steve Mcmahon wrote:
> Hello:
> 
> I need some help on a timing issue.
> 
> I have a timer running on a separate thread which changes parameters in my 
> flow graph every 100ms or 200ms. When I change the frequency of my Signal 
> Source by using gr.sig_source_c.set_frequency(), the timer thread is still 
> able to fire every 100ms or 200ms and change the tone frequency every cycle. 
> However, when I try to also change the center frequency in the timer thread 
> with usrp2.sink_32fc.set_center_freq(), it cannot keep up and often takes 
> more than 100ms or 200ms.
> 
> How long do functions such as usrp2.sink_32fc.set_center_freq() take to 
> execute? Do I need to to gr.lock() and gr.unlock() my flowgraph before 
> changing these kind of parameters? How can I change parameters every 100ms?

Not the most general answer you can get, but if you want to do *precise*
retuning (e.g. for frequency hopping) to my best knowledge the way to go
is to use a larger bandwidth and do the tuning digitally. You don't have
to use lock() for retuning the usrp (just as you don't have to do so for
calling set_center_freq() on the sig_source).

Cheers,
MB

-- 
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin Braun
Research Associate

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KIT -- University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association

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