Control time or number of points acquired

Hi all-

has anybody implemented a control whereby the user can limit how long or
how many points gets acquired by a gnuradio application? If so I’d
appreciate any pointers! I’ve got an app where I’m storing samples to
file and I’d like to control how many points go into each data file.

thanks,
eric


Eric H. Matlis, Ph.D.
Aerospace & Mechanical Engineering Dept.
120 Hessert Center for Aerospace Research
University of Notre Dame
Notre Dame, IN 46556-5684
Phone: (574) 631-6054
Fax: (574) 631-8355

On Sat, Dec 22, 2007 at 06:04:50PM -0500, [email protected] wrote:

Hi all-

has anybody implemented a control whereby the user can limit how long or
how many points gets acquired by a gnuradio application? If so I’d
appreciate any pointers! I’ve got an app where I’m storing samples to file
and I’d like to control how many points go into each data file.

thanks,
eric

Hi Eric,

We generally use gr.head for this.
See gr-utils/src/python/usrp_rx_cfile.py

Eric

You cannot do this continuously with any of the default blocks (to my
knowledge). But I have written a filesink a while back that chops the
data stream into files of specified size.

http://mep.fi/juha/gnuradio.html

I have used this for a couple of months and recorded terabytes of
baseband signals without any problems (I hate files that are 500GB,
that is why I wrote the block). But I still consider it to kind of
beta, so report any bugs that you find to me.

juha

Thanks Eric, Juha, and Michael-

to get 3 helpful responses within an hour of sending a post is truly
amazing, particularly considering the time of the year.

I should have elaborated in my post. I tried the gr.head approach, but
I’m not sure it works in my application- I’m using the approach of the
astronomy guys, with a control button that turns on and off from
/dev/null
to a file descriptor. So if I use gr.head, correct me if I’m wrong, but
I
believe it immediately sends the number of samples specified to
/dev/null.
I don’t think that way is compatible with the approach I’m using, which
I
ripped off from usrp_psr_receiver.py.

So you know what I’m doing, I’m using the USRP as a pseudo digital
oscilloscope with a capture to file option. When I see something I like
in the scope, I hit the “capture to file” button. It works great, but
currently I have to look at my watch to capture comparably sized
samples.

Perhaps there’s a way of incorporating a timed capture (or fixed number
of
samples to this model?

thanks again so much.

eric


Eric H. Matlis, Ph.D.
Aerospace & Mechanical Engineering Dept.
120 Hessert Center for Aerospace Research
University of Notre Dame
Notre Dame, IN 46556-5684
Phone: (574) 631-6054
Fax: (574) 631-8355

Here is a link to a small program I used for capturing to a file with a
given duration in seconds.

http://www.kd7lmo.net/ground_gnuradio_software.html

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