Re: [Discuss-gnuradio] *much* faster filtering --- plus vhf mountaintopping

[James Cooley]

I have successfully used an external USB 2 drive along with the usrp, no 
problems. And that's with a USB hub with USB2 drive as well as a GPS 
attached and spewing data. There's a trick, though.... compression. You 
can make a fifo, ask gnuradio to write to it, and zip it.

In one window, make the fifo and start it:

#> mkfifo testfifo
#> cat testfifo | gzip -c > data.gz

In another, start up the capture, something like this:

#> usrp_rx_file.py -o testfifo

THE reverse step is to unzip,, like this (for example, with the wfm script):

#> wfm_rcv_file.py testfifo

In the other window, do:
#> gzip -dcf data.gz > testfifo



Seems to work barely on my laptop, which is a 1.6 GHz pentium M 
machine.... HOWEVER, to aid things along even more, I did the captures 
without using X-windows (you don't need it if your not using any guis). 
You can switch consoles in linux with ctl-alt-Fx, where F7 is where your 
x-windows is running. I switched to a console, killed X, used one 
console for the usrp, the other for the piping and zipping.

How well did it work? I did a sweep of the entire front-end's range, 
about 40 minutes of sampling incrementing by 400kHz about every second 
from 50 Mhz to 860 MHz... this gave me a zipped file roughly 600MB.


For usrp source, complex samples, decim 8 (therefore, rate= 8Mbits/sec), 
this worked out well. By the way, Chuck, I think that if you're using a 
TVRX board, the downconverter 4937 has a 6 MHz bandwidth... so even 
though you captured at 8Mhz, don't you only have just 6 of useable data?


-jamie






Daniel O'Connor wrote:

> On Wed, 11 May 2005 21:43, Chuck Swiger wrote:
>  
>
> > for about 3 or 4 minutes each before filling up 20Gb free space. Still it's
> > nice to collect
> > field data for later slicing and dicing in the basement.
> >
> > Looking for faster/bigger portable storage. The Adaptec SlimSCSI 1480 card
> > will only do
> > 20MB/sec.
> >    
>
> If you can power a mains appliance (car inverter?) you could use an external 
> firewire drive.
>
> I doubt you could run a USB enclosure and the USRP without running out of USB 
> bandwidth but firewire should be OK.
>
> The enclosures I've used (Mapower) can keep up with WDxxxxJB drives which do 
> around 30-50Mbyte/sec.
>
>  
>
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