Re: [Discuss-gnuradio] USRP2 Sample 2.4 GHz Channel
Depending on how long you want to sample (and how much system RAM you've got) you can also do something like using tmpfs (i.e. a RAM disk). I've often resorted to this when doing collections lasting a minute or less. At 25MS/s * 32bit/S (Iq...@16bits) * 60s = 5.58GB according to my calculator - so that may or may not be a viable option for you. Doug On Thu, Sep 17, 2009 at 1:00 AM, Matt Ettus m...@ettus.com wrote: Miklos Christine wrote: Yes, that is exactly what I'm looking for. However, when running usrp2_rx_cfile.py with decimation = 4, I get a 'S' printing to stdout. Is anyone else able to run usrp2_rx_cfile.py and not get that overrun message? What could be the reason for 'S'? Is it a limitation on how fast we can write the samples to the hard disk? I want to keep the maximum number of samples possible. At a decimation rate of 4 you are generating 25 MS/s. If those samples are complex shorts, that works out to 100 MB/s. If those samples are complex floats, that is 200 MB/s. In the former case, you really need a RAID array of at least two fast drives to keep up. In the latter, you're going to need to do something more exotic. Matt -- Doug Geiger doug.gei...@bioradiation.net ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] USRP2 Sample 2.4 GHz Channel
Yes, that is exactly what I'm looking for. However, when running
usrp2_rx_cfile.py with decimation = 4, I get a 'S' printing to stdout. Is
anyone else able to run usrp2_rx_cfile.py and not get that overrun message?
What could be the reason for 'S'? Is it a limitation on how fast we can
write the samples to the hard disk?
I want to keep the maximum number of samples possible.
Thanks,
Miklos Christine
On Wed, Sep 16, 2009 at 6:52 AM, Douglas Geiger
doug.gei...@bioradiation.net wrote:
When you say sample the channel - are you trying to look at the IQ
samples coming right out of the USRP2? In which case, the easiest way
to start would be to use the usrp2_rx_cfile.py script, then you can
load the file into Matlab/Octave/etc. to take a look at. If you want
to record samples coming out of one of a block in the flowgraph (e.g.
in the 802.11b scripts) - you can modify the flowgraph to connect up a
file_sink at each point you want to record data from.
Doug
On Tue, Sep 15, 2009 at 9:41 PM, Miklos Christine
mchrist...@berkeley.edu wrote:
Hello,
I'm trying to sample the 802.11b wireless channels but the USRP2. I'm
currently using revision 10689 of Gnuradio.
I've added code to bbn_80211b_rx.py to connect the gr_probe_signal_f() to
the top block.
To sample the channel, I use gr.probe_signal_f().
Here's the code to connect the block:
self.connect(self.u, self.conv_c2f, self.probe2)
Then I use the gr.probe_signal_f().level() to retrieve the signal in a
loop.
data_file = open('data.txt', 'w')
T1 = time.asctime()
while cs_samples 100:
CST = self.tb.probe_channel()
data_file.write(str(CST) + '\n')
cs_samples += 1
data_file.close()
T2 = time.asctime()
def probe_channel(self):
return self.probe2.level()
I was wondering if this is the fastest way to sample the channel from
python. When I compute how long this process takes, it appears that I can
get a sample every 8-9 microseconds, which seems a lot slower than what
the
USRP2 is built to do. Am I sampling the channel in an incorrect way?
I'm running this on a machine with a Intel Quad Q9650 @ 3GHz.
Thanks,
Miklos Christine
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Doug Geiger
doug.gei...@bioradiation.net
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Re: [Discuss-gnuradio] USRP2 Sample 2.4 GHz Channel
Miklos Christine wrote: Yes, that is exactly what I'm looking for. However, when running usrp2_rx_cfile.py with decimation = 4, I get a 'S' printing to stdout. Is anyone else able to run usrp2_rx_cfile.py and not get that overrun message? What could be the reason for 'S'? Is it a limitation on how fast we can write the samples to the hard disk? I want to keep the maximum number of samples possible. At a decimation rate of 4 you are generating 25 MS/s. If those samples are complex shorts, that works out to 100 MB/s. If those samples are complex floats, that is 200 MB/s. In the former case, you really need a RAID array of at least two fast drives to keep up. In the latter, you're going to need to do something more exotic. Matt ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
