[USRP-users] rx_samples_to_file issue
Marcus D. Leech
mleech at ripnet.com
Thu Oct 2 08:20:55 EDT 2014
> with rx_samples_to_file without _4rx.rbf, Initially I tried on my i3,
> 4GB ram, it gave me
> some OOOO but was lesser than earlier, but I do not understand, my
> most of the ram capacity and processor was sitting idle while it shows
> OOOO, why is this strange behaviour
The default format for uhd_rx_cfile is complex-float, thus doubling the
amount of data written compared to rx_samples_to_file.
You can't just use CPU usage as an indicator of loading--if you're
writing to disk, the disk subsystem may be much slower than you think,
"rate limiting step" is writes to the disk, not computational elements.
Try using /dev/null as the file that you write to. If the 'O' go away,
even at higher sampling rates, then it's your disk subsystem.
> using uhd_rx_cfile getting similar result, but strangely, why it is
> low, at 4M sampling rate it was higher???
> On Thu, Oct 2, 2014 at 9:27 AM, Marcus D. Leech <mleech at ripnet.com
> <mailto:mleech at ripnet.com>> wrote:
> On 10/01/2014 11:46 PM, gsmandvoip wrote:
>> Yes I am running single channel, but when trying to achieve my
>> desired sampling rate without _4rx.rbf, it says, requested
>> sampling rate is not valid, adjusting to some 3.9M or so.
>> sorry for misleading info I gave earlier, I have i3, with 32 bit
>> and i7 with 64 bit, but getting same result on both machines
>> Here is my command to capture signal:
>> ./rx_samples_to_file --args="fpga=usrp1_fpga_4rx.rbf,
>> subdev=DBSRX" --freq "$FC" --rate="$SR" $FILE --nsamps "$NSAMPLES"
>> and here is its output:
>> Creating the usrp device with: fpga=usrp1_fpga_4rx.rbf,
>> -- Loading firmware image: /usr/share/uhd/images/usrp1_fw.ihx... done
>> -- Opening a USRP1 device...
>> -- Loading FPGA image:
>> /usr/share/uhd/images/usrp1_fpga_4rx.rbf... done
>> -- Using FPGA clock rate of 52.000000MHz...
>> *Error: LookupError: IndexError:
>> multi_usrp::get_tx_subdev_spec(0) failed to make default spec -
>> ValueError: The subdevice specification "A:0" is too long.*
>> The user specified 1 channels, but there are only 0 tx dsps on
>> mboard 0.
> Don't use the _4rx image if you don't need it.
> The USRP1 only does strict-integer resampling, and with a master
> clock (NON STANDARD FOR USRP1) of 52.000MHz, 4Msps is not a sample
> that it can produce. Try 5.2Msps or 4.3333Msps.
> At 5.2Msps, it's recording at roughly 20.8Mbytes/second, so your
> system needs to be able to sustain that for at least as long as
> the capture lasts.
Shirleys Bay Radio Astronomy Consortium
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