fl2k_test sample rate speeds up on Windows

Francesco Gugliuzza fgugliuzza.mail at gmail.com
Fri Nov 2 21:36:20 UTC 2018


I have to start with an errata corrige: my laptop has Windows 8.1 and not
7, which is installed on another computer.
Anyway, I've done some tests with a RTL-SDR, and I can definitely say that
something goes wrong. When I start the rtl-test sometimes a peak appears at
the correct frequency (e.g. if i set sampling at 100 MHz i find a peak at
3*100 - 50 = 250 MHz) and then disappears less than a second after; most
times it doesn't even appear at all.

I've also tried running fl2k_test on Linux with a live DVD of Ubuntu 18.10
and everything seems to go well: it runs correctly even at high sample
rates (150 MS/s), spewing out just an error on zero-copy buffers. Here is a
log:
ubuntu at ubuntu:~/osmo-fl2k$ fl2k_test -s 150e6
Allocating 6 zero-copy buffers
libusb: error [op_dev_mem_alloc] alloc dev mem failed errno 12
Failed to allocate zero-copy buffer for transfer 4
Falling back to buffers in userspace
Reporting PPM error measurement every 10 seconds...
Press ^C after a few minutes.
real sample rate: 149990146 current PPM: -66 cumulative PPM: -66
real sample rate: 150001491 current PPM: 10 cumulative PPM: -28
real sample rate: 150009752 current PPM: 65 cumulative PPM: 3
real sample rate: 149996142 current PPM: -26 cumulative PPM: -4
real sample rate: 150012666 current PPM: 84 cumulative PPM: 14
real sample rate: 150001814 current PPM: 12 cumulative PPM: 14
real sample rate: 150003433 current PPM: 23 cumulative PPM: 15
real sample rate: 149999114 current PPM: -6 cumulative PPM: 12
real sample rate: 149999349 current PPM: -4 cumulative PPM: 10
real sample rate: 150014477 current PPM: 97 cumulative PPM: 19
real sample rate: 149995547 current PPM: -30 cumulative PPM: 15
real sample rate: 150008611 current PPM: 57 cumulative PPM: 18
real sample rate: 149994234 current PPM: -38 cumulative PPM: 14
real sample rate: 150004040 current PPM: 27 cumulative PPM: 15
real sample rate: 150011047 current PPM: 74 cumulative PPM: 19
real sample rate: 149990169 current PPM: -66 cumulative PPM: 13
real sample rate: 150008286 current PPM: 55 cumulative PPM: 16
real sample rate: 149999384 current PPM: -4 cumulative PPM: 15

Using my RTL-SDR I find the peak at 3*150 - 75 = 375 MHz, as expected.

I will run some other tests on my other computer, the one with Windows 7.

Have a nice evening,
Francesco

-- 
Francesco Gugliuzza
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osmocom.org/pipermail/osmocom-sdr/attachments/20181102/29a26a1d/attachment.html>


More information about the osmocom-sdr mailing list