fl2k_test sample rate speeds up on Windows

Francesco Gugliuzza fgugliuzza.mail at gmail.com
Wed Oct 24 22:27:56 UTC 2018


Il giorno mar 23 ott 2018 alle ore 19:00 Steve Markgraf <steve at steve-m.de>
ha scritto:

> Hi,
> On 20.10.2018 02:20, Francesco Gugliuzza wrote:
> > I encountered this strange behavior when running fl2k_test on Windows 7:
> > basically after a while the sample rate drifts and speeds up
> > considerably. Sometimes it even starts up directly like that.
> Hm, I haven't seen this on Linux so far. Would be interesting to see if
> only the time measurement goes wrong (could be caused by CPU frequency
> scaling etc.), or if something is actually going wrong with the device
> or transfers.
My two cents is that something is up with the actual data transmission,
because I'm quite sure that the output signal gets corrupted or shifted out
of frequency. The CPU is set to maximum performance, but turbo boost could
effectively bring the frequency up by 200-300 MHz.
I'm on a laptop with an i7 4710HQ.

> fl2k_test outputs a rectangle signal, do you have an oscilloscope or an
> SDR you could use to check if the signal disappears when the measured
> sample rate starts to get strange?
Yes, I have a RTL-SDR, but I can't get my hands on it until next week. I
will update you when I will manage to perform some tests.
I can try on a live Linux distro if fl2k_test works correctly there,

> Regards,
> Steve
Thank you!


Francesco Gugliuzza
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