Librtlsdr zerocopy buffers not working on Tinkerboard Armbian

Carl Laufer admin at rtl-sdr.com
Mon Oct 1 03:42:11 UTC 2018


I've been trying to get some RTL-SDRs to function properly on my
Tinkerboard, running Armbian Bionic, Kernel 4.14y. I noticed that with the
Osmocom drivers rtl_test would result in huge sample drops (millions of
samples dropped each time). However, Keenerds branch did not drop any
samples, nor did the presumably older Osmocom drivers from apt-get.

I did a diff against Keenerds and discovered the new zerocopy buffer code
in the Osmocom drivers. After commenting that out, the Osmocom drivers work
fine on the Tinkerboard with Armbian and there is no sample loss.

Strangely, on TinkerOS and Ubuntu OS for Tinkerboard, all of which run
Kernel 4.4, I do not get sample loss with the Osmocom drivers and the
zerocopy code enabled.

I'm also running the Osmocom drivers on an Odroid XU4 with Ubuntu which is
also running Kernel 4.14, and on Raspbian, and on those there is no sample
loss. So it seems to be something specific to the Tinkerboard and Armbian
with Kernel 4.14y.

Not sure if the zerocopy code is just not getting activated on those other
OSes or what. How do I check if the installed libusb API version is >=
0x01000105?

Any ideas what could cause the zero copy code to result in the lost samples?

Regards,
Carl Laufer
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