fl2k on rpi4: no more USB error

Carl-Fredrik Enell fredrik at kyla.kiruna.se
Fri May 22 19:40:37 UTC 2020

Dear all,

I found that the fix for the USB issue on ARM systems has finally made
it into the Linux kernel, 5.6.14 and 5.7-rc6. Today I installed the
latest Manjaro 64 unstable mainline kernel on my rpi4 and made some
quick tests with fl-wspr (https://github.com/tejeez/fl2k-tool).

There are no more USB errors*, but I still get underflow errors at high
sample rates. In my quick tests the maximum reliable sample rate was about
20 MHz when running in an X session with other programs. When I
stopped the X server and ran in a text console I could go above 30 MHz
without underflows.
This means that the rpi4 is fine as an SDR transceiver for many
purposes- but it would be nice to know if it is possible to tune the
system for a bit higher sample rates!

All the best
SM2YHP Fredrik

* Installed AUR package libosmo-fl2k-git to fix other USB
device issues 
Carl-Fredrik Enell
Föraregatan 26B
SE-98139 Kiruna


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