Re: Osmo-FL2K stops transmitting randomly - osmocom-sdr

16 Jun 2018

Hi Marcus and thanks for your reply.

...
 Your video is about 13 minutes longer than I'd like
– can you pinpoint
at which time in that video your transmission stops? 
You can watch this video between 7:00 & 8:00 to observe the breakdowns.

...
 As usual, debugging on the side of the observing party
might very well
be helpful here. Figure out whether the program halts (a software
debugger, e.g. gdb, would be the appropriate tool), the USB transfers
stop (wireshark might be helpful here), or whether just something
happens inside the device while the computer and software happily
continue to work. Observing the spectrum might help. 
You just gave me a good point to start debugging this issue! Actually I don’t have a
RTL-SDR or anything else in hand right now to observe the spectrum but I will do the tests
soon.
--------------------------------------------

Hi Steve, did a great job!

...
 This will happen if the host cannot supply enough data
to the device,
you need to use a lower sample rate in this case, or get rid of
a hypervisor like VMware, as is the case in this video. 
I tried fl2k_fm both in VMWare and in GNU radio live image booted from a flash drive and
in both I had the problem. and why should I use a lower sample rate when my system can
handle the samples well? (take a look at attachments)

I’m using VMWare Workstation Pro (Version: 14.1.2 build-8497320) on a brand new ACER
laptop (Model: Aspire A715-71G-71Y3) running Windows 10 Pro 1803 (Build: 17134.112) with
16 gigabyte RAM and an Intel Core i7 7700HQ CPU. The USB host controller is Intel(R) USB
3.0 eXtensible Host Controller - 1.0 (Microsoft) witch I believe it can handle up to 157
MS/s. all drivers are updated. 
However, I didn’t see anything wrong with virtualization except that the maximum
achievable sample rate was a little lower than the GNU radio live booted from flash drive.
Except for this, I didn't encounter by anything.

...
 There seems to be a 'frame loss' mechanism to
detect this in  through an
interrupt transfer, but I haven't implemented this yet and have no idea
if this works with disabled synchronization. 
Looking forward to the results!
And don’t mind asking me for a helping hand. I’ll do my best to help this project.

I was reading the comments below this post in rtl-sdr.com blog and I saw a user who had
the same issue mentioned something that might be useful:
Of futher note (hopefully someone from osmocom will see this) the bug where the broadcast
intermittently ceases in fl2k_fm under both an ubuntu virtual machine and directly ran as
a windows exe seems to have something to do with cpu affinity and / or process priority –
generally it starts spitting out the underflow message on stdout then the signal drops out
and the process requires a restart.
Regards,
Sajjad