[Discuss-gnuradio] UHD recv demuxer errors with a simple Python flowgraph

[Pierre Baudry]

Hi,

While working with gr-gsm blocks and examples I ran into some weird UHD
errors.

I tried to reduce as much as possible the flowgraph complexity, and
ended up writing a very simple flowgraph that seems to reliably trigger
the UHD errors.

I uploaded the flowgraph here:
https://gist.github.com/anonymous/d3c0c9f1f72ab7cdc2c3460126682bc6

The point of this flowgraph is to simply tune into a frequency, acquire
some samples and proceed with a new acquisition. This is similar to what
grgsm-scanner does, with the sample analysis removed.

On my hardware (Xeon E5-2650 with USRP B200 on USB3), this flowgraph
will produce a lot of UHD errors every time such as:

> Tuning to 1934.301035 MHz
> Acquisition N° 13 finished
> 
> Tuning to 1619.216092 MHz
> 
> UHD Error:
>     recv packet demuxer unexpected sid 0xc449c000
> 
> UHD Error:
>     recv packet demuxer unexpected sid 0x44208000
> 
> UHD Error:
>     recv packet demuxer unexpected sid 0xc4064000
> 
> UHD Error:
>     recv packet demuxer unexpected sid 0xc2780000
> ---- snip ----

Am I doing something the wrong way ?
Is there a limitation of some kind with the way I retune the USRP ?
I first thought that these errors were tied to the processing power
required but the flowgraph I wrote just trashes received samples so this
is very unlikely.

Best,
Pierre