Re: Underruns causing USRP to stop transmitting and receiving

Hi Jerrid,

thanks for the answer!

Let me have a couple of comments, just quickly, in no particular order:

* If in doubt, send code as code instead of as screenshot. These
screenshots tell me very little about your software – and they don't
really show me the parts of the code I'm interested in.
  I advised some students at uni. The first thing I require them to do
is put their stuff on a git repository that I can access. That way, they
can always tell me what to look at when they have a question. I found
this is also a crucial technique for development outside of an academic
setting!

* A function probe is really a kludge in GNU Radio and probably
shouldn't be used. You've got very many of these – and that kind of
hints at architectural problems, e.g. you trying to replace message
passing with polling. My wild guess is that you've found a tutorial that
advertises the function probe. Really, that's not meant for signal
processing / marshalling purposes.

* Yeah, don't do time-critical signal processing in Python. As (the
other) Marcus mentioned, Python in this usage is orders of magnitude
slower than just writing this in C++.

So, recommendations:

1. Get rid of **all** the function probes. It's not clear why you'd want
that - really, it seems to me that you want to emit a new channel power
estimate e.g. every 10000 samples. That should be a very normal
decimating block!
2. In case you don't want to produce output regularly, you'd go with
message passing, or with tagging the estimate to a sample on your
estimator's output stream whenever appropriate (e.g. after receiving a
message "please estimate this and that now"). Tagging would allow you to
actually know which sample an estimate belongs to.
3. Python -> C++ if still necessary (quite possible)


Best regards,
Marcus

On 21.10.20 20:58, Jerrid Plymale wrote:
> Marcus,
>
> We are analyzing the average channel power of the USRP, as well as checking to see if the signal received is a constant envelope signal, and a handful of other functions like narrowband detection and pulsed signal detection. Here is a screenshot of the flowgraph:
>
> [A picture containing graphical user interface Description automatically generated]
>
> And here is a snippet of the average channel power estimator function (disregard the function name as that needs to be changed):
>
> [Text Description automatically generated]
>
> So when this function is executed inside the work function of an embedded python block, the application underruns, spitting out U's into the terminal window. If instead we execute the function outside of the work function, as shown below, the application doesn't underrun.
>
> [Text Description automatically generated]
>
> And so the function being used above to execute the average channel power estimator is being polled at a 10 Hz rate by a function probe. So are the underruns due to polling rate difference between the work function and the function probe? Is it something else? Any ideas on how I can get to work in the work function without underrunning?
>
> Best Regards,
>
> Jerrid
>