OSParam Error

I am running a USRP source through a throttle to an FFT sink and a file
sink. Last time I ran it, I got an “OSParam error”, followed by a bunch
"D"s and the FFT was lagging and jumping. Any ideas as to what this is?
sample rate is 50M.

Paul B. Huter

[email protected]
Discuss-gnuradio Info Page
You only ever need a “throttle” when you don’t have hardware in the
flow-graph pacing things.

AT 50Msps, whatever your flow-graph is doing will be working really,

As always, thank you, Marcus.

I am thinking about getting rid of the graph (and throttle, now), and
making another setup to run the output file from the original (through a
throttle?) to the graph to look at smaller pieces. I want to be able to
look at (say) 5MHz-10MHz, so my plan is to set the FFT to be 5MHz
on 7.5MHz. However, I am not sure if that is correct. But - first step
to get my data.

Thanks, again, Marcus.

Paul B. Huter

Don’t use a throttle in a flow graph with a hardware source. A throttle
block is software-limiting the number of samples that pass your
flowgraph on average in a given time. You have an USRP that produces
samples at a constant rate: Either this rate is significantly lower than
your throttle rate, in which case throttle is superflous, or you’ll run
into problems because throttle is trying to throttle what it shouldn’t
throttle because the hardware defines how fast your samples must flow.

For your file-sourced flowgraph, however, throttle is the right way to
go – but honestly, with 50Ms/s your PC will most likely get into such
heavy work that it can’t process everything in real-time (otherwise it
could do it with live data, too) and your throttle doesn’t do anything.

I don’t know your osparam error. But the D errors are likely caused by
your computer being to busy to process the samples.
Reduce the sample rate at the usrp, if you want to look at 10MHz of
bandwidth, anyway.