I have a flowgraph I am running on an E310 using all stock RFNoC blocks. It
looks a lot like this:
RFNoC:Radio ---> RFNoC: Split Stream ---> RFNoC: FFT ---> RFNoC: Keep 1 in N
---> RFNoC: Log Power ----> GR: complex to float ---> GR:Raster Sink
|
|
--->
RFNOC: Keep 1 in N ---> GR: log Power FFT ---> GR: custom block ---> GR: Raster
sink
So no DDC in the flowgraph. If I run the master_clock_rate at 56MHz, the
sample rate should be the same (I have SPP=512, and that is the size of the FFT
as well). I would then think that the pair of Keep 1 in Ns should basically
divide down the rate by N. So if I have them set to 56e3, that means I should
get a sample rate that averages out to be 1KHz out each of the two streams to
host for a total of 2KHz. I know that the E310 can stream 10MHz no problem to
the ARM, so I am not sure why in this scenario I get a ton of:
Ooverrun on chan 0
Ooverrun on chan 0
Ooverrun on chan 0
Ooverrun on chan 0
Ooverrun on chan 0
Ooverrun on chan 0
Ooverrun on chan 0
Now why would that be? I have no idea.
I set my downstream sample rate (on the GR host) to be sample_rate/keep1inN.
I bring this up because in the case about sample_rate is the same as
master_clock_rate. If I reduce the sample_rate to be 40MHz (which gets ignored
by the E310 since I don't have a DDC, but gets used in the down stream sample
rate for the raster guis, I can set the keep1inN up to the max of 65535 and
there are no overflows. There are "timeout on chan 0" errors, but I think that
is because RFNoC must be timing out somewhere du to the throughput being so
slow.
Does this make sense? Does anyone have an idea what I am doing stupidly
wrong? I have a feeling I am violating timing somewhere, but I can't figure
out where....
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